Base64 alternative for X.509 certificates

Those X.509 functions which require you to pass the filename of an X.509 certificate will accept a base64 string representation of the certificate instead. This is the base64 string that can be obtained using the X509_ReadStringFromFile function. The first character in such a string should always be an "M".

You can also pass a string containing the certificate in PEM format. See PEM string alternative below for more details.

The example below shows how each of the filename, the base64 string, or the PEM-format string can be used in a typical X.509 function.

Dim nRet As Long
Dim strCertFileOrB64String As String
Dim strHexHash As String

' Compute the SHA-1 `thumbprint' of an X.509 certificate in two forms
strHexHash = String(PKI_SHA1_CHARS, " ")

' Refer to file itself...
strCertFileOrB64String = "smallca.cer"
nRet = X509_CertThumb(strCertFileOrB64String, strHexHash, Len(strHexHash), 0)
Debug.Print "X509_CertThumb returns " & nRet & " for '" & strCertFileOrB64String & "'"
Debug.Print "SHA-1 thumbprint=" & strHexHash

' Use base64 string representation directly...
strCertFileOrB64String = _
    "MIHgMIGaAgEBMA0GCSqGSIb3DQEBBQUAMAwxCjAIBgNVBAMTAUEwHhcNMDcwODAyMDIwMDAxWhc" _
    & "NMTEwODAyMDIwMDAxWjAMMQowCAYDVQQDEwFBMEowDQYJKoZIhvcNAQEBBQADOQAwNgIxA1KS" _
    & "JlPSmQAqQgDHUISaUsCrHbIZe249i6jFtfN3rA7czrP4CXS3mjvMFf0AsxV6BwIBAzANBgkqh" _
    & "kiG9w0BAQUFAAMyAACeT7GtgmBRKUN20cIyNEGneEvmNxaliuBEVkg2npbyEBgeHXOH6jqj9Ase348UN/Q="
nRet = X509_CertThumb(strCertFileOrB64String, strHexHash, Len(strHexHash), 0)
Debug.Print "X509_CertThumb returns " & nRet & " for '" & strCertFileOrB64String & "'"
Debug.Print "SHA-1 thumbprint=" & strHexHash

' Again using a PEM-style string...
strCertFileOrB64String = _
    "-----BEGIN CERTIFICATE-----" & vbCrLf _
    & "MIHgMIGaAgEBMA0GCSqGSIb3DQEBBQUAMAwxCjAIBgNVBAMTAUEwHhcNMDcwODAyMDIwMDAxWhc" & vbCrLf _
    & "NMTEwODAyMDIwMDAxWjAMMQowCAYDVQQDEwFBMEowDQYJKoZIhvcNAQEBBQADOQAwNgIxA1KS" & vbCrLf _
    & "JlPSmQAqQgDHUISaUsCrHbIZe249i6jFtfN3rA7czrP4CXS3mjvMFf0AsxV6BwIBAzANBgkqh" & vbCrLf _
    & "kiG9w0BAQUFAAMyAACeT7GtgmBRKUN20cIyNEGneEvmNxaliuBEVkg2npbyEBgeHXOH6jqj9Ase348UN/Q=" & vbCrLf _
    & "-----END CERTIFICATE-----"
nRet = X509_CertThumb(strCertFileOrB64String, strHexHash, Len(strHexHash), 0)
Debug.Print "X509_CertThumb returns " & nRet & " for '" & strCertFileOrB64String & "'"
Debug.Print "SHA-1 thumbprint=" & strHexHash

[As of v3.5, the vbCrLf CRLF characters are no longer required in the PEM-style string]

X509_CertThumb returns 40 for 'smallca.cer'
SHA-1 thumbprint=a36b1bfa0af41a2785066b2d5135b67011ac3b7f
X509_CertThumb returns 40 for 'MIHgMIGaAgEBMA0GCSq...(snip)...HXOH6jqj9Ase348UN/Q='
SHA-1 thumbprint=a36b1bfa0af41a2785066b2d5135b67011ac3b7f
X509_CertThumb returns 40 for '-----BEGIN CERTIFICATE-----
MIHgMIGaAgEBMA...(snip)...BgeHXOH6jqj9Ase348UN/Q=
-----END CERTIFICATE-----'
SHA-1 thumbprint=a36b1bfa0af41a2785066b2d5135b67011ac3b7f

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