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120 lines
4.7 KiB
120 lines
4.7 KiB
10 months ago
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From e5a741f94977840c58775b38f8ed830207f7e4d0 Mon Sep 17 00:00:00 2001
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From: Willy Tarreau <w@1wt.eu>
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Date: Tue, 8 Aug 2023 16:17:22 +0200
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Subject: [PATCH] BUG/MINOR: h1: do not accept '#' as part of the URI component
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Seth Manesse and Paul Plasil reported that the "path" sample fetch
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function incorrectly accepts '#' as part of the path component. This
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can in some cases lead to misrouted requests for rules that would apply
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on the suffix:
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use_backend static if { path_end .png .jpg .gif .css .js }
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Note that this behavior can be selectively configured using
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"normalize-uri fragment-encode" and "normalize-uri fragment-strip".
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The problem is that while the RFC says that this '#' must never be
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emitted, as often it doesn't suggest how servers should handle it. A
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diminishing number of servers still do accept it and trim it silently,
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while others are rejecting it, as indicated in the conversation below
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with other implementers:
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https://lists.w3.org/Archives/Public/ietf-http-wg/2023JulSep/0070.html
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Looking at logs from publicly exposed servers, such requests appear at
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a rate of roughly 1 per million and only come from attacks or poorly
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written web crawlers incorrectly following links found on various pages.
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Thus it looks like the best solution to this problem is to simply reject
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such ambiguous requests by default, and include this in the list of
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controls that can be disabled using "option accept-invalid-http-request".
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We're already rejecting URIs containing any control char anyway, so we
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should also reject '#'.
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In the H1 parser for the H1_MSG_RQURI state, there is an accelerated
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parser for bytes 0x21..0x7e that has been tightened to 0x24..0x7e (it
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should not impact perf since 0x21..0x23 are not supposed to appear in
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a URI anyway). This way '#' falls through the fine-grained filter and
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we can add the special case for it also conditionned by a check on the
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proxy's option "accept-invalid-http-request", with no overhead for the
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vast majority of valid URIs. Here this information is available through
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h1m->err_pos that's set to -2 when the option is here (so we don't need
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to change the API to expose the proxy). Example with a trivial GET
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through netcat:
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[08/Aug/2023:16:16:52.651] frontend layer1 (#2): invalid request
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backend <NONE> (#-1), server <NONE> (#-1), event #0, src 127.0.0.1:50812
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buffer starts at 0 (including 0 out), 16361 free,
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len 23, wraps at 16336, error at position 7
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H1 connection flags 0x00000000, H1 stream flags 0x00000810
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H1 msg state MSG_RQURI(4), H1 msg flags 0x00001400
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H1 chunk len 0 bytes, H1 body len 0 bytes :
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00000 GET /aa#bb HTTP/1.0\r\n
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00021 \r\n
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This should be progressively backported to all stable versions along with
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the following patch:
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REGTESTS: http-rules: add accept-invalid-http-request for normalize-uri tests
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Similar fixes for h2 and h3 will come in followup patches.
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Thanks to Seth Manesse and Paul Plasil for reporting this problem with
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detailed explanations.
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(cherry picked from commit 2eab6d354322932cfec2ed54de261e4347eca9a6)
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Signed-off-by: Amaury Denoyelle <adenoyelle@haproxy.com>
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(cherry picked from commit 9bf75c8e22a8f2537f27c557854a8803087046d0)
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Signed-off-by: Amaury Denoyelle <adenoyelle@haproxy.com>
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(cherry picked from commit 9facd01c9ac85fe9bcb331594b80fa08e7406552)
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Signed-off-by: Amaury Denoyelle <adenoyelle@haproxy.com>
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(cherry picked from commit 832b672eee54866c7a42a1d46078cc9ae0d544d9)
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Signed-off-by: Willy Tarreau <w@1wt.eu>
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---
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src/h1.c | 15 +++++++++++----
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1 file changed, 11 insertions(+), 4 deletions(-)
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diff --git a/src/h1.c b/src/h1.c
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index eeda311b7..91d3dc47a 100644
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--- a/src/h1.c
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+++ b/src/h1.c
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@@ -480,13 +480,13 @@ int h1_headers_to_hdr_list(char *start, const char *stop,
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case H1_MSG_RQURI:
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http_msg_rquri:
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#ifdef HA_UNALIGNED_LE
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- /* speedup: skip bytes not between 0x21 and 0x7e inclusive */
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+ /* speedup: skip bytes not between 0x24 and 0x7e inclusive */
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while (ptr <= end - sizeof(int)) {
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- int x = *(int *)ptr - 0x21212121;
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+ int x = *(int *)ptr - 0x24242424;
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if (x & 0x80808080)
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break;
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- x -= 0x5e5e5e5e;
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+ x -= 0x5b5b5b5b;
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if (!(x & 0x80808080))
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break;
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@@ -498,8 +498,15 @@ int h1_headers_to_hdr_list(char *start, const char *stop,
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goto http_msg_ood;
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}
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http_msg_rquri2:
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- if (likely((unsigned char)(*ptr - 33) <= 93)) /* 33 to 126 included */
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+ if (likely((unsigned char)(*ptr - 33) <= 93)) { /* 33 to 126 included */
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+ if (*ptr == '#') {
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+ if (h1m->err_pos < -1) /* PR_O2_REQBUG_OK not set */
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+ goto invalid_char;
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+ if (h1m->err_pos == -1) /* PR_O2_REQBUG_OK set: just log */
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+ h1m->err_pos = ptr - start + skip;
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+ }
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EAT_AND_JUMP_OR_RETURN(ptr, end, http_msg_rquri2, http_msg_ood, state, H1_MSG_RQURI);
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+ }
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if (likely(HTTP_IS_SPHT(*ptr))) {
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sl.rq.u.len = ptr - sl.rq.u.ptr;
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--
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2.43.0
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