/* $OpenBSD: ssh-ed25519-sk.c,v 1.15 2022/10/28 00:44:44 djm Exp $ */
/*
 * Copyright (c) 2019 Markus Friedl.  All rights reserved.
 *
 * 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.
 */

/* #define DEBUG_SK 1 */

#include "includes.h"

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

#include "crypto_api.h"

#include <string.h>
#include <stdarg.h>

#include "log.h"
#include "sshbuf.h"
#include "sshkey.h"
#include "ssherr.h"
#include "ssh.h"
#include "digest.h"

/* Reuse some ED25519 internals */
extern struct sshkey_impl_funcs sshkey_ed25519_funcs;

static void
ssh_ed25519_sk_cleanup(struct sshkey *k)
{
        sshkey_sk_cleanup(k);
        sshkey_ed25519_funcs.cleanup(k);
}

static int
ssh_ed25519_sk_equal(const struct sshkey *a, const struct sshkey *b)
{
        if (!sshkey_sk_fields_equal(a, b))
                return 0;
        if (!sshkey_ed25519_funcs.equal(a, b))
                return 0;
        return 1;
}

static int
ssh_ed25519_sk_serialize_public(const struct sshkey *key, struct sshbuf *b,
    enum sshkey_serialize_rep opts)
{
        int r;

        if ((r = sshkey_ed25519_funcs.serialize_public(key, b, opts)) != 0)
                return r;
        if ((r = sshkey_serialize_sk(key, b)) != 0)
                return r;

        return 0;
}

static int
ssh_ed25519_sk_serialize_private(const struct sshkey *key, struct sshbuf *b,
    enum sshkey_serialize_rep opts)
{
        int r;

        if ((r = sshkey_ed25519_funcs.serialize_public(key, b, opts)) != 0)
                return r;
        if ((r = sshkey_serialize_private_sk(key, b)) != 0)
                return r;

        return 0;
}

static int
ssh_ed25519_sk_copy_public(const struct sshkey *from, struct sshkey *to)
{
        int r;

        if ((r = sshkey_ed25519_funcs.copy_public(from, to)) != 0)
                return r;
        if ((r = sshkey_copy_public_sk(from, to)) != 0)
                return r;
        return 0;
}

static int
ssh_ed25519_sk_deserialize_public(const char *ktype, struct sshbuf *b,
    struct sshkey *key)
{
        int r;

        if ((r = sshkey_ed25519_funcs.deserialize_public(ktype, b, key)) != 0)
                return r;
        if ((r = sshkey_deserialize_sk(b, key)) != 0)
                return r;
        return 0;
}

static int
ssh_ed25519_sk_deserialize_private(const char *ktype, struct sshbuf *b,
    struct sshkey *key)
{
        int r;

        if ((r = sshkey_ed25519_funcs.deserialize_public(ktype, b, key)) != 0)
                return r;
        if ((r = sshkey_private_deserialize_sk(b, key)) != 0)
                return r;
        return 0;
}

static int
ssh_ed25519_sk_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;
        struct sshbuf *encoded = NULL;
        char *ktype = NULL;
        const u_char *sigblob;
        const u_char *sm;
        u_char *m = NULL;
        u_char apphash[32];
        u_char msghash[32];
        u_char sig_flags;
        u_int sig_counter;
        size_t len;
        unsigned long long smlen = 0, mlen = 0;
        int r = SSH_ERR_INTERNAL_ERROR;
        int ret;
        struct sshkey_sig_details *details = NULL;

        if (detailsp != NULL)
                *detailsp = NULL;

        if (key == NULL ||
            sshkey_type_plain(key->type) != KEY_ED25519_SK ||
            key->ed25519_pk == NULL ||
            sig == NULL || siglen == 0)
                return SSH_ERR_INVALID_ARGUMENT;

        if ((b = sshbuf_from(sig, siglen)) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||
            sshbuf_get_string_direct(b, &sigblob, &len) != 0 ||
            sshbuf_get_u8(b, &sig_flags) != 0 ||
            sshbuf_get_u32(b, &sig_counter) != 0) {
                r = SSH_ERR_INVALID_FORMAT;
                goto out;
        }
#ifdef DEBUG_SK
        fprintf(stderr, "%s: data:\n", __func__);
        /* sshbuf_dump_data(data, datalen, stderr); */
        fprintf(stderr, "%s: sigblob:\n", __func__);
        sshbuf_dump_data(sigblob, len, stderr);
        fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n",
            __func__, sig_flags, sig_counter);
#endif
        if (strcmp(sshkey_ssh_name_plain(key), 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 > crypto_sign_ed25519_BYTES) {
                r = SSH_ERR_INVALID_FORMAT;
                goto out;
        }
        if (ssh_digest_memory(SSH_DIGEST_SHA256, key->sk_application,
            strlen(key->sk_application), apphash, sizeof(apphash)) != 0 ||
            ssh_digest_memory(SSH_DIGEST_SHA256, data, dlen,
            msghash, sizeof(msghash)) != 0) {
                r = SSH_ERR_INVALID_ARGUMENT;
                goto out;
        }
#ifdef DEBUG_SK
        fprintf(stderr, "%s: hashed application:\n", __func__);
        sshbuf_dump_data(apphash, sizeof(apphash), stderr);
        fprintf(stderr, "%s: hashed message:\n", __func__);
        sshbuf_dump_data(msghash, sizeof(msghash), stderr);
#endif
        if ((details = calloc(1, sizeof(*details))) == NULL) {
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
        details->sk_counter = sig_counter;
        details->sk_flags = sig_flags;
        if ((encoded = sshbuf_new()) == NULL) {
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
        if (sshbuf_put(encoded, sigblob, len) != 0 ||
            sshbuf_put(encoded, apphash, sizeof(apphash)) != 0 ||
            sshbuf_put_u8(encoded, sig_flags) != 0 ||
            sshbuf_put_u32(encoded, sig_counter) != 0 ||
            sshbuf_put(encoded, msghash, sizeof(msghash)) != 0) {
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
#ifdef DEBUG_SK
        fprintf(stderr, "%s: signed buf:\n", __func__);
        sshbuf_dump(encoded, stderr);
#endif
        sm = sshbuf_ptr(encoded);
        smlen = sshbuf_len(encoded);
        mlen = smlen;
        if ((m = malloc(smlen)) == NULL) {
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
        if ((ret = crypto_sign_ed25519_open(m, &mlen, sm, smlen,
            key->ed25519_pk)) != 0) {
                debug2_f("crypto_sign_ed25519_open failed: %d", ret);
        }
        if (ret != 0 || mlen != smlen - len) {
                r = SSH_ERR_SIGNATURE_INVALID;
                goto out;
        }
        /* XXX compare 'm' and 'sm + len' ? */
        /* success */
        r = 0;
        if (detailsp != NULL) {
                *detailsp = details;
                details = NULL;
        }
 out:
        if (m != NULL)
                freezero(m, smlen); /* NB mlen may be invalid if r != 0 */
        sshkey_sig_details_free(details);
        sshbuf_free(b);
        sshbuf_free(encoded);
        free(ktype);
        return r;
}

static const struct sshkey_impl_funcs sshkey_ed25519_sk_funcs = {
        /* .size = */           NULL,
        /* .alloc = */          NULL,
        /* .cleanup = */        ssh_ed25519_sk_cleanup,
        /* .equal = */          ssh_ed25519_sk_equal,
        /* .ssh_serialize_public = */ ssh_ed25519_sk_serialize_public,
        /* .ssh_deserialize_public = */ ssh_ed25519_sk_deserialize_public,
        /* .ssh_serialize_private = */ ssh_ed25519_sk_serialize_private,
        /* .ssh_deserialize_private = */ ssh_ed25519_sk_deserialize_private,
        /* .generate = */       NULL,
        /* .copy_public = */    ssh_ed25519_sk_copy_public,
        /* .sign = */           NULL,
        /* .verify = */         ssh_ed25519_sk_verify,
};

const struct sshkey_impl sshkey_ed25519_sk_impl = {
        /* .name = */           "sk-ssh-ed25519@openssh.com",
        /* .shortname = */      "ED25519-SK",
        /* .sigalg = */         NULL,
        /* .type = */           KEY_ED25519_SK,
        /* .nid = */            0,
        /* .cert = */           0,
        /* .sigonly = */        0,
        /* .keybits = */        256,
        /* .funcs = */          &sshkey_ed25519_sk_funcs,
};

const struct sshkey_impl sshkey_ed25519_sk_cert_impl = {
        /* .name = */           "sk-ssh-ed25519-cert-v01@openssh.com",
        /* .shortname = */      "ED25519-SK-CERT",
        /* .sigalg = */         NULL,
        /* .type = */           KEY_ED25519_SK_CERT,
        /* .nid = */            0,
        /* .cert = */           1,
        /* .sigonly = */        0,
        /* .keybits = */        256,
        /* .funcs = */          &sshkey_ed25519_sk_funcs,
};