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https://gitlab.freedesktop.org/NetworkManager/NetworkManager.git
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core: add nm_utils_file_get_contents() and nm_utils_fd_get_contents()
A reimplementation of g_file_get_contents() to overcome two limitations: - nm_utils_file_get_contents() accepts a @dirfd argument to open the file relative using openat(). - nm_utils_fd_get_contents() allows to read the content from a file filedescriptor. - both support a max_length argument, to fail gracefully if we get tricked into loading a huge file.
This commit is contained in:
Thomas Haller
parent
76876e896c
commit
1d9bdad1df
2 changed files with 259 additions and 6 deletions
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@ -2802,6 +2802,246 @@ nm_utils_fd_read_loop_exact (int fd, void *buf, size_t nbytes, bool do_poll)
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return 0;
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}
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_nm_printf (3, 4)
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static int
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_get_contents_error (GError **error, int errsv, const char *format, ...)
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{
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if (errsv < 0)
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errsv = -errsv;
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else if (!errsv)
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errsv = errno;
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if (error) {
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char *msg;
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va_list args;
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va_start (args, format);
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msg = g_strdup_vprintf (format, args);
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va_end (args);
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g_set_error (error,
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G_FILE_ERROR,
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g_file_error_from_errno (errsv),
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"%s: %s",
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msg, g_strerror (errsv));
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g_free (msg);
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}
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return -errsv;
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}
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/**
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* nm_utils_fd_get_contents:
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* @fd: open file descriptor to read. The fd will not be closed,
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* but don't rely on it's state afterwards.
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* @max_length: allocate at most @max_length bytes. If the
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* file is larger, reading will fail. Set to zero to use
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* a very large default.
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*
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* WARNING: @max_length is here to avoid a crash for huge/unlimited files.
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* For example, stat(/sys/class/net/enp0s25/ifindex) gives a filesize of
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* 4K, although the actual real is small. @max_length is the memory
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* allocated in the process of reading the file, thus it must be at least
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* the size reported by fstat.
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* If you set it to 1K, read will fail because fstat() claims the
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* file is larger.
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*
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* @contents: the output buffer with the file read. It is always
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* NUL terminated. The buffer is at most @max_length long, including
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* the NUL byte. That is, it reads only files up to a length of
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* @max_length - 1 bytes.
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* @length: optional output argument of the read file size.
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*
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* A reimplementation of g_file_get_contents() with a few differences:
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* - accepts an open fd, instead of a path name. This allows you to
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* use openat().
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* - limits the maxium filesize to max_length.
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*
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* Returns: a negative error code on failure.
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*/
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int
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nm_utils_fd_get_contents (int fd,
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gsize max_length,
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char **contents,
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gsize *length,
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GError **error)
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{
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struct stat stat_buf;
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gs_free char *str = NULL;
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g_return_val_if_fail (fd >= 0, -EINVAL);
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g_return_val_if_fail (contents, -EINVAL);
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g_return_val_if_fail (!error || !*error, -EINVAL);
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if (fstat (fd, &stat_buf) < 0)
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return _get_contents_error (error, 0, "failure during fstat");
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if (!max_length) {
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/* default to a very large size, but not extreme */
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max_length = 2 * 1024 * 1024;
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}
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if ( stat_buf.st_size > 0
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&& S_ISREG (stat_buf.st_mode)) {
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const gsize n_stat = stat_buf.st_size;
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ssize_t n_read;
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if (n_stat > max_length - 1)
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return _get_contents_error (error, EMSGSIZE, "file too large (%zu+1 bytes with maximum %zu bytes)", n_stat, max_length);
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str = g_try_malloc (n_stat + 1);
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if (!str)
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return _get_contents_error (error, ENOMEM, "failure to allocate buffer of %zu+1 bytes", n_stat);
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n_read = nm_utils_fd_read_loop (fd, str, n_stat, TRUE);
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if (n_read < 0)
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return _get_contents_error (error, n_read, "error reading %zu bytes from file descriptor", n_stat);
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str[n_read] = '\0';
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if (n_read < n_stat) {
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char *tmp;
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tmp = g_try_realloc (str, n_read + 1);
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if (!tmp)
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return _get_contents_error (error, ENOMEM, "failure to reallocate buffer with %zu bytes", n_read + 1);
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str = tmp;
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}
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NM_SET_OUT (length, n_read);
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} else {
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nm_auto_fclose FILE *f = NULL;
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char buf[4096];
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gsize n_have, n_alloc;
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if (!(f = fdopen (fd, "r")))
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return _get_contents_error (error, 0, "failure during fdopen");
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n_have = 0;
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n_alloc = 0;
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while (!feof (f)) {
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int errsv;
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gsize n_read;
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n_read = fread (buf, 1, sizeof (buf), f);
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errsv = errno;
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if (ferror (f))
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return _get_contents_error (error, errsv, "error during fread");
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if ( n_have > G_MAXSIZE - 1 - n_read
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|| n_have + n_read + 1 > max_length) {
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return _get_contents_error (error, EMSGSIZE, "file stream too large (%zu+1 bytes with maximum %zu bytes)",
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(n_have > G_MAXSIZE - 1 - n_read) ? G_MAXSIZE : n_have + n_read,
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max_length);
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}
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if (n_have + n_read + 1 >= n_alloc) {
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char *tmp;
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if (str) {
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if (n_alloc >= max_length / 2)
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n_alloc = max_length;
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else
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n_alloc *= 2;
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} else
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n_alloc = NM_MIN (n_read + 1, sizeof (buf));
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tmp = g_try_realloc (str, n_alloc);
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if (!tmp)
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return _get_contents_error (error, ENOMEM, "failure to allocate buffer of %zu bytes", n_alloc);
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str = tmp;
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}
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memcpy (str + n_have, buf, n_read);
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n_have += n_read;
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}
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if (n_alloc == 0)
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str = g_new0 (gchar, 1);
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else {
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str[n_have] = '\0';
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if (n_have + 1 < n_alloc) {
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char *tmp;
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tmp = g_try_realloc (str, n_have + 1);
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if (!tmp)
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return _get_contents_error (error, ENOMEM, "failure to truncate buffer to %zu bytes", n_have + 1);
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str = tmp;
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}
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}
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NM_SET_OUT (length, n_have);
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}
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*contents = g_steal_pointer (&str);
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return 0;
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}
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/**
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* nm_utils_file_get_contents:
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* @dirfd: optional file descriptor to use openat(). If negative, use plain open().
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* @filename: the filename to open. Possibly relative to @dirfd.
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* @max_length: allocate at most @max_length bytes.
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* WARNING: see nm_utils_fd_get_contents() hint about @max_length.
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* @contents: the output buffer with the file read. It is always
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* NUL terminated. The buffer is at most @max_length long, including
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* the NUL byte. That is, it reads only files up to a length of
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* @max_length - 1 bytes.
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* @length: optional output argument of the read file size.
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*
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* A reimplementation of g_file_get_contents() with a few differences:
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* - accepts an @dirfd to open @filename relative to that path via openat().
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* - limits the maxium filesize to max_length.
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* - uses O_CLOEXEC on internal file descriptor
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*
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* Returns: a negative error code on failure.
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*/
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int
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nm_utils_file_get_contents (int dirfd,
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const char *filename,
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gsize max_length,
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char **contents,
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gsize *length,
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GError **error)
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{
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nm_auto_close int fd = -1;
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int errsv;
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g_return_val_if_fail (filename && filename[0], -EINVAL);
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if (dirfd >= 0) {
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fd = openat (dirfd, filename, O_RDONLY | O_CLOEXEC);
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if (fd < 0) {
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errsv = errno;
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g_set_error (error,
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G_FILE_ERROR,
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g_file_error_from_errno (errsv),
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"Failed to open file \"%s\" with openat: %s",
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filename,
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g_strerror (errsv));
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return -errsv;
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}
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} else {
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fd = open (filename, O_RDONLY | O_CLOEXEC);
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if (fd < 0) {
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errsv = errno;
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g_set_error (error,
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G_FILE_ERROR,
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g_file_error_from_errno (errsv),
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"Failed to open file \"%s\": %s",
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filename,
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g_strerror (errsv));
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return -errsv;
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}
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}
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return nm_utils_fd_get_contents (fd,
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max_length,
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contents,
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length,
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error);
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}
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/*****************************************************************************/
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/* taken from systemd's dev_urandom(). */
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int
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nm_utils_read_urandom (void *p, size_t nbytes)
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@ -313,6 +313,25 @@ int nm_utils_fd_wait_for_event (int fd, int event, gint64 timeout_ns);
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ssize_t nm_utils_fd_read_loop (int fd, void *buf, size_t nbytes, bool do_poll);
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int nm_utils_fd_read_loop_exact (int fd, void *buf, size_t nbytes, bool do_poll);
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int nm_utils_fd_get_contents (int fd,
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gsize max_length,
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char **contents,
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gsize *length,
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GError **error);
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int nm_utils_file_get_contents (int dirfd,
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const char *filename,
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gsize max_length,
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char **contents,
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gsize *length,
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GError **error);
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gboolean nm_utils_file_set_contents (const gchar *filename,
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const gchar *contents,
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gssize length,
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mode_t mode,
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GError **error);
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int nm_utils_read_urandom (void *p, size_t n);
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char *nm_utils_machine_id_read (void);
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@ -445,12 +464,6 @@ const char *nm_utils_dnsmasq_status_to_string (int status, char *dest, gsize siz
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void nm_utils_get_reverse_dns_domains_ip4 (guint32 ip, guint8 plen, GPtrArray *domains);
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void nm_utils_get_reverse_dns_domains_ip6 (const struct in6_addr *ip, guint8 plen, GPtrArray *domains);
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gboolean nm_utils_file_set_contents (const gchar *filename,
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const gchar *contents,
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gssize length,
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mode_t mode,
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GError **error);
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struct stat;
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gboolean nm_utils_validate_plugin (const char *path, struct stat *stat, GError **error);
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