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annotate libtomcrypt/src/math/rand_bn.c @ 1861:2b3a8026a6ce

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Add re-exec for server This allows ASLR to re-randomize the address space for every connection, preventing some vulnerabilities from being exploitable by repeated probing. Overhead (memory and time) is yet to be confirmed. At present this is only enabled on Linux. Other BSD platforms with fexecve() would probably also work though have not been tested.
author Matt Johnston <matt@ucc.asn.au>
date Sun, 30 Jan 2022 10:14:56 +0800
parents e9dba7abd939
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1471
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
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2 *
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3 * LibTomCrypt is a library that provides various cryptographic
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4 * algorithms in a highly modular and flexible manner.
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5 *
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6 * The library is free for all purposes without any express
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7 * guarantee it works.
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8 */
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9 #include "tomcrypt.h"
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10
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11 #if defined(LTC_MDSA) || defined(LTC_MECC)
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12 /**
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13 Generate a random number N with given bitlength (note: MSB can be 0)
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14 */
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15
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16 int rand_bn_bits(void *N, int bits, prng_state *prng, int wprng)
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17 {
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18 int res, bytes;
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19 unsigned char *buf, mask;
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20
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21 LTC_ARGCHK(N != NULL);
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22 LTC_ARGCHK(bits > 1);
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23
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24 /* check PRNG */
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25 if ((res = prng_is_valid(wprng)) != CRYPT_OK) return res;
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26
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27 bytes = (bits+7) >> 3;
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28 mask = 0xff << (8 - bits % 8);
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29
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30 /* allocate buffer */
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31 if ((buf = XCALLOC(1, bytes)) == NULL) return CRYPT_MEM;
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32
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33 /* generate random bytes */
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34 if (prng_descriptor[wprng].read(buf, bytes, prng) != (unsigned long)bytes) {
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35 res = CRYPT_ERROR_READPRNG;
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36 goto cleanup;
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37 }
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38 /* mask bits */
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39 buf[0] &= ~mask;
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40 /* load value */
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41 if ((res = mp_read_unsigned_bin(N, buf, bytes)) != CRYPT_OK) goto cleanup;
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42
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43 res = CRYPT_OK;
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44
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45 cleanup:
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46 #ifdef LTC_CLEAN_STACK
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47 zeromem(buf, bytes);
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48 #endif
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49 XFREE(buf);
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50 return res;
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51 }
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52
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53 /**
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54 Generate a random number N in a range: 1 <= N < limit
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55 */
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56 int rand_bn_upto(void *N, void *limit, prng_state *prng, int wprng)
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57 {
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58 int res, bits;
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59
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60 LTC_ARGCHK(N != NULL);
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61 LTC_ARGCHK(limit != NULL);
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62
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63 bits = mp_count_bits(limit);
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64 do {
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65 res = rand_bn_bits(N, bits, prng, wprng);
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66 if (res != CRYPT_OK) return res;
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67 } while (mp_cmp_d(N, 0) != LTC_MP_GT || mp_cmp(N, limit) != LTC_MP_LT);
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68
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69 return CRYPT_OK;
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70 }
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71 #endif
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72
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73 /* ref: $Format:%D$ */
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74 /* git commit: $Format:%H$ */
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75 /* commit time: $Format:%ai$ */