packet_t *packet_parse(uint8_t *data, size_t length, options_t options)
{
packet_t *packet = (packet_t*) safe_malloc(sizeof(packet_t));
buffer_t *buffer = buffer_create_with_data(BO_BIG_ENDIAN, data, length);
/* Validate the size */
if(buffer_get_length(buffer) > MAX_PACKET_SIZE)
{
LOG_FATAL("Packet is too long: %zu bytes\n", buffer_get_length(buffer));
exit(1);
}
packet->packet_id = buffer_read_next_int16(buffer);
packet->packet_type = (packet_type_t) buffer_read_next_int8(buffer);
packet->session_id = buffer_read_next_int16(buffer);
switch(packet->packet_type)
{
case PACKET_TYPE_SYN:
packet->body.syn.seq = buffer_read_next_int16(buffer);
packet->body.syn.options = buffer_read_next_int16(buffer);
break;
case PACKET_TYPE_MSG:
if(options & OPT_CHUNKED_DOWNLOAD)
{
packet->body.msg.options.chunked.chunk = buffer_read_next_int32(buffer);
}
else
{
packet->body.msg.options.normal.seq = buffer_read_next_int16(buffer);
packet->body.msg.options.normal.ack = buffer_read_next_int16(buffer);
}
packet->body.msg.data = buffer_read_remaining_bytes(buffer, &packet->body.msg.data_length, -1, FALSE);
break;
case PACKET_TYPE_FIN:
packet->body.fin.reason = buffer_alloc_next_ntstring(buffer);
break;
case PACKET_TYPE_PING:
packet->body.ping.data = buffer_alloc_next_ntstring(buffer);
break;
default:
LOG_FATAL("Error: unknown message type (0x%02x)\n", packet->packet_type);
exit(0);
}
buffer_destroy(buffer);
return packet;
}
void sessions_print(sessions_t *sessions)
{
session_t *session = sessions->first_session;
while(session)
{
fprintf(stderr, "%s: %d bytes waiting\n", session->name, buffer_get_length(session->buffer));
session = (session_t*)session->next_session;
}
if(buffer_can_read_int8(sessions->buffer_data))
fprintf(stderr, "%d bytes buffered\n", buffer_get_length(sessions->buffer_data));
}
// Parses body. Returns true iff progress was made.
bool frameparser_parse_body(frameparser *fp, buffer *b)
{
log_printf(LOG_LEVEL_DEBUG, "frameparser_parse_body\n");
if (fp->length_left == FP_LENGTH_UNKNOWN)
{
// Look for NUL terminator
int nulpos = buffer_find_byte(b, '\x00');
if (nulpos < 0)
{
// No NUL, so grab everything
int count = buffer_get_length(b);
bytestring *body = frame_ensure_body(fp->cur_frame);
buffer_append_bytestring(b, body, 0, count);
buffer_consume(b, count);
return true;
}
else if (nulpos == 0)
{
// NUL as next character, so the frame is complete
fp->state = FP_STATE_END;
return true;
}
else
{
// NUL after some other bytes, so grab them and the frame is complete
bytestring *body = frame_ensure_body(fp->cur_frame);
buffer_append_bytestring(b, body, 0, nulpos);
buffer_consume(b, nulpos);
fp->state = FP_STATE_END;
return true;
}
}
else
{
// Remaining length is known. Figure out how many bytes to grab.
int count = buffer_get_length(b);
if (fp->length_left < count)
count = fp->length_left;
// Grab the bytes
bytestring *body = frame_ensure_body(fp->cur_frame);
buffer_append_bytestring(b, body, 0, count);
buffer_consume(b, count);
fp->length_left -= count;
// If we satisfied the expected length then the frame is complete
if (fp->length_left == 0)
fp->state = FP_STATE_END;
return true;
}
}
// Parses a frame's command. Returns true iff progress was made.
bool frameparser_parse_command(frameparser *fp, buffer *b)
{
log_printf(LOG_LEVEL_DEBUG, "frameparser_parse_command\n");
// Valid input in this state is a string followed by CR/LF or LF, which matches a known frame command
// Try to find LF line terminator
int lfpos = buffer_find_byte(b, '\x0A');
if (lfpos < 0) // No LF yet?
{
if (buffer_get_length(b) > LIMIT_FRAME_CMD_LINE_LEN)
frameparser_set_error(fp, "Line length limit exceeded waiting for command");
return false; // No progress
}
else if (lfpos == 0)
abort(); // Should never happen in this state
// Figure out number of bytes in command string
int len = lfpos;
if (buffer_get_byte(b, len - 1) == '\x0D')
len--;
// Extract the command into a new bytestring
bytestring *bs = bytestring_new(len);
buffer_append_bytestring(b, bs, 0, len);
bytestring_dump(bs);
// Consume the current line
buffer_consume(b, lfpos + 1);
// Find the command code for this command
frame_command cmd = frame_command_code(bytestring_get_bytes(bs), bytestring_get_length(bs));
// Clean up the bytestring
bytestring_free(bs);
// Make sure command is valid
if (cmd == CMD_NONE)
{
frameparser_set_error(fp, "Unknown command");
return false;
}
// Set up a new frame structure to hold parsed data
if (!fp->cur_frame)
fp->cur_frame = frame_new();
// Store parsed data
frame_set_command(fp->cur_frame, cmd);
// Got a valid command, so headers should be next
fp->state = FP_STATE_HEADER;
return true;
}
frameparser_outcome frameparser_parse(frameparser *fp, buffer *b)
{
// Parse as much as we can from the buffer
bool done = false;
while ((!done) && (buffer_get_length(b) > 0))
{
if (!frameparser_parse_internal(fp, b))
done = true;
}
// Can't make any more parsing progress for now. Might as well compact the buffer.
buffer_compact(b);
if (fp->state == FP_STATE_ERROR)
return FP_OUTCOME_ERROR;
else if (fp->fin_frame)
return FP_OUTCOME_FRAME;
return FP_OUTCOME_WAITING;
}
// Push waiting output out to the socket.
void connection_pump_output(connection *c)
{
int writecount = 0;
// If we have data waiting to go out, try writing it
size_t outbuflen = buffer_get_length(c->outbuffer);
if (outbuflen > 0)
{
writecount = buffer_output_fd(c->outbuffer, c->fd, outbuflen);
if (writecount < 0)
{
int error = errno;
if (error == EPIPE)
connection_close(c);
else if ((error != EAGAIN) && (error != EWOULDBLOCK))
connection_abort(c, error); // Unexpected error
}
}
// Update write timestamp, if needed
if (writecount > 0)
gettimeofday(&c->writetime, NULL);
}
// Parses keepalive linefeeds. Returns true iff progress was made.
bool frameparser_parse_idle(frameparser *fp, buffer *b)
{
log_printf(LOG_LEVEL_DEBUG, "frameparser_parse_idle\n");
// Valid input in this state is a CR/LF pair, or bare LF
uint8_t byte = buffer_get_byte(b, 0);
if (byte == '\x0D')
{
// Should be CR/LF pair. Make sure we have at least two bytes
size_t len = buffer_get_length(b);
if (len < 2)
return false; // No progress
// Make sure second byte is LF
byte = buffer_get_byte(b, 1);
if (byte != '\x0A')
{
frameparser_set_error(fp, "Expected 0x0A after 0x0D, got 0x%02X", byte);
return false; // No progress
}
// Eat the CR/LF pair
buffer_consume(b, 2);
return true;
}
else if (byte == '\x0A')
{
// Bare LF
buffer_consume(b, 1);
return true;
}
// Something else? Must be the start of a frame
fp->state = FP_STATE_COMMAND;
return true;
}
/* Needs to be freed with safe_free() */
uint8_t *command_packet_to_bytes(command_packet_t *packet, size_t *length)
{
buffer_t *buffer = buffer_create(BO_BIG_ENDIAN);
buffer_t *buffer_with_size = buffer_create(BO_BIG_ENDIAN);
uint16_t packed_id;
packed_id = (packet->is_request ? 0x0000 : 0x8000);
packed_id |= (packet->request_id & 0x7FFF);
buffer_add_int16(buffer, packed_id);
buffer_add_int16(buffer, packet->command_id);
switch(packet->command_id)
{
case COMMAND_PING:
if(packet->is_request)
buffer_add_ntstring(buffer, packet->r.request.body.ping.data);
else
buffer_add_ntstring(buffer, packet->r.response.body.ping.data);
break;
case COMMAND_SHELL:
if(packet->is_request)
buffer_add_ntstring(buffer, packet->r.request.body.shell.name);
else
buffer_add_int16(buffer, packet->r.response.body.shell.session_id);
break;
case COMMAND_EXEC:
if(packet->is_request)
{
buffer_add_ntstring(buffer, packet->r.request.body.exec.name);
buffer_add_ntstring(buffer, packet->r.request.body.exec.command);
}
else
{
buffer_add_int16(buffer, packet->r.response.body.exec.session_id);
}
break;
case COMMAND_DOWNLOAD:
if(packet->is_request)
{
buffer_add_ntstring(buffer, packet->r.request.body.download.filename);
}
else
{
buffer_add_bytes(buffer, packet->r.response.body.download.data, packet->r.response.body.download.length);
}
break;
case COMMAND_UPLOAD:
if(packet->is_request)
{
buffer_add_ntstring(buffer, packet->r.request.body.upload.filename);
buffer_add_bytes(buffer, packet->r.request.body.upload.data, packet->r.request.body.upload.length);
}
else
{
}
break;
case COMMAND_SHUTDOWN:
break;
case TUNNEL_CONNECT:
if(packet->is_request)
{
buffer_add_int32(buffer, packet->r.request.body.tunnel_connect.options);
buffer_add_ntstring(buffer, packet->r.request.body.tunnel_connect.host);
buffer_add_int16(buffer, packet->r.request.body.tunnel_connect.port);
}
else
{
buffer_add_int32(buffer, packet->r.response.body.tunnel_connect.tunnel_id);
}
break;
case TUNNEL_DATA:
if(packet->is_request)
{
buffer_add_int32(buffer, packet->r.request.body.tunnel_data.tunnel_id);
buffer_add_bytes(buffer, packet->r.request.body.tunnel_data.data, packet->r.request.body.tunnel_data.length);
}
else
{
}
break;
case TUNNEL_CLOSE:
if(packet->is_request)
{
buffer_add_int32(buffer, packet->r.request.body.tunnel_close.tunnel_id);
buffer_add_ntstring(buffer, packet->r.request.body.tunnel_close.reason);
}
else
{
}
break;
case COMMAND_ERROR:
if(packet->is_request)
{
buffer_add_int16(buffer, packet->r.request.body.error.status);
buffer_add_ntstring(buffer, packet->r.request.body.error.reason);
}
else
{
buffer_add_int16(buffer, packet->r.response.body.error.status);
buffer_add_ntstring(buffer, packet->r.response.body.error.reason);
}
break;
default:
LOG_FATAL("Unknown command_id: 0x%04x", packet->command_id);
exit(1);
}
buffer_add_int32(buffer_with_size, buffer_get_length(buffer));
buffer_add_buffer(buffer_with_size, buffer);
buffer_destroy(buffer);
return buffer_create_string_and_destroy(buffer_with_size, length);
}
// Parses a header line. Returns true iff progress was made.
bool frameparser_parse_header(frameparser *fp, buffer *b)
{
log_printf(LOG_LEVEL_DEBUG, "frameparser_parse_header\n");
// Valid input in this state is either:
// 1. CR/LF or LF alone, denoting the end of headers
// 2. A key name, followed by a colon, followed by a value name, terminated with CR/LF or LF
// Try to find LF line terminator
int lfpos = buffer_find_byte(b, '\x0A');
if (lfpos < 0) // No LF yet?
{
if (buffer_get_length(b) > LIMIT_FRAME_HEADER_LINE_LEN)
frameparser_set_error(fp, "Line length limit exceeded waiting for header");
return false; // No progress
}
else if (lfpos == 0) // LF alone
{
buffer_consume(b, 1);
frameparser_parse_headers_complete(fp);
return true;
}
else if ((lfpos == 1) && (buffer_get_byte(b, 0) == '\x0D')) // CR/LF alone
{
buffer_consume(b, 2);
frameparser_parse_headers_complete(fp);
return true;
}
// Figure out number of bytes in the line
int len = lfpos;
if (buffer_get_byte(b, len - 1) == '\x0D')
len--;
// Find the colon delimiter
int colonpos = buffer_find_byte_within(b, ':', 0, len);
if (colonpos < 0) // No colon?
{
frameparser_set_error(fp, "Expected colon delimiter on header line");
return false;
}
else if (colonpos == 0) // Starts with colon?
{
frameparser_set_error(fp, "Header name has zero length");
return false;
}
// Extract the key
bytestring *key = bytestring_new(colonpos);
buffer_append_bytestring(b, key, 0, colonpos);
// Extract the value
bytestring *val = bytestring_new(len - colonpos - 1);
buffer_append_bytestring(b, val, colonpos + 1, len - colonpos - 1);
// Consume the current line
buffer_consume(b, lfpos + 1);
// Unescape the key and value if needed
frame_command cmd = frame_get_command(fp->cur_frame);
if ((cmd != CMD_CONNECT) && (cmd != CMD_CONNECTED))
{
key = unescape_header_bytestring(key);
val = unescape_header_bytestring(val);
}
bytestring_dump(key);
bytestring_dump(val);
headerbundle *hb = frame_get_headerbundle(fp->cur_frame);
headerbundle_append_header(hb, key, val); // The bundle takes ownership of key and val
return true;
}
