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c288e032ae
This function is useful for checking that the question name is
uncompressed (as it should be).
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
(cherry picked from commit 78b1a4f0e4)
73 lines
2.0 KiB
C
73 lines
2.0 KiB
C
/* 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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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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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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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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#include <arpa/nameser.h>
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#include <errno.h>
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#include <stdbool.h>
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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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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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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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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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