CkPython

Check for an S/MIME Signing Time

Demonstrates the Chilkat Mime.HasSignatureSigningTime method, which returns whether the signer at a zero-based index included a CMS signingTime signed attribute. The only argument is the signer index; use NumSignerCerts for the count.

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: A signing time records when the signer claims to have signed, which matters for auditing and for validating a certificate that has since expired. It is an optional signed attribute, so not every signature has one — this predicate lets you check before calling GetSignatureSigningTimeStr, avoiding an error for signers that omitted it. Being a signed attribute, it is covered by the signature and cannot be altered undetected.

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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 verifying, check whether each signer included a CMS signingTime signed attribute.  The
#  only argument is the zero-based signer index.
success = mime.Verify()
if (success != True):
    print(mime.lastErrorText())
    sys.exit()

n = mime.get_NumSignerCerts()

for i in range(0,n):
    if (mime.HasSignatureSigningTime(i)):
        print("Signer " + str(i) + " included a signing time.")
    else:
        print("Signer " + str(i) + " did not include a signing time.")