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

1 files changed, 18 insertions, 7 deletions

diff --git a/res/stasis_recording/stored.c b/res/stasis_recording/stored.c
index 9df5d75dc..ac216ff8c 100644
--- a/res/stasis_recording/stored.c
+++ b/res/stasis_recording/stored.c
@@ -330,6 +330,7 @@ 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;
 
@@ -350,18 +351,28 @@ 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) {