Mercurial > dropbear

annotate libtomcrypt/src/stream/rc4/rc4_stream.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
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10 #include "tomcrypt.h"
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11
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12 #ifdef LTC_RC4_STREAM
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13
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14 /**
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15 Initialize an RC4 context (only the key)
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16 @param st [out] The destination of the RC4 state
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17 @param key The secret key
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18 @param keylen The length of the secret key (8 - 256 bytes)
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19 @return CRYPT_OK if successful
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20 */
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21 int rc4_stream_setup(rc4_state *st, const unsigned char *key, unsigned long keylen)
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22 {
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23 unsigned char tmp, *s;
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24 int x, y;
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25 unsigned long j;
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26
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27 LTC_ARGCHK(st != NULL);
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28 LTC_ARGCHK(key != NULL);
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29 LTC_ARGCHK(keylen >= 5); /* 40-2048 bits */
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30
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31 s = st->buf;
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32 for (x = 0; x < 256; x++) {
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33 s[x] = x;
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34 }
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35
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36 for (j = x = y = 0; x < 256; x++) {
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37 y = (y + s[x] + key[j++]) & 255;
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38 if (j == keylen) {
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39 j = 0;
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40 }
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41 tmp = s[x]; s[x] = s[y]; s[y] = tmp;
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42 }
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43 st->x = 0;
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44 st->y = 0;
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45
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46 return CRYPT_OK;
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47 }
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48
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49 /**
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50 Encrypt (or decrypt) bytes of ciphertext (or plaintext) with RC4
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51 @param st The RC4 state
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52 @param in The plaintext (or ciphertext)
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53 @param inlen The length of the input (octets)
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54 @param out [out] The ciphertext (or plaintext), length inlen
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55 @return CRYPT_OK if successful
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56 */
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57 int rc4_stream_crypt(rc4_state *st, const unsigned char *in, unsigned long inlen, unsigned char *out)
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58 {
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59 unsigned char x, y, *s, tmp;
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60
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61 LTC_ARGCHK(st != NULL);
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62 LTC_ARGCHK(in != NULL);
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63 LTC_ARGCHK(out != NULL);
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64
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65 x = st->x;
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66 y = st->y;
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67 s = st->buf;
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68 while (inlen--) {
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69 x = (x + 1) & 255;
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70 y = (y + s[x]) & 255;
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71 tmp = s[x]; s[x] = s[y]; s[y] = tmp;
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72 tmp = (s[x] + s[y]) & 255;
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73 *out++ = *in++ ^ s[tmp];
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74 }
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75 st->x = x;
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76 st->y = y;
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77 return CRYPT_OK;
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78 }
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79
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80 /**
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81 Generate a stream of random bytes via RC4
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82 @param st The RC420 state
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83 @param out [out] The output buffer
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84 @param outlen The output length
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85 @return CRYPT_OK on success
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86 */
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87 int rc4_stream_keystream(rc4_state *st, unsigned char *out, unsigned long outlen)
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88 {
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89 if (outlen == 0) return CRYPT_OK; /* nothing to do */
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90 LTC_ARGCHK(out != NULL);
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91 XMEMSET(out, 0, outlen);
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92 return rc4_stream_crypt(st, out, outlen, out);
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93 }
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94
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95 /**
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96 Terminate and clear RC4 state
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97 @param st The RC4 state
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98 @return CRYPT_OK on success
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99 */
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100 int rc4_stream_done(rc4_state *st)
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101 {
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102 LTC_ARGCHK(st != NULL);
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103 XMEMSET(st, 0, sizeof(rc4_state));
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104 return CRYPT_OK;
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105 }
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106
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107 #endif
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108
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109 /* ref: $Format:%D$ */
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110 /* git commit: $Format:%H$ */
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111 /* commit time: $Format:%ai$ */