356 lines
10 KiB
C
356 lines
10 KiB
C
/* Return the canonical absolute name of a given file.
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Copyright (C) 1996-2020 Free Software Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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#include <config.h>
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#include "canonicalize.h"
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "areadlink.h"
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#include "file-set.h"
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#include "hash-triple.h"
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#include "pathmax.h"
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#include "xalloc.h"
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#include "xgetcwd.h"
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#include "dosname.h"
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#define MULTIPLE_BITS_SET(i) (((i) & ((i) - 1)) != 0)
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/* In this file, we cannot handle file names longer than PATH_MAX.
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On systems with no file name length limit, use a fallback. */
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#ifndef PATH_MAX
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# define PATH_MAX 8192
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#endif
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#ifndef DOUBLE_SLASH_IS_DISTINCT_ROOT
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# define DOUBLE_SLASH_IS_DISTINCT_ROOT 0
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#endif
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#if ISSLASH ('\\')
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# define SLASHES "/\\"
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#else
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# define SLASHES "/"
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#endif
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#if !((HAVE_CANONICALIZE_FILE_NAME && FUNC_REALPATH_WORKS) \
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|| GNULIB_CANONICALIZE_LGPL)
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/* Return the canonical absolute name of file NAME. A canonical name
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does not contain any ".", ".." components nor any repeated file name
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separators ('/') or symlinks. All components must exist.
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The result is malloc'd. */
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char *
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canonicalize_file_name (const char *name)
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{
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return canonicalize_filename_mode (name, CAN_EXISTING);
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}
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#endif /* !HAVE_CANONICALIZE_FILE_NAME */
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/* Return true if we've already seen the triple, <FILENAME, dev, ino>.
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If *HT is not initialized, initialize it. */
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static bool
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seen_triple (Hash_table **ht, char const *filename, struct stat const *st)
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{
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if (*ht == NULL)
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{
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size_t initial_capacity = 7;
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*ht = hash_initialize (initial_capacity,
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NULL,
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triple_hash,
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triple_compare_ino_str,
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triple_free);
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if (*ht == NULL)
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xalloc_die ();
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}
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if (seen_file (*ht, filename, st))
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return true;
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record_file (*ht, filename, st);
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return false;
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}
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/* Return the canonical absolute name of file NAME, while treating
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missing elements according to CAN_MODE. A canonical name
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does not contain any ".", ".." components nor any repeated file name
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separators ('/') or, depending on other CAN_MODE flags, symlinks.
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Whether components must exist or not depends on canonicalize mode.
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The result is malloc'd. */
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char *
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canonicalize_filename_mode (const char *name, canonicalize_mode_t can_mode)
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{
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char *rname, *dest, *extra_buf = NULL;
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char const *start;
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char const *end;
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char const *rname_limit;
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size_t extra_len = 0;
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Hash_table *ht = NULL;
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int saved_errno;
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int can_flags = can_mode & ~CAN_MODE_MASK;
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bool logical = can_flags & CAN_NOLINKS;
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size_t prefix_len;
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can_mode &= CAN_MODE_MASK;
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if (MULTIPLE_BITS_SET (can_mode))
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{
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errno = EINVAL;
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return NULL;
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}
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if (name == NULL)
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{
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errno = EINVAL;
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return NULL;
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}
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if (name[0] == '\0')
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{
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errno = ENOENT;
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return NULL;
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}
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/* This is always zero for Posix hosts, but can be 2 for MS-Windows
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and MS-DOS X:/foo/bar file names. */
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prefix_len = FILE_SYSTEM_PREFIX_LEN (name);
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if (!IS_ABSOLUTE_FILE_NAME (name))
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{
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rname = xgetcwd ();
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if (!rname)
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return NULL;
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dest = strchr (rname, '\0');
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if (dest - rname < PATH_MAX)
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{
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char *p = xrealloc (rname, PATH_MAX);
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dest = p + (dest - rname);
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rname = p;
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rname_limit = rname + PATH_MAX;
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}
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else
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{
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rname_limit = dest;
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}
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start = name;
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prefix_len = FILE_SYSTEM_PREFIX_LEN (rname);
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}
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else
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{
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rname = xmalloc (PATH_MAX);
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rname_limit = rname + PATH_MAX;
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dest = rname;
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if (prefix_len)
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{
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memcpy (rname, name, prefix_len);
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dest += prefix_len;
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}
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*dest++ = '/';
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if (DOUBLE_SLASH_IS_DISTINCT_ROOT)
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{
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if (ISSLASH (name[1]) && !ISSLASH (name[2]) && !prefix_len)
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*dest++ = '/';
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*dest = '\0';
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}
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start = name + prefix_len;
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}
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for ( ; *start; start = end)
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{
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/* Skip sequence of multiple file name separators. */
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while (ISSLASH (*start))
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++start;
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/* Find end of component. */
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for (end = start; *end && !ISSLASH (*end); ++end)
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/* Nothing. */;
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if (end - start == 0)
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break;
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else if (end - start == 1 && start[0] == '.')
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/* nothing */;
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else if (end - start == 2 && start[0] == '.' && start[1] == '.')
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{
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/* Back up to previous component, ignore if at root already. */
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if (dest > rname + prefix_len + 1)
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for (--dest; dest > rname && !ISSLASH (dest[-1]); --dest)
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continue;
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if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rname + 1
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&& !prefix_len && ISSLASH (*dest) && !ISSLASH (dest[1]))
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dest++;
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}
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else
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{
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struct stat st;
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if (!ISSLASH (dest[-1]))
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*dest++ = '/';
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if (dest + (end - start) >= rname_limit)
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{
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ptrdiff_t dest_offset = dest - rname;
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size_t new_size = rname_limit - rname;
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if (end - start + 1 > PATH_MAX)
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new_size += end - start + 1;
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else
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new_size += PATH_MAX;
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rname = xrealloc (rname, new_size);
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rname_limit = rname + new_size;
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dest = rname + dest_offset;
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}
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dest = memcpy (dest, start, end - start);
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dest += end - start;
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*dest = '\0';
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if (logical && (can_mode == CAN_MISSING))
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{
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/* Avoid the stat in this case as it's inconsequential.
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i.e. we're neither resolving symlinks or testing
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component existence. */
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st.st_mode = 0;
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}
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else if ((logical ? stat (rname, &st) : lstat (rname, &st)) != 0)
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{
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/* FIXME: If errno == EOVERFLOW here, the entry exists. */
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saved_errno = errno;
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if (can_mode == CAN_EXISTING)
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goto error;
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if (can_mode == CAN_ALL_BUT_LAST)
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{
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if (end[strspn (end, SLASHES)] || saved_errno != ENOENT)
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goto error;
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continue;
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}
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st.st_mode = 0;
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}
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if (S_ISLNK (st.st_mode))
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{
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char *buf;
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size_t n, len;
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/* Detect loops. We cannot use the cycle-check module here,
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since it's actually possible to encounter the same symlink
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more than once in a given traversal. However, encountering
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the same symlink,NAME pair twice does indicate a loop. */
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if (seen_triple (&ht, name, &st))
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{
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if (can_mode == CAN_MISSING)
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continue;
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saved_errno = ELOOP;
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goto error;
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}
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buf = areadlink_with_size (rname, st.st_size);
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if (!buf)
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{
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if (can_mode == CAN_MISSING && errno != ENOMEM)
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continue;
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saved_errno = errno;
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goto error;
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}
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n = strlen (buf);
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len = strlen (end);
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if (!extra_len)
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{
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extra_len =
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((n + len + 1) > PATH_MAX) ? (n + len + 1) : PATH_MAX;
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extra_buf = xmalloc (extra_len);
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}
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else if ((n + len + 1) > extra_len)
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{
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extra_len = n + len + 1;
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extra_buf = xrealloc (extra_buf, extra_len);
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}
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/* Careful here, end may be a pointer into extra_buf... */
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memmove (&extra_buf[n], end, len + 1);
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name = end = memcpy (extra_buf, buf, n);
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if (IS_ABSOLUTE_FILE_NAME (buf))
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{
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size_t pfxlen = FILE_SYSTEM_PREFIX_LEN (buf);
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if (pfxlen)
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memcpy (rname, buf, pfxlen);
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dest = rname + pfxlen;
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*dest++ = '/'; /* It's an absolute symlink */
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if (DOUBLE_SLASH_IS_DISTINCT_ROOT)
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{
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if (ISSLASH (buf[1]) && !ISSLASH (buf[2]) && !pfxlen)
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*dest++ = '/';
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*dest = '\0';
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}
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/* Install the new prefix to be in effect hereafter. */
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prefix_len = pfxlen;
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}
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else
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{
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/* Back up to previous component, ignore if at root
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already: */
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if (dest > rname + prefix_len + 1)
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for (--dest; dest > rname && !ISSLASH (dest[-1]); --dest)
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continue;
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if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rname + 1
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&& ISSLASH (*dest) && !ISSLASH (dest[1]) && !prefix_len)
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dest++;
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}
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free (buf);
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}
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else
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{
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if (!S_ISDIR (st.st_mode) && *end && (can_mode != CAN_MISSING))
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{
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saved_errno = ENOTDIR;
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goto error;
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}
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}
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}
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}
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if (dest > rname + prefix_len + 1 && ISSLASH (dest[-1]))
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--dest;
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if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rname + 1 && !prefix_len
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&& ISSLASH (*dest) && !ISSLASH (dest[1]))
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dest++;
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*dest = '\0';
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if (rname_limit != dest + 1)
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rname = xrealloc (rname, dest - rname + 1);
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free (extra_buf);
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if (ht)
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hash_free (ht);
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return rname;
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error:
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free (extra_buf);
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free (rname);
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if (ht)
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hash_free (ht);
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errno = saved_errno;
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return NULL;
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}
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