tests/readlink.py

sslutil: fall back to commonName when no dNSName in subjectAltName (issue2798)

Any entries in subjectAltName would prevent fallback to using commonName, but
RFC 2818 says:

    If a subjectAltName extension of type dNSName is present, that MUST
    be used as the identity. Otherwise, the (most specific) Common Name
    field in the Subject field of the certificate MUST be used.

We now only consider dNSNames in subjectAltName.

(dNSName is known as 'DNS' in OpenSSL/Python.)

#!/usr/bin/env python

import errno, os, sys

for f in sys.argv[1:]:
    try:
        print f, '->', os.readlink(f)
    except OSError, err:
        if err.errno != errno.EINVAL:
            raise
        print f, 'not a symlink'

sys.exit(0)