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no-aaaa-read-overflow.patch
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File no-aaaa-read-overflow.patch of Package glibc
From bd77dd7e73e3530203be1c52c8a29d08270cb25d Mon Sep 17 00:00:00 2001 From: Florian Weimer <fweimer@redhat.com> Date: Wed, 13 Sep 2023 14:10:56 +0200 Subject: [PATCH] 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 f282cdbe7f436c75864e5640a4 ("resolv: Implement no-aaaa stub resolver option") and bug 30842. --- NEWS | 6 +- resolv/Makefile | 2 + resolv/nss_dns/dns-host.c | 2 +- resolv/tst-resolv-noaaaa-vc.c | 129 ++++++++++++++++++++++++++++++++++ 4 files changed, 137 insertions(+), 2 deletions(-) create mode 100644 resolv/tst-resolv-noaaaa-vc.c diff --git a/resolv/Makefile b/resolv/Makefile index 054b1fa36c..2f99eb3862 100644 --- a/resolv/Makefile +++ b/resolv/Makefile @@ -102,6 +102,7 @@ tests += \ tst-resolv-invalid-cname \ tst-resolv-network \ tst-resolv-noaaaa \ + tst-resolv-noaaaa-vc \ tst-resolv-nondecimal \ tst-resolv-res_init-multi \ tst-resolv-search \ @@ -293,6 +294,7 @@ $(objpfx)tst-resolv-res_init-thread: $(objpfx)libresolv.so \ $(objpfx)tst-resolv-invalid-cname: $(objpfx)libresolv.so \ $(shared-thread-library) $(objpfx)tst-resolv-noaaaa: $(objpfx)libresolv.so $(shared-thread-library) +$(objpfx)tst-resolv-noaaaa-vc: $(objpfx)libresolv.so $(shared-thread-library) $(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) diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c index c8b77bbc35..119dc9f00f 100644 --- a/resolv/nss_dns/dns-host.c +++ b/resolv/nss_dns/dns-host.c @@ -427,7 +427,7 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat, { n = __res_context_search (ctx, name, C_IN, T_A, dns_packet_buffer, sizeof (dns_packet_buffer), - NULL, NULL, NULL, NULL, NULL); + &alt_dns_packet_buffer, NULL, NULL, NULL, NULL); if (n >= 0) status = gaih_getanswer_noaaaa (alt_dns_packet_buffer, n, &abuf, pat, errnop, herrnop, ttlp); diff --git a/resolv/tst-resolv-noaaaa-vc.c b/resolv/tst-resolv-noaaaa-vc.c new file mode 100644 index 0000000000..9f5aebd99f --- /dev/null +++ b/resolv/tst-resolv-noaaaa-vc.c @@ -0,0 +1,129 @@ +/* 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> -- 2.42.0
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