1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
/*
* Copyright (c) 2013 Damien Miller <djm@mindrot.org>
*
* Adapted by Will Cosgrove <will@panic.com> for libssh2
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
/* $OpenBSD: cipher-chachapoly.c,v 1.8 2016/08/03 05:41:57 djm Exp $ */
#include "libssh2_priv.h"
#include "misc.h"
#include "cipher-chachapoly.h"
int
chachapoly_timingsafe_bcmp(const void *b1, const void *b2, size_t n);
int
chachapoly_init(struct chachapoly_ctx *ctx, const u_char *key, u_int keylen)
{
if(keylen != (32 + 32)) /* 2 x 256 bit keys */
return LIBSSH2_ERROR_INVAL;
chacha_keysetup(&ctx->main_ctx, key, 256);
chacha_keysetup(&ctx->header_ctx, key + 32, 256);
return 0;
}
/*
* chachapoly_crypt() operates as following:
* En/decrypt with header key 'aadlen' bytes from 'src', storing result
* to 'dest'. The ciphertext here is treated as additional authenticated
* data for MAC calculation.
* En/decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. Use
* POLY1305_TAGLEN bytes at offset 'len'+'aadlen' as the authentication
* tag. This tag is written on encryption and verified on decryption.
*/
int
chachapoly_crypt(struct chachapoly_ctx *ctx, u_int seqnr, u_char *dest,
const u_char *src, u_int len, u_int aadlen, int do_encrypt)
{
u_char seqbuf[8];
const u_char one[8] = { 1, 0, 0, 0, 0, 0, 0, 0 }; /* NB little-endian */
u_char expected_tag[POLY1305_TAGLEN], poly_key[POLY1305_KEYLEN];
int r = LIBSSH2_ERROR_INVAL;
unsigned char *ptr = NULL;
/*
* Run ChaCha20 once to generate the Poly1305 key. The IV is the
* packet sequence number.
*/
memset(poly_key, 0, sizeof(poly_key));
ptr = &seqbuf[0];
_libssh2_store_u64(&ptr, seqnr);
chacha_ivsetup(&ctx->main_ctx, seqbuf, NULL);
chacha_encrypt_bytes(&ctx->main_ctx,
poly_key, poly_key, sizeof(poly_key));
/* If decrypting, check tag before anything else */
if(!do_encrypt) {
const u_char *tag = src + aadlen + len;
poly1305_auth(expected_tag, src, aadlen + len, poly_key);
if(chachapoly_timingsafe_bcmp(expected_tag, tag, POLY1305_TAGLEN)
!= 0) {
r = LIBSSH2_ERROR_DECRYPT;
goto out;
}
}
/* Crypt additional data */
if(aadlen) {
chacha_ivsetup(&ctx->header_ctx, seqbuf, NULL);
chacha_encrypt_bytes(&ctx->header_ctx, src, dest, aadlen);
}
/* Set Chacha's block counter to 1 */
chacha_ivsetup(&ctx->main_ctx, seqbuf, one);
chacha_encrypt_bytes(&ctx->main_ctx, src + aadlen,
dest + aadlen, len);
/* If encrypting, calculate and append tag */
if(do_encrypt) {
poly1305_auth(dest + aadlen + len, dest, aadlen + len,
poly_key);
}
r = 0;
out:
memset(expected_tag, 0, sizeof(expected_tag));
memset(seqbuf, 0, sizeof(seqbuf));
memset(poly_key, 0, sizeof(poly_key));
return r;
}
/* Decrypt and extract the encrypted packet length */
int
chachapoly_get_length(struct chachapoly_ctx *ctx, unsigned int *plenp,
unsigned int seqnr, const unsigned char *cp,
unsigned int len)
{
u_char buf[4], seqbuf[8];
unsigned char *ptr = NULL;
if(len < 4)
return -1;
ptr = &seqbuf[0];
_libssh2_store_u64(&ptr, seqnr);
chacha_ivsetup(&ctx->header_ctx, seqbuf, NULL);
chacha_encrypt_bytes(&ctx->header_ctx, cp, buf, 4);
*plenp = _libssh2_ntohu32(buf);
return 0;
}
int
chachapoly_timingsafe_bcmp(const void *b1, const void *b2, size_t n)
{
const unsigned char *p1 = b1, *p2 = b2;
int ret = 0;
for(; n > 0; n--)
ret |= *p1++ ^ *p2++;
return (ret != 0);
}
|
