// internal for testing
internal static async Task <Payload> ValidateInternalAsync(string jwt, ValidationSettings validationSettings)
{
var settings = validationSettings.ThrowIfNull(nameof(validationSettings)).Clone();
var verificationOptions = validationSettings.ToVerificationOptions();
var signedToken = SignedToken <Header, Payload> .FromSignedToken(jwt);
// Start general validation task ...
var generalValidationTask = SignedTokenVerification.VerifySignedTokenAsync(signedToken, verificationOptions, default);
// ... and do Google specific validation in the meantime.
// Google signed tokens must not exceed this length.
// It's not clear if there's an absolute size limit for all possible tokens,
// that's why this check is only here and not on SignedTokenVerification.
if (jwt.Length > MaxJwtLength)
{
throw new InvalidJwtException($"JWT exceeds maximum allowed length of {MaxJwtLength}");
}
// Google signed tokens are signed with RS256.
if (signedToken.Header.Algorithm != SupportedJwtAlgorithm)
{
throw new InvalidJwtException($"JWT algorithm must be '{SupportedJwtAlgorithm}'");
}
// Google signed tokens can contain a G Suite hosted domain claim.
if (settings.HostedDomain != null && signedToken.Payload.HostedDomain != settings.HostedDomain)
{
throw new InvalidJwtException("JWT contains invalid 'hd' claim.");
}
// ... finally wait for the general verifications to be done.
await generalValidationTask.ConfigureAwait(false);
// All verification passed, return payload.
return(signedToken.Payload);
}
/// <summary>
/// Verifies that the given token is a valid, not expired, signed token.
/// </summary>
/// <param name="signedJwt">The token to verify.</param>
/// <param name="options">The options to use for verification.
/// May be null in which case default options will be used.</param>
/// <param name="cancellationToken">The cancellation token for the operation.</param>
/// <returns>The payload contained by the token.</returns>
/// <exception cref="InvalidJwtException">If the token is invalid or expired.</exception>
public async static Task <Payload> VerifySignedTokenAsync(
string signedJwt, SignedTokenVerificationOptions options = null, CancellationToken cancellationToken = default)
{
var signedToken = SignedToken <Header, Payload> .FromSignedToken(signedJwt);
await SignedTokenVerification.VerifySignedTokenAsync(signedToken, options, cancellationToken).ConfigureAwait(false);
return(signedToken.Payload);
}
internal async static Task VerifySignedTokenAsync <TJswHeader, TJswPayload>(
SignedToken <TJswHeader, TJswPayload> signedToken, SignedTokenVerificationOptions options, CancellationToken cancellationToken)
where TJswHeader : Header
where TJswPayload : Payload
{
signedToken.ThrowIfNull(nameof(signedToken));
options = options == null ? new SignedTokenVerificationOptions() : new SignedTokenVerificationOptions(options);
options.CertificateCache ??= s_certificateCache;
// Start the signature validation task...
Task signatureVerificationTask = signedToken.Header.Algorithm switch
{
"RS256" => VerifyRS256TokenAsync(signedToken, options, cancellationToken),
#if ES256_SUPPORTED
"ES256" => VerifyES256TokenAsync(signedToken, options, cancellationToken),
#else
"ES256" => throw new InvalidOperationException("ES256 signed token verification is not supported in this platform."),
#endif
_ => throw new InvalidJwtException("Signing algorithm must be either RS256 or ES256.")
};
// ... let's validate everything else while we wait for signature validation...
// The signed token issuer should be one of the trusted issuers.
if (options.TrustedIssuers.Count > 0 && !options.TrustedIssuers.Contains(signedToken.Payload.Issuer))
{
var validList = string.Join(", ", options.TrustedIssuers.Select(x => $"'{x}'"));
throw new InvalidJwtException($"JWT issuer incorrect. Must be one of: {validList}");
}
// All audiences on the signed token should be trusted audiences.
if (options.TrustedAudiences.Count > 0 && signedToken.Payload.AudienceAsList.Except(options.TrustedAudiences).Any())
{
throw new InvalidJwtException("JWT contains untrusted 'aud' claim.");
}
// Issued at and expiration are present. Save them for time related validity checks.
DateTimeOffset issuedAt = signedToken.Payload.IssuedAt ?? throw new InvalidJwtException("JWT must contain 'iat' and 'exp' claims");
DateTimeOffset expiresAt = signedToken.Payload.ExpiresAt ?? throw new InvalidJwtException("JWT must contain 'iat' and 'exp' claims");
// Check that the token was issued in the past.
var utcNow = options.Clock.UtcNow;
if (utcNow + options.IssuedAtClockTolerance < issuedAt)
{
throw new InvalidJwtException("JWT is not yet valid.");
}
// Check that the token is not yet expired.
if (utcNow - options.ExpiryClockTolerance > expiresAt)
{
throw new InvalidJwtException("JWT has expired.");
}
// ... and finally let's wait for signature validation to be done.
await signatureVerificationTask.ConfigureAwait(false);
}
private async static Task VerifyES256TokenAsync <TJswHeader, TJswPayload>(
SignedToken <TJswHeader, TJswPayload> signedToken, SignedTokenVerificationOptions options, CancellationToken cancellationToken)
where TJswHeader : Header
where TJswPayload : Payload
{
var certificates = await GetCertificatesAsync(
options, GoogleAuthConsts.IapKeySetUrl, FromKeyToECDsa, cancellationToken).ConfigureAwait(false);
foreach (ECDsa certificate in certificates)
{
if (certificate.VerifyHash(signedToken.Sha256Hash, signedToken.Signature))
{
return;
}
}
throw new InvalidJwtException("JWT invalid, unable to verify signature.");
private async static Task VerifyRS256TokenAsync <TJswHeader, TJswPayload>(
SignedToken <TJswHeader, TJswPayload> signedToken, SignedTokenVerificationOptions options, CancellationToken cancellationToken)
where TJswHeader : Header
where TJswPayload : Payload
{
var certificates = await GetCertificatesAsync(
options, GoogleAuthConsts.JsonWebKeySetUrl, FromKeyToRsa, cancellationToken).ConfigureAwait(false);
foreach (RSA certificate in certificates)
{
#if NET45
if (((RSACryptoServiceProvider)certificate).VerifyHash(signedToken.Sha256Hash, Sha256Oid, signedToken.Signature))
#elif NETSTANDARD1_3 || NETSTANDARD2_0 || NET461
if (certificate.VerifyHash(signedToken.Sha256Hash, signedToken.Signature, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1))
#else
#error Unsupported platform
#endif
{
return;
}
}
throw new InvalidJwtException("JWT invalid, unable to verify signature.");
