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/* |
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* Copyright (c) 2013 Damien Miller <djm@mindrot.org> |
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* |
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* Permission to use, copy, modify, and distribute this software for any |
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* purpose with or without fee is hereby granted, provided that the above |
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* copyright notice and this permission notice appear in all copies. |
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* |
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR |
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN |
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF |
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
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*/ |
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|
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/* $OpenBSD: cipher-chachapoly.c,v 1.8 2016/08/03 05:41:57 djm Exp $ */ |
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|
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#include "includes.h" |
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|
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#include <sys/types.h> |
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#include <stdarg.h> /* needed for log.h */ |
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#include <string.h> |
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#include <stdio.h> /* needed for misc.h */ |
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|
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#include "log.h" |
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#include "sshbuf.h" |
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#include "ssherr.h" |
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#include "cipher-chachapoly.h" |
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|
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int |
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chachapoly_init(struct chachapoly_ctx *ctx, |
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const u_char *key, u_int keylen) |
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{ |
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if (keylen != (32 + 32)) /* 2 x 256 bit keys */ |
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return SSH_ERR_INVALID_ARGUMENT; |
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chacha_keysetup(&ctx->main_ctx, key, 256); |
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chacha_keysetup(&ctx->header_ctx, key + 32, 256); |
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return 0; |
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} |
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|
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/* |
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* chachapoly_crypt() operates as following: |
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* En/decrypt with header key 'aadlen' bytes from 'src', storing result |
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* to 'dest'. The ciphertext here is treated as additional authenticated |
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* data for MAC calculation. |
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* En/decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. Use |
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* POLY1305_TAGLEN bytes at offset 'len'+'aadlen' as the authentication |
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* tag. This tag is written on encryption and verified on decryption. |
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*/ |
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int |
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chachapoly_crypt(struct chachapoly_ctx *ctx, u_int seqnr, u_char *dest, |
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const u_char *src, u_int len, u_int aadlen, u_int authlen, int do_encrypt) |
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{ |
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u_char seqbuf[8]; |
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const u_char one[8] = { 1, 0, 0, 0, 0, 0, 0, 0 }; /* NB little-endian */ |
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u_char expected_tag[POLY1305_TAGLEN], poly_key[POLY1305_KEYLEN]; |
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int r = SSH_ERR_INTERNAL_ERROR; |
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|
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/* |
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* Run ChaCha20 once to generate the Poly1305 key. The IV is the |
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* packet sequence number. |
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*/ |
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memset(poly_key, 0, sizeof(poly_key)); |
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POKE_U64(seqbuf, seqnr); |
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chacha_ivsetup(&ctx->main_ctx, seqbuf, NULL); |
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chacha_encrypt_bytes(&ctx->main_ctx, |
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poly_key, poly_key, sizeof(poly_key)); |
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|
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/* If decrypting, check tag before anything else */ |
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if (!do_encrypt) { |
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const u_char *tag = src + aadlen + len; |
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|
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poly1305_auth(expected_tag, src, aadlen + len, poly_key); |
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if (timingsafe_bcmp(expected_tag, tag, POLY1305_TAGLEN) != 0) { |
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r = SSH_ERR_MAC_INVALID; |
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goto out; |
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} |
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} |
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|
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/* Crypt additional data */ |
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if (aadlen) { |
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chacha_ivsetup(&ctx->header_ctx, seqbuf, NULL); |
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chacha_encrypt_bytes(&ctx->header_ctx, src, dest, aadlen); |
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} |
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|
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/* Set Chacha's block counter to 1 */ |
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chacha_ivsetup(&ctx->main_ctx, seqbuf, one); |
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chacha_encrypt_bytes(&ctx->main_ctx, src + aadlen, |
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dest + aadlen, len); |
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|
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/* If encrypting, calculate and append tag */ |
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if (do_encrypt) { |
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poly1305_auth(dest + aadlen + len, dest, aadlen + len, |
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poly_key); |
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} |
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r = 0; |
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out: |
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explicit_bzero(expected_tag, sizeof(expected_tag)); |
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explicit_bzero(seqbuf, sizeof(seqbuf)); |
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explicit_bzero(poly_key, sizeof(poly_key)); |
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return r; |
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} |
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|
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/* Decrypt and extract the encrypted packet length */ |
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int |
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chachapoly_get_length(struct chachapoly_ctx *ctx, |
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u_int *plenp, u_int seqnr, const u_char *cp, u_int len) |
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{ |
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u_char buf[4], seqbuf[8]; |
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|
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if (len < 4) |
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return SSH_ERR_MESSAGE_INCOMPLETE; |
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POKE_U64(seqbuf, seqnr); |
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chacha_ivsetup(&ctx->header_ctx, seqbuf, NULL); |
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chacha_encrypt_bytes(&ctx->header_ctx, cp, buf, 4); |
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*plenp = PEEK_U32(buf); |
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return 0; |
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} |
