Viewing file:  ssl_match_hostname.py (5.68 KB) -rw-r--r--
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"""The match_hostname() function from Python 3.5, essential when using SSL."""
# Note: This file is under the PSF license as the code comes from the python
# stdlib. http://docs.python.org/3/license.html
# It is modified to remove commonName support.
from __future__ import annotations
import ipaddress
import re
import typing
from ipaddress import IPv4Address, IPv6Address
if typing.TYPE_CHECKING:
from .ssl_ import _TYPE_PEER_CERT_RET_DICT
__version__ = "3.5.0.1"
class CertificateError(ValueError):
pass
def _dnsname_match(
dn: typing.Any, hostname: str, max_wildcards: int = 1
) -> typing.Match[str] | None | bool:
"""Matching according to RFC 6125, section 6.4.3
http://tools.ietf.org/html/rfc6125#section-6.4.3
"""
pats = []
if not dn:
return False
# Ported from python3-syntax:
# leftmost, *remainder = dn.split(r'.')
parts = dn.split(r".")
leftmost = parts[0]
remainder = parts[1:]
wildcards = leftmost.count("*")
if wildcards > max_wildcards:
# Issue #17980: avoid denials of service by refusing more
# than one wildcard per fragment. A survey of established
# policy among SSL implementations showed it to be a
# reasonable choice.
raise CertificateError(
"too many wildcards in certificate DNS name: " + repr(dn)
)
# speed up common case w/o wildcards
if not wildcards:
return bool(dn.lower() == hostname.lower())
# RFC 6125, section 6.4.3, subitem 1.
# The client SHOULD NOT attempt to match a presented identifier in which
# the wildcard character comprises a label other than the left-most label.
if leftmost == "*":
# When '*' is a fragment by itself, it matches a non-empty dotless
# fragment.
pats.append("[^.]+")
elif leftmost.startswith("xn--") or hostname.startswith("xn--"):
# RFC 6125, section 6.4.3, subitem 3.
# The client SHOULD NOT attempt to match a presented identifier
# where the wildcard character is embedded within an A-label or
# U-label of an internationalized domain name.
pats.append(re.escape(leftmost))
else:
# Otherwise, '*' matches any dotless string, e.g. www*
pats.append(re.escape(leftmost).replace(r"\*", "[^.]*"))
# add the remaining fragments, ignore any wildcards
for frag in remainder:
pats.append(re.escape(frag))
pat = re.compile(r"\A" + r"\.".join(pats) + r"\Z", re.IGNORECASE)
return pat.match(hostname)
def _ipaddress_match(ipname: str, host_ip: IPv4Address | IPv6Address) -> bool:
"""Exact matching of IP addresses.
RFC 9110 section 4.3.5: "A reference identity of IP-ID contains the decoded
bytes of the IP address. An IP version 4 address is 4 octets, and an IP
version 6 address is 16 octets. [...] A reference identity of type IP-ID
matches if the address is identical to an iPAddress value of the
subjectAltName extension of the certificate."
"""
# OpenSSL may add a trailing newline to a subjectAltName's IP address
# Divergence from upstream: ipaddress can't handle byte str
ip = ipaddress.ip_address(ipname.rstrip())
return bool(ip.packed == host_ip.packed)
def match_hostname(
cert: _TYPE_PEER_CERT_RET_DICT | None,
hostname: str,
hostname_checks_common_name: bool = False,
) -> None:
"""Verify that *cert* (in decoded format as returned by
SSLSocket.getpeercert()) matches the *hostname*. RFC 2818 and RFC 6125
rules are followed, but IP addresses are not accepted for *hostname*.
CertificateError is raised on failure. On success, the function
returns nothing.
"""
if not cert:
raise ValueError(
"empty or no certificate, match_hostname needs a "
"SSL socket or SSL context with either "
"CERT_OPTIONAL or CERT_REQUIRED"
)
try:
# Divergence from upstream: ipaddress can't handle byte str
#
# The ipaddress module shipped with Python < 3.9 does not support
# scoped IPv6 addresses so we unconditionally strip the Zone IDs for
# now. Once we drop support for Python 3.9 we can remove this branch.
if "%" in hostname:
host_ip = ipaddress.ip_address(hostname[: hostname.rfind("%")])
else:
host_ip = ipaddress.ip_address(hostname)
except ValueError:
# Not an IP address (common case)
host_ip = None
dnsnames = []
san: tuple[tuple[str, str], ...] = cert.get("subjectAltName", ())
key: str
value: str
for key, value in san:
if key == "DNS":
if host_ip is None and _dnsname_match(value, hostname):
return
dnsnames.append(value)
elif key == "IP Address":
if host_ip is not None and _ipaddress_match(value, host_ip):
return
dnsnames.append(value)
# We only check 'commonName' if it's enabled and we're not verifying
# an IP address. IP addresses aren't valid within 'commonName'.
if hostname_checks_common_name and host_ip is None and not dnsnames:
for sub in cert.get("subject", ()):
for key, value in sub:
if key == "commonName":
if _dnsname_match(value, hostname):
return
dnsnames.append(value)
if len(dnsnames) > 1:
raise CertificateError(
"hostname %r "
"doesn't match either of %s" % (hostname, ", ".join(map(repr, dnsnames)))
)
elif len(dnsnames) == 1:
raise CertificateError(f"hostname {hostname!r} doesn't match {dnsnames[0]!r}")
else:
raise CertificateError("no appropriate subjectAltName fields were found")
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