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comparison src/event/quic/ngx_event_quic_migration.c @ 8913:40445fc7c403 quic

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QUIC: fixed migration during NAT rebinding. The RFC 9000 allows a packet from known CID arrive from unknown path: These requirements regarding connection ID reuse apply only to the sending of packets, as unintentional changes in path without a change in connection ID are possible. For example, after a period of network inactivity, NAT rebinding might cause packets to be sent on a new path when the client resumes sending. Before the patch, such packets were rejected with an error in the ngx_quic_check_migration() function. Removing the check makes the separate function excessive - remaining checks are early migration check and "disable_active_migration" check. The latter is a transport parameter sent to client and it should not be used by server. The server should send "disable_active_migration" "if the endpoint does not support active connection migration" (18.2). The support status depends on nginx configuration: to have migration working with multiple workers, you need bpf helper, available on recent Linux systems. The patch does not set "disable_active_migration" automatically and leaves it for the administrator. By default, active migration is enabled. RFC 900 says that it is ok to migrate if the peer violates "disable_active_migration" flag requirements: If the peer violates this requirement, the endpoint MUST either drop the incoming packets on that path without generating a Stateless Reset OR proceed with path validation and allow the peer to migrate. Generating a Stateless Reset or closing the connection would allow third parties in the network to cause connections to close by spoofing or otherwise manipulating observed traffic. So, nginx adheres to the second option and proceeds to path validation. Note: The ngtcp2 may be used for testing both active migration and NAT rebinding: ngtcp2/client --change-local-addr=200ms --delay-stream=500ms <ip> <port> <url> ngtcp2/client --change-local-addr=200ms --delay-stream=500ms --nat-rebinding \ <ip> <port> <url>
author Vladimir Homutov <vl@nginx.com>
date Mon, 29 Nov 2021 11:51:14 +0300
parents 50d73bf20e73
children bb1d1d9d76e2
comparison
equal deleted inserted replaced
8912:50d73bf20e73 8913:40445fc7c403
277 return NULL; 277 return NULL;
278 } 278 }
279 279
280 280
281 ngx_int_t 281 ngx_int_t
282 ngx_quic_check_migration(ngx_connection_t *c, ngx_quic_header_t *pkt)
283 {
284 ngx_quic_path_t *path;
285 ngx_quic_socket_t *qsock;
286 ngx_quic_connection_t *qc;
287
288 qc = ngx_quic_get_connection(c);
289
290 qsock = ngx_quic_get_socket(c);
291
292 if (c->udp->dgram == NULL) {
293 /* 2nd QUIC packet in first UDP datagram */
294 return NGX_OK;
295 }
296
297 path = ngx_quic_find_path(c, c->udp->dgram->sockaddr,
298 c->udp->dgram->socklen);
299 if (path == NULL) {
300 /* packet comes from unknown path, possibly migration */
301
302 if (qc->tp.disable_active_migration) {
303 ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, 0,
304 "quic migration disabled, dropping packet "
305 "from unknown path");
306 return NGX_DECLINED;
307 }
308
309 if (pkt->level != ssl_encryption_application) {
310 ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, 0,
311 "quic too early migration attempt");
312 return NGX_DECLINED;
313 }
314
315 return NGX_OK;
316 }
317
318 /* packet from known path */
319
320 if (qsock->path == NULL) {
321 /* client switched to previously unused server id */
322 return NGX_OK;
323 }
324
325 if (path == qsock->path) {
326 /* regular packet to expected path */
327 return NGX_OK;
328 }
329
330 /* client is trying to use server id already used on other path */
331
332 ngx_log_debug4(NGX_LOG_DEBUG_EVENT, c->log, 0,
333 "quic attempt to use socket #%uL:%uL:%uL with path #%uL",
334 qsock->sid.seqnum, qsock->cid->seqnum,
335 qsock->path->seqnum, path->seqnum);
336
337 return NGX_DECLINED;
338 }
339
340
341 ngx_int_t
342 ngx_quic_update_paths(ngx_connection_t *c, ngx_quic_header_t *pkt) 282 ngx_quic_update_paths(ngx_connection_t *c, ngx_quic_header_t *pkt)
343 { 283 {
344 off_t len; 284 off_t len;
345 ngx_quic_path_t *path; 285 ngx_quic_path_t *path;
346 ngx_quic_socket_t *qsock; 286 ngx_quic_socket_t *qsock;
347 ngx_quic_client_id_t *cid; 287 ngx_quic_client_id_t *cid;
348 ngx_quic_connection_t *qc; 288 ngx_quic_connection_t *qc;
349 289
350 qsock = ngx_quic_get_socket(c); 290 qsock = ngx_quic_get_socket(c);
351 path = qsock->path; 291
352 292 if (c->udp->dgram == NULL && qsock->path) {
353 if (path) { 293 /* 1st ever packet in connection, path already exists */
294 path = qsock->path;
354 goto update; 295 goto update;
355 } 296 }
356 297
357 path = ngx_quic_find_path(c, c->udp->dgram->sockaddr, 298 path = ngx_quic_find_path(c, c->udp->dgram->sockaddr,
358 c->udp->dgram->socklen); 299 c->udp->dgram->socklen);
361 path = ngx_quic_add_path(c, c->udp->dgram->sockaddr, 302 path = ngx_quic_add_path(c, c->udp->dgram->sockaddr,
362 c->udp->dgram->socklen); 303 c->udp->dgram->socklen);
363 if (path == NULL) { 304 if (path == NULL) {
364 return NGX_ERROR; 305 return NGX_ERROR;
365 } 306 }
307
308 if (qsock->path) {
309 /* NAT rebinding case: packet to same CID, but from new address */
310
311 ngx_quic_unref_path(c, qsock->path);
312
313 qsock->path = path;
314 path->refcnt++;
315
316 goto update;
317 }
318
319 } else if (qsock->path) {
320 goto update;
366 } 321 }
367 322
368 /* prefer unused client IDs if available */ 323 /* prefer unused client IDs if available */
369 cid = ngx_quic_next_client_id(c); 324 cid = ngx_quic_next_client_id(c);
370 if (cid == NULL) { 325 if (cid == NULL) {