diff options
Diffstat (limited to 'lib/canonicalize.c')
| -rw-r--r-- | lib/canonicalize.c | 469 |
1 files changed, 469 insertions, 0 deletions
diff --git a/lib/canonicalize.c b/lib/canonicalize.c new file mode 100644 index 0000000..d73ee2c --- /dev/null +++ b/lib/canonicalize.c @@ -0,0 +1,469 @@ +/* Return the canonical absolute name of a given file. + Copyright (C) 1996-2023 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 <fcntl.h> +#include <string.h> +#include <sys/stat.h> +#include <unistd.h> + +#include <filename.h> +#include <idx.h> +#include <intprops.h> +#include <scratch_buffer.h> + +#include "attribute.h" +#include "file-set.h" +#include "hash-triple.h" +#include "xalloc.h" + +#ifndef DOUBLE_SLASH_IS_DISTINCT_ROOT +# define DOUBLE_SLASH_IS_DISTINCT_ROOT false +#endif + +#if ISSLASH ('\\') +# define SLASHES "/\\" +#else +# define SLASHES "/" +#endif + +/* Avoid false GCC warning "'end_idx' may be used uninitialized". */ +#if __GNUC__ + (__GNUC_MINOR__ >= 7) > 4 +# pragma GCC diagnostic ignored "-Wmaybe-uninitialized" +#endif + +/* Return true if FILE's existence can be shown, false (setting errno) + otherwise. Follow symbolic links. */ +static bool +file_accessible (char const *file) +{ +# if HAVE_FACCESSAT + return faccessat (AT_FDCWD, file, F_OK, AT_EACCESS) == 0; +# else + struct stat st; + return stat (file, &st) == 0 || errno == EOVERFLOW; +# endif +} + +/* True if concatenating END as a suffix to a file name means that the + code needs to check that the file name is that of a searchable + directory, since the canonicalize_filename_mode_stk code won't + check this later anyway when it checks an ordinary file name + component within END. END must either be empty, or start with a + slash. */ + +static bool _GL_ATTRIBUTE_PURE +suffix_requires_dir_check (char const *end) +{ + /* If END does not start with a slash, the suffix is OK. */ + while (ISSLASH (*end)) + { + /* Two or more slashes act like a single slash. */ + do + end++; + while (ISSLASH (*end)); + + switch (*end++) + { + default: return false; /* An ordinary file name component is OK. */ + case '\0': return true; /* Trailing "/" is trouble. */ + case '.': break; /* Possibly "." or "..". */ + } + /* Trailing "/.", or "/.." even if not trailing, is trouble. */ + if (!*end || (*end == '.' && (!end[1] || ISSLASH (end[1])))) + return true; + } + + return false; +} + +/* Append this to a file name to test whether it is a searchable directory. + On POSIX platforms "/" suffices, but "/./" is sometimes needed on + macOS 10.13 <https://bugs.gnu.org/30350>, and should also work on + platforms like AIX 7.2 that need at least "/.". */ + +#ifdef LSTAT_FOLLOWS_SLASHED_SYMLINK +static char const dir_suffix[] = "/"; +#else +static char const dir_suffix[] = "/./"; +#endif + +/* Return true if DIR is a searchable dir, false (setting errno) otherwise. + DIREND points to the NUL byte at the end of the DIR string. + Store garbage into DIREND[0 .. strlen (dir_suffix)]. */ + +static bool +dir_check (char *dir, char *dirend) +{ + strcpy (dirend, dir_suffix); + return file_accessible (dir); +} + +#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 */ + +static bool +multiple_bits_set (canonicalize_mode_t i) +{ + return (i & (i - 1)) != 0; +} + +/* 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) + { + idx_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; +} + +/* Scratch buffers used by canonicalize_filename_mode_stk and managed + by __realpath. */ +struct realpath_bufs +{ + struct scratch_buffer rname; + struct scratch_buffer extra; + struct scratch_buffer link; +}; + +static char * +canonicalize_filename_mode_stk (const char *name, canonicalize_mode_t can_mode, + struct realpath_bufs *bufs) +{ + char *dest; + char const *start; + char const *end; + Hash_table *ht = NULL; + bool logical = (can_mode & CAN_NOLINKS) != 0; + int num_links = 0; + + canonicalize_mode_t can_exist = can_mode & CAN_MODE_MASK; + if (multiple_bits_set (can_exist)) + { + errno = EINVAL; + return NULL; + } + + if (name == NULL) + { + errno = EINVAL; + return NULL; + } + + if (name[0] == '\0') + { + errno = ENOENT; + return NULL; + } + + char *rname = bufs->rname.data; + bool end_in_extra_buffer = false; + bool failed = true; + + /* This is always zero for Posix hosts, but can be 2 for MS-Windows + and MS-DOS X:/foo/bar file names. */ + idx_t prefix_len = FILE_SYSTEM_PREFIX_LEN (name); + + if (!IS_ABSOLUTE_FILE_NAME (name)) + { + while (!getcwd (bufs->rname.data, bufs->rname.length)) + { + switch (errno) + { + case ERANGE: + if (scratch_buffer_grow (&bufs->rname)) + break; + FALLTHROUGH; + case ENOMEM: + xalloc_die (); + + default: + dest = rname; + goto error; + } + rname = bufs->rname.data; + } + dest = rawmemchr (rname, '\0'); + start = name; + prefix_len = FILE_SYSTEM_PREFIX_LEN (rname); + } + else + { + dest = mempcpy (rname, name, prefix_len); + *dest++ = '/'; + if (DOUBLE_SLASH_IS_DISTINCT_ROOT) + { + if (prefix_len == 0 /* implies ISSLASH (name[0]) */ + && ISSLASH (name[1]) && !ISSLASH (name[2])) + { + *dest++ = '/'; +#if defined _WIN32 && !defined __CYGWIN__ + /* For UNC file names '\\server\path\to\file', extend the prefix + to include the server: '\\server\'. */ + { + idx_t i; + for (i = 2; name[i] != '\0' && !ISSLASH (name[i]); ) + i++; + if (name[i] != '\0' /* implies ISSLASH (name[i]) */ + && i + 1 < bufs->rname.length) + { + prefix_len = i; + memcpy (dest, name + 2, i - 2 + 1); + dest += i - 2 + 1; + } + else + { + /* Either name = '\\server'; this is an invalid file name. + Or name = '\\server\...' and server is more than + bufs->rname.length - 4 bytes long. In either + case, stop the UNC processing. */ + } + } +#endif + } + *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. */; + + /* Length of this file name component; it can be zero if a file + name ends in '/'. */ + idx_t startlen = end - start; + + if (startlen == 0) + break; + else if (startlen == 1 && start[0] == '.') + /* nothing */; + else if (startlen == 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 + { + if (!ISSLASH (dest[-1])) + *dest++ = '/'; + + while (rname + bufs->rname.length - dest + < startlen + sizeof dir_suffix) + { + idx_t dest_offset = dest - rname; + if (!scratch_buffer_grow_preserve (&bufs->rname)) + xalloc_die (); + rname = bufs->rname.data; + dest = rname + dest_offset; + } + + dest = mempcpy (dest, start, startlen); + *dest = '\0'; + + char *buf; + ssize_t n = -1; + if (!logical) + { + while (true) + { + buf = bufs->link.data; + idx_t bufsize = bufs->link.length; + n = readlink (rname, buf, bufsize - 1); + if (n < bufsize - 1) + break; + if (!scratch_buffer_grow (&bufs->link)) + xalloc_die (); + } + } + if (0 <= n) + { + /* A physical traversal and RNAME is a symbolic link. */ + + if (num_links < 20) + num_links++; + else if (*start) + { + /* Enough symlinks have been seen that it is time to + worry about being in a symlink cycle. + Get the device and inode of the parent directory, as + pre-2017 POSIX says this info is not reliable for + symlinks. */ + struct stat st; + dest[- startlen] = '\0'; + if (stat (*rname ? rname : ".", &st) != 0) + goto error; + dest[- startlen] = *start; + + /* Detect loops. We cannot use the cycle-check module here, + since it's possible to encounter the same parent + directory more than once in a given traversal. However, + encountering the same (parentdir, START) pair twice does + indicate a loop. */ + if (seen_triple (&ht, start, &st)) + { + if (can_exist == CAN_MISSING) + continue; + errno = ELOOP; + goto error; + } + } + + buf[n] = '\0'; + + char *extra_buf = bufs->extra.data; + idx_t end_idx; + if (end_in_extra_buffer) + end_idx = end - extra_buf; + size_t len = strlen (end); + if (INT_ADD_OVERFLOW (len, n)) + xalloc_die (); + while (bufs->extra.length <= len + n) + { + if (!scratch_buffer_grow_preserve (&bufs->extra)) + xalloc_die (); + extra_buf = bufs->extra.data; + } + if (end_in_extra_buffer) + end = extra_buf + end_idx; + + /* Careful here, end may be a pointer into extra_buf... */ + memmove (&extra_buf[n], end, len + 1); + name = end = memcpy (extra_buf, buf, n); + end_in_extra_buffer = true; + + if (IS_ABSOLUTE_FILE_NAME (buf)) + { + idx_t pfxlen = FILE_SYSTEM_PREFIX_LEN (buf); + + dest = mempcpy (rname, buf, 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++; + } + } + else if (! (can_exist == CAN_MISSING + || (suffix_requires_dir_check (end) + ? dir_check (rname, dest) + : !logical + ? errno == EINVAL + : *end || file_accessible (rname)) + || (can_exist == CAN_ALL_BUT_LAST + && errno == ENOENT + && !end[strspn (end, SLASHES)]))) + 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++; + failed = false; + +error: + if (ht) + hash_free (ht); + + if (failed) + return NULL; + + *dest++ = '\0'; + char *result = malloc (dest - rname); + if (!result) + xalloc_die (); + return memcpy (result, rname, dest - rname); +} + +/* 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) +{ + struct realpath_bufs bufs; + scratch_buffer_init (&bufs.rname); + scratch_buffer_init (&bufs.extra); + scratch_buffer_init (&bufs.link); + char *result = canonicalize_filename_mode_stk (name, can_mode, &bufs); + scratch_buffer_free (&bufs.link); + scratch_buffer_free (&bufs.extra); + scratch_buffer_free (&bufs.rname); + return result; +} |