epan/dissectors/packet-blip.c

   1 /* packet-blip.c
   2  *
   3  * BLIP protocol for Couchbase Lite <-> Sync Gateway 2.0+ Replication
   4  *
   5  * Spec: https://github.com/couchbaselabs/BLIP-Cpp/blob/master/docs/BLIP%20Protocol.md
   6  *
   7  * Copyright 2018, Traun Leyden <traun@couchbase.com>
   8  * Copyright 2018, Jim Borden <jim.borden@couchbase.com>
   9  *
  10  * Wireshark - Network traffic analyzer
  11  * By Gerald Combs <gerald@wireshark.org>
  12  * Copyright 1998 Gerald Combs
  13  *
  14  * SPDX-License-Identifier: GPL-2.0-or-later
  15  */
  16
  17 #include "config.h"
  18
  19 #include <epan/packet.h>
  20 #include <epan/conversation.h>
  21 #include <epan/prefs.h>
  22 #include <epan/expert.h>
  23 #include <epan/strutil.h>
  24 #include "proto_data.h"
  25
  26 #if defined(HAVE_ZLIB) && !defined(HAVE_ZLIBNG)
  27 #define ZLIB_PREFIX(x) x
  28 #include <zlib.h>
  29 typedef z_stream zlib_stream;
  30 #endif /* HAVE_ZLIB */
  31
  32 #ifdef HAVE_ZLIBNG
  33 #define ZLIB_PREFIX(x) zng_ ## x
  34 #include <zlib-ng.h>
  35 typedef zng_stream zlib_stream;
  36 #endif /* HAVE_ZLIBNG */
  37 void proto_reg_handoff_blip(void);
  38 void proto_register_blip(void);
  39
  40 #define BLIP_BODY_CHECKSUM_SIZE 4
  41
  42 // blip_conversation_entry_t is metadata that the blip dissector associates w/ each wireshark conversation
  43 typedef struct {
  44
  45         // Keep track of the largest frame number seen.  This is useful for determining whether
  46         // this is the first frame in a request message or not.
  47
  48         // key: msgtype:srcport:destport:messagenumber -> value: frame number for the _first_ frame in this request message
  49         // Example: "MSG:23243:4984:56" -> 12
  50         // which means: "the first frame for blip message number 56, originating from source port 23243,
  51         //              ... and going to port 4984 for message type = MSG occurred in wireshark packet #12"
  52         wmem_map_t *blip_requests;
  53
  54 #if defined(HAVE_ZLIB) || defined(HAVE_ZLIBNG)
  55         // The streams used to decode a particular connection.  These are per direction and per connection.
  56         wmem_map_t *decompress_streams;
  57 #endif
  58 } blip_conversation_entry_t;
  59
  60 #if defined (HAVE_ZLIB) || defined (HAVE_ZLIBNG)
  61 typedef enum
  62 {
  63         no_error = 0,
  64         zlib_error,
  65         overflow_error
  66 } decompress_error_t;
  67
  68 typedef struct
  69 {
  70         decompress_error_t domain;
  71         int code;
  72         size_t size;
  73         void* buf;
  74 } decompress_result_t;
  75 #endif
  76
  77 // File level variables
  78 static dissector_handle_t blip_handle;
  79 static int proto_blip;
  80 static int hf_blip_message_number;
  81 static int hf_blip_frame_flags;
  82 static int hf_blip_properties_length;
  83 static int hf_blip_properties;
  84 static int hf_blip_message_body;
  85 static int hf_blip_ack_size;
  86 static int hf_blip_checksum;
  87
  88 static int ett_blip;
  89
  90 static expert_field ei_blip_decompress_buffer_error;
  91
  92 // Compressed = 0x08
  93 // Urgent         = 0x10
  94 // NoReply        = 0x20
  95 // MoreComing = 0x40
  96 // In ascending order so that a binary search will be used as per the
  97 // README.dissector
  98 static const value_string flag_combos[] = {
  99         { 0x00, "None" },
 100         { 0x08, "Compressed" },
 101         { 0x10, "Urgent" },
 102         { 0x10|0x08, "Compressed|Urgent" },
 103         { 0x20, "NoReply" },
 104         { 0x20|0x08, "Compressed|NoReply" },
 105         { 0x20|0x10, "Urgent|NoReply" },
 106         { 0x20|0x10|0x08, "Compressed|Urgent|NoReply" },
 107         { 0x40, "MoreComing" },
 108         { 0x40|0x08, "Compressed|MoreComing" },
 109         { 0x40|0x10, "Urgent|MoreComing" },
 110         { 0x40|0x10|0x08, "Compressed|Urgent|MoreComing" },
 111         { 0x40|0x20, "NoReply|MoreComing" },
 112         { 0x40|0x20|0x08, "Compressed|NoReply|MoreComing" },
 113         { 0x40|0x20|0x10, "Urgent|NoReply|MoreComing" },
 114         { 0x40|0x20|0x10|0x08, "Compressed|Urgent|NoReply|MoreComing" },
 115         { 0, NULL }
 116 };
 117
 118 static value_string_ext flag_combos_ext = VALUE_STRING_EXT_INIT(flag_combos);
 119
 120 static const val64_string msg_types[] = {
 121         { 0x00ll, "MSG" },
 122         { 0x01ll, "RPY" },
 123         { 0x02ll, "ERR" },
 124         { 0x04ll, "ACKMSG" },
 125         { 0x05ll, "ACKRPY" },
 126         { 0, NULL }
 127 };
 128
 129 // Preferences
 130 #if defined (HAVE_ZLIB) || defined (HAVE_ZLIBNG)
 131 static unsigned max_uncompressed_size = 64; // Max uncompressed body size in Kb
 132 #endif
 133
 134 // MSG =        0x00
 135 // RPY =        0x01
 136 // ERR =        0x02
 137 // ACKMSG = 0x04
 138 // ACKRPY = 0x05
 139 static const char*
 140 get_message_type(uint64_t value_frame_flags)
 141 {
 142         // Mask out the least significant bits: 0000 0111
 143         uint64_t type_mask_val = (0x07ll & value_frame_flags);
 144         return val64_to_str_const(type_mask_val, msg_types, "???");
 145 }
 146
 147 static bool
 148 is_ack_message(uint64_t value_frame_flags) {
 149         // Note, even though this is a 64-bit int, only the least significant byte has meaningful information,
 150         // since frame flags all fit into one byte at the time this code was written.
 151
 152         // Mask out the least significant bits: 0000 0111
 153         uint64_t type_mask_val = (0x07ll & value_frame_flags);
 154
 155         // ACKMSG
 156         if (type_mask_val == 0x04ll) {
 157                 return true;
 158         }
 159
 160         // ACKRPY
 161         if (type_mask_val == 0x05ll) {
 162                 return true;
 163         }
 164
 165         return false;
 166 }
 167
 168 static bool
 169 is_compressed(uint64_t value_frame_flags)
 170 {
 171         // Note, even though this is a 64-bit int, only the least significant byte has meaningful information,
 172         // since frame flags all fit into one byte at the time this code was written.
 173
 174         if ((0x08ll & value_frame_flags) == 0x08ll) {
 175                 return true;
 176         }
 177
 178         return false;
 179
 180 }
 181
 182 static char*
 183 message_hash_key_convo(packet_info *pinfo,
 184                                   uint64_t value_frame_flags,
 185                                   uint64_t value_message_num)
 186 {
 187         // Derive the hash key to use
 188         // msgtype:srcport:destport:messagenum
 189
 190         const char *msg_type = get_message_type(value_frame_flags);
 191         char *hash_key = wmem_strdup_printf(pinfo->pool, "%s:%u:%u:%" PRIu64,
 192                         msg_type, pinfo->srcport, pinfo->destport, value_message_num);
 193
 194         return hash_key;
 195 }
 196
 197 // Finds out whether this is the first blip frame in the blip message (which can consist of a series of frames).
 198 // If it is, updates the conversation_entry_ptr->blip_requests hash to record the pinfo->num (wireshark packet number)
 199 static bool
 200 is_first_frame_in_msg(blip_conversation_entry_t *conversation_entry_ptr, packet_info *pinfo,
 201                                           uint64_t value_frame_flags, uint64_t value_message_num) {
 202
 203         bool first_frame_in_msg = true;
 204
 205         // Temporary pool for the lookup hash_key.      Will get duplicated on the file_scope() pool if needed to be
 206         // stored in the hashtable.
 207         char *hash_key = message_hash_key_convo(pinfo, value_frame_flags, value_message_num);
 208         unsigned* first_frame_number_for_msg = (unsigned*)wmem_map_lookup(conversation_entry_ptr->blip_requests, (void *) hash_key);
 209
 210         if (first_frame_number_for_msg != NULL) {
 211                 if (GPOINTER_TO_UINT(first_frame_number_for_msg) != pinfo->num) {
 212                         first_frame_in_msg = false;
 213                 }
 214         } else {
 215                 // If storing the key in the hashmap, re-allocate it with the file_scope() allocator
 216                 char *hash_key_copy = wmem_strdup(wmem_file_scope(), hash_key);
 217
 218                 wmem_map_insert(conversation_entry_ptr->blip_requests, (void *) hash_key_copy, GUINT_TO_POINTER(pinfo->num));
 219         }
 220
 221         return first_frame_in_msg;
 222 }
 223
 224 static int
 225 handle_ack_message(tvbuff_t *tvb, _U_ packet_info *pinfo, proto_tree *blip_tree, int offset, _U_ uint64_t value_frame_flags)
 226 {
 227         // This gets the number of ack bytes received  as a var int in order to find out how much to bump
 228         // the offset for the next proto_tree item
 229         uint64_t value_ack_size;
 230         unsigned varint_ack_size_length = tvb_get_varint(
 231                         tvb,
 232                         offset,
 233                         FT_VARINT_MAX_LEN,
 234                         &value_ack_size,
 235                         ENC_VARINT_PROTOBUF);
 236
 237         proto_tree_add_item(blip_tree, hf_blip_ack_size, tvb, offset, varint_ack_size_length, ENC_VARINT_PROTOBUF);
 238
 239         return tvb_captured_length(tvb);
 240 }
 241
 242 static blip_conversation_entry_t*
 243 get_blip_conversation(packet_info* pinfo)
 244 {
 245         // Create a new conversation if needed and associate the blip_conversation_entry_t with it
 246         // Adapted from sample code in doc/README.dissector
 247         conversation_t *conversation;
 248         conversation = find_or_create_conversation(pinfo);
 249         blip_conversation_entry_t *conversation_entry_ptr = (blip_conversation_entry_t*)conversation_get_proto_data(conversation, proto_blip);
 250         if (conversation_entry_ptr == NULL) {
 251
 252                 // create a new blip_conversation_entry_t
 253                 conversation_entry_ptr = wmem_new(wmem_file_scope(), blip_conversation_entry_t);
 254
 255                 // create a new hash map and save a reference in blip_conversation_entry_t
 256                 conversation_entry_ptr->blip_requests = wmem_map_new(wmem_file_scope(), g_str_hash, g_str_equal);
 257 #if defined(HAVE_ZLIB) || defined(HAVE_ZLIBNG)
 258                 conversation_entry_ptr->decompress_streams = wmem_map_new(wmem_file_scope(), g_direct_hash, g_direct_equal);
 259 #endif
 260                 conversation_add_proto_data(conversation, proto_blip, conversation_entry_ptr);
 261         }
 262
 263         return conversation_entry_ptr;
 264 }
 265
 266 #if defined (HAVE_ZLIB) || defined (HAVE_ZLIBNG)
 267 static bool
 268 z_stream_destroy_cb(wmem_allocator_t *allocator _U_, wmem_cb_event_t event _U_, void *user_data)
 269 {
 270         zlib_stream*decompress_stream = (zlib_stream*)user_data;
 271         ZLIB_PREFIX(inflateEnd)(decompress_stream);
 272         return false;
 273 }
 274
 275 static zlib_stream*
 276 get_decompress_stream(packet_info* pinfo)
 277 {
 278         const blip_conversation_entry_t* blip_convo = get_blip_conversation(pinfo);
 279
 280         // Store compression state per srcport/destport.
 281         uint32_t hash_key = (pinfo->srcport << 16) | pinfo->destport;
 282         zlib_stream* decompress_stream = (zlib_stream*)wmem_map_lookup(blip_convo->decompress_streams, GUINT_TO_POINTER(hash_key));
 283         if(decompress_stream) {
 284                 return decompress_stream;
 285         }
 286
 287         decompress_stream = wmem_new0(wmem_file_scope(), zlib_stream);
 288         wmem_map_insert(blip_convo->decompress_streams, GUINT_TO_POINTER(hash_key), decompress_stream);
 289         wmem_register_callback(wmem_file_scope(), z_stream_destroy_cb, decompress_stream);
 290
 291         return decompress_stream;
 292 }
 293
 294 static tvbuff_t*
 295 decompress(packet_info* pinfo, proto_tree* tree, tvbuff_t* tvb, int offset, int length)
 296 {
 297         if(PINFO_FD_VISITED(pinfo)) {
 298                 const decompress_result_t* saved_data = (decompress_result_t *)p_get_proto_data(wmem_file_scope(), pinfo, proto_blip, 0);
 299                 if(!saved_data) {
 300                         proto_tree_add_string(tree, hf_blip_message_body, tvb, offset, tvb_reported_length_remaining(tvb, offset), "<Error decompressing data>");
 301                         return NULL;
 302                 }
 303
 304                 if(saved_data->domain) {
 305                         proto_item* field = proto_tree_add_string(tree, hf_blip_message_body, tvb, offset, tvb_reported_length_remaining(tvb, offset), "<Error decompressing data>");
 306                         if(saved_data->domain == zlib_error) {
 307                                 expert_add_info_format(pinfo, field, &ei_blip_decompress_buffer_error, "Unable to decompress message, got zlib error %d", saved_data->code);
 308                         } else {
 309                                 expert_add_info_format(pinfo, field, &ei_blip_decompress_buffer_error, "Unable to decompress message, buffer too small (%u Kb).  Please adjust in settings.", max_uncompressed_size);
 310                         }
 311
 312                         return NULL;
 313                 } else {
 314                         tvbuff_t* decompressedChild = tvb_new_child_real_data(tvb, (uint8_t *)saved_data->buf,
 315                                 (int)saved_data->size, (int)saved_data->size);
 316                         add_new_data_source(pinfo, decompressedChild, "Decompressed Payload");
 317                         return decompressedChild;
 318                 }
 319         }
 320
 321         static bool size_overflow = false;
 322         const uint8_t* buf = tvb_get_ptr(tvb, offset, length);
 323         zlib_stream* decompress_stream = get_decompress_stream(pinfo);
 324         static Byte trailer[4] = { 0x00, 0x00, 0xff, 0xff };
 325         if(!decompress_stream->next_out) {
 326                 decompress_stream->zalloc = 0;
 327                 decompress_stream->zfree = 0;
 328                 decompress_stream->opaque = 0;
 329                 int err = ZLIB_PREFIX(inflateInit2)(decompress_stream, -MAX_WBITS);
 330                 if(err != Z_OK) {
 331                         decompress_stream->next_out = 0;
 332                         REPORT_DISSECTOR_BUG("Unable to create INFLATE context to decompress messages");
 333                         return NULL;
 334                 }
 335         }
 336
 337         // Create a temporary buffer of the maximum size, which will get cleaned up later
 338         // when the packet scope is freed
 339         uInt buffer_size = max_uncompressed_size * 1024;
 340         Bytef* decompress_buffer = (Bytef*)wmem_alloc(pinfo->pool, buffer_size);
 341         decompress_stream->next_in = (Bytef*)buf;
 342         decompress_stream->avail_in = length;
 343         decompress_stream->next_out = decompress_buffer;
 344         decompress_stream->avail_out = buffer_size;
 345         size_t start = decompress_stream->total_out;
 346         int err = ZLIB_PREFIX(inflate)(decompress_stream, Z_NO_FLUSH);
 347         if(err != Z_OK) {
 348                 proto_item* field = proto_tree_add_string(tree, hf_blip_message_body, tvb, offset, tvb_reported_length_remaining(tvb, offset), "<Error decompressing data>");
 349                 decompress_result_t* data_to_save = wmem_new0(wmem_file_scope(), decompress_result_t);
 350                 if(size_overflow && err == Z_DATA_ERROR) {
 351                         data_to_save->domain = overflow_error;
 352                         expert_add_info_format(pinfo, field, &ei_blip_decompress_buffer_error, "Unable to decompress message, buffer too small (%u Kb).  Please adjust in settings.", max_uncompressed_size);
 353                 } else {
 354                         data_to_save->domain = zlib_error;
 355                         data_to_save->code = err;
 356                         expert_add_info_format(pinfo, field, &ei_blip_decompress_buffer_error, "Unable to decompress message, got zlib error %d", err);
 357                 }
 358
 359                 p_add_proto_data(wmem_file_scope(), pinfo, proto_blip, 0, data_to_save);
 360                 return NULL;
 361         }
 362
 363         decompress_stream->next_in = trailer;
 364         decompress_stream->avail_in = 4;
 365         err = ZLIB_PREFIX(inflate)(decompress_stream, Z_SYNC_FLUSH);
 366         if(err != Z_OK) {
 367                 proto_item* field = proto_tree_add_string(tree, hf_blip_message_body, tvb, offset, tvb_reported_length_remaining(tvb, offset), "<Error decompressing data>");
 368                 decompress_result_t* data_to_save = wmem_new0(wmem_file_scope(), decompress_result_t);
 369                 if(err == Z_BUF_ERROR) {
 370                         data_to_save->domain = overflow_error;
 371                         size_overflow = true;
 372                         expert_add_info_format(pinfo, field, &ei_blip_decompress_buffer_error, "Unable to decompress message, buffer too small (%u Kb).  Please adjust in settings.", max_uncompressed_size);
 373                 } else {
 374                         data_to_save->domain = zlib_error;
 375                         data_to_save->code = err;
 376                         expert_add_info_format(pinfo, field, &ei_blip_decompress_buffer_error, "Unable to decompress message, got zlib error %d", err);
 377                 }
 378
 379                 p_add_proto_data(wmem_file_scope(), pinfo, proto_blip, 0, data_to_save);
 380                 return NULL;
 381         }
 382
 383         // Shrink the buffer so that there is not wasted space on the end of it since
 384         // it will be long lived in the file scope
 385         size_t bodyLength = decompress_stream->total_out - start;
 386         Bytef* shortened_buffer = (Bytef *)wmem_memdup(wmem_file_scope(), decompress_buffer, bodyLength);
 387
 388         tvbuff_t* decompressedChild = tvb_new_child_real_data(tvb, shortened_buffer, (unsigned)bodyLength, (int)bodyLength);
 389         add_new_data_source(pinfo, decompressedChild, "Decompressed Payload");
 390         decompress_result_t* data_to_save = wmem_new0(wmem_file_scope(), decompress_result_t);
 391         data_to_save->size = (size_t)bodyLength;
 392         data_to_save->buf = shortened_buffer;
 393         p_add_proto_data(wmem_file_scope(), pinfo, proto_blip, 0, data_to_save);
 394
 395         return decompressedChild;
 396 }
 397 #endif /* HAVE_ZLIB */
 398
 399 static int
 400 dissect_blip(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, _U_ void *data)
 401 {
 402
 403         proto_tree *blip_tree;
 404         int offset = 0;
 405
 406         /* Set the protocol column to say BLIP */
 407         col_set_str(pinfo->cinfo, COL_PROTOCOL, "BLIP");
 408         /* Clear out stuff in the info column */
 409         col_clear(pinfo->cinfo,COL_INFO);
 410
 411         // ------------------------------------- Setup BLIP tree -----------------------------------------------------------
 412
 413
 414         /* Add a subtree to dissection.  See WSDG 9.2.2. Dissecting the details of the protocol  */
 415         proto_item *blip_item = proto_tree_add_item(tree, proto_blip, tvb, offset, -1, ENC_NA);
 416
 417         blip_tree = proto_item_add_subtree(blip_item, ett_blip);
 418
 419
 420         // ------------------------ BLIP Frame Header: Message Number VarInt -----------------------------------------------
 421
 422         // This gets the message number as a var int in order to find out how much to bump
 423         // the offset for the next proto_tree item
 424         uint64_t value_message_num;
 425         unsigned varint_message_num_length = tvb_get_varint(
 426                         tvb,
 427                         offset,
 428                         FT_VARINT_MAX_LEN,
 429                         &value_message_num,
 430                         ENC_VARINT_PROTOBUF);
 431
 432         proto_tree_add_item(blip_tree, hf_blip_message_number, tvb, offset, varint_message_num_length, ENC_VARINT_PROTOBUF);
 433
 434         offset += varint_message_num_length;
 435
 436         // ------------------------ BLIP Frame Header: Frame Flags VarInt --------------------------------------------------
 437
 438         // This gets the message number as a var int in order to find out how much to bump
 439         // the offset for the next proto_tree item
 440         uint64_t value_frame_flags;
 441         unsigned varint_frame_flags_length = tvb_get_varint(
 442                         tvb,
 443                         offset,
 444                         FT_VARINT_MAX_LEN,
 445                         &value_frame_flags,
 446                         ENC_VARINT_PROTOBUF);
 447
 448         uint64_t masked = value_frame_flags & ~0x07;
 449         proto_tree_add_uint(blip_tree, hf_blip_frame_flags, tvb, offset, varint_frame_flags_length, (uint8_t)masked);
 450
 451         offset += varint_frame_flags_length;
 452
 453         const char* msg_type = get_message_type(value_frame_flags);
 454         char* msg_num = wmem_strdup_printf(pinfo->pool, "#%" PRIu64, value_message_num);
 455         char* col_info = wmem_strconcat(pinfo->pool, msg_type, msg_num, NULL);
 456         col_add_str(pinfo->cinfo, COL_INFO, col_info);
 457
 458         // If it's an ACK message, handle that separately, since there are no properties etc.
 459         if (is_ack_message(value_frame_flags) == true) {
 460                 return handle_ack_message(tvb, pinfo, blip_tree, offset, value_frame_flags);
 461         }
 462
 463
 464         // ------------------------------------- Conversation Tracking -----------------------------------------------------
 465
 466         blip_conversation_entry_t *conversation_entry_ptr = get_blip_conversation(pinfo);
 467
 468         // Is this the first frame in a blip message with multiple frames?
 469         bool first_frame_in_msg = is_first_frame_in_msg(
 470                         conversation_entry_ptr,
 471                         pinfo,
 472                         value_frame_flags,
 473                         value_message_num
 474         );
 475
 476         tvbuff_t* tvb_to_use = tvb;
 477         bool compressed = is_compressed(value_frame_flags);
 478
 479         if(compressed) {
 480 #if defined (HAVE_ZLIB) || defined (HAVE_ZLIBNG)
 481                 tvb_to_use = decompress(pinfo, blip_tree, tvb, offset, tvb_reported_length_remaining(tvb, offset) - BLIP_BODY_CHECKSUM_SIZE);
 482                 if(!tvb_to_use) {
 483                         return tvb_reported_length(tvb);
 484                 }
 485                 offset = 0;
 486 #else /* ! HAVE_ZLIB */
 487                 proto_tree_add_string(tree, hf_blip_message_body, tvb, offset, tvb_reported_length_remaining(tvb, offset), "<decompression support is not available>");
 488                 return tvb_reported_length(tvb);
 489 #endif /* ! HAVE_ZLIB */
 490         }
 491
 492         // Is this the first frame in a message?
 493         if (first_frame_in_msg == true) {
 494
 495                 // ------------------------ BLIP Frame Header: Properties Length VarInt --------------------------------------------------
 496
 497                 // WARNING: this only works because this code assumes that ALL MESSAGES FIT INTO ONE FRAME, which is absolutely not true.
 498                 // In other words, as soon as there is a message that spans two frames, this code will break.
 499
 500                 uint64_t value_properties_length;
 501                 unsigned value_properties_length_varint_length = tvb_get_varint(
 502                                 tvb_to_use,
 503                                 offset,
 504                                 FT_VARINT_MAX_LEN,
 505                                 &value_properties_length,
 506                                 ENC_VARINT_PROTOBUF);
 507
 508                 proto_tree_add_item(blip_tree, hf_blip_properties_length, tvb_to_use, offset, value_properties_length_varint_length, ENC_VARINT_PROTOBUF);
 509
 510                 offset += value_properties_length_varint_length;
 511
 512                 // ------------------------ BLIP Frame: Properties --------------------------------------------------
 513
 514                 // WARNING: this only works because this code assumes that ALL MESSAGES FIT INTO ONE FRAME, which is absolutely not true.
 515                 // In other words, as soon as there is a message that spans two frames, this code will break.
 516
 517                 // At this point, the length of the properties is known and is stored in value_properties_length.
 518                 // This reads the entire properties out of the tvb and into a buffer (buf).
 519                 uint8_t* buf = tvb_get_string_enc(pinfo->pool, tvb_to_use, offset, (int) value_properties_length, ENC_UTF_8);
 520
 521                 // "Profile\0subChanges\0continuous\0true\0foo\0bar" -> "Profile:subChanges:continuous:true:foo:bar"
 522                 // Iterate over buf and change all the \0 null characters to ':', since otherwise trying to set a header
 523                 // field to this buffer via proto_tree_add_item() will end up only printing it up to the first null character,
 524                 // for example "Profile", even though there are many more properties that follow.
 525                 for (int i = 0; i < (int) value_properties_length; i++) {
 526                         if (i < (int) (value_properties_length - 1)) {
 527                                 if (buf[i] == '\0') {  // TODO: I don't even know if this is actually a safe assumption in a UTF-8 encoded string
 528                                         buf[i] = ':';
 529                                 }
 530                         }
 531                 }
 532
 533                 if(value_properties_length > 0) {
 534                         proto_tree_add_string(blip_tree, hf_blip_properties, tvb_to_use, offset, (int)value_properties_length, (const char *)buf);
 535                 }
 536
 537                 // Bump the offset by the length of the properties
 538                 offset += (int)value_properties_length;
 539         }
 540
 541         // ------------------------ BLIP Frame: Message Body --------------------------------------------------
 542
 543         // WS_DLL_PUBLIC int tvb_reported_length_remaining(const tvbuff_t *tvb, const int offset);
 544         int reported_length_remaining = tvb_reported_length_remaining(tvb_to_use, offset);
 545
 546         // Don't read in the trailing checksum at the end
 547         if (!compressed && reported_length_remaining >= BLIP_BODY_CHECKSUM_SIZE) {
 548                 reported_length_remaining -= BLIP_BODY_CHECKSUM_SIZE;
 549         }
 550
 551         if(reported_length_remaining > 0) {
 552                 proto_tree_add_item(blip_tree, hf_blip_message_body, tvb_to_use, offset, reported_length_remaining, ENC_UTF_8);
 553         }
 554
 555         proto_tree_add_item(blip_tree, hf_blip_checksum, tvb, tvb_reported_length(tvb) - BLIP_BODY_CHECKSUM_SIZE, BLIP_BODY_CHECKSUM_SIZE, ENC_BIG_ENDIAN);
 556
 557         // -------------------------------------------- Etc ----------------------------------------------------------------
 558
 559         return tvb_captured_length(tvb);
 560 }
 561
 562 void
 563 proto_register_blip(void)
 564 {
 565         static hf_register_info hf[] = {
 566         { &hf_blip_message_number,
 567                 { "Message Number", "blip.messagenum", FT_UINT64, BASE_DEC,
 568                         NULL, 0x0, NULL, HFILL }
 569         },
 570         { &hf_blip_frame_flags,
 571                 { "Frame Flags", "blip.frameflags", FT_UINT8, BASE_HEX | BASE_EXT_STRING,
 572                         &flag_combos_ext, 0x0, NULL, HFILL }
 573         },
 574         { &hf_blip_properties_length,
 575                 { "Properties Length", "blip.propslength", FT_UINT64, BASE_DEC,
 576                         NULL, 0x0, NULL, HFILL }
 577         },
 578         { &hf_blip_properties,
 579                 { "Properties", "blip.props", FT_STRING, BASE_NONE,
 580                         NULL, 0x0, NULL, HFILL }
 581                 },
 582         { &hf_blip_message_body,
 583                 { "Message Body", "blip.messagebody", FT_STRING, BASE_NONE,
 584                         NULL, 0x0, NULL, HFILL }
 585         },
 586         { &hf_blip_ack_size,
 587                 { "ACK num bytes", "blip.numackbytes", FT_UINT64, BASE_DEC,
 588                         NULL, 0x0, NULL, HFILL }
 589         },
 590         { &hf_blip_checksum,
 591                 { "Checksum", "blip.checksum", FT_UINT32, BASE_DEC,
 592                         NULL, 0x0, NULL, HFILL }
 593         }
 594         };
 595
 596         /* Setup protocol subtree array */
 597         static int *ett[] = {
 598                 &ett_blip
 599         };
 600
 601         /* Expert Infos */
 602         static ei_register_info ei[] = {
 603                 { &ei_blip_decompress_buffer_error, { "blip.decompress_buffer_error", PI_UNDECODED, PI_WARN, "Decompression error", EXPFILL }}
 604         };
 605
 606         proto_blip = proto_register_protocol("BLIP Couchbase Mobile", "BLIP", "blip");
 607         expert_module_t* expert_blip = expert_register_protocol(proto_blip);
 608
 609         proto_register_field_array(proto_blip, hf, array_length(hf));
 610         proto_register_subtree_array(ett, array_length(ett));
 611         expert_register_field_array(expert_blip, ei, array_length(ei));
 612
 613         blip_handle = register_dissector("blip", dissect_blip, proto_blip);
 614
 615 #ifdef HAVE_ZLIB
 616         module_t *blip_module = prefs_register_protocol(proto_blip, NULL);
 617         prefs_register_uint_preference(blip_module, "max_uncompressed_size",
 618                                                 "Maximum uncompressed message size (Kb)",
 619                                                 "The maximum size of the buffer for uncompressed messages. "
 620                                                 "If a message is larger than this, then the packet containing "
 621                                                 "the message, as well as subsequent packets, will fail to "
 622                                                 "decompress", 10, &max_uncompressed_size);
 623 #endif
 624 }
 625
 626 void
 627 proto_reg_handoff_blip(void)
 628 {
 629
 630         // Register the blip dissector as a subprotocol dissector of "ws.protocol",
 631         // matching any packets with a Web-Sec-Protocol header of "BLIP_3+CBMobile_2"
 632         // "BLIP_3+CBMobile_3", or "BLIP_3+CBMobile_4"
 633         //
 634         // See https://github.com/couchbase/sync_gateway/issues/3356#issuecomment-370958321 for
 635         // more notes on how the websocket dissector routes packets down to subprotocol handlers.
 636
 637         dissector_add_string("ws.protocol", "BLIP_3+CBMobile_4", blip_handle);
 638         dissector_add_string("ws.protocol", "BLIP_3+CBMobile_3", blip_handle);
 639         dissector_add_string("ws.protocol", "BLIP_3+CBMobile_2", blip_handle);
 640 }
 641
 642 /*
 643  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 644  *
 645  * Local Variables:
 646  * c-basic-offset: 8
 647  * tab-width: 8
 648  * indent-tabs-mode: t
 649  * End:
 650  *
 651  * ex: set shiftwidth=8 tabstop=8 noexpandtab:
 652  * :indentSize=8:tabSize=8:noTabs=false:
 653  */