(Xojo Plugin) Decrypt S/MIME and Verify S/MIME Signatures

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

Chilkat Xojo Plugin Download Xojo Plugin for Windows, Linux, Mac OS X, and ARM, ARM64

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

Dim mime As New Chilkat.Mime

// Load an S/MIME message from a file:
Dim success As Boolean
success = mime.LoadMimeFile("signedMime.txt")
If (success <> True) Then
    System.DebugLog(mime.LastErrorText)
    Return
End If

// The ContainsEncryptedParts/ContainsSignedParts methods
// can be called to determine if the MIME is encrypted and/or signed:
Dim isEncrypted As Boolean
isEncrypted = mime.ContainsEncryptedParts()
Dim isSigned As Boolean
isSigned = mime.ContainsSignedParts()

// We don't want the "unwrap extras".  You'll see what those
// are in a few moments...
mime.UnwrapExtras = False

// 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.
success = mime.UnwrapSecurity()
If (success <> True) Then
    // UnwrapSecurity returns True if all signatures were
    // verified and all parts decrypted.
    System.DebugLog(mime.LastErrorText)
    Return
End If

// 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 (isSigned = True) Then
    // 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 GetSignerCert with an index of 0:
    Dim signerCert As Chilkat.Cert
    signerCert = mime.GetSignerCert(0)
    If (mime.LastMethodSuccess = True) Then
        System.DebugLog("**** Signer Cert: " + signerCert.SubjectCN)

    End If

End If

// If the MIME was encrypted, get the certificate used for encryption:
If (isEncrypted = True) Then
    // The NumEncryptCerts property indicates how many certificates
    // were used for encrypting.  This example will assume the value is 1.
    // To get the 1st encrypt cert, call GetEncryptCert with an index of 0:
    Dim encryptCert As Chilkat.Cert
    encryptCert = mime.GetEncryptCert(0)
    If (mime.LastMethodSuccess = True) Then
        System.DebugLog("**** Encrypt Cert: " + encryptCert.SubjectCN)

    End If

End If

// Display the unwrapped MIME:
System.DebugLog(mime.GetMime())

// Save the unwrapped MIME to a file:
success = mime.SaveMime("unwrappedMime.txt")