diff --git a/bz2169510-reject-empty-http-header-fields.patch b/bz2169510-reject-empty-http-header-fields.patch new file mode 100644 index 0000000..5623d7a --- /dev/null +++ b/bz2169510-reject-empty-http-header-fields.patch @@ -0,0 +1,164 @@ +From 486cd730485c8a119ef65b3f792134b56e7941b4 Mon Sep 17 00:00:00 2001 +From: Willy Tarreau +Date: Thu, 9 Feb 2023 21:36:54 +0100 +Subject: [PATCH] BUG/CRITICAL: http: properly reject empty http header field + names + +The HTTP header parsers surprizingly accepts empty header field names, +and this is a leftover from the original code that was agnostic to this. + +When muxes were introduced, for H2 first, the HPACK decompressor needed +to feed headers lists, and since empty header names were strictly +forbidden by the protocol, the lists of headers were purposely designed +to be terminated by an empty header field name (a principle that is +similar to H1's empty line termination). This principle was preserved +and generalized to other protocols migrated to muxes (H1/FCGI/H3 etc) +without anyone ever noticing that the H1 parser was still able to deliver +empty header field names to this list. In addition to this it turns out +that the HPACK decompressor, despite a comment in the code, may +successfully decompress an empty header field name, and this mistake +was propagated to the QPACK decompressor as well. + +The impact is that an empty header field name may be used to truncate +the list of headers and thus make some headers disappear. While for +H2/H3 the impact is limited as haproxy sees a request with missing +headers, and headers are not used to delimit messages, in the case of +HTTP/1, the impact is significant because the presence (and sometimes +contents) of certain sensitive headers is detected during the parsing. +Thus, some of these headers may be seen, marked as present, their value +extracted, but never delivered to upper layers and obviously not +forwarded to the other side either. This can have for consequence that +certain important header fields such as Connection, Upgrade, Host, +Content-length, Transfer-Encoding etc are possibly seen as different +between what haproxy uses to parse/forward/route and what is observed +in http-request rules and of course, forwarded. One direct consequence +is that it is possible to exploit this property in HTTP/1 to make +affected versions of haproxy forward more data than is advertised on +the other side, and bypass some access controls or routing rules by +crafting extraneous requests. Note, however, that responses to such +requests will normally not be passed back to the client, but this can +still cause some harm. + +This specific risk can be mostly worked around in configuration using +the following rule that will rely on the bug's impact to precisely +detect the inconsistency between the known body size and the one +expected to be advertised to the server (the rule works from 2.0 to +2.8-dev): + + http-request deny if { fc_http_major 1 } !{ req.body_size 0 } !{ req.hdr(content-length) -m found } !{ req.hdr(transfer-encoding) -m found } !{ method CONNECT } + +This will exclusively block such carefully crafted requests delivered +over HTTP/1. HTTP/2 and HTTP/3 do not need content-length, and a body +that arrives without being announced with a content-length will be +forwarded using transfer-encoding, hence will not cause discrepancies. +In HAProxy 2.0 in legacy mode ("no option http-use-htx"), this rule will +simply have no effect but will not cause trouble either. + +A clean solution would consist in modifying the loops iterating over +these headers lists to check the header name's pointer instead of its +length (since both are zero at the end of the list), but this requires +to touch tens of places and it's very easy to miss one. Functions such +as htx_add_header(), htx_add_trailer(), htx_add_all_headers() would be +good starting points for such a possible future change. + +Instead the current fix focuses on blocking empty headers where they +are first inserted, hence in the H1/HPACK/QPACK decoders. One benefit +of the current solution (for H1) is that it allows "show errors" to +report a precise diagnostic when facing such invalid HTTP/1 requests, +with the exact location of the problem and the originating address: + + $ printf "GET / HTTP/1.1\r\nHost: localhost\r\n:empty header\r\n\r\n" | nc 0 8001 + HTTP/1.1 400 Bad request + Content-length: 90 + Cache-Control: no-cache + Connection: close + Content-Type: text/html + +

400 Bad request

+ Your browser sent an invalid request. + + + $ socat /var/run/haproxy.stat <<< "show errors" + Total events captured on [10/Feb/2023:16:29:37.530] : 1 + + [10/Feb/2023:16:29:34.155] frontend decrypt (#2): invalid request + backend (#-1), server (#-1), event #0, src 127.0.0.1:31092 + buffer starts at 0 (including 0 out), 16334 free, + len 50, wraps at 16336, error at position 33 + H1 connection flags 0x00000000, H1 stream flags 0x00000810 + H1 msg state MSG_HDR_NAME(17), H1 msg flags 0x00001410 + H1 chunk len 0 bytes, H1 body len 0 bytes : + + 00000 GET / HTTP/1.1\r\n + 00016 Host: localhost\r\n + 00033 :empty header\r\n + 00048 \r\n + +I want to address sincere and warm thanks for their great work to the +team composed of the following security researchers who found the issue +together and reported it: Bahruz Jabiyev, Anthony Gavazzi, and Engin +Kirda from Northeastern University, Kaan Onarlioglu from Akamai +Technologies, Adi Peleg and Harvey Tuch from Google. And kudos to Amaury +Denoyelle from HAProxy Technologies for spotting that the HPACK and +QPACK decoders would let this pass despite the comment explicitly +saying otherwise. + +This fix must be backported as far as 2.0. The QPACK changes can be +dropped before 2.6. In 2.0 there is also the equivalent code for legacy +mode, which doesn't suffer from the list truncation, but it would better +be fixed regardless. + +CVE-2023-25725 was assigned to this issue. + +(cherry picked from commit a8598a2eb11b6c989e81f0dbf10be361782e8d32) +Signed-off-by: Willy Tarreau +(cherry picked from commit a0e561ad7f29ed50c473f5a9da664267b60d1112) +Signed-off-by: Willy Tarreau +(cherry picked from commit 73be199c4f5f1ed468161a4c5e10ca77cd5989d8) +[wt: dropped QPACK changes for 2.5] +Signed-off-by: Willy Tarreau +(cherry picked from commit f8b2b88aeae15dc3b261cd3749277ae75caf9db8) +Signed-off-by: Willy Tarreau +--- + src/h1.c | 4 ++++ + src/hpack-dec.c | 9 +++++++++ + 2 files changed, 13 insertions(+) + +diff --git a/src/h1.c b/src/h1.c +index 4c2e234c5..73de48be0 100644 +--- a/src/h1.c ++++ b/src/h1.c +@@ -750,6 +750,10 @@ int h1_headers_to_hdr_list(char *start, const char *stop, + + if (likely(*ptr == ':')) { + col = ptr - start; ++ if (col <= sol) { ++ state = H1_MSG_HDR_NAME; ++ goto http_msg_invalid; ++ } + EAT_AND_JUMP_OR_RETURN(ptr, end, http_msg_hdr_l1_sp, http_msg_ood, state, H1_MSG_HDR_L1_SP); + } + +diff --git a/src/hpack-dec.c b/src/hpack-dec.c +index 04f3d9ffa..ed39007d1 100644 +--- a/src/hpack-dec.c ++++ b/src/hpack-dec.c +@@ -420,6 +420,15 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len, + /* and are correctly filled here */ + } + ++ /* We must not accept empty header names (forbidden by the spec and used ++ * as a list termination). ++ */ ++ if (!name.len) { ++ hpack_debug_printf("##ERR@%d##\n", __LINE__); ++ ret = -HPACK_ERR_INVALID_ARGUMENT; ++ goto leave; ++ } ++ + /* here's what we have here : + * - name.len > 0 + * - value is filled with either const data or data allocated from tmp +-- +2.37.3 + diff --git a/haproxy.spec b/haproxy.spec index cb6d884..a9671a1 100644 --- a/haproxy.spec +++ b/haproxy.spec @@ -8,7 +8,7 @@ Name: haproxy Version: 2.4.17 -Release: 5%{?dist} +Release: 6%{?dist} Summary: HAProxy reverse proxy for high availability environments License: GPLv2+ @@ -23,6 +23,7 @@ Source5: %{name}.sysusers Source6: halog.1 Patch0: bz2161140-refuse-response-end-stream-flag.patch +Patch1: bz2169510-reject-empty-http-header-fields.patch BuildRequires: gcc BuildRequires: lua-devel @@ -53,6 +54,7 @@ availability environments. Indeed, it can: %prep %setup -q %patch0 -p1 +%patch1 -p1 %build regparm_opts= @@ -135,6 +137,9 @@ done %{_sysusersdir}/%{name}.conf %changelog +* Mon Feb 27 2023 Ryan O'Hara - 2.4.17-6 +- Reject empty http header field names (CVE-2023-25725, #2169510) + * Mon Feb 27 2023 Ryan O'Hara - 2.4.17-5 - Refuse interim responses with end-stream flag set (CVE-2023-0056, #2161140)