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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.
This commit is contained in:
Florian Weimer
parent
c8fa383f4c
commit
bd77dd7e73
6
NEWS
6
NEWS
@ -42,7 +42,11 @@ Changes to build and runtime requirements:
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Security related changes:
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[Add security related changes here]
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CVE-2023-4527: If the system is configured in no-aaaa mode via
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/etc/resolv.conf, getaddrinfo is called for the AF_UNSPEC address
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family, and a DNS response is received over TCP that is larger than
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2048 bytes, getaddrinfo may potentially disclose stack contents via
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the returned address data, or crash.
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The following bugs are resolved with this release:
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@ -102,6 +102,7 @@ tests += \
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tst-resolv-invalid-cname \
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tst-resolv-network \
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tst-resolv-noaaaa \
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tst-resolv-noaaaa-vc \
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tst-resolv-nondecimal \
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tst-resolv-res_init-multi \
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tst-resolv-search \
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@ -293,6 +294,7 @@ $(objpfx)tst-resolv-res_init-thread: $(objpfx)libresolv.so \
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$(objpfx)tst-resolv-invalid-cname: $(objpfx)libresolv.so \
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$(shared-thread-library)
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$(objpfx)tst-resolv-noaaaa: $(objpfx)libresolv.so $(shared-thread-library)
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$(objpfx)tst-resolv-noaaaa-vc: $(objpfx)libresolv.so $(shared-thread-library)
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$(objpfx)tst-resolv-nondecimal: $(objpfx)libresolv.so $(shared-thread-library)
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$(objpfx)tst-resolv-qtypes: $(objpfx)libresolv.so $(shared-thread-library)
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$(objpfx)tst-resolv-rotate: $(objpfx)libresolv.so $(shared-thread-library)
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@ -427,7 +427,7 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
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{
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n = __res_context_search (ctx, name, C_IN, T_A,
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dns_packet_buffer, sizeof (dns_packet_buffer),
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NULL, NULL, NULL, NULL, NULL);
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&alt_dns_packet_buffer, NULL, NULL, NULL, NULL);
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if (n >= 0)
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status = gaih_getanswer_noaaaa (alt_dns_packet_buffer, n,
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&abuf, pat, errnop, herrnop, ttlp);
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129
resolv/tst-resolv-noaaaa-vc.c
Normal file
129
resolv/tst-resolv-noaaaa-vc.c
Normal file
@ -0,0 +1,129 @@
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/* Test the RES_NOAAAA resolver option with a large response.
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Copyright (C) 2022-2023 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <netdb.h>
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#include <resolv.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include <support/check.h>
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#include <support/check_nss.h>
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#include <support/resolv_test.h>
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#include <support/support.h>
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#include <support/xmemstream.h>
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/* Used to keep track of the number of queries. */
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static volatile unsigned int queries;
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/* If true, add a large TXT record at the start of the answer section. */
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static volatile bool stuff_txt;
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static void
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response (const struct resolv_response_context *ctx,
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struct resolv_response_builder *b,
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const char *qname, uint16_t qclass, uint16_t qtype)
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{
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/* If not using TCP, just force its use. */
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if (!ctx->tcp)
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{
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struct resolv_response_flags flags = {.tc = true};
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resolv_response_init (b, flags);
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resolv_response_add_question (b, qname, qclass, qtype);
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return;
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}
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/* The test needs to send four queries, the first three are used to
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grow the NSS buffer via the ERANGE handshake. */
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++queries;
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TEST_VERIFY (queries <= 4);
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/* AAAA queries are supposed to be disabled. */
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TEST_COMPARE (qtype, T_A);
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TEST_COMPARE (qclass, C_IN);
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TEST_COMPARE_STRING (qname, "example.com");
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struct resolv_response_flags flags = {};
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resolv_response_init (b, flags);
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resolv_response_add_question (b, qname, qclass, qtype);
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resolv_response_section (b, ns_s_an);
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if (stuff_txt)
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{
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resolv_response_open_record (b, qname, qclass, T_TXT, 60);
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int zero = 0;
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for (int i = 0; i <= 15000; ++i)
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resolv_response_add_data (b, &zero, sizeof (zero));
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resolv_response_close_record (b);
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}
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for (int i = 0; i < 200; ++i)
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{
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resolv_response_open_record (b, qname, qclass, qtype, 60);
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char ipv4[4] = {192, 0, 2, i + 1};
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resolv_response_add_data (b, &ipv4, sizeof (ipv4));
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resolv_response_close_record (b);
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}
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}
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static int
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do_test (void)
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{
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struct resolv_test *obj = resolv_test_start
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((struct resolv_redirect_config)
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{
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.response_callback = response
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});
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_res.options |= RES_NOAAAA;
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for (int do_stuff_txt = 0; do_stuff_txt < 2; ++do_stuff_txt)
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{
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queries = 0;
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stuff_txt = do_stuff_txt;
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struct addrinfo *ai = NULL;
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int ret;
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ret = getaddrinfo ("example.com", "80",
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&(struct addrinfo)
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{
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.ai_family = AF_UNSPEC,
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.ai_socktype = SOCK_STREAM,
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}, &ai);
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char *expected_result;
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{
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struct xmemstream mem;
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xopen_memstream (&mem);
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for (int i = 0; i < 200; ++i)
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fprintf (mem.out, "address: STREAM/TCP 192.0.2.%d 80\n", i + 1);
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xfclose_memstream (&mem);
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expected_result = mem.buffer;
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}
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check_addrinfo ("example.com", ai, ret, expected_result);
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free (expected_result);
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freeaddrinfo (ai);
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}
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resolv_test_end (obj);
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return 0;
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}
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#include <support/test-driver.c>
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