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Diffstat (limited to 'lib/modechange.c')
| -rw-r--r-- | lib/modechange.c | 414 |
1 files changed, 414 insertions, 0 deletions
diff --git a/lib/modechange.c b/lib/modechange.c new file mode 100644 index 0000000..800bbf6 --- /dev/null +++ b/lib/modechange.c @@ -0,0 +1,414 @@ +/* modechange.c -- file mode manipulation + + Copyright (C) 1989-1990, 1997-1999, 2001, 2003-2006, 2009-2020 Free Software + Foundation, Inc. + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. */ + +/* Written by David MacKenzie <djm@ai.mit.edu> */ + +/* The ASCII mode string is compiled into an array of 'struct + modechange', which can then be applied to each file to be changed. + We do this instead of re-parsing the ASCII string for each file + because the compiled form requires less computation to use; when + changing the mode of many files, this probably results in a + performance gain. */ + +#include <config.h> + +#include "modechange.h" +#include <sys/stat.h> +#include "stat-macros.h" +#include "xalloc.h" +#include <stdlib.h> + +/* The traditional octal values corresponding to each mode bit. */ +#define SUID 04000 +#define SGID 02000 +#define SVTX 01000 +#define RUSR 00400 +#define WUSR 00200 +#define XUSR 00100 +#define RGRP 00040 +#define WGRP 00020 +#define XGRP 00010 +#define ROTH 00004 +#define WOTH 00002 +#define XOTH 00001 +#define ALLM 07777 /* all octal mode bits */ + +/* Convert OCTAL, which uses one of the traditional octal values, to + an internal mode_t value. */ +static mode_t +octal_to_mode (unsigned int octal) +{ + /* Help the compiler optimize the usual case where mode_t uses + the traditional octal representation. */ + return ((S_ISUID == SUID && S_ISGID == SGID && S_ISVTX == SVTX + && S_IRUSR == RUSR && S_IWUSR == WUSR && S_IXUSR == XUSR + && S_IRGRP == RGRP && S_IWGRP == WGRP && S_IXGRP == XGRP + && S_IROTH == ROTH && S_IWOTH == WOTH && S_IXOTH == XOTH) + ? octal + : (mode_t) ((octal & SUID ? S_ISUID : 0) + | (octal & SGID ? S_ISGID : 0) + | (octal & SVTX ? S_ISVTX : 0) + | (octal & RUSR ? S_IRUSR : 0) + | (octal & WUSR ? S_IWUSR : 0) + | (octal & XUSR ? S_IXUSR : 0) + | (octal & RGRP ? S_IRGRP : 0) + | (octal & WGRP ? S_IWGRP : 0) + | (octal & XGRP ? S_IXGRP : 0) + | (octal & ROTH ? S_IROTH : 0) + | (octal & WOTH ? S_IWOTH : 0) + | (octal & XOTH ? S_IXOTH : 0))); +} + +/* Special operations flags. */ +enum + { + /* For the sentinel at the end of the mode changes array. */ + MODE_DONE, + + /* The typical case. */ + MODE_ORDINARY_CHANGE, + + /* In addition to the typical case, affect the execute bits if at + least one execute bit is set already, or if the file is a + directory. */ + MODE_X_IF_ANY_X, + + /* Instead of the typical case, copy some existing permissions for + u, g, or o onto the other two. Which of u, g, or o is copied + is determined by which bits are set in the 'value' field. */ + MODE_COPY_EXISTING + }; + +/* Description of a mode change. */ +struct mode_change +{ + char op; /* One of "=+-". */ + char flag; /* Special operations flag. */ + mode_t affected; /* Set for u, g, o, or a. */ + mode_t value; /* Bits to add/remove. */ + mode_t mentioned; /* Bits explicitly mentioned. */ +}; + +/* Return a mode_change array with the specified "=ddd"-style + mode change operation, where NEW_MODE is "ddd" and MENTIONED + contains the bits explicitly mentioned in the mode are MENTIONED. */ + +static struct mode_change * +make_node_op_equals (mode_t new_mode, mode_t mentioned) +{ + struct mode_change *p = xmalloc (2 * sizeof *p); + p->op = '='; + p->flag = MODE_ORDINARY_CHANGE; + p->affected = CHMOD_MODE_BITS; + p->value = new_mode; + p->mentioned = mentioned; + p[1].flag = MODE_DONE; + return p; +} + +/* Return a pointer to an array of file mode change operations created from + MODE_STRING, an ASCII string that contains either an octal number + specifying an absolute mode, or symbolic mode change operations with + the form: + [ugoa...][[+-=][rwxXstugo...]...][,...] + + Return NULL if 'mode_string' does not contain a valid + representation of file mode change operations. */ + +struct mode_change * +mode_compile (char const *mode_string) +{ + /* The array of mode-change directives to be returned. */ + struct mode_change *mc; + size_t used = 0; + char const *p; + + if ('0' <= *mode_string && *mode_string < '8') + { + unsigned int octal_mode = 0; + mode_t mode; + mode_t mentioned; + + p = mode_string; + do + { + octal_mode = 8 * octal_mode + *p++ - '0'; + if (ALLM < octal_mode) + return NULL; + } + while ('0' <= *p && *p < '8'); + + if (*p) + return NULL; + + mode = octal_to_mode (octal_mode); + mentioned = (p - mode_string < 5 + ? (mode & (S_ISUID | S_ISGID)) | S_ISVTX | S_IRWXUGO + : CHMOD_MODE_BITS); + return make_node_op_equals (mode, mentioned); + } + + /* Allocate enough space to hold the result. */ + { + size_t needed = 1; + for (p = mode_string; *p; p++) + needed += (*p == '=' || *p == '+' || *p == '-'); + mc = xnmalloc (needed, sizeof *mc); + } + + /* One loop iteration for each + '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'. */ + for (p = mode_string; ; p++) + { + /* Which bits in the mode are operated on. */ + mode_t affected = 0; + + /* Turn on all the bits in 'affected' for each group given. */ + for (;; p++) + switch (*p) + { + default: + goto invalid; + case 'u': + affected |= S_ISUID | S_IRWXU; + break; + case 'g': + affected |= S_ISGID | S_IRWXG; + break; + case 'o': + affected |= S_ISVTX | S_IRWXO; + break; + case 'a': + affected |= CHMOD_MODE_BITS; + break; + case '=': case '+': case '-': + goto no_more_affected; + } + no_more_affected:; + + do + { + char op = *p++; + mode_t value; + mode_t mentioned = 0; + char flag = MODE_COPY_EXISTING; + struct mode_change *change; + + switch (*p) + { + case '0': case '1': case '2': case '3': + case '4': case '5': case '6': case '7': + { + unsigned int octal_mode = 0; + + do + { + octal_mode = 8 * octal_mode + *p++ - '0'; + if (ALLM < octal_mode) + goto invalid; + } + while ('0' <= *p && *p < '8'); + + if (affected || (*p && *p != ',')) + goto invalid; + affected = mentioned = CHMOD_MODE_BITS; + value = octal_to_mode (octal_mode); + flag = MODE_ORDINARY_CHANGE; + break; + } + + case 'u': + /* Set the affected bits to the value of the "u" bits + on the same file. */ + value = S_IRWXU; + p++; + break; + case 'g': + /* Set the affected bits to the value of the "g" bits + on the same file. */ + value = S_IRWXG; + p++; + break; + case 'o': + /* Set the affected bits to the value of the "o" bits + on the same file. */ + value = S_IRWXO; + p++; + break; + + default: + value = 0; + flag = MODE_ORDINARY_CHANGE; + + for (;; p++) + switch (*p) + { + case 'r': + value |= S_IRUSR | S_IRGRP | S_IROTH; + break; + case 'w': + value |= S_IWUSR | S_IWGRP | S_IWOTH; + break; + case 'x': + value |= S_IXUSR | S_IXGRP | S_IXOTH; + break; + case 'X': + flag = MODE_X_IF_ANY_X; + break; + case 's': + /* Set the setuid/gid bits if 'u' or 'g' is selected. */ + value |= S_ISUID | S_ISGID; + break; + case 't': + /* Set the "save text image" bit if 'o' is selected. */ + value |= S_ISVTX; + break; + default: + goto no_more_values; + } + no_more_values:; + } + + change = &mc[used++]; + change->op = op; + change->flag = flag; + change->affected = affected; + change->value = value; + change->mentioned = + (mentioned ? mentioned : affected ? affected & value : value); + } + while (*p == '=' || *p == '+' || *p == '-'); + + if (*p != ',') + break; + } + + if (*p == 0) + { + mc[used].flag = MODE_DONE; + return mc; + } + +invalid: + free (mc); + return NULL; +} + +/* Return a file mode change operation that sets permissions to match those + of REF_FILE. Return NULL (setting errno) if REF_FILE can't be accessed. */ + +struct mode_change * +mode_create_from_ref (const char *ref_file) +{ + struct stat ref_stats; + + if (stat (ref_file, &ref_stats) != 0) + return NULL; + return make_node_op_equals (ref_stats.st_mode, CHMOD_MODE_BITS); +} + +/* Return the file mode bits of OLDMODE (which is the mode of a + directory if DIR), assuming the umask is UMASK_VALUE, adjusted as + indicated by the list of change operations CHANGES. If DIR, the + type 'X' change affects the returned value even if no execute bits + were set in OLDMODE, and set user and group ID bits are preserved + unless CHANGES mentioned them. If PMODE_BITS is not null, store into + *PMODE_BITS a mask denoting file mode bits that are affected by + CHANGES. + + The returned value and *PMODE_BITS contain only file mode bits. + For example, they have the S_IFMT bits cleared on a standard + Unix-like host. */ + +mode_t +mode_adjust (mode_t oldmode, bool dir, mode_t umask_value, + struct mode_change const *changes, mode_t *pmode_bits) +{ + /* The adjusted mode. */ + mode_t newmode = oldmode & CHMOD_MODE_BITS; + + /* File mode bits that CHANGES cares about. */ + mode_t mode_bits = 0; + + for (; changes->flag != MODE_DONE; changes++) + { + mode_t affected = changes->affected; + mode_t omit_change = + (dir ? S_ISUID | S_ISGID : 0) & ~ changes->mentioned; + mode_t value = changes->value; + + switch (changes->flag) + { + case MODE_ORDINARY_CHANGE: + break; + + case MODE_COPY_EXISTING: + /* Isolate in 'value' the bits in 'newmode' to copy. */ + value &= newmode; + + /* Copy the isolated bits to the other two parts. */ + value |= ((value & (S_IRUSR | S_IRGRP | S_IROTH) + ? S_IRUSR | S_IRGRP | S_IROTH : 0) + | (value & (S_IWUSR | S_IWGRP | S_IWOTH) + ? S_IWUSR | S_IWGRP | S_IWOTH : 0) + | (value & (S_IXUSR | S_IXGRP | S_IXOTH) + ? S_IXUSR | S_IXGRP | S_IXOTH : 0)); + break; + + case MODE_X_IF_ANY_X: + /* Affect the execute bits if execute bits are already set + or if the file is a directory. */ + if ((newmode & (S_IXUSR | S_IXGRP | S_IXOTH)) | dir) + value |= S_IXUSR | S_IXGRP | S_IXOTH; + break; + } + + /* If WHO was specified, limit the change to the affected bits. + Otherwise, apply the umask. Either way, omit changes as + requested. */ + value &= (affected ? affected : ~umask_value) & ~ omit_change; + + switch (changes->op) + { + case '=': + /* If WHO was specified, preserve the previous values of + bits that are not affected by this change operation. + Otherwise, clear all the bits. */ + { + mode_t preserved = (affected ? ~affected : 0) | omit_change; + mode_bits |= CHMOD_MODE_BITS & ~preserved; + newmode = (newmode & preserved) | value; + break; + } + + case '+': + mode_bits |= value; + newmode |= value; + break; + + case '-': + mode_bits |= value; + newmode &= ~value; + break; + } + } + + if (pmode_bits) + *pmode_bits = mode_bits; + return newmode; +} |