(Tcl) Verify an RSA Signature Against the Signed String

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Demonstrates how to validate an RSA Signature against the string that was signed.

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load ./chilkat.dll

# Create the same string we previously signed in this example: 
# RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

set sb [new_CkStringBuilder]

set crlfLineEnding 1

for {set i 0} {$i <= 10} {incr i} {
    CkStringBuilder_AppendLine $sb "This is a test." $crlfLineEnding
}

set base64_rsa_sig "gWgpEXQqvXN6wh0MuFXPiw2xCb8cnmdizBT1TD1Tpm2GlJ8gnD59DGSj35GGXk1tM+mCOvMa2uW/9gmz8p6A90JLbn918i/2wKGvcde4wXnzPO7JADSNn2UwYzf3rp4/q/JrHv1GZETRJhABSFqTxOgdmdbEJQE/zijOSctCtQAM2CTb6t2BO8uHKSSUAwPH2cbeWxqsaVRLT4ruk5nZOxhoLgLMSjupiSzbE8zSTkkFOEHD+Mbb2xwg85AI0E4DsUnp+hLwwtS0blesgSyvtBY8oJODJeFcJsR7JDOTPdzHQHgJRl/2A4ij5xT91TpXy7ok43jhT6O9j7Q3qrafIQ=="

# Get the public key to be used for signature verification.
set pubKey [new_CkPublicKey]

set success [CkPublicKey_LoadFromFile $pubKey "rsaKeys/chilkat-rsa-2048.pem"]
if {$success == 0} then {
    puts [CkPublicKey_lastErrorText $pubKey]
    delete_CkStringBuilder $sb
    delete_CkPublicKey $pubKey
    exit
}

set rsa [new_CkRsa]

CkRsa_ImportPublicKeyObj $rsa $pubKey

# Verify the string against the signature.
# We signed the utf-8 byte representation of the string, so we must indicate
# to also validate against the utf-8 byte representation.
CkRsa_put_Charset $rsa "utf-8"
CkRsa_put_EncodingMode $rsa "base64"
set signedString [CkStringBuilder_getAsString $sb]
set success [CkRsa_VerifyStringENC $rsa $signedString "sha256" $base64_rsa_sig]

if {$success == 0} then {
    puts [CkRsa_lastErrorText $rsa]
    puts "Signature invalid."
} else {
    puts "Signature valid."
}


delete_CkStringBuilder $sb
delete_CkPublicKey $pubKey
delete_CkRsa $rsa