service-identity 0.1

Service identity verification for pyOpenSSL.

WARNING

This software is currently pre-alpha and under review. Use it at your own peril.

Any part is subject to change, but feedback is very welcome!

Pitch

service_identity aspires to give you all the tools you need for verifying whether the certificates of servers you connect to are valid for the intended purposes.

In the simplest case, this means host name verification. However, service_identity implements RFC 6125 fully and plans to add relevant other RFCs too.

Features

Present

• dNSName with fallback to CN (DNS-ID, aka host names, RFC 6125).

• uniformResourceIdentifier (URI-ID, RFC 6125).

• SRV-ID (RFC 6125)

Future

• xmppAddr (RFC 3920).

• iPAddress (RFC 2818).

• name constrains extensions (RFC 3280).

Usage

Verify a Hostname

The simplest, most common, and most important usage:

from __future__ import absolute_import, division, print_function

import socket

from OpenSSL import SSL
from service_identity import verify_hostname, VerificationError


ctx = SSL.Context(SSL.SSLv23_METHOD)
ctx.set_verify(SSL.VERIFY_PEER, lambda conn, cert, errno, depth, ok: ok)
ctx.set_default_verify_paths()

hostname = u"twistedmatrix.com"
sock = SSL.Connection(ctx, socket.socket(socket.AF_INET, socket.SOCK_STREAM))
sock.connect((hostname, 443))

try:
    sock.do_handshake()
    verify_hostname(sock.get_peer_certificate(), hostname)
    # Do your super-secure stuff here.
except SSL.Error as e:
    print("TLS Handshake failed: {0!r}.".format(e.args[0]))
except VerificationError:
    print("Presented certificate is not valid for {0}.".format(hostname))
finally:
    sock.shutdown()
    sock.close()

Requirements

Python 2.6, 2.7, 3.2, and 3.3 as well as PyPy are supported.

Additionally, the following PyPI modules are required:

• pyOpenSSL >= 0.12 (0.14 strongly suggested)

• pyasn1

• pyasn1-modules

Optionally, idna can be used for internationalized domain names (IDN), aka non-ASCII domains. Please note, that idna is not available for Python 3.2 and is required because Python’s stdlib support is outdated.