bugfix: generate 32-bit site index in packets in a sane way

Use a sequential nonzero integer as site index instead of the address
of the site structure(!).  This value is not secret but does need to
be unique, and truncating the address to 32 bits doesn't guarantee
that.

Signed-off-by: Richard Kettlewell <richard@greenend.org.uk>
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/site.c b/site.c
index c2777c4..29efb25 100644 (file)
--- a/site.c
+++ b/site.c
@@ -17,6 +17,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <limits.h>
+#include <assert.h>
 #include <sys/socket.h>
 
 #include <sys/mman.h>
@@ -145,6 +146,7 @@ struct site {
     struct dh_if *dh;
     struct hash_if *hash;
 
+    uint32_t index; /* Index of this site */
     int32_t setup_retries; /* How many times to send setup packets */
     int32_t setup_timeout; /* Initial timeout for setup packets */
     int32_t wait_timeout; /* How long to wait if setup unsuccessful */
@@ -268,7 +270,7 @@ static bool_t generate_msg(struct site *st, uint32_t type, cstring_t what)
     buffer_init(&st->buffer,0);
     buf_append_uint32(&st->buffer,
        (type==LABEL_MSG1?0:st->setup_session_id));
-    buf_append_uint32(&st->buffer,(uint32_t)st);
+    buf_append_uint32(&st->buffer,st->index);
     buf_append_uint32(&st->buffer,type);
     buf_append_string(&st->buffer,st->localname);
     buf_append_string(&st->buffer,st->remotename);
@@ -542,7 +544,7 @@ static bool_t generate_msg5(struct site *st)
     st->new_transform->forwards(st->new_transform->st,&st->buffer,
                                &transform_err);
     buf_prepend_uint32(&st->buffer,LABEL_MSG5);
-    buf_prepend_uint32(&st->buffer,(uint32_t)st);
+    buf_prepend_uint32(&st->buffer,st->index);
     buf_prepend_uint32(&st->buffer,st->setup_session_id);
 
     st->retries=st->setup_retries;
@@ -591,7 +593,7 @@ static bool_t generate_msg6(struct site *st)
     st->new_transform->forwards(st->new_transform->st,&st->buffer,
                                &transform_err);
     buf_prepend_uint32(&st->buffer,LABEL_MSG6);
-    buf_prepend_uint32(&st->buffer,(uint32_t)st);
+    buf_prepend_uint32(&st->buffer,st->index);
     buf_prepend_uint32(&st->buffer,st->setup_session_id);
 
     st->retries=1; /* Peer will retransmit MSG5 if this packet gets lost */
@@ -909,7 +911,7 @@ static bool_t send_msg7(struct site *st, cstring_t reason)
        st->current_transform->forwards(st->current_transform->st,
                                        &st->buffer, &transform_err);
        buf_prepend_uint32(&st->buffer,LABEL_MSG0);
-       buf_prepend_uint32(&st->buffer,(uint32_t)st);
+       buf_prepend_uint32(&st->buffer,st->index);
        buf_prepend_uint32(&st->buffer,st->remote_session_id);
        st->comm->sendmsg(st->comm->st,&st->buffer,&st->peer);
        BUF_FREE(&st->buffer);
@@ -1005,7 +1007,7 @@ static void site_outgoing(void *sst, struct buffer_if *buf)
            st->current_transform->forwards(st->current_transform->st,
                                            buf, &transform_err);
            buf_prepend_uint32(buf,LABEL_MSG0);
-           buf_prepend_uint32(buf,(uint32_t)st);
+           buf_prepend_uint32(buf,st->index);
            buf_prepend_uint32(buf,st->remote_session_id);
            st->comm->sendmsg(st->comm->st,buf,&st->peer);
        }
@@ -1078,7 +1080,7 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
        }
        return False; /* Not for us. */
     }
-    if (dest==(uint32_t)st) {
+    if (dest==st->index) {
        /* Explicitly addressed to us */
        uint32_t msgtype=ntohl(get_uint32(buf->start+8));
        if (msgtype!=LABEL_MSG0) dump_packet(st,buf,source,True);
@@ -1186,6 +1188,7 @@ static void site_phase_hook(void *sst, uint32_t newphase)
 static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
                          list_t *args)
 {
+    static uint32_t index_sequence;
     struct site *st;
     item_t *item;
     dict_t *dict;
@@ -1217,6 +1220,8 @@ static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
        free(st);
        return NULL;
     }
+    assert(index_sequence < 0xffffffffUL);
+    st->index = ++index_sequence;
     st->netlink=find_cl_if(dict,"link",CL_NETLINK,True,"site",loc);
     st->comm=find_cl_if(dict,"comm",CL_COMM,True,"site",loc);
     st->resolver=find_cl_if(dict,"resolver",CL_RESOLVER,True,"site",loc);