lib/modechange.c

   1 /* modechange.c -- file mode manipulation
   2    Copyright (C) 1989, 1990, 1997, 1998 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 /* Return a positive integer containing the value of the ASCII
  59    octal number S.  If S is not an octal number, return -1.  */
  60
  61 static int
  62 oatoi (const char *s)
  63 {
  64   register int i;
  65
  66   if (*s == 0)
  67     return -1;
  68   for (i = 0; isodigit (*s); ++s)
  69     i = i * 8 + *s - '0';
  70   if (*s)
  71     return -1;
  72   return i;
  73 }
  74
  75 /* Return a linked list of file mode change operations created from
  76    MODE_STRING, an ASCII string that contains either an octal number
  77    specifying an absolute mode, or symbolic mode change operations with
  78    the form:
  79    [ugoa...][[+-=][rwxXstugo...]...][,...]
  80    MASKED_OPS is a bitmask indicating which symbolic mode operators (=+-)
  81    should not affect bits set in the umask when no users are given.
  82    Operators not selected in MASKED_OPS ignore the umask.
  83
  84    Return MODE_INVALID if `mode_string' does not contain a valid
  85    representation of file mode change operations;
  86    return MODE_MEMORY_EXHAUSTED if there is insufficient memory. */
  87
  88 struct mode_change *
  89 mode_compile (const char *mode_string, unsigned int masked_ops)
  90 {
  91   struct mode_change *head;     /* First element of the linked list. */
  92   struct mode_change *change;   /* An element of the linked list. */
  93   int i;                        /* General purpose temporary. */
  94   int umask_value;              /* The umask value (surprise). */
  95   unsigned short affected_bits; /* Which bits in the mode are operated on. */
  96   unsigned short affected_masked; /* `affected_bits' modified by umask. */
  97   unsigned ops_to_mask;         /* Operators to actually use umask on. */
  98
  99   i = oatoi (mode_string);
 100   if (i >= 0)
 101     {
 102       if (i > 07777)
 103         return MODE_INVALID;
 104       head = talloc (struct mode_change);
 105       if (head == NULL)
 106         return MODE_MEMORY_EXHAUSTED;
 107       head->next = NULL;
 108       head->op = '=';
 109       head->flags = 0;
 110       head->value = i;
 111       head->affected = 07777;   /* Affect all permissions. */
 112       return head;
 113     }
 114
 115   umask_value = umask (0);
 116   umask (umask_value);          /* Restore the old value. */
 117
 118   head = NULL;
 119 #ifdef lint
 120   change = NULL;
 121 #endif
 122   --mode_string;
 123
 124   /* One loop iteration for each "ugoa...=+-rwxXstugo...[=+-rwxXstugo...]". */
 125   do
 126     {
 127       affected_bits = 0;
 128       ops_to_mask = 0;
 129       /* Turn on all the bits in `affected_bits' for each group given. */
 130       for (++mode_string;; ++mode_string)
 131         switch (*mode_string)
 132           {
 133           case 'u':
 134             affected_bits |= 04700;
 135             break;
 136           case 'g':
 137             affected_bits |= 02070;
 138             break;
 139           case 'o':
 140             affected_bits |= 01007;
 141             break;
 142           case 'a':
 143             affected_bits |= 07777;
 144             break;
 145           default:
 146             goto no_more_affected;
 147           }
 148
 149     no_more_affected:
 150       /* If none specified, affect all bits, except perhaps those
 151          set in the umask. */
 152       if (affected_bits == 0)
 153         {
 154           affected_bits = 07777;
 155           ops_to_mask = masked_ops;
 156         }
 157
 158       while (*mode_string == '=' || *mode_string == '+' || *mode_string == '-')
 159         {
 160           /* Add the element to the tail of the list, so the operations
 161              are performed in the correct order. */
 162           if (head == NULL)
 163             {
 164               head = talloc (struct mode_change);
 165               if (head == NULL)
 166                 return MODE_MEMORY_EXHAUSTED;
 167               change = head;
 168             }
 169           else
 170             {
 171               change->next = talloc (struct mode_change);
 172               if (change->next == NULL)
 173                 {
 174                   mode_free (change);
 175                   return MODE_MEMORY_EXHAUSTED;
 176                 }
 177               change = change->next;
 178             }
 179
 180           change->next = NULL;
 181           change->op = *mode_string;    /* One of "=+-". */
 182           affected_masked = affected_bits;
 183           if (ops_to_mask & (*mode_string == '=' ? MODE_MASK_EQUALS
 184                              : *mode_string == '+' ? MODE_MASK_PLUS
 185                              : MODE_MASK_MINUS))
 186             affected_masked &= ~umask_value;
 187           change->affected = affected_masked;
 188           change->value = 0;
 189           change->flags = 0;
 190
 191           /* Set `value' according to the bits set in `affected_masked'. */
 192           for (++mode_string;; ++mode_string)
 193             switch (*mode_string)
 194               {
 195               case 'r':
 196                 change->value |= 00444 & affected_masked;
 197                 break;
 198               case 'w':
 199                 change->value |= 00222 & affected_masked;
 200                 break;
 201               case 'X':
 202                 change->flags |= MODE_X_IF_ANY_X;
 203                 /* Fall through. */
 204               case 'x':
 205                 change->value |= 00111 & affected_masked;
 206                 break;
 207               case 's':
 208                 /* Set the setuid/gid bits if `u' or `g' is selected. */
 209                 change->value |= 06000 & affected_masked;
 210                 break;
 211               case 't':
 212                 /* Set the "save text image" bit if `o' is selected. */
 213                 change->value |= 01000 & affected_masked;
 214                 break;
 215               case 'u':
 216                 /* Set the affected bits to the value of the `u' bits
 217                    on the same file.  */
 218                 if (change->value)
 219                   goto invalid;
 220                 change->value = 00700;
 221                 change->flags |= MODE_COPY_EXISTING;
 222                 break;
 223               case 'g':
 224                 /* Set the affected bits to the value of the `g' bits
 225                    on the same file.  */
 226                 if (change->value)
 227                   goto invalid;
 228                 change->value = 00070;
 229                 change->flags |= MODE_COPY_EXISTING;
 230                 break;
 231               case 'o':
 232                 /* Set the affected bits to the value of the `o' bits
 233                    on the same file.  */
 234                 if (change->value)
 235                   goto invalid;
 236                 change->value = 00007;
 237                 change->flags |= MODE_COPY_EXISTING;
 238                 break;
 239               default:
 240                 goto no_more_values;
 241               }
 242         no_more_values:;
 243         }
 244   } while (*mode_string == ',');
 245   if (*mode_string == 0)
 246     return head;
 247 invalid:
 248   mode_free (head);
 249   return MODE_INVALID;
 250 }
 251
 252 /* Return a file mode change operation that sets permissions to match those
 253    of REF_FILE.  Return MODE_BAD_REFERENCE if REF_FILE can't be accessed.  */
 254
 255 struct mode_change *
 256 mode_create_from_ref (const char *ref_file)
 257 {
 258   struct mode_change *change;   /* the only change element */
 259   struct stat ref_stats;
 260
 261   if (stat (ref_file, &ref_stats))
 262     return MODE_BAD_REFERENCE;
 263
 264   change = talloc (struct mode_change);
 265
 266   if (change == NULL)
 267     return MODE_MEMORY_EXHAUSTED;
 268
 269   change->op = '=';
 270   change->flags = 0;
 271   change->affected = 07777;
 272   change->value = ref_stats.st_mode;
 273   change->next = NULL;
 274
 275   return change;
 276 }
 277
 278 /* Return file mode OLDMODE, adjusted as indicated by the list of change
 279    operations CHANGES.  If OLDMODE is a directory, the type `X'
 280    change affects it even if no execute bits were set in OLDMODE.
 281    The returned value has the S_IFMT bits cleared. */
 282
 283 unsigned short
 284 mode_adjust (unsigned int oldmode, const struct mode_change *changes)
 285 {
 286   unsigned short newmode;       /* The adjusted mode and one operand. */
 287   unsigned short value;         /* The other operand. */
 288
 289   newmode = oldmode & 07777;
 290
 291   for (; changes; changes = changes->next)
 292     {
 293       if (changes->flags & MODE_COPY_EXISTING)
 294         {
 295           /* Isolate in `value' the bits in `newmode' to copy, given in
 296              the mask `changes->value'. */
 297           value = newmode & changes->value;
 298
 299           if (changes->value & 00700)
 300             /* Copy `u' permissions onto `g' and `o'. */
 301             value |= (value >> 3) | (value >> 6);
 302           else if (changes->value & 00070)
 303             /* Copy `g' permissions onto `u' and `o'. */
 304             value |= (value << 3) | (value >> 3);
 305           else
 306             /* Copy `o' permissions onto `u' and `g'. */
 307             value |= (value << 3) | (value << 6);
 308
 309           /* In order to change only `u', `g', or `o' permissions,
 310              or some combination thereof, clear unselected bits.
 311              This can not be done in mode_compile because the value
 312              to which the `changes->affected' mask is applied depends
 313              on the old mode of each file. */
 314           value &= changes->affected;
 315         }
 316       else
 317         {
 318           value = changes->value;
 319           /* If `X', do not affect the execute bits if the file is not a
 320              directory and no execute bits are already set. */
 321           if ((changes->flags & MODE_X_IF_ANY_X)
 322               && !S_ISDIR (oldmode)
 323               && (newmode & 00111) == 0)
 324             value &= ~00111;    /* Clear the execute bits. */
 325         }
 326
 327       switch (changes->op)
 328         {
 329         case '=':
 330           /* Preserve the previous values in `newmode' of bits that are
 331              not affected by this change operation. */
 332           newmode = (newmode & ~changes->affected) | value;
 333           break;
 334         case '+':
 335           newmode |= value;
 336           break;
 337         case '-':
 338           newmode &= ~value;
 339           break;
 340         }
 341     }
 342   return newmode;
 343 }
 344
 345 /* Free the memory used by the list of file mode change operations
 346    CHANGES. */
 347
 348 void
 349 mode_free (register struct mode_change *changes)
 350 {
 351   register struct mode_change *next;
 352
 353   while (changes)
 354     {
 355       next = changes->next;
 356       free (changes);
 357       changes = next;
 358     }
 359 }