pki: Add a common place to store raw signatures

This is a preparation to store the raw signature for all algorithms in
the same place in ssh_signature.

Signed-off-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>

src/pki.c

@@ -629,6 +629,9 @@ void ssh_signature_free(ssh_signature sig)
             break;
     }
 
+    /* Explicitly zero the signature content before free */
+    ssh_string_burn(sig->raw_sig);
+    ssh_string_free(sig->raw_sig);
     SAFE_FREE(sig);
 }