From e4ff969a9868ecc25a85daab620f97227de8d493 Mon Sep 17 00:00:00 2001
From: Guus Sliepen <guus@tinc-vpn.org>
Date: Sat, 27 May 2000 19:04:12 +0000
Subject: [PATCH] Fix for a DoS attack: A remote user could telnet to the tinc
daemon and type only this line: 61 6 00000000/00000000:28f This would deny
any packets to be sent to other tinc networks (except for to the hosts that
run tincd's themselves). Solution is to skip hosts in lookup_conn() that
have not been activated yet. Fixed potential conn_list table corruption: If
a new connection is accepted but a connection with the same subnet would
already exist in the connection list, the OLD connection is terminated.
---
src/net.c | 2 +-
src/netutl.c | 7 ++++---
src/protocol.c | 17 ++++++++++++-----
3 files changed, 17 insertions(+), 9 deletions(-)
diff --git a/src/net.c b/src/net.c
index f8c7306..2d16ae8 100644
--- a/src/net.c
+++ b/src/net.c
@@ -821,8 +821,8 @@ cp
if(cl->status.outgoing)
{
- alarm(5);
signal(SIGALRM, sigalrm_handler);
+ alarm(5);
syslog(LOG_NOTICE, "Try to re-establish outgoing connection in 5 seconds.");
}
diff --git a/src/netutl.c b/src/netutl.c
index cc8266d..5b4badf 100644
--- a/src/netutl.c
+++ b/src/netutl.c
@@ -37,7 +37,8 @@
/*
look for a connection associated with the given vpn ip,
- return its connection structure
+ return its connection structure.
+ Skips connections that are not activated!
*/
conn_list_t *lookup_conn(ip_t ip)
{
@@ -45,10 +46,10 @@ conn_list_t *lookup_conn(ip_t ip)
cp
/* Exact match suggested by James B. MacLean */
for(p = conn_list; p != NULL; p = p->next)
- if(ip == p->vpn_ip)
+ if((ip == p->vpn_ip) && p->active)
return p;
for(p = conn_list; p != NULL; p = p->next)
- if((ip & p->vpn_mask) == (p->vpn_ip & p->vpn_mask))
+ if(((ip & p->vpn_mask) == (p->vpn_ip & p->vpn_mask)) && p->active)
return p;
cp
return NULL;
diff --git a/src/protocol.c b/src/protocol.c
index 3b81d7a..3b23c9e 100644
--- a/src/protocol.c
+++ b/src/protocol.c
@@ -188,7 +188,7 @@ void send_key_changed_all(void)
conn_list_t *p;
cp
for(p = conn_list; p != NULL; p = p->next)
- if(p->status.meta && p->protocol_version > PROT_3)
+ if(p->status.meta && p->active)
send_key_changed(p, myself);
cp
}
@@ -332,7 +332,7 @@ int notify_others(conn_list_t *new, conn_list_t *source,
conn_list_t *p;
cp
for(p = conn_list; p != NULL; p = p->next)
- if(p != new && p != source && p->status.meta)
+ if(p != new && p != source && p->status.meta && p->active)
function(p, new);
cp
return 0;
@@ -347,7 +347,7 @@ int notify_one(conn_list_t *new)
conn_list_t *p;
cp
for(p = conn_list; p != NULL; p = p->next)
- if(p != new && p->protocol_version > PROT_3)
+ if(p != new && p->active)
send_add_host(new, p);
cp
return 0;
@@ -392,8 +392,6 @@ cp
return -1;
send_passphrase(cl);
}
-
- cl->status.active = 0;
cp
return 0;
}
@@ -424,6 +422,7 @@ cp
int public_key_h(conn_list_t *cl)
{
char *g_n;
+ conn_list_t *old;
cp
if(sscanf(cl->buffer, "%*d %as", &g_n) != 1)
{
@@ -449,6 +448,14 @@ cp
else
send_ack(cl);
+ /* Okay, before we active the connection, we check if there is another entry
+ in the connection list with the same vpn_ip. If so, it presumably is an
+ old connection that has timed out but we don't know it yet. Because our
+ conn_list entry is not active, lookup_conn will skip ourself. */
+
+ if(old=lookup_conn(cl->vpn_ip))
+ terminate_connection(old);
+
cl->status.active = 1;
notify_others(cl, NULL, send_add_host);
notify_one(cl);
--
2.25.1