110 lines
3.2 KiB
C
110 lines
3.2 KiB
C
/*
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* IRC - Internet Relay Chat, ircd/random.c
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 1, or (at your option)
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* any later version.
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*
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* This program 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
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/** @file
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* @brief 32-bit pseudo-random number generator implementation.
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* @version $Id: random.c 1235 2004-10-06 00:22:09Z entrope $
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*/
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#include "config.h"
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#include "random.h"
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#include "client.h"
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#include "ircd_log.h"
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#include "ircd_md5.h"
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#include "ircd_reply.h"
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#include "send.h"
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#include <string.h>
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#include <sys/time.h>
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/** Pseudo-random number generator state. */
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static struct MD5Context localkey;
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/** Next byte position in #localkey to insert at. */
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static unsigned int localkey_pos;
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/** Add bytes to #localkey.
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* This should be fairly resistant to adding non-random bytes, but the
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* more random the bytes are, the harder it is for an attacker to
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* guess the internal state.
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* @param[in] buf Buffer of bytes to add.
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* @param[in] count Number of bytes to add.
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*/
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static void
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random_add_entropy(const char *buf, unsigned int count)
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{
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while (count--) {
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localkey.in[localkey_pos++] ^= *buf++;
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if (localkey_pos >= sizeof(localkey.in))
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localkey_pos = 0;
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}
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}
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/** Seed the PRNG with a string.
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* @param[in] from Client setting the seed (may be NULL).
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* @param[in] fields Input arguments (fields[0] is used).
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* @param[in] count Number of input arguments.
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* @return Non-zero on success, zero on error.
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*/
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int
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random_seed_set(struct Client* from, const char* const* fields, int count)
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{
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if (count < 1) {
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if (from) /* send an error */
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return need_more_params(from, "SET");
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else {
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log_write(LS_CONFIG, L_ERROR, 0, "Not enough fields in F line");
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return 0;
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}
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}
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random_add_entropy(fields[0], strlen(fields[0]));
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return 1;
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}
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/** Generate a pseudo-random number.
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* This uses the #localkey structure plus current time as input to
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* MD5, feeding most of the MD5 output back to #localkey and using one
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* output words as the pseudo-random output.
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* @return A 32-bit pseudo-random number.
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*/
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unsigned int ircrandom(void)
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{
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struct timeval tv;
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char usec[3];
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/* Add some randomness to the pool. */
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gettimeofday(&tv, 0);
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usec[0] = tv.tv_usec;
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usec[1] = tv.tv_usec >> 8;
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usec[2] = tv.tv_usec >> 16;
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random_add_entropy(usec, 3);
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/* Perform MD5 step. */
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localkey.buf[0] = 0x67452301;
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localkey.buf[1] = 0xefcdab89;
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localkey.buf[2] = 0x98badcfe;
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localkey.buf[3] = 0x10325476;
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MD5Transform(localkey.buf, (uint32*)localkey.in);
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/* Feed back 12 bytes of hash value into randomness pool. */
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random_add_entropy((char*)localkey.buf, 12);
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/* Return the final word of hash, which should not provide any
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* useful insight into current pool contents. */
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return localkey.buf[3];
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}
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