[release-branch.go1.15] net: filter bad names from Lookup functions instead of hard failing

Instead of hard failing on a single bad record, filter the bad records and return anything valid. This only applies to the methods which can return multiple records, LookupMX, LookupNS, LookupSRV, and LookupAddr. When bad results are filtered out, also return an error, indicating that this filtering has happened. Updates #46241 Updates #46979 Fixes #47012 Change-Id: I6493e0002beaf89f5a9795333a93605abd30d171 Reviewed-on: https://go-review.googlesource.com/c/go/+/332549 Trust: Roland Shoemaker <roland@golang.org> Reviewed-by: Filippo Valsorda <filippo@golang.org> (cherry picked from commit 296ddf2a936a30866303a64d49bc0e3e034730a8) Reviewed-on: https://go-review.googlesource.com/c/go/+/333331 Run-TryBot: Roland Shoemaker <roland@golang.org>
author: Roland Shoemaker <roland@golang.org> 2021-07-02 10:25:49 -0700
committer: Roland Shoemaker <roland@golang.org> 2021-07-08 19:20:05 +0000
commit: 3d1d0664a58f376c21ec586bb73a8f451fdfde85 (patch)
tree: 7582a18a5da76408d9f804e9b18aa47a4c6ffc34
parent: 0579cf14060179a51300c157f3952528a6d25997 (diff)
download: go-3d1d0664a58f376c21ec586bb73a8f451fdfde85.tar.gz
go-3d1d0664a58f376c21ec586bb73a8f451fdfde85.zip
2 files changed, 235 insertions, 68 deletions
diff --git a/src/net/dnsclient_unix_test.go b/src/net/dnsclient_unix_test.go
index f0f6e577ad..9958a133a8 100644
--- a/src/net/dnsclient_unix_test.go
+++ b/src/net/dnsclient_unix_test.go
@@ -1846,6 +1846,17 @@ func TestCVE202133195(t *testing.T) {
 							Target: dnsmessage.MustNewName("<html>.golang.org."),
 						},
 					},
+					dnsmessage.Resource{
+						Header: dnsmessage.ResourceHeader{
+							Name:   n,
+							Type:   dnsmessage.TypeSRV,
+							Class:  dnsmessage.ClassINET,
+							Length: 4,
+						},
+						Body: &dnsmessage.SRVResource{
+							Target: dnsmessage.MustNewName("good.golang.org."),
+						},
+					},
 				)
 			case dnsmessage.TypeMX:
 				r.Answers = append(r.Answers,
@@ -1860,6 +1871,17 @@ func TestCVE202133195(t *testing.T) {
 							MX: dnsmessage.MustNewName("<html>.golang.org."),
 						},
 					},
+					dnsmessage.Resource{
+						Header: dnsmessage.ResourceHeader{
+							Name:   dnsmessage.MustNewName("good.golang.org."),
+							Type:   dnsmessage.TypeMX,
+							Class:  dnsmessage.ClassINET,
+							Length: 4,
+						},
+						Body: &dnsmessage.MXResource{
+							MX: dnsmessage.MustNewName("good.golang.org."),
+						},
+					},
 				)
 			case dnsmessage.TypeNS:
 				r.Answers = append(r.Answers,
@@ -1874,6 +1896,17 @@ func TestCVE202133195(t *testing.T) {
 							NS: dnsmessage.MustNewName("<html>.golang.org."),
 						},
 					},
+					dnsmessage.Resource{
+						Header: dnsmessage.ResourceHeader{
+							Name:   dnsmessage.MustNewName("good.golang.org."),
+							Type:   dnsmessage.TypeNS,
+							Class:  dnsmessage.ClassINET,
+							Length: 4,
+						},
+						Body: &dnsmessage.NSResource{
+							NS: dnsmessage.MustNewName("good.golang.org."),
+						},
+					},
 				)
 			case dnsmessage.TypePTR:
 				r.Answers = append(r.Answers,
@@ -1888,6 +1921,17 @@ func TestCVE202133195(t *testing.T) {
 							PTR: dnsmessage.MustNewName("<html>.golang.org."),
 						},
 					},
+					dnsmessage.Resource{
+						Header: dnsmessage.ResourceHeader{
+							Name:   dnsmessage.MustNewName("good.golang.org."),
+							Type:   dnsmessage.TypePTR,
+							Class:  dnsmessage.ClassINET,
+							Length: 4,
+						},
+						Body: &dnsmessage.PTRResource{
+							PTR: dnsmessage.MustNewName("good.golang.org."),
+						},
+					},
 				)
 			}
 			return r, nil
@@ -1903,58 +1947,137 @@ func TestCVE202133195(t *testing.T) {
 	defer func(orig string) { testHookHostsPath = orig }(testHookHostsPath)
 	testHookHostsPath = "testdata/hosts"
 
-	_, err := r.LookupCNAME(context.Background(), "golang.org")
-	if expected := "lookup golang.org: CNAME target is invalid"; err == nil || err.Error() != expected {
-		t.Errorf("Resolver.LookupCNAME returned unexpected error, got %q, want %q", err, expected)
-	}
-	_, err = LookupCNAME("golang.org")
-	if expected := "lookup golang.org: CNAME target is invalid"; err == nil || err.Error() != expected {
-		t.Errorf("LookupCNAME returned unexpected error, got %q, want %q", err, expected)
-	}
-
-	_, _, err = r.LookupSRV(context.Background(), "target", "tcp", "golang.org")
-	if expected := "lookup golang.org: SRV target is invalid"; err == nil || err.Error() != expected {
-		t.Errorf("Resolver.LookupSRV returned unexpected error, got %q, want %q", err, expected)
-	}
-	_, _, err = LookupSRV("target", "tcp", "golang.org")
-	if expected := "lookup golang.org: SRV target is invalid"; err == nil || err.Error() != expected {
-		t.Errorf("LookupSRV returned unexpected error, got %q, want %q", err, expected)
-	}
-
-	_, _, err = r.LookupSRV(context.Background(), "hdr", "tcp", "golang.org")
-	if expected := "lookup golang.org: SRV header name is invalid"; err == nil || err.Error() != expected {
-		t.Errorf("Resolver.LookupSRV returned unexpected error, got %q, want %q", err, expected)
-	}
-	_, _, err = LookupSRV("hdr", "tcp", "golang.org")
-	if expected := "lookup golang.org: SRV header name is invalid"; err == nil || err.Error() != expected {
-		t.Errorf("LookupSRV returned unexpected error, got %q, want %q", err, expected)
-	}
-
-	_, err = r.LookupMX(context.Background(), "golang.org")
-	if expected := "lookup golang.org: MX target is invalid"; err == nil || err.Error() != expected {
-		t.Errorf("Resolver.LookupMX returned unexpected error, got %q, want %q", err, expected)
-	}
-	_, err = LookupMX("golang.org")
-	if expected := "lookup golang.org: MX target is invalid"; err == nil || err.Error() != expected {
-		t.Errorf("LookupMX returned unexpected error, got %q, want %q", err, expected)
-	}
-
-	_, err = r.LookupNS(context.Background(), "golang.org")
-	if expected := "lookup golang.org: NS target is invalid"; err == nil || err.Error() != expected {
-		t.Errorf("Resolver.LookupNS returned unexpected error, got %q, want %q", err, expected)
-	}
-	_, err = LookupNS("golang.org")
-	if expected := "lookup golang.org: NS target is invalid"; err == nil || err.Error() != expected {
-		t.Errorf("LookupNS returned unexpected error, got %q, want %q", err, expected)
+	tests := []struct {
+		name string
+		f    func(*testing.T)
+	}{
+		{
+			name: "CNAME",
+			f: func(t *testing.T) {
+				expectedErr := &DNSError{Err: errMalformedDNSRecordsDetail, Name: "golang.org"}
+				_, err := r.LookupCNAME(context.Background(), "golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				_, err = LookupCNAME("golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+			},
+		},
+		{
+			name: "SRV (bad record)",
+			f: func(t *testing.T) {
+				expected := []*SRV{
+					{
+						Target: "good.golang.org.",
+					},
+				}
+				expectedErr := &DNSError{Err: errMalformedDNSRecordsDetail, Name: "golang.org"}
+				_, records, err := r.LookupSRV(context.Background(), "target", "tcp", "golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+				_, records, err = LookupSRV("target", "tcp", "golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Errorf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+			},
+		},
+		{
+			name: "SRV (bad header)",
+			f: func(t *testing.T) {
+				_, _, err := r.LookupSRV(context.Background(), "hdr", "tcp", "golang.org.")
+				if expected := "lookup golang.org.: SRV header name is invalid"; err == nil || err.Error() != expected {
+					t.Errorf("Resolver.LookupSRV returned unexpected error, got %q, want %q", err, expected)
+				}
+				_, _, err = LookupSRV("hdr", "tcp", "golang.org.")
+				if expected := "lookup golang.org.: SRV header name is invalid"; err == nil || err.Error() != expected {
+					t.Errorf("LookupSRV returned unexpected error, got %q, want %q", err, expected)
+				}
+			},
+		},
+		{
+			name: "MX",
+			f: func(t *testing.T) {
+				expected := []*MX{
+					{
+						Host: "good.golang.org.",
+					},
+				}
+				expectedErr := &DNSError{Err: errMalformedDNSRecordsDetail, Name: "golang.org"}
+				records, err := r.LookupMX(context.Background(), "golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+				records, err = LookupMX("golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+			},
+		},
+		{
+			name: "NS",
+			f: func(t *testing.T) {
+				expected := []*NS{
+					{
+						Host: "good.golang.org.",
+					},
+				}
+				expectedErr := &DNSError{Err: errMalformedDNSRecordsDetail, Name: "golang.org"}
+				records, err := r.LookupNS(context.Background(), "golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+				records, err = LookupNS("golang.org")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+			},
+		},
+		{
+			name: "Addr",
+			f: func(t *testing.T) {
+				expected := []string{"good.golang.org."}
+				expectedErr := &DNSError{Err: errMalformedDNSRecordsDetail, Name: "192.0.2.42"}
+				records, err := r.LookupAddr(context.Background(), "192.0.2.42")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+				records, err = LookupAddr("192.0.2.42")
+				if err.Error() != expectedErr.Error() {
+					t.Fatalf("unexpected error: %s", err)
+				}
+				if !reflect.DeepEqual(records, expected) {
+					t.Error("Unexpected record set")
+				}
+			},
+		},
 	}
 
-	_, err = r.LookupAddr(context.Background(), "192.0.2.42")
-	if expected := "lookup 192.0.2.42: PTR target is invalid"; err == nil || err.Error() != expected {
-		t.Errorf("Resolver.LookupAddr returned unexpected error, got %q, want %q", err, expected)
-	}
-	_, err = LookupAddr("192.0.2.42")
-	if expected := "lookup 192.0.2.42: PTR target is invalid"; err == nil || err.Error() != expected {
-		t.Errorf("LookupAddr returned unexpected error, got %q, want %q", err, expected)
+	for _, tc := range tests {
+		t.Run(tc.name, tc.f)
 	}
 }
 
diff --git a/src/net/lookup.go b/src/net/lookup.go
index 01c81dbaaf..4135122d60 100644
--- a/src/net/lookup.go
+++ b/src/net/lookup.go
@@ -415,7 +415,7 @@ func (r *Resolver) LookupCNAME(ctx context.Context, host string) (string, error)
 		return "", err
 	}
 	if !isDomainName(cname) {
-		return "", &DNSError{Err: "CNAME target is invalid", Name: host}
+		return "", &DNSError{Err: errMalformedDNSRecordsDetail, Name: host}
 	}
 	return cname, nil
 }
@@ -431,7 +431,9 @@ func (r *Resolver) LookupCNAME(ctx context.Context, host string) (string, error)
 // and proto are empty strings, LookupSRV looks up name directly.
 //
 // The returned service names are validated to be properly
-// formatted presentation-format domain names.
+// formatted presentation-format domain names. If the response contains
+// invalid names, those records are filtered out and an error
+// will be returned alongside the the remaining results, if any.
 func LookupSRV(service, proto, name string) (cname string, addrs []*SRV, err error) {
 	return DefaultResolver.LookupSRV(context.Background(), service, proto, name)
 }
@@ -447,7 +449,9 @@ func LookupSRV(service, proto, name string) (cname string, addrs []*SRV, err err
 // and proto are empty strings, LookupSRV looks up name directly.
 //
 // The returned service names are validated to be properly
-// formatted presentation-format domain names.
+// formatted presentation-format domain names. If the response contains
+// invalid names, those records are filtered out and an error
+// will be returned alongside the the remaining results, if any.
 func (r *Resolver) LookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV, error) {
 	cname, addrs, err := r.lookupSRV(ctx, service, proto, name)
 	if err != nil {
@@ -456,21 +460,31 @@ func (r *Resolver) LookupSRV(ctx context.Context, service, proto, name string) (
 	if cname != "" && !isDomainName(cname) {
 		return "", nil, &DNSError{Err: "SRV header name is invalid", Name: name}
 	}
+	filteredAddrs := make([]*SRV, 0, len(addrs))
 	for _, addr := range addrs {
 		if addr == nil {
 			continue
 		}
 		if !isDomainName(addr.Target) {
-			return "", nil, &DNSError{Err: "SRV target is invalid", Name: name}
+			continue
 		}
+		filteredAddrs = append(filteredAddrs, addr)
+	}
+	if len(addrs) != len(filteredAddrs) {
+		return cname, filteredAddrs, &DNSError{Err: errMalformedDNSRecordsDetail, Name: name}
 	}
-	return cname, addrs, nil
+	return cname, filteredAddrs, nil
 }
 
 // LookupMX returns the DNS MX records for the given domain name sorted by preference.
 //
 // The returned mail server names are validated to be properly
-// formatted presentation-format domain names.
+// formatted presentation-format domain names. If the response contains
+// invalid names, those records are filtered out and an error
+// will be returned alongside the the remaining results, if any.
+//
+// LookupMX uses context.Background internally; to specify the context, use
+// Resolver.LookupMX.
 func LookupMX(name string) ([]*MX, error) {
 	return DefaultResolver.LookupMX(context.Background(), name)
 }
@@ -478,12 +492,15 @@ func LookupMX(name string) ([]*MX, error) {
 // LookupMX returns the DNS MX records for the given domain name sorted by preference.
 //
 // The returned mail server names are validated to be properly
-// formatted presentation-format domain names.
+// formatted presentation-format domain names. If the response contains
+// invalid names, those records are filtered out and an error
+// will be returned alongside the the remaining results, if any.
 func (r *Resolver) LookupMX(ctx context.Context, name string) ([]*MX, error) {
 	records, err := r.lookupMX(ctx, name)
 	if err != nil {
 		return nil, err
 	}
+	filteredMX := make([]*MX, 0, len(records))
 	for _, mx := range records {
 		if mx == nil {
 			continue
@@ -491,16 +508,25 @@ func (r *Resolver) LookupMX(ctx context.Context, name string) ([]*MX, error) {
 		// Bypass the hostname validity check for targets which contain only a dot,
 		// as this is used to represent a 'Null' MX record.
 		if mx.Host != "." && !isDomainName(mx.Host) {
-			return nil, &DNSError{Err: "MX target is invalid", Name: name}
+			continue
 		}
+		filteredMX = append(filteredMX, mx)
+	}
+	if len(records) != len(filteredMX) {
+		return filteredMX, &DNSError{Err: errMalformedDNSRecordsDetail, Name: name}
 	}
-	return records, nil
+	return filteredMX, nil
 }
 
 // LookupNS returns the DNS NS records for the given domain name.
 //
 // The returned name server names are validated to be properly
-// formatted presentation-format domain names.
+// formatted presentation-format domain names. If the response contains
+// invalid names, those records are filtered out and an error
+// will be returned alongside the the remaining results, if any.
+//
+// LookupNS uses context.Background internally; to specify the context, use
+// Resolver.LookupNS.
 func LookupNS(name string) ([]*NS, error) {
 	return DefaultResolver.LookupNS(context.Background(), name)
 }
@@ -508,21 +534,28 @@ func LookupNS(name string) ([]*NS, error) {
 // LookupNS returns the DNS NS records for the given domain name.
 //
 // The returned name server names are validated to be properly
-// formatted presentation-format domain names.
+// formatted presentation-format domain names. If the response contains
+// invalid names, those records are filtered out and an error
+// will be returned alongside the the remaining results, if any.
 func (r *Resolver) LookupNS(ctx context.Context, name string) ([]*NS, error) {
 	records, err := r.lookupNS(ctx, name)
 	if err != nil {
 		return nil, err
 	}
+	filteredNS := make([]*NS, 0, len(records))
 	for _, ns := range records {
 		if ns == nil {
 			continue
 		}
 		if !isDomainName(ns.Host) {
-			return nil, &DNSError{Err: "NS target is invalid", Name: name}
+			continue
 		}
+		filteredNS = append(filteredNS, ns)
+	}
+	if len(records) != len(filteredNS) {
+		return filteredNS, &DNSError{Err: errMalformedDNSRecordsDetail, Name: name}
 	}
-	return records, nil
+	return filteredNS, nil
 }
 
 // LookupTXT returns the DNS TXT records for the given domain name.
@@ -539,7 +572,8 @@ func (r *Resolver) LookupTXT(ctx context.Context, name string) ([]string, error)
 // of names mapping to that address.
 //
 // The returned names are validated to be properly formatted presentation-format
-// domain names.
+// domain names. If the response contains invalid names, those records are filtered
+// out and an error will be returned alongside the the remaining results, if any.
 //
 // When using the host C library resolver, at most one result will be
 // returned. To bypass the host resolver, use a custom Resolver.
@@ -551,16 +585,26 @@ func LookupAddr(addr string) (names []string, err error) {
 // of names mapping to that address.
 //
 // The returned names are validated to be properly formatted presentation-format
-// domain names.
+// domain names. If the response contains invalid names, those records are filtered
+// out and an error will be returned alongside the the remaining results, if any.
 func (r *Resolver) LookupAddr(ctx context.Context, addr string) ([]string, error) {
 	names, err := r.lookupAddr(ctx, addr)
 	if err != nil {
 		return nil, err
 	}
+	filteredNames := make([]string, 0, len(names))
 	for _, name := range names {
-		if !isDomainName(name) {
-			return nil, &DNSError{Err: "PTR target is invalid", Name: addr}
+		if isDomainName(name) {
+			filteredNames = append(filteredNames, name)
 		}
 	}
-	return names, nil
+	if len(names) != len(filteredNames) {
+		return filteredNames, &DNSError{Err: errMalformedDNSRecordsDetail, Name: addr}
+	}
+	return filteredNames, nil
 }
+
+// errMalformedDNSRecordsDetail is the DNSError detail which is returned when a Resolver.Lookup...
+// method recieves DNS records which contain invalid DNS names. This may be returned alongside
+// results which have had the malformed records filtered out.
+var errMalformedDNSRecordsDetail = "DNS response contained records which contain invalid names"
author	Roland Shoemaker <roland@golang.org>	2021-07-02 10:25:49 -0700
committer	Roland Shoemaker <roland@golang.org>	2021-07-08 19:20:05 +0000
commit	3d1d0664a58f376c21ec586bb73a8f451fdfde85 (patch)
tree	7582a18a5da76408d9f804e9b18aa47a4c6ffc34
parent	0579cf14060179a51300c157f3952528a6d25997 (diff)
download	go-3d1d0664a58f376c21ec586bb73a8f451fdfde85.tar.gz go-3d1d0664a58f376c21ec586bb73a8f451fdfde85.zip