annotate libtomcrypt/src/encauth/gcm/gcm_done.c @ 1715:3974f087d9c0

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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9
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10 /**
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11 @file gcm_done.c
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12 GCM implementation, Terminate the stream, 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_GCM_MODE
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17
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18 /**
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19 Terminate a GCM stream
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20 @param gcm The GCM state
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21 @param tag [out] The destination for the MAC tag
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22 @param taglen [in/out] The length of the MAC tag
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23 @return CRYPT_OK on success
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24 */
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25 int gcm_done(gcm_state *gcm,
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26 unsigned char *tag, unsigned long *taglen)
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27 {
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28 unsigned long x;
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29 int err;
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30
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31 LTC_ARGCHK(gcm != NULL);
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32 LTC_ARGCHK(tag != NULL);
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33 LTC_ARGCHK(taglen != NULL);
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34
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35 if (gcm->buflen > 16 || gcm->buflen < 0) {
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36 return CRYPT_INVALID_ARG;
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37 }
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38
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39 if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) {
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40 return err;
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41 }
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42
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43 if (gcm->mode == LTC_GCM_MODE_IV) {
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44 /* let's process the IV */
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45 if ((err = gcm_add_aad(gcm, NULL, 0)) != CRYPT_OK) return err;
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46 }
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47
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48 if (gcm->mode == LTC_GCM_MODE_AAD) {
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49 /* let's process the AAD */
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50 if ((err = gcm_process(gcm, NULL, 0, NULL, 0)) != CRYPT_OK) return err;
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51 }
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52
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53 if (gcm->mode != LTC_GCM_MODE_TEXT) {
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54 return CRYPT_INVALID_ARG;
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55 }
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56
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57 /* handle remaining ciphertext */
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58 if (gcm->buflen) {
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59 gcm->pttotlen += gcm->buflen * CONST64(8);
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60 gcm_mult_h(gcm, gcm->X);
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61 }
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62
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63 /* length */
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64 STORE64H(gcm->totlen, gcm->buf);
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65 STORE64H(gcm->pttotlen, gcm->buf+8);
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66 for (x = 0; x < 16; x++) {
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67 gcm->X[x] ^= gcm->buf[x];
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68 }
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69 gcm_mult_h(gcm, gcm->X);
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70
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71 /* encrypt original counter */
382
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72 if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y_0, gcm->buf, &gcm->K)) != CRYPT_OK) {
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73 return err;
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74 }
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75 for (x = 0; x < 16 && x < *taglen; x++) {
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76 tag[x] = gcm->buf[x] ^ gcm->X[x];
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77 }
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78 *taglen = x;
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79
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80 cipher_descriptor[gcm->cipher].done(&gcm->K);
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81
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82 return CRYPT_OK;
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83 }
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84
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85 #endif
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86
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87
1471
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88 /* ref: $Format:%D$ */
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89 /* git commit: $Format:%H$ */
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90 /* commit time: $Format:%ai$ */