/*
 * Copyright (C) 2013 Glyptodon LLC
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "config.h"

#include "client.h"
#include "guac_sftp.h"
#include "guac_ssh.h"
#include "sftp.h"
#include "terminal.h"

#ifdef ENABLE_SSH_AGENT
#include "ssh_agent.h"
#endif

#include <libssh2.h>
#include <libssh2_sftp.h>
#include <guacamole/client.h>
#include <guacamole/protocol.h>
#include <guacamole/socket.h>
#include <openssl/err.h>
#include <openssl/ssl.h>

#ifdef LIBSSH2_USES_GCRYPT
#include <gcrypt.h>
#endif

#include <errno.h>
#include <netdb.h>
#include <netinet/in.h>
#include <pthread.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <sys/time.h>

/**
 * Produces a new user object containing a username and password or private
 * key, prompting the user as necessary to obtain that information.
 *
 * @param client
 *     The Guacamole client containing any existing user data, as well as the
 *     terminal to use when prompting the user.
 *
 * @return
 *     A new user object containing the user's username and other credentials.
 */
static guac_common_ssh_user* guac_ssh_get_user(guac_client* client) {

    ssh_guac_client_data* client_data = (ssh_guac_client_data*) client->data;

    guac_common_ssh_user* user;

    /* Get username */
    if (client_data->username[0] == 0)
        guac_terminal_prompt(client_data->term, "Login as: ",
                client_data->username, sizeof(client_data->username), true);

    /* Create user object from username */
    user = guac_common_ssh_create_user(client_data->username);

    /* If key specified, import */
    if (client_data->key_base64[0] != 0) {

        guac_client_log(client, GUAC_LOG_DEBUG,
                "Attempting private key import (WITHOUT passphrase)");

        /* Attempt to read key without passphrase */
        if (guac_common_ssh_user_import_key(user,
                    client_data->key_base64, NULL)) {

            /* Log failure of initial attempt */
            guac_client_log(client, GUAC_LOG_DEBUG,
                    "Initial import failed: %s",
                    guac_common_ssh_key_error());
  
            guac_client_log(client, GUAC_LOG_DEBUG,
                    "Re-attempting private key import (WITH passphrase)");

            /* Prompt for passphrase if missing */
            if (client_data->key_passphrase[0] == 0)
                guac_terminal_prompt(client_data->term, "Key passphrase: ",
                        client_data->key_passphrase,
                        sizeof(client_data->key_passphrase), false);

            /* Reattempt import with passphrase */
            if (guac_common_ssh_user_import_key(user,
                        client_data->key_base64,
                        client_data->key_passphrase)) {

                /* If still failing, give up */
                guac_client_abort(client,
                        GUAC_PROTOCOL_STATUS_CLIENT_UNAUTHORIZED,
                        "Auth key import failed: %s",
                        guac_common_ssh_key_error());

                guac_common_ssh_destroy_user(user);
                return NULL;

            }

        } /* end decrypt key with passphrase */

        /* Success */
        guac_client_log(client, GUAC_LOG_INFO,
                "Auth key successfully imported.");

    } /* end if key given */

    /* Otherwise, use password */
    else {

        /* Get password if not provided */
        if (client_data->password[0] == 0)
            guac_terminal_prompt(client_data->term, "Password: ",
                    client_data->password, sizeof(client_data->password),
                    false);

        /* Set provided password */
        guac_common_ssh_user_set_password(user, client_data->password);

    }

    /* Clear screen of any prompts */
    guac_terminal_printf(client_data->term, "\x1B[H\x1B[J");

    return user;

}

void* ssh_input_thread(void* data) {

    guac_client* client = (guac_client*) data;
    ssh_guac_client_data* client_data = (ssh_guac_client_data*) client->data;

    char buffer[8192];
    int bytes_read;

    /* Write all data read */
    while ((bytes_read = guac_terminal_read_stdin(client_data->term, buffer, sizeof(buffer))) > 0) {
        pthread_mutex_lock(&(client_data->term_channel_lock));
        libssh2_channel_write(client_data->term_channel, buffer, bytes_read);
        pthread_mutex_unlock(&(client_data->term_channel_lock));
    }

    return NULL;

}

void* ssh_client_thread(void* data) {

    guac_client* client = (guac_client*) data;
    ssh_guac_client_data* client_data = (ssh_guac_client_data*) client->data;

    guac_socket* socket = client->socket;
    char buffer[8192];

    pthread_t input_thread;

    /* Init SSH base libraries */
    if (guac_common_ssh_init(client))
        return NULL;

    /* Get user and credentials */
    client_data->user = guac_ssh_get_user(client);

    /* Send new name */
    char name[1024];
    snprintf(name, sizeof(name)-1, "%s@%s",
            client_data->username, client_data->hostname);
    guac_protocol_send_name(socket, name);

    /* Open SSH session */
    client_data->session = guac_common_ssh_create_session(client,
            client_data->hostname, client_data->port, client_data->user);
    if (client_data->session == NULL) {
        /* Already aborted within guac_common_ssh_create_session() */
        return NULL;
    }

    pthread_mutex_init(&client_data->term_channel_lock, NULL);

    /* Open channel for terminal */
    client_data->term_channel =
        libssh2_channel_open_session(client_data->session->session);
    if (client_data->term_channel == NULL) {
        guac_client_abort(client, GUAC_PROTOCOL_STATUS_UPSTREAM_ERROR,
                "Unable to open terminal channel.");
        return NULL;
    }

#ifdef ENABLE_SSH_AGENT
    /* Start SSH agent forwarding, if enabled */
    if (client_data->enable_agent) {
        libssh2_session_callback_set(client_data->session,
                LIBSSH2_CALLBACK_AUTH_AGENT, (void*) ssh_auth_agent_callback);

        /* Request agent forwarding */
        if (libssh2_channel_request_auth_agent(client_data->term_channel))
            guac_client_log(client, GUAC_LOG_ERROR, "Agent forwarding request failed");
        else
            guac_client_log(client, GUAC_LOG_INFO, "Agent forwarding enabled.");
    }

    client_data->auth_agent = NULL;
#endif

    /* Start SFTP session as well, if enabled */
    if (client_data->enable_sftp) {

        /* Create SSH session specific for SFTP */
        guac_client_log(client, GUAC_LOG_DEBUG, "Reconnecting for SFTP...");
        client_data->sftp_session =
            guac_common_ssh_create_session(client, client_data->hostname,
                    client_data->port, client_data->user);
        if (client_data->sftp_session == NULL) {
            /* Already aborted within guac_common_ssh_create_session() */
            return NULL;
        }

        /* Request SFTP */
        client_data->sftp_filesystem =
            guac_common_ssh_create_sftp_filesystem(
                    client_data->sftp_session, "/");

        /* Set generic (non-filesystem) file upload handler */
        client->file_handler = guac_sftp_file_handler;

        /* Init handlers for Guacamole-specific console codes */
        client_data->term->upload_path_handler = guac_sftp_set_upload_path;
        client_data->term->file_download_handler = guac_sftp_download_file;

        guac_client_log(client, GUAC_LOG_DEBUG, "SFTP session initialized");

    }

    /* Request PTY */
    if (libssh2_channel_request_pty_ex(client_data->term_channel, "linux", sizeof("linux")-1, NULL, 0,
            client_data->term->term_width, client_data->term->term_height, 0, 0)) {
        guac_client_abort(client, GUAC_PROTOCOL_STATUS_UPSTREAM_ERROR, "Unable to allocate PTY.");
        return NULL;
    }

    /* If a command is specified, run that instead of a shell */
    if (client_data->command != NULL) {
        if (libssh2_channel_exec(client_data->term_channel, client_data->command)) {
            guac_client_abort(client, GUAC_PROTOCOL_STATUS_UPSTREAM_ERROR,
                    "Unable to execute command.");
            return NULL;
        }
    }

    /* Otherwise, request a shell */
    else if (libssh2_channel_shell(client_data->term_channel)) {
        guac_client_abort(client, GUAC_PROTOCOL_STATUS_UPSTREAM_ERROR,
                "Unable to associate shell with PTY.");
        return NULL;
    }

    /* Logged in */
    guac_client_log(client, GUAC_LOG_INFO, "SSH connection successful.");

    /* Start input thread */
    if (pthread_create(&(input_thread), NULL, ssh_input_thread, (void*) client)) {
        guac_client_abort(client, GUAC_PROTOCOL_STATUS_SERVER_ERROR, "Unable to start input thread");
        return NULL;
    }

    /* Set non-blocking */
    libssh2_session_set_blocking(client_data->session->session, 0);

    /* While data available, write to terminal */
    int bytes_read = 0;
    for (;;) {

        /* Track total amount of data read */
        int total_read = 0;

        pthread_mutex_lock(&(client_data->term_channel_lock));

        /* Stop reading at EOF */
        if (libssh2_channel_eof(client_data->term_channel)) {
            pthread_mutex_unlock(&(client_data->term_channel_lock));
            break;
        }

        /* Read terminal data */
        bytes_read = libssh2_channel_read(client_data->term_channel,
                buffer, sizeof(buffer));

        pthread_mutex_unlock(&(client_data->term_channel_lock));

        /* Attempt to write data received. Exit on failure. */
        if (bytes_read > 0) {
            int written = guac_terminal_write_stdout(client_data->term, buffer, bytes_read);
            if (written < 0)
                break;

            total_read += bytes_read;
        }

        else if (bytes_read < 0 && bytes_read != LIBSSH2_ERROR_EAGAIN)
            break;

#ifdef ENABLE_SSH_AGENT
        /* If agent open, handle any agent packets */
        if (client_data->auth_agent != NULL) {
            bytes_read = ssh_auth_agent_read(client_data->auth_agent);
            if (bytes_read > 0)
                total_read += bytes_read;
            else if (bytes_read < 0 && bytes_read != LIBSSH2_ERROR_EAGAIN)
                client_data->auth_agent = NULL;
        }
#endif

        /* Wait for more data if reads turn up empty */
        if (total_read == 0) {
            fd_set fds;
            struct timeval timeout;

            FD_ZERO(&fds);
            FD_SET(client_data->session->fd, &fds);

            /* Wait for one second */
            timeout.tv_sec = 1;
            timeout.tv_usec = 0;

            if (select(client_data->session->fd + 1, &fds,
                        NULL, NULL, &timeout) < 0)
                break;
        }

    }

    /* Kill client and Wait for input thread to die */
    guac_client_stop(client);
    pthread_join(input_thread, NULL);

    pthread_mutex_destroy(&client_data->term_channel_lock);

    guac_client_log(client, GUAC_LOG_INFO, "SSH connection ended.");
    return NULL;

}