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bpo-32107 - Improve MAC address calculation and fix test_uuid.py (#4600)
``uuid.getnode()`` now preferentially returns universally administered MAC addresses if available, over locally administered MAC addresses. This makes a better guarantee for global uniqueness of UUIDs returned from ``uuid.uuid1()``. If only locally administered MAC addresses are available, the first such one found is returned. Also improve internal code style by being explicit about ``return None`` rather than falling off the end of the function. Improve the test robustness.
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Barry Warsaw
GitHub
parent
71bd588646
commit
23df2d1304
4 changed files with 89 additions and 29 deletions
71
Lib/uuid.py
71
Lib/uuid.py
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@ -342,11 +342,30 @@ def _popen(command, *args):
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env=env)
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return proc
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# For MAC (a.k.a. IEEE 802, or EUI-48) addresses, the second least significant
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# bit of the first octet signifies whether the MAC address is universally (0)
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# or locally (1) administered. Network cards from hardware manufacturers will
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# always be universally administered to guarantee global uniqueness of the MAC
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# address, but any particular machine may have other interfaces which are
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# locally administered. An example of the latter is the bridge interface to
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# the Touch Bar on MacBook Pros.
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#
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# This bit works out to be the 42nd bit counting from 1 being the least
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# significant, or 1<<41. We'll prefer universally administered MAC addresses
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# over locally administered ones since the former are globally unique, but
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# we'll return the first of the latter found if that's all the machine has.
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#
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# See https://en.wikipedia.org/wiki/MAC_address#Universal_vs._local
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def _is_universal(mac):
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return not (mac & (1 << 41))
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def _find_mac(command, args, hw_identifiers, get_index):
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first_local_mac = None
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try:
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proc = _popen(command, *args.split())
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if not proc:
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return
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return None
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with proc:
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for line in proc.stdout:
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words = line.lower().rstrip().split()
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@ -355,8 +374,9 @@ def _find_mac(command, args, hw_identifiers, get_index):
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try:
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word = words[get_index(i)]
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mac = int(word.replace(b':', b''), 16)
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if mac:
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if _is_universal(mac):
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return mac
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first_local_mac = first_local_mac or mac
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except (ValueError, IndexError):
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# Virtual interfaces, such as those provided by
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# VPNs, do not have a colon-delimited MAC address
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@ -366,6 +386,7 @@ def _find_mac(command, args, hw_identifiers, get_index):
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pass
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except OSError:
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pass
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return first_local_mac or None
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def _ifconfig_getnode():
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"""Get the hardware address on Unix by running ifconfig."""
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@ -375,6 +396,7 @@ def _ifconfig_getnode():
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mac = _find_mac('ifconfig', args, keywords, lambda i: i+1)
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if mac:
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return mac
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return None
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def _ip_getnode():
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"""Get the hardware address on Unix by running ip."""
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@ -382,6 +404,7 @@ def _ip_getnode():
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mac = _find_mac('ip', 'link list', [b'link/ether'], lambda i: i+1)
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if mac:
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return mac
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return None
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def _arp_getnode():
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"""Get the hardware address on Unix by running arp."""
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@ -404,8 +427,10 @@ def _arp_getnode():
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# This works on Linux, FreeBSD and NetBSD
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mac = _find_mac('arp', '-an', [os.fsencode('(%s)' % ip_addr)],
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lambda i: i+2)
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# Return None instead of 0.
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if mac:
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return mac
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return None
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def _lanscan_getnode():
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"""Get the hardware address on Unix by running lanscan."""
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@ -415,32 +440,36 @@ def _lanscan_getnode():
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def _netstat_getnode():
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"""Get the hardware address on Unix by running netstat."""
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# This might work on AIX, Tru64 UNIX.
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first_local_mac = None
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try:
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proc = _popen('netstat', '-ia')
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if not proc:
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return
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return None
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with proc:
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words = proc.stdout.readline().rstrip().split()
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try:
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i = words.index(b'Address')
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except ValueError:
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return
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return None
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for line in proc.stdout:
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try:
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words = line.rstrip().split()
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word = words[i]
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if len(word) == 17 and word.count(b':') == 5:
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mac = int(word.replace(b':', b''), 16)
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if mac:
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if _is_universal(mac):
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return mac
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first_local_mac = first_local_mac or mac
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except (ValueError, IndexError):
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pass
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except OSError:
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pass
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return first_local_mac or None
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def _ipconfig_getnode():
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"""Get the hardware address on Windows by running ipconfig.exe."""
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import os, re
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first_local_mac = None
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dirs = ['', r'c:\windows\system32', r'c:\winnt\system32']
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try:
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import ctypes
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@ -458,18 +487,23 @@ def _ipconfig_getnode():
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for line in pipe:
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value = line.split(':')[-1].strip().lower()
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if re.match('([0-9a-f][0-9a-f]-){5}[0-9a-f][0-9a-f]', value):
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return int(value.replace('-', ''), 16)
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mac = int(value.replace('-', ''), 16)
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if _is_universal(mac):
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return mac
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first_local_mac = first_local_mac or mac
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return first_local_mac or None
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def _netbios_getnode():
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"""Get the hardware address on Windows using NetBIOS calls.
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See http://support.microsoft.com/kb/118623 for details."""
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import win32wnet, netbios
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first_local_mac = None
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ncb = netbios.NCB()
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ncb.Command = netbios.NCBENUM
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ncb.Buffer = adapters = netbios.LANA_ENUM()
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adapters._pack()
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if win32wnet.Netbios(ncb) != 0:
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return
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return None
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adapters._unpack()
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for i in range(adapters.length):
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ncb.Reset()
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@ -488,7 +522,11 @@ def _netbios_getnode():
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bytes = status.adapter_address[:6]
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if len(bytes) != 6:
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continue
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return int.from_bytes(bytes, 'big')
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mac = int.from_bytes(bytes, 'big')
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if _is_universal(mac):
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return mac
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first_local_mac = first_local_mac or mac
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return first_local_mac or None
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_generate_time_safe = _UuidCreate = None
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@ -601,9 +639,19 @@ def _windll_getnode():
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return UUID(bytes=bytes_(_buffer.raw)).node
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def _random_getnode():
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"""Get a random node ID, with eighth bit set as suggested by RFC 4122."""
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"""Get a random node ID."""
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# RFC 4122, $4.1.6 says "For systems with no IEEE address, a randomly or
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# pseudo-randomly generated value may be used; see Section 4.5. The
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# multicast bit must be set in such addresses, in order that they will
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# never conflict with addresses obtained from network cards."
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#
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# The "multicast bit" of a MAC address is defined to be "the least
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# significant bit of the first octet". This works out to be the 41st bit
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# counting from 1 being the least significant bit, or 1<<40.
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#
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# See https://en.wikipedia.org/wiki/MAC_address#Unicast_vs._multicast
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import random
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return random.getrandbits(48) | 0x010000000000
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return random.getrandbits(48) | (1 << 40)
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_node = None
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@ -626,13 +674,14 @@ def getnode():
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getters = [_unix_getnode, _ifconfig_getnode, _ip_getnode,
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_arp_getnode, _lanscan_getnode, _netstat_getnode]
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for getter in getters + [_random_getnode]:
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for getter in getters:
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try:
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_node = getter()
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except:
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continue
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if _node is not None:
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return _node
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return _random_getnode()
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_last_timestamp = None
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