/* $OpenBSD: mac.c,v 1.35 2019/09/06 04:53:27 djm Exp $ */
/*
 * Copyright (c) 2001 Markus Friedl.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"

#include <sys/types.h>

#include <stdlib.h>
#include <string.h>
#include <stdio.h>

#include "digest.h"
#include "hmac.h"
#include "umac.h"
#include "mac.h"
#include "misc.h"
#include "ssherr.h"
#include "sshbuf.h"

#include "openbsd-compat/openssl-compat.h"

#define SSH_DIGEST      1       /* SSH_DIGEST_XXX */
#define SSH_UMAC        2       /* UMAC (not integrated with OpenSSL) */
#define SSH_UMAC128     3

struct macalg {
        char            *name;
        int             type;
        int             alg;
        int             truncatebits;   /* truncate digest if != 0 */
        int             key_len;        /* just for UMAC */
        int             len;            /* just for UMAC */
        int             etm;            /* Encrypt-then-MAC */
};

static const struct macalg macs[] = {
        /* Encrypt-and-MAC (encrypt-and-authenticate) variants */
        { "hmac-sha1",                          SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 0 },
        { "hmac-sha1-96",                       SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 0 },
        { "hmac-sha2-256",                      SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 0 },
        { "hmac-sha2-512",                      SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 0 },
        { "hmac-md5",                           SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 0 },
        { "hmac-md5-96",                        SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 0 },
        { "umac-64@openssh.com",                SSH_UMAC, 0, 0, 128, 64, 0 },
        { "umac-128@openssh.com",               SSH_UMAC128, 0, 0, 128, 128, 0 },

        /* Encrypt-then-MAC variants */
        { "hmac-sha1-etm@openssh.com",          SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 1 },
        { "hmac-sha1-96-etm@openssh.com",       SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 1 },
        { "hmac-sha2-256-etm@openssh.com",      SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 1 },
        { "hmac-sha2-512-etm@openssh.com",      SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 1 },
        { "hmac-md5-etm@openssh.com",           SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 1 },
        { "hmac-md5-96-etm@openssh.com",        SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 1 },
        { "umac-64-etm@openssh.com",            SSH_UMAC, 0, 0, 128, 64, 1 },
        { "umac-128-etm@openssh.com",           SSH_UMAC128, 0, 0, 128, 128, 1 },

        { NULL,                                 0, 0, 0, 0, 0, 0 }
};

/* Returns a list of supported MACs separated by the specified char. */
char *
mac_alg_list(char sep)
{
        char *ret = NULL, *tmp;
        size_t nlen, rlen = 0;
        const struct macalg *m;

        for (m = macs; m->name != NULL; m++) {
                if (ret != NULL)
                        ret[rlen++] = sep;
                nlen = strlen(m->name);
                if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
                        free(ret);
                        return NULL;
                }
                ret = tmp;
                memcpy(ret + rlen, m->name, nlen + 1);
                rlen += nlen;
        }
        return ret;
}

static int
mac_setup_by_alg(struct sshmac *mac, const struct macalg *macalg)
{
        mac->type = macalg->type;
        if (mac->type == SSH_DIGEST) {
                if ((mac->hmac_ctx = ssh_hmac_start(macalg->alg)) == NULL)
                        return SSH_ERR_ALLOC_FAIL;
                mac->key_len = mac->mac_len = ssh_hmac_bytes(macalg->alg);
        } else {
                mac->mac_len = macalg->len / 8;
                mac->key_len = macalg->key_len / 8;
                mac->umac_ctx = NULL;
        }
        if (macalg->truncatebits != 0)
                mac->mac_len = macalg->truncatebits / 8;
        mac->etm = macalg->etm;
        return 0;
}

int
mac_setup(struct sshmac *mac, char *name)
{
        const struct macalg *m;

        for (m = macs; m->name != NULL; m++) {
                if (strcmp(name, m->name) != 0)
                        continue;
                if (mac != NULL)
                        return mac_setup_by_alg(mac, m);
                return 0;
        }
        return SSH_ERR_INVALID_ARGUMENT;
}

int
mac_init(struct sshmac *mac)
{
        if (mac->key == NULL)
                return SSH_ERR_INVALID_ARGUMENT;
        switch (mac->type) {
        case SSH_DIGEST:
                if (mac->hmac_ctx == NULL ||
                    ssh_hmac_init(mac->hmac_ctx, mac->key, mac->key_len) < 0)
                        return SSH_ERR_INVALID_ARGUMENT;
                return 0;
        case SSH_UMAC:
                if ((mac->umac_ctx = umac_new(mac->key)) == NULL)
                        return SSH_ERR_ALLOC_FAIL;
                return 0;
        case SSH_UMAC128:
                if ((mac->umac_ctx = umac128_new(mac->key)) == NULL)
                        return SSH_ERR_ALLOC_FAIL;
                return 0;
        default:
                return SSH_ERR_INVALID_ARGUMENT;
        }
}

int
mac_compute(struct sshmac *mac, u_int32_t seqno,
    const u_char *data, int datalen,
    u_char *digest, size_t dlen)
{
        static union {
                u_char m[SSH_DIGEST_MAX_LENGTH];
                u_int64_t for_align;
        } u;
        u_char b[4];
        u_char nonce[8];

        if (mac->mac_len > sizeof(u))
                return SSH_ERR_INTERNAL_ERROR;

        switch (mac->type) {
        case SSH_DIGEST:
                put_u32(b, seqno);
                /* reset HMAC context */
                if (ssh_hmac_init(mac->hmac_ctx, NULL, 0) < 0 ||
                    ssh_hmac_update(mac->hmac_ctx, b, sizeof(b)) < 0 ||
                    ssh_hmac_update(mac->hmac_ctx, data, datalen) < 0 ||
                    ssh_hmac_final(mac->hmac_ctx, u.m, sizeof(u.m)) < 0)
                        return SSH_ERR_LIBCRYPTO_ERROR;
                break;
        case SSH_UMAC:
                POKE_U64(nonce, seqno);
                umac_update(mac->umac_ctx, data, datalen);
                umac_final(mac->umac_ctx, u.m, nonce);
                break;
        case SSH_UMAC128:
                put_u64(nonce, seqno);
                umac128_update(mac->umac_ctx, data, datalen);
                umac128_final(mac->umac_ctx, u.m, nonce);
                break;
        default:
                return SSH_ERR_INVALID_ARGUMENT;
        }
        if (digest != NULL) {
                if (dlen > mac->mac_len)
                        dlen = mac->mac_len;
                memcpy(digest, u.m, dlen);
        }
        return 0;
}

int
mac_check(struct sshmac *mac, u_int32_t seqno,
    const u_char *data, size_t dlen,
    const u_char *theirmac, size_t mlen)
{
        u_char ourmac[SSH_DIGEST_MAX_LENGTH];
        int r;

        if (mac->mac_len > mlen)
                return SSH_ERR_INVALID_ARGUMENT;
        if ((r = mac_compute(mac, seqno, data, dlen,
            ourmac, sizeof(ourmac))) != 0)
                return r;
        if (timingsafe_bcmp(ourmac, theirmac, mac->mac_len) != 0)
                return SSH_ERR_MAC_INVALID;
        return 0;
}

void
mac_clear(struct sshmac *mac)
{
        if (mac->type == SSH_UMAC) {
                if (mac->umac_ctx != NULL)
                        umac_delete(mac->umac_ctx);
        } else if (mac->type == SSH_UMAC128) {
                if (mac->umac_ctx != NULL)
                        umac128_delete(mac->umac_ctx);
        } else if (mac->hmac_ctx != NULL)
                ssh_hmac_free(mac->hmac_ctx);
        mac->hmac_ctx = NULL;
        mac->umac_ctx = NULL;
}

/* XXX copied from ciphers_valid */
#define MAC_SEP ","
int
mac_valid(const char *names)
{
        char *maclist, *cp, *p;

        if (names == NULL || strcmp(names, "") == 0)
                return 0;
        if ((maclist = cp = strdup(names)) == NULL)
                return 0;
        for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0';
            (p = strsep(&cp, MAC_SEP))) {
                if (mac_setup(NULL, p) < 0) {
                        free(maclist);
                        return 0;
                }
        }
        free(maclist);
        return 1;
}