CkPython

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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import sys
import chilkat

success = False

mime = chilkat.CkMime()
success = mime.LoadMimeFile("qa_data/signed.eml")
if (success == False):
    print(mime.lastErrorText())
    sys.exit()

#  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 != True):
    print(mime.lastErrorText())
    sys.exit()

n = mime.get_NumSignerCerts()
cert = chilkat.CkCert()

for i in range(0,n):
    success = mime.LastSignerCert(i,cert)
    if (success == False):
        print(mime.lastErrorText())
        sys.exit()

    print("Signer " + str(i) + ": " + cert.subjectCN() + " (issued by " + cert.issuerCN() + ")")