Imported Debian patch 1:1.05-8

[hcoop/zz_old/debian/djbdns.git] / dbndns / diff / 0004-dnscache.c-allow-a-maximum-of-20-concurrent-outgoing.diff

From a7e94dd5f99a7e63af8fb2ce0406e294703814b7 Mon Sep 17 00:00:00 2001
From: Gerrit Pape <pape@smarden.org>
Date: Tue, 10 Mar 2009 13:35:38 +0000
Subject: [PATCH] dnscache.c: allow a maximum of 20 concurrent outgoing SOA queries

dnscache doesn't cache SOA records, and doesn't merge outgoing queries
to the same servers.  This commit limits the concurrent outgoing SOA
queries to 20 to make birthday attacks as described in CVE-2008-4392
more difficult.
---
 dnscache.c |   15 +++++++++++++++
 log.c      |    6 ++++++
 2 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/dnscache.c b/dnscache.c
index abcba69..2366ecc 100644
--- a/dnscache.c
+++ b/dnscache.c
@@ -72,11 +72,15 @@ static struct udpclient {
 } u[MAXUDP];
 int uactive = 0;
 
+#define MAXSOA 20
+int soaactive = 0;
+
 void u_drop(int j)
 {
   if (!u[j].active) return;
   log_querydrop(&u[j].active);
   u[j].active = 0; --uactive;
+  if (byte_equal(u[j].q.type,2,DNS_T_SOA)) --soaactive;
 }
 
 void u_respond(int j)
@@ -87,6 +91,7 @@ void u_respond(int j)
   socket_send6(udp53,response,response_len,u[j].ip,u[j].port,u[j].scope_id);
   log_querydone(&u[j].active,response_len);
   u[j].active = 0; --uactive;
+  if (byte_equal(u[j].q.type,2,DNS_T_SOA)) --soaactive;
 }
 
 void u_new(void)
@@ -125,6 +130,16 @@ void u_new(void)
 
   x->active = ++numqueries; ++uactive;
   log_query(&x->active,x->ip,x->port,x->id,q,qtype);
+
+  if (byte_equal(qtype,2,DNS_T_SOA)) {
+    if (soaactive >= MAXSOA) {
+      log_querydropmaxsoa(&x->active);
+      x->active = 0; --uactive;
+      return;
+    }
+    ++soaactive;
+  }
+
   switch(query_start(&x->q,q,qtype,qclass,myipoutgoing,interface)) {
     case -1:
       u_drop(j);
diff --git a/log.c b/log.c
index df465e2..a651607 100644
--- a/log.c
+++ b/log.c
@@ -118,6 +118,12 @@ void log_querydrop(uint64 *qnum)
   line();
 }
 
+void log_querydropmaxsoa(uint64 *qnum)
+{
+  string("drop "); number(*qnum); space(); string("maxsoa");
+  line();
+}
+
 void log_tcpopen(const char client[16],unsigned int port)
 {
   string("tcpopen ");
-- 
1.6.2