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changeset 8911:b09f055daa4e quic

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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.
author Vladimir Homutov <vl@nginx.com>
date Thu, 18 Nov 2021 14:19:36 +0300
parents f8848f5a1014
children 50d73bf20e73
files src/event/quic/ngx_event_quic_connid.c src/event/quic/ngx_event_quic_socket.c src/event/quic/ngx_event_quic_socket.h
diffstat 3 files changed, 56 insertions(+), 31 deletions(-) [+]
line wrap: on
line diff
--- 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_fra
         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_fra
         tmp = &qc->backup;
 
     } else {
-        tmp = NULL;
-    }
 
-    if (ngx_quic_create_sockets(c) != NGX_OK) {
-        return NGX_ERROR;
-    }
+        ngx_quic_close_socket(c, qsock);
 
-    if (tmp) {
-        /* replace socket in use (active or backup) */
-
-        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;
 
-        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));
+    /* ensure that closing_socket will not drop path and cid */
+    path->refcnt++;
+    cid->refcnt++;
+
+    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;
 }
 
 
--- 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_so
     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 *
 }
 
 
-static void
+void
 ngx_quic_unref_path(ngx_connection_t *c, ngx_quic_path_t *path)
 {
     ngx_quic_connection_t  *qc;
--- 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
     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);