glibc/resolv/tst-resolv-noaaaa-vc.c
Florian Weimer bd77dd7e73 CVE-2023-4527: Stack read overflow with large TCP responses in no-aaaa mode
Without passing alt_dns_packet_buffer, __res_context_search can only
store 2048 bytes (what fits into dns_packet_buffer).  However,
the function returns the total packet size, and the subsequent
DNS parsing code in _nss_dns_gethostbyname4_r reads beyond the end
of the stack-allocated buffer.

Fixes commit f282cdbe7f ("resolv: Implement no-aaaa
stub resolver option") and bug 30842.
2023-09-13 14:10:56 +02:00

130 lines
3.8 KiB
C

/* Test the RES_NOAAAA resolver option with a large response.
Copyright (C) 2022-2023 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 <errno.h>
#include <netdb.h>
#include <resolv.h>
#include <stdbool.h>
#include <stdlib.h>
#include <support/check.h>
#include <support/check_nss.h>
#include <support/resolv_test.h>
#include <support/support.h>
#include <support/xmemstream.h>
/* Used to keep track of the number of queries. */
static volatile unsigned int queries;
/* If true, add a large TXT record at the start of the answer section. */
static volatile bool stuff_txt;
static void
response (const struct resolv_response_context *ctx,
struct resolv_response_builder *b,
const char *qname, uint16_t qclass, uint16_t qtype)
{
/* If not using TCP, just force its use. */
if (!ctx->tcp)
{
struct resolv_response_flags flags = {.tc = true};
resolv_response_init (b, flags);
resolv_response_add_question (b, qname, qclass, qtype);
return;
}
/* The test needs to send four queries, the first three are used to
grow the NSS buffer via the ERANGE handshake. */
++queries;
TEST_VERIFY (queries <= 4);
/* AAAA queries are supposed to be disabled. */
TEST_COMPARE (qtype, T_A);
TEST_COMPARE (qclass, C_IN);
TEST_COMPARE_STRING (qname, "example.com");
struct resolv_response_flags flags = {};
resolv_response_init (b, flags);
resolv_response_add_question (b, qname, qclass, qtype);
resolv_response_section (b, ns_s_an);
if (stuff_txt)
{
resolv_response_open_record (b, qname, qclass, T_TXT, 60);
int zero = 0;
for (int i = 0; i <= 15000; ++i)
resolv_response_add_data (b, &zero, sizeof (zero));
resolv_response_close_record (b);
}
for (int i = 0; i < 200; ++i)
{
resolv_response_open_record (b, qname, qclass, qtype, 60);
char ipv4[4] = {192, 0, 2, i + 1};
resolv_response_add_data (b, &ipv4, sizeof (ipv4));
resolv_response_close_record (b);
}
}
static int
do_test (void)
{
struct resolv_test *obj = resolv_test_start
((struct resolv_redirect_config)
{
.response_callback = response
});
_res.options |= RES_NOAAAA;
for (int do_stuff_txt = 0; do_stuff_txt < 2; ++do_stuff_txt)
{
queries = 0;
stuff_txt = do_stuff_txt;
struct addrinfo *ai = NULL;
int ret;
ret = getaddrinfo ("example.com", "80",
&(struct addrinfo)
{
.ai_family = AF_UNSPEC,
.ai_socktype = SOCK_STREAM,
}, &ai);
char *expected_result;
{
struct xmemstream mem;
xopen_memstream (&mem);
for (int i = 0; i < 200; ++i)
fprintf (mem.out, "address: STREAM/TCP 192.0.2.%d 80\n", i + 1);
xfclose_memstream (&mem);
expected_result = mem.buffer;
}
check_addrinfo ("example.com", ai, ret, expected_result);
free (expected_result);
freeaddrinfo (ai);
}
resolv_test_end (obj);
return 0;
}
#include <support/test-driver.c>