commit 9fae0496723181c1da06ff856ff951d768371a87 Author: Jeffrey Wang <jeffreyw@stanford.edu> Date: Tue Dec 6 07:34:48 2011 +0000 a reasonable implementation of embed::detect() git-svn-id: svn+ssh://spartan.csl.sri.com/svn/private/DEFIANCE@175 a58ff0ac-194c-e011-a152-003048836090 --- src/steg/embed.cc | 32 ++++++++++++++++++++++++++------ 1 files changed, 26 insertions(+), 6 deletions(-) diff --git a/src/steg/embed.cc b/src/steg/embed.cc index 9b562d9..1e13851 100644 --- a/src/steg/embed.cc +++ b/src/steg/embed.cc @@ -104,9 +104,29 @@ embed::embed() { embed::~embed() { } -bool embed::detect(conn_t * /* conn */) { - // TODO: no good way to detect right now - return 0; /* change to 1 when testing */ +bool embed::detect(conn_t *conn) { + if (!embed_init) init_embed_traces(); + + struct evbuffer *source = conn_get_inbound(conn); + size_t src_len = evbuffer_get_length(source); + + log_debug("detecting buffer of length %d", src_len); + + int cur_idx; + if (evbuffer_copyout(source, &cur_idx, 4) != 4) return 0; + if (cur_idx < 0 || cur_idx >= embed_num_traces) return 0; + + trace_t *cur = &embed_traces[cur_idx]; + size_t tot_len = 0; + int idx = 0; + while (idx < cur->num_pkt && cur->pkt_sizes[idx] >= 0) { + tot_len += cur->pkt_sizes[idx++]; + if (src_len == tot_len) { + log_debug("detected embed trace %d", cur_idx); + return 1; + } + } + return 0; } size_t embed::transmit_room(conn_t * /* conn */) { @@ -122,9 +142,9 @@ size_t embed::transmit_room(conn_t * /* conn */) { if (is_finished() || !is_outgoing()) return 0; if (get_pkt_time() > time_diff+10) return 0; - // 24 bytes for chop header, 2 bytes for data length + // 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() - 26; + room = get_pkt_size() - 42; if (cur_pkt == 0) { room -= 4; } @@ -187,7 +207,7 @@ int embed::receive(conn_t *conn, struct evbuffer *dest) { cur_pkt = 0; pkt_size += 4; - log_debug("detected trace %d", cur_idx); + log_debug("received first packet of trace %d", cur_idx); } // keep reading data and padding from the source, advancing the packet