(Perl) RSASSA-PSS Sign String to Create Base64 PCKS7 Signature

Signs a string to create a PKCS7 signature in the base64 encoding. The signature algorithm is RSASSA-PSS with SHA256.

Note: This example requires Chilkat v9.5.0.67 or greater.

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use chilkat();

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

$crypt = chilkat::CkCrypt2->new();

# Get a digital certificate with private key from a .pfx
# (Chilkat has many different ways to provide a cert + private key for siging.
# Using a PFX is just one possible option.)
$pfx = chilkat::CkPfx->new();
$success = $pfx->LoadPfxFile("qa_data/rsassa-pss/privatekey.pfx","PFX_PASSWORD");
if ($success != 1) {
    print $pfx->lastErrorText() . "\r\n";
    exit;
}

# Get the certificate to be used for signing.
# (The typical case for a PFX is that it contains a cert with an associated private key,
# as well as other certificates in the chain of authentication.  The cert with the private
# key should be in the first position at index 0.)
# cert is a Cert
$cert = $pfx->GetCert(0);
if ($pfx->get_LastMethodSuccess() != 1) {
    print $pfx->lastErrorText() . "\r\n";
    exit;
}

$crypt->SetSigningCert($cert);

# Indicate that RSASSA-PSS with SHA256 should be used.
$crypt->put_SigningAlg("pss");
$crypt->put_HashAlgorithm("sha256");

$crypt->put_EncodingMode("base64");

# Sign a string and return the base64 PKCS7 detached signature
$originalText = "This is a test";
$pkcs7sig = $crypt->signStringENC($originalText);
print "Detached Signature:" . "\r\n";
print $pkcs7sig . "\r\n";

# This signature looks like this:
# MIIG5wYJKoZIhvcNAQcCoIIG2DCCBtQCAQExDzANBgl .. YToLqEwTdU87ox5g7rvw==

# The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
# then copy-and-paste the Base64 signature into the form and decode..

# The signature can be verified against the original data like this:
$success = $crypt->VerifyStringENC($originalText,$pkcs7sig);
print "Signature verified: " . $success . "\r\n";
$success = $crypt->VerifyStringENC("Not the original text",$pkcs7sig);
print "Signature verified: " . $success . "\r\n";

# Now we'll create an opaque signature (the opposite of a detached signature). 
# An opaque signature is a PKCS7 message that contains both the original data and
# the signature.  The verification process extracts the original data.
$opaqueSig = $crypt->opaqueSignStringENC($originalText);
print "Opaque Signature:" . "\r\n";
print $opaqueSig . "\r\n";

# The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
# then copy-and-paste the Base64 signature into the form and decode..

# We can verify and extract the original data:
$origTxt = $crypt->opaqueVerifyStringENC($opaqueSig);
if ($crypt->get_LastMethodSuccess() != 1) {
    print "Signature verification failed." . "\r\n";
    print $crypt->lastErrorText() . "\r\n";

    exit;
}

print "Signature verified." . "\r\n";
print "Extracted text:" . $origTxt . "\r\n";