From ef1fcbd1830778e9ba8065fc764105f0b67bff27 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Helleu?= <flashcode@flashtux.org>
Date: Sun, 12 May 2019 22:18:42 +0200
Subject: [PATCH] relay: do not overwrite a file if it's not a socket, display
 an error when the socket can not be created

---
 src/plugins/relay/relay-config.c | 38 +++++++++++++++++++++++++
 src/plugins/relay/relay-config.h |  1 +
 src/plugins/relay/relay-server.c | 49 +++++++++++++++++++++++++++-----
 3 files changed, 81 insertions(+), 7 deletions(-)

diff --git a/src/plugins/relay/relay-config.c b/src/plugins/relay/relay-config.c
index 904537216..4c0771387 100644
--- a/src/plugins/relay/relay-config.c
+++ b/src/plugins/relay/relay-config.c
@@ -19,11 +19,15 @@
  * along with WeeChat.  If not, see <https://www.gnu.org/licenses/>.
  */
 
+#include <unistd.h>
 #include <stdlib.h>
 #include <string.h>
 #include <limits.h>
 #include <regex.h>
 #include <sys/un.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <errno.h>
 
 #include "../weechat-plugin.h"
 #include "relay.h"
@@ -545,6 +549,40 @@ relay_config_check_path_length (const char *path)
     return 1;
 }
 
+/*
+ * Checks if a UNIX path is available: it is available if not existing, or
+ * if a file of type socket already exists.
+ *
+ * Returns:
+ *    0: path is available
+ *   -1: path already exists and is not a socket
+ *   -2: invalid path
+ */
+
+int
+relay_config_check_path_available (const char *path)
+{
+    struct stat buf;
+    int rc;
+
+    rc = stat (path, &buf);
+
+    /* OK if an existing file is a socket */
+    if ((rc == 0) && S_ISSOCK(buf.st_mode))
+        return 0;
+
+    /* error if an existing file is NOT a socket */
+    if (rc == 0)
+        return -1;
+
+    /* OK if the file does not exist */
+    if (errno == ENOENT)
+        return 0;
+
+    /* on any other error, the path it considered as not available */
+    return -2;
+}
+
 /*
  * Checks if a path is valid.
  *
diff --git a/src/plugins/relay/relay-config.h b/src/plugins/relay/relay-config.h
index 2b5e53000..f28f39a5a 100644
--- a/src/plugins/relay/relay-config.h
+++ b/src/plugins/relay/relay-config.h
@@ -74,6 +74,7 @@ extern int relay_config_create_option_port_path (const void *pointer, void *data
                                                  const char *option_name,
                                                  const char *value);
 extern int relay_config_check_path_length (const char *path);
+extern int relay_config_check_path_available (const char *path);
 extern int relay_config_init ();
 extern int relay_config_read ();
 extern int relay_config_write ();
diff --git a/src/plugins/relay/relay-server.c b/src/plugins/relay/relay-server.c
index 03e3d0e82..9c2aa1caa 100644
--- a/src/plugins/relay/relay-server.c
+++ b/src/plugins/relay/relay-server.c
@@ -472,7 +472,7 @@ end:
 int
 relay_server_create_socket (struct t_relay_server *server)
 {
-    int domain, set, max_clients, addr_size;
+    int domain, set, max_clients, addr_size, rc;
     struct sockaddr_in server_addr;
     struct sockaddr_in6 server_addr6;
     struct sockaddr_un server_addr_unix;
@@ -535,8 +535,32 @@ relay_server_create_socket (struct t_relay_server *server)
         ptr_addr = &server_addr_unix;
         addr_size = sizeof (struct sockaddr_un);
         if (!relay_config_check_path_length (server->path))
+        {
+            weechat_printf (NULL,
+                            _("%s%s: invalid socket path \"%s\""),
+                            weechat_prefix ("error"), RELAY_PLUGIN_NAME,
+                            server->path);
             return 0;
-        /* just in case it already exists */
+        }
+        rc = relay_config_check_path_available (server->path);
+        switch (rc)
+        {
+            case -1:
+                weechat_printf (NULL,
+                                _("%s%s: socket path \"%s\" exists and is not "
+                                  "a socket"),
+                                weechat_prefix ("error"), RELAY_PLUGIN_NAME,
+                                server->path);
+                break;
+            case -2:
+                weechat_printf (NULL,
+                                _("%s%s: socket path \"%s\" is invalid"),
+                                weechat_prefix ("error"), RELAY_PLUGIN_NAME,
+                                server->path);
+        }
+        if (rc < 0)
+            return 0;
+        /* just in case a socket already exists */
         unlink (server->path);
     }
 
@@ -749,11 +773,22 @@ relay_server_new (const char *protocol_string, enum t_relay_protocol protocol,
 void
 relay_server_update_path (struct t_relay_server *server, const char *path)
 {
-    relay_server_close_socket (server);
-    free (server->path);
-    server->path = weechat_string_eval_path_home (path, NULL, NULL, NULL);
-    server->port = -1;
-    relay_server_create_socket (server);
+    char *new_path;
+
+    new_path = weechat_string_eval_path_home (path, NULL, NULL, NULL);
+    if (!new_path)
+        return;
+
+    if (strcmp (new_path, server->path) != 0)
+    {
+        relay_server_close_socket (server);
+        free (server->path);
+        server->path = strdup (new_path);
+        server->port = -1;
+        relay_server_create_socket (server);
+    }
+
+    free (new_path);
 }
 
 /*