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| 1 | +From 95d09cafae12d4b314df32027b97e828ecf798de Mon Sep 17 00:00:00 2001 |
| 2 | +From: Maxim Dounin < [email protected]> |
| 3 | +Date: Tue, 10 Oct 2023 15:13:39 +0300 |
| 4 | +Subject: [PATCH] HTTP/2: per-iteration stream handling limit. To ensure that |
| 5 | +attempts to flood servers with many streams are detected early, a limit of no |
| 6 | +more than 2 * max_concurrent_streams new streams per one event loop iteration |
| 7 | +was introduced. This limit is applied even if max_concurrent_streams is not |
| 8 | +yet reached - for example, if corresponding streams are handled synchronously |
| 9 | +or reset. |
| 10 | + |
| 11 | +Further, refused streams are now limited to maximum of max_concurrent_streams |
| 12 | +and 100, similarly to priority_limit initial value, providing some tolerance |
| 13 | +to clients trying to open several streams at the connection start, yet |
| 14 | +low tolerance to flooding attempts. |
| 15 | + |
| 16 | +Upstream-Status: Backport [https://github.com/nginx/nginx/commit/6ceef192e7af1c507826ac38a2d43f08bf265fb9] |
| 17 | +CVE: CVE-2023-44487 |
| 18 | + |
| 19 | +Signed-off-by: Meenali Gupta < [email protected]> |
| 20 | +--- |
| 21 | + src/http/v2/ngx_http_v2.c | 15 +++++++++++++++ |
| 22 | + src/http/v2/ngx_http_v2.h | 2 ++ |
| 23 | + 2 files changed, 17 insertions(+) |
| 24 | + |
| 25 | +diff --git a/src/http/v2/ngx_http_v2.c b/src/http/v2/ngx_http_v2.c |
| 26 | +index ea3f27c..1116e56 100644 |
| 27 | +--- a/src/http/v2/ngx_http_v2.c |
| 28 | ++++ b/src/http/v2/ngx_http_v2.c |
| 29 | +@@ -361,6 +361,7 @@ ngx_http_v2_read_handler(ngx_event_t *rev) |
| 30 | + ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http2 read handler"); |
| 31 | + |
| 32 | + h2c->blocked = 1; |
| 33 | ++ h2c->new_streams = 0; |
| 34 | + |
| 35 | + if (c->close) { |
| 36 | + c->close = 0; |
| 37 | +@@ -1321,6 +1322,14 @@ ngx_http_v2_state_headers(ngx_http_v2_connection_t *h2c, u_char *pos, |
| 38 | + goto rst_stream; |
| 39 | + } |
| 40 | + |
| 41 | ++ if (h2c->new_streams++ >= 2 * h2scf->concurrent_streams) { |
| 42 | ++ ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0, |
| 43 | ++ "client sent too many streams at once"); |
| 44 | ++ |
| 45 | ++ status = NGX_HTTP_V2_REFUSED_STREAM; |
| 46 | ++ goto rst_stream; |
| 47 | ++ } |
| 48 | ++ |
| 49 | + if (!h2c->settings_ack |
| 50 | + && !(h2c->state.flags & NGX_HTTP_V2_END_STREAM_FLAG) |
| 51 | + && h2scf->preread_size < NGX_HTTP_V2_DEFAULT_WINDOW) |
| 52 | +@@ -1386,6 +1395,12 @@ ngx_http_v2_state_headers(ngx_http_v2_connection_t *h2c, u_char *pos, |
| 53 | + |
| 54 | + rst_stream: |
| 55 | + |
| 56 | ++ if (h2c->refused_streams++ > ngx_max(h2scf->concurrent_streams, 100)) { |
| 57 | ++ ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0, |
| 58 | ++ "client sent too many refused streams"); |
| 59 | ++ return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_NO_ERROR); |
| 60 | ++ } |
| 61 | ++ |
| 62 | + if (ngx_http_v2_send_rst_stream(h2c, h2c->state.sid, status) != NGX_OK) { |
| 63 | + return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_INTERNAL_ERROR); |
| 64 | + } |
| 65 | +diff --git a/src/http/v2/ngx_http_v2.h b/src/http/v2/ngx_http_v2.h |
| 66 | +index 4e25293..b9daf92 100644 |
| 67 | +--- a/src/http/v2/ngx_http_v2.h |
| 68 | ++++ b/src/http/v2/ngx_http_v2.h |
| 69 | +@@ -124,6 +124,8 @@ struct ngx_http_v2_connection_s { |
| 70 | + ngx_uint_t processing; |
| 71 | + ngx_uint_t frames; |
| 72 | + ngx_uint_t idle; |
| 73 | ++ ngx_uint_t new_streams; |
| 74 | ++ ngx_uint_t refused_streams; |
| 75 | + ngx_uint_t priority_limit; |
| 76 | + |
| 77 | + ngx_uint_t pushing; |
| 78 | +-- |
| 79 | +2.40.0 |
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