[service] Subscribe to systemd-resolver events

service/firewall/interception/dnslistener/module.go

@@ -0,0 +1,171 @@
+package dnslistener
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"sync/atomic"
+
+	"github.com/miekg/dns"
+	"github.com/safing/portmaster/base/log"
+	"github.com/safing/portmaster/service/mgr"
+	"github.com/safing/portmaster/service/network/netutils"
+	"github.com/safing/portmaster/service/resolver"
+	"github.com/varlink/go/varlink"
+)
+
+var ResolverInfo = resolver.ResolverInfo{
+	Name:   "SystemdResolver",
+	Type:   "env",
+	Source: "System",
+}
+
+type DNSListener struct {
+	instance instance
+	mgr      *mgr.Manager
+
+	varlinkConn *varlink.Connection
+}
+
+func (dl *DNSListener) Manager() *mgr.Manager {
+	return dl.mgr
+}
+
+func (dl *DNSListener) Start() error {
+	var err error
+
+	// Create the varlink connection with the systemd resolver.
+	dl.varlinkConn, err = varlink.NewConnection(dl.mgr.Ctx(), "unix:/run/systemd/resolve/io.systemd.Resolve.Monitor")
+	if err != nil {
+		log.Errorf("dnslistener: failed to connect to systemd-resolver varlink service: %s", err)
+		return nil
+	}
+
+	dl.mgr.Go("systemd-resolver-event-listener", func(w *mgr.WorkerCtx) error {
+		// Subscribe to the dns query events
+		receive, err := dl.varlinkConn.Send(dl.mgr.Ctx(), "io.systemd.Resolve.Monitor.SubscribeQueryResults", nil, varlink.More)
+		if err != nil {
+			if varlinkErr, ok := err.(*varlink.Error); ok {
+				return fmt.Errorf("failed to issue Varlink call: %+v", varlinkErr.Parameters)
+			} else {
+				return fmt.Errorf("failed to issue Varlink call: %v", err)
+			}
+		}
+
+		for {
+			queryResult := QueryResult{}
+			// Receive the next event from the resolver.
+			flags, err := receive(w.Ctx(), &queryResult)
+			if err != nil {
+				if varlinkErr, ok := err.(*varlink.Error); ok {
+					return fmt.Errorf("failed to receive Varlink reply: %+v", varlinkErr.Parameters)
+				} else {
+					return fmt.Errorf("failed to receive Varlink reply: %v", err)
+				}
+			}
+
+			// Check if the reply indicates the end of the stream
+			if flags&varlink.Continues == 0 {
+				break
+			}
+
+			if queryResult.Rcode != nil {
+				continue // Ignore DNS errors
+			}
+
+			dl.processAnswer(&queryResult)
+
+		}
+
+		return nil
+	})
+
+	return nil
+}
+
+func (dl *DNSListener) processAnswer(queryResult *QueryResult) {
+	// Allocated data struct for the parsed result.
+	cnames := make(map[string]string)
+	ips := make([]net.IP, 0, 5)
+
+	// Check if the query is valid
+	if queryResult.Question == nil || len(*queryResult.Question) == 0 || queryResult.Answer == nil {
+		return
+	}
+
+	domain := (*queryResult.Question)[0].Name
+
+	// Go trough each answer entry.
+	for _, a := range *queryResult.Answer {
+		if a.RR.Address != nil {
+			ip := net.IP(*a.RR.Address)
+			// Answer contains ip address.
+			ips = append(ips, ip)
+
+		} else if a.RR.Name != nil {
+			// Answer is a CNAME.
+			cnames[domain] = *a.RR.Name
+		}
+	}
+
+	for _, ip := range ips {
+		// Never save domain attributions for localhost IPs.
+		if netutils.GetIPScope(ip) == netutils.HostLocal {
+			continue
+		}
+		fqdn := dns.Fqdn(domain)
+
+		// Create new record for this IP.
+		record := resolver.ResolvedDomain{
+			Domain:            fqdn,
+			Resolver:          &ResolverInfo,
+			DNSRequestContext: &resolver.DNSRequestContext{},
+			Expires:           0,
+		}
+
+		for {
+			nextDomain, isCNAME := cnames[domain]
+			if !isCNAME {
+				break
+			}
+
+			record.CNAMEs = append(record.CNAMEs, nextDomain)
+			domain = nextDomain
+		}
+
+		info := resolver.IPInfo{
+			IP: ip.String(),
+		}
+
+		// Add the new record to the resolved domains for this IP and scope.
+		info.AddDomain(record)
+
+		// Save if the record is new or has been updated.
+		if err := info.Save(); err != nil {
+			log.Errorf("nameserver: failed to save IP info record: %s", err)
+		}
+	}
+}
+
+func (dl *DNSListener) Stop() error {
+	if dl.varlinkConn != nil {
+		_ = dl.varlinkConn.Close()
+	}
+	return nil
+}
+
+var shimLoaded atomic.Bool
+
+func New(instance instance) (*DNSListener, error) {
+	if !shimLoaded.CompareAndSwap(false, true) {
+		return nil, errors.New("only one instance allowed")
+	}
+	m := mgr.New("DNSListener")
+	module := &DNSListener{
+		mgr:      m,
+		instance: instance,
+	}
+	return module, nil
+}
+
+type instance interface{}

service/firewall/interception/dnslistener/varlinktypes.go

@@ -0,0 +1,79 @@
+package dnslistener
+
+// List of struct that define the systemd-resolver varlink dns event protocol.
+
+type ResourceKey struct {
+	Class int    `json:"class"`
+	Type  int    `json:"type"`
+	Name  string `json:"name"`
+}
+
+type ResourceRecord struct {
+	Key     ResourceKey `json:"key"`
+	Name    *string     `json:"name,omitempty"`
+	Address *[]byte     `json:"address,omitempty"`
+	// Rest of the fields are not used.
+	// Priority     *int        `json:"priority,omitempty"`
+	// Weight       *int        `json:"weight,omitempty"`
+	// Port         *int        `json:"port,omitempty"`
+	// CPU          *string     `json:"cpu,omitempty"`
+	// OS           *string     `json:"os,omitempty"`
+	// Items        *[]string   `json:"items,omitempty"`
+	// MName        *string     `json:"mname,omitempty"`
+	// RName        *string     `json:"rname,omitempty"`
+	// Serial       *int        `json:"serial,omitempty"`
+	// Refresh      *int        `json:"refresh,omitempty"`
+	// Expire       *int        `json:"expire,omitempty"`
+	// Minimum      *int        `json:"minimum,omitempty"`
+	// Exchange     *string     `json:"exchange,omitempty"`
+	// Version      *int        `json:"version,omitempty"`
+	// Size         *int        `json:"size,omitempty"`
+	// HorizPre     *int        `json:"horiz_pre,omitempty"`
+	// VertPre      *int        `json:"vert_pre,omitempty"`
+	// Latitude     *int        `json:"latitude,omitempty"`
+	// Longitude    *int        `json:"longitude,omitempty"`
+	// Altitude     *int        `json:"altitude,omitempty"`
+	// KeyTag       *int        `json:"key_tag,omitempty"`
+	// Algorithm    *int        `json:"algorithm,omitempty"`
+	// DigestType   *int        `json:"digest_type,omitempty"`
+	// Digest       *string     `json:"digest,omitempty"`
+	// FPType       *int        `json:"fptype,omitempty"`
+	// Fingerprint  *string     `json:"fingerprint,omitempty"`
+	// Flags        *int        `json:"flags,omitempty"`
+	// Protocol     *int        `json:"protocol,omitempty"`
+	// DNSKey       *string     `json:"dnskey,omitempty"`
+	// Signer       *string     `json:"signer,omitempty"`
+	// TypeCovered  *int        `json:"type_covered,omitempty"`
+	// Labels       *int        `json:"labels,omitempty"`
+	// OriginalTTL  *int        `json:"original_ttl,omitempty"`
+	// Expiration   *int        `json:"expiration,omitempty"`
+	// Inception    *int        `json:"inception,omitempty"`
+	// Signature    *string     `json:"signature,omitempty"`
+	// NextDomain   *string     `json:"next_domain,omitempty"`
+	// Types        *[]int      `json:"types,omitempty"`
+	// Iterations   *int        `json:"iterations,omitempty"`
+	// Salt         *string     `json:"salt,omitempty"`
+	// Hash         *string     `json:"hash,omitempty"`
+	// CertUsage    *int        `json:"cert_usage,omitempty"`
+	// Selector     *int        `json:"selector,omitempty"`
+	// MatchingType *int        `json:"matching_type,omitempty"`
+	// Data         *string     `json:"data,omitempty"`
+	// Tag          *string     `json:"tag,omitempty"`
+	// Value        *string     `json:"value,omitempty"`
+}
+
+type Answer struct {
+	RR      *ResourceRecord `json:"rr,omitempty"`
+	Raw     string          `json:"raw"`
+	IfIndex *int            `json:"ifindex,omitempty"`
+}
+
+type QueryResult struct {
+	Ready              *bool          `json:"ready,omitempty"`
+	State              *string        `json:"state,omitempty"`
+	Rcode              *int           `json:"rcode,omitempty"`
+	Errno              *int           `json:"errno,omitempty"`
+	Question           *[]ResourceKey `json:"question,omitempty"`
+	CollectedQuestions *[]ResourceKey `json:"collectedQuestions,omitempty"`
+	Answer             *[]Answer      `json:"answer,omitempty"`
+}

service/instance.go

@@ -19,6 +19,7 @@ import (
 	"github.com/safing/portmaster/service/core/base"
 	"github.com/safing/portmaster/service/firewall"
 	"github.com/safing/portmaster/service/firewall/interception"
+	"github.com/safing/portmaster/service/firewall/interception/dnslistener"
 	"github.com/safing/portmaster/service/intel/customlists"
 	"github.com/safing/portmaster/service/intel/filterlists"
 	"github.com/safing/portmaster/service/intel/geoip"
@@ -74,6 +75,7 @@ type Instance struct {
 	firewall     *firewall.Firewall
 	filterLists  *filterlists.FilterLists
 	interception *interception.Interception
+	dnslistener  *dnslistener.DNSListener
 	customlist   *customlists.CustomList
 	status       *status.Status
 	broadcasts   *broadcasts.Broadcasts
@@ -187,6 +189,10 @@ func New(svcCfg *ServiceConfig) (*Instance, error) { //nolint:maintidx
 	if err != nil {
 		return instance, fmt.Errorf("create interception module: %w", err)
 	}
+	instance.dnslistener, err = dnslistener.New(instance)
+	if err != nil {
+		return instance, fmt.Errorf("create dns-listener module: %w", err)
+	}
 	instance.customlist, err = customlists.New(instance)
 	if err != nil {
 		return instance, fmt.Errorf("create customlist module: %w", err)
@@ -288,6 +294,7 @@ func New(svcCfg *ServiceConfig) (*Instance, error) { //nolint:maintidx
 		instance.filterLists,
 		instance.customlist,
 		instance.interception,
+		instance.dnslistener,
 
 		instance.compat,
 		instance.status,
@@ -463,6 +470,11 @@ func (i *Instance) Interception() *interception.Interception {
 	return i.interception
 }
 
+// DNSListener returns the dns-listener module.
+func (i *Instance) DNSListener() *dnslistener.DNSListener {
+	return i.dnslistener
+}
+
 // CustomList returns the customlist module.
 func (i *Instance) CustomList() *customlists.CustomList {
 	return i.customlist