Hi,

Loads of Google searches and lots of reading have not led me to the desired result.

I have data that was signed by someone else. I also have the signature and I have a certificate. I want to verify in Perl that the data has not been fiddled with.

In Python this works for me as follows: 
from M2Crypto import X509

def verify_data(data, signature, cert):
    rawsig = signature..decode('base64') 

    x509 = X509.load_cert_string(cert)
    pubkey = x509.get_pubkey()
    pubkey.reset_context(md='sha256')
    pubkey.verify_init()
    pubkey.verify_update(data)
    return pubkey.verify_final(rawsig)

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How would I do this in Perl?

All the X509 things I have found appear to have options to deal with the certificate itself, but I haven't found the next step, i.e. 

my $x509 = Crypt::OpenSSL::X509->new_from_file('cert.pm');
my $pubkey = $x509->pubkey();
my $signature = read_file('signature.txt' , binmode => ':raw' );
my $data =  read_file('data.txt' , binmode => ':raw' );

[download]
But what happens next, as in Python I'd now like to call some methods that verify the signature and data against the public key....

The openssl dgst command does not handle a cert and extracting the public key didn't lead to the desired result: 

openssl x509 -in cert.pem -pubkey >& pubkey.txt
openssl dgst -sha256 -verify pubkey.txt -signature signature.txt myDat
+a.txt

[download]
The verification with openssl fails, but it should be valid and is valid with the Python code above. Help is much appreciated.

In reply to Verify signed data by rjschwei

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