res_stasis_recording: Allow symbolic links in configured recordings dir.

If any component of ast_config_AST_RECORDING_DIR is a symbolic link we
would incorrectly assume the ARI user was trying to escape the recording
path.  Create additional check to check the recording directory's
realpath, only deny access if both do not match.

This is needed by the testsuite when run by 'run-local'.

Change-Id: I9145e841865edadcb5f75cead3471ad06bbb56c0

diff --git a/res/stasis_recording/stored.c b/res/stasis_recording/stored.c
index 3ad7d82a9772cdca82072cb3d49ad797aa586f9d..f916e68026f66faf6d7f3ba6b298112aef72874c 100644 (file)
--- a/res/stasis_recording/stored.c
+++ b/res/stasis_recording/stored.c
@@ -314,6 +314,7 @@ struct stasis_app_stored_recording *stasis_app_stored_recording_find_by_name(
        RAII_VAR(char *, file_with_ext, NULL, ast_free);
        int res;
        struct stat file_stat;
+       int prefix_len = strlen(ast_config_AST_RECORDING_DIR);
 
        errno = 0;
 
@@ -334,18 +335,28 @@ struct stasis_app_stored_recording *stasis_app_stored_recording_find_by_name(
        ast_string_field_build(recording, file, "%s/%s", dir, file);
 
        if (!ast_begins_with(dir, ast_config_AST_RECORDING_DIR)) {
-               /* Attempt to escape the recording directory */
-               ast_log(LOG_WARNING, "Attempt to access invalid recording %s\n",
-                       name);
-               errno = EACCES;
-               return NULL;
+               /* It's possible that one or more component of the recording path is
+                * a symbolic link, this would prevent dir from ever matching. */
+               char *real_basedir = realpath(ast_config_AST_RECORDING_DIR, NULL);
+
+               if (!real_basedir || !ast_begins_with(dir, real_basedir)) {
+                       /* Attempt to escape the recording directory */
+                       ast_log(LOG_WARNING, "Attempt to access invalid recording directory %s\n",
+                               dir);
+                       ast_std_free(real_basedir);
+                       errno = EACCES;
+
+                       return NULL;
+               }
+
+               prefix_len = strlen(real_basedir);
+               ast_std_free(real_basedir);
        }
 
        /* The actual name of the recording is file with the config dir
         * prefix removed.
         */
-       ast_string_field_set(recording, name,
-               recording->file + strlen(ast_config_AST_RECORDING_DIR) + 1);
+       ast_string_field_set(recording, name, recording->file + prefix_len + 1);
 
        file_with_ext = find_recording(dir, file);
        if (!file_with_ext) {