Xbase++

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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LOCAL nSuccess
LOCAL oMime
LOCAL n
LOCAL oCert
LOCAL i

nSuccess := 0

oMime := CreateObject("Chilkat.Mime")
nSuccess := oMime:LoadMimeFile("qa_data/signed.eml")
IF (nSuccess == 0)
    ? oMime:LastErrorText
    oMime:destroy()
    RETURN
ENDIF

//  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.
nSuccess := oMime:Verify()
IF (nSuccess != 1)
    ? oMime:LastErrorText
    oMime:destroy()
    RETURN
ENDIF

n := oMime:NumSignerCerts
oCert := CreateObject("Chilkat.Cert")

FOR i := 0 TO n - 1
    nSuccess := oMime:LastSignerCert(i, oCert)
    IF (nSuccess == 0)
        ? oMime:LastErrorText
        oMime:destroy()
        oCert:destroy()
        RETURN
    ENDIF

    ? "Signer " + Str(i) + ": " + oCert:SubjectCN + " (issued by " + oCert:IssuerCN + ")"
NEXT

oMime:destroy()
oCert:destroy()