Delphi ActiveX

Get the S/MIME Signer's Certificate

Demonstrates the Chilkat Mime.LastSignerCert method, which loads the signer certificate at a zero-based index from the most recent successful verification (or security-unwrapping) into a Cert. The first argument is the signer index and the second is the receiving Cert.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: Verifying tells you the signature is mathematically valid, but you usually also need to know who signed — the subject, the issuer, the validity dates — to decide whether to trust it. This retrieves each signer's certificate after verification so your code can inspect and apply its own trust rules. A message can have multiple signers, so iterate from 0 to NumSignerCerts - 1.

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var
success: Integer;
mime: TChilkatMime;
n: Integer;
cert: TChilkatCert;
i: Integer;

begin
success := 0;

mime := TChilkatMime.Create(Self);
success := mime.LoadMimeFile('qa_data/signed.eml');
if (success = 0) then
  begin
    Memo1.Lines.Add(mime.LastErrorText);
    Exit;
  end;

//  After a successful verification, load each signer's certificate to inspect it.  The 1st argument
//  is the zero-based signer index and the 2nd is a Cert object that receives the certificate.
success := mime.Verify();
if (success <> 1) then
  begin
    Memo1.Lines.Add(mime.LastErrorText);
    Exit;
  end;

n := mime.NumSignerCerts;
cert := TChilkatCert.Create(Self);

for i := 0 to n - 1 do
  begin
    success := mime.LastSignerCert(i,cert.ControlInterface);
    if (success = 0) then
      begin
        Memo1.Lines.Add(mime.LastErrorText);
        Exit;
      end;
    Memo1.Lines.Add('Signer ' + IntToStr(i) + ': ' + cert.SubjectCN + ' (issued by ' + cert.IssuerCN + ')');
  end;