Mercurial > dropbear

annotate libtomcrypt/src/encauth/ocb3/ocb3_done.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 /**
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11 @file ocb3_done.c
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12 OCB implementation, INTERNAL ONLY helper, by Tom St Denis
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13 */
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14 #include "tomcrypt.h"
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15
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16 #ifdef LTC_OCB3_MODE
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17
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18 /**
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19 Finish OCB processing and compute the tag
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20 @param ocb The OCB state
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21 @param tag [out] The destination for the authentication tag
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22 @param taglen [in/out] The max size and resulting size of the authentication tag
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23 @return CRYPT_OK if successful
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24 */
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25 int ocb3_done(ocb3_state *ocb, unsigned char *tag, unsigned long *taglen)
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26 {
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27 unsigned char tmp[MAXBLOCKSIZE];
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28 int err, x;
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29
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30 LTC_ARGCHK(ocb != NULL);
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31 LTC_ARGCHK(tag != NULL);
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32 LTC_ARGCHK(taglen != NULL);
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33 if ((err = cipher_is_valid(ocb->cipher)) != CRYPT_OK) {
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34 goto LBL_ERR;
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35 }
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36
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37 /* check taglen */
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38 if ((int)*taglen < ocb->tag_len) {
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39 *taglen = (unsigned long)ocb->tag_len;
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40 return CRYPT_BUFFER_OVERFLOW;
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41 }
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42
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43 /* finalize AAD processing */
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44
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45 if (ocb->adata_buffer_bytes>0) {
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46 /* Offset_* = Offset_m xor L_* */
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47 ocb3_int_xor_blocks(ocb->aOffset_current, ocb->aOffset_current, ocb->L_star, ocb->block_len);
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48
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49 /* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
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50 ocb3_int_xor_blocks(tmp, ocb->adata_buffer, ocb->aOffset_current, ocb->adata_buffer_bytes);
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51 for(x=ocb->adata_buffer_bytes; x<ocb->block_len; x++) {
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52 if (x == ocb->adata_buffer_bytes) {
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53 tmp[x] = 0x80 ^ ocb->aOffset_current[x];
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54 }
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55 else {
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56 tmp[x] = 0x00 ^ ocb->aOffset_current[x];
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57 }
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58 }
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59
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60 /* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
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61 if ((err = cipher_descriptor[ocb->cipher].ecb_encrypt(tmp, tmp, &ocb->key)) != CRYPT_OK) {
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62 goto LBL_ERR;
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63 }
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64 ocb3_int_xor_blocks(ocb->aSum_current, ocb->aSum_current, tmp, ocb->block_len);
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65 }
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66
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67 /* finalize TAG computing */
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68
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69 /* at this point ocb->aSum_current = HASH(K, A) */
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70 /* tag = tag ^ HASH(K, A) */
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71 ocb3_int_xor_blocks(tmp, ocb->tag_part, ocb->aSum_current, ocb->block_len);
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72
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73 /* copy tag bytes */
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74 for(x = 0; x < ocb->tag_len; x++) tag[x] = tmp[x];
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75 *taglen = (unsigned long)ocb->tag_len;
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76
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77 err = CRYPT_OK;
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78
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79 LBL_ERR:
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80 #ifdef LTC_CLEAN_STACK
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81 zeromem(tmp, MAXBLOCKSIZE);
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82 zeromem(ocb, sizeof(*ocb));
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83 #endif
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84
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85 return err;
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86 }
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87
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88 #endif
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89
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90 /* ref: $Format:%D$ */
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91 /* git commit: $Format:%H$ */
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92 /* commit time: $Format:%ai$ */