Mercurial > dropbear

annotate libtomcrypt/src/encauth/ocb/ocb_decrypt.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
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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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10 /**
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11 @file ocb_decrypt.c
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6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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12 OCB implementation, decrypt data, 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_OCB_MODE
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18 /**
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19 Decrypt a block with OCB.
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20 @param ocb The OCB state
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21 @param ct The ciphertext (length of the block size of the block cipher)
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22 @param pt [out] The plaintext (length of ct)
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23 @return CRYPT_OK if successful
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24 */
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25 int ocb_decrypt(ocb_state *ocb, const unsigned char *ct, unsigned char *pt)
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26 {
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27 unsigned char Z[MAXBLOCKSIZE], tmp[MAXBLOCKSIZE];
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28 int err, x;
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30 LTC_ARGCHK(ocb != NULL);
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31 LTC_ARGCHK(pt != NULL);
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32 LTC_ARGCHK(ct != NULL);
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34 /* check if valid cipher */
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35 if ((err = cipher_is_valid(ocb->cipher)) != CRYPT_OK) {
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36 return err;
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37 }
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38 LTC_ARGCHK(cipher_descriptor[ocb->cipher].ecb_decrypt != NULL);
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6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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39
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40 /* check length */
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41 if (ocb->block_len != cipher_descriptor[ocb->cipher].block_length) {
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42 return CRYPT_INVALID_ARG;
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43 }
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45 /* Get Z[i] value */
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46 ocb_shift_xor(ocb, Z);
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48 /* xor ct in, encrypt, xor Z out */
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49 for (x = 0; x < ocb->block_len; x++) {
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50 tmp[x] = ct[x] ^ Z[x];
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51 }
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52 if ((err = cipher_descriptor[ocb->cipher].ecb_decrypt(tmp, pt, &ocb->key)) != CRYPT_OK) {
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53 return err;
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54 }
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55 for (x = 0; x < ocb->block_len; x++) {
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56 pt[x] ^= Z[x];
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57 }
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58
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59 /* compute checksum */
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60 for (x = 0; x < ocb->block_len; x++) {
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61 ocb->checksum[x] ^= pt[x];
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62 }
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65 #ifdef LTC_CLEAN_STACK
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66 zeromem(Z, sizeof(Z));
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67 zeromem(tmp, sizeof(tmp));
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68 #endif
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69 return CRYPT_OK;
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70 }
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72 #endif
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74
1471
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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75 /* ref: $Format:%D$ */
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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76 /* git commit: $Format:%H$ */
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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77 /* commit time: $Format:%ai$ */