Line data Source code
1 : /*
2 : * prng.c
3 : *
4 : * pseudorandom source
5 : *
6 : * David A. McGrew
7 : * Cisco Systems, Inc.
8 : */
9 : /*
10 : *
11 : * Copyright(c) 2001-2006 Cisco Systems, Inc.
12 : * All rights reserved.
13 : *
14 : * Redistribution and use in source and binary forms, with or without
15 : * modification, are permitted provided that the following conditions
16 : * are met:
17 : *
18 : * Redistributions of source code must retain the above copyright
19 : * notice, this list of conditions and the following disclaimer.
20 : *
21 : * Redistributions in binary form must reproduce the above
22 : * copyright notice, this list of conditions and the following
23 : * disclaimer in the documentation and/or other materials provided
24 : * with the distribution.
25 : *
26 : * Neither the name of the Cisco Systems, Inc. nor the names of its
27 : * contributors may be used to endorse or promote products derived
28 : * from this software without specific prior written permission.
29 : *
30 : * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
31 : * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
32 : * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
33 : * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
34 : * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
35 : * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
36 : * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
37 : * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
38 : * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39 : * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
40 : * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
41 : * OF THE POSSIBILITY OF SUCH DAMAGE.
42 : *
43 : */
44 :
45 :
46 : #include "prng.h"
47 :
48 : /* single, global prng structure */
49 :
50 : x917_prng_t x917_prng;
51 :
52 : err_status_t
53 0 : x917_prng_init(rand_source_func_t random_source) {
54 : uint8_t tmp_key[16];
55 : err_status_t status;
56 :
57 : /* initialize output count to zero */
58 0 : x917_prng.octet_count = 0;
59 :
60 : /* set random source */
61 0 : x917_prng.rand = random_source;
62 :
63 : /* initialize secret key from random source */
64 0 : status = random_source(tmp_key, 16);
65 0 : if (status)
66 0 : return status;
67 :
68 : /* expand aes key */
69 0 : aes_expand_encryption_key(tmp_key, 16, &x917_prng.key);
70 :
71 : /* initialize prng state from random source */
72 0 : status = x917_prng.rand((uint8_t *)&x917_prng.state, 16);
73 0 : if (status)
74 0 : return status;
75 :
76 0 : return err_status_ok;
77 : }
78 :
79 : err_status_t
80 0 : x917_prng_get_octet_string(uint8_t *dest, uint32_t len) {
81 : uint32_t t;
82 : v128_t buffer;
83 : uint32_t i, tail_len;
84 : err_status_t status;
85 :
86 : /*
87 : * if we need to re-initialize the prng, do so now
88 : *
89 : * avoid overflows by subtracting instead of adding
90 : */
91 0 : if (x917_prng.octet_count > MAX_PRNG_OUT_LEN - len) {
92 0 : status = x917_prng_init(x917_prng.rand);
93 0 : if (status)
94 0 : return status;
95 : }
96 0 : x917_prng.octet_count += len;
97 :
98 : /* find out the time */
99 0 : t = (uint32_t)time(NULL);
100 :
101 : /* loop until we have output enough data */
102 0 : for (i=0; i < len/16; i++) {
103 :
104 : /* exor time into state */
105 0 : x917_prng.state.v32[0] ^= t;
106 :
107 : /* copy state into buffer */
108 0 : v128_copy(&buffer, &x917_prng.state);
109 :
110 : /* apply aes to buffer */
111 0 : aes_encrypt(&buffer, &x917_prng.key);
112 :
113 : /* write data to output */
114 0 : *dest++ = buffer.v8[0];
115 0 : *dest++ = buffer.v8[1];
116 0 : *dest++ = buffer.v8[2];
117 0 : *dest++ = buffer.v8[3];
118 0 : *dest++ = buffer.v8[4];
119 0 : *dest++ = buffer.v8[5];
120 0 : *dest++ = buffer.v8[6];
121 0 : *dest++ = buffer.v8[7];
122 0 : *dest++ = buffer.v8[8];
123 0 : *dest++ = buffer.v8[9];
124 0 : *dest++ = buffer.v8[10];
125 0 : *dest++ = buffer.v8[11];
126 0 : *dest++ = buffer.v8[12];
127 0 : *dest++ = buffer.v8[13];
128 0 : *dest++ = buffer.v8[14];
129 0 : *dest++ = buffer.v8[15];
130 :
131 : /* exor time into buffer */
132 0 : buffer.v32[0] ^= t;
133 :
134 : /* encrypt buffer */
135 0 : aes_encrypt(&buffer, &x917_prng.key);
136 :
137 : /* copy buffer into state */
138 0 : v128_copy(&x917_prng.state, &buffer);
139 :
140 : }
141 :
142 : /* if we need to output any more octets, we'll do so now */
143 0 : tail_len = len % 16;
144 0 : if (tail_len) {
145 :
146 : /* exor time into state */
147 0 : x917_prng.state.v32[0] ^= t;
148 :
149 : /* copy value into buffer */
150 0 : v128_copy(&buffer, &x917_prng.state);
151 :
152 : /* apply aes to buffer */
153 0 : aes_encrypt(&buffer, &x917_prng.key);
154 :
155 : /* write data to output */
156 0 : for (i=0; i < tail_len; i++) {
157 0 : *dest++ = buffer.v8[i];
158 : }
159 :
160 : /* now update the state one more time */
161 :
162 : /* exor time into buffer */
163 0 : buffer.v32[0] ^= t;
164 :
165 : /* encrypt buffer */
166 0 : aes_encrypt(&buffer, &x917_prng.key);
167 :
168 : /* copy buffer into state */
169 0 : v128_copy(&x917_prng.state, &buffer);
170 :
171 : }
172 :
173 0 : return err_status_ok;
174 : }
175 :
176 : err_status_t
177 0 : x917_prng_deinit(void) {
178 :
179 0 : return err_status_ok;
180 : }
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