Add config option for local_cidr control

Author: nbrownus

examples/config.yml

@@ -309,6 +309,13 @@ firewall:
   outbound_action: drop
   inbound_action: drop
 
+  # Controls the default value for local_cidr. Default is true, will be deprecated after v1.9 and defaulted to false.
+  # This setting only affects nebula hosts with subnets encoded in their certificate. A nebula host acting as an
+  # unsafe router with `default_local_cidr_any: true` will expose their unsafe routes to every inbound rule regardless
+  # of the actual destination for the packet. Setting this to false requires each inbound rule to contain a `local_cidr`
+  # if the intention is to allow traffic to flow to an unsafe route.
+  #default_local_cidr_any: false
+
   conntrack:
     tcp_timeout: 12m
     udp_timeout: 3m
@@ -325,7 +332,8 @@ firewall:
   #   groups: Same as group but accepts a list of values. Multiple values are AND'd together and a certificate would have to contain all groups to pass
   #   cidr: a remote CIDR, `0.0.0.0/0` is any.
   #   local_cidr: a local CIDR, `0.0.0.0/0` is any. This could be used to filter destinations when using unsafe_routes.
-  #      Default is `any` unless the certificate contains subnets and then the default is the ip issued in the certificate.
+  #      Default is `any` unless the certificate contains subnets and then the default is the ip issued in the certificate
+  #      if `default_local_cidr_any` is false, otherwise its `any`.
   #   ca_name: An issuing CA name
   #   ca_sha: An issuing CA shasum
 

firewall.go

@@ -65,10 +65,11 @@ type Firewall struct {
 	rules        string
 	rulesVersion uint16
 
-	trackTCPRTT     bool
-	metricTCPRTT    metrics.Histogram
-	incomingMetrics firewallMetrics
-	outgoingMetrics firewallMetrics
+	defaultLocalCIDRAny bool
+	trackTCPRTT         bool
+	metricTCPRTT        metrics.Histogram
+	incomingMetrics     firewallMetrics
+	outgoingMetrics     firewallMetrics
 
 	l *logrus.Logger
 }
@@ -206,6 +207,9 @@ func NewFirewallFromConfig(l *logrus.Logger, nc *cert.NebulaCertificate, c *conf
 		//TODO: max_connections
 	)
 
+	//TODO: Flip to false after v1.9 release
+	fw.defaultLocalCIDRAny = c.GetBool("firewall.default_local_cidr_any", true)
+
 	inboundAction := c.GetString("firewall.inbound_action", "drop")
 	switch inboundAction {
 	case "reject":
@@ -873,10 +877,11 @@ func (fr *FirewallRule) match(p firewall.Packet, c *cert.NebulaCertificate) bool
 
 func (flc *firewallLocalCIDR) addRule(f *Firewall, localIp *net.IPNet) error {
 	if localIp == nil || (localIp != nil && localIp.Contains(net.IPv4(0, 0, 0, 0))) {
-		if !f.hasSubnets {
+		if !f.hasSubnets || f.defaultLocalCIDRAny {
 			flc.Any = true
 			return nil
 		}
+
 		localIp = f.assignedCIDR
 	}