commit 87030aa09dbb837da1aaeac79834bf829ffabb75 Author: Jeffrey Wang jeffreyw@stanford.edu Date: Wed Dec 7 08:10:58 2011 +0000

fixing a couple of chopper bugs; changing steg module constructor to have access to is_clientside

git-svn-id: svn+ssh://spartan.csl.sri.com/svn/private/DEFIANCE@177 a58ff0ac-194c-e011-a152-003048836090 --- src/protocol/chop.cc | 15 ++++++++++++--- src/steg.h | 7 ++----- src/steg/embed.cc | 34 +++++++++++++++------------------- src/steg/http.cc | 3 ++- 4 files changed, 31 insertions(+), 28 deletions(-)

diff --git a/src/protocol/chop.cc b/src/protocol/chop.cc index 3e87428..f960fbb 100644 --- a/src/protocol/chop.cc +++ b/src/protocol/chop.cc @@ -38,6 +38,7 @@ struct chop_header #define CHOP_WIRE_HDR_LEN (sizeof(struct chop_header)) #define CHOP_MAX_DATA 16384 #define CHOP_MAX_CHAFF 2048 +#define CHOP_BLOCK_OVERHD (CHOP_WIRE_HDR_LEN + GCM_TAG_LEN)

#define CHOP_F_SYN 0x0001 #define CHOP_F_FIN 0x0002 @@ -247,6 +248,11 @@ chop_pick_connection(chop_circuit_t *ckt, size_t desired, size_t *blocksize) log_debug(conn, "offers %lu bytes (%s)", (unsigned long)room, conn->steg->name());

+ if (room <= CHOP_BLOCK_OVERHD) + room = 0; + else + room -= CHOP_BLOCK_OVERHD; + if (room > CHOP_MAX_DATA) room = CHOP_MAX_DATA;

@@ -326,6 +332,11 @@ chop_send_block(conn_t *d, if (evbuffer_commit_space(block, &v, 1)) goto fail;

+ // TODO: this should be moved after the steg transmit, but currently that + // prevents conn_transmit_soon calls inside steg transmit + if (dest->must_transmit_timer) + evtimer_del(dest->must_transmit_timer); + if (dest->steg->transmit(block, dest)) goto fail_committed;

@@ -341,8 +352,6 @@ chop_send_block(conn_t *d, ckt->sent_fin = true; log_debug(dest, "sent %lu+%u byte block [flags %04hx]", (unsigned long)CHOP_WIRE_HDR_LEN, length, flags); - if (dest->must_transmit_timer) - evtimer_del(dest->must_transmit_timer); return 0;

fail: @@ -451,7 +460,7 @@ chop_send_targeted(circuit_t *c, conn_t *target, size_t blocksize) if (blocksize > CHOP_MAX_CHAFF) blocksize = CHOP_MAX_CHAFF;

- blocksize = rng_range(1, blocksize); + blocksize = rng_range(1, blocksize + 1); log_debug(target, "generating %lu bytes chaff", (unsigned long)blocksize);

chaff = evbuffer_new(); diff --git a/src/steg.h b/src/steg.h index 0f83c93..c78ffd7 100644 --- a/src/steg.h +++ b/src/steg.h @@ -100,10 +100,7 @@ steg_t *steg_detect(conn_t *conn); static bool mod##_detect(conn_t *conn) \ { return mod::detect(conn); } \ static steg_t *mod##_new(bool is_clientside) \ - { steg_t *s = new mod; \ - s->is_clientside = is_clientside; \ - return s; \ - } \ + { return new mod(is_clientside); } \ \ /* canned methods */ \ const char *mod::name() { return #mod; } \ @@ -116,7 +113,7 @@ steg_t *steg_detect(conn_t *conn);

#define STEG_DECLARE_METHODS(mod) \ static bool detect(conn_t *conn); \ - mod(); \ + mod(bool is_clientside); \ virtual ~mod(); \ virtual const char *name(); \ virtual size_t transmit_room(conn_t *conn); \ diff --git a/src/steg/embed.cc b/src/steg/embed.cc index d887ea7..75562bc 100644 --- a/src/steg/embed.cc +++ b/src/steg/embed.cc @@ -1,6 +1,7 @@ #include "util.h" #include "connections.h" #include "steg.h" +#include "rng.h"

#include <event2/buffer.h> #include <event2/event.h> @@ -66,12 +67,11 @@ void init_embed_traces() { } 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; + return rng_int(embed_num_traces); }

bool embed::advance_packet() { @@ -96,9 +96,16 @@ bool embed::is_finished() { return cur_pkt >= cur->num_pkt; }

-embed::embed() { +embed::embed(bool is_clientside) { if (!embed_init) init_embed_traces(); + + this->is_clientside = is_clientside; cur_idx = -1; + if (is_clientside) { + cur_idx = get_random_trace(); + cur = &embed_traces[cur_idx]; + cur_pkt = 0; + } gettimeofday(&last_pkt, NULL); }

@@ -110,8 +117,7 @@ bool embed::detect(conn_t *conn) { struct evbuffer *source = conn_get_inbound(conn); size_t src_len = evbuffer_get_length(source);

- log_debug("detecting buffer of length %lu", - (unsigned long)src_len); + log_debug("detecting buffer of length %lu", (unsigned long)src_len);

int cur_idx; if (evbuffer_copyout(source, &cur_idx, 4) != 4) return 0; @@ -131,24 +137,14 @@ bool embed::detect(conn_t *conn) { }

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; - } + if (is_finished() || !is_outgoing()) return 0;

int time_diff = millis_since(&last_pkt); - size_t room; - - if (is_finished() || !is_outgoing()) return 0; if (get_pkt_time() > time_diff+10) return 0;

- // 24 bytes for chop header, 16 bytes for GCM tag, 2 bytes for data length - // 4 bytes for the index of a new trace - room = get_pkt_size() - 42; - if (cur_pkt == 0) { - room -= 4; - } + // 2 bytes for data length, 4 bytes for the index of a new trace + size_t room = get_pkt_size() - 2; + if (cur_pkt == 0) room -= 4; return room; }

diff --git a/src/steg/http.cc b/src/steg/http.cc index aed9322..e4bdb0e 100644 --- a/src/steg/http.cc +++ b/src/steg/http.cc @@ -130,9 +130,10 @@ buf_dump(unsigned char* buf, int len, FILE *out) }

-http::http() +http::http(bool is_clientside) : have_transmitted(false), have_received(false) { + this->is_clientside = is_clientside; if (is_clientside) load_payloads("traces/client.out"); else {