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Commit | Line | Data |
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e0df8241 JR |
1 | """The match_hostname() function from Python 3.3.3, essential when using SSL.""" |
2 | ||
3 | # Note: This file is under the PSF license as the code comes from the python | |
4 | # stdlib. http://docs.python.org/3/license.html | |
5 | ||
6 | import re | |
7 | import sys | |
8 | ||
9 | # ipaddress has been backported to 2.6+ in pypi. If it is installed on the | |
10 | # system, use it to handle IPAddress ServerAltnames (this was added in | |
11 | # python-3.5) otherwise only do DNS matching. This allows | |
12 | # util.ssl_match_hostname to continue to be used in Python 2.7. | |
13 | try: | |
14 | import ipaddress | |
15 | except ImportError: | |
16 | ipaddress = None | |
17 | ||
18 | __version__ = "3.5.0.1" | |
19 | ||
20 | ||
21 | class CertificateError(ValueError): | |
22 | pass | |
23 | ||
24 | ||
25 | def _dnsname_match(dn, hostname, max_wildcards=1): | |
26 | """Matching according to RFC 6125, section 6.4.3 | |
27 | ||
28 | http://tools.ietf.org/html/rfc6125#section-6.4.3 | |
29 | """ | |
30 | pats = [] | |
31 | if not dn: | |
32 | return False | |
33 | ||
34 | # Ported from python3-syntax: | |
35 | # leftmost, *remainder = dn.split(r'.') | |
36 | parts = dn.split(r".") | |
37 | leftmost = parts[0] | |
38 | remainder = parts[1:] | |
39 | ||
40 | wildcards = leftmost.count("*") | |
41 | if wildcards > max_wildcards: | |
42 | # Issue #17980: avoid denials of service by refusing more | |
43 | # than one wildcard per fragment. A survey of established | |
44 | # policy among SSL implementations showed it to be a | |
45 | # reasonable choice. | |
46 | raise CertificateError( | |
47 | "too many wildcards in certificate DNS name: " + repr(dn) | |
48 | ) | |
49 | ||
50 | # speed up common case w/o wildcards | |
51 | if not wildcards: | |
52 | return dn.lower() == hostname.lower() | |
53 | ||
54 | # RFC 6125, section 6.4.3, subitem 1. | |
55 | # The client SHOULD NOT attempt to match a presented identifier in which | |
56 | # the wildcard character comprises a label other than the left-most label. | |
57 | if leftmost == "*": | |
58 | # When '*' is a fragment by itself, it matches a non-empty dotless | |
59 | # fragment. | |
60 | pats.append("[^.]+") | |
61 | elif leftmost.startswith("xn--") or hostname.startswith("xn--"): | |
62 | # RFC 6125, section 6.4.3, subitem 3. | |
63 | # The client SHOULD NOT attempt to match a presented identifier | |
64 | # where the wildcard character is embedded within an A-label or | |
65 | # U-label of an internationalized domain name. | |
66 | pats.append(re.escape(leftmost)) | |
67 | else: | |
68 | # Otherwise, '*' matches any dotless string, e.g. www* | |
69 | pats.append(re.escape(leftmost).replace(r"\*", "[^.]*")) | |
70 | ||
71 | # add the remaining fragments, ignore any wildcards | |
72 | for frag in remainder: | |
73 | pats.append(re.escape(frag)) | |
74 | ||
75 | pat = re.compile(r"\A" + r"\.".join(pats) + r"\Z", re.IGNORECASE) | |
76 | return pat.match(hostname) | |
77 | ||
78 | ||
79 | def _to_unicode(obj): | |
80 | if isinstance(obj, str) and sys.version_info < (3,): | |
81 | # ignored flake8 # F821 to support python 2.7 function | |
82 | obj = unicode(obj, encoding="ascii", errors="strict") # noqa: F821 | |
83 | return obj | |
84 | ||
85 | ||
86 | def _ipaddress_match(ipname, host_ip): | |
87 | """Exact matching of IP addresses. | |
88 | ||
89 | RFC 6125 explicitly doesn't define an algorithm for this | |
90 | (section 1.7.2 - "Out of Scope"). | |
91 | """ | |
92 | # OpenSSL may add a trailing newline to a subjectAltName's IP address | |
93 | # Divergence from upstream: ipaddress can't handle byte str | |
94 | ip = ipaddress.ip_address(_to_unicode(ipname).rstrip()) | |
95 | return ip == host_ip | |
96 | ||
97 | ||
98 | def match_hostname(cert, hostname): | |
99 | """Verify that *cert* (in decoded format as returned by | |
100 | SSLSocket.getpeercert()) matches the *hostname*. RFC 2818 and RFC 6125 | |
101 | rules are followed, but IP addresses are not accepted for *hostname*. | |
102 | ||
103 | CertificateError is raised on failure. On success, the function | |
104 | returns nothing. | |
105 | """ | |
106 | if not cert: | |
107 | raise ValueError( | |
108 | "empty or no certificate, match_hostname needs a " | |
109 | "SSL socket or SSL context with either " | |
110 | "CERT_OPTIONAL or CERT_REQUIRED" | |
111 | ) | |
112 | try: | |
113 | # Divergence from upstream: ipaddress can't handle byte str | |
114 | host_ip = ipaddress.ip_address(_to_unicode(hostname)) | |
115 | except (UnicodeError, ValueError): | |
116 | # ValueError: Not an IP address (common case) | |
117 | # UnicodeError: Divergence from upstream: Have to deal with ipaddress not taking | |
118 | # byte strings. addresses should be all ascii, so we consider it not | |
119 | # an ipaddress in this case | |
120 | host_ip = None | |
121 | except AttributeError: | |
122 | # Divergence from upstream: Make ipaddress library optional | |
123 | if ipaddress is None: | |
124 | host_ip = None | |
125 | else: # Defensive | |
126 | raise | |
127 | dnsnames = [] | |
128 | san = cert.get("subjectAltName", ()) | |
129 | for key, value in san: | |
130 | if key == "DNS": | |
131 | if host_ip is None and _dnsname_match(value, hostname): | |
132 | return | |
133 | dnsnames.append(value) | |
134 | elif key == "IP Address": | |
135 | if host_ip is not None and _ipaddress_match(value, host_ip): | |
136 | return | |
137 | dnsnames.append(value) | |
138 | if not dnsnames: | |
139 | # The subject is only checked when there is no dNSName entry | |
140 | # in subjectAltName | |
141 | for sub in cert.get("subject", ()): | |
142 | for key, value in sub: | |
143 | # XXX according to RFC 2818, the most specific Common Name | |
144 | # must be used. | |
145 | if key == "commonName": | |
146 | if _dnsname_match(value, hostname): | |
147 | return | |
148 | dnsnames.append(value) | |
149 | if len(dnsnames) > 1: | |
150 | raise CertificateError( | |
151 | "hostname %r " | |
152 | "doesn't match either of %s" % (hostname, ", ".join(map(repr, dnsnames))) | |
153 | ) | |
154 | elif len(dnsnames) == 1: | |
155 | raise CertificateError("hostname %r doesn't match %r" % (hostname, dnsnames[0])) | |
156 | else: | |
157 | raise CertificateError( | |
158 | "no appropriate commonName or subjectAltName fields were found" | |
159 | ) |