Mercurial > dropbear

annotate libtomcrypt/src/pk/dh/dh_import.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
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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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 /**
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15 Import a DH key from a binary packet
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16 @param in The packet to read
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17 @param inlen The length of the input packet
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18 @param key [out] Where to import the key to
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19 @return CRYPT_OK if successful, on error all allocated memory is freed automatically
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20 */
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21 int dh_import(const unsigned char *in, unsigned long inlen, dh_key *key)
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22 {
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23 unsigned char flags[1];
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24 int err;
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25 unsigned long version;
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26
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27 LTC_ARGCHK(in != NULL);
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28 LTC_ARGCHK(key != NULL);
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29
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30 /* init */
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31 if ((err = mp_init_multi(&key->x, &key->y, &key->base, &key->prime, NULL)) != CRYPT_OK) {
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32 return err;
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33 }
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34
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35 /* find out what type of key it is */
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36 err = der_decode_sequence_multi(in, inlen,
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37 LTC_ASN1_SHORT_INTEGER, 1UL, &version,
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38 LTC_ASN1_BIT_STRING, 1UL, &flags,
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39 LTC_ASN1_EOL, 0UL, NULL);
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40 if (err != CRYPT_OK && err != CRYPT_INPUT_TOO_LONG) {
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41 goto error;
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42 }
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43
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44 if (version == 0) {
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45 if (flags[0] == 1) {
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46 key->type = PK_PRIVATE;
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47 if ((err = der_decode_sequence_multi(in, inlen,
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48 LTC_ASN1_SHORT_INTEGER, 1UL, &version,
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49 LTC_ASN1_BIT_STRING, 1UL, flags,
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50 LTC_ASN1_INTEGER, 1UL, key->prime,
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51 LTC_ASN1_INTEGER, 1UL, key->base,
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52 LTC_ASN1_INTEGER, 1UL, key->x,
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53 LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) {
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54 goto error;
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55 }
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56 /* compute public key: y = (base ^ x) mod prime */
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57 if ((err = mp_exptmod(key->base, key->x, key->prime, key->y)) != CRYPT_OK) {
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58 goto error;
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59 }
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60 }
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61 else if (flags[0] == 0) {
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62 key->type = PK_PUBLIC;
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63 if ((err = der_decode_sequence_multi(in, inlen,
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64 LTC_ASN1_SHORT_INTEGER, 1UL, &version,
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65 LTC_ASN1_BIT_STRING, 1UL, flags,
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66 LTC_ASN1_INTEGER, 1UL, key->prime,
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67 LTC_ASN1_INTEGER, 1UL, key->base,
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68 LTC_ASN1_INTEGER, 1UL, key->y,
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69 LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) {
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70 goto error;
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71 }
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72 }
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73 else {
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74 err = CRYPT_INVALID_PACKET;
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75 goto error;
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76 }
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77 }
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78 else {
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79 err = CRYPT_INVALID_PACKET;
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80 goto error;
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81 }
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82
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83 /* check public key */
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84 if ((err = dh_check_pubkey(key)) != CRYPT_OK) {
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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85 goto error;
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86 }
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87
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88 return CRYPT_OK;
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89
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90 error:
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91 dh_free(key);
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92 return err;
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93 }
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94
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95 #endif /* LTC_MDH */
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96
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97 /* ref: $Format:%D$ */
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98 /* git commit: $Format:%H$ */
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99 /* commit time: $Format:%ai$ */