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272 lines
9.2 KiB
272 lines
9.2 KiB
commit c288e032ae107c48679ef3c46fb84af6de0a6baf |
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Author: Florian Weimer <fweimer@redhat.com> |
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Date: Tue Aug 30 10:02:49 2022 +0200 |
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resolv: Add internal __ns_name_length_uncompressed function |
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This function is useful for checking that the question name is |
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uncompressed (as it should be). |
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Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org> |
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(cherry picked from commit 78b1a4f0e49064e5dfb686c7cd87bd4df2640b29) |
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diff --git a/include/arpa/nameser.h b/include/arpa/nameser.h |
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index bb1dede187cf1500..6e4808f00d60caf9 100644 |
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--- a/include/arpa/nameser.h |
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+++ b/include/arpa/nameser.h |
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@@ -95,5 +95,13 @@ libc_hidden_proto (__ns_name_unpack) |
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extern __typeof (ns_samename) __libc_ns_samename; |
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libc_hidden_proto (__libc_ns_samename) |
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+/* Packet parser helper functions. */ |
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+ |
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+/* Verify that P points to an uncompressed domain name in wire format. |
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+ On success, return the length of the encoded name, including the |
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+ terminating null byte. On failure, return -1 and set errno. EOM |
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+ must point one past the last byte in the packet. */ |
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+int __ns_name_length_uncompressed (const unsigned char *p, |
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+ const unsigned char *eom) attribute_hidden; |
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# endif /* !_ISOMAC */ |
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#endif |
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diff --git a/resolv/Makefile b/resolv/Makefile |
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index 0b4fa30716af3b8a..308f18622a04965a 100644 |
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--- a/resolv/Makefile |
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+++ b/resolv/Makefile |
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@@ -40,6 +40,7 @@ routines := \ |
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inet_pton \ |
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ns_makecanon \ |
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ns_name_compress \ |
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+ ns_name_length_uncompressed \ |
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ns_name_ntop \ |
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ns_name_pack \ |
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ns_name_pton \ |
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@@ -112,6 +113,10 @@ tests-static += tst-resolv-txnid-collision |
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tests-internal += tst-ns_samebinaryname |
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tests-static += tst-ns_samebinaryname |
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+# Likewise for __ns_name_length_uncompressed. |
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+tests-internal += tst-ns_name_length_uncompressed |
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+tests-static += tst-ns_name_length_uncompressed |
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+ |
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# These tests need libdl. |
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ifeq (yes,$(build-shared)) |
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tests += \ |
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diff --git a/resolv/ns_name_length_uncompressed.c b/resolv/ns_name_length_uncompressed.c |
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new file mode 100644 |
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index 0000000000000000..51296b47efbf1849 |
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--- /dev/null |
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+++ b/resolv/ns_name_length_uncompressed.c |
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@@ -0,0 +1,72 @@ |
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+/* Skip over an uncompressed name in wire format. |
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+ Copyright (C) 2022 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 <arpa/nameser.h> |
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+#include <errno.h> |
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+#include <stdbool.h> |
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+ |
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+int |
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+__ns_name_length_uncompressed (const unsigned char *p, |
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+ const unsigned char *eom) |
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+{ |
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+ const unsigned char *start = p; |
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+ |
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+ while (true) |
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+ { |
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+ if (p == eom) |
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+ { |
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+ /* Truncated packet: no room for label length. */ |
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+ __set_errno (EMSGSIZE); |
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+ return -1; |
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+ } |
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+ |
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+ unsigned char b = *p; |
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+ ++p; |
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+ if (b == 0) |
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+ { |
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+ /* Root label. */ |
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+ size_t length = p - start; |
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+ if (length > NS_MAXCDNAME) |
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+ { |
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+ /* Domain name too long. */ |
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+ __set_errno (EMSGSIZE); |
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+ return -1; |
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+ } |
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+ return length; |
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+ } |
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+ |
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+ if (b <= 63) |
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+ { |
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+ /* Regular label. */ |
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+ if (b <= eom - p) |
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+ p += b; |
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+ else |
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+ { |
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+ /* Truncated packet: label incomplete. */ |
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+ __set_errno (EMSGSIZE); |
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+ return -1; |
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+ } |
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+ } |
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+ else |
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+ { |
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+ /* Compression reference or corrupted label length. */ |
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+ __set_errno (EMSGSIZE); |
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+ return -1; |
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+ } |
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+ } |
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+} |
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diff --git a/resolv/tst-ns_name_length_uncompressed.c b/resolv/tst-ns_name_length_uncompressed.c |
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new file mode 100644 |
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index 0000000000000000..c4a2904db75d1221 |
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--- /dev/null |
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+++ b/resolv/tst-ns_name_length_uncompressed.c |
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@@ -0,0 +1,135 @@ |
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+/* Test __ns_name_length_uncompressed. |
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+ Copyright (C) 2022 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 <arpa/nameser.h> |
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+#include <array_length.h> |
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+#include <errno.h> |
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+#include <stdio.h> |
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+#include <support/check.h> |
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+#include <support/next_to_fault.h> |
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+ |
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+/* Reference implementation based on other building blocks. */ |
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+static int |
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+reference_length (const unsigned char *p, const unsigned char *eom) |
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+{ |
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+ unsigned char buf[NS_MAXCDNAME]; |
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+ int n = __ns_name_unpack (p, eom, p, buf, sizeof (buf)); |
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+ if (n < 0) |
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+ return n; |
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+ const unsigned char *q = buf; |
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+ if (__ns_name_skip (&q, array_end (buf)) < 0) |
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+ return -1; |
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+ if (q - buf != n) |
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+ /* Compressed name. */ |
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+ return -1; |
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+ return n; |
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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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+ { |
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+ unsigned char buf[] = { 3, 'w', 'w', 'w', 0, 0, 0 }; |
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+ TEST_COMPARE (reference_length (buf, array_end (buf)), sizeof (buf) - 2); |
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+ TEST_COMPARE (__ns_name_length_uncompressed (buf, array_end (buf)), |
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+ sizeof (buf) - 2); |
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+ TEST_COMPARE (reference_length (array_end (buf) - 1, array_end (buf)), 1); |
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+ TEST_COMPARE (__ns_name_length_uncompressed (array_end (buf) - 1, |
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+ array_end (buf)), 1); |
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+ buf[4] = 0xc0; /* Forward compression reference. */ |
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+ buf[5] = 0x06; |
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+ TEST_COMPARE (reference_length (buf, array_end (buf)), -1); |
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+ TEST_COMPARE (__ns_name_length_uncompressed (buf, array_end (buf)), -1); |
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+ } |
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+ |
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+ struct support_next_to_fault ntf = support_next_to_fault_allocate (300); |
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+ |
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+ /* Buffer region with all possible bytes at start and end. */ |
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+ for (int length = 1; length <= 300; ++length) |
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+ { |
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+ unsigned char *end = (unsigned char *) ntf.buffer + ntf.length; |
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+ unsigned char *start = end - length; |
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+ memset (start, 'X', length); |
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+ for (int first = 0; first <= 255; ++first) |
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+ { |
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+ *start = first; |
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+ for (int last = 0; last <= 255; ++last) |
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+ { |
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+ start[length - 1] = last; |
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+ TEST_COMPARE (reference_length (start, end), |
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+ __ns_name_length_uncompressed (start, end)); |
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+ } |
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+ } |
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+ } |
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+ |
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+ /* Poor man's fuzz testing: patch two bytes. */ |
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+ { |
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+ unsigned char ref[] = |
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+ { |
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+ 7, 'e', 'x', 'a', 'm', 'p', 'l', 'e', 3, 'n', 'e', 't', 0, 0, 0 |
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+ }; |
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+ TEST_COMPARE (reference_length (ref, array_end (ref)), 13); |
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+ TEST_COMPARE (__ns_name_length_uncompressed (ref, array_end (ref)), 13); |
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+ |
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+ int good = 0; |
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+ int bad = 0; |
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+ for (int length = 1; length <= sizeof (ref); ++length) |
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+ { |
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+ unsigned char *end = (unsigned char *) ntf.buffer + ntf.length; |
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+ unsigned char *start = end - length; |
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+ memcpy (start, ref, length); |
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+ |
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+ for (int patch1_pos = 0; patch1_pos < length; ++patch1_pos) |
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+ { |
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+ for (int patch1_value = 0; patch1_value <= 255; ++patch1_value) |
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+ { |
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+ start[patch1_pos] = patch1_value; |
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+ for (int patch2_pos = 0; patch2_pos < length; ++patch2_pos) |
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+ { |
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+ for (int patch2_value = 0; patch2_value <= 255; |
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+ ++patch2_value) |
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+ { |
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+ start[patch2_pos] = patch2_value; |
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+ int expected = reference_length (start, end); |
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+ errno = EINVAL; |
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+ int actual |
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+ = __ns_name_length_uncompressed (start, end); |
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+ if (actual > 0) |
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+ ++good; |
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+ else |
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+ { |
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+ TEST_COMPARE (errno, EMSGSIZE); |
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+ ++bad; |
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+ } |
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+ TEST_COMPARE (expected, actual); |
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+ } |
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+ start[patch2_pos] = ref[patch2_pos]; |
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+ } |
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+ } |
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+ start[patch1_pos] = ref[patch1_pos]; |
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+ } |
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+ } |
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+ printf ("info: patched inputs with success: %d\n", good); |
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+ printf ("info: patched inputs with failure: %d\n", bad); |
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+ } |
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+ |
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+ support_next_to_fault_free (&ntf); |
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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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