res_crypto: Don't load non-regular files in keys directory

ASTERISK-30046

Change-Id: Ie77e0648f8b0b1c2159fb24662d1989cfd4cc36d

doc/UPGRADE-staging/res_crypto-regular-file-keys.txt

@@ -0,0 +1,5 @@
+Subject: res_crypto
+
+In addition to only paying attention to files ending with .key or .pub
+in the keys directory, we now also ignore any files which aren't regular
+files.

res/res_crypto.c

@@ -507,6 +507,13 @@ static void crypto_load(int ifd, int ofd)
 	/* Load new keys */
 	if ((dir = opendir(ast_config_AST_KEY_DIR))) {
 		while ((ent = readdir(dir))) {
+			if (!strcmp(ent->d_name, ".") || !strcmp(ent->d_name, "..")) {
+				continue;
+			}
+			if (ent->d_type != DT_REG) {
+				ast_log(LOG_WARNING, "Non-regular file '%s' in keys directory\n", ent->d_name);
+				continue;
+			}
 			try_load_key(ast_config_AST_KEY_DIR, ent->d_name, ifd, ofd, &note);
 		}
 		closedir(dir);