Pull request: 3381 check private domains

Merge in DNS/adguard-home from 3381-validate-privateness to master

Closes #3381.

Squashed commit of the following:

commit 21cb12d10b07bb0bf0578db74ca9ac7b3ac5ae14
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Feb 14 16:29:59 2022 +0300

    all: imp code, docs

commit 39793551438cbea71e6ec78d0e05bee2d8dba3e5
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Feb 14 15:08:36 2022 +0300

    all: imp code, docs

commit 6b71848fd0980582b1bfe24a34f48608795e9b7d
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Feb 14 14:22:00 2022 +0300

    all: check private domains

CHANGELOG.md

@@ -21,6 +21,11 @@ and this project adheres to
 
 ### Changed
 
+- Domain-specific private reverse DNS upstream servers are now validated to
+  allow only `*.in-addr.arpa` and `*.ip6.arpa` domains pointing to
+  locally-served networks ([#3381]).  **Note:**  If you already have invalid
+  entires in your configuration, consider removing them manually, since they
+  essentially had no effect.
 - Response filtering is now performed using the record types of the answer
   section of messages as opposed to the type of the question ([#4238]).
 - Instead of adding the build time information, the build scripts now use the
@@ -80,6 +85,7 @@ In this release, the schema version has changed from 12 to 13.
 [#2993]: https://github.com/AdguardTeam/AdGuardHome/issues/2993
 [#3057]: https://github.com/AdguardTeam/AdGuardHome/issues/3057
 [#3367]: https://github.com/AdguardTeam/AdGuardHome/issues/3367
+[#3381]: https://github.com/AdguardTeam/AdGuardHome/issues/3381
 [#3503]: https://github.com/AdguardTeam/AdGuardHome/issues/3503
 [#4216]: https://github.com/AdguardTeam/AdGuardHome/issues/4216
 [#4221]: https://github.com/AdguardTeam/AdGuardHome/issues/4221

go.mod

@@ -4,7 +4,7 @@ go 1.17
 
 require (
 	github.com/AdguardTeam/dnsproxy v0.41.1
-	github.com/AdguardTeam/golibs v0.10.4
+	github.com/AdguardTeam/golibs v0.10.5
 	github.com/AdguardTeam/urlfilter v0.15.2
 	github.com/NYTimes/gziphandler v1.1.1
 	github.com/ameshkov/dnscrypt/v2 v2.2.3

go.sum

@@ -12,8 +12,9 @@ github.com/AdguardTeam/dnsproxy v0.41.1/go.mod h1:PZ9l22h3Er+5mxFQB7oHZMTvx+aa9R
 github.com/AdguardTeam/golibs v0.4.0/go.mod h1:skKsDKIBB7kkFflLJBpfGX+G8QFTx0WKUzB6TIgtUj4=
 github.com/AdguardTeam/golibs v0.4.2/go.mod h1:skKsDKIBB7kkFflLJBpfGX+G8QFTx0WKUzB6TIgtUj4=
 github.com/AdguardTeam/golibs v0.10.3/go.mod h1:rSfQRGHIdgfxriDDNgNJ7HmE5zRoURq8R+VdR81Zuzw=
-github.com/AdguardTeam/golibs v0.10.4 h1:TMBkablZC0IZOpRgg9fzAKlxxNhSN2YJq7qbgtuZ7PQ=
 github.com/AdguardTeam/golibs v0.10.4/go.mod h1:rSfQRGHIdgfxriDDNgNJ7HmE5zRoURq8R+VdR81Zuzw=
+github.com/AdguardTeam/golibs v0.10.5 h1:4/nl1yIBJOv5luVu9SURW8LfgOjI3zQ2moIUy/1k0y4=
+github.com/AdguardTeam/golibs v0.10.5/go.mod h1:rSfQRGHIdgfxriDDNgNJ7HmE5zRoURq8R+VdR81Zuzw=
 github.com/AdguardTeam/gomitmproxy v0.2.0/go.mod h1:Qdv0Mktnzer5zpdpi5rAwixNJzW2FN91LjKJCkVbYGU=
 github.com/AdguardTeam/urlfilter v0.15.2 h1:LZGgrm4l4Ys9eAqB+UUmZfiC6vHlDlYFhx0WXqo6LtQ=
 github.com/AdguardTeam/urlfilter v0.15.2/go.mod h1:46YZDOV1+qtdRDuhZKVPSSp7JWWes0KayqHrKAFBdEI=

internal/aghnet/subnetdetector.go

@@ -6,16 +6,18 @@ import (
 
 // SubnetDetector describes IP address properties.
 type SubnetDetector struct {
-	// spNets is the slice of special-purpose address registries as defined
+	// spNets is the collection of special-purpose address registries as defined
-	// by RFC-6890 (https://tools.ietf.org/html/rfc6890).
+	// by RFC 6890.
 	spNets []*net.IPNet
 
-	// locServedNets is the slice of locally-served networks as defined by
+	// locServedNets is the collection of locally-served networks as defined by
-	// RFC-6303 (https://tools.ietf.org/html/rfc6303).
+	// RFC 6303.
 	locServedNets []*net.IPNet
 }
 
 // NewSubnetDetector returns a new IP detector.
+//
+// TODO(a.garipov):  Decide whether an error is actually needed.
 func NewSubnetDetector() (snd *SubnetDetector, err error) {
 	spNets := []string{
 		// "This" network.

internal/dnsforward/http.go

@@ -5,10 +5,12 @@ import (
 	"fmt"
 	"net"
 	"net/http"
+	"sort"
 	"strings"
 	"time"
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
+	"github.com/AdguardTeam/AdGuardHome/internal/aghnet"
 	"github.com/AdguardTeam/dnsproxy/proxy"
 	"github.com/AdguardTeam/dnsproxy/upstream"
 	"github.com/AdguardTeam/golibs/errors"
@@ -41,7 +43,7 @@ type dnsConfig struct {
 	LocalPTRUpstreams *[]string     `json:"local_ptr_upstreams"`
 }
 
-func (s *Server) getDNSConfig() dnsConfig {
+func (s *Server) getDNSConfig() (c *dnsConfig) {
 	s.serverLock.RLock()
 	defer s.serverLock.RUnlock()
 
@@ -70,7 +72,7 @@ func (s *Server) getDNSConfig() dnsConfig {
 		upstreamMode = "parallel"
 	}
 
-	return dnsConfig{
+	return &dnsConfig{
 		Upstreams:         &upstreams,
 		UpstreamsFile:     &upstreamFile,
 		Bootstraps:        &bootstraps,
@@ -106,7 +108,7 @@ func (s *Server) handleGetConfig(w http.ResponseWriter, r *http.Request) {
 		// since there is no need to omit it while decoding from JSON.
 		DefautLocalPTRUpstreams []string `json:"default_local_ptr_upstreams,omitempty"`
 	}{
-		dnsConfig:               s.getDNSConfig(),
+		dnsConfig:               *s.getDNSConfig(),
 		DefautLocalPTRUpstreams: defLocalPTRUps,
 	}
 
@@ -138,39 +140,63 @@ func (req *dnsConfig) checkBlockingMode() bool {
 }
 
 func (req *dnsConfig) checkUpstreamsMode() bool {
-	if req.UpstreamMode == nil {
+	valid := []string{"", "fastest_addr", "parallel"}
-		return true
-	}
 
-	for _, valid := range []string{
+	return req.UpstreamMode == nil || stringutil.InSlice(valid, *req.UpstreamMode)
-		"",
-		"fastest_addr",
-		"parallel",
-	} {
-		if *req.UpstreamMode == valid {
-			return true
-		}
-	}
-
-	return false
 }
 
-func (req *dnsConfig) checkBootstrap() (string, error) {
+func (req *dnsConfig) checkBootstrap() (err error) {
 	if req.Bootstraps == nil {
-		return "", nil
+		return nil
 	}
 
-	for _, boot := range *req.Bootstraps {
+	var b string
-		if boot == "" {
+	defer func() { err = errors.Annotate(err, "checking bootstrap %s: invalid address: %w", b) }()
-			return boot, fmt.Errorf("invalid bootstrap server address: empty")
+
+	for _, b = range *req.Bootstraps {
+		if b == "" {
+			return errors.Error("empty")
 		}
 
-		if _, err := upstream.NewResolver(boot, nil); err != nil {
+		if _, err = upstream.NewResolver(b, nil); err != nil {
-			return boot, fmt.Errorf("invalid bootstrap server address: %w", err)
+			return err
 		}
 	}
 
-	return "", nil
+	return nil
+}
+
+// validate returns an error if any field of req is invalid.
+func (req *dnsConfig) validate(snd *aghnet.SubnetDetector) (err error) {
+	if req.Upstreams != nil {
+		err = ValidateUpstreams(*req.Upstreams)
+		if err != nil {
+			return fmt.Errorf("validating upstream servers: %w", err)
+		}
+	}
+
+	if req.LocalPTRUpstreams != nil {
+		err = ValidateUpstreamsPrivate(*req.LocalPTRUpstreams, snd)
+		if err != nil {
+			return fmt.Errorf("validating private upstream servers: %w", err)
+		}
+	}
+
+	err = req.checkBootstrap()
+	if err != nil {
+		return err
+	}
+
+	switch {
+	case !req.checkBlockingMode():
+		return errors.Error("blocking_mode: incorrect value")
+	case !req.checkUpstreamsMode():
+		return errors.Error("upstream_mode: incorrect value")
+	case !req.checkCacheTTL():
+		return errors.Error("cache_ttl_min must be less or equal than cache_ttl_max")
+	default:
+		return nil
+	}
 }
 
 func (req *dnsConfig) checkCacheTTL() bool {
@@ -190,69 +216,33 @@ func (req *dnsConfig) checkCacheTTL() bool {
 }
 
 func (s *Server) handleSetConfig(w http.ResponseWriter, r *http.Request) {
-	req := dnsConfig{}
+	req := &dnsConfig{}
-	err := json.NewDecoder(r.Body).Decode(&req)
+	err := json.NewDecoder(r.Body).Decode(req)
 	if err != nil {
-		aghhttp.Error(r, w, http.StatusBadRequest, "json Encode: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "decoding request: %s", err)
 
 		return
 	}
 
-	if req.Upstreams != nil {
+	err = req.validate(s.subnetDetector)
-		if err = ValidateUpstreams(*req.Upstreams); err != nil {
+	if err != nil {
-			aghhttp.Error(r, w, http.StatusBadRequest, "wrong upstreams specification: %s", err)
+		aghhttp.Error(r, w, http.StatusBadRequest, "%s", err)
-
-			return
-		}
-	}
-
-	var errBoot string
-	if errBoot, err = req.checkBootstrap(); err != nil {
-		aghhttp.Error(
-			r,
-			w,
-			http.StatusBadRequest,
-			"%s can not be used as bootstrap dns cause: %s",
-			errBoot,
-			err,
-		)
 
 		return
 	}
 
-	switch {
-	case !req.checkBlockingMode():
-		aghhttp.Error(r, w, http.StatusBadRequest, "blocking_mode: incorrect value")
-
-		return
-	case !req.checkUpstreamsMode():
-		aghhttp.Error(r, w, http.StatusBadRequest, "upstream_mode: incorrect value")
-
-		return
-	case !req.checkCacheTTL():
-		aghhttp.Error(
-			r,
-			w,
-			http.StatusBadRequest,
-			"cache_ttl_min must be less or equal than cache_ttl_max",
-		)
-
-		return
-	default:
-		// Go on.
-	}
-
 	restart := s.setConfig(req)
 	s.conf.ConfigModified()
 
 	if restart {
-		if err = s.Reconfigure(nil); err != nil {
+		err = s.Reconfigure(nil)
+		if err != nil {
 			aghhttp.Error(r, w, http.StatusInternalServerError, "%s", err)
 		}
 	}
 }
 
-func (s *Server) setConfigRestartable(dc dnsConfig) (restart bool) {
+func (s *Server) setConfigRestartable(dc *dnsConfig) (restart bool) {
 	if dc.Upstreams != nil {
 		s.conf.UpstreamDNS = *dc.Upstreams
 		restart = true
@@ -273,9 +263,9 @@ func (s *Server) setConfigRestartable(dc dnsConfig) (restart bool) {
 		restart = true
 	}
 
-	if dc.RateLimit != nil {
+	if dc.RateLimit != nil && s.conf.Ratelimit != *dc.RateLimit {
-		restart = restart || s.conf.Ratelimit != *dc.RateLimit
 		s.conf.Ratelimit = *dc.RateLimit
+		restart = true
 	}
 
 	if dc.EDNSCSEnabled != nil {
@@ -306,7 +296,7 @@ func (s *Server) setConfigRestartable(dc dnsConfig) (restart bool) {
 	return restart
 }
 
-func (s *Server) setConfig(dc dnsConfig) (restart bool) {
+func (s *Server) setConfig(dc *dnsConfig) (restart bool) {
 	s.serverLock.Lock()
 	defer s.serverLock.Unlock()
 
@@ -353,52 +343,117 @@ type upstreamJSON struct {
 	PrivateUpstreams []string `json:"private_upstream"`
 }
 
-// IsCommentOrEmpty returns true of the string starts with a "#" character or is
+// IsCommentOrEmpty returns true if s starts with a "#" character or is empty.
-// an empty string.  This function is useful for filtering out non-upstream
+// This function is useful for filtering out non-upstream lines from upstream
-// lines from upstream configs.
+// configs.
 func IsCommentOrEmpty(s string) (ok bool) {
 	return len(s) == 0 || s[0] == '#'
 }
 
+// LocalNetChecker is used to check if the IP address belongs to a local
+// network.
+type LocalNetChecker interface {
+	// IsLocallyServedNetwork returns true if ip is contained in any of address
+	// registries defined by RFC 6303.
+	IsLocallyServedNetwork(ip net.IP) (ok bool)
+}
+
+// type check
+var _ LocalNetChecker = (*aghnet.SubnetDetector)(nil)
+
+// newUpstreamConfig validates upstreams and returns an appropriate upstream
+// configuration or nil if it can't be built.
+//
+// TODO(e.burkov):  Perhaps proxy.ParseUpstreamsConfig should validate upstreams
+// slice already so that this function may be considered useless.
+func newUpstreamConfig(upstreams []string) (conf *proxy.UpstreamConfig, err error) {
+	// No need to validate comments and empty lines.
+	upstreams = stringutil.FilterOut(upstreams, IsCommentOrEmpty)
+	if len(upstreams) == 0 {
+		// Consider this case valid since it means the default server should be
+		// used.
+		return nil, nil
+	}
+
+	conf, err = proxy.ParseUpstreamsConfig(
+		upstreams,
+		&upstream.Options{Bootstrap: []string{}, Timeout: DefaultTimeout},
+	)
+	if err != nil {
+		return nil, err
+	} else if len(conf.Upstreams) == 0 {
+		return nil, errors.Error("no default upstreams specified")
+	}
+
+	for _, u := range upstreams {
+		_, err = validateUpstream(u)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return conf, nil
+}
+
 // ValidateUpstreams validates each upstream and returns an error if any
 // upstream is invalid or if there are no default upstreams specified.
 //
-// TODO(e.burkov): Move into aghnet or even into dnsproxy.
+// TODO(e.burkov):  Move into aghnet or even into dnsproxy.
 func ValidateUpstreams(upstreams []string) (err error) {
-	// No need to validate comments
+	_, err = newUpstreamConfig(upstreams)
-	upstreams = stringutil.FilterOut(upstreams, IsCommentOrEmpty)
 
-	// Consider this case valid because defaultDNS will be used
+	return err
-	if len(upstreams) == 0 {
+}
-		return nil
+
+// stringKeysSorted returns the sorted slice of string keys of m.
+//
+// TODO(e.burkov):  Use generics in Go 1.18.  Move into golibs.
+func stringKeysSorted(m map[string][]upstream.Upstream) (sorted []string) {
+	sorted = make([]string, 0, len(m))
+	for s := range m {
+		sorted = append(sorted, s)
 	}
 
-	_, err = proxy.ParseUpstreamsConfig(
+	sort.Strings(sorted)
-		upstreams,
+
-		&upstream.Options{
+	return sorted
-			Bootstrap: []string{},
+}
-			Timeout:   DefaultTimeout,
+
-		},
+// ValidateUpstreamsPrivate validates each upstream and returns an error if any
-	)
+// upstream is invalid or if there are no default upstreams specified.  It also
+// checks each domain of domain-specific upstreams for being ARPA pointing to
+// a locally-served network.  lnc must not be nil.
+func ValidateUpstreamsPrivate(upstreams []string, lnc LocalNetChecker) (err error) {
+	conf, err := newUpstreamConfig(upstreams)
 	if err != nil {
 		return err
 	}
 
-	var defaultUpstreamFound bool
+	if conf == nil {
-	for _, u := range upstreams {
+		return nil
-		var useDefault bool
+	}
-		useDefault, err = validateUpstream(u)
+
+	var errs []error
+
+	for _, domain := range stringKeysSorted(conf.DomainReservedUpstreams) {
+		var subnet *net.IPNet
+		subnet, err = netutil.SubnetFromReversedAddr(domain)
 		if err != nil {
-			return err
+			errs = append(errs, err)
+
+			continue
 		}
 
-		if !defaultUpstreamFound {
+		if !lnc.IsLocallyServedNetwork(subnet.IP) {
-			defaultUpstreamFound = useDefault
+			errs = append(
+				errs,
+				fmt.Errorf("arpa domain %q should point to a locally-served network", domain),
+			)
 		}
 	}
 
-	if !defaultUpstreamFound {
+	if len(errs) > 0 {
-		return fmt.Errorf("no default upstreams specified")
+		return errors.List("checking domain-specific upstreams", errs...)
 	}
 
 	return nil

internal/dnsforward/http_test.go

@@ -184,12 +184,11 @@ func TestDNSForwardHTTP_handleSetConfig(t *testing.T) {
 		wantSet: "",
 	}, {
 		name: "upstream_dns_bad",
-		wantSet: `wrong upstreams specification: bad ipport address "!!!": address !!!: ` +
+		wantSet: `validating upstream servers: bad ipport address "!!!": ` +
-			`missing port in address`,
+			`address !!!: missing port in address`,
 	}, {
 		name: "bootstraps_bad",
-		wantSet: `a can not be used as bootstrap dns cause: ` +
+		wantSet: `checking bootstrap a: invalid address: ` +
-			`invalid bootstrap server address: ` +
 			`Resolver a is not eligible to be a bootstrap DNS server`,
 	}, {
 		name:    "cache_bad_ttl",
@@ -200,6 +199,10 @@ func TestDNSForwardHTTP_handleSetConfig(t *testing.T) {
 	}, {
 		name:    "local_ptr_upstreams_good",
 		wantSet: "",
+	}, {
+		name: "local_ptr_upstreams_bad",
+		wantSet: `validating private upstream servers: checking domain-specific upstreams: ` +
+			`bad arpa domain name "non.arpa": not a reversed ip network`,
 	}, {
 		name:    "local_ptr_upstreams_null",
 		wantSet: "",
@@ -350,7 +353,7 @@ func TestValidateUpstream(t *testing.T) {
 	}
 }
 
-func TestValidateUpstreamsSet(t *testing.T) {
+func TestValidateUpstreams(t *testing.T) {
 	testCases := []struct {
 		name    string
 		wantErr string
@@ -397,3 +400,52 @@ func TestValidateUpstreamsSet(t *testing.T) {
 		})
 	}
 }
+
+func TestValidateUpstreamsPrivate(t *testing.T) {
+	snd, err := aghnet.NewSubnetDetector()
+	require.NoError(t, err)
+
+	testCases := []struct {
+		name    string
+		wantErr string
+		u       string
+	}{{
+		name:    "success_address",
+		wantErr: ``,
+		u:       "[/1.0.0.127.in-addr.arpa/]#",
+	}, {
+		name:    "success_subnet",
+		wantErr: ``,
+		u:       "[/127.in-addr.arpa/]#",
+	}, {
+		name: "not_arpa_subnet",
+		wantErr: `checking domain-specific upstreams: ` +
+			`bad arpa domain name "hello.world": not a reversed ip network`,
+		u: "[/hello.world/]#",
+	}, {
+		name: "non-private_arpa_address",
+		wantErr: `checking domain-specific upstreams: ` +
+			`arpa domain "1.2.3.4.in-addr.arpa." should point to a locally-served network`,
+		u: "[/1.2.3.4.in-addr.arpa/]#",
+	}, {
+		name: "non-private_arpa_subnet",
+		wantErr: `checking domain-specific upstreams: ` +
+			`arpa domain "128.in-addr.arpa." should point to a locally-served network`,
+		u: "[/128.in-addr.arpa/]#",
+	}, {
+		name: "several_bad",
+		wantErr: `checking domain-specific upstreams: 2 errors: ` +
+			`"arpa domain \"1.2.3.4.in-addr.arpa.\" should point to a locally-served network", ` +
+			`"bad arpa domain name \"non.arpa\": not a reversed ip network"`,
+		u: "[/non.arpa/1.2.3.4.in-addr.arpa/127.in-addr.arpa/]#",
+	}}
+
+	for _, tc := range testCases {
+		set := []string{"192.168.0.1", tc.u}
+
+		t.Run(tc.name, func(t *testing.T) {
+			err = ValidateUpstreamsPrivate(set, snd)
+			testutil.AssertErrorMsg(t, tc.wantErr, err)
+		})
+	}
+}

internal/dnsforward/testdata/TestDNSForwardHTTP_handleSetConfig.json

@@ -520,6 +520,43 @@
       ]
     }
   },
+  "local_ptr_upstreams_bad": {
+    "req": {
+      "local_ptr_upstreams": [
+        "123.123.123.123",
+        "[/non.arpa/]#"
+      ]
+    },
+    "want": {
+      "upstream_dns": [
+        "8.8.8.8:53",
+        "8.8.4.4:53"
+      ],
+      "upstream_dns_file": "",
+      "bootstrap_dns": [
+        "9.9.9.10",
+        "149.112.112.10",
+        "2620:fe::10",
+        "2620:fe::fe:10"
+      ],
+      "protection_enabled": true,
+      "ratelimit": 0,
+      "blocking_mode": "",
+      "blocking_ipv4": "",
+      "blocking_ipv6": "",
+      "edns_cs_enabled": false,
+      "dnssec_enabled": false,
+      "disable_ipv6": false,
+      "upstream_mode": "",
+      "cache_size": 0,
+      "cache_ttl_min": 0,
+      "cache_ttl_max": 0,
+      "cache_optimistic": false,
+      "resolve_clients": false,
+      "use_private_ptr_resolvers": false,
+      "local_ptr_upstreams": []
+    }
+  },
   "local_ptr_upstreams_null": {
     "req": {
       "local_ptr_upstreams": null