(Xojo Plugin) Extract PKCS7 Signature Digest

Demonstrates how to extract a signature digest from a PKCS7 signature.

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

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

Dim crypt As New Chilkat.Crypt2

Dim p7mFile As String
p7mFile = "qa_data/p7m/test.pdf.p7m"
Dim outPath As String
outPath = "qa_output/test.pdf"

// First let's see if this .p7m signature can be verified, and the original file extracted.
Dim verified As Boolean
verified = crypt.VerifyP7M(p7mFile,outPath)
If (verified <> True) Then
    System.DebugLog(crypt.LastErrorText)
    Return
End If

// How many signers?
// (The NumSignerCerts property is set whenever a signature is verified.)
System.DebugLog("Num Signers: " + Str(crypt.NumSignerCerts))

// Load the .p7m into memory...
Dim pkcs7Data As New Chilkat.BinData
Dim success As Boolean
success = pkcs7Data.LoadFile(p7mFile)

// Check to see if this .p7m contains the binary bytes, or if it's
// already base64 encoded.  Get the 1st two bytes.  If the first two 
// bytes are the us-ascii values "MI", then we have base64.
Dim sbBase64 As New Chilkat.StringBuilder
Dim hexStr As String
hexStr = pkcs7Data.GetEncodedChunk(0,2,"hex")
success = sbBase64.Append(hexStr)

Dim bHaveBase64 As Boolean
bHaveBase64 = False
If (sbBase64.ContentsEqual("4D49",True) = True) Then
    bHaveBase64 = True
    sbBase64.Clear 
    success = sbBase64.AppendBd(pkcs7Data,"utf-8",0,0)
End If

// Get each signer's signature digest.
crypt.EncodingMode = "base64"
Dim i As Int32
i = 0
Dim digest As String
While i < crypt.NumSignerCerts
    If (bHaveBase64) Then
        digest = crypt.Pkcs7ExtractDigest(i,sbBase64.GetAsString())
    Else
        digest = crypt.Pkcs7ExtractDigest(i,pkcs7Data.GetEncoded("base64"))
    End If

    If (crypt.LastMethodSuccess <> True) Then
        System.DebugLog(crypt.LastErrorText)
        Return
    End If

    System.DebugLog("Signer " + Str(i + 1) + " digest = " + digest)
    i = i + 1
Wend