From 004ebcaba1dea344d3407ac77713322512ab0471 Mon Sep 17 00:00:00 2001
From: Benjamin George Roberts <benjamin@bgroberts.id.au>
Date: Wed, 24 Aug 2022 20:53:55 +1000
Subject: [PATCH] initial implementation of autoApprovers support

---
 acls_types.go           | 18 +++++++---
 machine.go              | 75 +++++++++++++++++++++++++++++++++++++++++
 protocol_common_poll.go |  7 ++++
 3 files changed, 95 insertions(+), 5 deletions(-)

diff --git a/acls_types.go b/acls_types.go
index 0f73d6fd..b9a5d4da 100644
--- a/acls_types.go
+++ b/acls_types.go
@@ -11,11 +11,12 @@ import (
 
 // ACLPolicy represents a Tailscale ACL Policy.
 type ACLPolicy struct {
-	Groups    Groups    `json:"groups"    yaml:"groups"`
-	Hosts     Hosts     `json:"hosts"     yaml:"hosts"`
-	TagOwners TagOwners `json:"tagOwners" yaml:"tagOwners"`
-	ACLs      []ACL     `json:"acls"      yaml:"acls"`
-	Tests     []ACLTest `json:"tests"     yaml:"tests"`
+	Groups        Groups        `json:"groups"        yaml:"groups"`
+	Hosts         Hosts         `json:"hosts"         yaml:"hosts"`
+	TagOwners     TagOwners     `json:"tagOwners"     yaml:"tagOwners"`
+	ACLs          []ACL         `json:"acls"          yaml:"acls"`
+	Tests         []ACLTest     `json:"tests"         yaml:"tests"`
+	AutoApprovers AutoApprovers `json:"autoApprovers" yaml:"autoApprovers"`
 }
 
 // ACL is a basic rule for the ACL Policy.
@@ -42,6 +43,13 @@ type ACLTest struct {
 	Deny   []string `json:"deny,omitempty" yaml:"deny,omitempty"`
 }
 
+// AutoApprovers specify which users (namespaces?), groups or tags have their advertised routes
+// or exit node status automatically enabled
+type AutoApprovers struct {
+	Routes   map[string][]string `json:"routes"   yaml:"routes"`
+	ExitNode []string            `json:"exitNode" yaml:"exitNode"`
+}
+
 // UnmarshalJSON allows to parse the Hosts directly into netaddr objects.
 func (hosts *Hosts) UnmarshalJSON(data []byte) error {
 	newHosts := Hosts{}
diff --git a/machine.go b/machine.go
index 4399029c..928f78e2 100644
--- a/machine.go
+++ b/machine.go
@@ -930,6 +930,81 @@ func (h *Headscale) EnableRoutes(machine *Machine, routeStrs ...string) error {
 	return nil
 }
 
+// Enabled any routes advertised by a machine that match the ACL autoApprovers policy
+// TODO simplify by expanding only for current machine, and by checking if approvedIPs contains machine.IPs[0]
+func (h *Headscale) EnableAutoApprovedRoutes(machine *Machine) error {
+	approvedRoutes := make([]netaddr.IPPrefix, 0, len(machine.HostInfo.RoutableIPs))
+	machines, err := h.ListMachines()
+
+	if err != nil {
+		log.Err(err)
+		return err
+	}
+
+	for _, advertisedRoute := range machine.HostInfo.RoutableIPs {
+		log.Debug().
+			Uint64("machine", machine.ID).
+			Str("advertisedRoute", advertisedRoute.String()).
+			Msg("Client requested to advertise route")
+
+		approved := false
+		routeApprovers := h.aclPolicy.AutoApprovers.Routes[advertisedRoute.String()]
+
+		if advertisedRoute.Bits() == 0 {
+			routeApprovers = h.aclPolicy.AutoApprovers.ExitNode
+		}
+
+		if len(routeApprovers) > 0 {
+			for _, approvedAlias := range routeApprovers {
+
+				approvedIps, err := expandAlias(machines, *h.aclPolicy, approvedAlias, h.cfg.OIDC.StripEmaildomain)
+
+				if err != nil {
+					log.Err(err).
+						Str("alias", approvedAlias).
+						Msg("Failed to expand alias when processing autoApprovers policy")
+					return err
+				}
+
+				for _, machineIp := range machine.IPAddresses {
+					for _, approvedIp := range approvedIps {
+						approved = machineIp.String() == approvedIp
+
+						if approved {
+							break
+						}
+					}
+
+					if approved {
+						break
+					}
+				}
+			}
+		} else {
+			log.Debug().
+				Uint64("client", machine.ID).
+				Str("advertisedRoute", advertisedRoute.String()).
+				Msg("Advertised route is not automatically approved")
+		}
+
+		if approved {
+			approvedRoutes = append(approvedRoutes, advertisedRoute)
+		}
+	}
+
+	for _, approvedRoute := range approvedRoutes {
+		if !contains(machine.EnabledRoutes, approvedRoute) {
+			log.Info().
+				Str("route", approvedRoute.String()).
+				Uint64("client", machine.ID).
+				Msg("Enabling autoApproved route for client")
+			machine.EnabledRoutes = append(machine.EnabledRoutes, approvedRoute)
+		}
+	}
+
+	return nil
+}
+
 func (machine *Machine) RoutesToProto() *v1.Routes {
 	availableRoutes := machine.GetAdvertisedRoutes()
 
diff --git a/protocol_common_poll.go b/protocol_common_poll.go
index 65dcb556..d6a8fff2 100644
--- a/protocol_common_poll.go
+++ b/protocol_common_poll.go
@@ -42,7 +42,14 @@ func (h *Headscale) handlePollCommon(
 				Str("machine", machine.Hostname).
 				Err(err)
 		}
+
+		// update routes with peer information
+		err = h.EnableAutoApprovedRoutes(machine)
+		if err != nil {
+			//TODO
+		}
 	}
+
 	// From Tailscale client:
 	//
 	// ReadOnly is whether the client just wants to fetch the MapResponse,