lib/modechange.c

   1 /* modechange.c -- file mode manipulation
   2
   3    Copyright (C) 1989, 1990, 1997, 1998, 1999, 2001, 2003 Free Software
   4    Foundation, Inc.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software Foundation,
  18    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20 /* Written by David MacKenzie <djm@ai.mit.edu> */
  21
  22 /* The ASCII mode string is compiled into a linked list of `struct
  23    modechange', which can then be applied to each file to be changed.
  24    We do this instead of re-parsing the ASCII string for each file
  25    because the compiled form requires less computation to use; when
  26    changing the mode of many files, this probably results in a
  27    performance gain. */
  28
  29 #if HAVE_CONFIG_H
  30 # include <config.h>
  31 #endif
  32
  33 #include "modechange.h"
  34 #include <sys/stat.h>
  35 #include "xstrtol.h"
  36 #include <stddef.h>
  37 #include <stdlib.h>
  38
  39 #if STAT_MACROS_BROKEN
  40 # undef S_ISDIR
  41 #endif
  42
  43 #if !defined(S_ISDIR) && defined(S_IFDIR)
  44 # define S_ISDIR(m) (((m) & S_IFMT) == S_IFDIR)
  45 #endif
  46
  47 /* The traditional octal values corresponding to each mode bit.  */
  48 #define SUID 04000
  49 #define SGID 02000
  50 #define SVTX 01000
  51 #define RUSR 00400
  52 #define WUSR 00200
  53 #define XUSR 00100
  54 #define RGRP 00040
  55 #define WGRP 00020
  56 #define XGRP 00010
  57 #define ROTH 00004
  58 #define WOTH 00002
  59 #define XOTH 00001
  60 #define ALLM 07777 /* all octal mode bits */
  61
  62 #ifndef S_ISUID
  63 # define S_ISUID SUID
  64 #endif
  65 #ifndef S_ISGID
  66 # define S_ISGID SGID
  67 #endif
  68 #ifndef S_ISVTX
  69 # define S_ISVTX SVTX
  70 #endif
  71 #ifndef S_IRUSR
  72 # define S_IRUSR RUSR
  73 #endif
  74 #ifndef S_IWUSR
  75 # define S_IWUSR WUSR
  76 #endif
  77 #ifndef S_IXUSR
  78 # define S_IXUSR XUSR
  79 #endif
  80 #ifndef S_IRGRP
  81 # define S_IRGRP RGRP
  82 #endif
  83 #ifndef S_IWGRP
  84 # define S_IWGRP WGRP
  85 #endif
  86 #ifndef S_IXGRP
  87 # define S_IXGRP XGRP
  88 #endif
  89 #ifndef S_IROTH
  90 # define S_IROTH ROTH
  91 #endif
  92 #ifndef S_IWOTH
  93 # define S_IWOTH WOTH
  94 #endif
  95 #ifndef S_IXOTH
  96 # define S_IXOTH XOTH
  97 #endif
  98 #ifndef S_IRWXU
  99 # define S_IRWXU (S_IRUSR | S_IWUSR | S_IXUSR)
 100 #endif
 101 #ifndef S_IRWXG
 102 # define S_IRWXG (S_IRGRP | S_IWGRP | S_IXGRP)
 103 #endif
 104 #ifndef S_IRWXO
 105 # define S_IRWXO (S_IROTH | S_IWOTH | S_IXOTH)
 106 #endif
 107
 108 /* All the mode bits that can be affected by chmod.  */
 109 #define CHMOD_MODE_BITS \
 110   (S_ISUID | S_ISGID | S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO)
 111
 112 /* Return newly allocated memory to hold one element of type TYPE. */
 113 #define talloc(type) ((type *) malloc (sizeof (type)))
 114
 115 /* Create a mode_change entry with the specified `=ddd'-style
 116    mode change operation, where NEW_MODE is `ddd'.  Return the
 117    new entry, or NULL upon failure.  */
 118
 119 static struct mode_change *
 120 make_node_op_equals (mode_t new_mode)
 121 {
 122   struct mode_change *p;
 123   p = talloc (struct mode_change);
 124   if (p == NULL)
 125     return p;
 126   p->next = NULL;
 127   p->op = '=';
 128   p->flags = 0;
 129   p->value = new_mode;
 130   p->affected = CHMOD_MODE_BITS;        /* Affect all permissions. */
 131   return p;
 132 }
 133
 134 /* Append entry E to the end of the link list with the specified
 135    HEAD and TAIL.  */
 136
 137 static void
 138 mode_append_entry (struct mode_change **head,
 139                    struct mode_change **tail,
 140                    struct mode_change *e)
 141 {
 142   if (*head == NULL)
 143     *head = *tail = e;
 144   else
 145     {
 146       (*tail)->next = e;
 147       *tail = e;
 148     }
 149 }
 150
 151 /* Return a linked list of file mode change operations created from
 152    MODE_STRING, an ASCII string that contains either an octal number
 153    specifying an absolute mode, or symbolic mode change operations with
 154    the form:
 155    [ugoa...][[+-=][rwxXstugo...]...][,...]
 156    MASKED_OPS is a bitmask indicating which symbolic mode operators (=+-)
 157    should not affect bits set in the umask when no users are given.
 158    Operators not selected in MASKED_OPS ignore the umask.
 159
 160    Return MODE_INVALID if `mode_string' does not contain a valid
 161    representation of file mode change operations;
 162    return MODE_MEMORY_EXHAUSTED if there is insufficient memory. */
 163
 164 struct mode_change *
 165 mode_compile (const char *mode_string, unsigned int masked_ops)
 166 {
 167   struct mode_change *head;     /* First element of the linked list. */
 168   struct mode_change *tail;     /* An element of the linked list. */
 169   unsigned long octal_value;    /* The mode value, if octal.  */
 170   mode_t umask_value;           /* The umask value (surprise). */
 171
 172   head = NULL;
 173 #ifdef lint
 174   tail = NULL;
 175 #endif
 176
 177   if (xstrtoul (mode_string, NULL, 8, &octal_value, "") == LONGINT_OK)
 178     {
 179       struct mode_change *p;
 180       mode_t mode;
 181       if (octal_value != (octal_value & ALLM))
 182         return MODE_INVALID;
 183
 184       /* Help the compiler optimize the usual case where mode_t uses
 185          the traditional octal representation.  */
 186       mode = ((S_ISUID == SUID && S_ISGID == SGID && S_ISVTX == SVTX
 187                && S_IRUSR == RUSR && S_IWUSR == WUSR && S_IXUSR == XUSR
 188                && S_IRGRP == RGRP && S_IWGRP == WGRP && S_IXGRP == XGRP
 189                && S_IROTH == ROTH && S_IWOTH == WOTH && S_IXOTH == XOTH)
 190               ? octal_value
 191               : (mode_t) ((octal_value & SUID ? S_ISUID : 0)
 192                           | (octal_value & SGID ? S_ISGID : 0)
 193                           | (octal_value & SVTX ? S_ISVTX : 0)
 194                           | (octal_value & RUSR ? S_IRUSR : 0)
 195                           | (octal_value & WUSR ? S_IWUSR : 0)
 196                           | (octal_value & XUSR ? S_IXUSR : 0)
 197                           | (octal_value & RGRP ? S_IRGRP : 0)
 198                           | (octal_value & WGRP ? S_IWGRP : 0)
 199                           | (octal_value & XGRP ? S_IXGRP : 0)
 200                           | (octal_value & ROTH ? S_IROTH : 0)
 201                           | (octal_value & WOTH ? S_IWOTH : 0)
 202                           | (octal_value & XOTH ? S_IXOTH : 0)));
 203
 204       p = make_node_op_equals (mode);
 205       if (p == NULL)
 206         return MODE_MEMORY_EXHAUSTED;
 207       mode_append_entry (&head, &tail, p);
 208       return head;
 209     }
 210
 211   umask_value = umask (0);
 212   umask (umask_value);          /* Restore the old value. */
 213   --mode_string;
 214
 215   /* One loop iteration for each "ugoa...=+-rwxXstugo...[=+-rwxXstugo...]". */
 216   do
 217     {
 218       /* Which bits in the mode are operated on. */
 219       mode_t affected_bits = 0;
 220       /* `affected_bits' modified by umask. */
 221       mode_t affected_masked;
 222       /* Operators to actually use umask on. */
 223       unsigned ops_to_mask = 0;
 224
 225       int who_specified_p;
 226
 227       affected_bits = 0;
 228       ops_to_mask = 0;
 229       /* Turn on all the bits in `affected_bits' for each group given. */
 230       for (++mode_string;; ++mode_string)
 231         switch (*mode_string)
 232           {
 233           case 'u':
 234             affected_bits |= S_ISUID | S_IRWXU;
 235             break;
 236           case 'g':
 237             affected_bits |= S_ISGID | S_IRWXG;
 238             break;
 239           case 'o':
 240             affected_bits |= S_ISVTX | S_IRWXO;
 241             break;
 242           case 'a':
 243             affected_bits |= CHMOD_MODE_BITS;
 244             break;
 245           default:
 246             goto no_more_affected;
 247           }
 248
 249     no_more_affected:
 250       /* If none specified, affect all bits, except perhaps those
 251          set in the umask. */
 252       if (affected_bits)
 253         who_specified_p = 1;
 254       else
 255         {
 256           who_specified_p = 0;
 257           affected_bits = CHMOD_MODE_BITS;
 258           ops_to_mask = masked_ops;
 259         }
 260
 261       while (*mode_string == '=' || *mode_string == '+' || *mode_string == '-')
 262         {
 263           struct mode_change *change = talloc (struct mode_change);
 264           if (change == NULL)
 265             {
 266               mode_free (head);
 267               return MODE_MEMORY_EXHAUSTED;
 268             }
 269
 270           change->next = NULL;
 271           change->op = *mode_string;    /* One of "=+-". */
 272           affected_masked = affected_bits;
 273
 274           /* Per the Single Unix Spec, if `who' is not specified and the
 275              `=' operator is used, then clear all the bits first.  */
 276           if (!who_specified_p &&
 277               ops_to_mask & (*mode_string == '=' ? MODE_MASK_EQUALS : 0))
 278             {
 279               struct mode_change *p = make_node_op_equals (0);
 280               if (p == NULL)
 281                 return MODE_MEMORY_EXHAUSTED;
 282               mode_append_entry (&head, &tail, p);
 283             }
 284
 285           if (ops_to_mask & (*mode_string == '=' ? MODE_MASK_EQUALS
 286                              : *mode_string == '+' ? MODE_MASK_PLUS
 287                              : MODE_MASK_MINUS))
 288             affected_masked &= ~umask_value;
 289           change->affected = affected_masked;
 290           change->value = 0;
 291           change->flags = 0;
 292
 293           /* Add the element to the tail of the list, so the operations
 294              are performed in the correct order. */
 295           mode_append_entry (&head, &tail, change);
 296
 297           /* Set `value' according to the bits set in `affected_masked'. */
 298           for (++mode_string;; ++mode_string)
 299             switch (*mode_string)
 300               {
 301               case 'r':
 302                 change->value |= ((S_IRUSR | S_IRGRP | S_IROTH)
 303                                   & affected_masked);
 304                 break;
 305               case 'w':
 306                 change->value |= ((S_IWUSR | S_IWGRP | S_IWOTH)
 307                                   & affected_masked);
 308                 break;
 309               case 'X':
 310                 change->flags |= MODE_X_IF_ANY_X;
 311                 /* Fall through. */
 312               case 'x':
 313                 change->value |= ((S_IXUSR | S_IXGRP | S_IXOTH)
 314                                   & affected_masked);
 315                 break;
 316               case 's':
 317                 /* Set the setuid/gid bits if `u' or `g' is selected. */
 318                 change->value |= (S_ISUID | S_ISGID) & affected_masked;
 319                 break;
 320               case 't':
 321                 /* Set the "save text image" bit if `o' is selected. */
 322                 change->value |= S_ISVTX & affected_masked;
 323                 break;
 324               case 'u':
 325                 /* Set the affected bits to the value of the `u' bits
 326                    on the same file.  */
 327                 if (change->value)
 328                   goto invalid;
 329                 change->value = S_IRWXU;
 330                 change->flags |= MODE_COPY_EXISTING;
 331                 break;
 332               case 'g':
 333                 /* Set the affected bits to the value of the `g' bits
 334                    on the same file.  */
 335                 if (change->value)
 336                   goto invalid;
 337                 change->value = S_IRWXG;
 338                 change->flags |= MODE_COPY_EXISTING;
 339                 break;
 340               case 'o':
 341                 /* Set the affected bits to the value of the `o' bits
 342                    on the same file.  */
 343                 if (change->value)
 344                   goto invalid;
 345                 change->value = S_IRWXO;
 346                 change->flags |= MODE_COPY_EXISTING;
 347                 break;
 348               default:
 349                 goto no_more_values;
 350               }
 351         no_more_values:;
 352         }
 353   } while (*mode_string == ',');
 354   if (*mode_string == 0)
 355     return head;
 356 invalid:
 357   mode_free (head);
 358   return MODE_INVALID;
 359 }
 360
 361 /* Return a file mode change operation that sets permissions to match those
 362    of REF_FILE.  Return MODE_BAD_REFERENCE if REF_FILE can't be accessed.  */
 363
 364 struct mode_change *
 365 mode_create_from_ref (const char *ref_file)
 366 {
 367   struct mode_change *change;   /* the only change element */
 368   struct stat ref_stats;
 369
 370   if (stat (ref_file, &ref_stats))
 371     return MODE_BAD_REFERENCE;
 372
 373   change = talloc (struct mode_change);
 374
 375   if (change == NULL)
 376     return MODE_MEMORY_EXHAUSTED;
 377
 378   change->op = '=';
 379   change->flags = 0;
 380   change->affected = CHMOD_MODE_BITS;
 381   change->value = ref_stats.st_mode;
 382   change->next = NULL;
 383
 384   return change;
 385 }
 386
 387 /* Return file mode OLDMODE, adjusted as indicated by the list of change
 388    operations CHANGES.  If OLDMODE is a directory, the type `X'
 389    change affects it even if no execute bits were set in OLDMODE.
 390    The returned value has the S_IFMT bits cleared. */
 391
 392 mode_t
 393 mode_adjust (mode_t oldmode, const struct mode_change *changes)
 394 {
 395   mode_t newmode;       /* The adjusted mode and one operand. */
 396   mode_t value;         /* The other operand. */
 397
 398   newmode = oldmode & CHMOD_MODE_BITS;
 399
 400   for (; changes; changes = changes->next)
 401     {
 402       if (changes->flags & MODE_COPY_EXISTING)
 403         {
 404           /* Isolate in `value' the bits in `newmode' to copy, given in
 405              the mask `changes->value'. */
 406           value = newmode & changes->value;
 407
 408           if (changes->value & S_IRWXU)
 409             /* Copy `u' permissions onto `g' and `o'. */
 410             value |= (  (value & S_IRUSR ? S_IRGRP | S_IROTH : 0)
 411                       | (value & S_IWUSR ? S_IWGRP | S_IWOTH : 0)
 412                       | (value & S_IXUSR ? S_IXGRP | S_IXOTH : 0));
 413           else if (changes->value & S_IRWXG)
 414             /* Copy `g' permissions onto `u' and `o'. */
 415             value |= (  (value & S_IRGRP ? S_IRUSR | S_IROTH : 0)
 416                       | (value & S_IWGRP ? S_IWUSR | S_IWOTH : 0)
 417                       | (value & S_IXGRP ? S_IXUSR | S_IXOTH : 0));
 418           else
 419             /* Copy `o' permissions onto `u' and `g'. */
 420             value |= (  (value & S_IROTH ? S_IRUSR | S_IRGRP : 0)
 421                       | (value & S_IWOTH ? S_IWUSR | S_IWGRP : 0)
 422                       | (value & S_IXOTH ? S_IXUSR | S_IXGRP : 0));
 423
 424           /* In order to change only `u', `g', or `o' permissions,
 425              or some combination thereof, clear unselected bits.
 426              This cannot be done in mode_compile because the value
 427              to which the `changes->affected' mask is applied depends
 428              on the old mode of each file. */
 429           value &= changes->affected;
 430         }
 431       else
 432         {
 433           value = changes->value;
 434           /* If `X', do not affect the execute bits if the file is not a
 435              directory and no execute bits are already set. */
 436           if ((changes->flags & MODE_X_IF_ANY_X)
 437               && !S_ISDIR (oldmode)
 438               && (newmode & (S_IXUSR | S_IXGRP | S_IXOTH)) == 0)
 439             /* Clear the execute bits. */
 440             value &= ~ (S_IXUSR | S_IXGRP | S_IXOTH);
 441         }
 442
 443       switch (changes->op)
 444         {
 445         case '=':
 446           /* Preserve the previous values in `newmode' of bits that are
 447              not affected by this change operation. */
 448           newmode = (newmode & ~changes->affected) | value;
 449           break;
 450         case '+':
 451           newmode |= value;
 452           break;
 453         case '-':
 454           newmode &= ~value;
 455           break;
 456         }
 457     }
 458   return newmode;
 459 }
 460
 461 /* Free the memory used by the list of file mode change operations
 462    CHANGES. */
 463
 464 void
 465 mode_free (register struct mode_change *changes)
 466 {
 467   register struct mode_change *next;
 468
 469   while (changes)
 470     {
 471       next = changes->next;
 472       free (changes);
 473       changes = next;
 474     }
 475 }