Annotation of src/usr.bin/ssh/cipher-chachapoly-libcrypto.c, Revision 1.2
1.2 ! djm 1: /* $OpenBSD: cipher-chachapoly-libcrypto.c,v 1.1 2020/04/03 04:32:21 djm Exp $ */
1.1 djm 2: /*
3: * Copyright (c) 2013 Damien Miller <djm@mindrot.org>
4: *
5: * Permission to use, copy, modify, and distribute this software for any
6: * purpose with or without fee is hereby granted, provided that the above
7: * copyright notice and this permission notice appear in all copies.
8: *
9: * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10: * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11: * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12: * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13: * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14: * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15: * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16: */
17:
18: #include <sys/types.h>
19: #include <stdarg.h> /* needed for log.h */
20: #include <string.h>
21: #include <stdio.h> /* needed for misc.h */
22:
23: #include <openssl/evp.h>
24:
25: #include "log.h"
26: #include "sshbuf.h"
27: #include "ssherr.h"
28: #include "cipher-chachapoly.h"
29:
30: struct chachapoly_ctx {
31: EVP_CIPHER_CTX *main_evp, *header_evp;
32: };
33:
34: struct chachapoly_ctx *
35: chachapoly_new(const u_char *key, u_int keylen)
36: {
37: struct chachapoly_ctx *ctx;
38:
39: if (keylen != (32 + 32)) /* 2 x 256 bit keys */
40: return NULL;
41: if ((ctx = calloc(1, sizeof(*ctx))) == NULL)
42: return NULL;
43: if ((ctx->main_evp = EVP_CIPHER_CTX_new()) == NULL ||
44: (ctx->header_evp = EVP_CIPHER_CTX_new()) == NULL)
45: goto fail;
46: if (!EVP_CipherInit(ctx->main_evp, EVP_chacha20(), key, NULL, 1))
47: goto fail;
48: if (!EVP_CipherInit(ctx->header_evp, EVP_chacha20(), key + 32, NULL, 1))
49: goto fail;
50: if (EVP_CIPHER_CTX_iv_length(ctx->header_evp) != 16)
51: goto fail;
52: return ctx;
53: fail:
54: chachapoly_free(ctx);
55: return NULL;
56: }
57:
58: void
59: chachapoly_free(struct chachapoly_ctx *cpctx)
60: {
61: if (cpctx == NULL)
62: return;
63: EVP_CIPHER_CTX_free(cpctx->main_evp);
64: EVP_CIPHER_CTX_free(cpctx->header_evp);
65: freezero(cpctx, sizeof(*cpctx));
66: }
67:
68: /*
69: * chachapoly_crypt() operates as following:
70: * En/decrypt with header key 'aadlen' bytes from 'src', storing result
71: * to 'dest'. The ciphertext here is treated as additional authenticated
72: * data for MAC calculation.
73: * En/decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. Use
74: * POLY1305_TAGLEN bytes at offset 'len'+'aadlen' as the authentication
75: * tag. This tag is written on encryption and verified on decryption.
76: */
77: int
78: chachapoly_crypt(struct chachapoly_ctx *ctx, u_int seqnr, u_char *dest,
79: const u_char *src, u_int len, u_int aadlen, u_int authlen, int do_encrypt)
80: {
81: u_char seqbuf[16]; /* layout: u64 counter || u64 seqno */
82: int r = SSH_ERR_INTERNAL_ERROR;
83: u_char expected_tag[POLY1305_TAGLEN], poly_key[POLY1305_KEYLEN];
84:
85: /*
86: * Run ChaCha20 once to generate the Poly1305 key. The IV is the
87: * packet sequence number.
88: */
89: memset(seqbuf, 0, sizeof(seqbuf));
90: POKE_U64(seqbuf + 8, seqnr);
91: memset(poly_key, 0, sizeof(poly_key));
92: if (!EVP_CipherInit(ctx->main_evp, NULL, NULL, seqbuf, 1) ||
93: EVP_Cipher(ctx->main_evp, poly_key,
94: poly_key, sizeof(poly_key)) < 0) {
95: r = SSH_ERR_LIBCRYPTO_ERROR;
96: goto out;
97: }
98:
99: /* If decrypting, check tag before anything else */
100: if (!do_encrypt) {
101: const u_char *tag = src + aadlen + len;
102:
103: poly1305_auth(expected_tag, src, aadlen + len, poly_key);
104: if (timingsafe_bcmp(expected_tag, tag, POLY1305_TAGLEN) != 0) {
105: r = SSH_ERR_MAC_INVALID;
106: goto out;
107: }
108: }
109:
110: /* Crypt additional data */
111: if (aadlen) {
112: if (!EVP_CipherInit(ctx->header_evp, NULL, NULL, seqbuf, 1) ||
113: EVP_Cipher(ctx->header_evp, dest, src, aadlen) < 0) {
114: r = SSH_ERR_LIBCRYPTO_ERROR;
115: goto out;
116: }
117: }
118:
119: /* Set Chacha's block counter to 1 */
120: seqbuf[0] = 1;
121: if (!EVP_CipherInit(ctx->main_evp, NULL, NULL, seqbuf, 1) ||
122: EVP_Cipher(ctx->main_evp, dest + aadlen, src + aadlen, len) < 0) {
123: r = SSH_ERR_LIBCRYPTO_ERROR;
124: goto out;
125: }
126:
127: /* If encrypting, calculate and append tag */
128: if (do_encrypt) {
129: poly1305_auth(dest + aadlen + len, dest, aadlen + len,
130: poly_key);
131: }
132: r = 0;
133: out:
134: explicit_bzero(expected_tag, sizeof(expected_tag));
135: explicit_bzero(seqbuf, sizeof(seqbuf));
136: explicit_bzero(poly_key, sizeof(poly_key));
137: return r;
138: }
139:
140: /* Decrypt and extract the encrypted packet length */
141: int
142: chachapoly_get_length(struct chachapoly_ctx *ctx,
143: u_int *plenp, u_int seqnr, const u_char *cp, u_int len)
144: {
145: u_char buf[4], seqbuf[16];
146:
147: if (len < 4)
148: return SSH_ERR_MESSAGE_INCOMPLETE;
149: memset(seqbuf, 0, sizeof(seqbuf));
150: POKE_U64(seqbuf + 8, seqnr);
151: if (!EVP_CipherInit(ctx->header_evp, NULL, NULL, seqbuf, 0))
152: return SSH_ERR_LIBCRYPTO_ERROR;
153: if (EVP_Cipher(ctx->header_evp, buf, (u_char *)cp, sizeof(buf)) < 0)
154: return SSH_ERR_LIBCRYPTO_ERROR;
155: *plenp = PEEK_U32(buf);
156: return 0;
157: }
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