Add support for Policy ACLs

acls.go

@@ -0,0 +1,263 @@
+package headscale
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/tailscale/hujson"
+	"inet.af/netaddr"
+	"tailscale.com/tailcfg"
+)
+
+const errorEmptyPolicy = Error("empty policy")
+const errorInvalidAction = Error("invalid action")
+const errorInvalidUserSection = Error("invalid user section")
+const errorInvalidGroup = Error("invalid group")
+const errorInvalidTag = Error("invalid tag")
+const errorInvalidNamespace = Error("invalid namespace")
+const errorInvalidPortFormat = Error("invalid port format")
+
+// LoadACLPolicy loads the ACL policy from the specify path, and generates the ACL rules
+func (h *Headscale) LoadACLPolicy(path string) error {
+	policyFile, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer policyFile.Close()
+
+	var policy ACLPolicy
+	b, err := io.ReadAll(policyFile)
+	if err != nil {
+		return err
+	}
+	err = hujson.Unmarshal(b, &policy)
+	if err != nil {
+		return err
+	}
+	if policy.IsZero() {
+		return errorEmptyPolicy
+	}
+
+	h.aclPolicy = &policy
+	rules, err := h.generateACLRules()
+	if err != nil {
+		return err
+	}
+	h.aclRules = rules
+	return nil
+}
+
+func (h *Headscale) generateACLRules() (*[]tailcfg.FilterRule, error) {
+	rules := []tailcfg.FilterRule{}
+
+	for i, a := range h.aclPolicy.ACLs {
+		if a.Action != "accept" {
+			return nil, errorInvalidAction
+		}
+
+		r := tailcfg.FilterRule{}
+
+		srcIPs := []string{}
+		for j, u := range a.Users {
+			srcs, err := h.generateACLPolicySrcIP(u)
+			if err != nil {
+				log.Printf("Error parsing ACL %d, User %d", i, j)
+				return nil, err
+			}
+			srcIPs = append(srcIPs, *srcs...)
+		}
+		r.SrcIPs = srcIPs
+
+		destPorts := []tailcfg.NetPortRange{}
+		for j, d := range a.Ports {
+			dests, err := h.generateACLPolicyDestPorts(d)
+			if err != nil {
+				log.Printf("Error parsing ACL %d, Port %d", i, j)
+				return nil, err
+			}
+			destPorts = append(destPorts, *dests...)
+		}
+
+		rules = append(rules, tailcfg.FilterRule{
+			SrcIPs:   srcIPs,
+			DstPorts: destPorts,
+		})
+	}
+
+	return &rules, nil
+}
+
+func (h *Headscale) generateACLPolicySrcIP(u string) (*[]string, error) {
+	return h.expandAlias(u)
+}
+
+func (h *Headscale) generateACLPolicyDestPorts(d string) (*[]tailcfg.NetPortRange, error) {
+	tokens := strings.Split(d, ":")
+	if len(tokens) < 2 || len(tokens) > 3 {
+		return nil, errorInvalidPortFormat
+	}
+
+	var alias string
+	// We can have here stuff like:
+	// git-server:*
+	// 192.168.1.0/24:22
+	// tag:montreal-webserver:80,443
+	// tag:api-server:443
+	// example-host-1:*
+	if len(tokens) == 2 {
+		alias = tokens[0]
+	} else {
+		alias = fmt.Sprintf("%s:%s", tokens[0], tokens[1])
+	}
+
+	expanded, err := h.expandAlias(alias)
+	if err != nil {
+		return nil, err
+	}
+	ports, err := h.expandPorts(tokens[len(tokens)-1])
+	if err != nil {
+		return nil, err
+	}
+
+	dests := []tailcfg.NetPortRange{}
+	for _, d := range *expanded {
+		for _, p := range *ports {
+			pr := tailcfg.NetPortRange{
+				IP:    d,
+				Ports: p,
+			}
+			dests = append(dests, pr)
+		}
+	}
+	return &dests, nil
+}
+
+func (h *Headscale) expandAlias(s string) (*[]string, error) {
+	if s == "*" {
+		return &[]string{"*"}, nil
+	}
+
+	if strings.HasPrefix(s, "group:") {
+		if _, ok := h.aclPolicy.Groups[s]; !ok {
+			return nil, errorInvalidGroup
+		}
+		ips := []string{}
+		for _, n := range h.aclPolicy.Groups[s] {
+			nodes, err := h.ListMachinesInNamespace(n)
+			if err != nil {
+				return nil, errorInvalidNamespace
+			}
+			for _, node := range *nodes {
+				ips = append(ips, node.IPAddress)
+			}
+		}
+		return &ips, nil
+	}
+
+	if strings.HasPrefix(s, "tag:") {
+		if _, ok := h.aclPolicy.TagOwners[s]; !ok {
+			return nil, errorInvalidTag
+		}
+
+		// This will have HORRIBLE performance.
+		// We need to change the data model to better store tags
+		machines := []Machine{}
+		if err := h.db.Where("registered").Find(&machines).Error; err != nil {
+			return nil, err
+		}
+		ips := []string{}
+		for _, m := range machines {
+			hostinfo := tailcfg.Hostinfo{}
+			if len(m.HostInfo) != 0 {
+				hi, err := m.HostInfo.MarshalJSON()
+				if err != nil {
+					return nil, err
+				}
+				err = json.Unmarshal(hi, &hostinfo)
+				if err != nil {
+					return nil, err
+				}
+
+				// FIXME: Check TagOwners allows this
+				for _, t := range hostinfo.RequestTags {
+					if s[4:] == t {
+						ips = append(ips, m.IPAddress)
+						break
+					}
+				}
+			}
+		}
+		return &ips, nil
+	}
+
+	n, err := h.GetNamespace(s)
+	if err == nil {
+		nodes, err := h.ListMachinesInNamespace(n.Name)
+		if err != nil {
+			return nil, err
+		}
+		ips := []string{}
+		for _, n := range *nodes {
+			ips = append(ips, n.IPAddress)
+		}
+		return &ips, nil
+	}
+
+	if h, ok := h.aclPolicy.Hosts[s]; ok {
+		return &[]string{h.String()}, nil
+	}
+
+	ip, err := netaddr.ParseIP(s)
+	if err == nil {
+		return &[]string{ip.String()}, nil
+	}
+
+	cidr, err := netaddr.ParseIPPrefix(s)
+	if err == nil {
+		return &[]string{cidr.String()}, nil
+	}
+
+	return nil, errorInvalidUserSection
+}
+
+func (h *Headscale) expandPorts(s string) (*[]tailcfg.PortRange, error) {
+	if s == "*" {
+		return &[]tailcfg.PortRange{{First: 0, Last: 65535}}, nil
+	}
+
+	ports := []tailcfg.PortRange{}
+	for _, p := range strings.Split(s, ",") {
+		rang := strings.Split(p, "-")
+		if len(rang) == 1 {
+			pi, err := strconv.ParseUint(rang[0], 10, 16)
+			if err != nil {
+				return nil, err
+			}
+			ports = append(ports, tailcfg.PortRange{
+				First: uint16(pi),
+				Last:  uint16(pi),
+			})
+		} else if len(rang) == 2 {
+			start, err := strconv.ParseUint(rang[0], 10, 16)
+			if err != nil {
+				return nil, err
+			}
+			last, err := strconv.ParseUint(rang[1], 10, 16)
+			if err != nil {
+				return nil, err
+			}
+			ports = append(ports, tailcfg.PortRange{
+				First: uint16(start),
+				Last:  uint16(last),
+			})
+		} else {
+			return nil, errorInvalidPortFormat
+		}
+	}
+	return &ports, nil
+}