1 /*
2 * Copyright (c) 2021 Google, Inc.
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files
6 * (the "Software"), to deal in the Software without restriction,
7 * including without limitation the rights to use, copy, modify, merge,
8 * publish, distribute, sublicense, and/or sell copies of the Software,
9 * and to permit persons to whom the Software is furnished to do so,
10 * subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
18 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
19 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
20 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
21 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
22 */
23
24 #include <assert.h>
25 #include <debug.h>
26 #include <platform/random.h>
27 #include <rand.h>
28
29 /*
30 * default implementations of these routines, if the platform code
31 * chooses not to implement.
32 */
33
platform_random_get_bytes(uint8_t * buf,size_t len)34 __WEAK void platform_random_get_bytes(uint8_t *buf, size_t len) {
35 /* Print a warning about using this, but only once per boot */
36 static bool printed_warning = false;
37 if (unlikely(!printed_warning)) {
38 dprintf(CRITICAL,
39 "FAKE RNG implementation MUST be replaced with the REAL one\n");
40 printed_warning = true;
41 }
42
43 DEBUG_ASSERT(buf);
44 while (len) {
45 /* lk's rand() returns 32 pseudo random bits */
46 uint32_t val = (uint32_t) rand();
47 size_t todo = len;
48 for (size_t i = 0; i < sizeof(val) && i < todo; i++, len--) {
49 *buf++ = val & 0xff;
50 val >>= 8;
51 }
52 }
53 }
54