lib/userspec.c

   1 /* userspec.c -- Parse a user and group string.
   2    Copyright (C) 1989-1992, 1997, 1998, 2000 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 Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 /* Written by David MacKenzie <djm@gnu.ai.mit.edu>.  */
  19
  20 #if HAVE_CONFIG_H
  21 # include <config.h>
  22 #endif
  23
  24 #ifdef __GNUC__
  25 # define alloca __builtin_alloca
  26 #else
  27 # if HAVE_ALLOCA_H
  28 #  include <alloca.h>
  29 # else
  30 #  ifdef _AIX
  31  #  pragma alloca
  32 #  else
  33 char *alloca ();
  34 #  endif
  35 # endif
  36 #endif
  37
  38 #include <stdio.h>
  39 #include <sys/types.h>
  40 #include <pwd.h>
  41 #include <grp.h>
  42
  43 #if HAVE_SYS_PARAM_H
  44 # include <sys/param.h>
  45 #endif
  46
  47 #if HAVE_LIMITS_H
  48 # include <limits.h>
  49 #endif
  50
  51 #if HAVE_STRING_H
  52 # include <string.h>
  53 #else
  54 # include <strings.h>
  55 # ifndef strchr
  56 #  define strchr index
  57 # endif
  58 #endif
  59
  60 #if STDC_HEADERS
  61 # include <stdlib.h>
  62 #endif
  63
  64 #if HAVE_UNISTD_H
  65 # include <unistd.h>
  66 #endif
  67
  68 #include "xalloc.h"
  69 #include "xstrtol.h"
  70
  71 #if ENABLE_NLS
  72 # include <libintl.h>
  73 # define _(Text) gettext (Text)
  74 #else
  75 # define _(Text) Text
  76 #endif
  77 #define N_(Text) Text
  78
  79 #ifndef _POSIX_VERSION
  80 struct passwd *getpwnam ();
  81 struct group *getgrnam ();
  82 struct group *getgrgid ();
  83 #endif
  84
  85 #ifndef HAVE_ENDGRENT
  86 # define endgrent() ((void) 0)
  87 #endif
  88
  89 #ifndef HAVE_ENDPWENT
  90 # define endpwent() ((void) 0)
  91 #endif
  92
  93 #ifndef CHAR_BIT
  94 # define CHAR_BIT 8
  95 #endif
  96
  97 /* The extra casts work around common compiler bugs.  */
  98 #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
  99 /* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
 100    It is necessary at least when t == time_t.  */
 101 #define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \
 102                               ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) : (t) 0))
 103 #define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t)))
 104
 105 #ifndef UID_T_MAX
 106 # define UID_T_MAX TYPE_MAXIMUM (uid_t)
 107 #endif
 108
 109 #ifndef GID_T_MAX
 110 # define GID_T_MAX TYPE_MAXIMUM (gid_t)
 111 #endif
 112
 113 /* MAXUID may come from limits.h or sys/params.h.  */
 114 #ifndef MAXUID
 115 # define MAXUID UID_T_MAX
 116 #endif
 117 #ifndef MAXGID
 118 # define MAXGID GID_T_MAX
 119 #endif
 120
 121 /* Perform the equivalent of the statement `dest = strdup (src);',
 122    but obtaining storage via alloca instead of from the heap.  */
 123
 124 #define V_STRDUP(dest, src)                                             \
 125   do                                                                    \
 126     {                                                                   \
 127       int _len = strlen ((src));                                        \
 128       (dest) = (char *) alloca (_len + 1);                              \
 129       strcpy (dest, src);                                               \
 130     }                                                                   \
 131   while (0)
 132
 133 /* ISDIGIT differs from isdigit, as follows:
 134    - Its arg may be any int or unsigned int; it need not be an unsigned char.
 135    - It's guaranteed to evaluate its argument exactly once.
 136    - It's typically faster.
 137    Posix 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 says that
 138    only '0' through '9' are digits.  Prefer ISDIGIT to isdigit unless
 139    it's important to use the locale's definition of `digit' even when the
 140    host does not conform to Posix.  */
 141 #define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)
 142
 143 #ifndef strdup
 144 char *strdup ();
 145 #endif
 146
 147 /* Return nonzero if STR represents an unsigned decimal integer,
 148    otherwise return 0. */
 149
 150 static int
 151 is_number (const char *str)
 152 {
 153   for (; *str; str++)
 154     if (!ISDIGIT (*str))
 155       return 0;
 156   return 1;
 157 }
 158
 159 /* Extract from NAME, which has the form "[user][:.][group]",
 160    a USERNAME, UID U, GROUPNAME, and GID G.
 161    Either user or group, or both, must be present.
 162    If the group is omitted but the ":" separator is given,
 163    use the given user's login group.
 164    If SPEC_ARG contains a `:', then use that as the separator, ignoring
 165    any `.'s.  If there is no `:', but there is a `.', then first look
 166    up the entire SPEC_ARG as a login name.  If that look-up fails, then
 167    try again interpreting the `.'  as a separator.
 168
 169    USERNAME and GROUPNAME will be in newly malloc'd memory.
 170    Either one might be NULL instead, indicating that it was not
 171    given and the corresponding numeric ID was left unchanged.
 172
 173    Return NULL if successful, a static error message string if not.  */
 174
 175 const char *
 176 parse_user_spec (const char *spec_arg, uid_t *uid, gid_t *gid,
 177                  char **username_arg, char **groupname_arg)
 178 {
 179   static const char *E_invalid_user = N_("invalid user");
 180   static const char *E_invalid_group = N_("invalid group");
 181   static const char *E_bad_spec =
 182     N_("cannot get the login group of a numeric UID");
 183   static const char *E_cannot_omit_both =
 184     N_("cannot omit both user and group");
 185
 186   const char *error_msg;
 187   char *spec;                   /* A copy we can write on.  */
 188   struct passwd *pwd;
 189   struct group *grp;
 190   char *g, *u, *separator;
 191   char *groupname;
 192   int maybe_retry = 0;
 193   char *dot = NULL;
 194
 195   error_msg = NULL;
 196   *username_arg = *groupname_arg = NULL;
 197   groupname = NULL;
 198
 199   V_STRDUP (spec, spec_arg);
 200
 201   /* Find the POSIX `:' separator if there is one.  */
 202   separator = strchr (spec, ':');
 203
 204   /* If there is no colon, then see if there's a `.'.  */
 205   if (separator == NULL)
 206     {
 207       dot = strchr (spec, '.');
 208       /* If there's no colon but there is a `.', then first look up the
 209          whole spec, in case it's an OWNER name that includes a dot.
 210          If that fails, then we'll try again, but interpreting the `.'
 211          as a separator.  */
 212       /* FIXME: accepting `.' as the separator is contrary to POSIX.
 213          someday we should drop support for this.  */
 214       if (dot)
 215         maybe_retry = 1;
 216     }
 217
 218  retry:
 219
 220   /* Replace separator with a NUL.  */
 221   if (separator != NULL)
 222     *separator = '\0';
 223
 224   /* Set U and G to non-zero length strings corresponding to user and
 225      group specifiers or to NULL.  */
 226   u = (*spec == '\0' ? NULL : spec);
 227
 228   g = (separator == NULL || *(separator + 1) == '\0'
 229        ? NULL
 230        : separator + 1);
 231
 232   if (u == NULL && g == NULL)
 233     return _(E_cannot_omit_both);
 234
 235 #ifdef __DJGPP__
 236   /* Pretend that we are the user U whose group is G.  This makes
 237      pwd and grp functions ``know'' about the UID and GID of these.  */
 238   if (u && !is_number (u))
 239     setenv ("USER", u, 1);
 240   if (g && !is_number (g))
 241     setenv ("GROUP", g, 1);
 242 #endif
 243
 244   if (u != NULL)
 245     {
 246       pwd = getpwnam (u);
 247       if (pwd == NULL)
 248         {
 249
 250           if (!is_number (u))
 251             error_msg = E_invalid_user;
 252           else
 253             {
 254               int use_login_group;
 255               use_login_group = (separator != NULL && g == NULL);
 256               if (use_login_group)
 257                 error_msg = E_bad_spec;
 258               else
 259                 {
 260                   unsigned long int tmp_long;
 261                   if (xstrtoul (u, NULL, 0, &tmp_long, NULL) != LONGINT_OK
 262                       || tmp_long > MAXUID)
 263                     return _(E_invalid_user);
 264                   *uid = tmp_long;
 265                 }
 266             }
 267         }
 268       else
 269         {
 270           *uid = pwd->pw_uid;
 271           if (g == NULL && separator != NULL)
 272             {
 273               /* A separator was given, but a group was not specified,
 274                  so get the login group.  */
 275               *gid = pwd->pw_gid;
 276               grp = getgrgid (pwd->pw_gid);
 277               if (grp == NULL)
 278                 {
 279                   /* This is enough room to hold the unsigned decimal
 280                      representation of any 32-bit quantity and the trailing
 281                      zero byte.  */
 282                   char uint_buf[21];
 283                   sprintf (uint_buf, "%u", (unsigned) (pwd->pw_gid));
 284                   V_STRDUP (groupname, uint_buf);
 285                 }
 286               else
 287                 {
 288                   V_STRDUP (groupname, grp->gr_name);
 289                 }
 290               endgrent ();
 291             }
 292         }
 293       endpwent ();
 294     }
 295
 296   if (g != NULL && error_msg == NULL)
 297     {
 298       /* Explicit group.  */
 299       grp = getgrnam (g);
 300       if (grp == NULL)
 301         {
 302           if (!is_number (g))
 303             error_msg = E_invalid_group;
 304           else
 305             {
 306               unsigned long int tmp_long;
 307               if (xstrtoul (g, NULL, 0, &tmp_long, NULL) != LONGINT_OK
 308                   || tmp_long > MAXGID)
 309                 return _(E_invalid_group);
 310               *gid = tmp_long;
 311             }
 312         }
 313       else
 314         *gid = grp->gr_gid;
 315       endgrent ();              /* Save a file descriptor.  */
 316
 317       if (error_msg == NULL)
 318         V_STRDUP (groupname, g);
 319     }
 320
 321   if (error_msg == NULL)
 322     {
 323       if (u != NULL)
 324         {
 325           *username_arg = strdup (u);
 326           if (*username_arg == NULL)
 327             error_msg = xalloc_msg_memory_exhausted;
 328         }
 329
 330       if (groupname != NULL && error_msg == NULL)
 331         {
 332           *groupname_arg = strdup (groupname);
 333           if (*groupname_arg == NULL)
 334             {
 335               if (*username_arg != NULL)
 336                 {
 337                   free (*username_arg);
 338                   *username_arg = NULL;
 339                 }
 340               error_msg = xalloc_msg_memory_exhausted;
 341             }
 342         }
 343     }
 344
 345   if (error_msg && maybe_retry)
 346     {
 347       maybe_retry = 0;
 348       separator = dot;
 349       error_msg = NULL;
 350       goto retry;
 351     }
 352
 353   return _(error_msg);
 354 }
 355
 356 #ifdef TEST
 357
 358 # define NULL_CHECK(s) ((s) == NULL ? "(null)" : (s))
 359
 360 int
 361 main (int argc, char **argv)
 362 {
 363   int i;
 364
 365   for (i = 1; i < argc; i++)
 366     {
 367       const char *e;
 368       char *username, *groupname;
 369       uid_t uid;
 370       gid_t gid;
 371       char *tmp;
 372
 373       tmp = strdup (argv[i]);
 374       e = parse_user_spec (tmp, &uid, &gid, &username, &groupname);
 375       free (tmp);
 376       printf ("%s: %u %u %s %s %s\n",
 377               argv[i],
 378               (unsigned int) uid,
 379               (unsigned int) gid,
 380               NULL_CHECK (username),
 381               NULL_CHECK (groupname),
 382               NULL_CHECK (e));
 383     }
 384
 385   exit (0);
 386 }
 387
 388 #endif