--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/urllib3/util/ssl_match_hostname.py	Sun May 05 23:32:17 2024 -0400
@@ -0,0 +1,159 @@
+"""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")