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188 lines
6.2 KiB
188 lines
6.2 KiB
1 year ago
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commit bd77dd7e73e3530203be1c52c8a29d08270cb25d
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Wed Sep 13 14:10:56 2023 +0200
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CVE-2023-4527: Stack read overflow with large TCP responses in no-aaaa mode
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Without passing alt_dns_packet_buffer, __res_context_search can only
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store 2048 bytes (what fits into dns_packet_buffer). However,
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the function returns the total packet size, and the subsequent
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DNS parsing code in _nss_dns_gethostbyname4_r reads beyond the end
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of the stack-allocated buffer.
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Fixes commit f282cdbe7f436c75864e5640a4 ("resolv: Implement no-aaaa
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stub resolver option") and bug 30842.
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Conflicts:
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resolv/nss_dns/dns-host.c
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(missing dns_packet_buffer cleanup downstream)
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diff --git a/resolv/Makefile b/resolv/Makefile
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index ab8ad49b5318ad41..4f4eaf060443c128 100644
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--- a/resolv/Makefile
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+++ b/resolv/Makefile
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@@ -58,6 +58,7 @@ tests += \
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tst-resolv-edns \
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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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@@ -202,6 +203,7 @@ $(objpfx)tst-resolv-res_init-multi: $(objpfx)libresolv.so \
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$(objpfx)tst-resolv-res_init-thread: $(libdl) $(objpfx)libresolv.so \
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$(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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diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
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index ff0a0b6f7f1f4703..f678c7d7caa3a026 100644
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--- a/resolv/nss_dns/dns-host.c
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+++ b/resolv/nss_dns/dns-host.c
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@@ -392,7 +392,7 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
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else
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{
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n = __res_context_search (ctx, name, C_IN, T_A,
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- host_buffer.buf->buf, 2048, NULL,
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+ host_buffer.buf->buf, 2048, &host_buffer.ptr,
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NULL, NULL, NULL, NULL);
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if (n >= 0)
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status = gaih_getanswer_noaaaa (host_buffer.buf, n,
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diff --git a/resolv/tst-resolv-noaaaa-vc.c b/resolv/tst-resolv-noaaaa-vc.c
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new file mode 100644
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index 0000000000000000..9f5aebd99f2d74a2
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--- /dev/null
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+++ b/resolv/tst-resolv-noaaaa-vc.c
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@@ -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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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+ resolv_response_section (b, ns_s_an);
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+
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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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+
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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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+
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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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+
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+ _res.options |= RES_NOAAAA;
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+
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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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+
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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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+
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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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+
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+ check_addrinfo ("example.com", ai, ret, expected_result);
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+
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+ free (expected_result);
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+ freeaddrinfo (ai);
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+ }
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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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+
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+#include <support/test-driver.c>
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