/*
 * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
 * 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.
 * 3. Neither the name of Hyra nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT OWNER OR CONTRIBUTORS 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 <net/stpsession.h>
#include <net/param.h>
#include <crypto/ecdh.h>
#include <arpa/inet.h>
#include <defs.h>
#include <stdio.h>
#include <stdint.h>
#include <unistd.h>
#include <string.h>

#define CENTRAL_SERVER "149.248.6.149"
#define OSTP_PORT 5352

static const char *pap_codestr[] = {
    [PAP_SUCCESS]   = "success",
    [PAP_BAD_SPW]   = "bad SPW",
    [PAP_BAD_PERMS] = "insufficient permissions",
    [PAP_RESOURCE]  = "server out of resources"
};

static void
log_pubkey(uint8_t pubkey[])
{
    for (size_t i = 0; i < 32; ++i) {
        printf("%02X ", pubkey[i] & 0xFF);
        if (i != 0 && i % 4 == 0) {
            printf("\n");
        }
    }
    printf("\n");
}

static int
negotiate_spw(int sockfd, const unsigned char *session_key)
{
    struct aes_message am;
    struct msg_frame msg_frame;
    struct pap pap;
    unsigned char *tmp;
    int error;

    /* Create a PAP and encrypt it */
    pap.spw = 0x8000;
    pap.code = 0;

    while (1) {
        if ((error = send_frame(sockfd, &pap, sizeof(pap), session_key)) < 0) {
            return error;
        }

        /* Receive the PAP the server replies with */
        if ((error = recv_frame(sockfd, sizeof(pap), session_key, &pap)) < 0) {
            return error;
        }

        /*
         * If the server echos our PAP with code 0 then it has
         * applied our session parameters! However, there is
         * a chance arbitration will be needed and we need
         * to look out for that too...
         */
        if (pap.code == 0) {
            printf("** Negotiation success\n");
            break;
        }

        printf("** Arbitration needed, server says: %s\n", pap_codestr[pap.code]);
        printf("** Server proposes SPW of 0x%0X, accepting\n", pap.spw);
        pap.spw |= PAP_SPW_QSR;
        pap.code = 0;
    }

    return 0;
}

static void
recv_motd(int sockfd, const unsigned char *session_key)
{
    char buf[4096];
    int len;

    /* Receive the PAP the server replies with */
    if ((len = recv_frame(sockfd, sizeof(buf), session_key, buf)) < 0) {
        printf("Failed to recv MOTD...\n");
        return;
    }

    buf[len] = '\0';
    printf("%s\n", buf);
}

static int
request_session(void)
{
    struct sockaddr_in addr;
    struct session_request stp_sq;
    struct x25519_keypair keypair;
    unsigned char serv_pubkey[32];
    unsigned char *session_key;
    int error, sockfd;

    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = inet_addr(CENTRAL_SERVER);
    addr.sin_port = htons(OSTP_PORT);

    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        return sockfd;
    }

    error = connect(sockfd, (struct sockaddr *)&addr, sizeof(addr));
    if (error < 0) {
        printf("Failed to connect!\n");
        close(sockfd);
        return error;
    }

    printf("Generating keys...\n");

    /* Generate an ephemeral keypair */
    if ((error = gen_x25519_keypair(&keypair)) < 0) {
        printf("Key generation failed!\n");
        close(sockfd);
        return error;
    }

    /*
     * Setup the session request and add our public
     * key to it.
     *
     * TODO: Use the 'U' bit in options.
     */
    memset(stp_sq.hash, 0, sizeof(stp_sq.hash));
    stp_sq.options = 0;
    memcpy(stp_sq.pubkey, keypair.pubkey, sizeof(stp_sq.pubkey));
    log_pubkey(keypair.pubkey);

    printf("Sending session request...\n");
    error = send(sockfd, &stp_sq, sizeof(stp_sq), 0);
    if (error < 0) {
        perror("Failed to send session request");
        close(sockfd);
        return error;
    }

    error = recv(sockfd, serv_pubkey, sizeof(serv_pubkey), 0);
    if (error < 0) {
        perror("Failed to get public key from peer\n");
        close(sockfd);
        return error;
    }

    if (error == 0) {
        printf("Connection closed by peer\n");
        close(sockfd);
        return 0;
    }

    printf("Got public key from server\n");
    log_pubkey(serv_pubkey);

    printf("Deriving session key...\n");
    gen_session_key(keypair.privkey, serv_pubkey, &session_key);

    /* Send server SPW bits */
    if ((error = negotiate_spw(sockfd, session_key)) < 0) {
        printf("Session Parameter Negotiation failed\n");
        free_session_key(session_key);
        close(sockfd);
        return error;
    }

    recv_motd(sockfd, session_key);
    free_session_key(session_key);
    close(sockfd);
    return 0;
}

int
main(void)
{
    return request_session();
}