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- /*
- * Copyright (c) 2013 Damien Miller <djm@mindrot.org>
- *
- * 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.
- */
- /* $OpenBSD: cipher-chachapoly.c,v 1.2 2013/11/21 02:50:00 djm Exp $ */
- #include <sys/types.h>
- #include <stdarg.h> /* needed for log.h */
- #include <string.h>
- #include <stdio.h> /* needed for misc.h */
- #include "log.h"
- #include "misc.h"
- #include "cipher-chachapoly.h"
- void chachapoly_init(struct chachapoly_ctx *ctx,
- const u_char *key, u_int keylen)
- {
- if (keylen != (32 + 32)) /* 2 x 256 bit keys */
- fatal("%s: invalid keylen %u", __func__, keylen);
- chacha_keysetup(&ctx->main_ctx, key, 256);
- chacha_keysetup(&ctx->header_ctx, key + 32, 256);
- }
- /*
- * chachapoly_crypt() operates as following:
- * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'.
- * Theses bytes are treated as additional authenticated data.
- * 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.
- * Both 'aadlen' and 'authlen' can be set to 0.
- */
- int
- chachapoly_crypt(struct chachapoly_ctx *ctx, u_int seqnr, u_char *dest,
- const u_char *src, u_int len, u_int aadlen, u_int authlen, int do_encrypt)
- {
- u_char seqbuf[8];
- 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 = -1;
- /*
- * Run ChaCha20 once to generate the Poly1305 key. The IV is the
- * packet sequence number.
- */
- bzero(poly_key, sizeof(poly_key));
- put_u64(seqbuf, seqnr);
- chacha_ivsetup(&ctx->main_ctx, seqbuf, NULL);
- chacha_encrypt_bytes(&ctx->main_ctx,
- poly_key, poly_key, sizeof(poly_key));
- /* Set Chacha's block counter to 1 */
- chacha_ivsetup(&ctx->main_ctx, seqbuf, one);
- /* 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 (timingsafe_bcmp(expected_tag, tag, POLY1305_TAGLEN) != 0)
- goto out;
- }
- /* Crypt additional data */
- if (aadlen) {
- chacha_ivsetup(&ctx->header_ctx, seqbuf, NULL);
- chacha_encrypt_bytes(&ctx->header_ctx, src, dest, aadlen);
- }
- 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:
- bzero(expected_tag, sizeof(expected_tag));
- bzero(seqbuf, sizeof(seqbuf));
- bzero(poly_key, sizeof(poly_key));
- return r;
- }
- int
- chachapoly_get_length(struct chachapoly_ctx *ctx,
- u_int *plenp, u_int seqnr, const u_char *cp, u_int len)
- {
- u_char buf[4], seqbuf[8];
- if (len < 4)
- return -1; /* Insufficient length */
- put_u64(seqbuf, seqnr);
- chacha_ivsetup(&ctx->header_ctx, seqbuf, NULL);
- chacha_encrypt_bytes(&ctx->header_ctx, cp, buf, 4);
- *plenp = get_u32(buf);
- return 0;
- }
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