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From 4ea972b7edd7e36610e8cde18bf7a8149d7bac4f 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.
(cherry picked from commit bd77dd7e73e3530203be1c52c8a29d08270cb25d)
Upstream-Status: Backport [https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=4ea972b7edd7e36610e8cde18bf7a8149d7bac4f]
CVE: CVE-2023-4527
Signed-off-by: Yash Shinde <Yash.Shinde@windriver.com>
---
NEWS | 7 ++
resolv/Makefile | 2 +
resolv/nss_dns/dns-host.c | 2 +-
resolv/tst-resolv-noaaaa-vc.c | 129 ++++++++++++++++++++++++++++++++++
4 files changed, 139 insertions(+), 1 deletion(-)
create mode 100644 resolv/tst-resolv-noaaaa-vc.c
diff --git a/NEWS b/NEWS
--- a/NEWS
+++ b/NEWS
@@ -25,6 +25,7 @@
[30101] gmon: fix memory corruption issues
[30125] dynamic-link: [regression, bisected] glibc-2.37 creates new
symlink for libraries without soname
+ [30842] Stack read overflow in getaddrinfo in no-aaaa mode (CVE-2023-4527)
[30151] gshadow: Matching sgetsgent, sgetsgent_r ERANGE handling
[30163] posix: Fix system blocks SIGCHLD erroneously
[30305] x86_64: Fix asm constraints in feraiseexcept
@@ -54,6 +55,12 @@
heap and prints it to the target log file, potentially revealing a
portion of the contents of the heap.
+ CVE-2023-4527: If the system is configured in no-aaaa mode via
+ /etc/resolv.conf, getaddrinfo is called for the AF_UNSPEC address
+ family, and a DNS response is received over TCP that is larger than
+ 2048 bytes, getaddrinfo may potentially disclose stack contents via
+ the returned address data, or crash.
+
The following bugs are resolved with this release:
[12154] network: Cannot resolve hosts which have wildcard aliases
diff --git a/resolv/Makefile b/resolv/Makefile
--- a/resolv/Makefile
+++ b/resolv/Makefile
@@ -101,6 +101,7 @@
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 \
@@ -292,6 +293,7 @@
$(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
--- a/resolv/nss_dns/dns-host.c
+++ b/resolv/nss_dns/dns-host.c
@@ -427,7 +427,7 @@
{
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
--- /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>
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