• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1#!/usr/bin/env python3
2#
3# fetch the certificate that the server(s) are providing in PEM form
4#
5# args are HOST:PORT [, HOST:PORT...]
6#
7# By Bill Janssen.
8
9import re
10import os
11import sys
12import tempfile
13
14
15def fetch_server_certificate (host, port):
16
17    def subproc(cmd):
18        from subprocess import Popen, PIPE, STDOUT
19        proc = Popen(cmd, stdout=PIPE, stderr=STDOUT, shell=True)
20        status = proc.wait()
21        output = proc.stdout.read()
22        return status, output
23
24    def strip_to_x509_cert(certfile_contents, outfile=None):
25        m = re.search(br"^([-]+BEGIN CERTIFICATE[-]+[\r]*\n"
26                      br".*[\r]*^[-]+END CERTIFICATE[-]+)$",
27                      certfile_contents, re.MULTILINE | re.DOTALL)
28        if not m:
29            return None
30        else:
31            tn = tempfile.mktemp()
32            with open(tn, "wb") as fp:
33                fp.write(m.group(1) + b"\n")
34            try:
35                tn2 = (outfile or tempfile.mktemp())
36                status, output = subproc(r'openssl x509 -in "%s" -out "%s"' %
37                                         (tn, tn2))
38                if status != 0:
39                    raise RuntimeError('OpenSSL x509 failed with status %s and '
40                                       'output: %r' % (status, output))
41                with open(tn2, 'rb') as fp:
42                    data = fp.read()
43                os.unlink(tn2)
44                return data
45            finally:
46                os.unlink(tn)
47
48    if sys.platform.startswith("win"):
49        tfile = tempfile.mktemp()
50        with open(tfile, "w") as fp:
51            fp.write("quit\n")
52        try:
53            status, output = subproc(
54                'openssl s_client -connect "%s:%s" -showcerts < "%s"' %
55                (host, port, tfile))
56        finally:
57            os.unlink(tfile)
58    else:
59        status, output = subproc(
60            'openssl s_client -connect "%s:%s" -showcerts < /dev/null' %
61            (host, port))
62    if status != 0:
63        raise RuntimeError('OpenSSL connect failed with status %s and '
64                           'output: %r' % (status, output))
65    certtext = strip_to_x509_cert(output)
66    if not certtext:
67        raise ValueError("Invalid response received from server at %s:%s" %
68                         (host, port))
69    return certtext
70
71
72if __name__ == "__main__":
73    if len(sys.argv) < 2:
74        sys.stderr.write(
75            "Usage:  %s HOSTNAME:PORTNUMBER [, HOSTNAME:PORTNUMBER...]\n" %
76            sys.argv[0])
77        sys.exit(1)
78    for arg in sys.argv[1:]:
79        host, port = arg.split(":")
80        sys.stdout.buffer.write(fetch_server_certificate(host, int(port)))
81    sys.exit(0)
82