commit a43ae4dc1ce5475d6a1265af3fc318b4921bf36b Author: Jeffrey Wang jeffreyw@stanford.edu Date: Sun Dec 4 08:24:11 2011 +0000

initial commit for 'embed' steg module, needs chopper changes to work

git-svn-id: svn+ssh://spartan.csl.sri.com/svn/private/DEFIANCE@169 a58ff0ac-194c-e011-a152-003048836090 --- src/steg/embed.cc | 234 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 234 insertions(+), 0 deletions(-)

diff --git a/src/steg/embed.cc b/src/steg/embed.cc new file mode 100644 index 0000000..1e3c34c --- /dev/null +++ b/src/steg/embed.cc @@ -0,0 +1,234 @@ +#include "util.h" +#include "connections.h" +#include "steg.h" + +#include <event2/buffer.h> +#include <event2/event.h> +#include <stdio.h> +#include <unistd.h> +#include <time.h> + +typedef struct trace_t { + int num_pkt; // number of packets in trace + short *pkt_sizes; // packet sizes (positive = client->server) + int *pkt_times; // packet inter-arrival times +} trace_t; + +namespace { + struct embed : steg_t { + int cur_idx; // current trace index + trace_t *cur; // current trace + int cur_pkt; // current packet in the trace + struct timeval last_pkt; // time at which last packet was sent/received + + STEG_DECLARE_METHODS(embed); + }; +} + +static int embed_init = 0; // whether traces are initialized +static int embed_num_traces; // number of traces +static trace_t *embed_traces; // global array of all traces + +STEG_DEFINE_MODULE(embed, 1024, 1024, 1, 1); + +int millis_since(struct timeval *last) { + struct timeval cur; + int diff = 0; + gettimeofday(&cur, NULL); + + diff += (cur.tv_sec - last->tv_sec) * 1000; + diff += (cur.tv_usec - last->tv_usec) / 1000; + return diff; +} + +void init_embed_traces() { + // read in traces to use for connections + FILE *trace_file = fopen("traces/embed.txt", "r"); + fscanf(trace_file, "%d", &embed_num_traces); + embed_traces = (trace_t *)xmalloc(sizeof(trace_t) * embed_num_traces); + for (int i = 0; i < embed_num_traces; i++) { + int num_pkt; + fscanf(trace_file, "%d", &num_pkt); + embed_traces[i].num_pkt = num_pkt; + embed_traces[i].pkt_sizes = (short *)xmalloc(sizeof(short) * num_pkt); + embed_traces[i].pkt_times = (int *)xmalloc(sizeof(int) * num_pkt); + for (int j = 0; j < embed_traces[i].num_pkt; j++) { + fscanf(trace_file, "%hd %d", + &embed_traces[i].pkt_sizes[j], + &embed_traces[i].pkt_times[j]); + } + } + log_debug("read %d traces to use", embed_num_traces); + + srand(time(NULL)); + embed_init = 1; +} + +int get_random_trace() { + return rand() % embed_num_traces; +} + +bool advance_packet(embed *state) { + state->cur_pkt++; + return state->cur_pkt == state->cur->num_pkt; +} + +short get_pkt_size(embed *state) { + return abs(state->cur->pkt_sizes[state->cur_pkt]); +} + +bool is_outgoing(embed *state) { + return (state->cur->pkt_sizes[state->cur_pkt] < 0) ^ (state->is_clientside); +} + +int get_pkt_time(embed *state) { + return state->cur->pkt_times[state->cur_pkt]; +} + +bool is_finished(embed *state) { + if (state->cur_idx == -1) return true; + return state->cur_pkt >= state->cur->num_pkt; +} + +embed::embed() { + if (!embed_init) init_embed_traces(); + cur_idx = -1; + gettimeofday(&last_pkt, NULL); +} + +embed::~embed() { } + +bool embed::detect(conn_t * /* conn */) { + return 1; +} + +size_t embed::transmit_room(conn_t * /* conn */) { + if (cur_idx == -1 && is_clientside) { + cur_idx = get_random_trace(); + cur = &embed_traces[cur_idx]; + cur_pkt = 0; + } + + int time_diff = millis_since(&last_pkt); + size_t room; + + if (is_finished(this) || !is_outgoing(this)) return 0; + if (get_pkt_time(this) > time_diff+10) return 0; + + // 24 bytes for chop header, 2 bytes for data length + // 4 bytes for the index of a new trace + room = get_pkt_size(this) - 26; + if (cur_pkt == 0) { + room -= 4; + } + return room; +} + +int embed::transmit(struct evbuffer *source, conn_t *conn) { + struct evbuffer *dest = conn_get_outbound(conn); + short src_len = evbuffer_get_length(source); + short pkt_size = get_pkt_size(this); + short used = src_len + 2; + + // starting a new trace, send the index + if (cur_pkt == 0) { + if (evbuffer_add(dest, &cur_idx, 4) == -1) return -1; + used += 4; + log_debug("sending trace %d", cur_idx); + } + + log_debug("sending packet %d of trace %d", cur_pkt, cur_idx); + + // add the data length and data to the dest buffer + if (evbuffer_add(dest, &src_len, 2) == -1) return -1; + if (evbuffer_add_buffer(dest, source) == -1) return -1; + log_debug("sending data with length %d", src_len); + + // if there is more space in the packet, pad it + if (pkt_size > used) { + size_t padding = pkt_size - used; + unsigned char zero[padding]; + memset(zero, 0, padding); + evbuffer_add(dest, zero, padding); + } + + // check if this trace is finished and whether we need to send again + if (advance_packet(this)) { + log_debug("send finished trace"); + conn_close_after_transmit(conn); + } else if (is_outgoing(this)) { + log_debug("sending again in %d ms", get_pkt_time(this)); + conn_transmit_soon(conn, get_pkt_time(this)); + } + + // update last time + gettimeofday(&last_pkt, NULL); + return 0; +} + +int embed::receive(conn_t *conn, struct evbuffer *dest) { + struct evbuffer *source = conn_get_inbound(conn); + short src_len = evbuffer_get_length(source); + short pkt_size = 0; + + log_debug("receiving buffer of length %d", src_len); + + // if we are receiving the first packet of the trace, read the index + if (cur_idx == -1) { + if (evbuffer_remove(source, &cur_idx, 4) != 4) return -1; + cur = &embed_traces[cur_idx]; + cur_pkt = 0; + pkt_size += 4; + + log_debug("detected trace %d", cur_idx); + } + + // keep reading data and padding from the source, advancing the packet + // in the trace when we have read enough bytes + while (1) { + // the next full packet is not in the source buffer yet + int exp_pkt_size = get_pkt_size(this); + if (src_len < exp_pkt_size) break; + + // read data + short data_len; + if (evbuffer_remove(source, &data_len, 2) != 2) return -1; + if (data_len > 0) { + if (evbuffer_remove_buffer(source, dest, data_len) != data_len) { + return -1; + } + } + pkt_size += data_len + 2; + + // read padding + if (exp_pkt_size > pkt_size) { + size_t padding = exp_pkt_size - pkt_size; + if (evbuffer_drain(source, padding) == -1) return -1; + } + + src_len -= exp_pkt_size; + pkt_size = 0; + + log_debug("received packet %d of trace %d", + cur_pkt, cur_idx); + + // advance packet; if done with trace, sender should close connection + if (advance_packet(this)) { + conn_cease_transmission(conn); + conn_expect_close(conn); + log_debug("received last packet in trace"); + return 0; + } + } + + if (is_outgoing(this)) { + log_debug("preparing to send in %d ms", get_pkt_time(this)); + conn_transmit_soon(conn, get_pkt_time(this)); + } + + log_debug("remaining source length: %d", src_len); + + // update last time + gettimeofday(&last_pkt, NULL); + return 0; +}