Return to cipher-chachapoly.c CVS log

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

Annotation of src/usr.bin/ssh/cipher-chachapoly.c, Revision 1.10

1.10    ! djm         1: /* $OpenBSD: cipher-chachapoly.c,v 1.9 2020/04/03 04:27:03 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:  */
1.2       djm        17:
1.1       djm        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 "log.h"
1.5       djm        24: #include "sshbuf.h"
                     25: #include "ssherr.h"
1.1       djm        26: #include "cipher-chachapoly.h"
                     27:
1.9       djm        28: struct chachapoly_ctx {
                     29:        struct chacha_ctx main_ctx, header_ctx;
                     30: };
                     31:
                     32: struct chachapoly_ctx *
                     33: chachapoly_new(const u_char *key, u_int keylen)
1.1       djm        34: {
1.9       djm        35:        struct chachapoly_ctx *ctx;
                     36:
1.1       djm        37:        if (keylen != (32 + 32)) /* 2 x 256 bit keys */
1.9       djm        38:                return NULL;
                     39:        if ((ctx = calloc(1, sizeof(*ctx))) == NULL)
                     40:                return NULL;
1.1       djm        41:        chacha_keysetup(&ctx->main_ctx, key, 256);
                     42:        chacha_keysetup(&ctx->header_ctx, key + 32, 256);
1.9       djm        43:        return ctx;
                     44: }
                     45:
                     46: void
                     47: chachapoly_free(struct chachapoly_ctx *cpctx)
                     48: {
                     49:        freezero(cpctx, sizeof(*cpctx));
1.1       djm        50: }
                     51:
                     52: /*
                     53:  * chachapoly_crypt() operates as following:
1.3       djm        54:  * En/decrypt with header key 'aadlen' bytes from 'src', storing result
                     55:  * to 'dest'. The ciphertext here is treated as additional authenticated
                     56:  * data for MAC calculation.
                     57:  * En/decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. Use
                     58:  * POLY1305_TAGLEN bytes at offset 'len'+'aadlen' as the authentication
                     59:  * tag. This tag is written on encryption and verified on decryption.
1.1       djm        60:  */
                     61: int
                     62: chachapoly_crypt(struct chachapoly_ctx *ctx, u_int seqnr, u_char *dest,
                     63:     const u_char *src, u_int len, u_int aadlen, u_int authlen, int do_encrypt)
                     64: {
                     65:        u_char seqbuf[8];
1.3       djm        66:        const u_char one[8] = { 1, 0, 0, 0, 0, 0, 0, 0 }; /* NB little-endian */
1.1       djm        67:        u_char expected_tag[POLY1305_TAGLEN], poly_key[POLY1305_KEYLEN];
1.5       djm        68:        int r = SSH_ERR_INTERNAL_ERROR;
1.1       djm        69:
                     70:        /*
                     71:         * Run ChaCha20 once to generate the Poly1305 key. The IV is the
                     72:         * packet sequence number.
                     73:         */
1.4       tedu       74:        memset(poly_key, 0, sizeof(poly_key));
1.5       djm        75:        POKE_U64(seqbuf, seqnr);
1.1       djm        76:        chacha_ivsetup(&ctx->main_ctx, seqbuf, NULL);
                     77:        chacha_encrypt_bytes(&ctx->main_ctx,
                     78:            poly_key, poly_key, sizeof(poly_key));
                     79:
                     80:        /* If decrypting, check tag before anything else */
                     81:        if (!do_encrypt) {
                     82:                const u_char *tag = src + aadlen + len;
                     83:
                     84:                poly1305_auth(expected_tag, src, aadlen + len, poly_key);
1.5       djm        85:                if (timingsafe_bcmp(expected_tag, tag, POLY1305_TAGLEN) != 0) {
                     86:                        r = SSH_ERR_MAC_INVALID;
1.1       djm        87:                        goto out;
1.5       djm        88:                }
1.1       djm        89:        }
1.6       jsing      90:
1.1       djm        91:        /* Crypt additional data */
1.3       djm        92:        if (aadlen) {
1.1       djm        93:                chacha_ivsetup(&ctx->header_ctx, seqbuf, NULL);
                     94:                chacha_encrypt_bytes(&ctx->header_ctx, src, dest, aadlen);
                     95:        }
1.6       jsing      96:
                     97:        /* Set Chacha's block counter to 1 */
                     98:        chacha_ivsetup(&ctx->main_ctx, seqbuf, one);
1.1       djm        99:        chacha_encrypt_bytes(&ctx->main_ctx, src + aadlen,
                    100:            dest + aadlen, len);
                    101:
                    102:        /* If encrypting, calculate and append tag */
                    103:        if (do_encrypt) {
                    104:                poly1305_auth(dest + aadlen + len, dest, aadlen + len,
                    105:                    poly_key);
                    106:        }
                    107:        r = 0;
                    108:  out:
1.4       tedu      109:        explicit_bzero(expected_tag, sizeof(expected_tag));
                    110:        explicit_bzero(seqbuf, sizeof(seqbuf));
                    111:        explicit_bzero(poly_key, sizeof(poly_key));
1.1       djm       112:        return r;
                    113: }
                    114:
1.3       djm       115: /* Decrypt and extract the encrypted packet length */
1.1       djm       116: int
                    117: chachapoly_get_length(struct chachapoly_ctx *ctx,
                    118:     u_int *plenp, u_int seqnr, const u_char *cp, u_int len)
                    119: {
                    120:        u_char buf[4], seqbuf[8];
                    121:
                    122:        if (len < 4)
1.5       djm       123:                return SSH_ERR_MESSAGE_INCOMPLETE;
                    124:        POKE_U64(seqbuf, seqnr);
1.1       djm       125:        chacha_ivsetup(&ctx->header_ctx, seqbuf, NULL);
                    126:        chacha_encrypt_bytes(&ctx->header_ctx, cp, buf, 4);
1.5       djm       127:        *plenp = PEEK_U32(buf);
1.1       djm       128:        return 0;
                    129: }