VBScript

Decrypt S/MIME using a PFX File

Loads a CMS/PKCS #7 encrypted S/MIME message and decrypts it back to the original MIME content.

DecryptUsingPfxFile decrypts using the certificates and private keys contained in a PFX/P12 file, identified by path and password.

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 PFX/P12 file bundles a certificate with its private key. DecryptUsingPfxFile opens the file, locates the key matching the encrypted message, and recovers the original MIME.

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VBScript

Dim fso, outFile
Set fso = CreateObject("Scripting.FileSystemObject")
'Create a Unicode (utf-16) output text file.
Set outFile = fso.CreateTextFile("output.txt", True, True)

success = 0

set mime = CreateObject("Chilkat.Mime")
success = mime.LoadMimeFile("qa_data/encrypted.eml")
If (success = 0) Then
    outFile.WriteLine(mime.LastErrorText)
    WScript.Quit
End If

'  Decrypt using the certificates and private keys in a PFX/P12 file.  The 1st argument is the PFX
'  path and the 2nd is its password (which should come from a secure source).
pfxPassword = "myPfxPassword"
success = mime.DecryptUsingPfxFile("qa_data/recipient.pfx",pfxPassword)
If (success = 0) Then
    outFile.WriteLine(mime.LastErrorText)
    WScript.Quit
End If

body = mime.GetBodyDecoded()
If (mime.LastMethodSuccess = 0) Then
    outFile.WriteLine(mime.LastErrorText)
    WScript.Quit
End If

outFile.WriteLine(body)

outFile.Close