Question

I am trying to see if I can get the python-gnupg module working to sign and verify a file using a python script. I have the following code, which does not interpret any errors when called.

However the code prints “unverified” at the end, when I thought that I had signed the file (example.txt).

I must be missing something in the documentation but after I read it this is what I came up with for signing and verifying. Any help please?

import gnupg

gpg = gnupg.GPG(gnupghome="/home/myname") 

stream = open("example.txt", "rb")

signed_data = gpg.sign_file(stream)

verified = gpg.verify_file(stream)

print "Verified" if verified else "Unverified"

Answer 1

There are a few issues with your code,

1.) gpg = gnupg.GPG(gnupghome="/home/myname") needs to be gpg = gnupg.GPG(gnupghome="/home/myname/.gnupg")

2.) You are attempting to verify the stream, using verify_file(stream), however the stream is still a handle to the original, unsigned file. You would first need to either write the signed data to a new file and call verify_file() against a handle to that file, or verify the result sign_file.

Below is a working example of your demo, using the result of sign_file – but before we get to that, the way to troubleshoot what is happening in your script, you can review the output of stderr on the returned object of the gnupg methods. for example, you can review the result of the signed data by printing out signed_data.stderr. Likewise for return of the verify_file method.

On to the code –

import gnupg

gpg = gnupg.GPG(gnupghome="/home/myname/.gnupg")

stream = open("example.txt", "rb")

signed_data = gpg.sign_file(stream)

verified = gpg.verify(signed_data.data)

print "Verified" if verified else "Unverified"

I hope this helps!