public EmailHeader SignMessage(Email email)
{
// Find the actual headers we're going to sign
var headers = email.GetHeadersToSign(_headersToSign);
// Generate the header value
var value = this.GenerateDkimHeaderValue(email, headers);
// Add the signature key
headers.Add(new EmailHeader() { Key = SignatureKey, Value = value});
// sign email
value += GenerateSignature(email, headers);
// Return the new header
return new EmailHeader() { Key = SignatureKey, Value = value };
}
/*
* see http://www.dkim.org/specs/rfc4871-dkimbase.html#dkim-sig-hdr
*
* */
public string GenerateDkimHeaderValue(Email email, List<EmailHeader> headers)
{
// timestamp - seconds since 00:00:00 on January 1, 1970 UTC
TimeSpan t = DateTime.Now.ToUniversalTime() -
DateTime.SpecifyKind(DateTime.Parse("00:00:00 January 1, 1970"), DateTimeKind.Utc);
var signatureValue = new StringBuilder();
var start = /*Email.NewLine + */" ";
var end = ";";
//nl= string.Empty;
signatureValue.Append("v=1;");
// algorithm used
signatureValue.Append(start);
signatureValue.Append("a=");
signatureValue.Append(_privateKeySigner.Algorithm);
signatureValue.Append(end);
// Canonicalization
signatureValue.Append(start);
signatureValue.Append("c=");
signatureValue.Append(this.HeaderCanonicalization.ToString().ToLower());
signatureValue.Append('/');
signatureValue.Append(this.BodyCanonicalization.ToString().ToLower());
signatureValue.Append(end);
// signing domain
signatureValue.Append(start);
signatureValue.Append("d=");
signatureValue.Append(_domain);
signatureValue.Append(end);
// headers to be signed
signatureValue.Append(start);
signatureValue.Append("h=");
foreach (var header in headers)
{
signatureValue.Append(header.Key);
signatureValue.Append(':');
}
signatureValue.Length--;
signatureValue.Append(end);
// i=identity
// not supported
// l=body length
//not supported
// public key location
signatureValue.Append(start);
signatureValue.Append("q=dns/txt");
signatureValue.Append(end);
// selector
signatureValue.Append(start);
signatureValue.Append("s=");
signatureValue.Append(_selector);
signatureValue.Append(end);
// time sent
signatureValue.Append(start);
signatureValue.Append("t=");
signatureValue.Append((int)t.TotalSeconds);
signatureValue.Append(end);
// x=expiration
// not supported
// hash of body
signatureValue.Append(start);
signatureValue.Append("bh=");
signatureValue.Append(SignBody(email));
signatureValue.Append(end);
// x=copied header fields
// not supported
signatureValue.Append(start);
signatureValue.Append("b=");
return signatureValue.ToString();
}
/// <summary>
///
/// </summary>
/// <param name="email">The email to sign.</param>
/// <param name="signature"></param>
/// <returns></returns>
public string GenerateSignature(Email email, List<EmailHeader> headers)
{
var cheaders = DkimCanonicalizer.CanonicalizeHeaders(headers, this.HeaderCanonicalization);
return Convert.ToBase64String(_privateKeySigner.Sign(email.Encoding.GetBytes(cheaders)));
}
public string SignBody(Email email)
{
var cb = DkimCanonicalizer.CanonicalizeBody(email.Body, this.BodyCanonicalization);
return Convert.ToBase64String(_privateKeySigner.Hash(email.Encoding.GetBytes(cb)));
}
public static string Canonicalize(Email email, DomainKeyCanonicalizationAlgorithm algorithm, List<EmailHeader> headersToSign)
{
Func<String, string> process;
switch (algorithm)
{
case DomainKeyCanonicalizationAlgorithm.Simple:
{
process = x => x;
break;
}
case DomainKeyCanonicalizationAlgorithm.Nofws:
{
process = x => x.RemoveWhitespace();
break;
}
default:
{
throw new ArgumentException("Invalid canonicalization type.");
}
}
var headers = new StringBuilder();
foreach (var h in headersToSign)
{
headers.Append(process(h.Key));
headers.Append(':');
headers.Append(process(" " + h.Value));
headers.Append(Email.NewLine);
}
var body = new StringBuilder();
using (var reader = new StringReader(email.Body))
{
string line;
int emptyLines = 0;
// if only empty lines don't write until these is text after them
while ((line = reader.ReadLine()) != null)
{
if (line.Length == 0)
{
emptyLines++;
}
else
{
while (emptyLines > 0)
{
body.Append(Email.NewLine);
emptyLines--;
}
body.Append(process(line));
body.Append(Email.NewLine);
}
}
}
// If the body consists entirely of empty lines, then the header/body
// line is similarly ignored.
if (body.Length == 0)
{
return headers.ToString();
}
headers.Append(Email.NewLine);// header/body seperator line
headers.Append(body);
return headers.ToString();
}
public EmailHeader SignMessage(Email email)
{
var signatureValue = new StringBuilder();
// algorithm used
signatureValue.Append("a=");
signatureValue.Append(_privateKeySigner.Algorithm);
signatureValue.Append("; ");
// Canonicalization
signatureValue.Append("c=");
signatureValue.Append(this.Canonicalization.ToString().ToLower());
signatureValue.Append("; ");
// signing domain
signatureValue.Append("d=");
signatureValue.Append(_domain);
signatureValue.Append("; ");
// headers to be signed
var headers = email.GetHeadersToSign(_headersToSign);
if (headers.Count>0)
{
signatureValue.Append("h=");
foreach (var header in headers)
{
signatureValue.Append(header.Key);
signatureValue.Append(':');
}
signatureValue.Length--;
signatureValue.Append("; ");
}
// public key location
signatureValue.Append("q=dns; ");
// selector
signatureValue.Append("s=");
signatureValue.Append(_selector);
signatureValue.Append("; ");
// signature data
signatureValue.Append("b=");
signatureValue.Append(SignSignature(email, headers));
signatureValue.Append(";");
return new EmailHeader() { Key = SignatureKey, Value = signatureValue.ToString() };
}
public string SignSignature(Email email, List<EmailHeader> headers)
{
var text = DomainKeyCanonicalizer.Canonicalize(email, this.Canonicalization, headers);
return Convert.ToBase64String(_privateKeySigner.Sign(email.Encoding.GetBytes(text)));
}
void FinishCollecting()
{
if (m_CollectMode == CollectMode.None)
return;
var e = new Email()
{
Headers = m_collectedHeaders,
Body = m_collectedContent.ToString(),
Encoding = writer.Encoding
};
// Generate Dkim signature
if (DkimSigner != null)
{
m_collectedHeaders.Insert(0, DkimSigner.SignMessage(e));
}
// Generate domain keys signature
if (DomainKeysSigner != null)
{
m_collectedHeaders.Insert(0, DomainKeysSigner.SignMessage(e));
}
m_CollectMode = CollectMode.None;
// Write all headers
foreach (var h in m_collectedHeaders)
{
SendHeader(h.Key, h.Value);
}
// Write the separator
SendData(string.Empty);
// Write the content
SendData(e.Body);
}
public string SignSignature(Email email, List <EmailHeader> headers)
{
var text = DomainKeyCanonicalizer.Canonicalize(email, this.Canonicalization, headers);
return(Convert.ToBase64String(_privateKeySigner.Sign(email.Encoding.GetBytes(text))));
}
