response.rs - webauthn_rp | Philomathic Life

response.rs (85857B)
      1 extern crate alloc;
      2 #[cfg(test)]
      3 mod tests;
      4 use crate::{
      5     request::{register::{PublicKeyCredentialUserEntity, UserHandle}, Challenge, RpId, Url},
      6     response::{
      7         auth::error::{
      8             AuthCeremonyErr, AuthenticatorDataErr as AuthAuthDataErr,
      9             AuthenticatorExtensionOutputErr as AuthAuthExtErr,
     10         },
     11         error::{CollectedClientDataErr, CredentialIdErr},
     12         register::error::{AttestationObjectErr, AttestedCredentialDataErr, AuthenticatorDataErr as RegAuthDataErr, AuthenticatorExtensionOutputErr as RegAuthExtErr, PubKeyErr, RegCeremonyErr},
     13     },
     14 };
     15 use alloc::borrow::Cow;
     16 use core::{
     17     borrow::Borrow,
     18     cmp::Ordering,
     19     convert::Infallible,
     20     fmt::{self, Display, Formatter},
     21     hash::{Hash, Hasher},
     22     str,
     23 };
     24 use rsa::sha2::{digest::OutputSizeUser as _, Sha256};
     25 #[cfg(feature = "serde_relaxed")]
     26 use ser_relaxed::SerdeJsonErr;
     27 /// Contains functionality for completing the
     28 /// [authentication ceremony](https://www.w3.org/TR/webauthn-3/#authentication-ceremony).
     29 ///
     30 /// # Examples
     31 ///
     32 /// ```no_run
     33 /// # use core::convert;
     34 /// # use webauthn_rp::{
     35 /// #     hash::hash_set::{InsertRemoveExpired, MaxLenHashSet},
     36 /// #     request::{auth::{error::InvalidTimeout, DiscoverableAuthenticationClientState, DiscoverableCredentialRequestOptions, AuthenticationVerificationOptions}, register::{UserHandle, USER_HANDLE_MAX_LEN, UserHandle64}, BackupReq, RpId},
     37 /// #     response::{auth::{error::AuthCeremonyErr, DiscoverableAuthentication64}, error::CollectedClientDataErr, register::{AuthenticatorExtensionOutputStaticState, ClientExtensionsOutputsStaticState, CredentialProtectionPolicy, DynamicState, Ed25519PubKey, CompressedPubKeyOwned, StaticState}, AuthenticatorAttachment, Backup, CollectedClientData, CredentialId},
     38 /// #     AuthenticatedCredential, CredentialErr
     39 /// # };
     40 /// # #[derive(Debug)]
     41 /// # enum E {
     42 /// #     CollectedClientData(CollectedClientDataErr),
     43 /// #     InvalidTimeout(InvalidTimeout),
     44 /// #     SerdeJson(serde_json::Error),
     45 /// #     MissingUserHandle,
     46 /// #     MissingCeremony,
     47 /// #     UnknownCredential,
     48 /// #     Credential(CredentialErr),
     49 /// #     AuthCeremony(AuthCeremonyErr),
     50 /// # }
     51 /// # impl From<CollectedClientDataErr> for E {
     52 /// #     fn from(value: CollectedClientDataErr) -> Self {
     53 /// #         Self::CollectedClientData(value)
     54 /// #     }
     55 /// # }
     56 /// # impl From<InvalidTimeout> for E {
     57 /// #     fn from(value: InvalidTimeout) -> Self {
     58 /// #         Self::InvalidTimeout(value)
     59 /// #     }
     60 /// # }
     61 /// # impl From<serde_json::Error> for E {
     62 /// #     fn from(value: serde_json::Error) -> Self {
     63 /// #         Self::SerdeJson(value)
     64 /// #     }
     65 /// # }
     66 /// # impl From<CredentialErr> for E {
     67 /// #     fn from(value: CredentialErr) -> Self {
     68 /// #         Self::Credential(value)
     69 /// #     }
     70 /// # }
     71 /// # impl From<AuthCeremonyErr> for E {
     72 /// #     fn from(value: AuthCeremonyErr) -> Self {
     73 /// #         Self::AuthCeremony(value)
     74 /// #     }
     75 /// # }
     76 /// const RP_ID: &RpId = &RpId::from_static_domain("example.com").unwrap();
     77 /// let mut ceremonies = MaxLenHashSet::new(128);
     78 /// let (server, client) = DiscoverableCredentialRequestOptions::passkey(RP_ID).start_ceremony()?;
     79 /// assert_eq!(ceremonies.insert_remove_all_expired(server), InsertRemoveExpired::Success);
     80 /// # #[cfg(feature = "serde")]
     81 /// let authentication = serde_json::from_str::<DiscoverableAuthentication64>(get_authentication_json(client).as_str())?;
     82 /// # #[cfg(feature = "serde")]
     83 /// let user_handle = authentication.response().user_handle();
     84 /// # #[cfg(feature = "serde")]
     85 /// let (static_state, dynamic_state) = get_credential(authentication.raw_id(), &user_handle).ok_or(E::UnknownCredential)?;
     86 /// # #[cfg(all(feature = "custom", feature = "serde"))]
     87 /// let mut cred = AuthenticatedCredential::new(authentication.raw_id(), &user_handle, static_state, dynamic_state)?;
     88 /// # #[cfg(all(feature = "custom", feature = "serde"))]
     89 /// if ceremonies.take(&authentication.challenge()?).ok_or(E::MissingCeremony)?.verify(RP_ID, &authentication, &mut cred, &AuthenticationVerificationOptions::<&str, &str>::default())? {
     90 ///     update_cred(authentication.raw_id(), cred.dynamic_state());
     91 /// }
     92 /// /// Send `DiscoverableAuthenticationClientState` and receive `DiscoverableAuthentication64` JSON from client.
     93 /// # #[cfg(feature = "serde")]
     94 /// fn get_authentication_json(client: DiscoverableAuthenticationClientState<'_, '_, '_>) -> String {
     95 ///     // ⋮
     96 /// #     let client_data_json = base64url_nopad::encode(serde_json::json!({
     97 /// #         "type": "webauthn.get",
     98 /// #         "challenge": client.options().public_key.challenge,
     99 /// #         "origin": format!("https://{}", client.options().public_key.rp_id.as_ref()),
    100 /// #         "crossOrigin": false
    101 /// #     }).to_string().as_bytes());
    102 /// #     serde_json::json!({
    103 /// #         "id": "AAAAAAAAAAAAAAAAAAAAAA",
    104 /// #         "rawId": "AAAAAAAAAAAAAAAAAAAAAA",
    105 /// #         "response": {
    106 /// #             "clientDataJSON": client_data_json,
    107 /// #             "authenticatorData": "",
    108 /// #             "signature": "",
    109 /// #             "userHandle": "AA"
    110 /// #         },
    111 /// #         "clientExtensionResults": {},
    112 /// #         "type": "public-key"
    113 /// #     }).to_string()
    114 /// }
    115 /// /// Gets the `AuthenticatedCredential` parts associated with `id` and `user_handle` from the database.
    116 /// fn get_credential(id: CredentialId<&[u8]>, user_handle: &UserHandle64) -> Option<(StaticState<CompressedPubKeyOwned>, DynamicState)> {
    117 ///     // ⋮
    118 /// #     Some((StaticState { credential_public_key: CompressedPubKeyOwned::Ed25519(Ed25519PubKey::from([0; 32])), extensions: AuthenticatorExtensionOutputStaticState { cred_protect: CredentialProtectionPolicy::UserVerificationRequired, hmac_secret: None, }, client_extension_results: ClientExtensionsOutputsStaticState { prf: None, }, }, DynamicState { user_verified: true, backup: Backup::NotEligible, sign_count: 1, authenticator_attachment: AuthenticatorAttachment::None }))
    119 /// }
    120 /// /// Updates the current `DynamicState` associated with `id` in the database to
    121 /// /// `dyn_state`.
    122 /// fn update_cred(id: CredentialId<&[u8]>, dyn_state: DynamicState) {
    123 ///     // ⋮
    124 /// }
    125 /// # Ok::<_, E>(())
    126 /// ```
    127 pub mod auth;
    128 /// Contains functionality to (de)serialize data to a data store.
    129 #[cfg(feature = "bin")]
    130 pub mod bin;
    131 /// Contains constants useful for
    132 /// [CTAP2 canonical CBOR encoding form](https://fidoalliance.org/specs/fido-v2.2-rd-20230321/fido-client-to-authenticator-protocol-v2.2-rd-20230321.html#ctap2-canonical-cbor-encoding-form).
    133 mod cbor;
    134 /// Contains functionality that needs to be accessible when `bin` or `serde` are not enabled.
    135 #[cfg(feature = "custom")]
    136 pub mod custom;
    137 /// Contains error types.
    138 pub mod error;
    139 /// Contains functionality for completing the
    140 /// [registration ceremony](https://www.w3.org/TR/webauthn-3/#registration-ceremony).
    141 ///
    142 /// # Examples
    143 ///
    144 /// ```no_run
    145 /// # use core::convert;
    146 /// # use webauthn_rp::{
    147 /// #     hash::hash_set::{InsertRemoveExpired, MaxLenHashSet},
    148 /// #     request::{register::{error::CreationOptionsErr, CredentialCreationOptions, PublicKeyCredentialUserEntity, RegistrationClientState, UserHandle, UserHandle64, USER_HANDLE_MAX_LEN, RegistrationVerificationOptions}, PublicKeyCredentialDescriptor, RpId},
    149 /// #     response::{register::{error::RegCeremonyErr, Registration}, error::CollectedClientDataErr, CollectedClientData},
    150 /// #     RegisteredCredential
    151 /// # };
    152 /// # #[derive(Debug)]
    153 /// # enum E {
    154 /// #     CollectedClientData(CollectedClientDataErr),
    155 /// #     CreationOptions(CreationOptionsErr),
    156 /// #     SerdeJson(serde_json::Error),
    157 /// #     MissingCeremony,
    158 /// #     RegCeremony(RegCeremonyErr),
    159 /// # }
    160 /// # impl From<CollectedClientDataErr> for E {
    161 /// #     fn from(value: CollectedClientDataErr) -> Self {
    162 /// #         Self::CollectedClientData(value)
    163 /// #     }
    164 /// # }
    165 /// # impl From<CreationOptionsErr> for E {
    166 /// #     fn from(value: CreationOptionsErr) -> Self {
    167 /// #         Self::CreationOptions(value)
    168 /// #     }
    169 /// # }
    170 /// # impl From<serde_json::Error> for E {
    171 /// #     fn from(value: serde_json::Error) -> Self {
    172 /// #         Self::SerdeJson(value)
    173 /// #     }
    174 /// # }
    175 /// # impl From<RegCeremonyErr> for E {
    176 /// #     fn from(value: RegCeremonyErr) -> Self {
    177 /// #         Self::RegCeremony(value)
    178 /// #     }
    179 /// # }
    180 /// const RP_ID: &RpId = &RpId::from_static_domain("example.com").unwrap();
    181 /// # #[cfg(feature = "custom")]
    182 /// let mut ceremonies = MaxLenHashSet::new(128);
    183 /// # #[cfg(feature = "custom")]
    184 /// let user_handle = get_user_handle();
    185 /// # #[cfg(feature = "custom")]
    186 /// let user = get_user_entity(&user_handle);
    187 /// # #[cfg(feature = "custom")]
    188 /// let creds = get_registered_credentials(user_handle);
    189 /// # #[cfg(feature = "custom")]
    190 /// let (server, client) = CredentialCreationOptions::passkey(RP_ID, user, creds).start_ceremony()?;
    191 /// # #[cfg(feature = "custom")]
    192 /// assert_eq!(ceremonies.insert_remove_all_expired(server), InsertRemoveExpired::Success);
    193 /// # #[cfg(all(feature = "serde_relaxed", feature = "custom"))]
    194 /// let registration = serde_json::from_str::<Registration>(get_registration_json(client).as_str())?;
    195 /// let ver_opts = RegistrationVerificationOptions::<&str, &str>::default();
    196 /// # #[cfg(all(feature = "custom", feature = "serde_relaxed"))]
    197 /// insert_cred(ceremonies.take(&registration.challenge()?).ok_or(E::MissingCeremony)?.verify(RP_ID, &registration, &ver_opts)?);
    198 /// /// Extract `UserHandle` from session cookie if this is not the first credential registered.
    199 /// # #[cfg(feature = "custom")]
    200 /// fn get_user_handle() -> UserHandle64 {
    201 ///     // ⋮
    202 /// #     [0; USER_HANDLE_MAX_LEN].into()
    203 /// }
    204 /// /// Fetch `PublicKeyCredentialUserEntity` info associated with `user`.
    205 /// ///
    206 /// /// If this is the first time a credential is being registered, then `PublicKeyCredentialUserEntity`
    207 /// /// will need to be constructed with `name` and `display_name` passed from the client and `UserHandle::new`
    208 /// /// used for `id`. Once created, this info can be stored such that the entity information
    209 /// /// does not need to be requested for subsequent registrations.
    210 /// # #[cfg(feature = "custom")]
    211 /// fn get_user_entity(user: &UserHandle<USER_HANDLE_MAX_LEN>) -> PublicKeyCredentialUserEntity<'_, '_, '_, USER_HANDLE_MAX_LEN> {
    212 ///     // ⋮
    213 /// #     PublicKeyCredentialUserEntity {
    214 /// #         name: "foo",
    215 /// #         id: user,
    216 /// #         display_name: "",
    217 /// #     }
    218 /// }
    219 /// /// Send `RegistrationClientState` and receive `Registration` JSON from client.
    220 /// # #[cfg(feature = "serde")]
    221 /// fn get_registration_json(client: RegistrationClientState<'_, '_, '_, '_, '_, '_, USER_HANDLE_MAX_LEN>) -> String {
    222 ///     // ⋮
    223 /// #     let client_data_json = base64url_nopad::encode(serde_json::json!({
    224 /// #         "type": "webauthn.create",
    225 /// #         "challenge": client.options().public_key.challenge,
    226 /// #         "origin": format!("https://{}", client.options().public_key.rp_id.as_ref()),
    227 /// #         "crossOrigin": false
    228 /// #     }).to_string().as_bytes());
    229 /// #     serde_json::json!({
    230 /// #         "response": {
    231 /// #             "clientDataJSON": client_data_json,
    232 /// #             "attestationObject": ""
    233 /// #         }
    234 /// #     }).to_string()
    235 /// }
    236 /// /// Fetch the `PublicKeyCredentialDescriptor`s associated with `user`.
    237 /// ///
    238 /// /// This doesn't need to be called when this is the first credential registered for `user`; instead
    239 /// /// an empty `Vec` should be passed.
    240 /// fn get_registered_credentials(
    241 ///     user: UserHandle<USER_HANDLE_MAX_LEN>,
    242 /// ) -> Vec<PublicKeyCredentialDescriptor<Box<[u8]>>> {
    243 ///     // ⋮
    244 /// #     Vec::new()
    245 /// }
    246 /// /// Inserts `RegisteredCredential::into_parts` into the database.
    247 /// fn insert_cred(cred: RegisteredCredential<'_, USER_HANDLE_MAX_LEN>) {
    248 ///     // ⋮
    249 /// }
    250 /// # Ok::<_, E>(())
    251 /// ```
    252 pub mod register;
    253 /// Contains functionality to (de)serialize data to/from a client.
    254 #[cfg(feature = "serde")]
    255 pub(crate) mod ser;
    256 /// Contains functionality to deserialize data from a client in a "relaxed" way.
    257 #[cfg(feature = "serde_relaxed")]
    258 pub mod ser_relaxed;
    259 /// [Backup eligibility](https://www.w3.org/TR/webauthn-3/#backup-eligibility) and
    260 /// [backup state](https://www.w3.org/TR/webauthn-3/#backup-state).
    261 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
    262 pub enum Backup {
    263     /// [BE and BS](https://www.w3.org/TR/webauthn-3/#authdata-flags) flags are `0`.
    264     NotEligible,
    265     /// [BE and BS](https://www.w3.org/TR/webauthn-3/#authdata-flags) flags are `1` and `0` respectively.
    266     Eligible,
    267     /// [BE and BS](https://www.w3.org/TR/webauthn-3/#authdata-flags) flags are `1`.
    268     Exists,
    269 }
    270 impl PartialEq<&Self> for Backup {
    271     #[inline]
    272     fn eq(&self, other: &&Self) -> bool {
    273         *self == **other
    274     }
    275 }
    276 impl PartialEq<Backup> for &Backup {
    277     #[inline]
    278     fn eq(&self, other: &Backup) -> bool {
    279         **self == *other
    280     }
    281 }
    282 /// [`AuthenticatorTransport`](https://www.w3.org/TR/webauthn-3/#enumdef-authenticatortransport).
    283 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
    284 pub enum AuthenticatorTransport {
    285     /// [`ble`](https://www.w3.org/TR/webauthn-3/#dom-authenticatortransport-ble).
    286     Ble,
    287     /// [`hybrid`](https://www.w3.org/TR/webauthn-3/#dom-authenticatortransport-hybrid).
    288     Hybrid,
    289     /// [`internal`](https://www.w3.org/TR/webauthn-3/#dom-authenticatortransport-internal).
    290     Internal,
    291     /// [`nfc`](https://www.w3.org/TR/webauthn-3/#dom-authenticatortransport-nfc).
    292     Nfc,
    293     /// [`smart-card`](https://www.w3.org/TR/webauthn-3/#dom-authenticatortransport-smart-card).
    294     SmartCard,
    295     /// [`usb`](https://www.w3.org/TR/webauthn-3/#dom-authenticatortransport-usb).
    296     Usb,
    297 }
    298 impl AuthenticatorTransport {
    299     /// Returns the encoded [`u8`] that `self` represents.
    300     const fn to_u8(self) -> u8 {
    301         match self {
    302             Self::Ble => 0x1,
    303             Self::Hybrid => 0x2,
    304             Self::Internal => 0x4,
    305             Self::Nfc => 0x8,
    306             Self::SmartCard => 0x10,
    307             Self::Usb => 0x20,
    308         }
    309     }
    310 }
    311 /// Set of [`AuthenticatorTransport`]s.
    312 #[derive(Clone, Copy, Debug)]
    313 pub struct AuthTransports(u8);
    314 impl AuthTransports {
    315     /// An empty `AuthTransports`.
    316     #[cfg(feature = "custom")]
    317     pub const NONE: Self = Self::new();
    318     /// An `AuthTransports` containing all possible [`AuthenticatorTransport`]s.
    319     #[cfg(feature = "custom")]
    320     pub const ALL: Self = Self::all();
    321     /// Construct an empty `AuthTransports`.
    322     #[cfg(any(feature = "bin", feature = "custom", feature = "serde"))]
    323     pub(super) const fn new() -> Self {
    324         Self(0)
    325     }
    326     #[cfg(any(feature = "bin", feature = "custom"))]
    327     /// Construct an `AuthTransports` containing all `AuthenticatorTransport`s.
    328     const fn all() -> Self {
    329         Self::new()
    330             .add_transport(AuthenticatorTransport::Ble)
    331             .add_transport(AuthenticatorTransport::Hybrid)
    332             .add_transport(AuthenticatorTransport::Internal)
    333             .add_transport(AuthenticatorTransport::Nfc)
    334             .add_transport(AuthenticatorTransport::SmartCard)
    335             .add_transport(AuthenticatorTransport::Usb)
    336     }
    337     /// Returns the number of [`AuthenticatorTransport`]s in `self`.
    338     ///
    339     /// # Examples
    340     ///
    341     /// ```
    342     /// # use webauthn_rp::response::AuthTransports;
    343     /// # #[cfg(feature = "custom")]
    344     /// assert_eq!(AuthTransports::ALL.count(), 6);
    345     /// ```
    346     #[inline]
    347     #[must_use]
    348     pub const fn count(self) -> u32 {
    349         self.0.count_ones()
    350     }
    351     /// Returns `true` iff there are no [`AuthenticatorTransport`]s in `self`.
    352     ///
    353     /// # Examples
    354     ///
    355     /// ```
    356     /// # use webauthn_rp::response::AuthTransports;
    357     /// # #[cfg(feature = "custom")]
    358     /// assert!(AuthTransports::NONE.is_empty());
    359     /// ```
    360     #[inline]
    361     #[must_use]
    362     pub const fn is_empty(self) -> bool {
    363         self.0 == 0
    364     }
    365     /// Returns `true` iff `self` contains `transport`.
    366     ///
    367     /// # Examples
    368     ///
    369     /// ```
    370     /// # use webauthn_rp::response::{AuthTransports, AuthenticatorTransport};
    371     /// # #[cfg(feature = "custom")]
    372     /// assert!(AuthTransports::ALL.contains(AuthenticatorTransport::Ble));
    373     /// ```
    374     #[inline]
    375     #[must_use]
    376     pub const fn contains(self, transport: AuthenticatorTransport) -> bool {
    377         let val = transport.to_u8();
    378         self.0 & val == val
    379     }
    380     /// Returns a copy of `self` with `transport` added.
    381     ///
    382     /// `self` is returned iff `transport` already exists.
    383     #[cfg(any(feature = "bin", feature = "custom", feature = "serde"))]
    384     const fn add_transport(self, transport: AuthenticatorTransport) -> Self {
    385         Self(self.0 | transport.to_u8())
    386     }
    387     /// Returns a copy of `self` with `transport` added.
    388     ///
    389     /// `self` is returned iff `transport` already exists.
    390     ///
    391     /// # Examples
    392     ///
    393     /// ```
    394     /// # use webauthn_rp::response::{AuthTransports, AuthenticatorTransport};
    395     /// assert_eq!(
    396     ///     AuthTransports::NONE
    397     ///         .add(AuthenticatorTransport::Usb)
    398     ///         .count(),
    399     ///     1
    400     /// );
    401     /// assert_eq!(
    402     ///     AuthTransports::ALL.add(AuthenticatorTransport::Usb).count(),
    403     ///     6
    404     /// );
    405     /// ```
    406     #[cfg(feature = "custom")]
    407     #[inline]
    408     #[must_use]
    409     pub const fn add(self, transport: AuthenticatorTransport) -> Self {
    410         self.add_transport(transport)
    411     }
    412     /// Returns a copy of `self` with `transport` removed.
    413     ///
    414     /// `self` is returned iff `transport` did not exist.
    415     ///
    416     /// # Examples
    417     ///
    418     /// ```
    419     /// # use webauthn_rp::response::{AuthTransports, AuthenticatorTransport};
    420     /// assert_eq!(
    421     ///     AuthTransports::ALL
    422     ///         .remove(AuthenticatorTransport::Internal)
    423     ///         .count(),
    424     ///     5
    425     /// );
    426     /// assert_eq!(
    427     ///     AuthTransports::NONE.remove(AuthenticatorTransport::Usb).count(),
    428     ///     0
    429     /// );
    430     /// ```
    431     #[cfg(feature = "custom")]
    432     #[inline]
    433     #[must_use]
    434     pub const fn remove(self, transport: AuthenticatorTransport) -> Self {
    435         Self(self.0 & !transport.to_u8())
    436     }
    437 }
    438 /// [`AuthenticatorAttachment`](https://www.w3.org/TR/webauthn-3/#enumdef-authenticatorattachment).
    439 #[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
    440 pub enum AuthenticatorAttachment {
    441     /// No attachment information.
    442     #[default]
    443     None,
    444     /// [`platform`](https://www.w3.org/TR/webauthn-3/#dom-authenticatorattachment-platform).
    445     Platform,
    446     /// [`cross-platform`](https://www.w3.org/TR/webauthn-3/#dom-authenticatorattachment-cross-platform).
    447     CrossPlatform,
    448 }
    449 impl PartialEq<&Self> for AuthenticatorAttachment {
    450     #[inline]
    451     fn eq(&self, other: &&Self) -> bool {
    452         *self == **other
    453     }
    454 }
    455 impl PartialEq<AuthenticatorAttachment> for &AuthenticatorAttachment {
    456     #[inline]
    457     fn eq(&self, other: &AuthenticatorAttachment) -> bool {
    458         **self == *other
    459     }
    460 }
    461 /// The maximum number of bytes that can make up a Credential ID
    462 /// [per WebAuthn](https://www.w3.org/TR/webauthn-3/#credential-id).
    463 pub const CRED_ID_MAX_LEN: usize = 1023;
    464 /// The minimum number of bytes that can make up a Credential ID
    465 /// [per WebAuthn](https://www.w3.org/TR/webauthn-3/#credential-id).
    466 ///
    467 /// The spec does not call out this value directly instead it states the following:
    468 ///
    469 /// > Credential IDs are generated by authenticators in two forms:
    470 /// >
    471 /// > * At least 16 bytes that include at least 100 bits of entropy, or
    472 /// > * The [public key credential source](https://www.w3.org/TR/webauthn-3/#public-key-credential-source),
    473 /// >   without its Credential ID or mutable items, encrypted so only its managing
    474 /// >   authenticator can decrypt it. This form allows the authenticator to be nearly
    475 /// >   stateless, by having the Relying Party store any necessary state.
    476 ///
    477 /// One of the immutable items of the public key credential source is the private key
    478 /// which for any real-world signature algorithm will always be at least 16 bytes.
    479 pub const CRED_ID_MIN_LEN: usize = 16;
    480 /// A [Credential ID](https://www.w3.org/TR/webauthn-3/#credential-id) that is made up of
    481 /// [`CRED_ID_MIN_LEN`]–[`CRED_ID_MAX_LEN`] bytes.
    482 #[derive(Clone, Copy, Debug)]
    483 pub struct CredentialId<T>(T);
    484 impl<T> CredentialId<T> {
    485     /// Returns the contained data consuming `self`.
    486     #[inline]
    487     pub fn into_inner(self) -> T {
    488         self.0
    489     }
    490     /// Returns the contained data.
    491     #[inline]
    492     pub const fn inner(&self) -> &T {
    493         &self.0
    494     }
    495 }
    496 impl<'a> CredentialId<&'a [u8]> {
    497     /// Creates a `CredentialId` from a `slice`.
    498     #[expect(single_use_lifetimes, reason = "false positive")]
    499     fn from_slice<'b: 'a>(value: &'b [u8]) -> Result<Self, CredentialIdErr> {
    500         if (CRED_ID_MIN_LEN..=CRED_ID_MAX_LEN).contains(&value.len()) {
    501             Ok(Self(value))
    502         } else {
    503             Err(CredentialIdErr)
    504         }
    505     }
    506 }
    507 impl<T: AsRef<[u8]>> AsRef<[u8]> for CredentialId<T> {
    508     #[inline]
    509     fn as_ref(&self) -> &[u8] {
    510         self.0.as_ref()
    511     }
    512 }
    513 impl<T: Borrow<[u8]>> Borrow<[u8]> for CredentialId<T> {
    514     #[inline]
    515     fn borrow(&self) -> &[u8] {
    516         self.0.borrow()
    517     }
    518 }
    519 impl<'a: 'b, 'b> From<&'a CredentialId<Box<[u8]>>> for CredentialId<&'b Box<[u8]>> {
    520     #[inline]
    521     fn from(value: &'a CredentialId<Box<[u8]>>) -> Self {
    522         Self(&value.0)
    523     }
    524 }
    525 impl<'a: 'b, 'b> From<CredentialId<&'a Box<[u8]>>> for CredentialId<&'b [u8]> {
    526     #[inline]
    527     fn from(value: CredentialId<&'a Box<[u8]>>) -> Self {
    528         Self(value.0)
    529     }
    530 }
    531 impl<'a: 'b, 'b> From<&'a CredentialId<Box<[u8]>>> for CredentialId<&'b [u8]> {
    532     #[inline]
    533     fn from(value: &'a CredentialId<Box<[u8]>>) -> Self {
    534         Self(&value.0)
    535     }
    536 }
    537 impl From<CredentialId<&[u8]>> for CredentialId<Box<[u8]>> {
    538     #[inline]
    539     fn from(value: CredentialId<&[u8]>) -> Self {
    540         Self(value.0.into())
    541     }
    542 }
    543 impl<T: PartialEq<T2>, T2: PartialEq<T>> PartialEq<CredentialId<T>> for CredentialId<T2> {
    544     #[inline]
    545     fn eq(&self, other: &CredentialId<T>) -> bool {
    546         self.0 == other.0
    547     }
    548 }
    549 impl<T: PartialEq<T2>, T2: PartialEq<T>> PartialEq<CredentialId<T>> for &CredentialId<T2> {
    550     #[inline]
    551     fn eq(&self, other: &CredentialId<T>) -> bool {
    552         **self == *other
    553     }
    554 }
    555 impl<T: PartialEq<T2>, T2: PartialEq<T>> PartialEq<&CredentialId<T>> for CredentialId<T2> {
    556     #[inline]
    557     fn eq(&self, other: &&CredentialId<T>) -> bool {
    558         *self == **other
    559     }
    560 }
    561 impl<T: Eq> Eq for CredentialId<T> {}
    562 impl<T: Hash> Hash for CredentialId<T> {
    563     #[inline]
    564     fn hash<H: Hasher>(&self, state: &mut H) {
    565         self.0.hash(state);
    566     }
    567 }
    568 impl<T: PartialOrd<T2>, T2: PartialOrd<T>> PartialOrd<CredentialId<T>> for CredentialId<T2> {
    569     #[inline]
    570     fn partial_cmp(&self, other: &CredentialId<T>) -> Option<Ordering> {
    571         self.0.partial_cmp(&other.0)
    572     }
    573 }
    574 impl<T: Ord> Ord for CredentialId<T> {
    575     #[inline]
    576     fn cmp(&self, other: &Self) -> Ordering {
    577         self.0.cmp(&other.0)
    578     }
    579 }
    580 // We define a separate type to ensure challenges sent to the client are always randomly generated;
    581 // otherwise one could deserialize arbitrary data into a `Challenge`.
    582 /// Copy of [`Challenge`] sent back from the client.
    583 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
    584 pub struct SentChallenge(pub u128);
    585 impl SentChallenge {
    586     /// Transforms `value` into a `SentChallenge` by interpreting `value` as a
    587     /// little-endian `u128`.
    588     #[expect(clippy::little_endian_bytes, reason = "Challenge and SentChallenge need to be compatible, and we need to ensure the data is sent and received in the same order")]
    589     #[inline]
    590     #[must_use]
    591     pub const fn from_array(value: [u8; 16]) -> Self {
    592         Self(u128::from_le_bytes(value))
    593     }
    594     /// Transforms `value` into a `SentChallenge`.
    595     #[inline]
    596     #[must_use]
    597     pub const fn from_challenge(value: Challenge) -> Self {
    598         Self(value.into_data())
    599     }
    600 }
    601 impl From<Challenge> for SentChallenge {
    602     #[inline]
    603     fn from(value: Challenge) -> Self {
    604         Self::from_challenge(value)
    605     }
    606 }
    607 impl From<[u8; 16]> for SentChallenge {
    608     #[inline]
    609     fn from(value: [u8; 16]) -> Self {
    610         Self::from_array(value)
    611     }
    612 }
    613 impl PartialEq<&Self> for SentChallenge {
    614     #[inline]
    615     fn eq(&self, other: &&Self) -> bool {
    616         *self == **other
    617     }
    618 }
    619 impl PartialEq<SentChallenge> for &SentChallenge {
    620     #[inline]
    621     fn eq(&self, other: &SentChallenge) -> bool {
    622         **self == *other
    623     }
    624 }
    625 impl PartialOrd for SentChallenge {
    626     #[inline]
    627     fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
    628         Some(self.cmp(other))
    629     }
    630 }
    631 impl Ord for SentChallenge {
    632     #[inline]
    633     fn cmp(&self, other: &Self) -> Ordering {
    634         self.0.cmp(&other.0)
    635     }
    636 }
    637 impl Hash for SentChallenge {
    638     #[inline]
    639     fn hash<H: Hasher>(&self, state: &mut H) {
    640         state.write_u128(self.0);
    641     }
    642 }
    643 /// An [`origin`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-origin) or
    644 /// [`topOrigin`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-toporigin).
    645 #[derive(Debug, Eq)]
    646 pub struct Origin<'a>(pub Cow<'a, str>);
    647 impl PartialEq<Origin<'_>> for Origin<'_> {
    648     #[inline]
    649     fn eq(&self, other: &Origin<'_>) -> bool {
    650         self.0 == other.0
    651     }
    652 }
    653 impl PartialEq<&Origin<'_>> for Origin<'_> {
    654     #[inline]
    655     fn eq(&self, other: &&Origin<'_>) -> bool {
    656         *self == **other
    657     }
    658 }
    659 impl PartialEq<Origin<'_>> for &Origin<'_> {
    660     #[inline]
    661     fn eq(&self, other: &Origin<'_>) -> bool {
    662         **self == *other
    663     }
    664 }
    665 impl PartialEq<str> for Origin<'_> {
    666     #[inline]
    667     fn eq(&self, other: &str) -> bool {
    668         self.0.as_ref() == other
    669     }
    670 }
    671 impl PartialEq<Origin<'_>> for str {
    672     #[inline]
    673     fn eq(&self, other: &Origin<'_>) -> bool {
    674         *other == *self
    675     }
    676 }
    677 impl PartialEq<&str> for Origin<'_> {
    678     #[inline]
    679     fn eq(&self, other: &&str) -> bool {
    680         *self == **other
    681     }
    682 }
    683 impl PartialEq<Origin<'_>> for &str {
    684     #[inline]
    685     fn eq(&self, other: &Origin<'_>) -> bool {
    686         **self == *other
    687     }
    688 }
    689 impl PartialEq<String> for Origin<'_> {
    690     #[inline]
    691     fn eq(&self, other: &String) -> bool {
    692         self.0 == *other
    693     }
    694 }
    695 impl PartialEq<Origin<'_>> for String {
    696     #[inline]
    697     fn eq(&self, other: &Origin<'_>) -> bool {
    698         *other == *self
    699     }
    700 }
    701 impl PartialEq<Url> for Origin<'_> {
    702     #[inline]
    703     fn eq(&self, other: &Url) -> bool {
    704         self.0.as_ref() == other.as_ref()
    705     }
    706 }
    707 impl PartialEq<Origin<'_>> for Url {
    708     #[inline]
    709     fn eq(&self, other: &Origin<'_>) -> bool {
    710         *other == *self
    711     }
    712 }
    713 impl PartialEq<&Url> for Origin<'_> {
    714     #[inline]
    715     fn eq(&self, other: &&Url) -> bool {
    716         *self == **other
    717     }
    718 }
    719 impl PartialEq<Origin<'_>> for &Url {
    720     #[inline]
    721     fn eq(&self, other: &Origin<'_>) -> bool {
    722         **self == *other
    723     }
    724 }
    725 /// [Authenticator data flags](https://www.w3.org/TR/webauthn-3/#authdata-flags).
    726 #[derive(Clone, Copy, Debug)]
    727 pub struct Flag {
    728     /// [`UP` flag](https://www.w3.org/TR/webauthn-3/#authdata-flags-up).
    729     ///
    730     /// Note this is always `true` when part of [`auth::AuthenticatorData::flags`].
    731     pub user_present: bool,
    732     /// [`UV` flag](https://www.w3.org/TR/webauthn-3/#concept-user-verified).
    733     pub user_verified: bool,
    734     /// [`BE`](https://www.w3.org/TR/webauthn-3/#backup-eligibility) and
    735     /// [`BS`](https://www.w3.org/TR/webauthn-3/#backup-state) flags.
    736     pub backup: Backup,
    737 }
    738 /// [Authenticator data](https://www.w3.org/TR/webauthn-3/#authenticator-data).
    739 pub(super) trait AuthData<'a>: Sized {
    740     /// Error returned by [`Self::user_is_not_present`].
    741     ///
    742     /// This should be [`Infallible`] in the event user must not always be present.
    743     type UpBitErr;
    744     /// [`attestedCredentialData`](https://www.w3.org/TR/webauthn-3/#authdata-attestedcredentialdata).
    745     type CredData;
    746     /// [`extensions`](https://www.w3.org/TR/webauthn-3/#authdata-extensions).
    747     type Ext: AuthExtOutput + Copy;
    748     /// Errors iff the user must always be present.
    749     fn user_is_not_present() -> Result<(), Self::UpBitErr>;
    750     /// `true` iff `AT` bit (i.e., bit 6) in [`Self::flag_data`] can and must be set to 1.
    751     fn contains_at_bit() -> bool;
    752     /// Constructor.
    753     fn new(rp_id_hash: &'a [u8], flags: Flag, sign_count: u32, attested_credential_data: Self::CredData, extensions: Self::Ext) -> Self;
    754     /// [`rpIdHash`](https://www.w3.org/TR/webauthn-3/#authdata-rpidhash).
    755     fn rp_hash(&self) -> &'a [u8];
    756     /// [`flags`](https://www.w3.org/TR/webauthn-3/#authdata-flags).
    757     fn flag(&self) -> Flag;
    758 }
    759 /// [`CollectedClientData`](https://www.w3.org/TR/webauthn-3/#dictdef-collectedclientdata).
    760 #[derive(Debug)]
    761 pub struct CollectedClientData<'a> {
    762     /// [`challenge`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-challenge).
    763     pub challenge: SentChallenge,
    764     /// [`origin`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-origin).
    765     pub origin: Origin<'a>,
    766     /// [`crossOrigin`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-crossorigin).
    767     pub cross_origin: bool,
    768     /// [`topOrigin`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-toporigin).
    769     ///
    770     /// When `CollectedClientData` is constructed via [`Self::from_client_data_json`], this can only be
    771     /// `Some` if [`Self::cross_origin`]; and if `Some`, it will be different than [`Self::origin`].
    772     pub top_origin: Option<Origin<'a>>,
    773 }
    774 impl<'a> CollectedClientData<'a> {
    775     /// Parses `json` based on the
    776     /// [limited verification algorithm](https://www.w3.org/TR/webauthn-3/#clientdatajson-verification).
    777     ///
    778     /// Additionally, [`topOrigin`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-toporigin) is only
    779     /// allowed to exist if it has a different value than
    780     /// [`origin`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-origin) and
    781     /// [`crossOrigin`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-crossorigin) is `true`.
    782     ///
    783     /// `REGISTRATION` iff [`type`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-type) must be
    784     /// `"webauthn.create"`; otherwise it must be `"webauthn.get"`.
    785     ///
    786     /// # Errors
    787     ///
    788     /// Errors iff `json` cannot be parsed based on the aforementioned requirements.
    789     ///
    790     /// # Examples
    791     ///
    792     /// ```
    793     /// # use webauthn_rp::response::{error::CollectedClientDataErr, CollectedClientData};
    794     /// assert!(!CollectedClientData::from_client_data_json::<true>(br#"{"type":"webauthn.create","challenge":"AAAAAAAAAAAAAAAAAAAAAA","origin":"https://example.com","crossOrigin":false}"#.as_slice())?.cross_origin);
    795     /// assert!(!CollectedClientData::from_client_data_json::<false>(br#"{"type":"webauthn.get","challenge":"AAAAAAAAAAAAAAAAAAAAAA","origin":"https://example.com","crossOrigin":false}"#.as_slice())?.cross_origin);
    796     /// # Ok::<_, CollectedClientDataErr>(())
    797     /// ```
    798     #[expect(single_use_lifetimes, reason = "false positive")]
    799     #[inline]
    800     pub fn from_client_data_json<'b: 'a, const REGISTRATION: bool>(json: &'b [u8]) -> Result<Self, CollectedClientDataErr> {
    801         LimitedVerificationParser::<REGISTRATION>::parse(json)
    802     }
    803     /// Parses `json` in a "relaxed" way.
    804     ///
    805     /// Unlike [`Self::from_client_data_json`] which requires `json` to be an output from the
    806     /// [JSON-compatible serialization of client data](https://www.w3.org/TR/webauthn-3/#clientdatajson-serialization),
    807     /// this parses `json` based entirely on the
    808     /// [`CollectedClientData`](https://www.w3.org/TR/webauthn-3/#dictdef-collectedclientdata) Web IDL `dictionary`.
    809     ///
    810     /// L1 clients predate the JSON-compatible serialization of client data; additionally there are L2 and L3
    811     /// clients that don't adhere to the JSON-compatible serialization of client data despite being required to.
    812     /// These clients serialize `CollectedClientData` so that it's valid JSON and conforms to the Web IDL `dictionary`
    813     /// and nothing more. Furthermore, when not relying on the
    814     /// [limited verification algorithm](https://www.w3.org/TR/webauthn-3/#clientdatajson-verification), the spec
    815     /// requires the data to be decoded in a way equivalent to
    816     /// [UTF-8 decode](https://encoding.spec.whatwg.org/#utf-8-decode) which both interprets a leading zero
    817     /// width no-breaking space (i.e., U+FEFF) as a byte-order mark (BOM) as well as replaces any sequences of
    818     /// invalid UTF-8 code units with the replacement character (i.e., U+FFFD). That is precisely what this
    819     /// function does.
    820     ///
    821     /// # Errors
    822     ///
    823     /// Errors iff any of the following is true:
    824     /// * The payload is not valid JSON _after_ ignoring a leading U+FEFF and replacing any sequences of invalid
    825     ///   UTF-8 code units with U+FFFD.
    826     /// * The JSON does not conform to the Web IDL `dictionary`.
    827     /// * [`type`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-type) is not `"webauthn.create"`
    828     ///   or `"webauthn.get"` when `REGISTRATION` and `!REGISTRATION` respectively.
    829     /// * [`challenge`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-challenge) is not a
    830     ///   base64url-encoded [`Challenge`].
    831     /// * Existence of duplicate keys for the keys that are expected.
    832     ///
    833     /// # Examples
    834     ///
    835     /// ```
    836     /// # use webauthn_rp::response::{ser_relaxed::SerdeJsonErr, CollectedClientData};
    837     /// assert!(!CollectedClientData::from_client_data_json_relaxed::<true>(b"\xef\xbb\xbf{
    838     ///   \"type\": \"webauthn.create\",
    839     ///   \"origin\": \"https://example.com\",
    840     ///   \"f\xffo\": 123,
    841     ///   \"topOrigin\": \"https://example.com\",
    842     ///   \"challenge\": \"AAAAAAAAAAAAAAAAAAAAAA\"
    843     /// }")?.cross_origin);
    844     /// # Ok::<_, SerdeJsonErr>(())
    845     /// ```
    846     #[expect(single_use_lifetimes, reason = "false positive")]
    847     #[cfg(feature = "serde_relaxed")]
    848     #[inline]
    849     pub fn from_client_data_json_relaxed<'b: 'a, const REGISTRATION: bool>(json: &'b [u8]) -> Result<Self, SerdeJsonErr> {
    850         ser_relaxed::RelaxedClientDataJsonParser::<REGISTRATION>::parse(json)
    851     }
    852 }
    853 /// Parser of 
    854 /// [`JSON-compatible serialization of client data`](https://www.w3.org/TR/webauthn-3/#collectedclientdata-json-compatible-serialization-of-client-data).
    855 trait ClientDataJsonParser {
    856     /// Error returned by [`Self::parse`].
    857     type Err;
    858     /// Parses `json` into `CollectedClientData` based on the value of
    859     /// [`type`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-type).
    860     ///
    861     /// # Errors
    862     ///
    863     /// Errors iff `json` cannot be parsed into a `CollectedClientData`.
    864     fn parse(json: &[u8]) -> Result<CollectedClientData<'_>, Self::Err>;
    865     /// Extracts [`challenge`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-challenge)
    866     /// from `json`.
    867     ///
    868     /// Note `json` should be minimally parsed such that only `challenge` is extracted; thus
    869     /// `Ok` being returned does _not_ mean `json` is in fact valid.
    870     fn get_sent_challenge(json: &[u8]) -> Result<SentChallenge, Self::Err>;
    871 }
    872 /// [`ClientDataJsonParser`] based on the
    873 /// [limited verification algorithm](https://www.w3.org/TR/webauthn-3/#clientdatajson-verification)
    874 /// with the following additional requirements:
    875 /// * Unknown keys are not allowed.
    876 /// * The entire payload is parsed; thus the payload is guaranteed to be valid UTF-8 and JSON.
    877 /// * [`CollectedClientData::top_origin`] can only be `Some` if
    878 ///   [`crossOrigin`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-crossorigin).
    879 /// * If `CollectedClientData::top_origin` is `Some`, then it does not equal [`CollectedClientData::origin`].
    880 ///
    881 /// `REGISTRATION` iff [`ClientDataJsonParser::parse`] requires
    882 /// [`type`](https://www.w3.org/TR/webauthn-3/#dom-collectedclientdata-type) to be `"webauthn.create"`;
    883 /// otherwise it must be `"webauthn.get"`.
    884 struct LimitedVerificationParser<const REGISTRATION: bool>;
    885 impl<const R: bool> LimitedVerificationParser<R> {
    886     /// Parses `val` as a JSON string with possibly trailing data. `val` MUST NOT begin with an opening quote. Upon
    887     /// encountering the first non-escaped quote, the parsed value is returned in addition to the remaining
    888     /// portion of `val` _after_ the closing quote. The limited verification algorithm is adhered to; thus the
    889     /// _only_ Unicode scalar values that are allowed (and must) be hex-escaped are U+0000 to U+001F inclusively.
    890     /// Similarly only `b'\\'` and `b'"'` are allowed (and must) be escaped with `b'\\'`.
    891     #[expect(unsafe_code, reason = "comment justifies its correctness")] 
    892     #[expect(clippy::arithmetic_side_effects, clippy::indexing_slicing, reason = "comments justify their correctness")]
    893     fn parse_string(val: &[u8]) -> Result<(Cow<'_, str>, &'_ [u8]), CollectedClientDataErr> {
    894         /// Tracks the state of the current Unicode scalar value that is being parsed.
    895         enum State {
    896             /// We are not parsing `'"'`, `'\\'`, or U+0000 to U+001F.
    897             Normal,
    898             /// We just encountered the escape character.
    899             Escape,
    900             /// We just encountered `b"\\u"`.
    901             UnicodeEscape,
    902             /// We just encountered `b"\\u0"`.
    903             UnicodeHex1,
    904             /// We just encountered `b"\\u00"`.
    905             UnicodeHex2,
    906             /// We just encountered `b"\\u000"` or `b"\\u001"`. The contained `u8` is `0` iff the former; otherwise
    907             /// `0x10`.
    908             UnicodeHex3(u8),
    909         }
    910         // We parse this as UTF-8 only at the end iff it is not empty. This contains all the potential Unicode scalar
    911         // values after de-escaping.
    912         let mut utf8 = Vec::new();
    913         // We check for all `u8`s already; thus we might as well check if we encounter a non-ASCII `u8`.
    914         // If we don't, then we can rely on `str::from_utf8_unchecked`.
    915         let mut all_ascii = true;
    916         // This tracks the start index of the next slice to add. We add slices iff we encounter the escape character or
    917         // we return the parsed `Cow` (i.e., encounter an unescaped `b'"'`).
    918         let mut cur_idx = 0;
    919         // The state of the yet-to-be-parsed Unicode scalar value.
    920         let mut state = State::Normal;
    921         for (counter, &b) in val.iter().enumerate() {
    922             match state {
    923                 State::Normal => {
    924                     match b {
    925                         b'"' => {
    926                             if utf8.is_empty() {
    927                                 if all_ascii {
    928                                     // `cur_idx` is 0 or 1. The latter is true iff `val` starts with a
    929                                     // `b'\\'` or `b'"'` but contains no other escaped characters.
    930                                     let s = &val[cur_idx..counter];
    931                                     // SAFETY:
    932                                     // `all_ascii` is `false` iff we encountered any `u8` that was not
    933                                     // an ASCII `u8`; thus we know `s` is valid ASCII which in turn means
    934                                     // it's valid UTF-8.
    935                                     let v = unsafe { str::from_utf8_unchecked(s) };
    936                                     // `val.len() > counter`, so indexing is fine and overflow cannot happen.
    937                                     return Ok((Cow::Borrowed(v), &val[counter + 1..]));
    938                                 }
    939                                 // `cur_idx` is 0 or 1. The latter is true iff `val` starts with a
    940                                 // `b'\\'` or `b'"'` but contains no other escaped characters.
    941                                 return str::from_utf8(&val[cur_idx..counter])
    942                                     .map_err(CollectedClientDataErr::Utf8)
    943                                     // `val.len() > counter`, so indexing is fine and overflow cannot happen.
    944                                     .map(|v| (Cow::Borrowed(v), &val[counter + 1..]));
    945                             }
    946                             // `val.len() > counter && counter >= cur_idx`, so indexing is fine and overflow
    947                             // cannot happen.
    948                             utf8.extend_from_slice(&val[cur_idx..counter]);
    949                             if all_ascii {
    950                                 // SAFETY:
    951                                 // `all_ascii` is `false` iff we encountered any `u8` that was not
    952                                 // an ASCII `u8`; thus we know `utf8` is valid ASCII which in turn means
    953                                 // it's valid UTF-8.
    954                                 let v = unsafe { String::from_utf8_unchecked(utf8) };
    955                                 // `val.len() > counter`, so indexing is fine and overflow cannot happen.
    956                                 return Ok((Cow::Owned(v), &val[counter + 1..]));
    957                             }
    958                             return String::from_utf8(utf8)
    959                                 .map_err(CollectedClientDataErr::Utf8Owned)
    960                                 // `val.len() > counter`, so indexing is fine and overflow cannot happen.
    961                                 .map(|v| (Cow::Owned(v), &val[counter + 1..]));
    962                         }
    963                         b'\\' => {
    964                             // Write the current slice of data.
    965                             utf8.extend_from_slice(&val[cur_idx..counter]);
    966                             state = State::Escape;
    967                         }
    968                         // ASCII is a subset of UTF-8 and this is a subset of ASCII. The code unit that is used for an
    969                         // ASCII Unicode scalar value _never_ appears in multi-code-unit Unicode scalar values; thus we
    970                         // error immediately.
    971                         ..=0x1f => return Err(CollectedClientDataErr::InvalidEscapedString),
    972                         128.. => all_ascii = false,
    973                         _ => (),
    974                     }
    975                 }
    976                 State::Escape => {
    977                     match b {
    978                         b'"' | b'\\' => {
    979                             // We start the next slice here since we need to add it.
    980                             cur_idx = counter;
    981                             state = State::Normal;
    982                         }
    983                         b'u' => {
    984                             state = State::UnicodeEscape;
    985                         }
    986                         _ => {
    987                             return Err(CollectedClientDataErr::InvalidEscapedString);
    988                         }
    989                     }
    990                 }
    991                 State::UnicodeEscape => {
    992                     if b != b'0' {
    993                         return Err(CollectedClientDataErr::InvalidEscapedString);
    994                     }
    995                     state = State::UnicodeHex1;
    996                 }
    997                 State::UnicodeHex1 => {
    998                     if b != b'0' {
    999                         return Err(CollectedClientDataErr::InvalidEscapedString);
   1000                     }
   1001                     state = State::UnicodeHex2;
   1002                 }
   1003                 State::UnicodeHex2 => {
   1004                     state = State::UnicodeHex3(match b {
   1005                         b'0' => 0,
   1006                         b'1' => 0x10,
   1007                         _ => return Err(CollectedClientDataErr::InvalidEscapedString),
   1008                     });
   1009                 }
   1010                 State::UnicodeHex3(v) => {
   1011                     match b {
   1012                         // Only and all _lowercase_ hex is allowed.
   1013                         b'0'..=b'9' | b'a'..=b'f' => {
   1014                             // When `b < b'a'`, then `b >= b'0'`; and `b'a' > 87`; thus underflow cannot happen.
   1015                             // Note `b'a' - 10 == 87`.
   1016                             utf8.push(v | (b - if b < b'a' { b'0' } else { 87 }));
   1017                             // `counter < val.len()`, so overflow cannot happen.
   1018                             cur_idx = counter + 1;
   1019                             state = State::Normal;
   1020                         }
   1021                         _ => return Err(CollectedClientDataErr::InvalidEscapedString),
   1022                     }
   1023                 }
   1024             }
   1025         }
   1026         // We never encountered an unescaped `b'"'`; thus we could not parse a string.
   1027         Err(CollectedClientDataErr::InvalidObject)
   1028     }
   1029 }
   1030 impl<const R: bool> ClientDataJsonParser for LimitedVerificationParser<R> {
   1031     type Err = CollectedClientDataErr;
   1032     #[expect(clippy::little_endian_bytes, reason = "Challenge::serialize and this need to be consistent across architectures")]
   1033     #[expect(clippy::too_many_lines, reason = "110 lines is fine")]
   1034     fn parse(json: &[u8]) -> Result<CollectedClientData<'_>, Self::Err> {
   1035         // `{"type":"webauthn.<create|get>","challenge":"<22 bytes>","origin":"<bytes>","crossOrigin":<true|false>[,"topOrigin":"<bytes>"][,<anything>]}`.
   1036         /// First portion of `value`.
   1037         const HEADER: &[u8; 18] = br#"{"type":"webauthn."#;
   1038         /// `get`.
   1039         const GET: &[u8; 3] = b"get";
   1040         /// `create`.
   1041         const CREATE: &[u8; 6] = b"create";
   1042         /// Value after type before the start of the base64url-encoded challenge.
   1043         const AFTER_TYPE: &[u8; 15] = br#"","challenge":""#;
   1044         /// Value after challenge before the start of the origin value.
   1045         const AFTER_CHALLENGE: &[u8; 12] = br#"","origin":""#;
   1046         /// Value after origin before the start of the crossOrigin value.
   1047         const AFTER_ORIGIN: &[u8; 15] = br#","crossOrigin":"#;
   1048         /// `true`.
   1049         const TRUE: &[u8; 4] = b"true";
   1050         /// `false`.
   1051         const FALSE: &[u8; 5] = b"false";
   1052         /// Value after crossOrigin before the start of the topOrigin value.
   1053         const AFTER_CROSS: &[u8; 13] = br#""topOrigin":""#;
   1054         json.split_last().ok_or(CollectedClientDataErr::Len).and_then(|(last, last_rem)| {
   1055             if *last == b'}' {
   1056                 last_rem.split_at_checked(HEADER.len()).ok_or(CollectedClientDataErr::Len).and_then(|(header, header_rem)| {
   1057                     if header == HEADER {
   1058                         if R {
   1059                             header_rem.split_at_checked(CREATE.len()).ok_or(CollectedClientDataErr::Len).and_then(|(create, create_rem)| {
   1060                                 if create == CREATE {
   1061                                     Ok(create_rem)
   1062                                 } else {
   1063                                     Err(CollectedClientDataErr::Type)
   1064                                 }
   1065                             })
   1066                         } else {
   1067                             header_rem.split_at_checked(GET.len()).ok_or(CollectedClientDataErr::Len).and_then(|(get, get_rem)| {
   1068                                 if get == GET {
   1069                                     Ok(get_rem)
   1070                                 } else {
   1071                                     Err(CollectedClientDataErr::Type)
   1072                                 }
   1073                             })
   1074                         }.and_then(|type_rem| {
   1075                             type_rem.split_at_checked(AFTER_TYPE.len()).ok_or(CollectedClientDataErr::Len).and_then(|(chall_key, chall_key_rem)| {
   1076                                 if chall_key == AFTER_TYPE {
   1077                                     chall_key_rem.split_at_checked(Challenge::BASE64_LEN).ok_or(CollectedClientDataErr::Len).and_then(|(base64_chall, base64_chall_rem)| {
   1078                                         let mut chall = [0; 16];
   1079                                         base64url_nopad::decode_buffer_exact(base64_chall, chall.as_mut_slice()).map_err(|_e| CollectedClientDataErr::Challenge).and_then(|()| {
   1080                                             base64_chall_rem.split_at_checked(AFTER_CHALLENGE.len()).ok_or(CollectedClientDataErr::Len).and_then(|(origin_key, origin_key_rem)| {
   1081                                                 if origin_key == AFTER_CHALLENGE {
   1082                                                     Self::parse_string(origin_key_rem).and_then(|(origin, origin_rem)| {
   1083                                                         origin_rem.split_at_checked(AFTER_ORIGIN.len()).ok_or(CollectedClientDataErr::Len).and_then(|(cross_key, cross_key_rem)| {
   1084                                                             if cross_key == AFTER_ORIGIN {
   1085                                                                 // `FALSE.len() > TRUE.len()`, so we check for `FALSE` in `and_then`.
   1086                                                                 cross_key_rem.split_at_checked(TRUE.len()).ok_or(CollectedClientDataErr::Len).and_then(|(cross_true, cross_true_rem)| {
   1087                                                                     if cross_true == TRUE {
   1088                                                                         Ok((true, cross_true_rem))
   1089                                                                     } else {
   1090                                                                         cross_key_rem.split_at_checked(FALSE.len()).ok_or(CollectedClientDataErr::Len).and_then(|(cross_false, cross_false_rem)| {
   1091                                                                             if cross_false == FALSE {
   1092                                                                                 Ok((false, cross_false_rem))
   1093                                                                             } else {
   1094                                                                                 Err(CollectedClientDataErr::CrossOrigin)
   1095                                                                             }
   1096                                                                         })
   1097                                                                     }.and_then(|(cross, cross_rem)| {
   1098                                                                         cross_rem.split_first().map_or(Ok((cross, None)), |(comma, comma_rem)| {
   1099                                                                             if *comma == b',' {
   1100                                                                                 comma_rem.split_at_checked(AFTER_CROSS.len()).map_or(Ok((cross, None)), |(top, top_rem)| {
   1101                                                                                     if top == AFTER_CROSS {
   1102                                                                                         if cross {
   1103                                                                                             Self::parse_string(top_rem).and_then(|(top_origin, top_origin_rem)| {
   1104                                                                                                 top_origin_rem.first().map_or(Ok(()), |v| {
   1105                                                                                                     if *v == b',' {
   1106                                                                                                         Ok(())
   1107                                                                                                     } else {
   1108                                                                                                         Err(CollectedClientDataErr::InvalidObject)
   1109                                                                                                     }
   1110                                                                                                 }).and_then(|()| {
   1111                                                                                                     if origin == top_origin {
   1112                                                                                                         Err(CollectedClientDataErr::TopOriginSameAsOrigin)
   1113                                                                                                     } else {
   1114                                                                                                         Ok((true, Some(Origin(top_origin))))
   1115                                                                                                     }
   1116                                                                                                 })
   1117                                                                                             })
   1118                                                                                         } else {
   1119                                                                                             Err(CollectedClientDataErr::TopOriginWithoutCrossOrigin)
   1120                                                                                         }
   1121                                                                                     } else {
   1122                                                                                         Ok((cross, None))
   1123                                                                                     }
   1124                                                                                 })
   1125                                                                             } else {
   1126                                                                                 Err(CollectedClientDataErr::InvalidObject)
   1127                                                                             }
   1128                                                                         }).map(|(cross_origin, top_origin)| CollectedClientData { challenge: SentChallenge(u128::from_le_bytes(chall)), origin: Origin(origin), cross_origin, top_origin, })
   1129                                                                     })
   1130                                                                 })
   1131                                                             } else {
   1132                                                                 Err(CollectedClientDataErr::CrossOriginKey)
   1133                                                             }
   1134                                                         })
   1135                                                     })
   1136                                                 } else {
   1137                                                     Err(CollectedClientDataErr::OriginKey)
   1138                                                 }
   1139                                             })
   1140                                         })
   1141                                     })
   1142                                 } else {
   1143                                     Err(CollectedClientDataErr::ChallengeKey)
   1144                                 }
   1145                             })
   1146                         })
   1147                     } else {
   1148                         Err(CollectedClientDataErr::InvalidStart)
   1149                     }
   1150                 })
   1151             } else {
   1152                 Err(CollectedClientDataErr::InvalidObject)
   1153             }
   1154         })
   1155     }
   1156     #[expect(clippy::arithmetic_side_effects, reason = "comment justifies correctness")]
   1157     #[expect(clippy::little_endian_bytes, reason = "Challenge::serialize and this need to be consistent across architectures")]
   1158     fn get_sent_challenge(json: &[u8]) -> Result<SentChallenge, Self::Err> {
   1159         // Index 39.
   1160         // `{"type":"webauthn.create","challenge":"AAAAAAAAAAAAAAAAAAAAAA"...`.
   1161         // Index 36.
   1162         // `{"type":"webauthn.get","challenge":"AAAAAAAAAAAAAAAAAAAAAA"...`.
   1163         let idx = if R { 39 } else { 36 };
   1164         // This maxes at 39 + 22 = 61; thus overflow is not an issue.
   1165         json.get(idx..idx + Challenge::BASE64_LEN).ok_or(CollectedClientDataErr::Len).and_then(|chall_slice| {
   1166             let mut chall = [0; 16];
   1167             base64url_nopad::decode_buffer_exact(chall_slice, chall.as_mut_slice()).map_err(|_e| CollectedClientDataErr::Challenge).map(|()| {
   1168                 SentChallenge(u128::from_le_bytes(chall))
   1169             })
   1170         })
   1171     }
   1172 }
   1173 /// Authenticator extension outputs;
   1174 pub(super) trait AuthExtOutput {
   1175     /// MUST return `true` iff there is no data.
   1176     fn missing(self) -> bool;
   1177 }
   1178 /// Successful return type from [`FromCbor::from_cbor`].
   1179 struct CborSuccess<'a, T> {
   1180     /// Value parsed from the slice.
   1181     value: T,
   1182     /// Remaining unprocessed data.
   1183     remaining: &'a [u8],
   1184 }
   1185 /// Types that parse
   1186 /// [CTAP2 canonical CBOR encoding form](https://fidoalliance.org/specs/fido-v2.2-rd-20230321/fido-client-to-authenticator-protocol-v2.2-rd-20230321.html#ctap2-canonical-cbor-encoding-form)
   1187 /// data without necessarily consuming all the data.
   1188 ///
   1189 /// The purpose of this `trait` is to allow chains of types to progressively consume `cbor` by passing
   1190 /// [`CborSuccess::remaining`] into the next `FromCbor` type.
   1191 trait FromCbor<'a>: Sized {
   1192     /// Error when conversion fails.
   1193     type Err;
   1194     /// Parses `cbor` into `Self`.
   1195     ///
   1196     /// # Errors
   1197     ///
   1198     /// Errors if `cbor` cannot be parsed into `Self:`.
   1199     fn from_cbor(cbor: &'a [u8]) -> Result<CborSuccess<'a, Self>, Self::Err>;
   1200 }
   1201 /// Error returned from [`A::from_cbor`] `where A: AuthData`.
   1202 enum AuthenticatorDataErr<UpErr, CredData, AuthExt> {
   1203     /// The `slice` had an invalid length.
   1204     Len,
   1205     /// [UP](https://www.w3.org/TR/webauthn-3/#authdata-flags-at) bit was 0.
   1206     UserNotPresent(UpErr),
   1207     /// Bit 1 in [`flags`](https://www.w3.org/TR/webauthn-3/#authdata-flags) is not 0.
   1208     FlagsBit1Not0,
   1209     /// Bit 5 in [`flags`](https://www.w3.org/TR/webauthn-3/#authdata-flags) is not 0.
   1210     FlagsBit5Not0,
   1211     /// [AT](https://www.w3.org/TR/webauthn-3/#authdata-flags-at) bit was 0 during registration or was 1
   1212     /// during authentication.
   1213     AttestedCredentialData,
   1214     /// [BE](https://www.w3.org/TR/webauthn-3/#authdata-flags-be) and
   1215     /// [BS](https://www.w3.org/TR/webauthn-3/#authdata-flags-bs) bits were 0 and 1 respectively.
   1216     BackupWithoutEligibility,
   1217     /// Error returned from [`AttestedCredentialData::from_cbor`].
   1218     AttestedCredential(CredData),
   1219     /// Error returned from [`register::AuthenticatorExtensionOutput::from_cbor`] and
   1220     /// [`auth::AuthenticatorExtensionOutput::from_cbor`].
   1221     AuthenticatorExtension(AuthExt),
   1222     /// [ED](https://www.w3.org/TR/webauthn-3/#authdata-flags-ed) bit was 0, but
   1223     /// [`extensions`](https://www.w3.org/TR/webauthn-3/#authdata-extensions) existed.
   1224     NoExtensionBitWithData,
   1225     /// [ED](https://www.w3.org/TR/webauthn-3/#authdata-flags-ed) bit was 1, but
   1226     /// [`extensions`](https://www.w3.org/TR/webauthn-3/#authdata-extensions) did not exist.
   1227     ExtensionBitWithoutData,
   1228     /// There was trailing data that could not be deserialized.
   1229     TrailingData,
   1230 }
   1231 impl<U, C: Display, A: Display> Display for AuthenticatorDataErr<U, C, A> {
   1232     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
   1233         match *self {
   1234             Self::Len => f.write_str("authenticator data had an invalid length"),
   1235             Self::UserNotPresent(_) => f.write_str("user was not present"),
   1236             Self::FlagsBit1Not0 => f.write_str("flags 1-bit was 1"),
   1237             Self::FlagsBit5Not0 => f.write_str("flags 5-bit was 1"),
   1238             Self::AttestedCredentialData => f.write_str("attested credential data was included during authentication or was not included during registration"),
   1239             Self::BackupWithoutEligibility => {
   1240                 f.write_str("backup state bit was 1 despite backup eligibility being 0")
   1241             }
   1242             Self::AttestedCredential(ref err) => err.fmt(f),
   1243             Self::AuthenticatorExtension(ref err) => err.fmt(f),
   1244             Self::NoExtensionBitWithData => {
   1245                 f.write_str("extension bit was 0 despite extensions existing")
   1246             }
   1247             Self::ExtensionBitWithoutData => {
   1248                 f.write_str("extension bit was 1 despite no extensions existing")
   1249             }
   1250             Self::TrailingData => {
   1251                 f.write_str("slice had trailing data that could not be deserialized")
   1252             }
   1253         }
   1254     }
   1255 }
   1256 impl From<AuthenticatorDataErr<Infallible, AttestedCredentialDataErr, RegAuthExtErr>> for RegAuthDataErr {
   1257     #[inline]
   1258     fn from(value: AuthenticatorDataErr<Infallible, AttestedCredentialDataErr, RegAuthExtErr>) -> Self {
   1259         match value {
   1260             AuthenticatorDataErr::Len => Self::Len,
   1261             AuthenticatorDataErr::UserNotPresent(v) => match v {},
   1262             AuthenticatorDataErr::FlagsBit1Not0 => Self::FlagsBit1Not0,
   1263             AuthenticatorDataErr::FlagsBit5Not0 => Self::FlagsBit5Not0,
   1264             AuthenticatorDataErr::AttestedCredentialData => Self::AttestedCredentialDataNotIncluded,
   1265             AuthenticatorDataErr::BackupWithoutEligibility => Self::BackupWithoutEligibility,
   1266             AuthenticatorDataErr::AttestedCredential(err) => Self::AttestedCredential(err),
   1267             AuthenticatorDataErr::AuthenticatorExtension(err) => Self::AuthenticatorExtension(err),
   1268             AuthenticatorDataErr::NoExtensionBitWithData => Self::NoExtensionBitWithData,
   1269             AuthenticatorDataErr::ExtensionBitWithoutData => Self::ExtensionBitWithoutData,
   1270             AuthenticatorDataErr::TrailingData => Self::TrailingData,
   1271         }
   1272     }
   1273 }
   1274 impl From<AuthenticatorDataErr<(), Infallible, AuthAuthExtErr>> for AuthAuthDataErr {
   1275     #[inline]
   1276     fn from(value: AuthenticatorDataErr<(), Infallible, AuthAuthExtErr>) -> Self {
   1277         match value {
   1278             AuthenticatorDataErr::Len => Self::Len,
   1279             AuthenticatorDataErr::UserNotPresent(()) => Self::UserNotPresent,
   1280             AuthenticatorDataErr::FlagsBit1Not0 => Self::FlagsBit1Not0,
   1281             AuthenticatorDataErr::FlagsBit5Not0 => Self::FlagsBit5Not0,
   1282             AuthenticatorDataErr::AttestedCredentialData => Self::AttestedCredentialDataIncluded,
   1283             AuthenticatorDataErr::AttestedCredential(val) => match val {},
   1284             AuthenticatorDataErr::BackupWithoutEligibility => Self::BackupWithoutEligibility,
   1285             AuthenticatorDataErr::AuthenticatorExtension(err) => Self::AuthenticatorExtension(err),
   1286             AuthenticatorDataErr::NoExtensionBitWithData => Self::NoExtensionBitWithData,
   1287             AuthenticatorDataErr::ExtensionBitWithoutData => Self::ExtensionBitWithoutData,
   1288             AuthenticatorDataErr::TrailingData => Self::TrailingData,
   1289         }
   1290     }
   1291 }
   1292 impl<'a, A> FromCbor<'a> for A
   1293 where
   1294     A: AuthData<'a>,
   1295     A::CredData: FromCbor<'a>,
   1296     A::Ext: FromCbor<'a>,
   1297 {
   1298     type Err = AuthenticatorDataErr<A::UpBitErr, <A::CredData as FromCbor<'a>>::Err, <A::Ext as FromCbor<'a>>::Err>;
   1299     #[expect(clippy::big_endian_bytes, reason = "CBOR integers are in big-endian")]
   1300     fn from_cbor(cbor: &'a [u8]) -> Result<CborSuccess<'a, Self>, Self::Err> {
   1301         /// Length of `signCount`.
   1302         const SIGN_COUNT_LEN: usize = 4;
   1303         /// `UP` bit (i.e., bit 0) set to 1.
   1304         const UP: u8 = 0b0000_0001;
   1305         /// `RFU1` bit (i.e., bit 1) set to 1.
   1306         const RFU1: u8 = UP << 1;
   1307         /// `UV` bit (i.e., bit 2) set to 1.
   1308         const UV: u8 = RFU1 << 1;
   1309         /// `BE` bit (i.e., bit 3) set to 1.
   1310         const BE: u8 = UV << 1;
   1311         /// `BS` bit (i.e., bit 4) set to 1.
   1312         const BS: u8 = BE << 1;
   1313         /// `RFU2` bit (i.e., bit 5) set to 1.
   1314         const RFU2: u8 = BS << 1;
   1315         /// `AT` bit (i.e., bit 6) set to 1.
   1316         const AT: u8 = RFU2 << 1;
   1317         /// `ED` bit (i.e., bit 7) set to 1.
   1318         const ED: u8 = AT << 1;
   1319         cbor.split_at_checked(Sha256::output_size()).ok_or_else(|| AuthenticatorDataErr::Len).and_then(|(rp_id_slice, rp_id_rem)| {
   1320             rp_id_rem.split_first().ok_or_else(|| AuthenticatorDataErr::Len).and_then(|(&flag, flag_rem)| {
   1321                 let user_present = flag & UP == UP;
   1322                 if user_present {
   1323                     Ok(())
   1324                 } else {
   1325                     A::user_is_not_present().map_err(AuthenticatorDataErr::UserNotPresent)   
   1326                 }
   1327                 .and_then(|()| {
   1328                     if flag & RFU1 == 0 {
   1329                         if flag & RFU2 == 0 {
   1330                             let at_bit = A::contains_at_bit();
   1331                             if flag & AT == AT {
   1332                                 if at_bit {
   1333                                     Ok(())
   1334                                 } else {
   1335                                     Err(AuthenticatorDataErr::AttestedCredentialData)
   1336                                 }
   1337                             } else if at_bit {
   1338                                 Err(AuthenticatorDataErr::AttestedCredentialData)
   1339                             } else {
   1340                                 Ok(())
   1341                             }.and_then(|()| {
   1342                                 let bs = flag & BS == BS;
   1343                                 if flag & BE == BE {
   1344                                     if bs {
   1345                                         Ok(Backup::Exists)
   1346                                     } else {
   1347                                         Ok(Backup::Eligible)
   1348                                     }
   1349                                 } else if bs {
   1350                                     Err(AuthenticatorDataErr::BackupWithoutEligibility)
   1351                                 } else {
   1352                                     Ok(Backup::NotEligible)
   1353                                 }
   1354                                 .and_then(|backup| {
   1355                                     flag_rem.split_at_checked(SIGN_COUNT_LEN).ok_or_else(|| AuthenticatorDataErr::Len).and_then(|(count_slice, count_rem)| {
   1356                                         A::CredData::from_cbor(count_rem).map_err(AuthenticatorDataErr::AttestedCredential).and_then(|att_data| {
   1357                                             A::Ext::from_cbor(att_data.remaining).map_err(AuthenticatorDataErr::AuthenticatorExtension).and_then(|ext| {
   1358                                                 if ext.remaining.is_empty() {
   1359                                                     let ed = flag & ED == ED;
   1360                                                     if ext.value.missing() {
   1361                                                         if ed {
   1362                                                             Err(AuthenticatorDataErr::ExtensionBitWithoutData)
   1363                                                         } else {
   1364                                                             Ok(())
   1365                                                         }
   1366                                                     } else if ed {
   1367                                                         Ok(())
   1368                                                     } else {
   1369                                                         Err(AuthenticatorDataErr::NoExtensionBitWithData)
   1370                                                     }.map(|()| {
   1371                                                         let mut sign_count = [0; SIGN_COUNT_LEN];
   1372                                                         sign_count.copy_from_slice(count_slice);
   1373                                                         // `signCount` is in big-endian.
   1374                                                         CborSuccess { value: A::new(rp_id_slice, Flag { user_present, user_verified: flag & UV == UV, backup, }, u32::from_be_bytes(sign_count), att_data.value, ext.value), remaining: ext.remaining, }
   1375                                                     })
   1376                                                 } else {
   1377                                                     Err(AuthenticatorDataErr::TrailingData)
   1378                                                 }
   1379                                             })
   1380                                         })
   1381                                     })
   1382                                 })
   1383                             })
   1384                         } else {
   1385                             Err(AuthenticatorDataErr::FlagsBit5Not0)
   1386                         }
   1387                     } else {
   1388                         Err(AuthenticatorDataErr::FlagsBit1Not0)
   1389                     }
   1390                 })
   1391             })
   1392         })
   1393     }
   1394 }
   1395 /// Data returned by [`AuthDataContainer::from_data`].
   1396 pub(super) struct ParsedAuthData<'a, A> {
   1397     /// The data the CBOR is parsed into.
   1398     data: A,
   1399     /// The raw authenticator data and 32-bytes of trailing data.
   1400     auth_data_and_32_trailing_bytes: &'a [u8],
   1401 }
   1402 /// Error returned by [`AuthResponse::parse_data_and_verify_sig`].
   1403 pub(super) enum AuthRespErr<AuthDataErr> {
   1404     /// Variant returned when parsing
   1405     /// [`clientDataJSON`](https://www.w3.org/TR/webauthn-3/#dom-authenticatorresponse-clientdatajson)
   1406     /// into [`CollectedClientData`] fails.
   1407     CollectedClientData(CollectedClientDataErr),
   1408     /// Variant returned when parsing
   1409     /// [`clientDataJSON`](https://www.w3.org/TR/webauthn-3/#dom-authenticatorresponse-clientdatajson)
   1410     /// in a "relaxed" way into [`CollectedClientData`] fails.
   1411     #[cfg(feature = "serde_relaxed")]
   1412     CollectedClientDataRelaxed(SerdeJsonErr),
   1413     /// Variant returned when parsing [`AuthResponse::Auth`] fails.
   1414     Auth(AuthDataErr),
   1415     /// Variant when the [`CompressedPubKey`] or [`UncompressePubKey`] is not valid.
   1416     PubKey(PubKeyErr),
   1417     /// Variant returned when the signature, if one exists, associated with
   1418     /// [`Self::AuthResponse`] is invalid.
   1419     Signature,
   1420 }
   1421 impl<A: Display> Display for AuthRespErr<A> {
   1422     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
   1423         match *self {
   1424             Self::CollectedClientData(ref err) => write!(f, "CollectedClientData could not be parsed: {err}"),
   1425             #[cfg(feature = "serde_relaxed")]
   1426             Self::CollectedClientDataRelaxed(ref err) => write!(f, "CollectedClientData could not be parsed: {err}"),
   1427             Self::Auth(ref err) => write!(f, "auth data could not be parsed: {err}"),
   1428             Self::PubKey(err) => err.fmt(f),
   1429             Self::Signature => f.write_str("the signature over the authenticator data and CollectedClientData could not be verified"),
   1430         }
   1431     }
   1432 }
   1433 impl From<AuthRespErr<AttestationObjectErr>> for RegCeremonyErr {
   1434     #[inline]
   1435     fn from(value: AuthRespErr<AttestationObjectErr>) -> Self {
   1436         match value {
   1437             AuthRespErr::CollectedClientData(err) => Self::CollectedClientData(err),
   1438             #[cfg(feature = "serde_relaxed")]
   1439             AuthRespErr::CollectedClientDataRelaxed(err) => Self::CollectedClientDataRelaxed(err),
   1440             AuthRespErr::Auth(err) => Self::AttestationObject(err),
   1441             AuthRespErr::PubKey(err) => Self::PubKey(err),
   1442             AuthRespErr::Signature => Self::AttestationSignature,
   1443         }
   1444     }
   1445 }
   1446 impl From<AuthRespErr<AuthAuthDataErr>> for AuthCeremonyErr {
   1447     #[inline]
   1448     fn from(value: AuthRespErr<AuthAuthDataErr>) -> Self {
   1449         match value {
   1450             AuthRespErr::CollectedClientData(err) => Self::CollectedClientData(err),
   1451             #[cfg(feature = "serde_relaxed")]
   1452             AuthRespErr::CollectedClientDataRelaxed(err) => Self::CollectedClientDataRelaxed(err),
   1453             AuthRespErr::Auth(err) => Self::AuthenticatorData(err),
   1454             AuthRespErr::PubKey(err) => Self::PubKey(err),
   1455             AuthRespErr::Signature => Self::AssertionSignature,
   1456         }
   1457     }
   1458 }
   1459 /// [Authenticator data](https://www.w3.org/TR/webauthn-3/#authenticator-data)
   1460 /// container.
   1461 ///
   1462 /// Note [`Self::Auth`] may be `Self`.
   1463 pub(super) trait AuthDataContainer<'a>: Sized {
   1464     /// [Authenticator data](https://www.w3.org/TR/webauthn-3/#authenticator-data).
   1465     type Auth: AuthData<'a>;
   1466     /// Error returned from [`Self::from_data`].
   1467     type Err;
   1468     /// Converts `data` into [`ParsedAuthData`].
   1469     ///
   1470     /// # Errors
   1471     ///
   1472     /// Errors iff `data` cannot be converted into `ParsedAuthData`.
   1473     fn from_data(data: &'a [u8]) -> Result<ParsedAuthData<'a, Self>, Self::Err>;
   1474     /// Returns the contained
   1475     /// [authenticator data](https://www.w3.org/TR/webauthn-3/#authenticator-data).
   1476     fn authenticator_data(&self) -> &Self::Auth;
   1477 }
   1478 /// [`AuthenticatorResponse`](https://www.w3.org/TR/webauthn-3/#authenticatorresponse).
   1479 pub(super) trait AuthResponse {
   1480     /// [Attestation object](https://www.w3.org/TR/webauthn-3/#attestation-object) or
   1481     /// [authenticator data](https://www.w3.org/TR/webauthn-3/#authenticator-data).
   1482     type Auth<'a>: AuthDataContainer<'a> where Self: 'a;
   1483     /// Public key to use to verify the contained signature.
   1484     type CredKey<'a>;
   1485     /// Parses
   1486     /// [`clientDataJSON`](https://www.w3.org/TR/webauthn-3/#dom-authenticatorresponse-clientdatajson)
   1487     /// based on `RELAXED` and [`Self::Auth`] via [`AuthDataContainer::from_data`] in addition to
   1488     /// verifying any possible signature over the concatenation of the raw
   1489     /// [`AuthDataContainer::Auth`] and `clientDataJSON` using `key` or the contained
   1490     /// public key if one exists. If `Self` contains a public key and should not be passed one, then it should set
   1491     /// [`Self::CredKey`] to `()`.
   1492     ///
   1493     /// # Errors
   1494     ///
   1495     /// Errors iff parsing `clientDataJSON` errors, [`AuthDataContainer::from_data`] does, or the signature
   1496     /// is invalid.
   1497     ///
   1498     /// # Panics
   1499     ///
   1500     /// `panic`s iff `relaxed` and `serde_relaxed` is not enabled.
   1501     #[expect(
   1502         clippy::type_complexity,
   1503         reason = "type aliases with bounds are even more problematic at least until lazy_type_alias is stable"
   1504     )]
   1505     fn parse_data_and_verify_sig(&self, key: Self::CredKey<'_>, relaxed: bool) -> Result<(CollectedClientData<'_>, Self::Auth<'_>), AuthRespErr<<Self::Auth<'_> as AuthDataContainer<'_>>::Err>>;
   1506 }
   1507 /// Ceremony response (i.e., [`PublicKeyCredential`](https://www.w3.org/TR/webauthn-3/#publickeycredential)).
   1508 pub(super) trait Response {
   1509     /// [`AuthenticatorResponse`](https://www.w3.org/TR/webauthn-3/#authenticatorresponse).
   1510     type Auth: AuthResponse;
   1511     /// [`response`](https://www.w3.org/TR/webauthn-3/#dom-publickeycredential-response).
   1512     fn auth(&self) -> &Self::Auth;
   1513 }
   1514 /// Error returned from [`Ceremony::partial_validate`].
   1515 pub(super) enum CeremonyErr<AuthDataErr> {
   1516     /// Timeout occurred.
   1517     Timeout,
   1518     /// Read [`AuthRespErr`] for information.
   1519     AuthResp(AuthRespErr<AuthDataErr>),
   1520     /// Origin did not validate.
   1521     OriginMismatch,
   1522     /// Cross origin was `true` but was not allowed to be.
   1523     CrossOrigin,
   1524     /// Top origin did not validate.
   1525     TopOriginMismatch,
   1526     /// Challenges don't match.
   1527     ChallengeMismatch,
   1528     /// `rpIdHash` does not match the SHA-256 hash of the [`RpId`].
   1529     RpIdHashMismatch,
   1530     /// User was not verified despite being required to.
   1531     UserNotVerified,
   1532     /// [`Backup::NotEligible`] was not sent back despite [`BackupReq::NotEligible`].
   1533     BackupEligible,
   1534     /// [`Backup::NotEligible`] was sent back despite [`BackupReq::Eligible`].
   1535     BackupNotEligible,
   1536     /// [`Backup::Eligible`] was not sent back despite [`BackupReq::EligibleNoteExists`].
   1537     BackupExists,
   1538     /// [`Backup::Exists`] was not sent back despite [`BackupReq::Exists`].
   1539     BackupDoesNotExist,
   1540 }
   1541 impl<A: Display> Display for CeremonyErr<A> {
   1542     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
   1543         match *self {
   1544             Self::Timeout => f.write_str("ceremony timed out"),
   1545             Self::AuthResp(ref err) => err.fmt(f),
   1546             Self::OriginMismatch => {
   1547                 f.write_str("the origin sent from the client is not an allowed origin")
   1548             }
   1549             Self::CrossOrigin => {
   1550                 f.write_str("cross origin was from the client, but it is not allowed")
   1551             }
   1552             Self::TopOriginMismatch => {
   1553                 f.write_str("the top origin sent from the client is not an allowed top origin")
   1554             }
   1555             Self::ChallengeMismatch => f.write_str(
   1556                 "the challenge sent to the client does not match the challenge sent back",
   1557             ),
   1558             Self::RpIdHashMismatch => f.write_str(
   1559                 "the SHA-256 hash of the RP ID doesn't match the hash sent from the client",
   1560             ),
   1561             Self::UserNotVerified => f.write_str("user was not verified despite being required to"),
   1562             Self::BackupEligible => f.write_str("credential is eligible to be backed up despite requiring that it not be"),
   1563             Self::BackupNotEligible => f.write_str("credential is not eligible to be backed up despite requiring that it be"),
   1564             Self::BackupExists => f.write_str("credential backup exists despite requiring that a backup not exist"),
   1565             Self::BackupDoesNotExist => f.write_str("credential backup does not exist despite requiring that a backup exist"),
   1566         }
   1567     }
   1568 }
   1569 impl From<CeremonyErr<AttestationObjectErr>> for RegCeremonyErr {
   1570     #[inline]
   1571     fn from(value: CeremonyErr<AttestationObjectErr>) -> Self {
   1572         match value {
   1573             CeremonyErr::Timeout => Self::Timeout,
   1574             CeremonyErr::AuthResp(err) => err.into(),
   1575             CeremonyErr::OriginMismatch => Self::OriginMismatch,
   1576             CeremonyErr::CrossOrigin => Self::CrossOrigin,
   1577             CeremonyErr::TopOriginMismatch => Self::TopOriginMismatch,
   1578             CeremonyErr::ChallengeMismatch => Self::ChallengeMismatch,
   1579             CeremonyErr::RpIdHashMismatch => Self::RpIdHashMismatch,
   1580             CeremonyErr::UserNotVerified => Self::UserNotVerified,
   1581             CeremonyErr::BackupEligible => Self::BackupEligible,
   1582             CeremonyErr::BackupNotEligible => Self::BackupNotEligible,
   1583             CeremonyErr::BackupExists => Self::BackupExists,
   1584             CeremonyErr::BackupDoesNotExist => Self::BackupDoesNotExist,
   1585         }
   1586     }
   1587 }
   1588 impl From<CeremonyErr<AuthAuthDataErr>> for AuthCeremonyErr {
   1589     #[inline]
   1590     fn from(value: CeremonyErr<AuthAuthDataErr>) -> Self {
   1591         match value {
   1592             CeremonyErr::Timeout => Self::Timeout,
   1593             CeremonyErr::AuthResp(err) => err.into(),
   1594             CeremonyErr::OriginMismatch => Self::OriginMismatch,
   1595             CeremonyErr::CrossOrigin => Self::CrossOrigin,
   1596             CeremonyErr::TopOriginMismatch => Self::TopOriginMismatch,
   1597             CeremonyErr::ChallengeMismatch => Self::ChallengeMismatch,
   1598             CeremonyErr::RpIdHashMismatch => Self::RpIdHashMismatch,
   1599             CeremonyErr::UserNotVerified => Self::UserNotVerified,
   1600             CeremonyErr::BackupEligible => Self::BackupEligible,
   1601             CeremonyErr::BackupNotEligible => Self::BackupNotEligible,
   1602             CeremonyErr::BackupExists => Self::BackupExists,
   1603             CeremonyErr::BackupDoesNotExist => Self::BackupDoesNotExist,
   1604         }
   1605     }
   1606 }
   1607 /// [`AllAcceptedCredentialsOptions`](https://www.w3.org/TR/webauthn-3/#dictdef-allacceptedcredentialsoptions).
   1608 ///
   1609 /// This can be sent to _an already authenticated user_ to inform what credentials are currently registered.
   1610 /// This can be useful when a user deletes credentials on the RP's side but does not do so on the authenticator.
   1611 /// When the client forwards this response to the authenticator, it can remove all credentials that don't have
   1612 /// a [`CredentialId`] in [`Self::all_accepted_credential_ids`].
   1613 #[derive(Debug)]
   1614 pub struct AllAcceptedCredentialsOptions<'rp, 'user, const USER_LEN: usize> {
   1615     /// [`rpId`](https://www.w3.org/TR/webauthn-3/#dictdef-allacceptedcredentialsoptions-rpid).
   1616     pub rp_id: &'rp RpId,
   1617     /// [`userId`](https://www.w3.org/TR/webauthn-3/#dictdef-allacceptedcredentialsoptions-userid).
   1618     pub user_id: &'user UserHandle<USER_LEN>,
   1619     /// [`allAcceptedCredentialIds`](https://www.w3.org/TR/webauthn-3/#dictdef-allacceptedcredentialsoptions-allacceptedcredentialids).
   1620     pub all_accepted_credential_ids: Vec<CredentialId<Box<[u8]>>>,
   1621 }
   1622 /// [`CurrentUserDetailsOptions`](https://www.w3.org/TR/webauthn-3/#dictdef-currentuserdetailsoptions).
   1623 ///
   1624 /// This can be sent to _an already authenticated user_ to inform the user information.
   1625 /// This can be useful when a user updates their user information on the RP's side but does not do so on the authenticator.
   1626 /// When the client forwards this response to the authenticator, it can update the user info for the associated credential.
   1627 #[derive(Debug)]
   1628 pub struct CurrentUserDetailsOptions<'rp_id, 'name, 'display_name, 'id, const LEN: usize> {
   1629     /// [`rpId`](https://www.w3.org/TR/webauthn-3/#dictdef-currentuserdetailsoptions-rpid).
   1630     pub rp_id: &'rp_id RpId,
   1631     /// [`userId`](https://www.w3.org/TR/webauthn-3/#dictdef-currentuserdetailsoptions-userid),
   1632     /// [`name`](https://www.w3.org/TR/webauthn-3/#dictdef-currentuserdetailsoptions-name), and
   1633     /// [`displayName`](https://www.w3.org/TR/webauthn-3/#dictdef-currentuserdetailsoptions-displayname).
   1634     pub user: PublicKeyCredentialUserEntity<'name, 'display_name, 'id, LEN>,
   1635 }
   1636 /// [`hmac-secret`](https://fidoalliance.org/specs/fido-v2.2-rd-20230321/fido-client-to-authenticator-protocol-v2.2-rd-20230321.html#sctn-hmac-secret-extension)
   1637 /// during authentication and
   1638 /// [`hmac-secret-mc`](https://fidoalliance.org/specs/fido-v2.2-ps-20250228/fido-client-to-authenticator-protocol-v2.2-ps-20250228.html#sctn-hmac-secret-make-cred-extension)
   1639 /// during registration.
   1640 ///
   1641 /// `REG` iff `hmac-secret-mc`.
   1642 enum HmacSecretGet<const REG: bool> {
   1643     /// No `hmac-secret` response.
   1644     None,
   1645     /// One encrypted `hmac-secret`.
   1646     One,
   1647     /// Two encrypted `hmac-secret`s.
   1648     Two,
   1649 }
   1650 /// Error returned by [`HmacSecretGet::from_cbor`]
   1651 enum HmacSecretGetErr {
   1652     /// Error related to the length of the CBOR input.
   1653     Len,
   1654     /// Error related to the type of the CBOR key.
   1655     Type,
   1656     /// Error related to the value of the CBOR value.
   1657     Value,
   1658 }
   1659 impl<const REG: bool> FromCbor<'_> for HmacSecretGet<REG> {
   1660     type Err = HmacSecretGetErr;
   1661     fn from_cbor(cbor: &[u8]) -> Result<CborSuccess<'_, Self>, Self::Err> {
   1662         /// AES block size.
   1663         const AES_BLOCK_SIZE: usize = 16;
   1664         /// HMAC-SHA-256 output length.
   1665         const HMAC_SHA_256_LEN: usize = 32;
   1666         /// Length of two HMAC-SHA-256 outputs concatenated together.
   1667         const TWO_HMAC_SHA_256_LEN: usize = HMAC_SHA_256_LEN << 1;
   1668         // We need the smallest multiple of `AES_BLOCK_SIZE` that
   1669         // is strictly greater than `HMAC_SHA_256_LEN`.
   1670         /// AES-256 output length on a 32-byte input.
   1671         #[expect(
   1672             clippy::integer_division_remainder_used,
   1673             reason = "doesn't need to be constant time"
   1674         )]
   1675         const ONE_SECRET_LEN: usize =
   1676             HMAC_SHA_256_LEN + (AES_BLOCK_SIZE - (HMAC_SHA_256_LEN % AES_BLOCK_SIZE));
   1677         // We need the smallest multiple of `AES_BLOCK_SIZE` that
   1678         // is strictly greater than `TWO_HMAC_SHA_256_LEN`.
   1679         /// AES-256 output length on a 64-byte input.
   1680         #[expect(
   1681             clippy::integer_division_remainder_used,
   1682             reason = "doesn't need to be constant time"
   1683         )]
   1684         const TWO_SECRET_LEN: usize =
   1685             TWO_HMAC_SHA_256_LEN + (AES_BLOCK_SIZE - (TWO_HMAC_SHA_256_LEN % AES_BLOCK_SIZE));
   1686         /// `hmac-secret-mc`.
   1687         ///
   1688         /// This is the key iff `REG`.
   1689         const KEY: [u8; 15] = [
   1690             cbor::TEXT_14,
   1691             b'h',
   1692             b'm',
   1693             b'a',
   1694             b'c',
   1695             b'-',
   1696             b's',
   1697             b'e',
   1698             b'c',
   1699             b'r',
   1700             b'e',
   1701             b't',
   1702             b'-',
   1703             b'm',
   1704             b'c',
   1705         ];
   1706         /// Helper that unifies `HmacSecretGet`.
   1707         enum CborVal<'a> {
   1708             /// Extension does not exist with remaining payload
   1709             Success,
   1710             /// Extension exists with remaining payload.
   1711             Continue(&'a [u8]),
   1712         }
   1713         if REG {
   1714             cbor.split_at_checked(KEY.len()).map_or(
   1715                 Ok(CborVal::Success),
   1716                 |(key, key_rem)| {
   1717                     if key == KEY {
   1718                         Ok(CborVal::Continue(key_rem))
   1719                     } else {
   1720                         Ok(CborVal::Success)
   1721                     }
   1722                 }
   1723             )
   1724         } else {
   1725             cbor.split_at_checked(cbor::HMAC_SECRET.len()).map_or(
   1726                 Ok(CborVal::Success),
   1727                 |(key, key_rem)| {
   1728                     if key == cbor::HMAC_SECRET {
   1729                         Ok(CborVal::Continue(key_rem))
   1730                     } else {
   1731                         Ok(CborVal::Success)
   1732                     }
   1733                 }
   1734             )
   1735         }.and_then(|cbor_val| {
   1736             match cbor_val {
   1737                 CborVal::Success => Ok(CborSuccess { value: Self::None, remaining: cbor, }),
   1738                 CborVal::Continue(key_rem) => {
   1739                     key_rem
   1740                         .split_first()
   1741                         .ok_or(HmacSecretGetErr::Len)
   1742                         .and_then(|(bytes, bytes_rem)| {
   1743                             if *bytes == cbor::BYTES_INFO_24 {
   1744                                 bytes_rem
   1745                                     .split_first()
   1746                                     .ok_or(HmacSecretGetErr::Len)
   1747                                     .and_then(|(&len, len_rem)| {
   1748                                         len_rem.split_at_checked(usize::from(len)).ok_or(HmacSecretGetErr::Len).and_then(|(_, remaining)| {
   1749                                             match usize::from(len) {
   1750                                                 ONE_SECRET_LEN => {
   1751                                                     Ok(CborSuccess {
   1752                                                         value: Self::One,
   1753                                                         remaining,
   1754                                                     })
   1755                                                 }
   1756                                                 TWO_SECRET_LEN => {
   1757                                                     Ok(CborSuccess {
   1758                                                         value: Self::Two,
   1759                                                         remaining,
   1760                                                     })
   1761                                                 }
   1762                                                 _ => Err(HmacSecretGetErr::Value),
   1763                                             }
   1764                                         })
   1765                                     })
   1766                             } else {
   1767                                 Err(HmacSecretGetErr::Type)
   1768                             }
   1769                         })
   1770                 }
   1771             }
   1772         })
   1773     }
   1774 }
	webauthn_rp WebAuthn Level 3 RP library.
	git clone https://git.philomathiclife.com/repos/webauthn_rp
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