315 lines
11 KiB
Diff
315 lines
11 KiB
Diff
commit 9344c796f7a4ac8f2c59de63f3e1e936b51e817d
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Author: Carlos O'Donell <carlos@redhat.com>
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Date: Fri Mar 20 17:14:33 2026 -0400
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resolv: Check hostname for validity (CVE-2026-4438)
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The processed hostname in getanswer_ptr should be correctly checked to
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avoid invalid characters from being allowed, including shell
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metacharacters. It is a security issue to fail to check the returned
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hostname for validity.
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A regression test is added for invalid metacharacters and other cases
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of invalid or valid characters.
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No regressions on x86_64-linux-gnu.
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Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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(cherry picked from commit e10977481f4db4b2a3ce34fa4c3a1e26651ae312)
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diff --git a/resolv/Makefile b/resolv/Makefile
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index 8dba948b632d3abc..87a5c1ccc6dabc8a 100644
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--- a/resolv/Makefile
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+++ b/resolv/Makefile
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@@ -107,6 +107,7 @@ tests += \
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tst-resolv-dns-section \
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tst-resolv-edns \
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tst-resolv-invalid-cname \
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+ tst-resolv-invalid-ptr \
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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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@@ -305,6 +306,8 @@ $(objpfx)tst-resolv-res_init-thread: $(objpfx)libresolv.so \
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$(shared-thread-library)
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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-invalid-ptr: $(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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diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
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index 74a7c08d0f055d6e..b8f5d61b2ae20a4e 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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@@ -866,7 +866,7 @@ getanswer_ptr (unsigned char *packet, size_t packetlen,
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char hname[MAXHOSTNAMELEN + 1];
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if (__ns_name_unpack (c.begin, c.end, rr.rdata,
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name_buffer, sizeof (name_buffer)) < 0
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- || !__res_binary_hnok (expected_name)
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+ || !__res_binary_hnok (name_buffer)
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|| __ns_name_ntop (name_buffer, hname, sizeof (hname)) < 0)
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{
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*h_errnop = NO_RECOVERY;
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diff --git a/resolv/tst-resolv-invalid-ptr.c b/resolv/tst-resolv-invalid-ptr.c
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new file mode 100644
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index 0000000000000000..0c802ab96780efb0
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--- /dev/null
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+++ b/resolv/tst-resolv-invalid-ptr.c
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@@ -0,0 +1,255 @@
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+/* Test handling of invalid T_PTR results (bug 34015).
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+ Copyright (C) 2022-2026 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 <array_length.h>
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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 <stdlib.h>
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+#include <string.h>
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+#include <support/check.h>
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+#include <support/format_nss.h>
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+#include <support/resolv_test.h>
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+#include <support/support.h>
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+
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+/* Name of test, the answer, the expected error return, and if we
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+ expect the call to fail. */
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+struct item {
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+ const char *test;
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+ const char *answer;
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+ int expected;
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+ bool fail;
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+};
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+
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+static const struct item test_items[] =
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+ {
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+ /* Test for invalid characters. */
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+ { "Invalid use of \"|\"",
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+ "test.|.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"&\"",
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+ "test.&.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \";\"",
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+ "test.;.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"<\"",
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+ "test.<.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \">\"",
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+ "test.>.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"(\"",
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+ "test.(.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \")\"",
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+ "test.).ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"$\"",
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+ "test.$.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"`\"",
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+ "test.`.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"\\\"",
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+ "test.\\.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"\'\"",
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+ "test.'.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"\"\"",
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+ "test.\".ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \" \"",
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+ "test. .ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"\\t\"",
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+ "test.\t.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"\\n\"",
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+ "test.\n.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"\\r\"",
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+ "test.\r.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"*\"",
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+ "test.*.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"?\"",
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+ "test.?.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"[\"",
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+ "test.[.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"]\"",
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+ "test.].ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \",\"",
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+ "test.,.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"~\"",
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+ "test.~.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \":\"",
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+ "test.:.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"!\"",
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+ "test.!.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"@\"",
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+ "test.@.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"#\"",
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+ "test.#.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"%\"",
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+ "test.%%.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of \"^\"",
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+ "test.^.ptr.example", NO_RECOVERY, true },
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+
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+ /* Test for invalid UTF-8 characters (2-byte, 4-byte, 6-byte). */
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+ { "Invalid use of UTF-8 (2-byte, U+00C0-U+00C2)",
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+ "ÁÂÃ.test.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of UTF-8 (4-byte, U+0750-U+0752)",
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+ "ݐݑݒ.test.ptr.example", NO_RECOVERY, true },
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+ { "Invalid use of UTF-8 (6-byte, U+0904-U+0906)",
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+ "ऄअआ.test.ptr.example", NO_RECOVERY, true },
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+
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+ /* Test for "-" which may be valid depending on position. */
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+ { "Invalid leading \"-\"",
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+ "-test.ptr.example", NO_RECOVERY, true },
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+ { "Valid trailing \"-\"",
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+ "test-.ptr.example", 0, false },
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+ { "Valid mid-label use of \"-\"",
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+ "te-st.ptr.example", 0, false },
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+
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+ /* Test for "_" which is always valid in any position. */
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+ { "Valid leading use of \"_\"",
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+ "_test.ptr.example", 0, false },
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+ { "Valid mid-label use of \"_\"",
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+ "te_st.ptr.example", 0, false },
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+ { "Valid trailing use of \"_\"",
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+ "test_.ptr.example", 0, false },
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+
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+ /* Sanity test the broader set [A-Za-z0-9_-] of valid characters. */
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+ { "Valid \"[A-Z]\"",
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+ "test.ABCDEFGHIJKLMNOPQRSTUVWXYZ.ptr.example", 0, false },
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+ { "Valid \"[a-z]\"",
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+ "test.abcdefghijklmnopqrstuvwxyz.ptr.example", 0, false },
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+ { "Valid \"[0-9]\"",
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+ "test.0123456789.ptr.example", 0, false },
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+ { "Valid mixed use of \"[A-Za-z0-9_-]\"",
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+ "test.012abcABZ_-.ptr.example", 0, false },
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+ };
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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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+ TEST_COMPARE (qclass, C_IN);
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+
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+ /* We only test PTR. */
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+ TEST_COMPARE (qtype, T_PTR);
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+
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+ unsigned int count, count1;
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+ char *tail = NULL;
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+
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+ /* The test implementation can handle up to 255 tests. */
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+ if (strstr (qname, "in-addr.arpa") != NULL
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+ && sscanf (qname, "%u.%ms", &count, &tail) == 2)
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+ TEST_COMPARE_STRING (tail, "0.168.192.in-addr.arpa");
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+ else if (sscanf (qname, "%x.%x.%ms", &count, &count1, &tail) == 3)
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+ {
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+ TEST_COMPARE_STRING (tail, "\
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+0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa");
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+ count |= count1 << 4;
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+ }
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+ else
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+ FAIL_EXIT1 ("invalid QNAME: %s\n", qname);
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+ free (tail);
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+
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+ /* Cross check. Count has a fixed bound (soft limit). */
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+ TEST_VERIFY (count >= 0 && count <= 255);
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+
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+ /* We have a fixed number of tests (hard limit). */
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+ TEST_VERIFY_EXIT (count < array_length (test_items));
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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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+ resolv_response_section (b, ns_s_an);
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+
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+ /* Actual answer record. */
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+ resolv_response_open_record (b, qname, qclass, qtype, 60);
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+
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+ /* Record the answer. */
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+ resolv_response_add_name (b, test_items[count].answer);
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+ resolv_response_close_record (b);
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+}
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+
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+/* Perform one check using a reverse lookup. */
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+static void
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+check_reverse (int af, int count)
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+{
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+ TEST_VERIFY (af == AF_INET || af == AF_INET6);
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+ TEST_VERIFY_EXIT (count < array_length (test_items));
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+
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+ /* Generate an address to query for each test. */
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+ char addr[sizeof (struct in6_addr)] = { 0 };
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+ socklen_t addrlen;
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+ if (af == AF_INET)
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+ {
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+ addr[0] = (char) 192;
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+ addr[1] = (char) 168;
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+ addr[2] = (char) 0;
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+ addr[3] = (char) count;
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+ addrlen = 4;
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+ }
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+ else
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+ {
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+ addr[0] = 0x20;
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+ addr[1] = 0x01;
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+ addr[2] = 0x0d;
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+ addr[3] = 0xb8;
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+ addr[4] = addr[5] = addr[6] = addr[7] = 0x0;
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+ addr[8] = addr[9] = addr[10] = addr[11] = 0x0;
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+ addr[12] = 0x0;
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+ addr[13] = 0x0;
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+ addr[14] = 0x0;
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+ addr[15] = (char) count;
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+ addrlen = 16;
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+ }
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+
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+ h_errno = 0;
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+ struct hostent *answer = gethostbyaddr (addr, addrlen, af);
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+
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+ /* Verify h_errno is as expected. */
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+ TEST_COMPARE (h_errno, test_items[count].expected);
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+ if (h_errno != test_items[count].expected)
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+ /* And print more information if it's not. */
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+ printf ("INFO: %s\n", test_items[count].test);
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+
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+ if (test_items[count].fail)
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+ {
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+ /* We expected a failure so verify answer is NULL. */
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+ TEST_VERIFY (answer == NULL);
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+ /* If it's not NULL we should print out what we received. */
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+ if (answer != NULL)
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+ printf ("error: unexpected success: %s\n",
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+ support_format_hostent (answer));
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+ }
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+ else
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+ /* We don't expect a failure so answer must be valid. */
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+ TEST_COMPARE_STRING (answer->h_name, test_items[count].answer);
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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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+ for (int i = 0; i < array_length (test_items); i++)
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+ {
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+ check_reverse (AF_INET, i);
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+ check_reverse (AF_INET6, i);
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+ }
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+ resolv_test_end (obj);
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+
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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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