Change the utils_expand_path function to use utils_partial_realpath

As most of the resolve-related work can now be done using
utils_partial_realpath, the utils_expand_path function can
call it and concentrate on resolving the relative paths in
the middle of a path string, such as '/./' and '/../'.

Signed-off-by: Raphaël Beamonte <raphael.beamonte@gmail.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>

diff --git a/src/common/utils.c b/src/common/utils.c
index 57add319ba416b6eda1cb967fc126c008177f45f..d28e31349df3cd3bf383e8d366c119db52305c57 100644 (file)
--- a/src/common/utils.c
+++ b/src/common/utils.c
@@ -230,102 +230,87 @@ error:
        return NULL;
 }
 
-
 /*
- * Return the realpath(3) of the path even if the last directory token does not
- * exist. For example, with /tmp/test1/test2, if test2/ does not exist but the
- * /tmp/test1 does, the real path is returned. In normal time, realpath(3)
- * fails if the end point directory does not exist.
+ * Make a full resolution of the given path even if it doesn't exist.
+ * This function uses the utils_partial_realpath function to resolve
+ * symlinks and relatives paths at the start of the string, and
+ * implements functionnalities to resolve the './' and '../' strings
+ * in the middle of a path. This function is only necessary because
+ * realpath(3) does not accept to resolve unexistent paths.
+ * The returned string was allocated in the function, it is thus of
+ * the responsibility of the caller to free this memory.
  */
 LTTNG_HIDDEN
 char *utils_expand_path(const char *path)
 {
-       const char *end_path = NULL;
-       char *next, *cut_path = NULL, *expanded_path = NULL;
+       char *next, *previous, *slash, *start_path, *absolute_path = NULL;
 
        /* Safety net */
        if (path == NULL) {
                goto error;
        }
 
-       /* Allocate memory for the expanded path */
-       expanded_path = zmalloc(PATH_MAX);
-       if (expanded_path == NULL) {
+       /* Allocate memory for the absolute_path */
+       absolute_path = zmalloc(PATH_MAX);
+       if (absolute_path == NULL) {
                PERROR("zmalloc expand path");
                goto error;
        }
 
-       /* If given path is already absolute */
-       if (*path == '/') {
-               strncpy(expanded_path, path, PATH_MAX);
-       /* Else, we have some work to do */
+       /*
+        * If the path is not already absolute nor explicitly relative,
+        * consider we're in the current directory
+        */
+       if (*path != '/' && strncmp(path, "./", 2) != 0 &&
+                       strncmp(path, "../", 3) != 0) {
+               snprintf(absolute_path, PATH_MAX, "./%s", path);
+               /* Else, we just copy the path */
        } else {
-               /* Pointer to the last char of the path */
-               const char *last_char = path + strlen(path) - 1;
+               strncpy(absolute_path, path, PATH_MAX);
+       }
 
-               end_path = path;
+       /* Resolve partially our path */
+       absolute_path = utils_partial_realpath(absolute_path,
+                       absolute_path, PATH_MAX);
 
-               /* Split part that will be resolved by realpath (relative path from
-                * current directory using ./ or ../ only) and part that could not
-                * (directory names)
-                */
-               while ((next = strpbrk(end_path, "/")) && (next != last_char)) {
-                       end_path = next + 1;
-                       if (strncmp(end_path, "./", 2) != 0 &&
-                                       strncmp(end_path, "../", 3) != 0) {
-                               break;
-                       }
-               }
+       /* As long as we find '/./' in the working_path string */
+       while ((next = strstr(absolute_path, "/./"))) {
 
-               /* If this is the end of the string, and we still can resolve it */
-               if (strncmp(end_path, "..\0", 3) == 0 ||
-                               strncmp(end_path, ".\0", 2) == 0) {
-                       end_path += strlen(end_path);
-               }
+               /* We prepare the start_path not containing it */
+               start_path = strndup(absolute_path, next - absolute_path);
 
-               /* If the end part is the whole path, we are in the current dir */
-               if (end_path == path) {
-                       cut_path = strdup(".");
-               /* Else, cut the resolvable part from original path */
-               } else {
-                       cut_path = strndup(path, end_path - path);
-               }
+               /* And we concatenate it with the part after this string */
+               snprintf(absolute_path, PATH_MAX, "%s%s", start_path, next + 2);
 
-               /* Resolve the canonical path of the first part of the path */
-               expanded_path = realpath((char *)cut_path, expanded_path);
-               if (expanded_path == NULL) {
-                       switch (errno) {
-                       case ENOENT:
-                               ERR("%s: No such file or directory", cut_path);
-                               break;
-                       default:
-                               PERROR("realpath utils expand path");
-                               break;
-                       }
-                       goto error;
-               }
+               free(start_path);
+       }
 
-               /* Add end part to expanded path if not empty */
-               if (*end_path != 0) {
-                       strncat(expanded_path, "/", PATH_MAX - strlen(expanded_path) - 1);
-                       strncat(expanded_path, end_path,
-                                       PATH_MAX - strlen(expanded_path) - 1);
+       /* As long as we find '/../' in the working_path string */
+       while ((next = strstr(absolute_path, "/../"))) {
+               /* We find the last level of directory */
+               previous = absolute_path;
+               while ((slash = strpbrk(previous, "/")) && slash != next) {
+                       previous = slash + 1;
                }
-       }
 
-       /* Resolve the internal './' and '../' strings */
-       next = utils_resolve_relative(expanded_path);
-       if (next == NULL) {
-               goto error;
+               /* Then we prepare the start_path not containing it */
+               start_path = strndup(absolute_path, previous - absolute_path);
+
+               /* And we concatenate it with the part after the '/../' */
+               snprintf(absolute_path, PATH_MAX, "%s%s", start_path, next + 4);
+
+               /* We can free the memory used for the start path*/
+               free(start_path);
+
+               /* Then we verify for symlinks using partial_realpath */
+               absolute_path = utils_partial_realpath(absolute_path,
+                               absolute_path, PATH_MAX);
        }
 
-       free(expanded_path);
-       free(cut_path);
-       return next;
+       return absolute_path;
 
 error:
-       free(expanded_path);
-       free(cut_path);
+       free(absolute_path);
        return NULL;
 }