setauth segfaults when giving an inexistent username

[Marc-Olivier Mercier]

Hi all,

I tried to used setauth and it segfaults when I passed a wrong user name 
(or even a wrong group name). The problem is when the args are parsed. 
In libshouldbeinlibc/ugids-argp.c, the function getpwnam_r is used. It 
is assumed that getpwnam_r return non-zero if the user does not exist, 
which is false. There's nothing in the POSIX spec that tells that user 
name that doesn't exist should return an error. In fact, this is 
considered as a success. The only way to know for sure that a user 
doesn't exist is by looking if pwbufp is NULL. The same thing applies to 
the group and the getgrnam_r function.

I attached a patch, but i want to know what is supposed to be done when 
there's a real error return by getpwnam_r.

Marc. O

Index: libshouldbeinlibc/ugids-argp.c
===================================================================
RCS file: /sources/hurd/hurd/libshouldbeinlibc/ugids-argp.c,v
retrieving revision 1.2
diff -u -p -r1.2 ugids-argp.c
--- libshouldbeinlibc/ugids-argp.c      11 Jul 1999 06:02:55 -0000      1.2
+++ libshouldbeinlibc/ugids-argp.c      13 Mar 2008 23:30:24 -0000
@@ -83,14 +83,22 @@ parse_opt (int key, char *arg, struct ar
       else
        {
          struct passwd _pw, *pw;
-         if (getpwnam_r (arg, &_pw, id_lookup_buf, sizeof id_lookup_buf, &pw)
-             == 0)
-           uid = pw->pw_uid;
+          int error;
+         error = getpwnam_r (arg, &_pw, id_lookup_buf, 
+                          sizeof id_lookup_buf, &pw);
+         if (error == 0)
+            {
+              /* Even if the username does not exist, getpwnam_r succeded */
+              if (pw == NULL)
+                {
+                 argp_failure (state, 10, 0, "%s: Unknown user", arg);
+                  return EINVAL;
+                }
+
+             uid = pw->pw_uid;
+            }
          else
-           {
-             argp_failure (state, 10, 0, "%s: Unknown user", arg);
-             return EINVAL;
-           }
+           return error;
        }
 
       if (key == ARGP_KEY_ARG || key == ARGP_KEY_END)
@@ -121,14 +129,20 @@ parse_opt (int key, char *arg, struct ar
       else
        {
          struct group _gr, *gr;
-         if (getgrnam_r (arg, &_gr, id_lookup_buf, sizeof id_lookup_buf, &gr)
-             == 0)
-           return ugids_add_gid (ugids, gr->gr_gid, key == 'G');
+          int error = getgrnam_r (arg, &_gr, id_lookup_buf, 
+                                  sizeof id_lookup_buf, &gr);
+         if (error == 0)
+            {
+              if (gr == NULL)
+                {
+                 argp_failure (state, 11, 0, "%s: Unknown group", arg);
+                 return EINVAL;
+                }
+
+             return ugids_add_gid (ugids, gr->gr_gid, key == 'G');
+            }
          else
-           {
-             argp_failure (state, 11, 0, "%s: Unknown group", arg);
-             return EINVAL;
-           }
+           return error;
        }
 
     default: