QUIC: fixed handling of RETIRE_CONNECTION_ID frame.

Previously, the retired socket was not closed if it didn't match
active or backup.

New sockets could not be created (due to count limit), since retired socket
was not closed before calling ngx_quic_create_sockets().

When replacing retired socket, new socket is only requested after closing
old one, to avoid hitting the limit on the number of active connection ids.

Together with added restrictions, this fixes an issue when a current socket
could be closed during migration, recreated and erroneously reused leading
to null pointer dereference.

diff --git a/src/event/quic/ngx_event_quic_connid.c b/src/event/quic/ngx_event_quic_connid.c
index 8b9805b1e0118b08fb9a888988aed7be60d4923d..503a71b4eb9d935fb48bd1e24488b20ffdbb07f8 100644 (file)
--- a/src/event/quic/ngx_event_quic_connid.c
+++ b/src/event/quic/ngx_event_quic_connid.c
@@ -403,6 +403,10 @@ ngx_quic_handle_retire_connection_id_frame(ngx_connection_t *c,
         return NGX_OK;
     }
 
+    ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                   "quic socket #%uL is retired", qsock->sid.seqnum);
+
+    /* check if client is willing to retire sid we have in use */
     if (qsock->sid.seqnum == qc->socket->sid.seqnum) {
         tmp = &qc->socket;
 
@@ -410,46 +414,68 @@ ngx_quic_handle_retire_connection_id_frame(ngx_connection_t *c,
         tmp = &qc->backup;
 
     } else {
-        tmp = NULL;
-    }
-
-    if (ngx_quic_create_sockets(c) != NGX_OK) {
-        return NGX_ERROR;
-    }
 
-    if (tmp) {
-        /* replace socket in use (active or backup) */
+        ngx_quic_close_socket(c, qsock);
 
-        ngx_log_debug4(NGX_LOG_DEBUG_EVENT, c->log, 0,
-                       "quic %s socket #%uL:%uL:%uL retired",
-                       (*tmp) == qc->socket ? "active" : "backup",
-                       (*tmp)->sid.seqnum, (*tmp)->cid->seqnum,
-                       (*tmp)->path->seqnum);
-
-        qsock = ngx_quic_get_unconnected_socket(c);
-        if (qsock == NULL) {
+        /* restore socket count up to a limit after deletion */
+        if (ngx_quic_create_sockets(c) != NGX_OK) {
             return NGX_ERROR;
         }
 
-        path = (*tmp)->path;
-        cid = (*tmp)->cid;
+        return NGX_OK;
+    }
 
-        ngx_quic_connect(c, qsock, path, cid);
+    /* preserve path/cid from retired socket */
+    path = qsock->path;
+    cid = qsock->cid;
 
+    /* ensure that closing_socket will not drop path and cid */
+    path->refcnt++;
+    cid->refcnt++;
 
-        ngx_log_debug5(NGX_LOG_DEBUG_EVENT, c->log, 0,
-                       "quic %s socket is now #%uL:%uL:%uL (%s)",
-                       (*tmp) == qc->socket ? "active" : "backup",
-                       qsock->sid.seqnum, qsock->cid->seqnum,
-                       qsock->path->seqnum,
-                       ngx_quic_path_state_str(qsock->path));
+    ngx_quic_close_socket(c, qsock);
 
-        ngx_quic_close_socket(c, *tmp); /* no longer used */
+    /* restore original values */
+    path->refcnt--;
+    cid->refcnt--;
 
-        *tmp = qsock;
+    /* restore socket count up to a limit after deletion */
+    if (ngx_quic_create_sockets(c) != NGX_OK) {
+        goto failed;
     }
 
+    qsock = ngx_quic_get_unconnected_socket(c);
+    if (qsock == NULL) {
+        qc->error = NGX_QUIC_ERR_CONNECTION_ID_LIMIT_ERROR;
+        qc->error_reason = "not enough server IDs";
+        goto failed;
+    }
+
+    ngx_quic_connect(c, qsock, path, cid);
+
+    ngx_log_debug5(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                   "quic %s socket is now #%uL:%uL:%uL (%s)",
+                   (*tmp) == qc->socket ? "active" : "backup",
+                   qsock->sid.seqnum, qsock->cid->seqnum,
+                   qsock->path->seqnum,
+                   ngx_quic_path_state_str(qsock->path));
+
+    /* restore active/backup pointer in quic connection */
+    *tmp = qsock;
+
     return NGX_OK;
+
+failed:
+
+    /*
+     * socket was closed, path and cid were preserved artifically
+     * to be reused, but it didn't happen, thus unref here
+     */
+
+    ngx_quic_unref_path(c, path);
+    ngx_quic_unref_client_id(c, cid);
+
+    return NGX_ERROR;
 }
 
 

diff --git a/src/event/quic/ngx_event_quic_socket.c b/src/event/quic/ngx_event_quic_socket.c
index ddde68f09f915f48a38cc2dc80c81ec4020226b9..3b507fca8104e3fd67033140a09b2857a4e9bb22 100644 (file)
--- a/src/event/quic/ngx_event_quic_socket.c
+++ b/src/event/quic/ngx_event_quic_socket.c
@@ -14,8 +14,6 @@ static ngx_int_t ngx_quic_create_temp_socket(ngx_connection_t *c,
     ngx_quic_connection_t *qc, ngx_str_t *dcid, ngx_quic_path_t *path,
     ngx_quic_client_id_t *cid);
 
-static void ngx_quic_unref_path(ngx_connection_t *c, ngx_quic_path_t *path);
-
 
 ngx_int_t
 ngx_quic_open_sockets(ngx_connection_t *c, ngx_quic_connection_t *qc,
@@ -207,7 +205,7 @@ ngx_quic_close_socket(ngx_connection_t *c, ngx_quic_socket_t *qsock)
 }
 
 
-static void
+void
 ngx_quic_unref_path(ngx_connection_t *c, ngx_quic_path_t *path)
 {
     ngx_quic_connection_t  *qc;

diff --git a/src/event/quic/ngx_event_quic_socket.h b/src/event/quic/ngx_event_quic_socket.h
index 1372822c01ec473ea7b1fa8d76da723584ebf743..72ed67ad0e621b9167634137a7762174a875ceba 100644 (file)
--- a/src/event/quic/ngx_event_quic_socket.h
+++ b/src/event/quic/ngx_event_quic_socket.h
@@ -22,6 +22,7 @@ ngx_int_t ngx_quic_listen(ngx_connection_t *c, ngx_quic_connection_t *qc,
     ngx_quic_socket_t *qsock);
 void ngx_quic_close_socket(ngx_connection_t *c, ngx_quic_socket_t *qsock);
 
+void ngx_quic_unref_path(ngx_connection_t *c, ngx_quic_path_t *path);
 void ngx_quic_connect(ngx_connection_t *c, ngx_quic_socket_t *qsock,
     ngx_quic_path_t *path, ngx_quic_client_id_t *cid);