Mercurial > dropbear

annotate libtomcrypt/src/pk/dh/dh_generate_key.c @ 1715:3974f087d9c0

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Disallow leading lines before the ident for server (#102) Per RFC4253 4.2 clients must be able to process other lines of data before the version string, server behavior is not defined neither with MUST/SHOULD nor with MAY. If server process up to 50 lines too - it may cause too long hanging session with invalid/evil client that consume host resources and potentially may lead to DDoS on poor embedded boxes. Let's require first line from client to be version string and fail early if it's not - matches both RFC and real OpenSSH behavior.
author Vladislav Grishenko <themiron@users.noreply.github.com>
date Mon, 15 Jun 2020 18:22:18 +0500
parents 6dba84798cd5
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
1471
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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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
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10 #include "tomcrypt.h"
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11
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12 #ifdef LTC_MDH
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13
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14 static int _dh_groupsize_to_keysize(int groupsize)
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15 {
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16 /* The strength estimates from https://tools.ietf.org/html/rfc3526#section-8
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17 * We use "Estimate 2" to get an appropriate private key (exponent) size.
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18 */
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19 if (groupsize <= 0) {
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20 return 0;
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21 }
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22 else if (groupsize <= 192) {
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23 return 30; /* 1536-bit => key size 240-bit */
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24 }
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25 else if (groupsize <= 256) {
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26 return 40; /* 2048-bit => key size 320-bit */
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27 }
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28 else if (groupsize <= 384) {
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29 return 52; /* 3072-bit => key size 416-bit */
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30 }
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31 else if (groupsize <= 512) {
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32 return 60; /* 4096-bit => key size 480-bit */
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33 }
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34 else if (groupsize <= 768) {
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35 return 67; /* 6144-bit => key size 536-bit */
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36 }
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37 else if (groupsize <= 1024) {
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38 return 77; /* 8192-bit => key size 616-bit */
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39 }
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40 else {
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41 return 0;
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42 }
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43 }
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44
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45 int dh_generate_key(prng_state *prng, int wprng, dh_key *key)
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46 {
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47 unsigned char *buf;
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48 unsigned long keysize;
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49 int err, max_iterations = LTC_PK_MAX_RETRIES;
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50
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51 LTC_ARGCHK(key != NULL);
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52 LTC_ARGCHK(ltc_mp.name != NULL);
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53
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54 /* good prng? */
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55 if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
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56 return err;
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57 }
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58
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59 keysize = _dh_groupsize_to_keysize(mp_unsigned_bin_size(key->prime));
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60 if (keysize == 0) {
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61 err = CRYPT_INVALID_KEYSIZE;
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62 goto freemp;
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63 }
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64
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65 /* allocate buffer */
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66 buf = XMALLOC(keysize);
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67 if (buf == NULL) {
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68 err = CRYPT_MEM;
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69 goto freemp;
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70 }
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71
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72 key->type = PK_PRIVATE;
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73 do {
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74 /* make up random buf */
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75 if (prng_descriptor[wprng].read(buf, keysize, prng) != keysize) {
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76 err = CRYPT_ERROR_READPRNG;
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77 goto freebuf;
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78 }
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79 /* load the x value - private key */
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80 if ((err = mp_read_unsigned_bin(key->x, buf, keysize)) != CRYPT_OK) {
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81 goto freebuf;
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82 }
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83 /* compute the y value - public key */
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84 if ((err = mp_exptmod(key->base, key->x, key->prime, key->y)) != CRYPT_OK) {
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85 goto freebuf;
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86 }
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87 err = dh_check_pubkey(key);
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88 } while (err != CRYPT_OK && max_iterations-- > 0);
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89
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90 freebuf:
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91 zeromem(buf, keysize);
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92 XFREE(buf);
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93 freemp:
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94 if (err != CRYPT_OK) dh_free(key);
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95 return err;
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96 }
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97
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98 #endif /* LTC_MDH */
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99
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100 /* ref: $Format:%D$ */
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101 /* git commit: $Format:%H$ */
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102 /* commit time: $Format:%ai$ */