Damien Miller | 0fde8ac | 2013-11-21 14:12:23 +1100 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2013 Damien Miller <djm@mindrot.org> |
| 3 | * |
| 4 | * Permission to use, copy, modify, and distribute this software for any |
| 5 | * purpose with or without fee is hereby granted, provided that the above |
| 6 | * copyright notice and this permission notice appear in all copies. |
| 7 | * |
| 8 | * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
| 9 | * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
| 10 | * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR |
| 11 | * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
| 12 | * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN |
| 13 | * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF |
| 14 | * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
| 15 | */ |
| 16 | |
Damien Miller | d58a596 | 2013-12-18 17:50:13 +1100 | [diff] [blame] | 17 | /* $OpenBSD: cipher-chachapoly.c,v 1.3 2013/12/15 21:42:35 djm Exp $ */ |
Damien Miller | 0fde8ac | 2013-11-21 14:12:23 +1100 | [diff] [blame] | 18 | |
| 19 | #include "includes.h" |
| 20 | |
| 21 | #include <sys/types.h> |
| 22 | #include <stdarg.h> /* needed for log.h */ |
| 23 | #include <string.h> |
| 24 | #include <stdio.h> /* needed for misc.h */ |
| 25 | |
| 26 | #include "log.h" |
| 27 | #include "misc.h" |
| 28 | #include "cipher-chachapoly.h" |
| 29 | |
| 30 | void chachapoly_init(struct chachapoly_ctx *ctx, |
| 31 | const u_char *key, u_int keylen) |
| 32 | { |
| 33 | if (keylen != (32 + 32)) /* 2 x 256 bit keys */ |
| 34 | fatal("%s: invalid keylen %u", __func__, keylen); |
| 35 | chacha_keysetup(&ctx->main_ctx, key, 256); |
| 36 | chacha_keysetup(&ctx->header_ctx, key + 32, 256); |
| 37 | } |
| 38 | |
| 39 | /* |
| 40 | * chachapoly_crypt() operates as following: |
Damien Miller | d58a596 | 2013-12-18 17:50:13 +1100 | [diff] [blame] | 41 | * En/decrypt with header key 'aadlen' bytes from 'src', storing result |
| 42 | * to 'dest'. The ciphertext here is treated as additional authenticated |
| 43 | * data for MAC calculation. |
| 44 | * En/decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. Use |
| 45 | * POLY1305_TAGLEN bytes at offset 'len'+'aadlen' as the authentication |
| 46 | * tag. This tag is written on encryption and verified on decryption. |
Damien Miller | 0fde8ac | 2013-11-21 14:12:23 +1100 | [diff] [blame] | 47 | */ |
| 48 | int |
| 49 | chachapoly_crypt(struct chachapoly_ctx *ctx, u_int seqnr, u_char *dest, |
| 50 | const u_char *src, u_int len, u_int aadlen, u_int authlen, int do_encrypt) |
| 51 | { |
| 52 | u_char seqbuf[8]; |
Damien Miller | d58a596 | 2013-12-18 17:50:13 +1100 | [diff] [blame] | 53 | const u_char one[8] = { 1, 0, 0, 0, 0, 0, 0, 0 }; /* NB little-endian */ |
Damien Miller | 0fde8ac | 2013-11-21 14:12:23 +1100 | [diff] [blame] | 54 | u_char expected_tag[POLY1305_TAGLEN], poly_key[POLY1305_KEYLEN]; |
| 55 | int r = -1; |
| 56 | |
| 57 | /* |
| 58 | * Run ChaCha20 once to generate the Poly1305 key. The IV is the |
| 59 | * packet sequence number. |
| 60 | */ |
| 61 | bzero(poly_key, sizeof(poly_key)); |
| 62 | put_u64(seqbuf, seqnr); |
| 63 | chacha_ivsetup(&ctx->main_ctx, seqbuf, NULL); |
| 64 | chacha_encrypt_bytes(&ctx->main_ctx, |
| 65 | poly_key, poly_key, sizeof(poly_key)); |
| 66 | /* Set Chacha's block counter to 1 */ |
| 67 | chacha_ivsetup(&ctx->main_ctx, seqbuf, one); |
| 68 | |
| 69 | /* If decrypting, check tag before anything else */ |
| 70 | if (!do_encrypt) { |
| 71 | const u_char *tag = src + aadlen + len; |
| 72 | |
| 73 | poly1305_auth(expected_tag, src, aadlen + len, poly_key); |
| 74 | if (timingsafe_bcmp(expected_tag, tag, POLY1305_TAGLEN) != 0) |
| 75 | goto out; |
| 76 | } |
| 77 | /* Crypt additional data */ |
Damien Miller | d58a596 | 2013-12-18 17:50:13 +1100 | [diff] [blame] | 78 | if (aadlen) { |
Damien Miller | 0fde8ac | 2013-11-21 14:12:23 +1100 | [diff] [blame] | 79 | chacha_ivsetup(&ctx->header_ctx, seqbuf, NULL); |
| 80 | chacha_encrypt_bytes(&ctx->header_ctx, src, dest, aadlen); |
| 81 | } |
| 82 | chacha_encrypt_bytes(&ctx->main_ctx, src + aadlen, |
| 83 | dest + aadlen, len); |
| 84 | |
| 85 | /* If encrypting, calculate and append tag */ |
| 86 | if (do_encrypt) { |
| 87 | poly1305_auth(dest + aadlen + len, dest, aadlen + len, |
| 88 | poly_key); |
| 89 | } |
| 90 | r = 0; |
| 91 | |
| 92 | out: |
| 93 | bzero(expected_tag, sizeof(expected_tag)); |
| 94 | bzero(seqbuf, sizeof(seqbuf)); |
| 95 | bzero(poly_key, sizeof(poly_key)); |
| 96 | return r; |
| 97 | } |
| 98 | |
Damien Miller | d58a596 | 2013-12-18 17:50:13 +1100 | [diff] [blame] | 99 | /* Decrypt and extract the encrypted packet length */ |
Damien Miller | 0fde8ac | 2013-11-21 14:12:23 +1100 | [diff] [blame] | 100 | int |
| 101 | chachapoly_get_length(struct chachapoly_ctx *ctx, |
| 102 | u_int *plenp, u_int seqnr, const u_char *cp, u_int len) |
| 103 | { |
| 104 | u_char buf[4], seqbuf[8]; |
| 105 | |
| 106 | if (len < 4) |
| 107 | return -1; /* Insufficient length */ |
| 108 | put_u64(seqbuf, seqnr); |
| 109 | chacha_ivsetup(&ctx->header_ctx, seqbuf, NULL); |
| 110 | chacha_encrypt_bytes(&ctx->header_ctx, cp, buf, 4); |
| 111 | *plenp = get_u32(buf); |
| 112 | return 0; |
| 113 | } |
| 114 | |