X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=secnet.git;a=blobdiff_plain;f=site.c;h=b9b4d0dd0c0974e3b5d960a077977e14c54d9349;hp=f65051fca9a4009467384e6f9f1f0b6a8f81b0b4;hb=4a1a591973e0be6f33a55b8f1fc5abc827f6969d;hpb=065e1922e00c787775b595badce0e40a999a6afb

diff --git a/site.c b/site.c
index f65051f..b9b4d0d 100644
--- a/site.c
+++ b/site.c
@@ -214,6 +214,12 @@ static void transport_xmit(struct site *st, transport_peers *peers,
  /***** END of transport peers declarations *****/
 
 
+struct data_key {
+    struct transform_inst_if *transform;
+    uint64_t key_timeout; /* End of life of current key */
+    uint32_t remote_session_id;
+};
+
 struct site {
     closure_t cl;
     struct site_if ops;
@@ -259,11 +265,11 @@ struct site {
     uint64_t now; /* Most recently seen time */
 
     /* The currently established session */
-    uint32_t remote_session_id;
-    struct transform_inst_if *current_transform;
-    bool_t current_valid;
-    uint64_t current_key_timeout; /* End of life of current key */
+    struct data_key current;
+    struct data_key auxiliary_key;
+    bool_t auxiliary_is_new;
     uint64_t renegotiate_key_time; /* When we can negotiate a new key */
+    uint64_t auxiliary_renegotiate_key_time;
     transport_peers peers; /* Current address(es) of peer for data traffic */
 
     /* The current key setup protocol exchange.  We can only be
@@ -277,6 +283,7 @@ struct site {
     uint8_t localN[NONCELEN]; /* Nonces for key exchange */
     uint8_t remoteN[NONCELEN];
     struct buffer_if buffer; /* Current outgoing key exchange packet */
+    struct buffer_if scratch;
     int32_t retries; /* Number of retries remaining */
     uint64_t timeout; /* Timeout for current state */
     uint8_t *dhsecret;
@@ -315,12 +322,22 @@ static void slog(struct site *st, uint32_t event, cstring_t msg, ...)
 }
 
 static void set_link_quality(struct site *st);
-static void delete_key(struct site *st, cstring_t reason, uint32_t loglevel);
+static void delete_keys(struct site *st, cstring_t reason, uint32_t loglevel);
+static void delete_one_key(struct site *st, struct data_key *key,
+			   const char *reason /* may be 0 meaning don't log*/,
+			   const char *which /* ignored if !reasonn */,
+			   uint32_t loglevel /* ignored if !reasonn */);
 static bool_t initiate_key_setup(struct site *st, cstring_t reason);
 static void enter_state_run(struct site *st);
 static bool_t enter_state_resolve(struct site *st);
 static bool_t enter_new_state(struct site *st,uint32_t next);
 static void enter_state_wait(struct site *st);
+static void activate_new_key(struct site *st);
+
+static bool_t current_valid(struct site *st)
+{
+    return st->current.transform->valid(st->current.transform->st);
+}
 
 #define CHECK_AVAIL(b,l) do { if ((b)->size<(l)) return False; } while(0)
 #define CHECK_EMPTY(b) do { if ((b)->size!=0) return False; } while(0)
@@ -446,7 +463,7 @@ static bool_t check_msg(struct site *st, uint32_t type, struct msg *m,
 	return False;
     }
     if (type==LABEL_MSG2) return True;
-    if (memcmp(m->nR,st->remoteN,NONCELEN)!=0) {
+    if (!consttime_memeq(m->nR,st->remoteN,NONCELEN)!=0) {
 	*error="wrong remotely-generated nonce";
 	return False;
     }
@@ -640,15 +657,15 @@ static bool_t generate_msg5(struct site *st)
 }
 
 static bool_t process_msg5(struct site *st, struct buffer_if *msg5,
-			   const struct comm_addr *src)
+			   const struct comm_addr *src,
+			   struct transform_inst_if *transform)
 {
     struct msg0 m;
     cstring_t transform_err;
 
     if (!unpick_msg0(st,msg5,&m)) return False;
 
-    if (st->new_transform->reverse(st->new_transform->st,
-				   msg5,&transform_err)) {
+    if (transform->reverse(transform->st,msg5,&transform_err)) {
 	/* There's a problem */
 	slog(st,LOG_SEC,"process_msg5: transform: %s",transform_err);
 	return False;
@@ -664,7 +681,8 @@ static bool_t process_msg5(struct site *st, struct buffer_if *msg5,
     return True;
 }
 
-static bool_t generate_msg6(struct site *st)
+static void create_msg6(struct site *st, struct transform_inst_if *transform,
+			uint32_t session_id)
 {
     cstring_t transform_err;
 
@@ -674,12 +692,15 @@ static bool_t generate_msg6(struct site *st)
     /* Give the netlink code an opportunity to put its own stuff in the
        message (configuration information, etc.) */
     buf_prepend_uint32(&st->buffer,LABEL_MSG6);
-    st->new_transform->forwards(st->new_transform->st,&st->buffer,
-				&transform_err);
+    transform->forwards(transform->st,&st->buffer,&transform_err);
     buf_prepend_uint32(&st->buffer,LABEL_MSG6);
     buf_prepend_uint32(&st->buffer,st->index);
-    buf_prepend_uint32(&st->buffer,st->setup_session_id);
+    buf_prepend_uint32(&st->buffer,session_id);
+}
 
+static bool_t generate_msg6(struct site *st)
+{
+    create_msg6(st,st->new_transform,st->setup_session_id);
     st->retries=1; /* Peer will retransmit MSG5 if this packet gets lost */
     return True;
 }
@@ -711,23 +732,68 @@ static bool_t process_msg6(struct site *st, struct buffer_if *msg6,
 
 static bool_t decrypt_msg0(struct site *st, struct buffer_if *msg0)
 {
-    cstring_t transform_err;
+    cstring_t transform_err, auxkey_err, newkey_err="n/a";
     struct msg0 m;
     uint32_t problem;
 
-    if (!st->current_valid) {
-	slog(st,LOG_DROP,"incoming message but no current key -> dropping");
-	initiate_key_setup(st,"incoming message but no current key");
+    if (!unpick_msg0(st,msg0,&m)) return False;
+
+    /* Keep a copy so we can try decrypting it with multiple keys */
+    buffer_copy(&st->scratch, msg0);
+
+    problem = st->current.transform->reverse(st->current.transform->st,
+					     msg0,&transform_err);
+    if (!problem) {
+	if (!st->auxiliary_is_new)
+	    delete_one_key(st,&st->auxiliary_key,
+			   "peer has used new key","auxiliary key",LOG_SEC);
+	return True;
+    }
+
+    if (problem==2) {
+	slog(st,LOG_DROP,"transform: %s (merely skew)",transform_err);
 	return False;
     }
 
-    if (!unpick_msg0(st,msg0,&m)) return False;
+    buffer_copy(msg0, &st->scratch);
+    problem = st->auxiliary_key.transform->reverse
+	(st->auxiliary_key.transform->st,msg0,&auxkey_err);
+    if (problem==0) {
+	slog(st,LOG_DROP,"processing packet which uses auxiliary key");
+	if (st->auxiliary_is_new) {
+	    /* We previously timed out in state SENTMSG5 but it turns
+	     * out that our peer did in fact get our MSG5 and is
+	     * using the new key.  So we should switch to it too. */
+	    /* This is a bit like activate_new_key. */
+	    struct data_key t;
+	    t=st->current;
+	    st->current=st->auxiliary_key;
+	    st->auxiliary_key=t;
+
+	    delete_one_key(st,&st->auxiliary_key,"peer has used new key",
+			   "previous key",LOG_SEC);
+	    st->auxiliary_is_new=0;
+	    st->renegotiate_key_time=st->auxiliary_renegotiate_key_time;
+	}
+	return True;
+    }
 
-    problem = st->current_transform->reverse(st->current_transform->st,
-					     msg0,&transform_err);
-    if (!problem) return True;
+    if (st->state==SITE_SENTMSG5) {
+	buffer_copy(msg0, &st->scratch);
+	if (!st->new_transform->reverse(st->new_transform->st,
+					msg0,&newkey_err)) {
+	    /* It looks like we didn't get the peer's MSG6 */
+	    /* This is like a cut-down enter_new_state(SITE_RUN) */
+	    slog(st,LOG_STATE,"will enter state RUN (MSG0 with new key)");
+	    BUF_FREE(&st->buffer);
+	    st->timeout=0;
+	    activate_new_key(st);
+	    return True; /* do process the data in this packet */
+	}
+    }
 
-    slog(st,LOG_SEC,"transform: %s",transform_err);
+    slog(st,LOG_SEC,"transform: %s (aux: %s, new: %s)",
+	 transform_err,auxkey_err,newkey_err);
     initiate_key_setup(st,"incoming message would not decrypt");
     return False;
 }
@@ -745,7 +811,7 @@ static bool_t process_msg0(struct site *st, struct buffer_if *msg0,
     switch(type) {
     case LABEL_MSG7:
 	/* We must forget about the current session. */
-	delete_key(st,"request from peer",LOG_SEC);
+	delete_keys(st,"request from peer",LOG_SEC);
 	return True;
     case LABEL_MSG9:
 	/* Deliver to netlink layer */
@@ -788,6 +854,24 @@ static bool_t send_msg(struct site *st)
 	st->timeout=st->now+st->setup_retry_interval;
 	st->retries--;
 	return True;
+    } else if (st->state==SITE_SENTMSG5) {
+	slog(st,LOG_SETUP_TIMEOUT,"timed out sending MSG5, stashing new key");
+	/* We stash the key we have produced, in case it turns out that
+	 * our peer did see our MSG5 after all and starts using it. */
+	/* This is a bit like some of activate_new_key */
+	struct transform_inst_if *t;
+	t=st->auxiliary_key.transform;
+	st->auxiliary_key.transform=st->new_transform;
+	st->new_transform=t;
+
+	t->delkey(t->st);
+	st->auxiliary_is_new=1;
+	st->auxiliary_key.key_timeout=st->now+st->key_lifetime;
+	st->auxiliary_renegotiate_key_time=st->now+st->key_renegotiate_time;
+	st->auxiliary_key.remote_session_id=st->setup_session_id;
+
+	enter_state_wait(st);
+	return False;
     } else {
 	slog(st,LOG_SETUP_TIMEOUT,"timed out sending key setup packet "
 	    "(in state %s)",state_name(st->state));
@@ -843,34 +927,44 @@ static void activate_new_key(struct site *st)
 {
     struct transform_inst_if *t;
 
-    /* We have two transform instances, which we swap between active
-       and setup */
-    t=st->current_transform;
-    st->current_transform=st->new_transform;
+    /* We have three transform instances, which we swap between old,
+       active and setup */
+    t=st->auxiliary_key.transform;
+    st->auxiliary_key.transform=st->current.transform;
+    st->current.transform=st->new_transform;
     st->new_transform=t;
 
     t->delkey(t->st);
     st->timeout=0;
-    st->current_valid=True;
-    st->current_key_timeout=st->now+st->key_lifetime;
+    st->auxiliary_is_new=0;
+    st->auxiliary_key.key_timeout=st->current.key_timeout;
+    st->current.key_timeout=st->now+st->key_lifetime;
     st->renegotiate_key_time=st->now+st->key_renegotiate_time;
     transport_peers_copy(st,&st->peers,&st->setup_peers);
-    st->remote_session_id=st->setup_session_id;
+    st->current.remote_session_id=st->setup_session_id;
 
     slog(st,LOG_ACTIVATE_KEY,"new key activated");
     enter_state_run(st);
 }
 
-static void delete_key(struct site *st, cstring_t reason, uint32_t loglevel)
+static void delete_one_key(struct site *st, struct data_key *key,
+			   cstring_t reason, cstring_t which, uint32_t loglevel)
+{
+    if (!key->transform->valid(key->transform->st)) return;
+    if (reason) slog(st,loglevel,"%s deleted (%s)",which,reason);
+    key->transform->delkey(key->transform->st);
+    key->key_timeout=0;
+}
+
+static void delete_keys(struct site *st, cstring_t reason, uint32_t loglevel)
 {
-    if (st->current_valid) {
+    if (current_valid(st)) {
 	slog(st,loglevel,"session closed (%s)",reason);
 
-	st->current_valid=False;
-	st->current_transform->delkey(st->current_transform->st);
-	st->current_key_timeout=0;
+	delete_one_key(st,&st->current,0,0,0);
 	set_link_quality(st);
     }
+    delete_one_key(st,&st->auxiliary_key,0,0,0);
 }
 
 static void state_assert(struct site *st, bool_t ok)
@@ -882,14 +976,14 @@ static void enter_state_stop(struct site *st)
 {
     st->state=SITE_STOP;
     st->timeout=0;
-    delete_key(st,"entering state STOP",LOG_TIMEOUT_KEY);
+    delete_keys(st,"entering state STOP",LOG_TIMEOUT_KEY);
     st->new_transform->delkey(st->new_transform->st);
 }
 
 static void set_link_quality(struct site *st)
 {
     uint32_t quality;
-    if (st->current_valid)
+    if (current_valid(st))
 	quality=LINK_QUALITY_UP;
     else if (st->state==SITE_WAIT || st->state==SITE_STOP)
 	quality=LINK_QUALITY_DOWN;
@@ -1001,17 +1095,17 @@ static bool_t send_msg7(struct site *st, cstring_t reason)
 {
     cstring_t transform_err;
 
-    if (st->current_valid && st->buffer.free
+    if (current_valid(st) && st->buffer.free
 	&& transport_peers_valid(&st->peers)) {
 	BUF_ALLOC(&st->buffer,"site:MSG7");
 	buffer_init(&st->buffer,st->transform->max_start_pad+(4*3));
 	buf_append_uint32(&st->buffer,LABEL_MSG7);
 	buf_append_string(&st->buffer,reason);
-	st->current_transform->forwards(st->current_transform->st,
+	st->current.transform->forwards(st->current.transform->st,
 					&st->buffer, &transform_err);
 	buf_prepend_uint32(&st->buffer,LABEL_MSG0);
 	buf_prepend_uint32(&st->buffer,st->index);
-	buf_prepend_uint32(&st->buffer,st->remote_session_id);
+	buf_prepend_uint32(&st->buffer,st->current.remote_session_id);
 	transport_xmit(st,&st->peers,&st->buffer,True);
 	BUF_FREE(&st->buffer);
 	return True;
@@ -1052,14 +1146,23 @@ static int site_beforepoll(void *sst, struct pollfd *fds, int *nfds_io,
     st->now=*now;
 
     /* Work out when our next timeout is. The earlier of 'timeout' or
-       'current_key_timeout'. A stored value of '0' indicates no timeout
+       'current.key_timeout'. A stored value of '0' indicates no timeout
        active. */
     site_settimeout(st->timeout, timeout_io);
-    site_settimeout(st->current_key_timeout, timeout_io);
+    site_settimeout(st->current.key_timeout, timeout_io);
+    site_settimeout(st->auxiliary_key.key_timeout, timeout_io);
 
     return 0; /* success */
 }
 
+static void check_expiry(struct site *st, struct data_key *key,
+			 const char *which)
+{
+    if (key->key_timeout && *now>key->key_timeout) {
+	delete_one_key(st,key,"maximum life exceeded",which,LOG_TIMEOUT_KEY);
+    }
+}
+
 /* NB site_afterpoll will be called before site_beforepoll is ever called */
 static void site_afterpoll(void *sst, struct pollfd *fds, int nfds)
 {
@@ -1078,9 +1181,8 @@ static void site_afterpoll(void *sst, struct pollfd *fds, int nfds)
 		 st->state);
 	}
     }
-    if (st->current_key_timeout && *now>st->current_key_timeout) {
-	delete_key(st,"maximum key life exceeded",LOG_TIMEOUT_KEY);
-    }
+    check_expiry(st,&st->current,"current key");
+    check_expiry(st,&st->auxiliary_key,"auxiliary key");
 }
 
 /* This function is called by the netlink device to deliver packets
@@ -1098,15 +1200,15 @@ static void site_outgoing(void *sst, struct buffer_if *buf)
 
     /* In all other states we consider delivering the packet if we have
        a valid key and a valid address to send it to. */
-    if (st->current_valid && transport_peers_valid(&st->peers)) {
+    if (current_valid(st) && transport_peers_valid(&st->peers)) {
 	/* Transform it and send it */
 	if (buf->size>0) {
 	    buf_prepend_uint32(buf,LABEL_MSG9);
-	    st->current_transform->forwards(st->current_transform->st,
+	    st->current.transform->forwards(st->current.transform->st,
 					    buf, &transform_err);
 	    buf_prepend_uint32(buf,LABEL_MSG0);
 	    buf_prepend_uint32(buf,st->index);
-	    buf_prepend_uint32(buf,st->remote_session_id);
+	    buf_prepend_uint32(buf,st->current.remote_session_id);
 	    transport_xmit(st,&st->peers,buf,False);
 	}
 	BUF_FREE(buf);
@@ -1186,7 +1288,7 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
 	case 0: /* NAK */
 	    /* If the source is our current peer then initiate a key setup,
 	       because our peer's forgotten the key */
-	    if (get_uint32(buf->start+4)==st->remote_session_id) {
+	    if (get_uint32(buf->start+4)==st->current.remote_session_id) {
 		initiate_key_setup(st,"received a NAK");
 	    } else {
 		slog(st,LOG_SEC,"bad incoming NAK");
@@ -1237,16 +1339,29 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
 	    /* Setup packet: expected only in state SENTMSG4 */
 	    /* (may turn up in state RUN if our return MSG6 was lost
 	       and the new key has already been activated. In that
-	       case we should treat it as an ordinary PING packet. We
-	       can't pass it to process_msg5() because the
-	       new_transform will now be unkeyed. XXX) */
-	    if (st->state!=SITE_SENTMSG4) {
-		slog(st,LOG_UNEXPECTED,"unexpected MSG5");
-	    } else if (process_msg5(st,buf,source)) {
-		transport_setup_msgok(st,source);
-		enter_new_state(st,SITE_RUN);
+	       case we discard it. The peer will realise that we
+	       are using the new key when they see our data packets.
+	       Until then the peer's data packets to us get discarded. */
+	    if (st->state==SITE_SENTMSG4) {
+		if (process_msg5(st,buf,source,st->new_transform)) {
+		    transport_setup_msgok(st,source);
+		    enter_new_state(st,SITE_RUN);
+		} else {
+		    slog(st,LOG_SEC,"invalid MSG5");
+		}
+	    } else if (st->state==SITE_RUN) {
+		if (process_msg5(st,buf,source,st->current.transform)) {
+		    slog(st,LOG_DROP,"got MSG5, retransmitting MSG6");
+		    transport_setup_msgok(st,source);
+		    create_msg6(st,st->current.transform,
+				st->current.remote_session_id);
+		    transport_xmit(st,&st->peers,&st->buffer,True);
+		    BUF_FREE(&st->buffer);
+		} else {
+		    slog(st,LOG_SEC,"invalid MSG5 (in state RUN)");
+		}
 	    } else {
-		slog(st,LOG_SEC,"invalid MSG5");
+		slog(st,LOG_UNEXPECTED,"unexpected MSG5");
 	    }
 	    break;
 	case LABEL_MSG6:
@@ -1428,13 +1543,16 @@ static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
 
     buffer_new(&st->buffer,SETUP_BUFFER_LEN);
 
+    buffer_new(&st->scratch,0);
+    BUF_ALLOC(&st->scratch,"site:scratch");
+
     /* We are interested in poll(), but only for timeouts. We don't have
        any fds of our own. */
     register_for_poll(st, site_beforepoll, site_afterpoll, 0, "site");
     st->timeout=0;
 
-    st->current_valid=False;
-    st->current_key_timeout=0;
+    st->current.key_timeout=0;
+    st->auxiliary_key.key_timeout=0;
     transport_peers_clear(st,&st->peers);
     transport_peers_clear(st,&st->setup_peers);
     /* XXX mlock these */
@@ -1461,8 +1579,10 @@ static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
     for (i=0; i<st->ncomms; i++)
 	st->comms[i]->request_notify(st->comms[i]->st, st, site_incoming);
 
-    st->current_transform=st->transform->create(st->transform->st);
+    st->current.transform=st->transform->create(st->transform->st);
+    st->auxiliary_key.transform=st->transform->create(st->transform->st);
     st->new_transform=st->transform->create(st->transform->st);
+    st->auxiliary_is_new=0;
 
     enter_state_stop(st);