lib/userspec.c

   1 /* userspec.c -- Parse a user and group string.
   2    Copyright (C) 1989, 1990, 1991, 1992 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software
  16    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  17
  18 /* Written by David MacKenzie <djm@gnu.ai.mit.edu>.  */
  19 \f
  20 #ifdef HAVE_CONFIG_H
  21 #if defined (CONFIG_BROKETS)
  22 /* We use <config.h> instead of "config.h" so that a compilation
  23    using -I. -I$srcdir will use ./config.h rather than $srcdir/config.h
  24    (which it would do because it found this file in $srcdir).  */
  25 #include <config.h>
  26 #else
  27 #include "config.h"
  28 #endif
  29 #endif
  30
  31 #include <stdio.h>
  32 #include <sys/types.h>
  33 #include <pwd.h>
  34 #include <grp.h>
  35
  36 #if defined(STDC_HEADERS) || defined(HAVE_STRING_H)
  37 #include <string.h>
  38 #ifndef index
  39 #define index strchr
  40 #endif
  41 #else
  42 #include <strings.h>
  43 #endif
  44
  45 #ifdef STDC_HEADERS
  46 #include <stdlib.h>
  47 #else
  48 char *malloc ();
  49 #endif
  50
  51 #ifdef HAVE_UNISTD_H
  52 #include <unistd.h>
  53 #endif
  54
  55 #ifndef _POSIX_VERSION
  56 struct passwd *getpwnam ();
  57 struct group *getgrnam ();
  58 struct group *getgrgid ();
  59 #endif
  60
  61 #ifdef _POSIX_SOURCE
  62 #define endpwent()
  63 #define endgrent()
  64 #endif
  65
  66 #define isdigit(c) ((c) >= '0' && (c) <= '9')
  67
  68 char *strdup ();
  69 static int isnumber ();
  70
  71 /* Extract from NAME, which has the form "[user][:.][group]",
  72    a USERNAME, UID U, GROUPNAME, and GID G.
  73    Either user or group, or both, must be present.
  74    If the group is omitted but the ":" or "." separator is given,
  75    use the given user's login group.
  76
  77    USERNAME and GROUPNAME will be in newly malloc'd memory.
  78    Either one might be NULL instead, indicating that it was not
  79    given and the corresponding numeric ID was left unchanged.
  80    Might write NULs into NAME.
  81
  82    Return NULL if successful, a static error message string if not.  */
  83
  84 char *
  85 parse_user_spec (name, uid, gid, username, groupname)
  86      char *name;
  87      uid_t *uid;
  88      gid_t *gid;
  89      char **username, **groupname;
  90 {
  91   static char *tired = "virtual memory exhausted";
  92   struct passwd *pwd;
  93   struct group *grp;
  94   char *cp;
  95   int use_login_group = 0;
  96
  97   *username = *groupname = NULL;
  98
  99   /* Check whether a group is given.  */
 100   cp = index (name, ':');
 101   if (cp == NULL)
 102     cp = index (name, '.');
 103   if (cp != NULL)
 104     {
 105       *cp++ = '\0';
 106       if (*cp == '\0')
 107         {
 108           if (cp == name + 1)
 109             /* Neither user nor group given, just "." or ":".  */
 110             return "can not omit both user and group";
 111           else
 112             /* "user.".  */
 113             use_login_group = 1;
 114         }
 115       else
 116         {
 117           /* Explicit group.  */
 118           *groupname = strdup (cp);
 119           if (*groupname == NULL)
 120             return tired;
 121           grp = getgrnam (cp);
 122           if (grp == NULL)
 123             {
 124               if (!isnumber (cp))
 125                 return "invalid group";
 126               *gid = atoi (cp);
 127             }
 128           else
 129             *gid = grp->gr_gid;
 130           endgrent ();          /* Save a file descriptor.  */
 131         }
 132     }
 133
 134   /* Parse the user name, now that any group has been removed.  */
 135
 136   if (name[0] == '\0')
 137     /* No user name was given, just a group.  */
 138     return NULL;
 139
 140   *username = strdup (name);
 141   if (*username == NULL)
 142     return tired;
 143
 144   pwd = getpwnam (name);
 145   if (pwd == NULL)
 146     {
 147       if (!isnumber (name))
 148         return "invalid user";
 149       if (use_login_group)
 150         return "cannot get the login group of a numeric UID";
 151       *uid = atoi (name);
 152     }
 153   else
 154     {
 155       *uid = pwd->pw_uid;
 156       if (use_login_group)
 157         {
 158           *gid = pwd->pw_gid;
 159           grp = getgrgid (pwd->pw_gid);
 160           if (grp == NULL)
 161             {
 162               *groupname = malloc (15);
 163               if (*groupname == NULL)
 164                 return tired;
 165               sprintf (*groupname, "%u", pwd->pw_gid);
 166             }
 167           else
 168             {
 169               *groupname = strdup (grp->gr_name);
 170               if (*groupname == NULL)
 171                 return tired;
 172             }
 173           endgrent ();
 174         }
 175     }
 176   endpwent ();
 177   return NULL;
 178 }
 179
 180 /* Return nonzero if STR represents an unsigned decimal integer,
 181    otherwise return 0. */
 182
 183 static int
 184 isnumber (str)
 185      char *str;
 186 {
 187   for (; *str; str++)
 188     if (!isdigit (*str))
 189       return 0;
 190   return 1;
 191 }