public static bool Verify(byte[] emailData, Signature signature)
{
string emailDatastr = Encoding.ASCII.GetString(emailData, 0, emailData.Length);
string header = emailDatastr.Substring(0, emailDatastr.IndexOf("\r\n\r\n"));
header = Parser.Unfold(header);
header = SelectFieldsAndCanonicalize(header, signature);
string body = emailDatastr.Substring(Regex.Match(emailDatastr, @"(?<=\r?\n\r?\n).").Index - 1);
System.IO.StringReader sr = new System.IO.StringReader(body);
StringBuilder sb = new StringBuilder();
while (sr.Peek() != -1)
{
sb.Append(string.Concat(Canonicalizer.Canonicalize(sr.ReadLine(), signature.CanonicalizationAlgorithm), Tokenizer.NewLine));
}
byte[] canonicalized = Encoding.ASCII.GetBytes(header + sb.ToString().TrimEnd('\r', '\n') + "\r\n");
SHA1Managed sha = new SHA1Managed();
byte[] hash = sha.ComputeHash(canonicalized);
PublicKeyRecord record = signature.GetPublicKeyRecord();
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
RSAParameters rsap = new RSAParameters();
FillRSAPublicKeyParameters(record.KeyData, ref rsap);
rsa.ImportParameters(rsap);
RSAPKCS1SignatureDeformatter RSADeformatter = new RSAPKCS1SignatureDeformatter(rsa);
RSADeformatter.SetHashAlgorithm("SHA1");
return(RSADeformatter.VerifySignature(hash, signature.Data));
}
private static string SelectFieldsAndCanonicalize(string header, Signature signature)
{
// Make a lowercase version for easy IndoxOf.
string headerLower = header.ToLower();
// We will only review the portion of the header after (before, in time) the signature.
int start = headerLower.IndexOf("\ndomainkey-signature");
header = header.Substring(start);
StringBuilder sb = new StringBuilder();
// Unfold.
header = Parser.Unfold(header);
// Build a list of header lines.
string[] lines = Regex.Split(header, "\r?\n");
// Do we have to take specific headers or all headers ?
if (signature.SignedHeaders.Length > 0)
{
// There are specific headers. For each field name in the signature, loop through the lines and append found occurences.
foreach (string str in signature.SignedHeaders)
{
foreach (string line in lines)
{
if (line.ToLower().StartsWith(str))
{
sb.Append(string.Concat(Canonicalizer.Canonicalize(line, signature.CanonicalizationAlgorithm), Tokenizer.NewLine));
}
}
}
}
else
{
// We take all headers subsequent to the signature field.
bool firstPassed = false;
foreach (string line in lines)
{
if (!firstPassed)
{
firstPassed = true;
continue;
}
else
{
sb.Append(string.Concat(line, Tokenizer.NewLine));
}
}
}
return(sb.ToString().TrimEnd('\r', '\n') + "\r\n");
}
