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[obfsproxy/master] Implement functional shared secret support.
by nickm＠torproject.org 28 May '11

28 May '11

commit c6a369e197cae2e677106ac2b126abcfdaed6a43 Author: George Kadianakis <desnacked(a)gmail.com> Date: Tue May 17 03:05:42 2011 +0200 Implement functional shared secret support. --- src/main.c | 37 ++++++++++++++++++++++--------------- src/network.c | 30 ++++++++++++++---------------- src/network.h | 2 +- src/protocol.c | 6 +++--- src/protocol.h | 40 ++++++++++++++++++++++++---------------- src/protocols/dummy.c | 4 +++- src/protocols/dummy.h | 2 +- src/protocols/obfs2.c | 30 ++++++++++++++++++++++-------- src/protocols/obfs2.h | 4 +--- src/test/unittest.c | 2 +- src/test/unittest_obfs2.c | 2 ++ 11 files changed, 94 insertions(+), 65 deletions(-) diff --git a/src/main.c b/src/main.c index 225c698..1c084d3 100644 --- a/src/main.c +++ b/src/main.c @@ -25,7 +25,7 @@ static void usage(void) { fprintf(stderr, - "Usage: obfsproxy {client/server/socks} {obfs2/dummy} listenaddr[:port] targetaddr:port\n" + "Usage: obfsproxy {client/server/socks} {obfs2/dummy} listenaddr[:port] targetaddr:port <shared secret>\n" " (Default listen port is 48988 for client; 23548 for socks; 11253 for server)\n" ); exit(1); @@ -49,6 +49,7 @@ main(int argc, const char **argv) struct sockaddr *sa_target=NULL; int sl_listen, sl_target=0; const char *defport; + char *shared_secret = NULL; struct event_base *base; struct event *sigevent; @@ -85,19 +86,25 @@ main(int argc, const char **argv) if (resolve_address_port(argv[3], 1, 1, &ss_listen, &sl_listen, defport) < 0) usage(); - if (is_socks) { - if (argc != 4) - usage(); - } else { - if (argc != 5) - usage(); - - /* figure out what place to connect to as a client/server. */ - /* XXXX when we add socks support, clients will not have a fixed "target" - * XXXX address but will instead connect to a client-selected address. */ - if (resolve_address_port(argv[4], 1, 0, &ss_target, &sl_target, NULL) < 0) - usage(); - sa_target = (struct sockaddr *)&ss_target; + /* figure out what place to connect to as a client/server. */ + /* XXXX when we add socks support, clients will not have a fixed "target" + * XXXX address but will instead connect to a client-selected address. */ + if (resolve_address_port(argv[4], 1, 0, &ss_target, &sl_target, NULL) < 0) + usage(); + sa_target = (struct sockaddr *)&ss_target; + + /* Let's see if the user wants a shared secret. + So ugly. So ugly. So ugly. So ugly. So ugly interface. + */ + if (argc > 5 && argc != 6) + usage(); + if (argc == 6) { + if (protocol != OBFS2_PROTOCOL) { + printf("shared secret is only supported with obfs2 atm.\n"); + exit(1); + } + + shared_secret = strdup(argv[5]); } /* Initialize libevent */ @@ -121,7 +128,7 @@ main(int argc, const char **argv) mode, protocol, (struct sockaddr *)&ss_listen, sl_listen, sa_target, sl_target, - NULL, 0); + shared_secret); if (! listener) { printf("Couldn't create listener!\n"); return 4; diff --git a/src/network.c b/src/network.c index b0106de..a32cb1d 100644 --- a/src/network.c +++ b/src/network.c @@ -29,10 +29,8 @@ struct listener_t { int target_address_len; int proto; /* Protocol that this listener can speak. */ int mode; - /* ASN */ - /* char shared_secret[SHARED_SECRET_LENGTH]; + const char *shared_secret; unsigned int have_shared_secret : 1; - */ }; static void simple_listener_cb(struct evconnlistener *evcl, @@ -54,7 +52,7 @@ listener_new(struct event_base *base, int mode, int protocol, const struct sockaddr *on_address, int on_address_len, const struct sockaddr *target_address, int target_address_len, - const char *shared_secret, size_t shared_secret_len) + const char *shared_secret) { const unsigned flags = LEV_OPT_CLOSE_ON_FREE|LEV_OPT_CLOSE_ON_EXEC|LEV_OPT_REUSEABLE; @@ -70,6 +68,8 @@ listener_new(struct event_base *base, lsn->proto = protocol; lsn->mode = mode; + lsn->shared_secret = shared_secret; + lsn->have_shared_secret = 1; if (target_address) { assert(target_address_len <= sizeof(struct sockaddr_storage)); @@ -79,15 +79,6 @@ listener_new(struct event_base *base, assert(lsn->mode == LSN_SOCKS_CLIENT); } - /* ASN */ - /* - assert(shared_secret == NULL || shared_secret_len == SHARED_SECRET_LENGTH); - if (shared_secret) { - memcpy(lsn->shared_secret, shared_secret, SHARED_SECRET_LENGTH); - lsn->have_shared_secret = 1; - } - */ - lsn->listener = evconnlistener_new_bind(base, simple_listener_cb, lsn, flags, -1, @@ -124,10 +115,17 @@ simple_listener_cb(struct evconnlistener *evcl, conn->mode = lsn->mode; - /* Will all protocols need to _init() here? Don't think so! */ + struct protocol_params_t *proto_params = calloc(1, sizeof(struct protocol_params_t)); + proto_params->is_initiator = conn->mode != LSN_SIMPLE_SERVER; + proto_params->shared_secret = lsn->shared_secret; + conn->proto = proto_new(lsn->proto, - conn->mode != LSN_SIMPLE_SERVER); - + proto_params); + if (!conn->proto) { + printf("Creation of protocol object failed! Closing connection.\n"); + goto err; + } + if (conn->mode == LSN_SOCKS_CLIENT) { /* Construct SOCKS state. */ conn->socks_state = socks_state_new(); diff --git a/src/network.h b/src/network.h index 619e45f..1e13cb4 100644 --- a/src/network.h +++ b/src/network.h @@ -28,7 +28,7 @@ listener_t *listener_new( int mode, int protocol, const struct sockaddr *on_address, int on_address_len, const struct sockaddr *target_address, int target_address_len, - const char *shared_secret, size_t shared_secret_len); + const char *shared_secret); void listener_free(listener_t *listener); #ifdef NETWORK_PRIVATE diff --git a/src/protocol.c b/src/protocol.c index 1fbd3f7..b371923 100644 --- a/src/protocol.c +++ b/src/protocol.c @@ -31,7 +31,7 @@ set_up_protocol(int protocol) { Return the protocol_t if successful, NULL otherwise. */ struct protocol_t * -proto_new(int protocol, int is_initiator) { +proto_new(int protocol, struct protocol_params_t *params) { struct protocol_t *proto = calloc(1, sizeof(struct protocol_t)); if (!proto) return NULL; @@ -42,10 +42,10 @@ proto_new(int protocol, int is_initiator) { if (protocol == OBFS2_PROTOCOL) { proto->proto = protocol; - proto->state = obfs2_new(proto, is_initiator); + proto->state = obfs2_new(proto, params->is_initiator, params->shared_secret); } else if (protocol == DUMMY_PROTOCOL) { proto->proto = protocol; - proto->state = dummy_new(proto, is_initiator); + proto->state = dummy_new(proto, 666, NULL); } if (proto->state) diff --git a/src/protocol.h b/src/protocol.h index dd34585..7d0fb44 100644 --- a/src/protocol.h +++ b/src/protocol.h @@ -6,12 +6,16 @@ struct evbuffer; -int set_up_protocol(int protocol); -struct protocol_t *proto_new(int protocol, int arg); -void proto_destroy(struct protocol_t *proto); -int proto_handshake(struct protocol_t *proto, void *buf); -int proto_send(struct protocol_t *proto, void *source, void *dest); -int proto_recv(struct protocol_t *proto, void *source, void *dest); +struct protocol_t { + /* protocol */ + int proto; + + /* protocol vtable */ + struct protocol_vtable *vtable; + + /* ASN do we need a proto_get_state()? */ + void *state; +}; typedef struct protocol_vtable { @@ -22,7 +26,7 @@ typedef struct protocol_vtable { /* Constructor: Creates a protocol object. */ void *(*create)(struct protocol_t *proto_struct, - int is_initiator); + int is_initiator, const char *parameters); /* does handshake. Not all protocols have a handshake. */ int (*handshake)(void *state, @@ -37,17 +41,21 @@ typedef struct protocol_vtable { int (*recv)(void *state, struct evbuffer *source, struct evbuffer *dest); -} protocol_vtable; -struct protocol_t { - /* protocol */ - int proto; - - /* protocol vtable */ - protocol_vtable *vtable; +} protocol_vtable; - /* ASN do we need a proto_get_state()? */ - void *state; +struct protocol_params_t { + int is_initiator; + + const char *shared_secret; }; +int set_up_protocol(int protocol); +struct protocol_t *proto_new(int protocol, + struct protocol_params_t *params); +void proto_destroy(struct protocol_t *proto); +int proto_handshake(struct protocol_t *proto, void *buf); +int proto_send(struct protocol_t *proto, void *source, void *dest); +int proto_recv(struct protocol_t *proto, void *source, void *dest); + #endif diff --git a/src/protocols/dummy.c b/src/protocols/dummy.c index 8fe722e..f5a7558 100644 --- a/src/protocols/dummy.c +++ b/src/protocols/dummy.c @@ -36,8 +36,10 @@ dummy_init(void) { } void * -dummy_new(struct protocol_t *proto_struct, int whatever) { +dummy_new(struct protocol_t *proto_struct, int whatever, + const char *whatever2) { (void)whatever; + (void)whatever2; proto_struct->vtable = vtable; diff --git a/src/protocols/dummy.h b/src/protocols/dummy.h index 241366d..5ab39a4 100644 --- a/src/protocols/dummy.h +++ b/src/protocols/dummy.h @@ -5,6 +5,6 @@ struct protocol_t; struct evbuffer; int dummy_init(void); -void *dummy_new(struct protocol_t *proto_struct, int whatever); +void *dummy_new(struct protocol_t *proto_struct, int whatever, const char* whatever2); #endif diff --git a/src/protocols/obfs2.c b/src/protocols/obfs2.c index cac7bb2..aba8ea9 100644 --- a/src/protocols/obfs2.c +++ b/src/protocols/obfs2.c @@ -26,7 +26,9 @@ static int obfs2_send(void *state, struct evbuffer *source, struct evbuffer *dest); static int obfs2_recv(void *state, struct evbuffer *source, struct evbuffer *dest); -static void *obfs2_state_new(int initiator); +static void *obfs2_state_new(int initiator, const char *shared_secret); +static int obfs2_state_set_shared_secret(void *s, + const char *secret); static protocol_vtable *vtable=NULL; @@ -113,11 +115,11 @@ derive_padding_key(void *s, const uchar *seed, } void * -obfs2_new(struct protocol_t *proto_struct, int initiator) { +obfs2_new(struct protocol_t *proto_struct, int initiator, const char *shared_secret) { assert(vtable); proto_struct->vtable = vtable; - return obfs2_state_new(initiator); + return obfs2_state_new(initiator, shared_secret); } /** @@ -126,7 +128,7 @@ obfs2_new(struct protocol_t *proto_struct, int initiator) { NULL on failure. */ static void * -obfs2_state_new(int initiator) +obfs2_state_new(int initiator, const char *shared_secret) { obfs2_state_t *state = calloc(1, sizeof(obfs2_state_t)); uchar *seed; @@ -150,6 +152,9 @@ obfs2_state_new(int initiator) return NULL; } + if (shared_secret) + obfs2_state_set_shared_secret(state, shared_secret); + /* Derive the key for what we're sending */ state->send_padding_crypto = derive_padding_key(state, seed, send_pad_type); if (state->send_padding_crypto == NULL) { @@ -161,15 +166,25 @@ obfs2_state_new(int initiator) } /** Set the shared secret to be used with this protocol state. */ -void +static int obfs2_state_set_shared_secret(void *s, - const char *secret, size_t secretlen) + const char *secret) { + assert(secret); obfs2_state_t *state = s; + size_t secretlen = strlen(secret); - if (secretlen > SHARED_SECRET_LENGTH) + if (secretlen < SHARED_SECRET_LENGTH) { + printf("Shared secrets must be at least 16 bytes.\n"); /* Why? */ + return -1; + } else if (secretlen > SHARED_SECRET_LENGTH) secretlen = SHARED_SECRET_LENGTH; + memcpy(state->secret_seed, secret, secretlen); + + /* free(secret); */ + + return 0; } /** @@ -232,7 +247,6 @@ crypt_and_transmit(crypt_t *crypto, if (n <= 0) return 0; stream_crypt(crypto, data, n); - // printf("Message is: %s", data); evbuffer_add(dest, data, n); dbg(("Processed %d bytes.", n)); } diff --git a/src/protocols/obfs2.h b/src/protocols/obfs2.h index 3124bbc..bcc423f 100644 --- a/src/protocols/obfs2.h +++ b/src/protocols/obfs2.h @@ -16,10 +16,8 @@ struct protocol_t; #define SHARED_SECRET_LENGTH 16 -void obfs2_state_set_shared_secret(void *state, - const char *secret, size_t secretlen); int obfs2_init(void); -void *obfs2_new(struct protocol_t *proto_struct, int initiator); +void *obfs2_new(struct protocol_t *proto_struct, int initiator, const char *parameters); #ifdef CRYPT_PROTOCOL_PRIVATE diff --git a/src/test/unittest.c b/src/test/unittest.c index 41159ca..9ca6a74 100644 --- a/src/test/unittest.c +++ b/src/test/unittest.c @@ -15,7 +15,7 @@ extern struct testcase_t socks_tests[]; struct testgroup_t groups[] = { { "crypt/", crypt_tests }, - { "proto/", protocol_tests }, + /* { "proto/", protocol_tests }, */ { "socks/", socks_tests }, END_OF_GROUPS }; diff --git a/src/test/unittest_obfs2.c b/src/test/unittest_obfs2.c index f006b2f..ce743c8 100644 --- a/src/test/unittest_obfs2.c +++ b/src/test/unittest_obfs2.c @@ -1,3 +1,4 @@ +#if 0 /* Copyright 2011 Nick Mathewson You may do anything with this work that copyright law would normally @@ -474,3 +475,4 @@ struct testcase_t protocol_tests[] = { T(wrong_handshake_plength, 0), END_OF_TESTCASES }; +#endif

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[obfsproxy/master] Improved shared secret support based on the comments of my Mentor in #3202.
by nickm＠torproject.org 28 May '11

28 May '11

commit 536e014a102d283f668dbfd75bdd56de2728bc87 Author: George Kadianakis <desnacked(a)gmail.com> Date: Tue May 24 16:06:33 2011 +0200 Improved shared secret support based on the comments of my Mentor in #3202. Specifically: * We stop stupidly treating the shared secret as a C-string. We now instead hash it. We don't iteratively hash it yet. * Because of hashing the shared secret, we now allow shared secrets of arbitrary length. * We now pass protocol_params_t structs to the _new protocol methods. It looks/is much nicer. * I better defined the role of the protocol_params_t struct and is now attached to the listener_t struct. This is not done yet. --- src/main.c | 2 +- src/network.c | 32 +++++++++++++++++++++----------- src/network.h | 2 +- src/protocol.c | 4 ++-- src/protocol.h | 33 +++++++++++++++++++++++++-------- src/protocols/dummy.c | 8 +++----- src/protocols/dummy.h | 3 ++- src/protocols/obfs2.c | 46 ++++++++++++++++++++++++++-------------------- src/protocols/obfs2.h | 7 +++++-- 9 files changed, 86 insertions(+), 51 deletions(-) diff --git a/src/main.c b/src/main.c index 1c084d3..59b6909 100644 --- a/src/main.c +++ b/src/main.c @@ -128,7 +128,7 @@ main(int argc, const char **argv) mode, protocol, (struct sockaddr *)&ss_listen, sl_listen, sa_target, sl_target, - shared_secret); + shared_secret, strlen(shared_secret)); if (! listener) { printf("Couldn't create listener!\n"); return 4; diff --git a/src/network.c b/src/network.c index a32cb1d..07efbc4 100644 --- a/src/network.c +++ b/src/network.c @@ -27,10 +27,9 @@ struct listener_t { struct evconnlistener *listener; struct sockaddr_storage target_address; int target_address_len; - int proto; /* Protocol that this listener can speak. */ int mode; - const char *shared_secret; - unsigned int have_shared_secret : 1; + int proto; /* Protocol that this listener can speak. */ + struct protocol_params_t *proto_params; }; static void simple_listener_cb(struct evconnlistener *evcl, @@ -52,7 +51,7 @@ listener_new(struct event_base *base, int mode, int protocol, const struct sockaddr *on_address, int on_address_len, const struct sockaddr *target_address, int target_address_len, - const char *shared_secret) + const char *shared_secret, size_t shared_secret_len) { const unsigned flags = LEV_OPT_CLOSE_ON_FREE|LEV_OPT_CLOSE_ON_EXEC|LEV_OPT_REUSEABLE; @@ -68,8 +67,13 @@ listener_new(struct event_base *base, lsn->proto = protocol; lsn->mode = mode; - lsn->shared_secret = shared_secret; - lsn->have_shared_secret = 1; + + struct protocol_params_t *proto_params = calloc(1, sizeof(struct protocol_params_t)); + proto_params->is_initiator = mode != LSN_SIMPLE_SERVER; + proto_params->shared_secret = shared_secret; + proto_params->shared_secret_len = shared_secret_len; + + lsn->proto_params = proto_params; if (target_address) { assert(target_address_len <= sizeof(struct sockaddr_storage)); @@ -92,11 +96,21 @@ listener_new(struct event_base *base, return lsn; } +static void +protocol_params_free(struct protocol_params_t *params) +{ + assert(params); + if (params->shared_secret) + free(&params->shared_secret); +} + void listener_free(listener_t *lsn) { if (lsn->listener) evconnlistener_free(lsn->listener); + if (lsn->proto_params) + protocol_params_free(lsn->proto_params); memset(lsn, 0xb0, sizeof(listener_t)); free(lsn); } @@ -115,12 +129,8 @@ simple_listener_cb(struct evconnlistener *evcl, conn->mode = lsn->mode; - struct protocol_params_t *proto_params = calloc(1, sizeof(struct protocol_params_t)); - proto_params->is_initiator = conn->mode != LSN_SIMPLE_SERVER; - proto_params->shared_secret = lsn->shared_secret; - conn->proto = proto_new(lsn->proto, - proto_params); + lsn->proto_params); if (!conn->proto) { printf("Creation of protocol object failed! Closing connection.\n"); goto err; diff --git a/src/network.h b/src/network.h index 1e13cb4..619e45f 100644 --- a/src/network.h +++ b/src/network.h @@ -28,7 +28,7 @@ listener_t *listener_new( int mode, int protocol, const struct sockaddr *on_address, int on_address_len, const struct sockaddr *target_address, int target_address_len, - const char *shared_secret); + const char *shared_secret, size_t shared_secret_len); void listener_free(listener_t *listener); #ifdef NETWORK_PRIVATE diff --git a/src/protocol.c b/src/protocol.c index b371923..4e6ae81 100644 --- a/src/protocol.c +++ b/src/protocol.c @@ -42,10 +42,10 @@ proto_new(int protocol, struct protocol_params_t *params) { if (protocol == OBFS2_PROTOCOL) { proto->proto = protocol; - proto->state = obfs2_new(proto, params->is_initiator, params->shared_secret); + proto->state = obfs2_new(proto, params); } else if (protocol == DUMMY_PROTOCOL) { proto->proto = protocol; - proto->state = dummy_new(proto, 666, NULL); + proto->state = dummy_new(proto, NULL); } if (proto->state) diff --git a/src/protocol.h b/src/protocol.h index 7d0fb44..6b609ee 100644 --- a/src/protocol.h +++ b/src/protocol.h @@ -6,14 +6,37 @@ struct evbuffer; +/** + This struct defines parameters of the protocol per-listener basis. + + By 'per-listener basis' I mean that the parameters defined here will + be inherited by *all* connections opened from the listener_t that + owns this protocol_params_t. +*/ +struct protocol_params_t { +int is_initiator; + + const char *shared_secret; + size_t shared_secret_len; +}; + struct protocol_t { /* protocol */ int proto; /* protocol vtable */ struct protocol_vtable *vtable; + + /* This protocol specific struct defines the state of the protocol + per-connection basis. - /* ASN do we need a proto_get_state()? */ + By 'protocol specific' I mean that every protocol has it's own + state struct. (for example, obfs2 has obfs2_state_t) + + By 'per-connection basis' I mean that the every connection has a + different protocol_t struct, and that's precisely the reason that + this struct is owned by the conn_t struct. + */ void *state; }; @@ -26,7 +49,7 @@ typedef struct protocol_vtable { /* Constructor: Creates a protocol object. */ void *(*create)(struct protocol_t *proto_struct, - int is_initiator, const char *parameters); + struct protocol_params_t *parameters); /* does handshake. Not all protocols have a handshake. */ int (*handshake)(void *state, @@ -44,12 +67,6 @@ typedef struct protocol_vtable { } protocol_vtable; -struct protocol_params_t { - int is_initiator; - - const char *shared_secret; -}; - int set_up_protocol(int protocol); struct protocol_t *proto_new(int protocol, struct protocol_params_t *params); diff --git a/src/protocols/dummy.c b/src/protocols/dummy.c index f5a7558..79d40e0 100644 --- a/src/protocols/dummy.c +++ b/src/protocols/dummy.c @@ -36,11 +36,9 @@ dummy_init(void) { } void * -dummy_new(struct protocol_t *proto_struct, int whatever, - const char *whatever2) { - (void)whatever; - (void)whatever2; - +dummy_new(struct protocol_t *proto_struct, + struct protocol_params_t *params) +{ proto_struct->vtable = vtable; /* Dodging state check. diff --git a/src/protocols/dummy.h b/src/protocols/dummy.h index 5ab39a4..1ee0e02 100644 --- a/src/protocols/dummy.h +++ b/src/protocols/dummy.h @@ -3,8 +3,9 @@ struct protocol_t; struct evbuffer; +struct protocol_params_t; int dummy_init(void); -void *dummy_new(struct protocol_t *proto_struct, int whatever, const char* whatever2); +void *dummy_new(struct protocol_t *proto_struct, struct protocol_params_t *params); #endif diff --git a/src/protocols/obfs2.c b/src/protocols/obfs2.c index fe50553..277ca63 100644 --- a/src/protocols/obfs2.c +++ b/src/protocols/obfs2.c @@ -26,9 +26,10 @@ static int obfs2_send(void *state, struct evbuffer *source, struct evbuffer *dest); static int obfs2_recv(void *state, struct evbuffer *source, struct evbuffer *dest); -static void *obfs2_state_new(int initiator, const char *shared_secret); +static void *obfs2_state_new(struct protocol_params_t *params); static int obfs2_state_set_shared_secret(void *s, - const char *secret); + const char *secret, + size_t secretlen); static protocol_vtable *vtable=NULL; @@ -115,11 +116,13 @@ derive_padding_key(void *s, const uchar *seed, } void * -obfs2_new(struct protocol_t *proto_struct, int initiator, const char *shared_secret) { +obfs2_new(struct protocol_t *proto_struct, + struct protocol_params_t *params) +{ assert(vtable); proto_struct->vtable = vtable; - return obfs2_state_new(initiator, shared_secret); + return obfs2_state_new(params); } /** @@ -128,7 +131,7 @@ obfs2_new(struct protocol_t *proto_struct, int initiator, const char *shared_sec NULL on failure. */ static void * -obfs2_state_new(int initiator, const char *shared_secret) +obfs2_state_new(struct protocol_params_t *params) { obfs2_state_t *state = calloc(1, sizeof(obfs2_state_t)); uchar *seed; @@ -137,8 +140,8 @@ obfs2_state_new(int initiator, const char *shared_secret) if (!state) return NULL; state->state = ST_WAIT_FOR_KEY; - state->we_are_initiator = initiator; - if (initiator) { + state->we_are_initiator = params->is_initiator; + if (state->we_are_initiator) { send_pad_type = INITIATOR_PAD_TYPE; seed = state->initiator_seed; } else { @@ -152,8 +155,10 @@ obfs2_state_new(int initiator, const char *shared_secret) return NULL; } - if (shared_secret) - if (obfs2_state_set_shared_secret(state, shared_secret)<0) + if (params->shared_secret) + if (obfs2_state_set_shared_secret(state, + params->shared_secret, + params->shared_secret_len)<0) return NULL; /* Derive the key for what we're sending */ @@ -168,22 +173,23 @@ obfs2_state_new(int initiator, const char *shared_secret) /** Set the shared secret to be used with this protocol state. */ static int -obfs2_state_set_shared_secret(void *s, - const char *secret) +obfs2_state_set_shared_secret(void *s, const char *secret, + size_t secretlen) { assert(secret); - obfs2_state_t *state = s; - size_t secretlen = strlen(secret); + assert(secretlen); - if (secretlen < SHARED_SECRET_LENGTH) { - printf("Shared secrets must be at least 16 bytes.\n"); /* Why? */ - return -1; - } else if (secretlen > SHARED_SECRET_LENGTH) - secretlen = SHARED_SECRET_LENGTH; + uchar buf[SHARED_SECRET_LENGTH]; + obfs2_state_t *state = s; - memcpy(state->secret_seed, secret, secretlen); + digest_t *c = digest_new(); + /* ASN do we like this cast here? */ + digest_update(c, (uchar*)secret, secretlen); + digest_getdigest(c, buf, sizeof(buf)); + memcpy(state->secret_seed, buf, SHARED_SECRET_LENGTH); - /* free(secret); */ + memset(buf,0,SHARED_SECRET_LENGTH); + digest_free(c); return 0; } diff --git a/src/protocols/obfs2.h b/src/protocols/obfs2.h index bcc423f..bc8a22d 100644 --- a/src/protocols/obfs2.h +++ b/src/protocols/obfs2.h @@ -13,11 +13,14 @@ typedef struct obfs2_state_t obfs2_state_t; struct evbuffer; struct protocol_t; +struct protocol_params_t; -#define SHARED_SECRET_LENGTH 16 +#define SHA256_LENGTH 32 +#define SHARED_SECRET_LENGTH SHA256_LENGTH int obfs2_init(void); -void *obfs2_new(struct protocol_t *proto_struct, int initiator, const char *parameters); +void *obfs2_new(struct protocol_t *proto_struct, + struct protocol_params_t *params); #ifdef CRYPT_PROTOCOL_PRIVATE

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[obfsproxy/master] Small fix.
by nickm＠torproject.org 28 May '11

28 May '11

commit 5eafc3f2382b5c7ee5115005b887dbe51695fd23 Author: George Kadianakis <desnacked(a)gmail.com> Date: Tue May 17 23:33:42 2011 +0200 Small fix. --- src/protocols/obfs2.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/src/protocols/obfs2.c b/src/protocols/obfs2.c index aba8ea9..fe50553 100644 --- a/src/protocols/obfs2.c +++ b/src/protocols/obfs2.c @@ -153,7 +153,8 @@ obfs2_state_new(int initiator, const char *shared_secret) } if (shared_secret) - obfs2_state_set_shared_secret(state, shared_secret); + if (obfs2_state_set_shared_secret(state, shared_secret)<0) + return NULL; /* Derive the key for what we're sending */ state->send_padding_crypto = derive_padding_key(state, seed, send_pad_type);

1 0

[obfsproxy/master] Killed some magic numbers and replaced them with SHA256_LENGTH.
by nickm＠torproject.org 28 May '11

28 May '11

commit 4f55412fbf663977faf26847f6425ce5e4ea2f7b Author: George Kadianakis <desnacked(a)gmail.com> Date: Tue May 24 23:52:10 2011 +0200 Killed some magic numbers and replaced them with SHA256_LENGTH. --- src/protocols/obfs2.c | 4 ++-- src/protocols/obfs2.h | 1 - src/protocols/obfs2_crypt.c | 4 ++-- src/protocols/obfs2_crypt.h | 2 ++ 4 files changed, 6 insertions(+), 5 deletions(-) diff --git a/src/protocols/obfs2.c b/src/protocols/obfs2.c index 1377dfe..3490d0e 100644 --- a/src/protocols/obfs2.c +++ b/src/protocols/obfs2.c @@ -74,7 +74,7 @@ derive_key(void *s, const char *keytype) obfs2_state_t *state = s; crypt_t *cryptstate; - uchar buf[32]; + uchar buf[SHA256_LENGTH]; digest_t *c = digest_new(); digest_update(c, (uchar*)keytype, strlen(keytype)); if (seed_nonzero(state->initiator_seed)) @@ -99,7 +99,7 @@ derive_padding_key(void *s, const uchar *seed, obfs2_state_t *state = s; crypt_t *cryptstate; - uchar buf[32]; + uchar buf[SHA256_LENGTH]; digest_t *c = digest_new(); digest_update(c, (uchar*)keytype, strlen(keytype)); if (seed_nonzero(seed)) diff --git a/src/protocols/obfs2.h b/src/protocols/obfs2.h index bc8a22d..1f9f31d 100644 --- a/src/protocols/obfs2.h +++ b/src/protocols/obfs2.h @@ -15,7 +15,6 @@ struct evbuffer; struct protocol_t; struct protocol_params_t; -#define SHA256_LENGTH 32 #define SHARED_SECRET_LENGTH SHA256_LENGTH int obfs2_init(void); diff --git a/src/protocols/obfs2_crypt.c b/src/protocols/obfs2_crypt.c index 0121c93..50d094c 100644 --- a/src/protocols/obfs2_crypt.c +++ b/src/protocols/obfs2_crypt.c @@ -109,7 +109,7 @@ digest_update(digest_t *d, const uchar *buf, size_t len) size_t digest_getdigest(digest_t *d, uchar *buf, size_t len) { - uchar tmp[32]; + uchar tmp[SHA256_LENGTH]; int n = 32; SHA256_Final(tmp, &d->ctx); if (len < 32) @@ -137,7 +137,7 @@ digest_update(digest_t *d, const uchar *buf, size_t len) size_t digest_getdigest(digest_t *d, uchar *buf, size_t len) { - uchar tmp[32]; + uchar tmp[SHA256_LENGTH]; int n = 32; sha256_done(&d->ctx, tmp); if (len < 32) diff --git a/src/protocols/obfs2_crypt.h b/src/protocols/obfs2_crypt.h index c9841d8..ef279e9 100644 --- a/src/protocols/obfs2_crypt.h +++ b/src/protocols/obfs2_crypt.h @@ -10,6 +10,8 @@ #include <sys/types.h> +#define SHA256_LENGTH 32 + /* Stream cipher state */ typedef struct crypt_t crypt_t; /* Digest state */

1 0

[obfsproxy/master] Trivial improvements over the code:
by nickm＠torproject.org 28 May '11

28 May '11

commit 75ecf16d8342a34357ef39b3fe339590097896fd Author: George Kadianakis <desnacked(a)gmail.com> Date: Tue May 24 22:32:47 2011 +0200 Trivial improvements over the code: * typedef'ed protocol_params_t * we now also free() the protocol_params_t itself in protocol_params_free(). --- src/network.c | 7 ++++--- src/protocol.c | 2 +- src/protocol.h | 10 +++++----- src/protocols/dummy.c | 2 +- src/protocols/obfs2.c | 8 ++++---- 5 files changed, 15 insertions(+), 14 deletions(-) diff --git a/src/network.c b/src/network.c index 07efbc4..a2dc410 100644 --- a/src/network.c +++ b/src/network.c @@ -29,7 +29,7 @@ struct listener_t { int target_address_len; int mode; int proto; /* Protocol that this listener can speak. */ - struct protocol_params_t *proto_params; + protocol_params_t *proto_params; }; static void simple_listener_cb(struct evconnlistener *evcl, @@ -68,7 +68,7 @@ listener_new(struct event_base *base, lsn->proto = protocol; lsn->mode = mode; - struct protocol_params_t *proto_params = calloc(1, sizeof(struct protocol_params_t)); + protocol_params_t *proto_params = calloc(1, sizeof(protocol_params_t)); proto_params->is_initiator = mode != LSN_SIMPLE_SERVER; proto_params->shared_secret = shared_secret; proto_params->shared_secret_len = shared_secret_len; @@ -97,11 +97,12 @@ listener_new(struct event_base *base, } static void -protocol_params_free(struct protocol_params_t *params) +protocol_params_free(protocol_params_t *params) { assert(params); if (params->shared_secret) free(&params->shared_secret); + free(params); } void diff --git a/src/protocol.c b/src/protocol.c index 4e6ae81..8fff6a3 100644 --- a/src/protocol.c +++ b/src/protocol.c @@ -31,7 +31,7 @@ set_up_protocol(int protocol) { Return the protocol_t if successful, NULL otherwise. */ struct protocol_t * -proto_new(int protocol, struct protocol_params_t *params) { +proto_new(int protocol, protocol_params_t *params) { struct protocol_t *proto = calloc(1, sizeof(struct protocol_t)); if (!proto) return NULL; diff --git a/src/protocol.h b/src/protocol.h index 6b609ee..e4c3e0f 100644 --- a/src/protocol.h +++ b/src/protocol.h @@ -13,12 +13,12 @@ struct evbuffer; be inherited by *all* connections opened from the listener_t that owns this protocol_params_t. */ -struct protocol_params_t { -int is_initiator; +typedef struct protocol_params_t { + int is_initiator; const char *shared_secret; size_t shared_secret_len; -}; +} protocol_params_t; struct protocol_t { /* protocol */ @@ -49,7 +49,7 @@ typedef struct protocol_vtable { /* Constructor: Creates a protocol object. */ void *(*create)(struct protocol_t *proto_struct, - struct protocol_params_t *parameters); + protocol_params_t *parameters); /* does handshake. Not all protocols have a handshake. */ int (*handshake)(void *state, @@ -69,7 +69,7 @@ typedef struct protocol_vtable { int set_up_protocol(int protocol); struct protocol_t *proto_new(int protocol, - struct protocol_params_t *params); + protocol_params_t *params); void proto_destroy(struct protocol_t *proto); int proto_handshake(struct protocol_t *proto, void *buf); int proto_send(struct protocol_t *proto, void *source, void *dest); diff --git a/src/protocols/dummy.c b/src/protocols/dummy.c index 79d40e0..482c927 100644 --- a/src/protocols/dummy.c +++ b/src/protocols/dummy.c @@ -37,7 +37,7 @@ dummy_init(void) { void * dummy_new(struct protocol_t *proto_struct, - struct protocol_params_t *params) + protocol_params_t *params) { proto_struct->vtable = vtable; diff --git a/src/protocols/obfs2.c b/src/protocols/obfs2.c index 277ca63..1377dfe 100644 --- a/src/protocols/obfs2.c +++ b/src/protocols/obfs2.c @@ -26,7 +26,7 @@ static int obfs2_send(void *state, struct evbuffer *source, struct evbuffer *dest); static int obfs2_recv(void *state, struct evbuffer *source, struct evbuffer *dest); -static void *obfs2_state_new(struct protocol_params_t *params); +static void *obfs2_state_new(protocol_params_t *params); static int obfs2_state_set_shared_secret(void *s, const char *secret, size_t secretlen); @@ -117,7 +117,7 @@ derive_padding_key(void *s, const uchar *seed, void * obfs2_new(struct protocol_t *proto_struct, - struct protocol_params_t *params) + protocol_params_t *params) { assert(vtable); proto_struct->vtable = vtable; @@ -131,7 +131,7 @@ obfs2_new(struct protocol_t *proto_struct, NULL on failure. */ static void * -obfs2_state_new(struct protocol_params_t *params) +obfs2_state_new(protocol_params_t *params) { obfs2_state_t *state = calloc(1, sizeof(obfs2_state_t)); uchar *seed; @@ -183,9 +183,9 @@ obfs2_state_set_shared_secret(void *s, const char *secret, obfs2_state_t *state = s; digest_t *c = digest_new(); - /* ASN do we like this cast here? */ digest_update(c, (uchar*)secret, secretlen); digest_getdigest(c, buf, sizeof(buf)); + memcpy(state->secret_seed, buf, SHARED_SECRET_LENGTH); memset(buf,0,SHARED_SECRET_LENGTH);

1 0

[obfsproxy/master] Added a warning in obfs2_recv() since we are sending pending data on
by nickm＠torproject.org 28 May '11

28 May '11

commit ad09a5176ed9a7d171ffe7a98ef36801767b08db Author: George Kadianakis <desnacked(a)gmail.com> Date: Thu May 26 00:36:50 2011 +0200 Added a warning in obfs2_recv() since we are sending pending data on the next obfs2_send() instead of sending them at the moment init_crypto() is done. --- src/protocols/obfs2.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/src/protocols/obfs2.c b/src/protocols/obfs2.c index b3fe590..a8f9155 100644 --- a/src/protocols/obfs2.c +++ b/src/protocols/obfs2.c @@ -398,6 +398,10 @@ obfs2_recv(void *s, struct evbuffer *source, if (plength > OBFUSCATE_MAX_PADDING) return -1; + /* XXX FIXME we should now be sending any 'pending_data_to_send' + but we can't send them from here, so we send them with + obfs2_send() when we next have to send data */ + /* Now we're waiting for plength bytes of padding */ state->padding_left_to_read = plength; state->state = ST_WAIT_FOR_PADDING;

1 0

[obfsproxy/master] Fixed stupid bug.
by nickm＠torproject.org 28 May '11

28 May '11

commit 35abc50a3646d6165ba7f3e9ac0efd218bb0e162 Author: George Kadianakis <desnacked(a)gmail.com> Date: Wed May 25 04:51:51 2011 +0200 Fixed stupid bug. --- src/protocols/obfs2.c | 16 ++++++++-------- 1 files changed, 8 insertions(+), 8 deletions(-) diff --git a/src/protocols/obfs2.c b/src/protocols/obfs2.c index 6221bb2..4159691 100644 --- a/src/protocols/obfs2.c +++ b/src/protocols/obfs2.c @@ -290,13 +290,20 @@ obfs2_send(void *s, obfs2_state_t *state = s; if (state->send_crypto) { + /* First of all, send any data that we've been waiting to send. */ + if (state->pending_data_to_send) { + crypt_and_transmit(state->send_crypto, state->pending_data_to_send, dest); + evbuffer_free(state->pending_data_to_send); + state->pending_data_to_send = NULL; + } /* Our crypto is set up; just relay the bytes */ return crypt_and_transmit(state->send_crypto, source, dest); } else { /* Our crypto isn't set up yet, we'll have to queue the data */ if (evbuffer_get_length(source)) { if (! state->pending_data_to_send) { - state->pending_data_to_send = evbuffer_new(); + if ((state->pending_data_to_send = evbuffer_new()) == NULL) + return -1; } evbuffer_add_buffer(state->pending_data_to_send, source); } @@ -387,13 +394,6 @@ obfs2_recv(void *s, struct evbuffer *source, if (plength > OBFUSCATE_MAX_PADDING) return -1; - /* Send any data that we've been waiting to send */ - if (state->pending_data_to_send) { - crypt_and_transmit(state->send_crypto, state->pending_data_to_send, dest); - evbuffer_free(state->pending_data_to_send); - state->pending_data_to_send = NULL; - } - /* Now we're waiting for plength bytes of padding */ state->padding_left_to_read = plength; state->state = ST_WAIT_FOR_PADDING;

1 0

[obfsproxy/master] Revived unit tests.
by nickm＠torproject.org 28 May '11

28 May '11

commit 9d2e98860ed5c0e5f6a6a45869a20732a0a01218 Author: George Kadianakis <desnacked(a)gmail.com> Date: Wed May 25 04:10:23 2011 +0200 Revived unit tests. --- src/test/unittest.c | 2 +- src/test/unittest_obfs2.c | 99 ++++++++++++++++++++++++++++++++++++++------ 2 files changed, 86 insertions(+), 15 deletions(-) diff --git a/src/test/unittest.c b/src/test/unittest.c index 9ca6a74..41159ca 100644 --- a/src/test/unittest.c +++ b/src/test/unittest.c @@ -15,7 +15,7 @@ extern struct testcase_t socks_tests[]; struct testgroup_t groups[] = { { "crypt/", crypt_tests }, - /* { "proto/", protocol_tests }, */ + { "proto/", protocol_tests }, { "socks/", socks_tests }, END_OF_GROUPS }; diff --git a/src/test/unittest_obfs2.c b/src/test/unittest_obfs2.c index ce743c8..052c909 100644 --- a/src/test/unittest_obfs2.c +++ b/src/test/unittest_obfs2.c @@ -1,4 +1,3 @@ -#if 0 /* Copyright 2011 Nick Mathewson You may do anything with this work that copyright law would normally @@ -32,8 +31,20 @@ test_proto_setup(void *data) tt_assert(set_up_protocol(OBFS2_PROTOCOL) >= 0); - client_proto = proto_new(OBFS2_PROTOCOL,1); - server_proto = proto_new(OBFS2_PROTOCOL,1); + protocol_params_t *proto_params_serv = calloc(1, sizeof(protocol_params_t)); + tt_assert(proto_params_serv); + proto_params_serv->is_initiator = 1; + proto_params_serv->shared_secret = "hahaha"; + proto_params_serv->shared_secret_len = 7; + + protocol_params_t *proto_params_client = calloc(1, sizeof(protocol_params_t)); + tt_assert(proto_params_client); + proto_params_client->is_initiator = 0; + proto_params_client->shared_secret = "hahaha"; + proto_params_client->shared_secret_len = 7; + + client_proto = proto_new(OBFS2_PROTOCOL,proto_params_serv); + server_proto = proto_new(OBFS2_PROTOCOL,proto_params_client); tt_assert(client_proto); tt_assert(server_proto); @@ -61,8 +72,20 @@ test_proto_handshake(void *data) tt_assert(set_up_protocol(OBFS2_PROTOCOL) >= 0); - client_proto = proto_new(OBFS2_PROTOCOL,1); - server_proto = proto_new(OBFS2_PROTOCOL,0); + protocol_params_t *proto_params_serv = calloc(1, sizeof(protocol_params_t)); + tt_assert(proto_params_serv); + proto_params_serv->is_initiator = 1; + proto_params_serv->shared_secret = "hahaha"; + proto_params_serv->shared_secret_len = 7; + + protocol_params_t *proto_params_client = calloc(1, sizeof(protocol_params_t)); + tt_assert(proto_params_client); + proto_params_client->is_initiator = 0; + proto_params_client->shared_secret = "hahaha"; + proto_params_client->shared_secret_len = 7; + + client_proto = proto_new(OBFS2_PROTOCOL,proto_params_serv); + server_proto = proto_new(OBFS2_PROTOCOL,proto_params_client); tt_assert(client_proto); tt_assert(server_proto); @@ -121,8 +144,20 @@ test_proto_transfer(void *data) tt_assert(set_up_protocol(OBFS2_PROTOCOL) >= 0); - client_proto = proto_new(OBFS2_PROTOCOL,1); - server_proto = proto_new(OBFS2_PROTOCOL,0); + protocol_params_t *proto_params_serv = calloc(1, sizeof(protocol_params_t)); + tt_assert(proto_params_serv); + proto_params_serv->is_initiator = 1; + proto_params_serv->shared_secret = "hahaha"; + proto_params_serv->shared_secret_len = 7; + + protocol_params_t *proto_params_client = calloc(1, sizeof(protocol_params_t)); + tt_assert(proto_params_client); + proto_params_client->is_initiator = 0; + proto_params_client->shared_secret = "hahaha"; + proto_params_client->shared_secret_len = 7; + + client_proto = proto_new(OBFS2_PROTOCOL,proto_params_serv); + server_proto = proto_new(OBFS2_PROTOCOL,proto_params_client); tt_assert(client_proto); tt_assert(server_proto); @@ -204,9 +239,21 @@ test_proto_splitted_handshake(void *data) struct protocol_t *server_proto = NULL; tt_assert(set_up_protocol(OBFS2_PROTOCOL) >= 0); + + protocol_params_t *proto_params_serv = calloc(1, sizeof(protocol_params_t)); + tt_assert(proto_params_serv); + proto_params_serv->is_initiator = 1; + proto_params_serv->shared_secret = "hahaha"; + proto_params_serv->shared_secret_len = 7; - client_proto = proto_new(OBFS2_PROTOCOL,1); - server_proto = proto_new(OBFS2_PROTOCOL,0); + protocol_params_t *proto_params_client = calloc(1, sizeof(protocol_params_t)); + tt_assert(proto_params_client); + proto_params_client->is_initiator = 0; + proto_params_client->shared_secret = "hahaha"; + proto_params_client->shared_secret_len = 7; + + client_proto = proto_new(OBFS2_PROTOCOL,proto_params_serv); + server_proto = proto_new(OBFS2_PROTOCOL,proto_params_client); tt_assert(client_proto); tt_assert(server_proto); @@ -346,8 +393,20 @@ test_proto_wrong_handshake_magic(void *data) tt_assert(set_up_protocol(OBFS2_PROTOCOL) >= 0); - client_proto = proto_new(OBFS2_PROTOCOL,1); - server_proto = proto_new(OBFS2_PROTOCOL,0); + protocol_params_t *proto_params_serv = calloc(1, sizeof(protocol_params_t)); + tt_assert(proto_params_serv); + proto_params_serv->is_initiator = 1; + proto_params_serv->shared_secret = "hahaha"; + proto_params_serv->shared_secret_len = 7; + + protocol_params_t *proto_params_client = calloc(1, sizeof(protocol_params_t)); + tt_assert(proto_params_client); + proto_params_client->is_initiator = 0; + proto_params_client->shared_secret = "hahaha"; + proto_params_client->shared_secret_len = 7; + + client_proto = proto_new(OBFS2_PROTOCOL,proto_params_serv); + server_proto = proto_new(OBFS2_PROTOCOL,proto_params_client); tt_assert(client_proto); tt_assert(server_proto); @@ -413,8 +472,21 @@ test_proto_wrong_handshake_plength(void *data) tt_assert(set_up_protocol(OBFS2_PROTOCOL) >= 0); - client_proto = proto_new(OBFS2_PROTOCOL,1); - server_proto = proto_new(OBFS2_PROTOCOL,0); + protocol_params_t *proto_params_serv = calloc(1, sizeof(protocol_params_t)); + tt_assert(proto_params_serv); + proto_params_serv->is_initiator = 1; + proto_params_serv->shared_secret = "hahaha"; + proto_params_serv->shared_secret_len = 7; + + protocol_params_t *proto_params_client = calloc(1, sizeof(protocol_params_t)); + tt_assert(proto_params_client); + proto_params_client->is_initiator = 0; + proto_params_client->shared_secret = "hahaha"; + proto_params_client->shared_secret_len = 7; + + + client_proto = proto_new(OBFS2_PROTOCOL,proto_params_serv); + server_proto = proto_new(OBFS2_PROTOCOL,proto_params_client); tt_assert(client_proto); tt_assert(server_proto); @@ -475,4 +547,3 @@ struct testcase_t protocol_tests[] = { T(wrong_handshake_plength, 0), END_OF_TESTCASES }; -#endif

1 0

[obfsproxy/master] Merge remote-tracking branch 'asn/shared_secret'
by nickm＠torproject.org 28 May '11

28 May '11

commit 9ef190a4d70cd44053dde4d19d5579a609ced091 Merge: 8ac51f3 ad09a51 Author: Nick Mathewson <nickm(a)torproject.org> Date: Sat May 28 21:34:22 2011 -0400 Merge remote-tracking branch 'asn/shared_secret' Conflicts: doc/protocol-spec.txt doc/protocol-spec.txt | 12 ++++-- src/main.c | 38 ++++++++++------- src/network.c | 43 +++++++++++-------- src/protocol.c | 6 +- src/protocol.h | 59 ++++++++++++++++++-------- src/protocols/dummy.c | 6 +- src/protocols/dummy.h | 3 +- src/protocols/obfs2.c | 94 +++++++++++++++++++++++++++++++---------- src/protocols/obfs2.h | 9 ++-- src/protocols/obfs2_crypt.c | 4 +- src/protocols/obfs2_crypt.h | 2 + src/test/unittest_obfs2.c | 97 +++++++++++++++++++++++++++++++++++++----- 12 files changed, 272 insertions(+), 101 deletions(-) diff --cc doc/protocol-spec.txt index 471f2c0,798da14..c11f653 --- a/doc/protocol-spec.txt +++ b/doc/protocol-spec.txt @@@ -16,13 -16,15 +16,15 @@@ The Twobfuscato 1. Primitives, notation, and constants. - H(x) is SHA256 of X + H(x) is SHA256 of x. + H^n(x) is H(x) called iteratively n times. + - E_K(s) is the AES-counter-mode encryption of s using the key K. + E_K(s) is the AES-CTR-128 encryption of s using K as key. - x | y is the concatenation of x and y - UINT32(n) is the 4 byte value of n in big-endian (network) order - SR(n) is n bytes of strong random data - WR(n) is n bytes of weaker random data + x | y is the concatenation of x and y. + UINT32(n) is the 4 byte value of n in big-endian (network) order. + SR(n) is n bytes of strong random data. + WR(n) is n bytes of weaker random data. "xyz" is the ASCII characters 'x', 'y', and 'z', not NUL-terminated. s[:n] is the first n bytes of s. s[n:] is the last n bytes of s.

1 0

[obfsproxy/master] Implemented iterated hashing and updated the protocol spec.
by nickm＠torproject.org 28 May '11

28 May '11

commit d63d9d56a0da3a51aa7ec599635ec8a02ab0c8cb Author: George Kadianakis <desnacked(a)gmail.com> Date: Wed May 25 02:13:37 2011 +0200 Implemented iterated hashing and updated the protocol spec. --- doc/protocol-spec.txt | 28 ++++++++++++++++++---------- src/protocols/obfs2.c | 21 ++++++++++++++++++++- src/protocols/obfs2.h | 1 + 3 files changed, 39 insertions(+), 11 deletions(-) diff --git a/doc/protocol-spec.txt b/doc/protocol-spec.txt index 9a7d4fa..0f9edf9 100644 --- a/doc/protocol-spec.txt +++ b/doc/protocol-spec.txt @@ -27,9 +27,10 @@ The Twobfuscator s[:n] is the first n bytes of s. s[n:] is the last n bytes of s. - MAGIC_VALUE is 0x2BF5CA7E - SEED_LENGTH is 16 - MAX_PADDING is 8192 + MAGIC_VALUE is 0x2BF5CA7E + SEED_LENGTH is 16 + MAX_PADDING is 8192 + HASH_ITERATIONS is 100000 KEYLEN is the length of the key used by E_K(s) -- that is, 16. IVLEN is the length of the IV used by E_K(s) -- that is, 16 @@ -38,6 +39,9 @@ The Twobfuscator MAC(s, x) = H(s | x | s) + Let n = HASH_ITERATIONS through section '2. Key establishment phase.'. + Then, H^n(x) is H(x) called iteratively n times. + A "byte" is an 8-bit octet. We require that HASHLEN >= KEYLEN + IVLEN @@ -49,12 +53,14 @@ The Twobfuscator a padding key as follows. The initiator generates: INIT_SEED = SR(SEED_LENGTH) - INIT_PAD_KEY = MAC("Initiator obfuscation padding", INIT_SEED)[:KEYLEN] + INIT_PAD_TEMP = MAC("Initiator obfuscation padding", INIT_SEED)[:KEYLEN] + INIT_PAD_KEY = H^n(INIT_PAD_TEMP) And the responder generates: RESP_SEED = SR(SEED_LENGTH) - RESP_PAD_KEY = MAC("Responder obfuscation padding", INIT_SEED)[:KEYLEN] + RESP_PAD_TEMP = MAC("Responder obfuscation padding", INIT_SEED)[:KEYLEN] + RESP_PAD_KEY = H^n(RESP_PAD_TEMP) Each then generates a random number PADLEN in range from 0 through MAX_PADDING (inclusive), and sends: @@ -73,10 +79,12 @@ The Twobfuscator INIT_SECRET = MAC("Initiator obfuscated data", INIT_SEED|RESP_SEED) RESP_SECRET = MAC("Responder obfuscated data", INIT_SEED|RESP_SEED) - INIT_KEY = INIT_SECRET[:KEYLEN] - INIT_IV = INIT_SECRET[KEYLEN:] - RESP_KEY = RESP_SECRET[:KEYLEN] - RESP_IV = RESP_SECRET[KEYLEN:] + INIT_MASTER_KEY = H^n(INIT_SECRET) + RESP_MASTER_KEY = H^n(RESP_SECRET) + INIT_KEY = INIT_MASTER_KEY[:KEYLEN] + INIT_IV = INIT_MASTER_KEY[KEYLEN:] + RESP_KEY = RESP_MASTER_KEY[:KEYLEN] + RESP_IV = RESP_MASTER_KEY[KEYLEN:] The INIT_KEY value keys a stream cipher used to encrypt values from initiator to responder thereafter. The stream cipher's IV is @@ -89,5 +97,5 @@ The Twobfuscator Optionally, if the client and server share a secret value SECRET, they can replace the MAC function with: - MAC(s,x) = MAC(s | x | SECRET | s) + MAC(s,x) = H(s | x | SECRET | s) diff --git a/src/protocols/obfs2.c b/src/protocols/obfs2.c index 3490d0e..6221bb2 100644 --- a/src/protocols/obfs2.c +++ b/src/protocols/obfs2.c @@ -72,10 +72,12 @@ static crypt_t * derive_key(void *s, const char *keytype) { obfs2_state_t *state = s; - crypt_t *cryptstate; uchar buf[SHA256_LENGTH]; digest_t *c = digest_new(); + digest_t *d; + int i; + digest_update(c, (uchar*)keytype, strlen(keytype)); if (seed_nonzero(state->initiator_seed)) digest_update(c, state->initiator_seed, OBFUSCATE_SEED_LENGTH); @@ -85,6 +87,13 @@ derive_key(void *s, const char *keytype) digest_update(c, state->secret_seed, SHARED_SECRET_LENGTH); digest_update(c, (uchar*)keytype, strlen(keytype)); digest_getdigest(c, buf, sizeof(buf)); + + for (i=0; i < OBFUSCATE_HASH_ITERATIONS; i++) { + d = digest_new(); + digest_update(d, buf, sizeof(buf)); + digest_getdigest(d, buf, sizeof(buf)); + } + cryptstate = crypt_new(buf, 16); crypt_set_iv(cryptstate, buf+16, 16); memset(buf, 0, sizeof(buf)); @@ -101,6 +110,9 @@ derive_padding_key(void *s, const uchar *seed, crypt_t *cryptstate; uchar buf[SHA256_LENGTH]; digest_t *c = digest_new(); + digest_t *d; + int i; + digest_update(c, (uchar*)keytype, strlen(keytype)); if (seed_nonzero(seed)) digest_update(c, seed, OBFUSCATE_SEED_LENGTH); @@ -108,6 +120,13 @@ derive_padding_key(void *s, const uchar *seed, digest_update(c, state->secret_seed, OBFUSCATE_SEED_LENGTH); digest_update(c, (uchar*)keytype, strlen(keytype)); digest_getdigest(c, buf, sizeof(buf)); + + for (i=0; i < OBFUSCATE_HASH_ITERATIONS; i++) { + d = digest_new(); + digest_update(d, buf, sizeof(buf)); + digest_getdigest(d, buf, sizeof(buf)); + } + cryptstate = crypt_new(buf, 16); crypt_set_iv(cryptstate, buf+16, 16); memset(buf, 0, 16); diff --git a/src/protocols/obfs2.h b/src/protocols/obfs2.h index 1f9f31d..0d70144 100644 --- a/src/protocols/obfs2.h +++ b/src/protocols/obfs2.h @@ -36,6 +36,7 @@ void *obfs2_new(struct protocol_t *proto_struct, #define OBFUSCATE_SEED_LENGTH 16 #define OBFUSCATE_MAX_PADDING 8192 #define OBFUSCATE_ZERO_SEED "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0" +#define OBFUSCATE_HASH_ITERATIONS 100000 #define INITIATOR_PAD_TYPE "Initiator obfuscation padding" #define RESPONDER_PAD_TYPE "Responder obfuscation padding"

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