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1 | /* | |
2 | * IRC - Internet Relay Chat, ircd/random.c | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 1, or (at your option) | |
7 | * any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
15 | * along with this program; if not, write to the Free Software | |
16 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. | |
17 | */ | |
18 | /** @file | |
19 | * @brief 32-bit pseudo-random number generator implementation. | |
20 | * @version $Id: random.c,v 1.8 2004/10/06 00:22:09 entrope Exp $ | |
21 | */ | |
22 | #include "config.h" | |
23 | ||
24 | #include "random.h" | |
25 | #include "client.h" | |
26 | #include "ircd_log.h" | |
27 | #include "ircd_md5.h" | |
28 | #include "ircd_reply.h" | |
29 | #include "send.h" | |
30 | ||
31 | #include <string.h> | |
32 | #include <sys/time.h> | |
33 | ||
34 | /** Pseudo-random number generator state. */ | |
35 | static struct MD5Context localkey; | |
36 | /** Next byte position in #localkey to insert at. */ | |
37 | static unsigned int localkey_pos; | |
38 | ||
39 | /** Add bytes to #localkey. | |
40 | * This should be fairly resistant to adding non-random bytes, but the | |
41 | * more random the bytes are, the harder it is for an attacker to | |
42 | * guess the internal state. | |
43 | * @param[in] buf Buffer of bytes to add. | |
44 | * @param[in] count Number of bytes to add. | |
45 | */ | |
46 | static void | |
47 | random_add_entropy(const char *buf, unsigned int count) | |
48 | { | |
49 | while (count--) { | |
50 | localkey.in[localkey_pos++] ^= *buf++; | |
51 | if (localkey_pos >= sizeof(localkey.in)) | |
52 | localkey_pos = 0; | |
53 | } | |
54 | } | |
55 | ||
56 | /** Seed the PRNG with a string. | |
57 | * @param[in] from Client setting the seed (may be NULL). | |
58 | * @param[in] fields Input arguments (fields[0] is used). | |
59 | * @param[in] count Number of input arguments. | |
60 | * @return Non-zero on success, zero on error. | |
61 | */ | |
62 | int | |
63 | random_seed_set(struct Client* from, const char* const* fields, int count) | |
64 | { | |
65 | if (count < 1) { | |
66 | if (from) /* send an error */ | |
67 | return need_more_params(from, "SET"); | |
68 | else { | |
69 | log_write(LS_CONFIG, L_ERROR, 0, "Not enough fields in F line"); | |
70 | return 0; | |
71 | } | |
72 | } | |
73 | ||
74 | random_add_entropy(fields[0], strlen(fields[0])); | |
75 | return 1; | |
76 | } | |
77 | ||
78 | /** Generate a pseudo-random number. | |
79 | * This uses the #localkey structure plus current time as input to | |
80 | * MD5, feeding most of the MD5 output back to #localkey and using one | |
81 | * output words as the pseudo-random output. | |
82 | * @return A 32-bit pseudo-random number. | |
83 | */ | |
84 | unsigned int ircrandom(void) | |
85 | { | |
86 | struct timeval tv; | |
87 | char usec[3]; | |
88 | ||
89 | /* Add some randomness to the pool. */ | |
90 | gettimeofday(&tv, 0); | |
91 | usec[0] = tv.tv_usec; | |
92 | usec[1] = tv.tv_usec >> 8; | |
93 | usec[2] = tv.tv_usec >> 16; | |
94 | random_add_entropy(usec, 3); | |
95 | ||
96 | /* Perform MD5 step. */ | |
97 | localkey.buf[0] = 0x67452301; | |
98 | localkey.buf[1] = 0xefcdab89; | |
99 | localkey.buf[2] = 0x98badcfe; | |
100 | localkey.buf[3] = 0x10325476; | |
101 | MD5Transform(localkey.buf, (uint32*)localkey.in); | |
102 | ||
103 | /* Feed back 12 bytes of hash value into randomness pool. */ | |
104 | random_add_entropy((char*)localkey.buf, 12); | |
105 | ||
106 | /* Return the final word of hash, which should not provide any | |
107 | * useful insight into current pool contents. */ | |
108 | return localkey.buf[3]; | |
109 | } |