net: allow a dns TXT record to contain more than one <character-string>

RFC 1035 3.3.14 allows a TXT record to contain one or more <character-string>s.
The current implementation returns a "no such host" error if there is more
than one <character-string> in the TXT record.

Fixes #10482

Change-Id: I0ded258005e6b7ba45f687fecd10afa2b321bb77
Reviewed-on: https://go-review.googlesource.com/8966
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>

diff --git a/src/net/dnsmsg.go b/src/net/dnsmsg.go
index 161afb2a55675eaaa855c4840c97b4c9af3c2e18..6ecaa9482304f7b1b1a9eb90814e60350a9192c9 100644 (file)
--- a/src/net/dnsmsg.go
+++ b/src/net/dnsmsg.go
@@ -306,7 +306,23 @@ func (rr *dnsRR_TXT) Header() *dnsRR_Header {
 }
 
 func (rr *dnsRR_TXT) Walk(f func(v interface{}, name, tag string) bool) bool {
-       return rr.Hdr.Walk(f) && f(&rr.Txt, "Txt", "")
+       if !rr.Hdr.Walk(f) {
+               return false
+       }
+       var n uint16 = 0
+       for n < rr.Hdr.Rdlength {
+               var txt string
+               if !f(&txt, "Txt", "") {
+                       return false
+               }
+               // more bytes than rr.Hdr.Rdlength said there woudld be
+               if rr.Hdr.Rdlength-n < uint16(len(txt))+1 {
+                       return false
+               }
+               n += uint16(len(txt)) + 1
+               rr.Txt += txt
+       }
+       return true
 }
 
 type dnsRR_SRV struct {

diff --git a/src/net/dnsmsg_test.go b/src/net/dnsmsg_test.go
index 159a03e5252a6e301991148cafea7a4067ff35fc..655d5c0a8f80988e3bba95fd96ee4f7ac94fa752 100644 (file)
--- a/src/net/dnsmsg_test.go
+++ b/src/net/dnsmsg_test.go
@@ -96,6 +96,93 @@ func TestDNSParseCorruptSRVReply(t *testing.T) {
        }
 }
 
+func TestDNSParseTXTReply(t *testing.T) {
+       expectedTxt1 := "v=spf1 redirect=_spf.google.com"
+       expectedTxt2 := "v=spf1 ip4:69.63.179.25 ip4:69.63.178.128/25 ip4:69.63.184.0/25 " +
+               "ip4:66.220.144.128/25 ip4:66.220.155.0/24 " +
+               "ip4:69.171.232.0/25 ip4:66.220.157.0/25 " +
+               "ip4:69.171.244.0/24 mx -all"
+
+       replies := []string{dnsTXTReply1, dnsTXTReply2}
+       expectedTxts := []string{expectedTxt1, expectedTxt2}
+
+       for i := range replies {
+               data, err := hex.DecodeString(replies[i])
+               if err != nil {
+                       t.Fatal(err)
+               }
+
+               msg := new(dnsMsg)
+               ok := msg.Unpack(data)
+               if !ok {
+                       t.Errorf("test %d: unpacking packet failed", i)
+                       continue
+               }
+
+               if len(msg.answer) != 1 {
+                       t.Errorf("test %d: len(rr.answer) = %d; want 1", i, len(msg.answer))
+                       continue
+               }
+
+               rr := msg.answer[0]
+               rrTXT, ok := rr.(*dnsRR_TXT)
+               if !ok {
+                       t.Errorf("test %d: answer[0] = %T; want *dnsRR_TXT", i, rr)
+                       continue
+               }
+
+               if rrTXT.Txt != expectedTxts[i] {
+                       t.Errorf("test %d: Txt = %s; want %s", i, rrTXT.Txt, expectedTxts[i])
+               }
+       }
+}
+
+func TestDNSParseTXTCorruptDataLengthReply(t *testing.T) {
+       replies := []string{dnsTXTCorruptDataLengthReply1, dnsTXTCorruptDataLengthReply2}
+
+       for i := range replies {
+               data, err := hex.DecodeString(replies[i])
+               if err != nil {
+                       t.Fatal(err)
+               }
+
+               msg := new(dnsMsg)
+               ok := msg.Unpack(data)
+               if ok {
+                       t.Errorf("test %d: expected to fail on unpacking corrupt packet", i)
+               }
+       }
+}
+
+func TestDNSParseTXTCorruptTXTLengthReply(t *testing.T) {
+       replies := []string{dnsTXTCorruptTXTLengthReply1, dnsTXTCorruptTXTLengthReply2}
+
+       for i := range replies {
+               data, err := hex.DecodeString(replies[i])
+               if err != nil {
+                       t.Fatal(err)
+               }
+
+               msg := new(dnsMsg)
+               ok := msg.Unpack(data)
+               // Unpacking should succeed, but we should just get the header.
+               if !ok {
+                       t.Errorf("test %d: unpacking packet failed", i)
+                       continue
+               }
+
+               if len(msg.answer) != 1 {
+                       t.Errorf("test %d: len(rr.answer) = %d; want 1", i, len(msg.answer))
+                       continue
+               }
+
+               rr := msg.answer[0]
+               if _, justHeader := rr.(*dnsRR_Header); !justHeader {
+                       t.Errorf("test %d: rr = %T; expected *dnsRR_Header", i, rr)
+               }
+       }
+}
+
 // Valid DNS SRV reply
 const dnsSRVReply = "0901818000010005000000000c5f786d70702d736572766572045f74637006676f6f67" +
        "6c6503636f6d0000210001c00c002100010000012c00210014000014950c786d70702d" +
@@ -117,3 +204,63 @@ const dnsSRVCorruptReply = "0901818000010005000000000c5f786d70702d73657276657204
        "6503636f6d00c00c002100010000012c00200005000014950b786d70702d7365727665" +
        "72016c06676f6f676c6503636f6d00c00c002100010000012c00FF0014000014950c78" +
        "6d70702d73657276657231016c06676f6f676c6503636f6d00"
+
+// TXT reply with one <character-string>
+const dnsTXTReply1 = "b3458180000100010004000505676d61696c03636f6d0000100001c00c001000010000012c00" +
+       "201f763d737066312072656469726563743d5f7370662e676f6f676c652e636f6dc00" +
+       "c0002000100025d4c000d036e733406676f6f676c65c012c00c0002000100025d4c00" +
+       "06036e7331c057c00c0002000100025d4c0006036e7333c057c00c0002000100025d4" +
+       "c0006036e7332c057c06c00010001000248b50004d8ef200ac09000010001000248b5" +
+       "0004d8ef220ac07e00010001000248b50004d8ef240ac05300010001000248b50004d" +
+       "8ef260a0000291000000000000000"
+
+// TXT reply with more than one <character-string>.
+// See https://tools.ietf.org/html/rfc1035#section-3.3.14
+const dnsTXTReply2 = "a0a381800001000100020002045f7370660866616365626f6f6b03636f6d0000100001c00c0010000" +
+       "100000e1000af7f763d73706631206970343a36392e36332e3137392e3235206970343a36392e" +
+       "36332e3137382e3132382f3235206970343a36392e36332e3138342e302f3235206970343a363" +
+       "62e3232302e3134342e3132382f3235206970343a36362e3232302e3135352e302f3234206970" +
+       "343a36392e3137312e3233322e302f323520692e70343a36362e3232302e3135372e302f32352" +
+       "06970343a36392e3137312e3234342e302f3234206d78202d616c6cc0110002000100025d1500" +
+       "070161026e73c011c0110002000100025d1500040162c0ecc0ea0001000100025d15000445abe" +
+       "f0cc0fd0001000100025d15000445abff0c"
+
+// DataLength field should be sum of all TXT fields. In this case it's less.
+const dnsTXTCorruptDataLengthReply1 = "a0a381800001000100020002045f7370660866616365626f6f6b03636f6d0000100001c00c0010000" +
+       "100000e1000967f763d73706631206970343a36392e36332e3137392e3235206970343a36392e" +
+       "36332e3137382e3132382f3235206970343a36392e36332e3138342e302f3235206970343a363" +
+       "62e3232302e3134342e3132382f3235206970343a36362e3232302e3135352e302f3234206970" +
+       "343a36392e3137312e3233322e302f323520692e70343a36362e3232302e3135372e302f32352" +
+       "06970343a36392e3137312e3234342e302f3234206d78202d616c6cc0110002000100025d1500" +
+       "070161026e73c011c0110002000100025d1500040162c0ecc0ea0001000100025d15000445abe" +
+       "f0cc0fd0001000100025d15000445abff0c"
+
+// Same as above but DataLength is more than sum of TXT fields.
+const dnsTXTCorruptDataLengthReply2 = "a0a381800001000100020002045f7370660866616365626f6f6b03636f6d0000100001c00c0010000" +
+       "100000e1001227f763d73706631206970343a36392e36332e3137392e3235206970343a36392e" +
+       "36332e3137382e3132382f3235206970343a36392e36332e3138342e302f3235206970343a363" +
+       "62e3232302e3134342e3132382f3235206970343a36362e3232302e3135352e302f3234206970" +
+       "343a36392e3137312e3233322e302f323520692e70343a36362e3232302e3135372e302f32352" +
+       "06970343a36392e3137312e3234342e302f3234206d78202d616c6cc0110002000100025d1500" +
+       "070161026e73c011c0110002000100025d1500040162c0ecc0ea0001000100025d15000445abe" +
+       "f0cc0fd0001000100025d15000445abff0c"
+
+// TXT Length field is less than actual length.
+const dnsTXTCorruptTXTLengthReply1 = "a0a381800001000100020002045f7370660866616365626f6f6b03636f6d0000100001c00c0010000" +
+       "100000e1000af7f763d73706631206970343a36392e36332e3137392e3235206970343a36392e" +
+       "36332e3137382e3132382f3235206970343a36392e36332e3138342e302f3235206970343a363" +
+       "62e3232302e3134342e3132382f3235206970343a36362e3232302e3135352e302f3234206970" +
+       "343a36392e3137312e3233322e302f323520691470343a36362e3232302e3135372e302f32352" +
+       "06970343a36392e3137312e3234342e302f3234206d78202d616c6cc0110002000100025d1500" +
+       "070161026e73c011c0110002000100025d1500040162c0ecc0ea0001000100025d15000445abe" +
+       "f0cc0fd0001000100025d15000445abff0c"
+
+// TXT Length field is more than actual length.
+const dnsTXTCorruptTXTLengthReply2 = "a0a381800001000100020002045f7370660866616365626f6f6b03636f6d0000100001c00c0010000" +
+       "100000e1000af7f763d73706631206970343a36392e36332e3137392e3235206970343a36392e" +
+       "36332e3137382e3132382f3235206970343a36392e36332e3138342e302f3235206970343a363" +
+       "62e3232302e3134342e3132382f3235206970343a36362e3232302e3135352e302f3234206970" +
+       "343a36392e3137312e3233322e302f323520693370343a36362e3232302e3135372e302f32352" +
+       "06970343a36392e3137312e3234342e302f3234206d78202d616c6cc0110002000100025d1500" +
+       "070161026e73c011c0110002000100025d1500040162c0ecc0ea0001000100025d15000445abe" +
+       "f0cc0fd0001000100025d15000445abff0c"