diff options
Diffstat (limited to 'vendor/github.com/google/gopacket/layers/dns.go')
-rw-r--r-- | vendor/github.com/google/gopacket/layers/dns.go | 894 |
1 files changed, 894 insertions, 0 deletions
diff --git a/vendor/github.com/google/gopacket/layers/dns.go b/vendor/github.com/google/gopacket/layers/dns.go new file mode 100644 index 0000000..2368a28 --- /dev/null +++ b/vendor/github.com/google/gopacket/layers/dns.go @@ -0,0 +1,894 @@ +// Copyright 2014 Google, Inc. All rights reserved. +// +// Use of this source code is governed by a BSD-style license +// that can be found in the LICENSE file in the root of the source +// tree. + +package layers + +import ( + "encoding/binary" + "errors" + "fmt" + "net" + + "github.com/google/gopacket" +) + +// DNSClass defines the class associated with a request/response. Different DNS +// classes can be thought of as an array of parallel namespace trees. +type DNSClass uint16 + +// DNSClass known values. +const ( + DNSClassIN DNSClass = 1 // Internet + DNSClassCS DNSClass = 2 // the CSNET class (Obsolete) + DNSClassCH DNSClass = 3 // the CHAOS class + DNSClassHS DNSClass = 4 // Hesiod [Dyer 87] + DNSClassAny DNSClass = 255 // AnyClass +) + +func (dc DNSClass) String() string { + switch dc { + default: + return "Unknown" + case DNSClassIN: + return "IN" + case DNSClassCS: + return "CS" + case DNSClassCH: + return "CH" + case DNSClassHS: + return "HS" + case DNSClassAny: + return "Any" + } +} + +// DNSType defines the type of data being requested/returned in a +// question/answer. +type DNSType uint16 + +// DNSType known values. +const ( + DNSTypeA DNSType = 1 // a host address + DNSTypeNS DNSType = 2 // an authoritative name server + DNSTypeMD DNSType = 3 // a mail destination (Obsolete - use MX) + DNSTypeMF DNSType = 4 // a mail forwarder (Obsolete - use MX) + DNSTypeCNAME DNSType = 5 // the canonical name for an alias + DNSTypeSOA DNSType = 6 // marks the start of a zone of authority + DNSTypeMB DNSType = 7 // a mailbox domain name (EXPERIMENTAL) + DNSTypeMG DNSType = 8 // a mail group member (EXPERIMENTAL) + DNSTypeMR DNSType = 9 // a mail rename domain name (EXPERIMENTAL) + DNSTypeNULL DNSType = 10 // a null RR (EXPERIMENTAL) + DNSTypeWKS DNSType = 11 // a well known service description + DNSTypePTR DNSType = 12 // a domain name pointer + DNSTypeHINFO DNSType = 13 // host information + DNSTypeMINFO DNSType = 14 // mailbox or mail list information + DNSTypeMX DNSType = 15 // mail exchange + DNSTypeTXT DNSType = 16 // text strings + DNSTypeAAAA DNSType = 28 // a IPv6 host address [RFC3596] + DNSTypeSRV DNSType = 33 // server discovery [RFC2782] [RFC6195] +) + +func (dt DNSType) String() string { + switch dt { + default: + return "Unknown" + case DNSTypeA: + return "A" + case DNSTypeNS: + return "NS" + case DNSTypeMD: + return "MD" + case DNSTypeMF: + return "MF" + case DNSTypeCNAME: + return "CNAME" + case DNSTypeSOA: + return "SOA" + case DNSTypeMB: + return "MB" + case DNSTypeMG: + return "MG" + case DNSTypeMR: + return "MR" + case DNSTypeNULL: + return "NULL" + case DNSTypeWKS: + return "WKS" + case DNSTypePTR: + return "PTR" + case DNSTypeHINFO: + return "HINFO" + case DNSTypeMINFO: + return "MINFO" + case DNSTypeMX: + return "MX" + case DNSTypeTXT: + return "TXT" + case DNSTypeAAAA: + return "AAAA" + case DNSTypeSRV: + return "SRV" + } +} + +// DNSResponseCode provides response codes for question answers. +type DNSResponseCode uint8 + +// DNSResponseCode known values. +const ( + DNSResponseCodeNoErr DNSResponseCode = 0 // No error + DNSResponseCodeFormErr DNSResponseCode = 1 // Format Error [RFC1035] + DNSResponseCodeServFail DNSResponseCode = 2 // Server Failure [RFC1035] + DNSResponseCodeNXDomain DNSResponseCode = 3 // Non-Existent Domain [RFC1035] + DNSResponseCodeNotImp DNSResponseCode = 4 // Not Implemented [RFC1035] + DNSResponseCodeRefused DNSResponseCode = 5 // Query Refused [RFC1035] + DNSResponseCodeYXDomain DNSResponseCode = 6 // Name Exists when it should not [RFC2136] + DNSResponseCodeYXRRSet DNSResponseCode = 7 // RR Set Exists when it should not [RFC2136] + DNSResponseCodeNXRRSet DNSResponseCode = 8 // RR Set that should exist does not [RFC2136] + DNSResponseCodeNotAuth DNSResponseCode = 9 // Server Not Authoritative for zone [RFC2136] + DNSResponseCodeNotZone DNSResponseCode = 10 // Name not contained in zone [RFC2136] + DNSResponseCodeBadVers DNSResponseCode = 16 // Bad OPT Version [RFC2671] + DNSResponseCodeBadSig DNSResponseCode = 16 // TSIG Signature Failure [RFC2845] + DNSResponseCodeBadKey DNSResponseCode = 17 // Key not recognized [RFC2845] + DNSResponseCodeBadTime DNSResponseCode = 18 // Signature out of time window [RFC2845] + DNSResponseCodeBadMode DNSResponseCode = 19 // Bad TKEY Mode [RFC2930] + DNSResponseCodeBadName DNSResponseCode = 20 // Duplicate key name [RFC2930] + DNSResponseCodeBadAlg DNSResponseCode = 21 // Algorithm not supported [RFC2930] + DNSResponseCodeBadTruc DNSResponseCode = 22 // Bad Truncation [RFC4635] +) + +func (drc DNSResponseCode) String() string { + switch drc { + default: + return "Unknown" + case DNSResponseCodeNoErr: + return "No Error" + case DNSResponseCodeFormErr: + return "Format Error" + case DNSResponseCodeServFail: + return "Server Failure " + case DNSResponseCodeNXDomain: + return "Non-Existent Domain" + case DNSResponseCodeNotImp: + return "Not Implemented" + case DNSResponseCodeRefused: + return "Query Refused" + case DNSResponseCodeYXDomain: + return "Name Exists when it should not" + case DNSResponseCodeYXRRSet: + return "RR Set Exists when it should not" + case DNSResponseCodeNXRRSet: + return "RR Set that should exist does not" + case DNSResponseCodeNotAuth: + return "Server Not Authoritative for zone" + case DNSResponseCodeNotZone: + return "Name not contained in zone" + case DNSResponseCodeBadVers: + return "Bad OPT Version" + case DNSResponseCodeBadKey: + return "Key not recognized" + case DNSResponseCodeBadTime: + return "Signature out of time window" + case DNSResponseCodeBadMode: + return "Bad TKEY Mode" + case DNSResponseCodeBadName: + return "Duplicate key name" + case DNSResponseCodeBadAlg: + return "Algorithm not supported" + case DNSResponseCodeBadTruc: + return "Bad Truncation" + } +} + +// DNSOpCode defines a set of different operation types. +type DNSOpCode uint8 + +// DNSOpCode known values. +const ( + DNSOpCodeQuery DNSOpCode = 0 // Query [RFC1035] + DNSOpCodeIQuery DNSOpCode = 1 // Inverse Query Obsolete [RFC3425] + DNSOpCodeStatus DNSOpCode = 2 // Status [RFC1035] + DNSOpCodeNotify DNSOpCode = 4 // Notify [RFC1996] + DNSOpCodeUpdate DNSOpCode = 5 // Update [RFC2136] +) + +func (doc DNSOpCode) String() string { + switch doc { + default: + return "Unknown" + case DNSOpCodeQuery: + return "Query" + case DNSOpCodeIQuery: + return "Inverse Query" + case DNSOpCodeStatus: + return "Status" + case DNSOpCodeNotify: + return "Notify" + case DNSOpCodeUpdate: + return "Update" + } +} + +// DNS is specified in RFC 1034 / RFC 1035 +// +---------------------+ +// | Header | +// +---------------------+ +// | Question | the question for the name server +// +---------------------+ +// | Answer | RRs answering the question +// +---------------------+ +// | Authority | RRs pointing toward an authority +// +---------------------+ +// | Additional | RRs holding additional information +// +---------------------+ +// +// DNS Header +// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +// | ID | +// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +// |QR| Opcode |AA|TC|RD|RA| Z | RCODE | +// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +// | QDCOUNT | +// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +// | ANCOUNT | +// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +// | NSCOUNT | +// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +// | ARCOUNT | +// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ + +// DNS contains data from a single Domain Name Service packet. +type DNS struct { + BaseLayer + + // Header fields + ID uint16 + QR bool + OpCode DNSOpCode + + AA bool // Authoritative answer + TC bool // Truncated + RD bool // Recursion desired + RA bool // Recursion available + Z uint8 // Resrved for future use + + ResponseCode DNSResponseCode + QDCount uint16 // Number of questions to expect + ANCount uint16 // Number of answers to expect + NSCount uint16 // Number of authorities to expect + ARCount uint16 // Number of additional records to expect + + // Entries + Questions []DNSQuestion + Answers []DNSResourceRecord + Authorities []DNSResourceRecord + Additionals []DNSResourceRecord + + // buffer for doing name decoding. We use a single reusable buffer to avoid + // name decoding on a single object via multiple DecodeFromBytes calls + // requiring constant allocation of small byte slices. + buffer []byte +} + +// LayerType returns gopacket.LayerTypeDNS. +func (d *DNS) LayerType() gopacket.LayerType { return LayerTypeDNS } + +// decodeDNS decodes the byte slice into a DNS type. It also +// setups the application Layer in PacketBuilder. +func decodeDNS(data []byte, p gopacket.PacketBuilder) error { + d := &DNS{} + err := d.DecodeFromBytes(data, p) + if err != nil { + return err + } + p.AddLayer(d) + p.SetApplicationLayer(d) + return nil +} + +// DecodeFromBytes decodes the slice into the DNS struct. +func (d *DNS) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error { + d.buffer = d.buffer[:0] + + if len(data) < 12 { + df.SetTruncated() + return errors.New("DNS packet too short") + } + + // since there are no further layers, the baselayer's content is + // pointing to this layer + d.BaseLayer = BaseLayer{Contents: data[:len(data)]} + d.ID = binary.BigEndian.Uint16(data[:2]) + d.QR = data[2]&0x80 != 0 + d.OpCode = DNSOpCode(data[2]>>3) & 0x0F + d.AA = data[2]&0x04 != 0 + d.TC = data[2]&0x02 != 0 + d.RD = data[2]&0x01 != 0 + d.RA = data[3]&0x80 != 0 + d.Z = uint8(data[3]>>4) & 0x7 + d.ResponseCode = DNSResponseCode(data[3] & 0xF) + d.QDCount = binary.BigEndian.Uint16(data[4:6]) + d.ANCount = binary.BigEndian.Uint16(data[6:8]) + d.NSCount = binary.BigEndian.Uint16(data[8:10]) + d.ARCount = binary.BigEndian.Uint16(data[10:12]) + + d.Questions = d.Questions[:0] + d.Answers = d.Answers[:0] + d.Authorities = d.Authorities[:0] + d.Additionals = d.Additionals[:0] + + offset := 12 + var err error + for i := 0; i < int(d.QDCount); i++ { + var q DNSQuestion + if offset, err = q.decode(data, offset, df, &d.buffer); err != nil { + return err + } + d.Questions = append(d.Questions, q) + } + + // For some horrible reason, if we do the obvious thing in this loop: + // var r DNSResourceRecord + // if blah := r.decode(blah); err != nil { + // return err + // } + // d.Foo = append(d.Foo, r) + // the Go compiler thinks that 'r' escapes to the heap, causing a malloc for + // every Answer, Authority, and Additional. To get around this, we do + // something really silly: we append an empty resource record to our slice, + // then use the last value in the slice to call decode. Since the value is + // already in the slice, there's no WAY it can escape... on the other hand our + // code is MUCH uglier :( + for i := 0; i < int(d.ANCount); i++ { + d.Answers = append(d.Answers, DNSResourceRecord{}) + if offset, err = d.Answers[i].decode(data, offset, df, &d.buffer); err != nil { + d.Answers = d.Answers[:i] // strip off erroneous value + return err + } + } + for i := 0; i < int(d.NSCount); i++ { + d.Authorities = append(d.Authorities, DNSResourceRecord{}) + if offset, err = d.Authorities[i].decode(data, offset, df, &d.buffer); err != nil { + d.Authorities = d.Authorities[:i] // strip off erroneous value + return err + } + } + for i := 0; i < int(d.ARCount); i++ { + d.Additionals = append(d.Additionals, DNSResourceRecord{}) + if offset, err = d.Additionals[i].decode(data, offset, df, &d.buffer); err != nil { + d.Additionals = d.Additionals[:i] // strip off erroneous value + return err + } + } + + if uint16(len(d.Questions)) != d.QDCount { + return errors.New("Invalid query decoding, not the right number of questions") + } else if uint16(len(d.Answers)) != d.ANCount { + return errors.New("Invalid query decoding, not the right number of answers") + } else if uint16(len(d.Authorities)) != d.NSCount { + return errors.New("Invalid query decoding, not the right number of authorities") + } else if uint16(len(d.Additionals)) != d.ARCount { + return errors.New("Invalid query decoding, not the right number of additionals info") + } + return nil +} + +// CanDecode implements gopacket.DecodingLayer. +func (d *DNS) CanDecode() gopacket.LayerClass { + return LayerTypeDNS +} + +// NextLayerType implements gopacket.DecodingLayer. +func (d *DNS) NextLayerType() gopacket.LayerType { + return gopacket.LayerTypePayload +} + +// Payload returns nil. +func (d *DNS) Payload() []byte { + return nil +} + +func b2i(b bool) int { + if b { + return 1 + } + return 0 +} + +func recSize(rr *DNSResourceRecord) int { + switch rr.Type { + case DNSTypeA: + return 4 + case DNSTypeAAAA: + return 16 + case DNSTypeNS: + return len(rr.NS) + 2 + case DNSTypeCNAME: + return len(rr.CNAME) + 2 + case DNSTypePTR: + return len(rr.PTR) + 2 + case DNSTypeSOA: + return len(rr.SOA.MName) + 2 + len(rr.SOA.RName) + 2 + 20 + case DNSTypeMX: + return 2 + len(rr.MX.Name) + 2 + case DNSTypeTXT: + l := len(rr.TXTs) + for _, txt := range rr.TXTs { + l += len(txt) + } + return l + case DNSTypeSRV: + return 6 + len(rr.SRV.Name) + 2 + } + + return 0 +} + +func computeSize(recs []DNSResourceRecord) int { + sz := 0 + for _, rr := range recs { + sz += len(rr.Name) + 14 + sz += recSize(&rr) + } + return sz +} + +// SerializeTo writes the serialized form of this layer into the +// SerializationBuffer, implementing gopacket.SerializableLayer. +func (d *DNS) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error { + dsz := 0 + for _, q := range d.Questions { + dsz += len(q.Name) + 6 + } + dsz += computeSize(d.Answers) + dsz += computeSize(d.Authorities) + dsz += computeSize(d.Additionals) + + bytes, err := b.PrependBytes(12 + dsz) + if err != nil { + return err + } + binary.BigEndian.PutUint16(bytes, d.ID) + bytes[2] = byte((b2i(d.QR) << 7) | (int(d.OpCode) << 3) | (b2i(d.AA) << 2) | (b2i(d.TC) << 1) | b2i(d.RD)) + bytes[3] = byte((b2i(d.RA) << 7) | (int(d.Z) << 4) | int(d.ResponseCode)) + + if opts.FixLengths { + d.QDCount = uint16(len(d.Questions)) + d.ANCount = uint16(len(d.Answers)) + d.NSCount = uint16(len(d.Authorities)) + d.ARCount = uint16(len(d.Additionals)) + } + binary.BigEndian.PutUint16(bytes[4:], d.QDCount) + binary.BigEndian.PutUint16(bytes[6:], d.ANCount) + binary.BigEndian.PutUint16(bytes[8:], d.NSCount) + binary.BigEndian.PutUint16(bytes[10:], d.ARCount) + + off := 12 + for _, qd := range d.Questions { + n := qd.encode(bytes, off) + off += n + } + + for i := range d.Answers { + // done this way so we can modify DNSResourceRecord to fix + // lengths if requested + qa := &d.Answers[i] + n, err := qa.encode(bytes, off, opts) + if err != nil { + return err + } + off += n + } + + for i := range d.Authorities { + qa := &d.Authorities[i] + n, err := qa.encode(bytes, off, opts) + if err != nil { + return err + } + off += n + } + for i := range d.Additionals { + qa := &d.Additionals[i] + n, err := qa.encode(bytes, off, opts) + if err != nil { + return err + } + off += n + } + + return nil +} + +var errMaxRecursion = errors.New("max DNS recursion level hit") + +const maxRecursionLevel = 255 + +func decodeName(data []byte, offset int, buffer *[]byte, level int) ([]byte, int, error) { + if level > maxRecursionLevel { + return nil, 0, errMaxRecursion + } else if offset >= len(data) { + return nil, 0, errors.New("dns name offset too high") + } else if offset < 0 { + return nil, 0, errors.New("dns name offset is negative") + } + start := len(*buffer) + index := offset + if data[index] == 0x00 { + return nil, index + 1, nil + } +loop: + for data[index] != 0x00 { + switch data[index] & 0xc0 { + default: + /* RFC 1035 + A domain name represented as a sequence of labels, where + each label consists of a length octet followed by that + number of octets. The domain name terminates with the + zero length octet for the null label of the root. Note + that this field may be an odd number of octets; no + padding is used. + */ + index2 := index + int(data[index]) + 1 + if index2-offset > 255 { + return nil, 0, errors.New("dns name is too long") + } else if index2 < index+1 || index2 > len(data) { + return nil, 0, errors.New("dns name uncomputable: invalid index") + } + *buffer = append(*buffer, '.') + *buffer = append(*buffer, data[index+1:index2]...) + index = index2 + + case 0xc0: + /* RFC 1035 + The pointer takes the form of a two octet sequence. + + The first two bits are ones. This allows a pointer to + be distinguished from a label, since the label must + begin with two zero bits because labels are restricted + to 63 octets or less. (The 10 and 01 combinations are + reserved for future use.) The OFFSET field specifies + an offset from the start of the message (i.e., the + first octet of the ID field in the domain header). A + zero offset specifies the first byte of the ID field, + etc. + + The compression scheme allows a domain name in a message to be + represented as either: + - a sequence of labels ending in a zero octet + - a pointer + - a sequence of labels ending with a pointer + */ + if index+2 > len(data) { + return nil, 0, errors.New("dns offset pointer too high") + } + offsetp := int(binary.BigEndian.Uint16(data[index:index+2]) & 0x3fff) + if offsetp > len(data) { + return nil, 0, errors.New("dns offset pointer too high") + } + // This looks a little tricky, but actually isn't. Because of how + // decodeName is written, calling it appends the decoded name to the + // current buffer. We already have the start of the buffer, then, so + // once this call is done buffer[start:] will contain our full name. + _, _, err := decodeName(data, offsetp, buffer, level+1) + if err != nil { + return nil, 0, err + } + index++ // pointer is two bytes, so add an extra byte here. + break loop + /* EDNS, or other DNS option ? */ + case 0x40: // RFC 2673 + return nil, 0, fmt.Errorf("qname '0x40' - RFC 2673 unsupported yet (data=%x index=%d)", + data[index], index) + + case 0x80: + return nil, 0, fmt.Errorf("qname '0x80' unsupported yet (data=%x index=%d)", + data[index], index) + } + if index >= len(data) { + return nil, 0, errors.New("dns index walked out of range") + } + } + if len(*buffer) <= start { + return nil, 0, errors.New("no dns data found for name") + } + return (*buffer)[start+1:], index + 1, nil +} + +// DNSQuestion wraps a single request (question) within a DNS query. +type DNSQuestion struct { + Name []byte + Type DNSType + Class DNSClass +} + +func (q *DNSQuestion) decode(data []byte, offset int, df gopacket.DecodeFeedback, buffer *[]byte) (int, error) { + name, endq, err := decodeName(data, offset, buffer, 1) + if err != nil { + return 0, err + } + + q.Name = name + q.Type = DNSType(binary.BigEndian.Uint16(data[endq : endq+2])) + q.Class = DNSClass(binary.BigEndian.Uint16(data[endq+2 : endq+4])) + + return endq + 4, nil +} + +func (q *DNSQuestion) encode(data []byte, offset int) int { + noff := encodeName(q.Name, data, offset) + binary.BigEndian.PutUint16(data[noff:], uint16(q.Type)) + binary.BigEndian.PutUint16(data[noff+2:], uint16(q.Class)) + return len(q.Name) + 6 +} + +// DNSResourceRecord +// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +// | | +// / / +// / NAME / +// | | +// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +// | TYPE | +// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +// | CLASS | +// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +// | TTL | +// | | +// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +// | RDLENGTH | +// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--| +// / RDATA / +// / / +// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ + +// DNSResourceRecord wraps the data from a single DNS resource within a +// response. +type DNSResourceRecord struct { + // Header + Name []byte + Type DNSType + Class DNSClass + TTL uint32 + + // RDATA Raw Values + DataLength uint16 + Data []byte + + // RDATA Decoded Values + IP net.IP + NS, CNAME, PTR []byte + TXTs [][]byte + SOA DNSSOA + SRV DNSSRV + MX DNSMX + + // Undecoded TXT for backward compatibility + TXT []byte +} + +// decode decodes the resource record, returning the total length of the record. +func (rr *DNSResourceRecord) decode(data []byte, offset int, df gopacket.DecodeFeedback, buffer *[]byte) (int, error) { + name, endq, err := decodeName(data, offset, buffer, 1) + if err != nil { + return 0, err + } + + rr.Name = name + rr.Type = DNSType(binary.BigEndian.Uint16(data[endq : endq+2])) + rr.Class = DNSClass(binary.BigEndian.Uint16(data[endq+2 : endq+4])) + rr.TTL = binary.BigEndian.Uint32(data[endq+4 : endq+8]) + rr.DataLength = binary.BigEndian.Uint16(data[endq+8 : endq+10]) + end := endq + 10 + int(rr.DataLength) + if end > len(data) { + return 0, fmt.Errorf("resource record length exceeds data") + } + rr.Data = data[endq+10 : end] + + if err = rr.decodeRData(data, endq+10, buffer); err != nil { + return 0, err + } + + return endq + 10 + int(rr.DataLength), nil +} + +func encodeName(name []byte, data []byte, offset int) int { + l := 0 + for i := range name { + if name[i] == '.' { + data[offset+i-l] = byte(l) + l = 0 + } else { + // skip one to write the length + data[offset+i+1] = name[i] + l++ + } + } + // length for final portion + data[offset+len(name)-l] = byte(l) + data[offset+len(name)+1] = 0x00 // terminal + return offset + len(name) + 2 +} + +func (rr *DNSResourceRecord) encode(data []byte, offset int, opts gopacket.SerializeOptions) (int, error) { + + noff := encodeName(rr.Name, data, offset) + + binary.BigEndian.PutUint16(data[noff:], uint16(rr.Type)) + binary.BigEndian.PutUint16(data[noff+2:], uint16(rr.Class)) + binary.BigEndian.PutUint32(data[noff+4:], uint32(rr.TTL)) + + switch rr.Type { + case DNSTypeA: + copy(data[noff+10:], rr.IP.To4()) + case DNSTypeAAAA: + copy(data[noff+10:], rr.IP) + case DNSTypeNS: + encodeName(rr.NS, data, noff+10) + case DNSTypeCNAME: + encodeName(rr.CNAME, data, noff+10) + case DNSTypePTR: + encodeName(rr.PTR, data, noff+10) + case DNSTypeSOA: + noff2 := encodeName(rr.SOA.MName, data, noff+10) + noff2 = encodeName(rr.SOA.RName, data, noff2) + binary.BigEndian.PutUint32(data[noff2:], rr.SOA.Serial) + binary.BigEndian.PutUint32(data[noff2+4:], rr.SOA.Refresh) + binary.BigEndian.PutUint32(data[noff2+8:], rr.SOA.Retry) + binary.BigEndian.PutUint32(data[noff2+12:], rr.SOA.Expire) + binary.BigEndian.PutUint32(data[noff2+16:], rr.SOA.Minimum) + case DNSTypeMX: + binary.BigEndian.PutUint16(data[noff+10:], rr.MX.Preference) + encodeName(rr.MX.Name, data, noff+12) + case DNSTypeTXT: + noff2 := noff + 10 + for _, txt := range rr.TXTs { + data[noff2] = byte(len(txt)) + copy(data[noff2+1:], txt) + noff2 += 1 + len(txt) + } + case DNSTypeSRV: + binary.BigEndian.PutUint16(data[noff+10:], rr.SRV.Priority) + binary.BigEndian.PutUint16(data[noff+12:], rr.SRV.Weight) + binary.BigEndian.PutUint16(data[noff+14:], rr.SRV.Port) + encodeName(rr.SRV.Name, data, noff+16) + default: + return 0, fmt.Errorf("serializing resource record of type %v not supported", rr.Type) + } + + // DataLength + dSz := recSize(rr) + binary.BigEndian.PutUint16(data[noff+8:], uint16(dSz)) + + if opts.FixLengths { + rr.DataLength = uint16(dSz) + } + + return len(rr.Name) + 1 + 11 + dSz, nil +} + +func (rr *DNSResourceRecord) String() string { + + if rr.Class == DNSClassIN { + switch rr.Type { + case DNSTypeA, DNSTypeAAAA: + return rr.IP.String() + case DNSTypeNS: + return "NS " + string(rr.NS) + case DNSTypeCNAME: + return "CNAME " + string(rr.CNAME) + case DNSTypePTR: + return "PTR " + string(rr.PTR) + case DNSTypeTXT: + return "TXT " + string(rr.TXT) + } + } + + return fmt.Sprintf("<%v, %v>", rr.Class, rr.Type) +} + +func decodeCharacterStrings(data []byte) ([][]byte, error) { + strings := make([][]byte, 0, 1) + end := len(data) + for index, index2 := 0, 0; index != end; index = index2 { + index2 = index + 1 + int(data[index]) // index increases by 1..256 and does not overflow + if index2 > end { + return nil, errors.New("Insufficient data for a <character-string>") + } + strings = append(strings, data[index+1:index2]) + } + return strings, nil +} + +func (rr *DNSResourceRecord) decodeRData(data []byte, offset int, buffer *[]byte) error { + switch rr.Type { + case DNSTypeA: + rr.IP = rr.Data + case DNSTypeAAAA: + rr.IP = rr.Data + case DNSTypeTXT, DNSTypeHINFO: + rr.TXT = rr.Data + txts, err := decodeCharacterStrings(rr.Data) + if err != nil { + return err + } + rr.TXTs = txts + case DNSTypeNS: + name, _, err := decodeName(data, offset, buffer, 1) + if err != nil { + return err + } + rr.NS = name + case DNSTypeCNAME: + name, _, err := decodeName(data, offset, buffer, 1) + if err != nil { + return err + } + rr.CNAME = name + case DNSTypePTR: + name, _, err := decodeName(data, offset, buffer, 1) + if err != nil { + return err + } + rr.PTR = name + case DNSTypeSOA: + name, endq, err := decodeName(data, offset, buffer, 1) + if err != nil { + return err + } + rr.SOA.MName = name + name, endq, err = decodeName(data, endq, buffer, 1) + if err != nil { + return err + } + rr.SOA.RName = name + rr.SOA.Serial = binary.BigEndian.Uint32(data[endq : endq+4]) + rr.SOA.Refresh = binary.BigEndian.Uint32(data[endq+4 : endq+8]) + rr.SOA.Retry = binary.BigEndian.Uint32(data[endq+8 : endq+12]) + rr.SOA.Expire = binary.BigEndian.Uint32(data[endq+12 : endq+16]) + rr.SOA.Minimum = binary.BigEndian.Uint32(data[endq+16 : endq+20]) + case DNSTypeMX: + rr.MX.Preference = binary.BigEndian.Uint16(data[offset : offset+2]) + name, _, err := decodeName(data, offset+2, buffer, 1) + if err != nil { + return err + } + rr.MX.Name = name + case DNSTypeSRV: + rr.SRV.Priority = binary.BigEndian.Uint16(data[offset : offset+2]) + rr.SRV.Weight = binary.BigEndian.Uint16(data[offset+2 : offset+4]) + rr.SRV.Port = binary.BigEndian.Uint16(data[offset+4 : offset+6]) + name, _, err := decodeName(data, offset+6, buffer, 1) + if err != nil { + return err + } + rr.SRV.Name = name + } + return nil +} + +// DNSSOA is a Start of Authority record. Each domain requires a SOA record at +// the cutover where a domain is delegated from its parent. +type DNSSOA struct { + MName, RName []byte + Serial, Refresh, Retry, Expire, Minimum uint32 +} + +// DNSSRV is a Service record, defining a location (hostname/port) of a +// server/service. +type DNSSRV struct { + Priority, Weight, Port uint16 + Name []byte +} + +// DNSMX is a mail exchange record, defining a mail server for a recipient's +// domain. +type DNSMX struct { + Preference uint16 + Name []byte +} |