Mercurial > dropbear

annotate src/pk/dsa/dsa_verify_key.c @ 383:2c89a3a04104 libtomcrypt-dropbear

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Fix up some slight changes. Hack out the RSA code in tomcrypt_math.h fairly crudely, as LTC's rsa_key collide's with Dropbear's rsa_key
author Matt Johnston <matt@ucc.asn.au>
date Thu, 11 Jan 2007 03:04:55 +0000
parents d5faf4814ddb
children
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280
59400faa4b44 Re-import libtomcrypt 1.05 for cleaner propagating.
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
59400faa4b44 Re-import libtomcrypt 1.05 for cleaner propagating.
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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 * Tom St Denis, [email protected], http://libtomcrypt.com
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10 */
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11 #include "tomcrypt.h"
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12
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13 /**
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14 @file dsa_verify_key.c
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15 DSA implementation, verify a key, Tom St Denis
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16 */
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17
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18 #ifdef MDSA
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19
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20 /**
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21 Verify a DSA key for validity
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22 @param key The key to verify
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23 @param stat [out] Result of test, 1==valid, 0==invalid
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24 @return CRYPT_OK if successful
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25 */
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26 int dsa_verify_key(dsa_key *key, int *stat)
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27 {
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28 void *tmp, *tmp2;
280
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29 int res, err;
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30
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31 LTC_ARGCHK(key != NULL);
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32 LTC_ARGCHK(stat != NULL);
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33
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34 /* default to an invalid key */
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35 *stat = 0;
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36
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37 /* first make sure key->q and key->p are prime */
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38 if ((err = mp_prime_is_prime(key->q, 8, &res)) != CRYPT_OK) {
280
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39 return err;
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40 }
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41 if (res == 0) {
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42 return CRYPT_OK;
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43 }
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44
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45 if ((err = mp_prime_is_prime(key->p, 8, &res)) != CRYPT_OK) {
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46 return err;
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47 }
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48 if (res == 0) {
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49 return CRYPT_OK;
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50 }
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51
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52 /* now make sure that g is not -1, 0 or 1 and <p */
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53 if (mp_cmp_d(key->g, 0) == LTC_MP_EQ || mp_cmp_d(key->g, 1) == LTC_MP_EQ) {
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54 return CRYPT_OK;
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55 }
380
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56 if ((err = mp_init_multi(&tmp, &tmp2, NULL)) != CRYPT_OK) { return err; }
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57 if ((err = mp_sub_d(key->p, 1, tmp)) != CRYPT_OK) { goto error; }
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58 if (mp_cmp(tmp, key->g) == LTC_MP_EQ || mp_cmp(key->g, key->p) != LTC_MP_LT) {
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59 err = CRYPT_OK;
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60 goto error;
280
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61 }
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62
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63 /* 1 < y < p-1 */
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64 if (!(mp_cmp_d(key->y, 1) == LTC_MP_GT && mp_cmp(key->y, tmp) == LTC_MP_LT)) {
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65 err = CRYPT_OK;
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66 goto error;
280
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67 }
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68
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69 /* now we have to make sure that g^q = 1, and that p-1/q gives 0 remainder */
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70 if ((err = mp_div(tmp, key->q, tmp, tmp2)) != CRYPT_OK) { goto error; }
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71 if (mp_iszero(tmp2) != LTC_MP_YES) {
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72 err = CRYPT_OK;
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73 goto error;
280
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74 }
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75
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76 if ((err = mp_exptmod(key->g, key->q, key->p, tmp)) != CRYPT_OK) { goto error; }
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77 if (mp_cmp_d(tmp, 1) != LTC_MP_EQ) {
280
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78 err = CRYPT_OK;
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79 goto error;
280
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80 }
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81
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82 /* now we have to make sure that y^q = 1, this makes sure y \in g^x mod p */
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83 if ((err = mp_exptmod(key->y, key->q, key->p, tmp)) != CRYPT_OK) { goto error; }
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84 if (mp_cmp_d(tmp, 1) != LTC_MP_EQ) {
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85 err = CRYPT_OK;
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86 goto error;
280
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87 }
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88
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89 /* at this point we are out of tests ;-( */
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90 err = CRYPT_OK;
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91 *stat = 1;
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92 error:
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93 mp_clear_multi(tmp, tmp2, NULL);
280
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94 return err;
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95 }
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96 #endif
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97
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98 /* $Source: /cvs/libtom/libtomcrypt/src/pk/dsa/dsa_verify_key.c,v $ */
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99 /* $Revision: 1.6 $ */
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100 /* $Date: 2006/12/04 03:18:43 $ */