| 1 | /* provide consistent interface to chown for systems that don't interpret
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| 2 | an ID of -1 as meaning `don't change the corresponding ID'.
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| 3 |
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| 4 | Copyright (C) 1997, 2004, 2005, 2006 Free Software Foundation, Inc.
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| 5 |
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| 6 | This program is free software; you can redistribute it and/or modify
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| 7 | it under the terms of the GNU General Public License as published by
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| 8 | the Free Software Foundation; either version 2, or (at your option)
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| 9 | any later version.
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| 10 |
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| 11 | This program is distributed in the hope that it will be useful,
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| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 14 | GNU General Public License for more details.
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| 15 |
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| 16 | You should have received a copy of the GNU General Public License
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| 17 | along with this program; if not, write to the Free Software Foundation,
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| 18 | Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
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| 19 |
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| 20 | /* written by Jim Meyering */
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| 21 |
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| 22 | #include <config.h>
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| 23 |
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| 24 | /* Disable the definition of chown to rpl_chown (from config.h) in this
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| 25 | file. Otherwise, we'd get conflicting prototypes for rpl_chown on
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| 26 | most systems. */
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| 27 | #undef chown
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| 28 |
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| 29 | #include <stdbool.h>
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| 30 | #include <sys/types.h>
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| 31 | #include <sys/stat.h>
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| 32 | #include <unistd.h>
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| 33 | #include <fcntl.h>
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| 34 | #include <errno.h>
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| 35 |
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| 36 | /* Provide a more-closely POSIX-conforming version of chown on
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| 37 | systems with one or both of the following problems:
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| 38 | - chown doesn't treat an ID of -1 as meaning
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| 39 | `don't change the corresponding ID'.
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| 40 | - chown doesn't dereference symlinks. */
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| 41 |
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| 42 | int
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| 43 | rpl_chown (const char *file, uid_t uid, gid_t gid)
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| 44 | {
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| 45 | #if CHOWN_FAILS_TO_HONOR_ID_OF_NEGATIVE_ONE
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| 46 | if (gid == (gid_t) -1 || uid == (uid_t) -1)
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| 47 | {
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| 48 | struct stat file_stats;
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| 49 |
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| 50 | /* Stat file to get id(s) that should remain unchanged. */
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| 51 | if (stat (file, &file_stats))
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| 52 | return -1;
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| 53 |
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| 54 | if (gid == (gid_t) -1)
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| 55 | gid = file_stats.st_gid;
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| 56 |
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| 57 | if (uid == (uid_t) -1)
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| 58 | uid = file_stats.st_uid;
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| 59 | }
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| 60 | #endif
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| 61 |
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| 62 | #if CHOWN_MODIFIES_SYMLINK
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| 63 | {
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| 64 | /* Handle the case in which the system-supplied chown function
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| 65 | does *not* follow symlinks. Instead, it changes permissions
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| 66 | on the symlink itself. To work around that, we open the
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| 67 | file (but this can fail due to lack of read or write permission) and
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| 68 | use fchown on the resulting descriptor. */
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| 69 | int open_flags = O_NONBLOCK | O_NOCTTY;
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| 70 | int fd = open (file, O_RDONLY | open_flags);
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| 71 | if (0 <= fd
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| 72 | || (errno == EACCES
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| 73 | && 0 <= (fd = open (file, O_WRONLY | open_flags))))
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| 74 | {
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| 75 | int result = fchown (fd, uid, gid);
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| 76 | int saved_errno = errno;
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| 77 |
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| 78 | /* POSIX says fchown can fail with errno == EINVAL on sockets,
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| 79 | so fall back on chown in that case. */
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| 80 | struct stat sb;
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| 81 | bool fchown_socket_failure =
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| 82 | (result != 0 && saved_errno == EINVAL
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| 83 | && fstat (fd, &sb) == 0 && S_ISFIFO (sb.st_mode));
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| 84 |
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| 85 | close (fd);
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| 86 |
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| 87 | if (! fchown_socket_failure)
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| 88 | {
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| 89 | errno = saved_errno;
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| 90 | return result;
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| 91 | }
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| 92 | }
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| 93 | else if (errno != EACCES)
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| 94 | return -1;
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| 95 | }
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| 96 | #endif
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| 97 |
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| 98 | return chown (file, uid, gid);
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| 99 | }
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