ttssh2/ttxssh/x11util.c

/*
Copyright (c) 1998-2001, Robert O'Callahan
All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list of
conditions and the following disclaimer.

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.

The name of Robert O'Callahan may not 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 REGENTS 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 "x11util.h"

#include <openssl/rand.h>
#include "util.h"
#include <stdlib.h>

typedef struct {
        PTInstVar pvar;
        X11AuthData FAR *auth_data;

        unsigned char FAR *init_buf;
        int init_buf_len;
        int init_data_len;
} X11UnspoofingFilterClosure;

void X11_get_DISPLAY_info(char FAR * name_buf, int name_buf_len,
                          int FAR * port)
{
        char FAR *DISPLAY = getenv("DISPLAY");

        strncpy_s(name_buf, name_buf_len, "localhost", _TRUNCATE);
        *port = 6000;

        if (DISPLAY != NULL) {
                int i;

                for (i = 0; DISPLAY[i] != 0 && DISPLAY[i] != ':'; i++) {
                }

                if (i > 0) {
                        char c = DISPLAY[i];
                        DISPLAY[i] = 0;
                        strncpy_s(name_buf, name_buf_len, DISPLAY, _TRUNCATE);
                        DISPLAY[i] = c;
                }

                if (DISPLAY[i] == ':') {
                        *port = atoi(DISPLAY + i + 1) + 6000;
                }
        }
}

X11AuthData FAR *X11_load_local_auth_data(int screen_num)
{
        X11AuthData FAR *auth_data =
                (X11AuthData FAR *) malloc(sizeof(X11AuthData));
        char FAR *local_auth_data_str;

        auth_data->local_protocol = getenv("TTSSH_XAUTH_PROTOCOL_NAME");

        local_auth_data_str = getenv("TTSSH_XAUTH_PROTOCOL_DATA");
        if (local_auth_data_str == NULL) {
                auth_data->local_data_len = 0;
                auth_data->local_data = NULL;
        } else {
                int str_len = strlen(local_auth_data_str);
                int i;

                auth_data->local_data_len = (str_len + 1) / 2;
                auth_data->local_data = malloc(auth_data->local_data_len);

                if (auth_data->local_data_len * 2 > str_len) {
                        char buf[2] = { local_auth_data_str[0], 0 };

                        auth_data->local_data[0] =
                                (unsigned char) strtol(buf, NULL, 16);
                        i = 1;
                } else {
                        i = 0;
                }

                for (; i < str_len; i += 2) {
                        char buf[3] =
                                { local_auth_data_str[i], local_auth_data_str[i + 1], 0 };

                        auth_data->local_data[(i + 1) / 2] =
                                (unsigned char) strtol(buf, NULL, 16);
                }
        }

        auth_data->spoofed_protocol = _strdup("MIT-MAGIC-COOKIE-1");
        auth_data->spoofed_data_len = 16;
        auth_data->spoofed_data = malloc(auth_data->spoofed_data_len);
        RAND_bytes(auth_data->spoofed_data, auth_data->spoofed_data_len);

        return auth_data;
}

void X11_dispose_auth_data(X11AuthData FAR * auth_data)
{
        memset(auth_data->local_data, 0, auth_data->local_data_len);
        free(auth_data->local_data);
        free(auth_data->spoofed_protocol);
        memset(auth_data->spoofed_data, 0, auth_data->spoofed_data_len);
        free(auth_data->spoofed_data);
        free(auth_data);
}

void *X11_init_unspoofing_filter(PTInstVar pvar,
                                 X11AuthData FAR * auth_data)
{
        X11UnspoofingFilterClosure FAR *closure =
                malloc(sizeof(X11UnspoofingFilterClosure));

        closure->pvar = pvar;
        closure->auth_data = auth_data;

        closure->init_data_len = 0;
        buf_create(&closure->init_buf, &closure->init_buf_len);

        return closure;
}

#define MERGE_NEED_MORE     0
#define MERGE_GOT_GOOD_DATA 1
#define MERGE_GOT_BAD_DATA  2

static int merge_into_X11_init_packet(X11UnspoofingFilterClosure FAR *
                                      closure, int length,
                                      unsigned char FAR * buf)
{
        buf_ensure_size_growing(&closure->init_buf, &closure->init_buf_len,
                                closure->init_data_len + length);
        memcpy(closure->init_buf + closure->init_data_len, buf, length);
        closure->init_data_len += length;

        if (closure->init_data_len < 12) {
                return MERGE_NEED_MORE;
        } else {
                int name_len;
                int data_len;
                int padded_name_len;
                int padded_data_len;

                switch (closure->init_buf[0]) {
                case 0x42:                              /* MSB first */
                        name_len = (closure->init_buf[6] << 8) | closure->init_buf[7];
                        data_len = (closure->init_buf[8] << 8) | closure->init_buf[9];
                        break;
                case 0x6C:                              /* LSB first */
                        name_len = (closure->init_buf[7] << 8) | closure->init_buf[6];
                        data_len = (closure->init_buf[9] << 8) | closure->init_buf[8];
                        break;
                default:
                        return MERGE_GOT_BAD_DATA;
                }

                padded_name_len = (name_len + 3) & ~0x3;
                padded_data_len = (data_len + 3) & ~0x3;

                if (closure->init_data_len <
                    12 + padded_name_len + padded_data_len) {
                        return MERGE_NEED_MORE;
                } else if (name_len ==
                           (int) strlen(closure->auth_data->spoofed_protocol)
                           && memcmp(closure->init_buf + 12,
                                     closure->auth_data->spoofed_protocol,
                                     name_len) == 0
                           && data_len == closure->auth_data->spoofed_data_len
                           && memcmp(closure->init_buf + 12 + padded_name_len,
                                     closure->auth_data->spoofed_data,
                                     data_len) == 0) {
                        return MERGE_GOT_GOOD_DATA;
                } else {
                        return MERGE_GOT_BAD_DATA;
                }
        }
}

static void insert_real_X11_auth_data(X11UnspoofingFilterClosure FAR *
                                      closure, int FAR * length,
                                      unsigned char FAR * FAR * buf)
{
        int name_len = closure->auth_data->local_protocol == NULL
                ? 0 : strlen(closure->auth_data->local_protocol);
        int data_len = closure->auth_data->local_data_len;
        int padded_name_len = (name_len + 3) & ~0x3;
        int padded_data_len = (data_len + 3) & ~0x3;

        *length = 12 + padded_name_len + padded_data_len;
        buf_ensure_size(&closure->init_buf, &closure->init_buf_len, *length);
        *buf = closure->init_buf;

        switch (closure->init_buf[0]) {
        case 0x42:                                      /* MSB first */
                closure->init_buf[6] = name_len >> 8;
                closure->init_buf[7] = name_len & 0xFF;
                closure->init_buf[8] = data_len >> 8;
                closure->init_buf[9] = data_len & 0xFF;
                break;
        case 0x6C:                                      /* LSB first */
                closure->init_buf[7] = name_len >> 8;
                closure->init_buf[6] = name_len & 0xFF;
                closure->init_buf[9] = data_len >> 8;
                closure->init_buf[8] = data_len & 0xFF;
                break;
        }

        memcpy(*buf + 12, closure->auth_data->local_protocol, name_len);
        memcpy(*buf + 12 + padded_name_len, closure->auth_data->local_data,
               data_len);
}

int X11_unspoofing_filter(void FAR * void_closure, int direction,
                          int FAR * length, unsigned char FAR * FAR * buf)
{
        X11UnspoofingFilterClosure FAR *closure =
                (X11UnspoofingFilterClosure FAR *) void_closure;

        if (length == NULL) {
                buf_destroy(&closure->init_buf, &closure->init_buf_len);
                free(closure);
                return FWD_FILTER_REMOVE;
        } else if (direction == FWD_FILTER_FROM_SERVER) {
                switch (merge_into_X11_init_packet(closure, *length, *buf)) {
                case MERGE_NEED_MORE:
                        *length = 0;
                        return FWD_FILTER_RETAIN;
                case MERGE_GOT_GOOD_DATA:
                        insert_real_X11_auth_data(closure, length, buf);
                        return FWD_FILTER_REMOVE;
                default:
                case MERGE_GOT_BAD_DATA:
                        UTIL_get_lang_msg("MSG_X_AUTH_ERROR", closure->pvar,
                                          "Remote X application sent incorrect authentication data.\n"
                                          "Its X session is being cancelled.");
                        notify_nonfatal_error(closure->pvar, closure->pvar->ts->UIMsg);
                        *length = 0;
                        return FWD_FILTER_CLOSECHANNEL;
                }
        } else {
                return FWD_FILTER_RETAIN;
        }
}