I'm unable to verify a PSS-signed signature in Perl using Crypt::RSA and Crypt::RSA::SS::PSS.
Here's the situation:

I have a device that has a 1024-bit RSA key, and signs data using PSS, SHA1 and AES-128.

I extract the device's public key successfully, save it in a file with PEM_write_RSA_PUBKEY()

I am able to verify this in C/C++ using RSA_verify_PKCS1_PSS(), and also using openssl on the command line, like this:

echo -n hello | 
openssl dgst -verify pubkey.pem -signature hello.sig -sha1 \
             -sigopt rsa_padding_mode:pss -sigopt rsa_pss_saltlen:20
[download]

Where:

• The string "hello" is the buffer that's been signed by the device.
• "pubkey.pem" is the device's RSA Public Key, exported from the device with PEM_write_RSA_PUBKEY().
• "hello.sig" contains the binary (raw) signature generated by the device. (It's 128 bytes, because of the padding.)

I'm trying to do the above in Perl, using Crypt::RSA and Crypt::RSA::SS::PSS, and can't get it to work.

I've tested those two modules and I *am* able to generate and verify a PSS signature in Perl when generating my own key, like this:

####
use Crypt::RSA;
use Crypt::RSA::SS::PSS;

my ($message, $rsa, $pss, $signature, $verify);
my ($public, $private);


# The message to be encrypted
#
$message = "hello";


# Generate RSA key
#
$rsa = new Crypt::RSA;
($public, $private) = $rsa->keygen( Size => 1024,
                                    Filename => "key" );


# Generate PSS signature
#
$pss = new Crypt::RSA::SS::PSS;

$signature = $pss->sign ( Message => $message,
                          Key => $private ) || die $pss->errstr;

$verify = $pss->verify ( Message => $message,
                         Key => $public,
                         Signature => $signature) || die $pss->errstr;


# $verify returns true, it worked.
####
[download]

So, instead of creating my own RSA key I read in a public key using something like this:

####

$publicKey = new Crypt::RSA::Key::Public (Filename => "key.public");
       ….
# I pack the 256 character (128 byte) hex string of the signature
# that's generated by the device.

$signature = pack ("H*", '03808458…..73E92');   

####
[download]

Where "key.public" contains the device's public key, converted to a decimal string, inserted into the "n" field of the structure that is read/written by Crypt::RSA::Key::Public.

But I can't get it to verify :-(

Methinks I should be able to indicate that it should be using SHA1 and AES-128 (as opposed to, say, Blowfish). Am I barking up the wrong tree?

Thanks….

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