ui/vnc-ws.c

   1 /*
   2  * QEMU VNC display driver: Websockets support
   3  *
   4  * Copyright (C) 2010 Joel Martin
   5  * Copyright (C) 2012 Tim Hardeck
   6  *
   7  * This is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This software is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this software; if not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #include "vnc.h"
  22 #include "qemu/main-loop.h"
  23
  24 #ifdef CONFIG_VNC_TLS
  25 #include "qemu/sockets.h"
  26
  27 static int vncws_start_tls_handshake(VncState *vs)
  28 {
  29     int ret = gnutls_handshake(vs->tls.session);
  30
  31     if (ret < 0) {
  32         if (!gnutls_error_is_fatal(ret)) {
  33             VNC_DEBUG("Handshake interrupted (blocking)\n");
  34             if (!gnutls_record_get_direction(vs->tls.session)) {
  35                 qemu_set_fd_handler(vs->csock, vncws_tls_handshake_io,
  36                                     NULL, vs);
  37             } else {
  38                 qemu_set_fd_handler(vs->csock, NULL, vncws_tls_handshake_io,
  39                                     vs);
  40             }
  41             return 0;
  42         }
  43         VNC_DEBUG("Handshake failed %s\n", gnutls_strerror(ret));
  44         vnc_client_error(vs);
  45         return -1;
  46     }
  47
  48     if (vs->vd->tls.x509verify) {
  49         if (vnc_tls_validate_certificate(vs) < 0) {
  50             VNC_DEBUG("Client verification failed\n");
  51             vnc_client_error(vs);
  52             return -1;
  53         } else {
  54             VNC_DEBUG("Client verification passed\n");
  55         }
  56     }
  57
  58     VNC_DEBUG("Handshake done, switching to TLS data mode\n");
  59     qemu_set_fd_handler2(vs->csock, NULL, vncws_handshake_read, NULL, vs);
  60
  61     return 0;
  62 }
  63
  64 void vncws_tls_handshake_io(void *opaque)
  65 {
  66     VncState *vs = (VncState *)opaque;
  67
  68     if (!vs->tls.session) {
  69         VNC_DEBUG("TLS Websocket setup\n");
  70         if (vnc_tls_client_setup(vs, vs->vd->tls.x509cert != NULL) < 0) {
  71             return;
  72         }
  73     }
  74     VNC_DEBUG("Handshake IO continue\n");
  75     vncws_start_tls_handshake(vs);
  76 }
  77 #endif /* CONFIG_VNC_TLS */
  78
  79 void vncws_handshake_read(void *opaque)
  80 {
  81     VncState *vs = opaque;
  82     uint8_t *handshake_end;
  83     long ret;
  84     /* Typical HTTP headers from novnc are 512 bytes, so limiting
  85      * total header size to 4096 is easily enough. */
  86     size_t want = 4096 - vs->ws_input.offset;
  87     buffer_reserve(&vs->ws_input, want);
  88     ret = vnc_client_read_buf(vs, buffer_end(&vs->ws_input), want);
  89
  90     if (!ret) {
  91         if (vs->csock == -1) {
  92             vnc_disconnect_finish(vs);
  93         }
  94         return;
  95     }
  96     vs->ws_input.offset += ret;
  97
  98     handshake_end = (uint8_t *)g_strstr_len((char *)vs->ws_input.buffer,
  99             vs->ws_input.offset, WS_HANDSHAKE_END);
 100     if (handshake_end) {
 101         qemu_set_fd_handler2(vs->csock, NULL, vnc_client_read, NULL, vs);
 102         vncws_process_handshake(vs, vs->ws_input.buffer, vs->ws_input.offset);
 103         buffer_advance(&vs->ws_input, handshake_end - vs->ws_input.buffer +
 104                 strlen(WS_HANDSHAKE_END));
 105     } else if (vs->ws_input.offset >= 4096) {
 106         VNC_DEBUG("End of headers not found in first 4096 bytes\n");
 107         vnc_client_error(vs);
 108     }
 109 }
 110
 111
 112 long vnc_client_read_ws(VncState *vs)
 113 {
 114     int ret, err;
 115     uint8_t *payload;
 116     size_t payload_size, header_size;
 117     VNC_DEBUG("Read websocket %p size %zd offset %zd\n", vs->ws_input.buffer,
 118             vs->ws_input.capacity, vs->ws_input.offset);
 119     buffer_reserve(&vs->ws_input, 4096);
 120     ret = vnc_client_read_buf(vs, buffer_end(&vs->ws_input), 4096);
 121     if (!ret) {
 122         return 0;
 123     }
 124     vs->ws_input.offset += ret;
 125
 126     ret = 0;
 127     /* consume as much of ws_input buffer as possible */
 128     do {
 129         if (vs->ws_payload_remain == 0) {
 130             err = vncws_decode_frame_header(&vs->ws_input,
 131                                             &header_size,
 132                                             &vs->ws_payload_remain,
 133                                             &vs->ws_payload_mask);
 134             if (err <= 0) {
 135                 return err;
 136             }
 137
 138             buffer_advance(&vs->ws_input, header_size);
 139         }
 140         if (vs->ws_payload_remain != 0) {
 141             err = vncws_decode_frame_payload(&vs->ws_input,
 142                                              &vs->ws_payload_remain,
 143                                              &vs->ws_payload_mask,
 144                                              &payload,
 145                                              &payload_size);
 146             if (err < 0) {
 147                 return err;
 148             }
 149             if (err == 0) {
 150                 return ret;
 151             }
 152             ret += err;
 153
 154             buffer_reserve(&vs->input, payload_size);
 155             buffer_append(&vs->input, payload, payload_size);
 156
 157             buffer_advance(&vs->ws_input, payload_size);
 158         }
 159     } while (vs->ws_input.offset > 0);
 160
 161     return ret;
 162 }
 163
 164 long vnc_client_write_ws(VncState *vs)
 165 {
 166     long ret;
 167     VNC_DEBUG("Write WS: Pending output %p size %zd offset %zd\n",
 168               vs->output.buffer, vs->output.capacity, vs->output.offset);
 169     vncws_encode_frame(&vs->ws_output, vs->output.buffer, vs->output.offset);
 170     buffer_reset(&vs->output);
 171     ret = vnc_client_write_buf(vs, vs->ws_output.buffer, vs->ws_output.offset);
 172     if (!ret) {
 173         return 0;
 174     }
 175
 176     buffer_advance(&vs->ws_output, ret);
 177
 178     if (vs->ws_output.offset == 0) {
 179         qemu_set_fd_handler2(vs->csock, NULL, vnc_client_read, NULL, vs);
 180     }
 181
 182     return ret;
 183 }
 184
 185 static char *vncws_extract_handshake_entry(const char *handshake,
 186         size_t handshake_len, const char *name)
 187 {
 188     char *begin, *end, *ret = NULL;
 189     char *line = g_strdup_printf("%s%s: ", WS_HANDSHAKE_DELIM, name);
 190     begin = g_strstr_len(handshake, handshake_len, line);
 191     if (begin != NULL) {
 192         begin += strlen(line);
 193         end = g_strstr_len(begin, handshake_len - (begin - handshake),
 194                 WS_HANDSHAKE_DELIM);
 195         if (end != NULL) {
 196             ret = g_strndup(begin, end - begin);
 197         }
 198     }
 199     g_free(line);
 200     return ret;
 201 }
 202
 203 static void vncws_send_handshake_response(VncState *vs, const char* key)
 204 {
 205     char combined_key[WS_CLIENT_KEY_LEN + WS_GUID_LEN + 1];
 206     unsigned char hash[SHA1_DIGEST_LEN];
 207     size_t hash_size = sizeof(hash);
 208     char *accept = NULL, *response = NULL;
 209     gnutls_datum_t in;
 210     int ret;
 211
 212     g_strlcpy(combined_key, key, WS_CLIENT_KEY_LEN + 1);
 213     g_strlcat(combined_key, WS_GUID, WS_CLIENT_KEY_LEN + WS_GUID_LEN + 1);
 214
 215     /* hash and encode it */
 216     in.data = (void *)combined_key;
 217     in.size = WS_CLIENT_KEY_LEN + WS_GUID_LEN;
 218     ret = gnutls_fingerprint(GNUTLS_DIG_SHA1, &in, hash, &hash_size);
 219     if (ret == GNUTLS_E_SUCCESS && hash_size <= SHA1_DIGEST_LEN) {
 220         accept = g_base64_encode(hash, hash_size);
 221     }
 222     if (accept == NULL) {
 223         VNC_DEBUG("Hashing Websocket combined key failed\n");
 224         vnc_client_error(vs);
 225         return;
 226     }
 227
 228     response = g_strdup_printf(WS_HANDSHAKE, accept);
 229     vnc_client_write_buf(vs, (const uint8_t *)response, strlen(response));
 230
 231     g_free(accept);
 232     g_free(response);
 233
 234     vs->encode_ws = 1;
 235     vnc_init_state(vs);
 236 }
 237
 238 void vncws_process_handshake(VncState *vs, uint8_t *line, size_t size)
 239 {
 240     char *protocols = vncws_extract_handshake_entry((const char *)line, size,
 241             "Sec-WebSocket-Protocol");
 242     char *version = vncws_extract_handshake_entry((const char *)line, size,
 243             "Sec-WebSocket-Version");
 244     char *key = vncws_extract_handshake_entry((const char *)line, size,
 245             "Sec-WebSocket-Key");
 246
 247     if (protocols && version && key
 248             && g_strrstr(protocols, "binary")
 249             && !strcmp(version, WS_SUPPORTED_VERSION)
 250             && strlen(key) == WS_CLIENT_KEY_LEN) {
 251         vncws_send_handshake_response(vs, key);
 252     } else {
 253         VNC_DEBUG("Defective Websockets header or unsupported protocol\n");
 254         vnc_client_error(vs);
 255     }
 256
 257     g_free(protocols);
 258     g_free(version);
 259     g_free(key);
 260 }
 261
 262 void vncws_encode_frame(Buffer *output, const void *payload,
 263         const size_t payload_size)
 264 {
 265     size_t header_size = 0;
 266     unsigned char opcode = WS_OPCODE_BINARY_FRAME;
 267     union {
 268         char buf[WS_HEAD_MAX_LEN];
 269         WsHeader ws;
 270     } header;
 271
 272     if (!payload_size) {
 273         return;
 274     }
 275
 276     header.ws.b0 = 0x80 | (opcode & 0x0f);
 277     if (payload_size <= 125) {
 278         header.ws.b1 = (uint8_t)payload_size;
 279         header_size = 2;
 280     } else if (payload_size < 65536) {
 281         header.ws.b1 = 0x7e;
 282         header.ws.u.s16.l16 = cpu_to_be16((uint16_t)payload_size);
 283         header_size = 4;
 284     } else {
 285         header.ws.b1 = 0x7f;
 286         header.ws.u.s64.l64 = cpu_to_be64(payload_size);
 287         header_size = 10;
 288     }
 289
 290     buffer_reserve(output, header_size + payload_size);
 291     buffer_append(output, header.buf, header_size);
 292     buffer_append(output, payload, payload_size);
 293 }
 294
 295 int vncws_decode_frame_header(Buffer *input,
 296                               size_t *header_size,
 297                               size_t *payload_remain,
 298                               WsMask *payload_mask)
 299 {
 300     unsigned char opcode = 0, fin = 0, has_mask = 0;
 301     size_t payload_len;
 302     WsHeader *header = (WsHeader *)input->buffer;
 303
 304     if (input->offset < WS_HEAD_MIN_LEN + 4) {
 305         /* header not complete */
 306         return 0;
 307     }
 308
 309     fin = (header->b0 & 0x80) >> 7;
 310     opcode = header->b0 & 0x0f;
 311     has_mask = (header->b1 & 0x80) >> 7;
 312     payload_len = header->b1 & 0x7f;
 313
 314     if (opcode == WS_OPCODE_CLOSE) {
 315         /* disconnect */
 316         return -1;
 317     }
 318
 319     /* Websocket frame sanity check:
 320      * * Websocket fragmentation is not supported.
 321      * * All  websockets frames sent by a client have to be masked.
 322      * * Only binary encoding is supported.
 323      */
 324     if (!fin || !has_mask || opcode != WS_OPCODE_BINARY_FRAME) {
 325         VNC_DEBUG("Received faulty/unsupported Websocket frame\n");
 326         return -2;
 327     }
 328
 329     if (payload_len < 126) {
 330         *payload_remain = payload_len;
 331         *header_size = 6;
 332         *payload_mask = header->u.m;
 333     } else if (payload_len == 126 && input->offset >= 8) {
 334         *payload_remain = be16_to_cpu(header->u.s16.l16);
 335         *header_size = 8;
 336         *payload_mask = header->u.s16.m16;
 337     } else if (payload_len == 127 && input->offset >= 14) {
 338         *payload_remain = be64_to_cpu(header->u.s64.l64);
 339         *header_size = 14;
 340         *payload_mask = header->u.s64.m64;
 341     } else {
 342         /* header not complete */
 343         return 0;
 344     }
 345
 346     return 1;
 347 }
 348
 349 int vncws_decode_frame_payload(Buffer *input,
 350                                size_t *payload_remain, WsMask *payload_mask,
 351                                uint8_t **payload, size_t *payload_size)
 352 {
 353     size_t i;
 354     uint32_t *payload32;
 355
 356     *payload = input->buffer;
 357     /* If we aren't at the end of the payload, then drop
 358      * off the last bytes, so we're always multiple of 4
 359      * for purpose of unmasking, except at end of payload
 360      */
 361     if (input->offset < *payload_remain) {
 362         *payload_size = input->offset - (input->offset % 4);
 363     } else {
 364         *payload_size = *payload_remain;
 365     }
 366     if (*payload_size == 0) {
 367         return 0;
 368     }
 369     *payload_remain -= *payload_size;
 370
 371     /* unmask frame */
 372     /* process 1 frame (32 bit op) */
 373     payload32 = (uint32_t *)(*payload);
 374     for (i = 0; i < *payload_size / 4; i++) {
 375         payload32[i] ^= payload_mask->u;
 376     }
 377     /* process the remaining bytes (if any) */
 378     for (i *= 4; i < *payload_size; i++) {
 379         (*payload)[i] ^= payload_mask->c[i % 4];
 380     }
 381
 382     return 1;
 383 }