Bug report

UUID reads the MAC address from the local system in order to generate UUIDv1/v2 spec requests. On Linux and Darwin and unknown platforms it will attempt to run _ifconfig_getnode() to search throughifconfig in order to get the MAC value by searching ifconfig. On MacOS and Unknown platforms it will do this first. (https://github.com/python/cpython/blob/main/Lib/uuid.py#L627)

_ifconfig_getnode() is designed to take a number of args, likely to support multiple systems. Currently this supports 3 flags,'' '-a' and '-av' (https://github.com/python/cpython/blob/main/Lib/uuid.py#L510). This function can never move passed calling the first argument as it will always return. Worse yet, on MacOS and linux passing'' as the argument will actually run the equivalent of/sbin/ifconfig "" which will always return to stderr (which is discarded). This is very likely due to the developer not understanding how popen generates the command string (seehttps://github.com/python/cpython/blob/main/Lib/subprocess.py#L615)

Due to an incorrectly tabbed return statement this will always result in the function bailing out before testing other valid options. In all tested cases this also results in the function ALWAYS return None. Making the check useless.

    for args in ('', '-a', '-av'):        mac = _find_mac_near_keyword('ifconfig', args, keywords, lambda i: i+1)        if mac:            return mac        return None

https://github.com/python/cpython/blob/main/Lib/uuid.py#L506

The smallest example of this problem looks something like this

    import subprocess    """Get the hardware address on Unix by running ifconfig."""    # This works on Linux ('' or '-a'), Tru64 ('-av'), but not all Unixes.    for args in ('', '-a', '-av'):        proc = subprocess.Popen(("/sbin/ifconfig",) + (args,),                        stdout=subprocess.PIPE,                        stderr=subprocess.DEVNULL)        if not proc:            return None        stdout, stderr = proc.communicate()        mac = stdout # This is fine for this example (normally it'd have parsed out a mac        if mac:            return mac        return None

Your environment

• Python 3.10.6
• macOS 13.0 Beta 10

• PR:gh-98415: Fix UUID ifconfig MAC address detection #98423

• PR:[3.10] gh-98415: Fix uuid.getnode() ifconfig implementation (GH-98423) #99020

• PR:[3.11] gh-98415: Fix uuid.getnode() ifconfig implementation (GH-98423) #99021