[PM-5731] feat: implement credential assertion in client

src/Core/Services/Fido2AuthenticatorService.cs

@@ -192,7 +192,7 @@ namespace Bit.Core.Services
 
                 var signature = GenerateSignature(
                     authData: authenticatorData,
-                    clientDataHash: assertionParams.ClientDataHash,
+                    clientDataHash: assertionParams.Hash,
                     privateKey: selectedFido2Credential.KeyBytes
                 );
 

src/Core/Services/Fido2ClientService.cs

@@ -18,8 +18,7 @@ namespace Bit.Core.Services
             IStateService stateService,
             IEnvironmentService environmentService,
             ICryptoFunctionService cryptoFunctionService,
-            IFido2AuthenticatorService fido2AuthenticatorService
-        )
+            IFido2AuthenticatorService fido2AuthenticatorService)
         {
             _stateService = stateService;
             _environmentService = environmentService;
@@ -133,7 +132,74 @@ namespace Bit.Core.Services
             }
         }
 
-        public Task<Fido2ClientAssertCredentialResult> AssertCredentialAsync(Fido2ClientAssertCredentialParams assertCredentialParams) => throw new NotImplementedException();
+        public async Task<Fido2ClientAssertCredentialResult> AssertCredentialAsync(Fido2ClientAssertCredentialParams assertCredentialParams)
+        {
+            var blockedUris = await _stateService.GetAutofillBlacklistedUrisAsync();
+            var domain = CoreHelpers.GetHostname(assertCredentialParams.Origin);
+            if (blockedUris.Contains(domain))
+            {
+                throw new Fido2ClientException(
+                    Fido2ClientException.ErrorCode.UriBlockedError,
+                    "Origin is blocked by the user");
+            }
+
+            if (!await _stateService.IsAuthenticatedAsync())
+            {
+                throw new Fido2ClientException(
+                    Fido2ClientException.ErrorCode.InvalidStateError,
+                    "No user is logged in");
+            }
+
+            if (assertCredentialParams.Origin == _environmentService.GetWebVaultUrl())
+            {
+                throw new Fido2ClientException(
+                    Fido2ClientException.ErrorCode.NotAllowedError,
+                    "Saving Bitwarden credentials in a Bitwarden vault is not allowed");
+            }
+
+            if (!assertCredentialParams.Origin.StartsWith("https://"))
+            {
+                throw new Fido2ClientException(
+                    Fido2ClientException.ErrorCode.SecurityError,
+                    "Origin is not a valid https origin");
+            }
+
+            if (!Fido2DomainUtils.IsValidRpId(assertCredentialParams.RpId, assertCredentialParams.Origin))
+            {
+                throw new Fido2ClientException(
+                    Fido2ClientException.ErrorCode.SecurityError,
+                    "RP ID cannot be used with this origin");
+            }
+
+            var clientDataJSON = JsonSerializer.Serialize(new {
+                type = "webauthn.get",
+                challenge = CoreHelpers.Base64UrlEncode(assertCredentialParams.Challenge),
+                origin = assertCredentialParams.Origin,
+                crossOrigin = !assertCredentialParams.SameOriginWithAncestors,
+            });
+            var clientDataJSONBytes = Encoding.UTF8.GetBytes(clientDataJSON);
+            var clientDataHash = await _cryptoFunctionService.HashAsync(clientDataJSONBytes, CryptoHashAlgorithm.Sha256);
+            var getAssertionParams = MapToGetAssertionParams(assertCredentialParams, clientDataHash);
+
+            try {
+                var getAssertionResult = await _fido2AuthenticatorService.GetAssertionAsync(getAssertionParams);
+
+                return new Fido2ClientAssertCredentialResult {
+                    AuthenticatorData = getAssertionResult.AuthenticatorData,
+                    ClientDataJSON = clientDataJSONBytes,
+                    Id = CoreHelpers.Base64UrlEncode(getAssertionResult.SelectedCredential.Id),
+                    RawId = getAssertionResult.SelectedCredential.Id,
+                    Signature = getAssertionResult.Signature,
+                    UserHandle = getAssertionResult.SelectedCredential.UserHandle
+                };
+            } catch (InvalidStateError) {
+                throw new Fido2ClientException(Fido2ClientException.ErrorCode.InvalidStateError, "Unknown invalid state encountered");
+            } catch (Exception) {
+                throw new Fido2ClientException(Fido2ClientException.ErrorCode.UnknownError, $"An unknown error occurred");
+            }
+
+            throw new NotImplementedException();
+        }
 
         private Fido2AuthenticatorMakeCredentialParams MapToMakeCredentialParams(
             Fido2ClientCreateCredentialParams createCredentialParams,
@@ -160,5 +226,23 @@ namespace Bit.Core.Services
                 Extensions = createCredentialParams.Extensions
             };
         }
+
+        private Fido2AuthenticatorGetAssertionParams MapToGetAssertionParams(
+            Fido2ClientAssertCredentialParams assertCredentialParams,
+            byte[] cliendDataHash)
+        {
+            var requireUserVerification = assertCredentialParams.UserVerification == "required" ||
+                assertCredentialParams.UserVerification == "preferred" ||
+                assertCredentialParams.UserVerification == null;
+
+            return new Fido2AuthenticatorGetAssertionParams {
+                RpId = assertCredentialParams.RpId,
+                Challenge = assertCredentialParams.Challenge,
+                AllowCredentialDescriptorList = assertCredentialParams.AllowCredentials,
+                RequireUserPresence = true,
+                RequireUserVerification = requireUserVerification,
+                Hash = cliendDataHash
+            };
+        }
     }
 }

src/Core/Utilities/Fido2/Fido2AuthenticatorGetAssertionParams.cs

@@ -6,7 +6,7 @@
         public string RpId { get; set; }
 
         /** The hash of the serialized client data, provided by the client. */
-        public byte[] ClientDataHash { get; set; }
+        public byte[] Hash { get; set; }
 
         public PublicKeyCredentialDescriptor[] AllowCredentialDescriptorList { get; set; }
 
@@ -20,6 +20,11 @@
         /// </summary>
         public bool RequireUserPresence { get; set; }
 
+        /// <summary>
+        /// The challenge to be signed by the authenticator.
+        /// </summary>
+        public byte[] Challenge { get; set; }
+
         public object Extensions { get; set; }
     }
 }

src/Core/Utilities/Fido2/Fido2ClientAssertCredentialParams.cs

@@ -11,7 +11,13 @@ namespace Bit.Core.Utilities.Fido2
     public class Fido2ClientAssertCredentialParams
     {
         /// <summary>
-        /// S challenge that the selected authenticator signs, along with other data, when producing an authentication
+        /// A value which is true if and only if the caller’s environment settings object is same-origin with its ancestors.
+        /// It is false if caller is cross-origin.
+        /// </summary>
+        public bool SameOriginWithAncestors { get; set; }
+
+        /// <summary>
+        /// The challenge that the selected authenticator signs, along with other data, when producing an authentication
         /// assertion. 
         /// </summary>
         public required byte[] Challenge { get; set; }

src/Core/Utilities/Fido2/Fido2ClientAssertCredentialResult.cs

@@ -16,5 +16,27 @@ namespace Bit.Core.Utilities.Fido2
         /// The credential identifier.
         /// </summary>
         public required byte[] RawId { get; set; }
+
+        /// <summary>
+        /// The JSON-compatible serialization of client datapassed to the authenticator by the client in
+        /// order to generate this assertion.
+        /// </summary>
+        public required byte[] ClientDataJSON { get; set; }
+
+        /// <summary>
+        /// The authenticator data returned by the authenticator.
+        /// </summary>
+        public required byte[] AuthenticatorData { get; set; }
+
+        /// <summary>
+        /// The raw signature returned from the authenticator.
+        /// </summary>
+        public required byte[] Signature { get; set; }
+
+        /// <summary>
+        /// The user handle returned from the authenticator, or null if the authenticator did not
+        /// return a user handle.
+        /// </summary>
+        public byte[]? UserHandle { get; set; }
     }
 }

src/Core/Utilities/Fido2/Fido2ClientCreateCredentialParams.cs

@@ -12,7 +12,6 @@ namespace Bit.Core.Utilities.Fido2
         /// </summary>
         public required string Origin { get; set; }
 
-        // TODO: Check if we actually need this
         /// <summary>
         /// A value which is true if and only if the caller’s environment settings object is same-origin with its ancestors.
         /// It is false if caller is cross-origin.