/*
 * 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 <sys/socket.h>
#include <netinet/in.h>
#include <ostp/net/stpsession.h>
#include <ostp/net/param.h>
#include <ostp/crypto/ecdh.h>
#include <ostp/defs.h>
#include <ostp/session.h>
#include <ostp/otconfig.h>
#include <arpa/inet.h>
#include <termios.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#define OSTP_PORT 5352

#if DIAGNOSTIC
#define LOG(...) printf("libostp: %s", __VA_ARGS__)
#else
#define LOG(...) (void)0
#endif

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 const char *auth_codestr[] = {
    [AUTH_SUCCESS] = "successful auth",
    [AUTH_BAD_PW] = "bad username or password"
};

static int
send_auth(int sockfd, const unsigned char *session_key)
{
    struct session_auth auth;
    struct termios oldt, newt;
    int c, index = 0;
    int error;

    printf("** Please authenticate yourself **\n");
    printf("Username: ");

    /* Fetch username and clean it up */
    fgets(auth.username, sizeof(auth.username), stdin);
    auth.username[strcspn(auth.username, "\n")] = '\0';

    /* Hide input */
    tcgetattr(STDIN_FILENO, &oldt);
    newt = oldt;
    newt.c_lflag &= ~(ECHO | ICANON);
    tcsetattr(STDIN_FILENO, TCSANOW, &newt);

    printf("Password: ");
    while (index < (sizeof(auth.password) - 1)) {
        c = getchar();

        if (c == '\n') {
            printf("\n");
            break;
        }

        if (c == 127 || c == '\b') {
            if (index > 0) {
                auth.password[index] = '\0';
                index--;
                printf("\b \b");
            }
        } else {
            auth.password[index++] = c;
            printf("*");
        }
    }

    auth.code = 0;
    auth.password[index] = '\0';
    tcsetattr(STDIN_FILENO, TCSANOW, &oldt);

    /* Send frame with session auth */
    error = send_frame(sockfd, &auth, sizeof(auth), session_key);
    if (error < 0) {
        printf("Failed to send user authentication\n");
        return error;
    }

    /* Try to get server reply */
    error = recv_frame(sockfd, sizeof(auth), session_key, &auth);
    if (error < 0) {
        LOG("Failed to get user authentication ACK from server\n");
        return error;
    }

    /* Did it fail? */
    if (auth.code != AUTH_SUCCESS) {
        LOG("Failed to authenticate, server says: %s\n",
            auth_codestr[auth.code]);
        return -1;
    }

    return 0;
}

static int
client_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) {
            LOG("** Negotiation success\n");
            break;
        }

        LOG("** Arbitration needed, server says: %s\n", pap_codestr[pap.code]);
        LOG("** 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) - 1, session_key, buf)) < 0) {
        printf("Failed to recv MOTD...\n");
        return;
    }

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

int
session_new(const char *host, struct ostp_session *res)
{
    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;

    res->session_key = NULL;
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = inet_addr(host);
    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) {
        LOG("Failed to connect!\n");
        close(sockfd);
        return error;
    }

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

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

    /*
     * Setup the session request and add our public
     * key to it. We also assume user authentication.
     */
    stp_sq.options = SESSION_REQ_USER;
    memcpy(stp_sq.pubkey, keypair.pubkey, sizeof(stp_sq.pubkey));

    LOG("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) {
        LOG("Connection closed by peer\n");
        close(sockfd);
        return 0;
    }

    LOG("Got public key from server\n");
    LOG("Deriving session key...\n");
    gen_session_key(keypair.privkey, serv_pubkey, &session_key);

    /* User authentication occurs before sending SPWs */
    if ((error = send_auth(sockfd, session_key)) < 0) {
        return error;
    }

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

    recv_motd(sockfd, session_key);
    res->sockfd = sockfd;
    res->session_key = session_key;
    return 0;
}

int
session_close(struct ostp_session *session)
{
    if (session->session_key == NULL) {
        free_session_key(session->session_key);
    }
    close(session->sockfd);
    return 0;
}

int
session_send(void *data, uint16_t len, const struct ostp_session *session)
{
    return send_frame(session->sockfd, data, len, session->session_key);
}

int
session_recv(void *buf, uint16_t len, const struct ostp_session *session)
{
    return recv_frame(session->sockfd, len, session->session_key, buf);
}