From 2d4f61459284a52c1641a334be3b59ab601f2192 Mon Sep 17 00:00:00 2001
From: Johan Siebens <johan.siebens@gmail.com>
Date: Sun, 15 May 2022 08:11:45 +0200
Subject: [PATCH] feat: acl rules based on cidr ranges

---
 internal/domain/acl.go      | 40 +++++++++++++++++++++++--------------
 internal/domain/machine.go  | 14 ++++++++++++-
 internal/service/machine.go |  4 ++--
 3 files changed, 40 insertions(+), 18 deletions(-)

diff --git a/internal/domain/acl.go b/internal/domain/acl.go
index d9d9b2c..4d510e0 100644
--- a/internal/domain/acl.go
+++ b/internal/domain/acl.go
@@ -58,7 +58,7 @@ func (a *aclEngine) isValidPeer(src *Machine, dest *Machine) bool {
 		}
 
 		for _, alias := range acl.Src {
-			if len(a.expandMachineAlias(src, alias)) != 0 {
+			if len(a.expandMachineAlias(src, alias, true)) != 0 {
 				return true
 			}
 		}
@@ -78,7 +78,7 @@ func (a *aclEngine) build(dst *Machine, peers []Machine) []tailcfg.FilterRule {
 		var allSrcIPs []string
 		for _, src := range acl.Src {
 			for _, peer := range peers {
-				srcIPs := a.expandMachineAlias(&peer, src)
+				srcIPs := a.expandMachineAlias(&peer, src, true)
 				allSrcIPs = append(allSrcIPs, srcIPs...)
 			}
 		}
@@ -129,7 +129,7 @@ func (a *aclEngine) expandMachineDestToNetPortRanges(m *Machine, dest string) []
 		return nil
 	}
 
-	ips := a.expandMachineAlias(m, alias)
+	ips := a.expandMachineAlias(m, alias, false)
 	if len(ips) == 0 {
 		return nil
 	}
@@ -148,26 +148,36 @@ func (a *aclEngine) expandMachineDestToNetPortRanges(m *Machine, dest string) []
 	return dests
 }
 
-func (a *aclEngine) expandMachineAlias(m *Machine, src string) []string {
-	if src == "*" {
-		if src == "*" {
+func (a *aclEngine) expandMachineAlias(m *Machine, alias string, src bool) []string {
+	if alias == "*" {
+		if alias == "*" {
 			return []string{"*"}
 		}
 	}
 
-	machineIPs := []string{m.IPv4.String(), m.IPv6.String()}
-
-	if strings.HasPrefix(src, "tag:") && m.HasTag(src[4:]) {
-		return machineIPs
+	if strings.HasPrefix(alias, "tag:") && m.HasTag(alias[4:]) {
+		return []string{m.IPv4.String(), m.IPv6.String()}
 	}
 
-	if h, ok := a.policy.Hosts[src]; ok {
-		src = h
+	if h, ok := a.policy.Hosts[alias]; ok {
+		alias = h
 	}
 
-	ip, err := netaddr.ParseIP(src)
-	if err == nil && m.HasIP(ip) {
-		return machineIPs
+	if src {
+		ip, err := netaddr.ParseIP(alias)
+		if err == nil && m.HasIP(ip) {
+			return []string{ip.String()}
+		}
+	} else {
+		ip, err := netaddr.ParseIP(alias)
+		if err == nil && m.IsAllowedIP(ip) {
+			return []string{ip.String()}
+		}
+
+		prefix, err := netaddr.ParseIPPrefix(alias)
+		if err == nil && m.IsAllowedIPPrefix(prefix) {
+			return []string{prefix.String()}
+		}
 	}
 
 	return []string{}
diff --git a/internal/domain/machine.go b/internal/domain/machine.go
index 199f27a..788b9f8 100644
--- a/internal/domain/machine.go
+++ b/internal/domain/machine.go
@@ -57,7 +57,19 @@ func (m *Machine) HasTag(tag string) bool {
 	return false
 }
 
-func (m *Machine) IsAllowedIP(i netaddr.IPPrefix) bool {
+func (m *Machine) IsAllowedIP(i netaddr.IP) bool {
+	if m.HasIP(i) {
+		return true
+	}
+	for _, t := range m.AllowIPs {
+		if t.Contains(i) {
+			return true
+		}
+	}
+	return false
+}
+
+func (m *Machine) IsAllowedIPPrefix(i netaddr.IPPrefix) bool {
 	for _, t := range m.AllowIPs {
 		if t.Overlaps(i) {
 			return true
diff --git a/internal/service/machine.go b/internal/service/machine.go
index 89a344f..cf3a7b9 100644
--- a/internal/service/machine.go
+++ b/internal/service/machine.go
@@ -92,7 +92,7 @@ func (s *Service) GetMachineRoutes(ctx context.Context, req *api.GetMachineRoute
 	for _, r := range m.HostInfo.RoutableIPs {
 		routes = append(routes, &api.RoutableIP{
 			Advertised: r.String(),
-			Allowed:    m.IsAllowedIP(r),
+			Allowed:    m.IsAllowedIPPrefix(r),
 		})
 	}
 
@@ -133,7 +133,7 @@ func (s *Service) SetMachineRoutes(ctx context.Context, req *api.SetMachineRoute
 	for _, r := range m.HostInfo.RoutableIPs {
 		routes = append(routes, &api.RoutableIP{
 			Advertised: r.String(),
-			Allowed:    m.IsAllowedIP(r),
+			Allowed:    m.IsAllowedIPPrefix(r),
 		})
 	}