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resolv: Allow short error responses to match any query (bug 31890)

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Reviewed-by: DJ Delorie <dj@redhat.com>
(cherry picked from commit 691a3b2e9b)
This commit is contained in:
Florian Weimer 2024-07-24 12:06:47 +02:00
parent 6daa771045
commit 8bbb8d7b16
4 changed files with 140 additions and 10 deletions
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6
NEWS
View File

@ -5,6 +5,12 @@ See the end for copying conditions.
Please send GNU C library bug reports via <https://sourceware.org/bugzilla/>
using `glibc' in the "product" field.
Version 2.41
The following bugs are resolved with this release:
[31890] resolv: Allow short error responses to match any DNS query
Version 2.40
Major new features:

3
resolv/Makefile
View File

@ -106,6 +106,7 @@ tests += \
tst-resolv-nondecimal \
tst-resolv-res_init-multi \
tst-resolv-search \
tst-resolv-short-response \
tst-resolv-trailing \
# This test calls __res_context_send directly, which is not exported
@ -299,6 +300,8 @@ $(objpfx)tst-resolv-nondecimal: $(objpfx)libresolv.so $(shared-thread-library)
$(objpfx)tst-resolv-qtypes: $(objpfx)libresolv.so $(shared-thread-library)
$(objpfx)tst-resolv-rotate: $(objpfx)libresolv.so $(shared-thread-library)
$(objpfx)tst-resolv-search: $(objpfx)libresolv.so $(shared-thread-library)
$(objpfx)tst-resolv-short-response: $(objpfx)libresolv.so \
$(shared-thread-library)
$(objpfx)tst-resolv-trailing: $(objpfx)libresolv.so $(shared-thread-library)
$(objpfx)tst-resolv-threads: $(objpfx)libresolv.so $(shared-thread-library)
$(objpfx)tst-resolv-txnid-collision: $(objpfx)libresolv.a \

29
resolv/res_send.c
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@ -1199,19 +1199,30 @@ send_dg(res_state statp,
}
/* Check for the correct header layout and a matching
question. */
question. Some recursive resolvers send REFUSED
without copying back the question section
(producing a response that is only HFIXEDSZ bytes
long). Skip query matching in this case. */
bool thisansp_error = (anhp->rcode == SERVFAIL ||
anhp->rcode == NOTIMP ||
anhp->rcode == REFUSED);
bool skip_query_match = (*thisresplenp == HFIXEDSZ
&& ntohs (anhp->qdcount) == 0
&& thisansp_error);
int matching_query = 0; /* Default to no matching query. */
if (!recvresp1
&& anhp->id == hp->id
&& __libc_res_queriesmatch (buf, buf + buflen,
*thisansp,
*thisansp + *thisanssizp))
&& (skip_query_match
|| __libc_res_queriesmatch (buf, buf + buflen,
*thisansp,
*thisansp + *thisanssizp)))
matching_query = 1;
if (!recvresp2
&& anhp->id == hp2->id
&& __libc_res_queriesmatch (buf2, buf2 + buflen2,
*thisansp,
*thisansp + *thisanssizp))
&& (skip_query_match
|| __libc_res_queriesmatch (buf2, buf2 + buflen2,
*thisansp,
*thisansp + *thisanssizp)))
matching_query = 2;
if (matching_query == 0)
/* Spurious UDP packet. Drop it and continue
@ -1221,9 +1232,7 @@ send_dg(res_state statp,
goto wait;
}
if (anhp->rcode == SERVFAIL ||
anhp->rcode == NOTIMP ||
anhp->rcode == REFUSED) {
if (thisansp_error) {
next_ns:
if (recvresp1 || (buf2 != NULL && recvresp2)) {
*resplen2 = 0;

112
resolv/tst-resolv-short-response.c Normal file
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@ -0,0 +1,112 @@
/* Test for spurious timeouts with short 12-byte responses (bug 31890).
Copyright (C) 2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <resolv.h>
#include <support/check.h>
#include <support/resolv_test.h>
#include <support/check_nss.h>
/* The rcode in the initial response. */
static volatile int rcode;
static void
response (const struct resolv_response_context *ctx,
struct resolv_response_builder *b,
const char *qname, uint16_t qclass, uint16_t qtype)
{
switch (ctx->server_index)
{
case 0:
/* First server times out. */
struct resolv_response_flags flags = {.rcode = rcode};
resolv_response_init (b, flags);
break;
case 1:
/* Second server sends reply. */
resolv_response_init (b, (struct resolv_response_flags) {});
resolv_response_add_question (b, qname, qclass, qtype);
resolv_response_section (b, ns_s_an);
resolv_response_open_record (b, qname, qclass, qtype, 0);
switch (qtype)
{
case T_A:
{
char ipv4[4] = {192, 0, 2, 17};
resolv_response_add_data (b, &ipv4, sizeof (ipv4));
}
break;
case T_AAAA:
{
char ipv6[16]
= {0x20, 0x01, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1};
resolv_response_add_data (b, &ipv6, sizeof (ipv6));
}
break;
default:
FAIL_EXIT1 ("unexpected TYPE%d query", qtype);
}
resolv_response_close_record (b);
break;
default:
FAIL_EXIT1 ("unexpected query to server %d", ctx->server_index);
}
}
static void
check_one (void)
{
/* The buggy 1-second query timeout results in 30 seconds of delay,
which triggers a test timeout failure. */
for (int i = 0; i < 10; ++i)
{
check_hostent ("www.example", gethostbyname ("www.example"),
"name: www.example\n"
"address: 192.0.2.17\n");
check_hostent ("www.example", gethostbyname2 ("www.example", AF_INET6),
"name: www.example\n"
"address: 2001:db8::1\n");
}
}
static int
do_test (void)
{
struct resolv_test *aux = resolv_test_start
((struct resolv_redirect_config)
{
.response_callback = response,
});
_res.options |= RES_SNGLKUP;
rcode = 2; /* SERVFAIL. */
check_one ();
rcode = 4; /* NOTIMP. */
check_one ();
rcode = 5; /* REFUSED. */
check_one ();
resolv_test_end (aux);
return 0;
}
#include <support/test-driver.c>