5
Last change
on this file since 3d374d9 was
3d374d9,
checked in by Sebastian Huber <sebastian.huber@…>, on 11/17/17 at 08:43:17
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bsps: Use a state in default getentropy()
Use the boot time to initialize the state. Use the state, the current
CPU counter and a very simple pseudo random number generator for
getentropy(). At least, this enables to pass the test "GETENTROPY 1" on
ERC32.
Update #3239.
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-
Property mode set to
100644
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File size:
1.4 KB
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1 | /* |
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2 | * Copyright (c) 2017 embedded brains GmbH. All rights reserved. |
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3 | * |
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4 | * embedded brains GmbH |
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5 | * Dornierstr. 4 |
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6 | * 82178 Puchheim |
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7 | * Germany |
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8 | * <rtems@embedded-brains.de> |
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9 | * |
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10 | * The license and distribution terms for this file may be |
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11 | * found in the file LICENSE in this distribution or at |
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12 | * http://www.rtems.org/license/LICENSE. |
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13 | */ |
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14 | |
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15 | /* |
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16 | * ATTENTION: THIS IS A VERY LIMITED ENTROPY SOURCE. |
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17 | * |
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18 | * This implementation uses a time-based value for it's entropy. The only thing |
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19 | * that makes it random are interrupts from external sources. Don't use it if |
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20 | * you need for example a strong crypto. |
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21 | */ |
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22 | |
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23 | #include <sys/param.h> |
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24 | #include <unistd.h> |
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25 | #include <string.h> |
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26 | #include <rtems/bsd.h> |
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27 | #include <rtems/counter.h> |
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28 | #include <rtems/sysinit.h> |
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29 | |
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30 | static uint32_t state; |
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31 | |
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32 | int getentropy(void *ptr, size_t n) |
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33 | { |
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34 | uint8_t *dest = ptr; |
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35 | |
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36 | state ^= rtems_counter_read(); |
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37 | state *= 25169206; |
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38 | state += 1679610226; |
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39 | |
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40 | while (n > 0) { |
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41 | size_t m; |
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42 | |
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43 | m = MIN(n, sizeof(state)); |
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44 | memcpy(dest, &state, m); |
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45 | n -= m; |
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46 | dest += m; |
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47 | state *= 85236167; |
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48 | state += 30557471; |
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49 | } |
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50 | |
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51 | return 0; |
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52 | } |
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53 | |
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54 | static void getentropy_init(void) |
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55 | { |
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56 | struct bintime bt; |
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57 | |
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58 | rtems_bsd_bintime(&bt); |
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59 | state = (uint32_t) bt.frac; |
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60 | state ^= (uint32_t) (bt.frac >> 32); |
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61 | state ^= (uint32_t) bt.sec; |
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62 | state ^= (uint32_t) (bt.sec >> 32); |
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63 | } |
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64 | |
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65 | RTEMS_SYSINIT_ITEM( |
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66 | getentropy_init, |
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67 | RTEMS_SYSINIT_DEVICE_DRIVERS, |
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68 | RTEMS_SYSINIT_ORDER_LAST |
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69 | ); |
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