Mercurial > dropbear

annotate libtomcrypt/src/encauth/ccm/ccm_process.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
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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 #ifdef LTC_CCM_MODE
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12
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13 /**
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14 Process plaintext/ciphertext through CCM
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15 @param ccm The CCM state
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16 @param pt The plaintext
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17 @param ptlen The plaintext length (ciphertext length is the same)
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18 @param ct The ciphertext
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19 @param direction Encrypt or Decrypt mode (CCM_ENCRYPT or CCM_DECRYPT)
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20 @return CRYPT_OK on success
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21 */
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22 int ccm_process(ccm_state *ccm,
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23 unsigned char *pt, unsigned long ptlen,
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24 unsigned char *ct,
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25 int direction)
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26 {
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27 unsigned char z, b;
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28 unsigned long y;
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29 int err;
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30
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31 LTC_ARGCHK(ccm != NULL);
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32
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33 /* Check aad has been correctly added */
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34 if (ccm->aadlen != ccm->current_aadlen) {
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35 return CRYPT_ERROR;
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36 }
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37
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38 /* Check we do not process too much data */
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39 if (ccm->ptlen < ccm->current_ptlen + ptlen) {
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40 return CRYPT_ERROR;
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41 }
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42 ccm->current_ptlen += ptlen;
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43
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44 /* now handle the PT */
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45 if (ptlen > 0) {
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46 LTC_ARGCHK(pt != NULL);
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47 LTC_ARGCHK(ct != NULL);
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48
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49 for (y = 0; y < ptlen; y++) {
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50 /* increment the ctr? */
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51 if (ccm->CTRlen == 16) {
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52 for (z = 15; z > 15-ccm->L; z--) {
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53 ccm->ctr[z] = (ccm->ctr[z] + 1) & 255;
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54 if (ccm->ctr[z]) break;
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55 }
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56 if ((err = cipher_descriptor[ccm->cipher].ecb_encrypt(ccm->ctr, ccm->CTRPAD, &ccm->K)) != CRYPT_OK) {
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57 return err;
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58 }
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59 ccm->CTRlen = 0;
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60 }
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61
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62 /* if we encrypt we add the bytes to the MAC first */
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63 if (direction == CCM_ENCRYPT) {
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64 b = pt[y];
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65 ct[y] = b ^ ccm->CTRPAD[ccm->CTRlen++];
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66 } else {
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67 b = ct[y] ^ ccm->CTRPAD[ccm->CTRlen++];
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68 pt[y] = b;
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69 }
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70
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71 if (ccm->x == 16) {
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72 if ((err = cipher_descriptor[ccm->cipher].ecb_encrypt(ccm->PAD, ccm->PAD, &ccm->K)) != CRYPT_OK) {
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73 return err;
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74 }
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75 ccm->x = 0;
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76 }
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77 ccm->PAD[ccm->x++] ^= b;
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78 }
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79 }
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80
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81 return CRYPT_OK;
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82 }
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83
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84 #endif
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85
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86 /* ref: $Format:%D$ */
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87 /* git commit: $Format:%H$ */
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88 /* commit time: $Format:%ai$ */