Visual FoxPro

Get Recipient Certificate Info from Encrypted S/MIME

Demonstrates GetDecryptCertInfo, which examines an encrypted S/MIME entity and writes the recipient-certificate identifiers into a JsonObject. This reveals which certificate(s) the message was encrypted for, so the correct private key can be located before decrypting.

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.

Tip: Code to parse the returned JSON can be generated with Chilkat's online tool at https://tools.chilkat.io/jsonParse.

Background. A CMS/PKCS #7 encrypted message carries recipient identifiers (such as issuer and serial number). Inspecting them lets an application determine, without decrypting, which key it needs.

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Visual FoxPro

LOCAL lnSuccess
LOCAL loMime
LOCAL loCertInfo
LOCAL lcJson

lnSuccess = 0

loMime = CreateObject('Chilkat.Mime')
lnSuccess = loMime.LoadMimeFile("qa_data/encrypted.eml")
IF (lnSuccess = 0) THEN
    ? loMime.LastErrorText
    RELEASE loMime
    CANCEL
ENDIF

*  Examine the encrypted entity and write the recipient-certificate identifiers to a JsonObject.
*  This tells you which certificate(s) the message was encrypted for, so you can locate the right
*  private key before attempting to decrypt.
loCertInfo = CreateObject('Chilkat.JsonObject')
lnSuccess = loMime.GetDecryptCertInfo(loCertInfo)
IF (lnSuccess = 0) THEN
    ? loMime.LastErrorText
    RELEASE loMime
    RELEASE loCertInfo
    CANCEL
ENDIF

loCertInfo.EmitCompact = 0
lcJson = loCertInfo.Emit()
? lcJson
*  JSON parsing code for this result can be generated at Chilkat's online tool:
*  https://tools.chilkat.io/jsonParse

RELEASE loMime
RELEASE loCertInfo