GNU bug report logs - #53631
coreutils id(1) incorrect behavior

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: "Vladimir D. Seleznev" <vseleznv <at> altlinux.org>
Subject: bug#53631: closed (Re: bug#53631: coreutils id(1) incorrect behavior)
Date: Fri, 04 Feb 2022 23:00:03 +0000

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Your bug report

#53631: coreutils id(1) incorrect behavior

which was filed against the coreutils package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 53631 <at> debbugs.gnu.org.

-- 
53631: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=53631
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Paul Eggert <eggert <at> cs.ucla.edu>
To: "Vladimir D. Seleznev" <vseleznv <at> altlinux.org>
Cc: 53631-done <at> debbugs.gnu.org
Subject: Re: bug#53631: coreutils id(1) incorrect behavior
Date: Fri, 4 Feb 2022 14:59:20 -0800

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Thanks for the bug report. I installed the attached patch, which I hope 
fixes things for you, and am boldly closing the bug report.

This fix depends on the latest lib/userspec.c from Gnulib; see 
<https://lists.gnu.org/r/bug-gnulib/2022-02/msg00000.html>.

[0001-id-print-groups-of-listed-name.patch (text/x-patch, attachment)]

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From: "Vladimir D. Seleznev" <vseleznv <at> altlinux.org>
To: bug-coreutils <at> gnu.org
Cc: "Vladimir D. Seleznev" <vseleznv <at> altlinux.org>
Subject: coreutils id(1) incorrect behavior
Date: Sun, 30 Jan 2022 03:52:29 +0300

Hi, bug-coreutils@!

Recently I found an issue in the coreutils id(1) behavior. For coreutils
v8.32-165-g18dbcae25, `id username` prints user and group IDs for the
first matched user with the identical UID. In the case where there are
several users with the identical UID in the system it can be misleading.

Example:

	# useradd user1
	# groupadd somegroup
	# useradd -o -u "$(id -u user1)" -g "$(id -G user1) -G somegroup user2
	# id user1
	uid=1027(user1) gid=1027(user1) groups=1027(user1)
	# id user2
	uid=1027(user1) gid=1027(user1) groups=1027(user1)
	# su - user2
	$ id
	uid=1027(user1) gid=1027(user1) groups=1027(user1),1028(somegroup)

Expected behavior is:

	# id user1
	uid=1027(user1) gid=1027(user1) groups=1027(user1)
	# id user2
	uid=1027(user1) gid=1027(user1) groups=1027(user1),1028(somegroup)

Looking at the code, I found that id uses parse_user_spec() to obtain
euid of username (or uid) command line argument, and then it obtains all
the rest needed information by this euid.

	for (; optind < n_ids; optind++)
	{
	  struct passwd *pwd = NULL;
	  char const *spec = argv[optind];
	  /* Disallow an empty spec here as parse_user_spec() doesn't
	     give an error for that as it seems it's a valid way to
	     specify a noop or "reset special bits" depending on the system.  */
	  if (*spec)
	    {
	      if (parse_user_spec (spec, &euid, NULL, NULL, NULL) == NULL)
		{
		  /* parse_user_spec will only extract a numeric spec,
		     so we lookup that here to verify and also retrieve
		     the PW_NAME used subsequently in group lookup.  */
		  pwd = getpwuid (euid);
		}
	    }


-- 
   WBR,
   Vladimir D. Seleznev

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