[Pkg-shadow-devel] [PATCH] new?idmap: verbose error when uid/gid do not match

[Hank Leininger]

Below is a patch that expands the error message when newuidmap /
newgidmap do not like the user/group ownership of their target process.

Currently the error is just:

newuidmap: Target [pid] is owned by a different user

With this patch it will be like:

newuidmap: Target [pid] is owned by a different user: uid:0 pw_uid:0 st_uid:0, gid:0 pw_gid:0 st_gid:99

Why is this useful?  Well, in my case...

The grsecurity kernel-hardening patch includes an option to make parts
of /proc unreadable, such as /proc/pid/ dirs for processes not owned by
the current uid.  This comes with an option to make /proc/pid/
directories readable by a specific gid; sysadmins and the like are then
put into that group so they can see a full 'ps'.

This means that the check in new[ug]idmap fails, as in the above quoted
error - /proc/[targetpid] is owned by root, but the group is 99 so that
users in group 99 can see the process.

Some Googling finds dozens of people hitting this problem, but not
*knowing* that they have hit this problem, because the errors and
circumstances are non-obvious.

Some graceful way of handling this and not failing, will be next ;)  But
in the meantime it'd be nice to have new[ug]idmap emit a more useful
error, so that it's easier to troubleshoot.

Thanks!

Signed-off-by: Hank Leininger <hlein at korelogic.com>
---

diff -urP shadow-4.2.1.orig/src/newgidmap.c shadow-4.2.1/src/newgidmap.c
--- shadow-4.2.1.orig/src/newgidmap.c	2014-03-01 13:59:51.000000000 -0500
+++ shadow-4.2.1/src/newgidmap.c	2015-03-25 00:37:39.074144574 -0400
@@ -160,8 +160,10 @@
 	    (getgid() != pw->pw_gid) ||
 	    (pw->pw_uid != st.st_uid) ||
 	    (pw->pw_gid != st.st_gid)) {
-		fprintf(stderr, _( "%s: Target %u is owned by a different user\n" ),
-			Prog, target);
+		fprintf(stderr, _( "%s: Target %u is owned by a different user: uid:%lu pw_uid:%lu st_uid:%lu, gid:%lu pw_gid:%lu st_gid:%lu\n" ),
+			Prog, target,
+			(unsigned long int)getuid(), (unsigned long int)pw->pw_uid, (unsigned long int)st.st_uid,
+			(unsigned long int)getgid(), (unsigned long int)pw->pw_gid, (unsigned long int)st.st_gid);
 		return EXIT_FAILURE;
 	}
 
diff -urP shadow-4.2.1.orig/src/newuidmap.c shadow-4.2.1/src/newuidmap.c
--- shadow-4.2.1.orig/src/newuidmap.c	2014-03-01 13:59:51.000000000 -0500
+++ shadow-4.2.1/src/newuidmap.c	2015-03-25 00:36:56.138141710 -0400
@@ -160,8 +160,10 @@
 	    (getgid() != pw->pw_gid) ||
 	    (pw->pw_uid != st.st_uid) ||
 	    (pw->pw_gid != st.st_gid)) {
-		fprintf(stderr, _( "%s: Target %u is owned by a different user\n" ),
-			Prog, target);
+		fprintf(stderr, _( "%s: Target process %u is owned by a different user: uid:%lu pw_uid:%lu st_uid:%lu, gid:%lu pw_gid:%lu st_gid:%lu\n" ),
+			Prog, target,
+			(unsigned long int)getuid(), (unsigned long int)pw->pw_uid, (unsigned long int)st.st_uid,
+			(unsigned long int)getgid(), (unsigned long int)pw->pw_gid, (unsigned long int)st.st_gid);
 		return EXIT_FAILURE;
 	}
 
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