(Visual FoxPro) Decrypt S/MIME and Verify S/MIME Signatures

Visual FoxPro example to decrypt S/MIME and verify S/MIME signatures. The S/MIME is unwrapped to get the original MIME prior to signing/encrypting.

Note: This example requires Chilkat v11.0.0 or greater.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL lnSuccess
LOCAL loMime
LOCAL lnIsEncrypted
LOCAL lnIsSigned
LOCAL loSignerCert
LOCAL loDecryptCert

lnSuccess = 0

* This example requires the Chilkat API to have been previously unlocked.
* See Global Unlock Sample for sample code.

loMime = CreateObject('Chilkat.Mime')

* Load an S/MIME message from a file:
lnSuccess = loMime.LoadMimeFile("signedMime.txt")
IF (lnSuccess = 0) THEN
    ? loMime.LastErrorText
    RELEASE loMime
    CANCEL
ENDIF

* The ContainsEncryptedParts/ContainsSignedParts methods
* can be called to determine if the MIME is encrypted and/or signed:
lnIsEncrypted = loMime.ContainsEncryptedParts()
lnIsSigned = loMime.ContainsSignedParts()

* We don't want the "unwrap extras".  You'll see what those
* are in a few moments...
loMime.UnwrapExtras = 0

* To verify the signature, call UnwrapSecurity.  This will
* verify the signature(s) and decrypt the S/MIME and restore
* the MIME to the unsigned/unencrypted state.
* The results of what was found are present in the MIME object's
* properties, as well as extra header fields that are added
* to the unwrapped MIME.
lnSuccess = loMime.UnwrapSecurity()
IF (lnSuccess <> 1) THEN
    * UnwrapSecurity returns 1 if all signatures were
    * verified and all parts decrypted.
    ? loMime.LastErrorText
    RELEASE loMime
    CANCEL
ENDIF

* The mime.UnwrapExtras property controls whether or not
* these additional fields are added to the unwrapped MIME:
* 
* X-NumPartsSigned: 1
* X-SignaturesValid: yes
* X-NumPartsEncrypted: 1
* X-Decrypted: no
* 
* The X-NumPartsSigned/X-SignaturesValid headers are added
* if the MIME was signed.  
* 
* The X-NumPartsEncrypted/X-Decrypted headers are added
* if the MIME was encrypted.
* 

* If the MIME was signed, get the certificate used for signing.
IF (lnIsSigned = 1) THEN
    loSignerCert = CreateObject('Chilkat.Cert')

    * The NumSignerCerts property indicates how many certificates
    * were used for signing.  This example will assume the value is 1.
    * To get the 1st signer cert, call LastSignerCert with an index of 0:
    lnSuccess = loMime.LastSignerCert(0,loSignerCert)
    IF (lnSuccess = 1) THEN
        ? "**** Signer Cert: " + loSignerCert.SubjectCN
    ENDIF

ENDIF

* If the MIME was encrypted, get the certificate used for decryption
IF (lnIsEncrypted = 1) THEN
    * The NumDecryptCerts property indicates how many certificates
    * were used for decrypting.  This example will assume the value is 1.
    * To get the 1st decrypt cert, call LastDecryptCert with an index of 0:
    loDecryptCert = CreateObject('Chilkat.Cert')
    lnSuccess = loMime.LastDecryptCert(0,loDecryptCert)
    IF (lnSuccess = 1) THEN
        ? "**** Decrypt Cert: " + loDecryptCert.SubjectCN
    ENDIF

ENDIF

* Display the unwrapped MIME:
? loMime.GetMime()

* Save the unwrapped MIME to a file:
lnSuccess = loMime.SaveMime("unwrappedMime.txt")

RELEASE loMime
RELEASE loSignerCert
RELEASE loDecryptCert