diff options
Diffstat (limited to 'lib/canonicalize.c')
| -rw-r--r-- | lib/canonicalize.c | 355 |
1 files changed, 355 insertions, 0 deletions
diff --git a/lib/canonicalize.c b/lib/canonicalize.c new file mode 100644 index 0000000..67fc76e --- /dev/null +++ b/lib/canonicalize.c @@ -0,0 +1,355 @@ +/* Return the canonical absolute name of a given file. + Copyright (C) 1996-2020 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/>. */ + +#include <config.h> + +#include "canonicalize.h" + +#include <errno.h> +#include <stdlib.h> +#include <string.h> +#include <sys/stat.h> +#include <unistd.h> + +#include "areadlink.h" +#include "file-set.h" +#include "hash-triple.h" +#include "pathmax.h" +#include "xalloc.h" +#include "xgetcwd.h" +#include "dosname.h" + +#define MULTIPLE_BITS_SET(i) (((i) & ((i) - 1)) != 0) + +/* In this file, we cannot handle file names longer than PATH_MAX. + On systems with no file name length limit, use a fallback. */ +#ifndef PATH_MAX +# define PATH_MAX 8192 +#endif + +#ifndef DOUBLE_SLASH_IS_DISTINCT_ROOT +# define DOUBLE_SLASH_IS_DISTINCT_ROOT 0 +#endif + +#if ISSLASH ('\\') +# define SLASHES "/\\" +#else +# define SLASHES "/" +#endif + +#if !((HAVE_CANONICALIZE_FILE_NAME && FUNC_REALPATH_WORKS) \ + || GNULIB_CANONICALIZE_LGPL) +/* Return the canonical absolute name of file NAME. A canonical name + does not contain any ".", ".." components nor any repeated file name + separators ('/') or symlinks. All components must exist. + The result is malloc'd. */ + +char * +canonicalize_file_name (const char *name) +{ + return canonicalize_filename_mode (name, CAN_EXISTING); +} +#endif /* !HAVE_CANONICALIZE_FILE_NAME */ + +/* Return true if we've already seen the triple, <FILENAME, dev, ino>. + If *HT is not initialized, initialize it. */ +static bool +seen_triple (Hash_table **ht, char const *filename, struct stat const *st) +{ + if (*ht == NULL) + { + size_t initial_capacity = 7; + *ht = hash_initialize (initial_capacity, + NULL, + triple_hash, + triple_compare_ino_str, + triple_free); + if (*ht == NULL) + xalloc_die (); + } + + if (seen_file (*ht, filename, st)) + return true; + + record_file (*ht, filename, st); + return false; +} + +/* Return the canonical absolute name of file NAME, while treating + missing elements according to CAN_MODE. A canonical name + does not contain any ".", ".." components nor any repeated file name + separators ('/') or, depending on other CAN_MODE flags, symlinks. + Whether components must exist or not depends on canonicalize mode. + The result is malloc'd. */ + +char * +canonicalize_filename_mode (const char *name, canonicalize_mode_t can_mode) +{ + char *rname, *dest, *extra_buf = NULL; + char const *start; + char const *end; + char const *rname_limit; + size_t extra_len = 0; + Hash_table *ht = NULL; + int saved_errno; + int can_flags = can_mode & ~CAN_MODE_MASK; + bool logical = can_flags & CAN_NOLINKS; + size_t prefix_len; + + can_mode &= CAN_MODE_MASK; + + if (MULTIPLE_BITS_SET (can_mode)) + { + errno = EINVAL; + return NULL; + } + + if (name == NULL) + { + errno = EINVAL; + return NULL; + } + + if (name[0] == '\0') + { + errno = ENOENT; + return NULL; + } + + /* This is always zero for Posix hosts, but can be 2 for MS-Windows + and MS-DOS X:/foo/bar file names. */ + prefix_len = FILE_SYSTEM_PREFIX_LEN (name); + + if (!IS_ABSOLUTE_FILE_NAME (name)) + { + rname = xgetcwd (); + if (!rname) + return NULL; + dest = strchr (rname, '\0'); + if (dest - rname < PATH_MAX) + { + char *p = xrealloc (rname, PATH_MAX); + dest = p + (dest - rname); + rname = p; + rname_limit = rname + PATH_MAX; + } + else + { + rname_limit = dest; + } + start = name; + prefix_len = FILE_SYSTEM_PREFIX_LEN (rname); + } + else + { + rname = xmalloc (PATH_MAX); + rname_limit = rname + PATH_MAX; + dest = rname; + if (prefix_len) + { + memcpy (rname, name, prefix_len); + dest += prefix_len; + } + *dest++ = '/'; + if (DOUBLE_SLASH_IS_DISTINCT_ROOT) + { + if (ISSLASH (name[1]) && !ISSLASH (name[2]) && !prefix_len) + *dest++ = '/'; + *dest = '\0'; + } + start = name + prefix_len; + } + + for ( ; *start; start = end) + { + /* Skip sequence of multiple file name separators. */ + while (ISSLASH (*start)) + ++start; + + /* Find end of component. */ + for (end = start; *end && !ISSLASH (*end); ++end) + /* Nothing. */; + + if (end - start == 0) + break; + else if (end - start == 1 && start[0] == '.') + /* nothing */; + else if (end - start == 2 && start[0] == '.' && start[1] == '.') + { + /* Back up to previous component, ignore if at root already. */ + if (dest > rname + prefix_len + 1) + for (--dest; dest > rname && !ISSLASH (dest[-1]); --dest) + continue; + if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rname + 1 + && !prefix_len && ISSLASH (*dest) && !ISSLASH (dest[1])) + dest++; + } + else + { + struct stat st; + + if (!ISSLASH (dest[-1])) + *dest++ = '/'; + + if (dest + (end - start) >= rname_limit) + { + ptrdiff_t dest_offset = dest - rname; + size_t new_size = rname_limit - rname; + + if (end - start + 1 > PATH_MAX) + new_size += end - start + 1; + else + new_size += PATH_MAX; + rname = xrealloc (rname, new_size); + rname_limit = rname + new_size; + + dest = rname + dest_offset; + } + + dest = memcpy (dest, start, end - start); + dest += end - start; + *dest = '\0'; + + if (logical && (can_mode == CAN_MISSING)) + { + /* Avoid the stat in this case as it's inconsequential. + i.e. we're neither resolving symlinks or testing + component existence. */ + st.st_mode = 0; + } + else if ((logical ? stat (rname, &st) : lstat (rname, &st)) != 0) + { + /* FIXME: If errno == EOVERFLOW here, the entry exists. */ + saved_errno = errno; + if (can_mode == CAN_EXISTING) + goto error; + if (can_mode == CAN_ALL_BUT_LAST) + { + if (end[strspn (end, SLASHES)] || saved_errno != ENOENT) + goto error; + continue; + } + st.st_mode = 0; + } + + if (S_ISLNK (st.st_mode)) + { + char *buf; + size_t n, len; + + /* Detect loops. We cannot use the cycle-check module here, + since it's actually possible to encounter the same symlink + more than once in a given traversal. However, encountering + the same symlink,NAME pair twice does indicate a loop. */ + if (seen_triple (&ht, name, &st)) + { + if (can_mode == CAN_MISSING) + continue; + saved_errno = ELOOP; + goto error; + } + + buf = areadlink_with_size (rname, st.st_size); + if (!buf) + { + if (can_mode == CAN_MISSING && errno != ENOMEM) + continue; + saved_errno = errno; + goto error; + } + + n = strlen (buf); + len = strlen (end); + + if (!extra_len) + { + extra_len = + ((n + len + 1) > PATH_MAX) ? (n + len + 1) : PATH_MAX; + extra_buf = xmalloc (extra_len); + } + else if ((n + len + 1) > extra_len) + { + extra_len = n + len + 1; + extra_buf = xrealloc (extra_buf, extra_len); + } + + /* Careful here, end may be a pointer into extra_buf... */ + memmove (&extra_buf[n], end, len + 1); + name = end = memcpy (extra_buf, buf, n); + + if (IS_ABSOLUTE_FILE_NAME (buf)) + { + size_t pfxlen = FILE_SYSTEM_PREFIX_LEN (buf); + + if (pfxlen) + memcpy (rname, buf, pfxlen); + dest = rname + pfxlen; + *dest++ = '/'; /* It's an absolute symlink */ + if (DOUBLE_SLASH_IS_DISTINCT_ROOT) + { + if (ISSLASH (buf[1]) && !ISSLASH (buf[2]) && !pfxlen) + *dest++ = '/'; + *dest = '\0'; + } + /* Install the new prefix to be in effect hereafter. */ + prefix_len = pfxlen; + } + else + { + /* Back up to previous component, ignore if at root + already: */ + if (dest > rname + prefix_len + 1) + for (--dest; dest > rname && !ISSLASH (dest[-1]); --dest) + continue; + if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rname + 1 + && ISSLASH (*dest) && !ISSLASH (dest[1]) && !prefix_len) + dest++; + } + + free (buf); + } + else + { + if (!S_ISDIR (st.st_mode) && *end && (can_mode != CAN_MISSING)) + { + saved_errno = ENOTDIR; + goto error; + } + } + } + } + if (dest > rname + prefix_len + 1 && ISSLASH (dest[-1])) + --dest; + if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rname + 1 && !prefix_len + && ISSLASH (*dest) && !ISSLASH (dest[1])) + dest++; + *dest = '\0'; + if (rname_limit != dest + 1) + rname = xrealloc (rname, dest - rname + 1); + + free (extra_buf); + if (ht) + hash_free (ht); + return rname; + +error: + free (extra_buf); + free (rname); + if (ht) + hash_free (ht); + errno = saved_errno; + return NULL; +} |