Visual FoxPro

Check if an Email Was Received Digitally Signed

Demonstrates the read-only Chilkat Email.ReceivedSigned property, which is true if the email was originally received carrying one or more digital signatures. Knowing a message was signed is separate from knowing the signature checked out, so this example also reads SignaturesValid to report whether the signed content verified.

Background: A digital signature on an email (S/MIME) provides two things: authenticity (it was really sent by the holder of a particular certificate) and integrity (the content was not altered in transit). The sender signs a hash of the message with their private key; the recipient verifies it with the sender's public certificate. ReceivedSigned simply tells you a signature is present — verifying it is a separate step exposed through SignaturesValid.

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Visual FoxPro

LOCAL lnSuccess
LOCAL loEmail

lnSuccess = 0

*  Demonstrates the read-only Email.ReceivedSigned property, which is true if this
*  email was originally received with a digital signature.  Use SignaturesValid to
*  determine whether the signed content actually verified.

loEmail = CreateObject('Chilkat.Email')

lnSuccess = loEmail.LoadEml("qa_data/eml/signed.eml")
IF (lnSuccess = 0) THEN
    ? loEmail.LastErrorText
    RELEASE loEmail
    CANCEL
ENDIF

IF (loEmail.ReceivedSigned = 1) THEN
    ? "This email was received with a digital signature."
    IF (loEmail.SignaturesValid = 1) THEN
        ? "All signatures are valid."
    ELSE
        ? "One or more signatures are NOT valid."
    ENDIF

ELSE
    ? "This email was not signed."
ENDIF

*  Note: Paths such as "qa_data/..." are relative local filesystem paths,
*  relative to the current working directory of the running application.

RELEASE loEmail