/* $OpenBSD: ssh-xmss.c,v 1.14 2022/10/28 00:44:44 djm Exp $*/
/*
 * Copyright (c) 2017 Stefan-Lukas Gazdag.
 * Copyright (c) 2017 Markus Friedl.
 *
 * 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.
 */
#include "includes.h"
#ifdef WITH_XMSS

#define SSHKEY_INTERNAL
#include <sys/types.h>
#include <limits.h>

#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#ifdef HAVE_STDINT_H
# include <stdint.h>
#endif
#include <unistd.h>

#include "log.h"
#include "sshbuf.h"
#include "sshkey.h"
#include "sshkey-xmss.h"
#include "ssherr.h"
#include "ssh.h"

#include "xmss_fast.h"

static void
ssh_xmss_cleanup(struct sshkey *k)
{
        freezero(k->xmss_pk, sshkey_xmss_pklen(k));
        freezero(k->xmss_sk, sshkey_xmss_sklen(k));
        sshkey_xmss_free_state(k);
        free(k->xmss_name);
        free(k->xmss_filename);
        k->xmss_pk = NULL;
        k->xmss_sk = NULL;
        k->xmss_name = NULL;
        k->xmss_filename = NULL;
}

static int
ssh_xmss_equal(const struct sshkey *a, const struct sshkey *b)
{
        if (a->xmss_pk == NULL || b->xmss_pk == NULL)
                return 0;
        if (sshkey_xmss_pklen(a) != sshkey_xmss_pklen(b))
                return 0;
        if (memcmp(a->xmss_pk, b->xmss_pk, sshkey_xmss_pklen(a)) != 0)
                return 0;
        return 1;
}

static int
ssh_xmss_serialize_public(const struct sshkey *key, struct sshbuf *b,
    enum sshkey_serialize_rep opts)
{
        int r;

        if (key->xmss_name == NULL || key->xmss_pk == NULL ||
            sshkey_xmss_pklen(key) == 0)
                return SSH_ERR_INVALID_ARGUMENT;
        if ((r = sshbuf_put_cstring(b, key->xmss_name)) != 0 ||
            (r = sshbuf_put_string(b, key->xmss_pk,
            sshkey_xmss_pklen(key))) != 0 ||
            (r = sshkey_xmss_serialize_pk_info(key, b, opts)) != 0)
                return r;

        return 0;
}

static int
ssh_xmss_serialize_private(const struct sshkey *key, struct sshbuf *b,
    enum sshkey_serialize_rep opts)
{
        int r;

        if (key->xmss_name == NULL)
                return SSH_ERR_INVALID_ARGUMENT;
        /* Note: can't reuse ssh_xmss_serialize_public because of sk order */
        if ((r = sshbuf_put_cstring(b, key->xmss_name)) != 0 ||
            (r = sshbuf_put_string(b, key->xmss_pk,
            sshkey_xmss_pklen(key))) != 0 ||
            (r = sshbuf_put_string(b, key->xmss_sk,
            sshkey_xmss_sklen(key))) != 0 ||
            (r = sshkey_xmss_serialize_state_opt(key, b, opts)) != 0)
                return r;

        return 0;
}

static int
ssh_xmss_copy_public(const struct sshkey *from, struct sshkey *to)
{
        int r = SSH_ERR_INTERNAL_ERROR;
        u_int32_t left;
        size_t pklen;

        if ((r = sshkey_xmss_init(to, from->xmss_name)) != 0)
                return r;
        if (from->xmss_pk == NULL)
                return 0; /* XXX SSH_ERR_INTERNAL_ERROR ? */

        if ((pklen = sshkey_xmss_pklen(from)) == 0 ||
            sshkey_xmss_pklen(to) != pklen)
                return SSH_ERR_INTERNAL_ERROR;
        if ((to->xmss_pk = malloc(pklen)) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        memcpy(to->xmss_pk, from->xmss_pk, pklen);
        /* simulate number of signatures left on pubkey */
        left = sshkey_xmss_signatures_left(from);
        if (left)
                sshkey_xmss_enable_maxsign(to, left);
        return 0;
}

static int
ssh_xmss_deserialize_public(const char *ktype, struct sshbuf *b,
    struct sshkey *key)
{
        size_t len = 0;
        char *xmss_name = NULL;
        u_char *pk = NULL;
        int ret = SSH_ERR_INTERNAL_ERROR;

        if ((ret = sshbuf_get_cstring(b, &xmss_name, NULL)) != 0)
                goto out;
        if ((ret = sshkey_xmss_init(key, xmss_name)) != 0)
                goto out;
        if ((ret = sshbuf_get_string(b, &pk, &len)) != 0)
                goto out;
        if (len == 0 || len != sshkey_xmss_pklen(key)) {
                ret = SSH_ERR_INVALID_FORMAT;
                goto out;
        }
        key->xmss_pk = pk;
        pk = NULL;
        if (!sshkey_is_cert(key) &&
            (ret = sshkey_xmss_deserialize_pk_info(key, b)) != 0)
                goto out;
        /* success */
        ret = 0;
 out:
        free(xmss_name);
        freezero(pk, len);
        return ret;
}

static int
ssh_xmss_deserialize_private(const char *ktype, struct sshbuf *b,
    struct sshkey *key)
{
        int r;
        char *xmss_name = NULL;
        size_t pklen = 0, sklen = 0;
        u_char *xmss_pk = NULL, *xmss_sk = NULL;

        /* Note: can't reuse ssh_xmss_deserialize_public because of sk order */
        if ((r = sshbuf_get_cstring(b, &xmss_name, NULL)) != 0 ||
            (r = sshbuf_get_string(b, &xmss_pk, &pklen)) != 0 ||
            (r = sshbuf_get_string(b, &xmss_sk, &sklen)) != 0)
                goto out;
        if (!sshkey_is_cert(key) &&
            (r = sshkey_xmss_init(key, xmss_name)) != 0)
                goto out;
        if (pklen != sshkey_xmss_pklen(key) ||
            sklen != sshkey_xmss_sklen(key)) {
                r = SSH_ERR_INVALID_FORMAT;
                goto out;
        }
        key->xmss_pk = xmss_pk;
        key->xmss_sk = xmss_sk;
        xmss_pk = xmss_sk = NULL;
        /* optional internal state */
        if ((r = sshkey_xmss_deserialize_state_opt(key, b)) != 0)
                goto out;
        /* success */
        r = 0;
 out:
        free(xmss_name);
        freezero(xmss_pk, pklen);
        freezero(xmss_sk, sklen);
        return r;
}

static int
ssh_xmss_sign(struct sshkey *key,
    u_char **sigp, size_t *lenp,
    const u_char *data, size_t datalen,
    const char *alg, const char *sk_provider, const char *sk_pin, u_int compat)
{
        u_char *sig = NULL;
        size_t slen = 0, len = 0, required_siglen;
        unsigned long long smlen;
        int r, ret;
        struct sshbuf *b = NULL;

        if (lenp != NULL)
                *lenp = 0;
        if (sigp != NULL)
                *sigp = NULL;

        if (key == NULL ||
            sshkey_type_plain(key->type) != KEY_XMSS ||
            key->xmss_sk == NULL ||
            sshkey_xmss_params(key) == NULL)
                return SSH_ERR_INVALID_ARGUMENT;
        if ((r = sshkey_xmss_siglen(key, &required_siglen)) != 0)
                return r;
        if (datalen >= INT_MAX - required_siglen)
                return SSH_ERR_INVALID_ARGUMENT;
        smlen = slen = datalen + required_siglen;
        if ((sig = malloc(slen)) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        if ((r = sshkey_xmss_get_state(key, 1)) != 0)
                goto out;
        if ((ret = xmss_sign(key->xmss_sk, sshkey_xmss_bds_state(key), sig, &smlen,
            data, datalen, sshkey_xmss_params(key))) != 0 || smlen <= datalen) {
                r = SSH_ERR_INVALID_ARGUMENT; /* XXX better error? */
                goto out;
        }
        /* encode signature */
        if ((b = sshbuf_new()) == NULL) {
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
        if ((r = sshbuf_put_cstring(b, "ssh-xmss@openssh.com")) != 0 ||
            (r = sshbuf_put_string(b, sig, smlen - datalen)) != 0)
                goto out;
        len = sshbuf_len(b);
        if (sigp != NULL) {
                if ((*sigp = malloc(len)) == NULL) {
                        r = SSH_ERR_ALLOC_FAIL;
                        goto out;
                }
                memcpy(*sigp, sshbuf_ptr(b), len);
        }
        if (lenp != NULL)
                *lenp = len;
        /* success */
        r = 0;
 out:
        if ((ret = sshkey_xmss_update_state(key, 1)) != 0) {
                /* discard signature since we cannot update the state */
                if (r == 0 && sigp != NULL && *sigp != NULL) {
                        explicit_bzero(*sigp, len);
                        free(*sigp);
                }
                if (sigp != NULL)
                        *sigp = NULL;
                if (lenp != NULL)
                        *lenp = 0;
                r = ret;
        }
        sshbuf_free(b);
        if (sig != NULL)
                freezero(sig, slen);

        return r;
}

static int
ssh_xmss_verify(const struct sshkey *key,
    const u_char *sig, size_t siglen,
    const u_char *data, size_t dlen, const char *alg, u_int compat,
    struct sshkey_sig_details **detailsp)
{
        struct sshbuf *b = NULL;
        char *ktype = NULL;
        const u_char *sigblob;
        u_char *sm = NULL, *m = NULL;
        size_t len, required_siglen;
        unsigned long long smlen = 0, mlen = 0;
        int r, ret;

        if (key == NULL ||
            sshkey_type_plain(key->type) != KEY_XMSS ||
            key->xmss_pk == NULL ||
            sshkey_xmss_params(key) == NULL ||
            sig == NULL || siglen == 0)
                return SSH_ERR_INVALID_ARGUMENT;
        if ((r = sshkey_xmss_siglen(key, &required_siglen)) != 0)
                return r;
        if (dlen >= INT_MAX - required_siglen)
                return SSH_ERR_INVALID_ARGUMENT;

        if ((b = sshbuf_from(sig, siglen)) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        if ((r = sshbuf_get_cstring(b, &ktype, NULL)) != 0 ||
            (r = sshbuf_get_string_direct(b, &sigblob, &len)) != 0)
                goto out;
        if (strcmp("ssh-xmss@openssh.com", ktype) != 0) {
                r = SSH_ERR_KEY_TYPE_MISMATCH;
                goto out;
        }
        if (sshbuf_len(b) != 0) {
                r = SSH_ERR_UNEXPECTED_TRAILING_DATA;
                goto out;
        }
        if (len != required_siglen) {
                r = SSH_ERR_INVALID_FORMAT;
                goto out;
        }
        if (dlen >= SIZE_MAX - len) {
                r = SSH_ERR_INVALID_ARGUMENT;
                goto out;
        }
        smlen = len + dlen;
        mlen = smlen;
        if ((sm = malloc(smlen)) == NULL || (m = malloc(mlen)) == NULL) {
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
        memcpy(sm, sigblob, len);
        memcpy(sm+len, data, dlen);
        if ((ret = xmss_sign_open(m, &mlen, sm, smlen,
            key->xmss_pk, sshkey_xmss_params(key))) != 0) {
                debug2_f("xmss_sign_open failed: %d", ret);
        }
        if (ret != 0 || mlen != dlen) {
                r = SSH_ERR_SIGNATURE_INVALID;
                goto out;
        }
        /* XXX compare 'm' and 'data' ? */
        /* success */
        r = 0;
 out:
        if (sm != NULL)
                freezero(sm, smlen);
        if (m != NULL)
                freezero(m, smlen);
        sshbuf_free(b);
        free(ktype);
        return r;
}

static const struct sshkey_impl_funcs sshkey_xmss_funcs = {
        /* .size = */           NULL,
        /* .alloc = */          NULL,
        /* .cleanup = */        ssh_xmss_cleanup,
        /* .equal = */          ssh_xmss_equal,
        /* .ssh_serialize_public = */ ssh_xmss_serialize_public,
        /* .ssh_deserialize_public = */ ssh_xmss_deserialize_public,
        /* .ssh_serialize_private = */ ssh_xmss_serialize_private,
        /* .ssh_deserialize_private = */ ssh_xmss_deserialize_private,
        /* .generate = */       sshkey_xmss_generate_private_key,
        /* .copy_public = */    ssh_xmss_copy_public,
        /* .sign = */           ssh_xmss_sign,
        /* .verify = */         ssh_xmss_verify,
};

const struct sshkey_impl sshkey_xmss_impl = {
        /* .name = */           "ssh-xmss@openssh.com",
        /* .shortname = */      "XMSS",
        /* .sigalg = */         NULL,
        /* .type = */           KEY_XMSS,
        /* .nid = */            0,
        /* .cert = */           0,
        /* .sigonly = */        0,
        /* .keybits = */        256,
        /* .funcs = */          &sshkey_xmss_funcs,
};

const struct sshkey_impl sshkey_xmss_cert_impl = {
        /* .name = */           "ssh-xmss-cert-v01@openssh.com",
        /* .shortname = */      "XMSS-CERT",
        /* .sigalg = */         NULL,
        /* .type = */           KEY_XMSS_CERT,
        /* .nid = */            0,
        /* .cert = */           1,
        /* .sigonly = */        0,
        /* .keybits = */        256,
        /* .funcs = */          &sshkey_xmss_funcs,
};
#endif /* WITH_XMSS */