Return to cipher-chachapoly.c CVS log

Up to [local] / src / usr.bin / ssh

Annotation of src/usr.bin/ssh/cipher-chachapoly.c, Revision 1.8

1.1       djm         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:
1.8     ! djm        17: /* $OpenBSD: cipher-chachapoly.c,v 1.7 2015/01/14 10:24:42 markus Exp $ */
1.2       djm        18:
1.1       djm        19: #include <sys/types.h>
                     20: #include <stdarg.h> /* needed for log.h */
                     21: #include <string.h>
                     22: #include <stdio.h>  /* needed for misc.h */
                     23:
                     24: #include "log.h"
1.5       djm        25: #include "sshbuf.h"
                     26: #include "ssherr.h"
1.1       djm        27: #include "cipher-chachapoly.h"
                     28:
1.8     ! djm        29: int
        !            30: chachapoly_init(struct chachapoly_ctx *ctx,
1.1       djm        31:     const u_char *key, u_int keylen)
                     32: {
                     33:        if (keylen != (32 + 32)) /* 2 x 256 bit keys */
1.5       djm        34:                return SSH_ERR_INVALID_ARGUMENT;
1.1       djm        35:        chacha_keysetup(&ctx->main_ctx, key, 256);
                     36:        chacha_keysetup(&ctx->header_ctx, key + 32, 256);
1.5       djm        37:        return 0;
1.1       djm        38: }
                     39:
                     40: /*
                     41:  * chachapoly_crypt() operates as following:
1.3       djm        42:  * En/decrypt with header key 'aadlen' bytes from 'src', storing result
                     43:  * to 'dest'. The ciphertext here is treated as additional authenticated
                     44:  * data for MAC calculation.
                     45:  * En/decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. Use
                     46:  * POLY1305_TAGLEN bytes at offset 'len'+'aadlen' as the authentication
                     47:  * tag. This tag is written on encryption and verified on decryption.
1.1       djm        48:  */
                     49: int
                     50: chachapoly_crypt(struct chachapoly_ctx *ctx, u_int seqnr, u_char *dest,
                     51:     const u_char *src, u_int len, u_int aadlen, u_int authlen, int do_encrypt)
                     52: {
                     53:        u_char seqbuf[8];
1.3       djm        54:        const u_char one[8] = { 1, 0, 0, 0, 0, 0, 0, 0 }; /* NB little-endian */
1.1       djm        55:        u_char expected_tag[POLY1305_TAGLEN], poly_key[POLY1305_KEYLEN];
1.5       djm        56:        int r = SSH_ERR_INTERNAL_ERROR;
1.1       djm        57:
                     58:        /*
                     59:         * Run ChaCha20 once to generate the Poly1305 key. The IV is the
                     60:         * packet sequence number.
                     61:         */
1.4       tedu       62:        memset(poly_key, 0, sizeof(poly_key));
1.5       djm        63:        POKE_U64(seqbuf, seqnr);
1.1       djm        64:        chacha_ivsetup(&ctx->main_ctx, seqbuf, NULL);
                     65:        chacha_encrypt_bytes(&ctx->main_ctx,
                     66:            poly_key, poly_key, sizeof(poly_key));
                     67:
                     68:        /* If decrypting, check tag before anything else */
                     69:        if (!do_encrypt) {
                     70:                const u_char *tag = src + aadlen + len;
                     71:
                     72:                poly1305_auth(expected_tag, src, aadlen + len, poly_key);
1.5       djm        73:                if (timingsafe_bcmp(expected_tag, tag, POLY1305_TAGLEN) != 0) {
                     74:                        r = SSH_ERR_MAC_INVALID;
1.1       djm        75:                        goto out;
1.5       djm        76:                }
1.1       djm        77:        }
1.6       jsing      78:
1.1       djm        79:        /* Crypt additional data */
1.3       djm        80:        if (aadlen) {
1.1       djm        81:                chacha_ivsetup(&ctx->header_ctx, seqbuf, NULL);
                     82:                chacha_encrypt_bytes(&ctx->header_ctx, src, dest, aadlen);
                     83:        }
1.6       jsing      84:
                     85:        /* Set Chacha's block counter to 1 */
                     86:        chacha_ivsetup(&ctx->main_ctx, seqbuf, one);
1.1       djm        87:        chacha_encrypt_bytes(&ctx->main_ctx, src + aadlen,
                     88:            dest + aadlen, len);
                     89:
                     90:        /* If encrypting, calculate and append tag */
                     91:        if (do_encrypt) {
                     92:                poly1305_auth(dest + aadlen + len, dest, aadlen + len,
                     93:                    poly_key);
                     94:        }
                     95:        r = 0;
                     96:  out:
1.4       tedu       97:        explicit_bzero(expected_tag, sizeof(expected_tag));
                     98:        explicit_bzero(seqbuf, sizeof(seqbuf));
                     99:        explicit_bzero(poly_key, sizeof(poly_key));
1.1       djm       100:        return r;
                    101: }
                    102:
1.3       djm       103: /* Decrypt and extract the encrypted packet length */
1.1       djm       104: int
                    105: chachapoly_get_length(struct chachapoly_ctx *ctx,
                    106:     u_int *plenp, u_int seqnr, const u_char *cp, u_int len)
                    107: {
                    108:        u_char buf[4], seqbuf[8];
                    109:
                    110:        if (len < 4)
1.5       djm       111:                return SSH_ERR_MESSAGE_INCOMPLETE;
                    112:        POKE_U64(seqbuf, seqnr);
1.1       djm       113:        chacha_ivsetup(&ctx->header_ctx, seqbuf, NULL);
                    114:        chacha_encrypt_bytes(&ctx->header_ctx, cp, buf, 4);
1.5       djm       115:        *plenp = PEEK_U32(buf);
1.1       djm       116:        return 0;
                    117: }