Re: [Botan-devel] How can extract public key from x509Cert

[Jack L. <ll...@ac...>]

On Sun, 20 Jul 2003, Marcus Meyer wrote:

> Hallo,

> I have a list of many X509Cert. The X509Cert Object can successful read
> the certificate und show me the infos (subject_dn issure_dn ...). The
> Problem is, it can not extract the public key object from the
> certificate.

That is bad.

> Botan::X509_PublicKey* key( Botan::X509::load_key("test.cert") );
> rise the exeption "X.509 public key decoding failed"

This will always fail, because the certificate has a bunch of other things
besides the public key, but load_key doesn't know that.

> the same exeption is come when I use the
> X509Certificate.subject_public_key().

This should not happen.

> I can extract the publickey with "openssl x509 -in cert -pubkey
> then i can create my X509Pubkey object.
>
> Have anybody a idea how i can do this  without using openssl?

The following program reads the public key from your sample certificate
just fine (at least with 1.2.4, which is the only version I have built on
this machine). What it prints matches what I get from running
'openssl x509 -in somecert.pem -pubkey -noout'

---- CUT ----
#include <botan/x509cert.h>
using namespace Botan;

#include <iostream>

int main()
   {
   LibraryInitializer init;

   try {
      X509_Certificate cert("somecert.pem");
      X509_PublicKey* key = cert.subject_public_key();
      std::cout << X509::PEM_encode(*key);
   }
   catch(std::exception& e)
      {
      std::cout << e.what() << std::endl;
      }
   return 0;
   }
---- CUT ----

-Jack