lib/modechange.c

   1 /* modechange.c -- file mode manipulation
   2    Copyright (C) 1989, 1990, 1997 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@ai.mit.edu> */
  19
  20 /* The ASCII mode string is compiled into a linked list of `struct
  21    modechange', which can then be applied to each file to be changed.
  22    We do this instead of re-parsing the ASCII string for each file
  23    because the compiled form requires less computation to use; when
  24    changing the mode of many files, this probably results in a
  25    performance gain. */
  26
  27 #if HAVE_CONFIG_H
  28 # include <config.h>
  29 #endif
  30
  31 #include <sys/types.h>
  32 #include <sys/stat.h>
  33 #include "modechange.h"
  34
  35 #if STDC_HEADERS
  36 # include <stdlib.h>
  37 #else
  38 char *malloc ();
  39 #endif
  40
  41 #ifndef NULL
  42 # define NULL 0
  43 #endif
  44
  45 #if STAT_MACROS_BROKEN
  46 # undef S_ISDIR
  47 #endif
  48
  49 #if !defined(S_ISDIR) && defined(S_IFDIR)
  50 # define S_ISDIR(m) (((m) & S_IFMT) == S_IFDIR)
  51 #endif
  52
  53 /* Return newly allocated memory to hold one element of type TYPE. */
  54 #define talloc(type) ((type *) malloc (sizeof (type)))
  55
  56 #define isodigit(c) ((c) >= '0' && (c) <= '7')
  57
  58 static int oatoi ();
  59
  60 /* Return a linked list of file mode change operations created from
  61    MODE_STRING, an ASCII string that contains either an octal number
  62    specifying an absolute mode, or symbolic mode change operations with
  63    the form:
  64    [ugoa...][[+-=][rwxXstugo...]...][,...]
  65    MASKED_OPS is a bitmask indicating which symbolic mode operators (=+-)
  66    should not affect bits set in the umask when no users are given.
  67    Operators not selected in MASKED_OPS ignore the umask.
  68
  69    Return MODE_INVALID if `mode_string' does not contain a valid
  70    representation of file mode change operations;
  71    return MODE_MEMORY_EXHAUSTED if there is insufficient memory. */
  72
  73 struct mode_change *
  74 mode_compile (mode_string, masked_ops)
  75      const char *mode_string;
  76      unsigned masked_ops;
  77 {
  78   struct mode_change *head;     /* First element of the linked list. */
  79   struct mode_change *change;   /* An element of the linked list. */
  80   int i;                        /* General purpose temporary. */
  81   int umask_value;              /* The umask value (surprise). */
  82   unsigned short affected_bits; /* Which bits in the mode are operated on. */
  83   unsigned short affected_masked; /* `affected_bits' modified by umask. */
  84   unsigned ops_to_mask;         /* Operators to actually use umask on. */
  85
  86   i = oatoi (mode_string);
  87   if (i >= 0)
  88     {
  89       if (i > 07777)
  90         return MODE_INVALID;
  91       head = talloc (struct mode_change);
  92       if (head == NULL)
  93         return MODE_MEMORY_EXHAUSTED;
  94       head->next = NULL;
  95       head->op = '=';
  96       head->flags = 0;
  97       head->value = i;
  98       head->affected = 07777;   /* Affect all permissions. */
  99       return head;
 100     }
 101
 102   umask_value = umask (0);
 103   umask (umask_value);          /* Restore the old value. */
 104
 105   head = NULL;
 106 #ifdef lint
 107   change = NULL;
 108 #endif
 109   --mode_string;
 110
 111   /* One loop iteration for each "ugoa...=+-rwxXstugo...[=+-rwxXstugo...]". */
 112   do
 113     {
 114       affected_bits = 0;
 115       ops_to_mask = 0;
 116       /* Turn on all the bits in `affected_bits' for each group given. */
 117       for (++mode_string;; ++mode_string)
 118         switch (*mode_string)
 119           {
 120           case 'u':
 121             affected_bits |= 04700;
 122             break;
 123           case 'g':
 124             affected_bits |= 02070;
 125             break;
 126           case 'o':
 127             affected_bits |= 01007;
 128             break;
 129           case 'a':
 130             affected_bits |= 07777;
 131             break;
 132           default:
 133             goto no_more_affected;
 134           }
 135
 136     no_more_affected:
 137       /* If none specified, affect all bits, except perhaps those
 138          set in the umask. */
 139       if (affected_bits == 0)
 140         {
 141           affected_bits = 07777;
 142           ops_to_mask = masked_ops;
 143         }
 144
 145       while (*mode_string == '=' || *mode_string == '+' || *mode_string == '-')
 146         {
 147           /* Add the element to the tail of the list, so the operations
 148              are performed in the correct order. */
 149           if (head == NULL)
 150             {
 151               head = talloc (struct mode_change);
 152               if (head == NULL)
 153                 return MODE_MEMORY_EXHAUSTED;
 154               change = head;
 155             }
 156           else
 157             {
 158               change->next = talloc (struct mode_change);
 159               if (change->next == NULL)
 160                 {
 161                   mode_free (change);
 162                   return MODE_MEMORY_EXHAUSTED;
 163                 }
 164               change = change->next;
 165             }
 166
 167           change->next = NULL;
 168           change->op = *mode_string;    /* One of "=+-". */
 169           affected_masked = affected_bits;
 170           if (ops_to_mask & (*mode_string == '=' ? MODE_MASK_EQUALS
 171                              : *mode_string == '+' ? MODE_MASK_PLUS
 172                              : MODE_MASK_MINUS))
 173             affected_masked &= ~umask_value;
 174           change->affected = affected_masked;
 175           change->value = 0;
 176           change->flags = 0;
 177
 178           /* Set `value' according to the bits set in `affected_masked'. */
 179           for (++mode_string;; ++mode_string)
 180             switch (*mode_string)
 181               {
 182               case 'r':
 183                 change->value |= 00444 & affected_masked;
 184                 break;
 185               case 'w':
 186                 change->value |= 00222 & affected_masked;
 187                 break;
 188               case 'X':
 189                 change->flags |= MODE_X_IF_ANY_X;
 190                 /* Fall through. */
 191               case 'x':
 192                 change->value |= 00111 & affected_masked;
 193                 break;
 194               case 's':
 195                 /* Set the setuid/gid bits if `u' or `g' is selected. */
 196                 change->value |= 06000 & affected_masked;
 197                 break;
 198               case 't':
 199                 /* Set the "save text image" bit if `o' is selected. */
 200                 change->value |= 01000 & affected_masked;
 201                 break;
 202               case 'u':
 203                 /* Set the affected bits to the value of the `u' bits
 204                    on the same file.  */
 205                 if (change->value)
 206                   goto invalid;
 207                 change->value = 00700;
 208                 change->flags |= MODE_COPY_EXISTING;
 209                 break;
 210               case 'g':
 211                 /* Set the affected bits to the value of the `g' bits
 212                    on the same file.  */
 213                 if (change->value)
 214                   goto invalid;
 215                 change->value = 00070;
 216                 change->flags |= MODE_COPY_EXISTING;
 217                 break;
 218               case 'o':
 219                 /* Set the affected bits to the value of the `o' bits
 220                    on the same file.  */
 221                 if (change->value)
 222                   goto invalid;
 223                 change->value = 00007;
 224                 change->flags |= MODE_COPY_EXISTING;
 225                 break;
 226               default:
 227                 goto no_more_values;
 228               }
 229         no_more_values:;
 230         }
 231   } while (*mode_string == ',');
 232   if (*mode_string == 0)
 233     return head;
 234 invalid:
 235   mode_free (head);
 236   return MODE_INVALID;
 237 }
 238
 239 /* Return a file mode change operation that sets permissions to match those
 240    of REF_FILE.  Return MODE_BAD_REFERENCE if REF_FILE can't be accessed.  */
 241
 242 struct mode_change *
 243 mode_create_from_ref (ref_file)
 244      const char *ref_file;
 245 {
 246   struct mode_change *change;   /* the only change element */
 247   struct stat ref_stats;
 248
 249   if (stat (ref_file, &ref_stats))
 250     return MODE_BAD_REFERENCE;
 251
 252   change = talloc (struct mode_change);
 253
 254   if (change == NULL)
 255     return MODE_MEMORY_EXHAUSTED;
 256
 257   change->op = '=';
 258   change->flags = 0;
 259   change->affected = 07777;
 260   change->value = ref_stats.st_mode;
 261   change->next = NULL;
 262
 263   return change;
 264 }
 265
 266 /* Return file mode OLDMODE, adjusted as indicated by the list of change
 267    operations CHANGES.  If OLDMODE is a directory, the type `X'
 268    change affects it even if no execute bits were set in OLDMODE.
 269    The returned value has the S_IFMT bits cleared. */
 270
 271 unsigned short
 272 mode_adjust (oldmode, changes)
 273      unsigned oldmode;
 274      const struct mode_change *changes;
 275 {
 276   unsigned short newmode;       /* The adjusted mode and one operand. */
 277   unsigned short value;         /* The other operand. */
 278
 279   newmode = oldmode & 07777;
 280
 281   for (; changes; changes = changes->next)
 282     {
 283       if (changes->flags & MODE_COPY_EXISTING)
 284         {
 285           /* Isolate in `value' the bits in `newmode' to copy, given in
 286              the mask `changes->value'. */
 287           value = newmode & changes->value;
 288
 289           if (changes->value & 00700)
 290             /* Copy `u' permissions onto `g' and `o'. */
 291             value |= (value >> 3) | (value >> 6);
 292           else if (changes->value & 00070)
 293             /* Copy `g' permissions onto `u' and `o'. */
 294             value |= (value << 3) | (value >> 3);
 295           else
 296             /* Copy `o' permissions onto `u' and `g'. */
 297             value |= (value << 3) | (value << 6);
 298
 299           /* In order to change only `u', `g', or `o' permissions,
 300              or some combination thereof, clear unselected bits.
 301              This can not be done in mode_compile because the value
 302              to which the `changes->affected' mask is applied depends
 303              on the old mode of each file. */
 304           value &= changes->affected;
 305         }
 306       else
 307         {
 308           value = changes->value;
 309           /* If `X', do not affect the execute bits if the file is not a
 310              directory and no execute bits are already set. */
 311           if ((changes->flags & MODE_X_IF_ANY_X)
 312               && !S_ISDIR (oldmode)
 313               && (newmode & 00111) == 0)
 314             value &= ~00111;    /* Clear the execute bits. */
 315         }
 316
 317       switch (changes->op)
 318         {
 319         case '=':
 320           /* Preserve the previous values in `newmode' of bits that are
 321              not affected by this change operation. */
 322           newmode = (newmode & ~changes->affected) | value;
 323           break;
 324         case '+':
 325           newmode |= value;
 326           break;
 327         case '-':
 328           newmode &= ~value;
 329           break;
 330         }
 331     }
 332   return newmode;
 333 }
 334
 335 /* Free the memory used by the list of file mode change operations
 336    CHANGES. */
 337
 338 void
 339 mode_free (changes)
 340      register struct mode_change *changes;
 341 {
 342   register struct mode_change *next;
 343
 344   while (changes)
 345     {
 346       next = changes->next;
 347       free (changes);
 348       changes = next;
 349     }
 350 }
 351
 352 /* Return a positive integer containing the value of the ASCII
 353    octal number S.  If S is not an octal number, return -1.  */
 354
 355 static int
 356 oatoi (s)
 357      char *s;
 358 {
 359   register int i;
 360
 361   if (*s == 0)
 362     return -1;
 363   for (i = 0; isodigit (*s); ++s)
 364     i = i * 8 + *s - '0';
 365   if (*s)
 366     return -1;
 367   return i;
 368 }