/// <summary> /// Verify the signature of the message headers. /// </summary> /// <remarks> /// Verifies the signature of the message headers. /// </remarks> /// <param name="options">The formatting options.</param> /// <param name="message">The signed MIME message.</param> /// <param name="dkimSignature">The DKIM-Signature or ARC-Message-Signature header.</param> /// <param name="signatureAlgorithm">The algorithm used to sign the message headers.</param> /// <param name="key">The public key used to verify the signature.</param> /// <param name="headers">The list of headers that were signed.</param> /// <param name="canonicalizationAlgorithm">The algorithm used to canonicalize the headers.</param> /// <param name="signature">The expected signature of the headers encoded in base64.</param> /// <returns><c>true</c> if the calculated signature matches <paramref name="signature"/>; otherwise, <c>false</c>.</returns> protected bool VerifySignature(FormatOptions options, MimeMessage message, Header dkimSignature, DkimSignatureAlgorithm signatureAlgorithm, AsymmetricKeyParameter key, string[] headers, DkimCanonicalizationAlgorithm canonicalizationAlgorithm, string signature) { using (var stream = new DkimSignatureStream(CreateVerifyContext(signatureAlgorithm, key))) { using (var filtered = new FilteredStream(stream)) { filtered.Add(options.CreateNewLineFilter()); WriteHeaders(options, message, headers, canonicalizationAlgorithm, filtered); // now include the DKIM-Signature header that we are verifying, // but only after removing the "b=" signature value. var header = GetSignedSignatureHeader(dkimSignature); switch (canonicalizationAlgorithm) { case DkimCanonicalizationAlgorithm.Relaxed: WriteHeaderRelaxed(options, filtered, header, true); break; default: WriteHeaderSimple(options, filtered, header, true); break; } filtered.Flush(); } return(stream.VerifySignature(signature)); } }
async Task <bool> VerifyArcSealAsync(FormatOptions options, ArcHeaderSet[] sets, int i, bool doAsync, CancellationToken cancellationToken) { DkimSignatureAlgorithm algorithm; AsymmetricKeyParameter key; string d, s, q, b; ValidateArcSealParameters(sets[i].ArcSealParameters, out algorithm, out d, out s, out q, out b); if (!IsEnabled(algorithm)) { return(false); } if (doAsync) { key = await PublicKeyLocator.LocatePublicKeyAsync(q, d, s, cancellationToken).ConfigureAwait(false); } else { key = PublicKeyLocator.LocatePublicKey(q, d, s, cancellationToken); } if ((key is RsaKeyParameters rsa) && rsa.Modulus.BitLength < MinimumRsaKeyLength) { return(false); } options = options.Clone(); options.NewLineFormat = NewLineFormat.Dos; using (var stream = new DkimSignatureStream(CreateVerifyContext(algorithm, key))) { using (var filtered = new FilteredStream(stream)) { filtered.Add(options.CreateNewLineFilter()); for (int j = 0; j < i; j++) { WriteHeaderRelaxed(options, filtered, sets[j].ArcAuthenticationResult, false); WriteHeaderRelaxed(options, filtered, sets[j].ArcMessageSignature, false); WriteHeaderRelaxed(options, filtered, sets[j].ArcSeal, false); } WriteHeaderRelaxed(options, filtered, sets[i].ArcAuthenticationResult, false); WriteHeaderRelaxed(options, filtered, sets[i].ArcMessageSignature, false); // now include the ARC-Seal header that we are verifying, // but only after removing the "b=" signature value. var seal = GetSignedSignatureHeader(sets[i].ArcSeal); WriteHeaderRelaxed(options, filtered, seal, true); filtered.Flush(); } return(stream.VerifySignature(b)); } }
async Task <bool> VerifyAsync(FormatOptions options, MimeMessage message, Header dkimSignature, bool doAsync, CancellationToken cancellationToken) { if (options == null) { throw new ArgumentNullException(nameof(options)); } if (message == null) { throw new ArgumentNullException(nameof(message)); } if (dkimSignature == null) { throw new ArgumentNullException(nameof(dkimSignature)); } if (dkimSignature.Id != HeaderId.DkimSignature) { throw new ArgumentException("The signature parameter MUST be a DKIM-Signature header.", nameof(dkimSignature)); } var parameters = ParseParameterTags(dkimSignature.Id, dkimSignature.Value); DkimCanonicalizationAlgorithm headerAlgorithm, bodyAlgorithm; DkimSignatureAlgorithm signatureAlgorithm; AsymmetricKeyParameter key; string d, s, q, bh, b; string[] headers; int maxLength; ValidateDkimSignatureParameters(parameters, out signatureAlgorithm, out headerAlgorithm, out bodyAlgorithm, out d, out s, out q, out headers, out bh, out b, out maxLength); if (!IsEnabled(signatureAlgorithm)) { return(false); } if (doAsync) { key = await PublicKeyLocator.LocatePublicKeyAsync(q, d, s, cancellationToken).ConfigureAwait(false); } else { key = PublicKeyLocator.LocatePublicKey(q, d, s, cancellationToken); } if ((key is RsaKeyParameters rsa) && rsa.Modulus.BitLength < MinimumRsaKeyLength) { return(false); } options = options.Clone(); options.NewLineFormat = NewLineFormat.Dos; // first check the body hash (if that's invalid, then the entire signature is invalid) var hash = Convert.ToBase64String(message.HashBody(options, signatureAlgorithm, bodyAlgorithm, maxLength)); if (hash != bh) { return(false); } using (var stream = new DkimSignatureStream(CreateVerifyContext(signatureAlgorithm, key))) { using (var filtered = new FilteredStream(stream)) { filtered.Add(options.CreateNewLineFilter()); WriteHeaders(options, message, headers, headerAlgorithm, filtered); // now include the DKIM-Signature header that we are verifying, // but only after removing the "b=" signature value. var header = GetSignedSignatureHeader(dkimSignature); switch (headerAlgorithm) { case DkimCanonicalizationAlgorithm.Relaxed: WriteHeaderRelaxed(options, filtered, header, true); break; default: WriteHeaderSimple(options, filtered, header, true); break; } filtered.Flush(); } return(stream.VerifySignature(b)); } }
/// <summary> /// Verify the specified DKIM-Signature header. /// </summary> /// <remarks> /// Verifies the specified DKIM-Signature header. /// </remarks> /// <param name="options">The formatting options.</param> /// <param name="dkimSignature">The DKIM-Signature header.</param> /// <param name="publicKeyLocator">The public key locator service.</param> /// <param name="cancellationToken">The cancellation token.</param> /// <exception cref="System.ArgumentNullException"> /// <para><paramref name="options"/> is <c>null</c>.</para> /// <para>-or-</para> /// <para><paramref name="dkimSignature"/> is <c>null</c>.</para> /// <para>-or-</para> /// <para><paramref name="publicKeyLocator"/> is <c>null</c>.</para> /// </exception> /// <exception cref="System.ArgumentException"> /// <paramref name="dkimSignature"/> is not a DKIM-Signature header. /// </exception> /// <exception cref="System.FormatException"> /// The DKIM-Signature header value is malformed. /// </exception> /// <exception cref="System.OperationCanceledException"> /// The operation was canceled via the cancellation token. /// </exception> bool Verify (FormatOptions options, Header dkimSignature, IDkimPublicKeyLocator publicKeyLocator, CancellationToken cancellationToken = default (CancellationToken)) { if (options == null) throw new ArgumentNullException ("options"); if (dkimSignature == null) throw new ArgumentNullException ("dkimSignature"); if (dkimSignature.Id != HeaderId.DkimSignature) throw new ArgumentException ("The dkimSignature parameter MUST be a DKIM-Signature header.", "dkimSignature"); if (publicKeyLocator == null) throw new ArgumentNullException ("publicKeyLocator"); var parameters = ParseDkimSignature (dkimSignature.Value); DkimCanonicalizationAlgorithm headerAlgorithm, bodyAlgorithm; DkimSignatureAlgorithm signatureAlgorithm; AsymmetricKeyParameter key; string d, s, q, h, bh, b; int maxLength; ValidateDkimSignatureParameters (parameters, out signatureAlgorithm, out headerAlgorithm, out bodyAlgorithm, out d, out s, out q, out h, out bh, out b, out maxLength); key = publicKeyLocator.LocatePublicKey (q, d, s, cancellationToken); options = options.Clone (); options.NewLineFormat = NewLineFormat.Dos; // first check the body hash (if that's invalid, then the entire signature is invalid) var hash = Convert.ToBase64String (DkimHashBody (options, signatureAlgorithm, bodyAlgorithm, maxLength)); if (hash != bh) return false; using (var stream = new DkimSignatureStream (DkimGetDigestSigner (signatureAlgorithm, key))) { using (var filtered = new FilteredStream (stream)) { filtered.Add (options.CreateNewLineFilter ()); DkimWriteHeaders (options, h.Split (':'), headerAlgorithm, filtered); // now include the DKIM-Signature header that we are verifying, // but only after removing the "b=" signature value. var header = GetSignedDkimSignatureHeader (dkimSignature); switch (headerAlgorithm) { case DkimCanonicalizationAlgorithm.Relaxed: DkimWriteHeaderRelaxed (options, filtered, header); break; default: DkimWriteHeaderSimple (options, filtered, header); break; } filtered.Flush (); } return stream.VerifySignature (b); } }