From e1e8d058a33f7566f9c565d04b0d8b56f9645c35 Mon Sep 17 00:00:00 2001 From: Dimitri Sokolyuk Date: Wed, 25 Apr 2018 09:28:54 +0200 Subject: add vendor --- vendor/golang.org/x/net/dns/dnsmessage/message.go | 2247 +++++++++++++++++++++ 1 file changed, 2247 insertions(+) create mode 100644 vendor/golang.org/x/net/dns/dnsmessage/message.go (limited to 'vendor/golang.org/x/net/dns/dnsmessage/message.go') diff --git a/vendor/golang.org/x/net/dns/dnsmessage/message.go b/vendor/golang.org/x/net/dns/dnsmessage/message.go new file mode 100644 index 0000000..38f8177 --- /dev/null +++ b/vendor/golang.org/x/net/dns/dnsmessage/message.go @@ -0,0 +1,2247 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Package dnsmessage provides a mostly RFC 1035 compliant implementation of +// DNS message packing and unpacking. +// +// The package also supports messages with Extension Mechanisms for DNS +// (EDNS(0)) as defined in RFC 6891. +// +// This implementation is designed to minimize heap allocations and avoid +// unnecessary packing and unpacking as much as possible. +package dnsmessage + +import ( + "errors" +) + +// Message formats + +// A Type is a type of DNS request and response. +type Type uint16 + +// A Class is a type of network. +type Class uint16 + +// An OpCode is a DNS operation code. +type OpCode uint16 + +// An RCode is a DNS response status code. +type RCode uint16 + +// Wire constants. +const ( + // ResourceHeader.Type and Question.Type + TypeA Type = 1 + TypeNS Type = 2 + TypeCNAME Type = 5 + TypeSOA Type = 6 + TypePTR Type = 12 + TypeMX Type = 15 + TypeTXT Type = 16 + TypeAAAA Type = 28 + TypeSRV Type = 33 + TypeOPT Type = 41 + + // Question.Type + TypeWKS Type = 11 + TypeHINFO Type = 13 + TypeMINFO Type = 14 + TypeAXFR Type = 252 + TypeALL Type = 255 + + // ResourceHeader.Class and Question.Class + ClassINET Class = 1 + ClassCSNET Class = 2 + ClassCHAOS Class = 3 + ClassHESIOD Class = 4 + + // Question.Class + ClassANY Class = 255 + + // Message.Rcode + RCodeSuccess RCode = 0 + RCodeFormatError RCode = 1 + RCodeServerFailure RCode = 2 + RCodeNameError RCode = 3 + RCodeNotImplemented RCode = 4 + RCodeRefused RCode = 5 +) + +var ( + // ErrNotStarted indicates that the prerequisite information isn't + // available yet because the previous records haven't been appropriately + // parsed, skipped or finished. + ErrNotStarted = errors.New("parsing/packing of this type isn't available yet") + + // ErrSectionDone indicated that all records in the section have been + // parsed or finished. + ErrSectionDone = errors.New("parsing/packing of this section has completed") + + errBaseLen = errors.New("insufficient data for base length type") + errCalcLen = errors.New("insufficient data for calculated length type") + errReserved = errors.New("segment prefix is reserved") + errTooManyPtr = errors.New("too many pointers (>10)") + errInvalidPtr = errors.New("invalid pointer") + errNilResouceBody = errors.New("nil resource body") + errResourceLen = errors.New("insufficient data for resource body length") + errSegTooLong = errors.New("segment length too long") + errZeroSegLen = errors.New("zero length segment") + errResTooLong = errors.New("resource length too long") + errTooManyQuestions = errors.New("too many Questions to pack (>65535)") + errTooManyAnswers = errors.New("too many Answers to pack (>65535)") + errTooManyAuthorities = errors.New("too many Authorities to pack (>65535)") + errTooManyAdditionals = errors.New("too many Additionals to pack (>65535)") + errNonCanonicalName = errors.New("name is not in canonical format (it must end with a .)") + errStringTooLong = errors.New("character string exceeds maximum length (255)") + errCompressedSRV = errors.New("compressed name in SRV resource data") +) + +// Internal constants. +const ( + // packStartingCap is the default initial buffer size allocated during + // packing. + // + // The starting capacity doesn't matter too much, but most DNS responses + // Will be <= 512 bytes as it is the limit for DNS over UDP. + packStartingCap = 512 + + // uint16Len is the length (in bytes) of a uint16. + uint16Len = 2 + + // uint32Len is the length (in bytes) of a uint32. + uint32Len = 4 + + // headerLen is the length (in bytes) of a DNS header. + // + // A header is comprised of 6 uint16s and no padding. + headerLen = 6 * uint16Len +) + +type nestedError struct { + // s is the current level's error message. + s string + + // err is the nested error. + err error +} + +// nestedError implements error.Error. +func (e *nestedError) Error() string { + return e.s + ": " + e.err.Error() +} + +// Header is a representation of a DNS message header. +type Header struct { + ID uint16 + Response bool + OpCode OpCode + Authoritative bool + Truncated bool + RecursionDesired bool + RecursionAvailable bool + RCode RCode +} + +func (m *Header) pack() (id uint16, bits uint16) { + id = m.ID + bits = uint16(m.OpCode)<<11 | uint16(m.RCode) + if m.RecursionAvailable { + bits |= headerBitRA + } + if m.RecursionDesired { + bits |= headerBitRD + } + if m.Truncated { + bits |= headerBitTC + } + if m.Authoritative { + bits |= headerBitAA + } + if m.Response { + bits |= headerBitQR + } + return +} + +// Message is a representation of a DNS message. +type Message struct { + Header + Questions []Question + Answers []Resource + Authorities []Resource + Additionals []Resource +} + +type section uint8 + +const ( + sectionNotStarted section = iota + sectionHeader + sectionQuestions + sectionAnswers + sectionAuthorities + sectionAdditionals + sectionDone + + headerBitQR = 1 << 15 // query/response (response=1) + headerBitAA = 1 << 10 // authoritative + headerBitTC = 1 << 9 // truncated + headerBitRD = 1 << 8 // recursion desired + headerBitRA = 1 << 7 // recursion available +) + +var sectionNames = map[section]string{ + sectionHeader: "header", + sectionQuestions: "Question", + sectionAnswers: "Answer", + sectionAuthorities: "Authority", + sectionAdditionals: "Additional", +} + +// header is the wire format for a DNS message header. +type header struct { + id uint16 + bits uint16 + questions uint16 + answers uint16 + authorities uint16 + additionals uint16 +} + +func (h *header) count(sec section) uint16 { + switch sec { + case sectionQuestions: + return h.questions + case sectionAnswers: + return h.answers + case sectionAuthorities: + return h.authorities + case sectionAdditionals: + return h.additionals + } + return 0 +} + +// pack appends the wire format of the header to msg. +func (h *header) pack(msg []byte) []byte { + msg = packUint16(msg, h.id) + msg = packUint16(msg, h.bits) + msg = packUint16(msg, h.questions) + msg = packUint16(msg, h.answers) + msg = packUint16(msg, h.authorities) + return packUint16(msg, h.additionals) +} + +func (h *header) unpack(msg []byte, off int) (int, error) { + newOff := off + var err error + if h.id, newOff, err = unpackUint16(msg, newOff); err != nil { + return off, &nestedError{"id", err} + } + if h.bits, newOff, err = unpackUint16(msg, newOff); err != nil { + return off, &nestedError{"bits", err} + } + if h.questions, newOff, err = unpackUint16(msg, newOff); err != nil { + return off, &nestedError{"questions", err} + } + if h.answers, newOff, err = unpackUint16(msg, newOff); err != nil { + return off, &nestedError{"answers", err} + } + if h.authorities, newOff, err = unpackUint16(msg, newOff); err != nil { + return off, &nestedError{"authorities", err} + } + if h.additionals, newOff, err = unpackUint16(msg, newOff); err != nil { + return off, &nestedError{"additionals", err} + } + return newOff, nil +} + +func (h *header) header() Header { + return Header{ + ID: h.id, + Response: (h.bits & headerBitQR) != 0, + OpCode: OpCode(h.bits>>11) & 0xF, + Authoritative: (h.bits & headerBitAA) != 0, + Truncated: (h.bits & headerBitTC) != 0, + RecursionDesired: (h.bits & headerBitRD) != 0, + RecursionAvailable: (h.bits & headerBitRA) != 0, + RCode: RCode(h.bits & 0xF), + } +} + +// A Resource is a DNS resource record. +type Resource struct { + Header ResourceHeader + Body ResourceBody +} + +// A ResourceBody is a DNS resource record minus the header. +type ResourceBody interface { + // pack packs a Resource except for its header. + pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) + + // realType returns the actual type of the Resource. This is used to + // fill in the header Type field. + realType() Type +} + +// pack appends the wire format of the Resource to msg. +func (r *Resource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) { + if r.Body == nil { + return msg, errNilResouceBody + } + oldMsg := msg + r.Header.Type = r.Body.realType() + msg, length, err := r.Header.pack(msg, compression, compressionOff) + if err != nil { + return msg, &nestedError{"ResourceHeader", err} + } + preLen := len(msg) + msg, err = r.Body.pack(msg, compression, compressionOff) + if err != nil { + return msg, &nestedError{"content", err} + } + if err := r.Header.fixLen(msg, length, preLen); err != nil { + return oldMsg, err + } + return msg, nil +} + +// A Parser allows incrementally parsing a DNS message. +// +// When parsing is started, the Header is parsed. Next, each Question can be +// either parsed or skipped. Alternatively, all Questions can be skipped at +// once. When all Questions have been parsed, attempting to parse Questions +// will return (nil, nil) and attempting to skip Questions will return +// (true, nil). After all Questions have been either parsed or skipped, all +// Answers, Authorities and Additionals can be either parsed or skipped in the +// same way, and each type of Resource must be fully parsed or skipped before +// proceeding to the next type of Resource. +// +// Note that there is no requirement to fully skip or parse the message. +type Parser struct { + msg []byte + header header + + section section + off int + index int + resHeaderValid bool + resHeader ResourceHeader +} + +// Start parses the header and enables the parsing of Questions. +func (p *Parser) Start(msg []byte) (Header, error) { + if p.msg != nil { + *p = Parser{} + } + p.msg = msg + var err error + if p.off, err = p.header.unpack(msg, 0); err != nil { + return Header{}, &nestedError{"unpacking header", err} + } + p.section = sectionQuestions + return p.header.header(), nil +} + +func (p *Parser) checkAdvance(sec section) error { + if p.section < sec { + return ErrNotStarted + } + if p.section > sec { + return ErrSectionDone + } + p.resHeaderValid = false + if p.index == int(p.header.count(sec)) { + p.index = 0 + p.section++ + return ErrSectionDone + } + return nil +} + +func (p *Parser) resource(sec section) (Resource, error) { + var r Resource + var err error + r.Header, err = p.resourceHeader(sec) + if err != nil { + return r, err + } + p.resHeaderValid = false + r.Body, p.off, err = unpackResourceBody(p.msg, p.off, r.Header) + if err != nil { + return Resource{}, &nestedError{"unpacking " + sectionNames[sec], err} + } + p.index++ + return r, nil +} + +func (p *Parser) resourceHeader(sec section) (ResourceHeader, error) { + if p.resHeaderValid { + return p.resHeader, nil + } + if err := p.checkAdvance(sec); err != nil { + return ResourceHeader{}, err + } + var hdr ResourceHeader + off, err := hdr.unpack(p.msg, p.off) + if err != nil { + return ResourceHeader{}, err + } + p.resHeaderValid = true + p.resHeader = hdr + p.off = off + return hdr, nil +} + +func (p *Parser) skipResource(sec section) error { + if p.resHeaderValid { + newOff := p.off + int(p.resHeader.Length) + if newOff > len(p.msg) { + return errResourceLen + } + p.off = newOff + p.resHeaderValid = false + p.index++ + return nil + } + if err := p.checkAdvance(sec); err != nil { + return err + } + var err error + p.off, err = skipResource(p.msg, p.off) + if err != nil { + return &nestedError{"skipping: " + sectionNames[sec], err} + } + p.index++ + return nil +} + +// Question parses a single Question. +func (p *Parser) Question() (Question, error) { + if err := p.checkAdvance(sectionQuestions); err != nil { + return Question{}, err + } + var name Name + off, err := name.unpack(p.msg, p.off) + if err != nil { + return Question{}, &nestedError{"unpacking Question.Name", err} + } + typ, off, err := unpackType(p.msg, off) + if err != nil { + return Question{}, &nestedError{"unpacking Question.Type", err} + } + class, off, err := unpackClass(p.msg, off) + if err != nil { + return Question{}, &nestedError{"unpacking Question.Class", err} + } + p.off = off + p.index++ + return Question{name, typ, class}, nil +} + +// AllQuestions parses all Questions. +func (p *Parser) AllQuestions() ([]Question, error) { + // Multiple questions are valid according to the spec, + // but servers don't actually support them. There will + // be at most one question here. + // + // Do not pre-allocate based on info in p.header, since + // the data is untrusted. + qs := []Question{} + for { + q, err := p.Question() + if err == ErrSectionDone { + return qs, nil + } + if err != nil { + return nil, err + } + qs = append(qs, q) + } +} + +// SkipQuestion skips a single Question. +func (p *Parser) SkipQuestion() error { + if err := p.checkAdvance(sectionQuestions); err != nil { + return err + } + off, err := skipName(p.msg, p.off) + if err != nil { + return &nestedError{"skipping Question Name", err} + } + if off, err = skipType(p.msg, off); err != nil { + return &nestedError{"skipping Question Type", err} + } + if off, err = skipClass(p.msg, off); err != nil { + return &nestedError{"skipping Question Class", err} + } + p.off = off + p.index++ + return nil +} + +// SkipAllQuestions skips all Questions. +func (p *Parser) SkipAllQuestions() error { + for { + if err := p.SkipQuestion(); err == ErrSectionDone { + return nil + } else if err != nil { + return err + } + } +} + +// AnswerHeader parses a single Answer ResourceHeader. +func (p *Parser) AnswerHeader() (ResourceHeader, error) { + return p.resourceHeader(sectionAnswers) +} + +// Answer parses a single Answer Resource. +func (p *Parser) Answer() (Resource, error) { + return p.resource(sectionAnswers) +} + +// AllAnswers parses all Answer Resources. +func (p *Parser) AllAnswers() ([]Resource, error) { + // The most common query is for A/AAAA, which usually returns + // a handful of IPs. + // + // Pre-allocate up to a certain limit, since p.header is + // untrusted data. + n := int(p.header.answers) + if n > 20 { + n = 20 + } + as := make([]Resource, 0, n) + for { + a, err := p.Answer() + if err == ErrSectionDone { + return as, nil + } + if err != nil { + return nil, err + } + as = append(as, a) + } +} + +// SkipAnswer skips a single Answer Resource. +func (p *Parser) SkipAnswer() error { + return p.skipResource(sectionAnswers) +} + +// SkipAllAnswers skips all Answer Resources. +func (p *Parser) SkipAllAnswers() error { + for { + if err := p.SkipAnswer(); err == ErrSectionDone { + return nil + } else if err != nil { + return err + } + } +} + +// AuthorityHeader parses a single Authority ResourceHeader. +func (p *Parser) AuthorityHeader() (ResourceHeader, error) { + return p.resourceHeader(sectionAuthorities) +} + +// Authority parses a single Authority Resource. +func (p *Parser) Authority() (Resource, error) { + return p.resource(sectionAuthorities) +} + +// AllAuthorities parses all Authority Resources. +func (p *Parser) AllAuthorities() ([]Resource, error) { + // Authorities contains SOA in case of NXDOMAIN and friends, + // otherwise it is empty. + // + // Pre-allocate up to a certain limit, since p.header is + // untrusted data. + n := int(p.header.authorities) + if n > 10 { + n = 10 + } + as := make([]Resource, 0, n) + for { + a, err := p.Authority() + if err == ErrSectionDone { + return as, nil + } + if err != nil { + return nil, err + } + as = append(as, a) + } +} + +// SkipAuthority skips a single Authority Resource. +func (p *Parser) SkipAuthority() error { + return p.skipResource(sectionAuthorities) +} + +// SkipAllAuthorities skips all Authority Resources. +func (p *Parser) SkipAllAuthorities() error { + for { + if err := p.SkipAuthority(); err == ErrSectionDone { + return nil + } else if err != nil { + return err + } + } +} + +// AdditionalHeader parses a single Additional ResourceHeader. +func (p *Parser) AdditionalHeader() (ResourceHeader, error) { + return p.resourceHeader(sectionAdditionals) +} + +// Additional parses a single Additional Resource. +func (p *Parser) Additional() (Resource, error) { + return p.resource(sectionAdditionals) +} + +// AllAdditionals parses all Additional Resources. +func (p *Parser) AllAdditionals() ([]Resource, error) { + // Additionals usually contain OPT, and sometimes A/AAAA + // glue records. + // + // Pre-allocate up to a certain limit, since p.header is + // untrusted data. + n := int(p.header.additionals) + if n > 10 { + n = 10 + } + as := make([]Resource, 0, n) + for { + a, err := p.Additional() + if err == ErrSectionDone { + return as, nil + } + if err != nil { + return nil, err + } + as = append(as, a) + } +} + +// SkipAdditional skips a single Additional Resource. +func (p *Parser) SkipAdditional() error { + return p.skipResource(sectionAdditionals) +} + +// SkipAllAdditionals skips all Additional Resources. +func (p *Parser) SkipAllAdditionals() error { + for { + if err := p.SkipAdditional(); err == ErrSectionDone { + return nil + } else if err != nil { + return err + } + } +} + +// CNAMEResource parses a single CNAMEResource. +// +// One of the XXXHeader methods must have been called before calling this +// method. +func (p *Parser) CNAMEResource() (CNAMEResource, error) { + if !p.resHeaderValid || p.resHeader.Type != TypeCNAME { + return CNAMEResource{}, ErrNotStarted + } + r, err := unpackCNAMEResource(p.msg, p.off) + if err != nil { + return CNAMEResource{}, err + } + p.off += int(p.resHeader.Length) + p.resHeaderValid = false + p.index++ + return r, nil +} + +// MXResource parses a single MXResource. +// +// One of the XXXHeader methods must have been called before calling this +// method. +func (p *Parser) MXResource() (MXResource, error) { + if !p.resHeaderValid || p.resHeader.Type != TypeMX { + return MXResource{}, ErrNotStarted + } + r, err := unpackMXResource(p.msg, p.off) + if err != nil { + return MXResource{}, err + } + p.off += int(p.resHeader.Length) + p.resHeaderValid = false + p.index++ + return r, nil +} + +// NSResource parses a single NSResource. +// +// One of the XXXHeader methods must have been called before calling this +// method. +func (p *Parser) NSResource() (NSResource, error) { + if !p.resHeaderValid || p.resHeader.Type != TypeNS { + return NSResource{}, ErrNotStarted + } + r, err := unpackNSResource(p.msg, p.off) + if err != nil { + return NSResource{}, err + } + p.off += int(p.resHeader.Length) + p.resHeaderValid = false + p.index++ + return r, nil +} + +// PTRResource parses a single PTRResource. +// +// One of the XXXHeader methods must have been called before calling this +// method. +func (p *Parser) PTRResource() (PTRResource, error) { + if !p.resHeaderValid || p.resHeader.Type != TypePTR { + return PTRResource{}, ErrNotStarted + } + r, err := unpackPTRResource(p.msg, p.off) + if err != nil { + return PTRResource{}, err + } + p.off += int(p.resHeader.Length) + p.resHeaderValid = false + p.index++ + return r, nil +} + +// SOAResource parses a single SOAResource. +// +// One of the XXXHeader methods must have been called before calling this +// method. +func (p *Parser) SOAResource() (SOAResource, error) { + if !p.resHeaderValid || p.resHeader.Type != TypeSOA { + return SOAResource{}, ErrNotStarted + } + r, err := unpackSOAResource(p.msg, p.off) + if err != nil { + return SOAResource{}, err + } + p.off += int(p.resHeader.Length) + p.resHeaderValid = false + p.index++ + return r, nil +} + +// TXTResource parses a single TXTResource. +// +// One of the XXXHeader methods must have been called before calling this +// method. +func (p *Parser) TXTResource() (TXTResource, error) { + if !p.resHeaderValid || p.resHeader.Type != TypeTXT { + return TXTResource{}, ErrNotStarted + } + r, err := unpackTXTResource(p.msg, p.off, p.resHeader.Length) + if err != nil { + return TXTResource{}, err + } + p.off += int(p.resHeader.Length) + p.resHeaderValid = false + p.index++ + return r, nil +} + +// SRVResource parses a single SRVResource. +// +// One of the XXXHeader methods must have been called before calling this +// method. +func (p *Parser) SRVResource() (SRVResource, error) { + if !p.resHeaderValid || p.resHeader.Type != TypeSRV { + return SRVResource{}, ErrNotStarted + } + r, err := unpackSRVResource(p.msg, p.off) + if err != nil { + return SRVResource{}, err + } + p.off += int(p.resHeader.Length) + p.resHeaderValid = false + p.index++ + return r, nil +} + +// AResource parses a single AResource. +// +// One of the XXXHeader methods must have been called before calling this +// method. +func (p *Parser) AResource() (AResource, error) { + if !p.resHeaderValid || p.resHeader.Type != TypeA { + return AResource{}, ErrNotStarted + } + r, err := unpackAResource(p.msg, p.off) + if err != nil { + return AResource{}, err + } + p.off += int(p.resHeader.Length) + p.resHeaderValid = false + p.index++ + return r, nil +} + +// AAAAResource parses a single AAAAResource. +// +// One of the XXXHeader methods must have been called before calling this +// method. +func (p *Parser) AAAAResource() (AAAAResource, error) { + if !p.resHeaderValid || p.resHeader.Type != TypeAAAA { + return AAAAResource{}, ErrNotStarted + } + r, err := unpackAAAAResource(p.msg, p.off) + if err != nil { + return AAAAResource{}, err + } + p.off += int(p.resHeader.Length) + p.resHeaderValid = false + p.index++ + return r, nil +} + +// OPTResource parses a single OPTResource. +// +// One of the XXXHeader methods must have been called before calling this +// method. +func (p *Parser) OPTResource() (OPTResource, error) { + if !p.resHeaderValid || p.resHeader.Type != TypeOPT { + return OPTResource{}, ErrNotStarted + } + r, err := unpackOPTResource(p.msg, p.off, p.resHeader.Length) + if err != nil { + return OPTResource{}, err + } + p.off += int(p.resHeader.Length) + p.resHeaderValid = false + p.index++ + return r, nil +} + +// Unpack parses a full Message. +func (m *Message) Unpack(msg []byte) error { + var p Parser + var err error + if m.Header, err = p.Start(msg); err != nil { + return err + } + if m.Questions, err = p.AllQuestions(); err != nil { + return err + } + if m.Answers, err = p.AllAnswers(); err != nil { + return err + } + if m.Authorities, err = p.AllAuthorities(); err != nil { + return err + } + if m.Additionals, err = p.AllAdditionals(); err != nil { + return err + } + return nil +} + +// Pack packs a full Message. +func (m *Message) Pack() ([]byte, error) { + return m.AppendPack(make([]byte, 0, packStartingCap)) +} + +// AppendPack is like Pack but appends the full Message to b and returns the +// extended buffer. +func (m *Message) AppendPack(b []byte) ([]byte, error) { + // Validate the lengths. It is very unlikely that anyone will try to + // pack more than 65535 of any particular type, but it is possible and + // we should fail gracefully. + if len(m.Questions) > int(^uint16(0)) { + return nil, errTooManyQuestions + } + if len(m.Answers) > int(^uint16(0)) { + return nil, errTooManyAnswers + } + if len(m.Authorities) > int(^uint16(0)) { + return nil, errTooManyAuthorities + } + if len(m.Additionals) > int(^uint16(0)) { + return nil, errTooManyAdditionals + } + + var h header + h.id, h.bits = m.Header.pack() + + h.questions = uint16(len(m.Questions)) + h.answers = uint16(len(m.Answers)) + h.authorities = uint16(len(m.Authorities)) + h.additionals = uint16(len(m.Additionals)) + + compressionOff := len(b) + msg := h.pack(b) + + // RFC 1035 allows (but does not require) compression for packing. RFC + // 1035 requires unpacking implementations to support compression, so + // unconditionally enabling it is fine. + // + // DNS lookups are typically done over UDP, and RFC 1035 states that UDP + // DNS messages can be a maximum of 512 bytes long. Without compression, + // many DNS response messages are over this limit, so enabling + // compression will help ensure compliance. + compression := map[string]int{} + + for i := range m.Questions { + var err error + if msg, err = m.Questions[i].pack(msg, compression, compressionOff); err != nil { + return nil, &nestedError{"packing Question", err} + } + } + for i := range m.Answers { + var err error + if msg, err = m.Answers[i].pack(msg, compression, compressionOff); err != nil { + return nil, &nestedError{"packing Answer", err} + } + } + for i := range m.Authorities { + var err error + if msg, err = m.Authorities[i].pack(msg, compression, compressionOff); err != nil { + return nil, &nestedError{"packing Authority", err} + } + } + for i := range m.Additionals { + var err error + if msg, err = m.Additionals[i].pack(msg, compression, compressionOff); err != nil { + return nil, &nestedError{"packing Additional", err} + } + } + + return msg, nil +} + +// A Builder allows incrementally packing a DNS message. +// +// Example usage: +// buf := make([]byte, 2, 514) +// b := NewBuilder(buf, Header{...}) +// b.EnableCompression() +// // Optionally start a section and add things to that section. +// // Repeat adding sections as necessary. +// buf, err := b.Finish() +// // If err is nil, buf[2:] will contain the built bytes. +type Builder struct { + // msg is the storage for the message being built. + msg []byte + + // section keeps track of the current section being built. + section section + + // header keeps track of what should go in the header when Finish is + // called. + header header + + // start is the starting index of the bytes allocated in msg for header. + start int + + // compression is a mapping from name suffixes to their starting index + // in msg. + compression map[string]int +} + +// NewBuilder creates a new builder with compression disabled. +// +// Note: Most users will want to immediately enable compression with the +// EnableCompression method. See that method's comment for why you may or may +// not want to enable compression. +// +// The DNS message is appended to the provided initial buffer buf (which may be +// nil) as it is built. The final message is returned by the (*Builder).Finish +// method, which may return the same underlying array if there was sufficient +// capacity in the slice. +func NewBuilder(buf []byte, h Header) Builder { + if buf == nil { + buf = make([]byte, 0, packStartingCap) + } + b := Builder{msg: buf, start: len(buf)} + b.header.id, b.header.bits = h.pack() + var hb [headerLen]byte + b.msg = append(b.msg, hb[:]...) + b.section = sectionHeader + return b +} + +// EnableCompression enables compression in the Builder. +// +// Leaving compression disabled avoids compression related allocations, but can +// result in larger message sizes. Be careful with this mode as it can cause +// messages to exceed the UDP size limit. +// +// According to RFC 1035, section 4.1.4, the use of compression is optional, but +// all implementations must accept both compressed and uncompressed DNS +// messages. +// +// Compression should be enabled before any sections are added for best results. +func (b *Builder) EnableCompression() { + b.compression = map[string]int{} +} + +func (b *Builder) startCheck(s section) error { + if b.section <= sectionNotStarted { + return ErrNotStarted + } + if b.section > s { + return ErrSectionDone + } + return nil +} + +// StartQuestions prepares the builder for packing Questions. +func (b *Builder) StartQuestions() error { + if err := b.startCheck(sectionQuestions); err != nil { + return err + } + b.section = sectionQuestions + return nil +} + +// StartAnswers prepares the builder for packing Answers. +func (b *Builder) StartAnswers() error { + if err := b.startCheck(sectionAnswers); err != nil { + return err + } + b.section = sectionAnswers + return nil +} + +// StartAuthorities prepares the builder for packing Authorities. +func (b *Builder) StartAuthorities() error { + if err := b.startCheck(sectionAuthorities); err != nil { + return err + } + b.section = sectionAuthorities + return nil +} + +// StartAdditionals prepares the builder for packing Additionals. +func (b *Builder) StartAdditionals() error { + if err := b.startCheck(sectionAdditionals); err != nil { + return err + } + b.section = sectionAdditionals + return nil +} + +func (b *Builder) incrementSectionCount() error { + var count *uint16 + var err error + switch b.section { + case sectionQuestions: + count = &b.header.questions + err = errTooManyQuestions + case sectionAnswers: + count = &b.header.answers + err = errTooManyAnswers + case sectionAuthorities: + count = &b.header.authorities + err = errTooManyAuthorities + case sectionAdditionals: + count = &b.header.additionals + err = errTooManyAdditionals + } + if *count == ^uint16(0) { + return err + } + *count++ + return nil +} + +// Question adds a single Question. +func (b *Builder) Question(q Question) error { + if b.section < sectionQuestions { + return ErrNotStarted + } + if b.section > sectionQuestions { + return ErrSectionDone + } + msg, err := q.pack(b.msg, b.compression, b.start) + if err != nil { + return err + } + if err := b.incrementSectionCount(); err != nil { + return err + } + b.msg = msg + return nil +} + +func (b *Builder) checkResourceSection() error { + if b.section < sectionAnswers { + return ErrNotStarted + } + if b.section > sectionAdditionals { + return ErrSectionDone + } + return nil +} + +// CNAMEResource adds a single CNAMEResource. +func (b *Builder) CNAMEResource(h ResourceHeader, r CNAMEResource) error { + if err := b.checkResourceSection(); err != nil { + return err + } + h.Type = r.realType() + msg, length, err := h.pack(b.msg, b.compression, b.start) + if err != nil { + return &nestedError{"ResourceHeader", err} + } + preLen := len(msg) + if msg, err = r.pack(msg, b.compression, b.start); err != nil { + return &nestedError{"CNAMEResource body", err} + } + if err := h.fixLen(msg, length, preLen); err != nil { + return err + } + if err := b.incrementSectionCount(); err != nil { + return err + } + b.msg = msg + return nil +} + +// MXResource adds a single MXResource. +func (b *Builder) MXResource(h ResourceHeader, r MXResource) error { + if err := b.checkResourceSection(); err != nil { + return err + } + h.Type = r.realType() + msg, length, err := h.pack(b.msg, b.compression, b.start) + if err != nil { + return &nestedError{"ResourceHeader", err} + } + preLen := len(msg) + if msg, err = r.pack(msg, b.compression, b.start); err != nil { + return &nestedError{"MXResource body", err} + } + if err := h.fixLen(msg, length, preLen); err != nil { + return err + } + if err := b.incrementSectionCount(); err != nil { + return err + } + b.msg = msg + return nil +} + +// NSResource adds a single NSResource. +func (b *Builder) NSResource(h ResourceHeader, r NSResource) error { + if err := b.checkResourceSection(); err != nil { + return err + } + h.Type = r.realType() + msg, length, err := h.pack(b.msg, b.compression, b.start) + if err != nil { + return &nestedError{"ResourceHeader", err} + } + preLen := len(msg) + if msg, err = r.pack(msg, b.compression, b.start); err != nil { + return &nestedError{"NSResource body", err} + } + if err := h.fixLen(msg, length, preLen); err != nil { + return err + } + if err := b.incrementSectionCount(); err != nil { + return err + } + b.msg = msg + return nil +} + +// PTRResource adds a single PTRResource. +func (b *Builder) PTRResource(h ResourceHeader, r PTRResource) error { + if err := b.checkResourceSection(); err != nil { + return err + } + h.Type = r.realType() + msg, length, err := h.pack(b.msg, b.compression, b.start) + if err != nil { + return &nestedError{"ResourceHeader", err} + } + preLen := len(msg) + if msg, err = r.pack(msg, b.compression, b.start); err != nil { + return &nestedError{"PTRResource body", err} + } + if err := h.fixLen(msg, length, preLen); err != nil { + return err + } + if err := b.incrementSectionCount(); err != nil { + return err + } + b.msg = msg + return nil +} + +// SOAResource adds a single SOAResource. +func (b *Builder) SOAResource(h ResourceHeader, r SOAResource) error { + if err := b.checkResourceSection(); err != nil { + return err + } + h.Type = r.realType() + msg, length, err := h.pack(b.msg, b.compression, b.start) + if err != nil { + return &nestedError{"ResourceHeader", err} + } + preLen := len(msg) + if msg, err = r.pack(msg, b.compression, b.start); err != nil { + return &nestedError{"SOAResource body", err} + } + if err := h.fixLen(msg, length, preLen); err != nil { + return err + } + if err := b.incrementSectionCount(); err != nil { + return err + } + b.msg = msg + return nil +} + +// TXTResource adds a single TXTResource. +func (b *Builder) TXTResource(h ResourceHeader, r TXTResource) error { + if err := b.checkResourceSection(); err != nil { + return err + } + h.Type = r.realType() + msg, length, err := h.pack(b.msg, b.compression, b.start) + if err != nil { + return &nestedError{"ResourceHeader", err} + } + preLen := len(msg) + if msg, err = r.pack(msg, b.compression, b.start); err != nil { + return &nestedError{"TXTResource body", err} + } + if err := h.fixLen(msg, length, preLen); err != nil { + return err + } + if err := b.incrementSectionCount(); err != nil { + return err + } + b.msg = msg + return nil +} + +// SRVResource adds a single SRVResource. +func (b *Builder) SRVResource(h ResourceHeader, r SRVResource) error { + if err := b.checkResourceSection(); err != nil { + return err + } + h.Type = r.realType() + msg, length, err := h.pack(b.msg, b.compression, b.start) + if err != nil { + return &nestedError{"ResourceHeader", err} + } + preLen := len(msg) + if msg, err = r.pack(msg, b.compression, b.start); err != nil { + return &nestedError{"SRVResource body", err} + } + if err := h.fixLen(msg, length, preLen); err != nil { + return err + } + if err := b.incrementSectionCount(); err != nil { + return err + } + b.msg = msg + return nil +} + +// AResource adds a single AResource. +func (b *Builder) AResource(h ResourceHeader, r AResource) error { + if err := b.checkResourceSection(); err != nil { + return err + } + h.Type = r.realType() + msg, length, err := h.pack(b.msg, b.compression, b.start) + if err != nil { + return &nestedError{"ResourceHeader", err} + } + preLen := len(msg) + if msg, err = r.pack(msg, b.compression, b.start); err != nil { + return &nestedError{"AResource body", err} + } + if err := h.fixLen(msg, length, preLen); err != nil { + return err + } + if err := b.incrementSectionCount(); err != nil { + return err + } + b.msg = msg + return nil +} + +// AAAAResource adds a single AAAAResource. +func (b *Builder) AAAAResource(h ResourceHeader, r AAAAResource) error { + if err := b.checkResourceSection(); err != nil { + return err + } + h.Type = r.realType() + msg, length, err := h.pack(b.msg, b.compression, b.start) + if err != nil { + return &nestedError{"ResourceHeader", err} + } + preLen := len(msg) + if msg, err = r.pack(msg, b.compression, b.start); err != nil { + return &nestedError{"AAAAResource body", err} + } + if err := h.fixLen(msg, length, preLen); err != nil { + return err + } + if err := b.incrementSectionCount(); err != nil { + return err + } + b.msg = msg + return nil +} + +// OPTResource adds a single OPTResource. +func (b *Builder) OPTResource(h ResourceHeader, r OPTResource) error { + if err := b.checkResourceSection(); err != nil { + return err + } + h.Type = r.realType() + msg, length, err := h.pack(b.msg, b.compression, b.start) + if err != nil { + return &nestedError{"ResourceHeader", err} + } + preLen := len(msg) + if msg, err = r.pack(msg, b.compression, b.start); err != nil { + return &nestedError{"OPTResource body", err} + } + if err := h.fixLen(msg, length, preLen); err != nil { + return err + } + if err := b.incrementSectionCount(); err != nil { + return err + } + b.msg = msg + return nil +} + +// Finish ends message building and generates a binary message. +func (b *Builder) Finish() ([]byte, error) { + if b.section < sectionHeader { + return nil, ErrNotStarted + } + b.section = sectionDone + // Space for the header was allocated in NewBuilder. + b.header.pack(b.msg[b.start:b.start]) + return b.msg, nil +} + +// A ResourceHeader is the header of a DNS resource record. There are +// many types of DNS resource records, but they all share the same header. +type ResourceHeader struct { + // Name is the domain name for which this resource record pertains. + Name Name + + // Type is the type of DNS resource record. + // + // This field will be set automatically during packing. + Type Type + + // Class is the class of network to which this DNS resource record + // pertains. + Class Class + + // TTL is the length of time (measured in seconds) which this resource + // record is valid for (time to live). All Resources in a set should + // have the same TTL (RFC 2181 Section 5.2). + TTL uint32 + + // Length is the length of data in the resource record after the header. + // + // This field will be set automatically during packing. + Length uint16 +} + +// pack appends the wire format of the ResourceHeader to oldMsg. +// +// The bytes where length was packed are returned as a slice so they can be +// updated after the rest of the Resource has been packed. +func (h *ResourceHeader) pack(oldMsg []byte, compression map[string]int, compressionOff int) (msg []byte, length []byte, err error) { + msg = oldMsg + if msg, err = h.Name.pack(msg, compression, compressionOff); err != nil { + return oldMsg, nil, &nestedError{"Name", err} + } + msg = packType(msg, h.Type) + msg = packClass(msg, h.Class) + msg = packUint32(msg, h.TTL) + lenBegin := len(msg) + msg = packUint16(msg, h.Length) + return msg, msg[lenBegin : lenBegin+uint16Len], nil +} + +func (h *ResourceHeader) unpack(msg []byte, off int) (int, error) { + newOff := off + var err error + if newOff, err = h.Name.unpack(msg, newOff); err != nil { + return off, &nestedError{"Name", err} + } + if h.Type, newOff, err = unpackType(msg, newOff); err != nil { + return off, &nestedError{"Type", err} + } + if h.Class, newOff, err = unpackClass(msg, newOff); err != nil { + return off, &nestedError{"Class", err} + } + if h.TTL, newOff, err = unpackUint32(msg, newOff); err != nil { + return off, &nestedError{"TTL", err} + } + if h.Length, newOff, err = unpackUint16(msg, newOff); err != nil { + return off, &nestedError{"Length", err} + } + return newOff, nil +} + +func (h *ResourceHeader) fixLen(msg []byte, length []byte, preLen int) error { + conLen := len(msg) - preLen + if conLen > int(^uint16(0)) { + return errResTooLong + } + + // Fill in the length now that we know how long the content is. + packUint16(length[:0], uint16(conLen)) + h.Length = uint16(conLen) + + return nil +} + +// EDNS(0) wire costants. +const ( + edns0Version = 0 + + edns0DNSSECOK = 0x00008000 + ednsVersionMask = 0x00ff0000 + edns0DNSSECOKMask = 0x00ff8000 +) + +// SetEDNS0 configures h for EDNS(0). +// +// The provided extRCode must be an extedned RCode. +func (h *ResourceHeader) SetEDNS0(udpPayloadLen int, extRCode RCode, dnssecOK bool) error { + h.Name = Name{Data: [nameLen]byte{'.'}, Length: 1} // RFC 6891 section 6.1.2 + h.Type = TypeOPT + h.Class = Class(udpPayloadLen) + h.TTL = uint32(extRCode) >> 4 << 24 + if dnssecOK { + h.TTL |= edns0DNSSECOK + } + return nil +} + +// DNSSECAllowed reports whether the DNSSEC OK bit is set. +func (h *ResourceHeader) DNSSECAllowed() bool { + return h.TTL&edns0DNSSECOKMask == edns0DNSSECOK // RFC 6891 section 6.1.3 +} + +// ExtendedRCode returns an extended RCode. +// +// The provided rcode must be the RCode in DNS message header. +func (h *ResourceHeader) ExtendedRCode(rcode RCode) RCode { + if h.TTL&ednsVersionMask == edns0Version { // RFC 6891 section 6.1.3 + return RCode(h.TTL>>24<<4) | rcode + } + return rcode +} + +func skipResource(msg []byte, off int) (int, error) { + newOff, err := skipName(msg, off) + if err != nil { + return off, &nestedError{"Name", err} + } + if newOff, err = skipType(msg, newOff); err != nil { + return off, &nestedError{"Type", err} + } + if newOff, err = skipClass(msg, newOff); err != nil { + return off, &nestedError{"Class", err} + } + if newOff, err = skipUint32(msg, newOff); err != nil { + return off, &nestedError{"TTL", err} + } + length, newOff, err := unpackUint16(msg, newOff) + if err != nil { + return off, &nestedError{"Length", err} + } + if newOff += int(length); newOff > len(msg) { + return off, errResourceLen + } + return newOff, nil +} + +// packUint16 appends the wire format of field to msg. +func packUint16(msg []byte, field uint16) []byte { + return append(msg, byte(field>>8), byte(field)) +} + +func unpackUint16(msg []byte, off int) (uint16, int, error) { + if off+uint16Len > len(msg) { + return 0, off, errBaseLen + } + return uint16(msg[off])<<8 | uint16(msg[off+1]), off + uint16Len, nil +} + +func skipUint16(msg []byte, off int) (int, error) { + if off+uint16Len > len(msg) { + return off, errBaseLen + } + return off + uint16Len, nil +} + +// packType appends the wire format of field to msg. +func packType(msg []byte, field Type) []byte { + return packUint16(msg, uint16(field)) +} + +func unpackType(msg []byte, off int) (Type, int, error) { + t, o, err := unpackUint16(msg, off) + return Type(t), o, err +} + +func skipType(msg []byte, off int) (int, error) { + return skipUint16(msg, off) +} + +// packClass appends the wire format of field to msg. +func packClass(msg []byte, field Class) []byte { + return packUint16(msg, uint16(field)) +} + +func unpackClass(msg []byte, off int) (Class, int, error) { + c, o, err := unpackUint16(msg, off) + return Class(c), o, err +} + +func skipClass(msg []byte, off int) (int, error) { + return skipUint16(msg, off) +} + +// packUint32 appends the wire format of field to msg. +func packUint32(msg []byte, field uint32) []byte { + return append( + msg, + byte(field>>24), + byte(field>>16), + byte(field>>8), + byte(field), + ) +} + +func unpackUint32(msg []byte, off int) (uint32, int, error) { + if off+uint32Len > len(msg) { + return 0, off, errBaseLen + } + v := uint32(msg[off])<<24 | uint32(msg[off+1])<<16 | uint32(msg[off+2])<<8 | uint32(msg[off+3]) + return v, off + uint32Len, nil +} + +func skipUint32(msg []byte, off int) (int, error) { + if off+uint32Len > len(msg) { + return off, errBaseLen + } + return off + uint32Len, nil +} + +// packText appends the wire format of field to msg. +func packText(msg []byte, field string) ([]byte, error) { + l := len(field) + if l > 255 { + return nil, errStringTooLong + } + msg = append(msg, byte(l)) + msg = append(msg, field...) + + return msg, nil +} + +func unpackText(msg []byte, off int) (string, int, error) { + if off >= len(msg) { + return "", off, errBaseLen + } + beginOff := off + 1 + endOff := beginOff + int(msg[off]) + if endOff > len(msg) { + return "", off, errCalcLen + } + return string(msg[beginOff:endOff]), endOff, nil +} + +func skipText(msg []byte, off int) (int, error) { + if off >= len(msg) { + return off, errBaseLen + } + endOff := off + 1 + int(msg[off]) + if endOff > len(msg) { + return off, errCalcLen + } + return endOff, nil +} + +// packBytes appends the wire format of field to msg. +func packBytes(msg []byte, field []byte) []byte { + return append(msg, field...) +} + +func unpackBytes(msg []byte, off int, field []byte) (int, error) { + newOff := off + len(field) + if newOff > len(msg) { + return off, errBaseLen + } + copy(field, msg[off:newOff]) + return newOff, nil +} + +func skipBytes(msg []byte, off int, field []byte) (int, error) { + newOff := off + len(field) + if newOff > len(msg) { + return off, errBaseLen + } + return newOff, nil +} + +const nameLen = 255 + +// A Name is a non-encoded domain name. It is used instead of strings to avoid +// allocations. +type Name struct { + Data [nameLen]byte + Length uint8 +} + +// NewName creates a new Name from a string. +func NewName(name string) (Name, error) { + if len([]byte(name)) > nameLen { + return Name{}, errCalcLen + } + n := Name{Length: uint8(len(name))} + copy(n.Data[:], []byte(name)) + return n, nil +} + +func (n Name) String() string { + return string(n.Data[:n.Length]) +} + +// pack appends the wire format of the Name to msg. +// +// Domain names are a sequence of counted strings split at the dots. They end +// with a zero-length string. Compression can be used to reuse domain suffixes. +// +// The compression map will be updated with new domain suffixes. If compression +// is nil, compression will not be used. +func (n *Name) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) { + oldMsg := msg + + // Add a trailing dot to canonicalize name. + if n.Length == 0 || n.Data[n.Length-1] != '.' { + return oldMsg, errNonCanonicalName + } + + // Allow root domain. + if n.Data[0] == '.' && n.Length == 1 { + return append(msg, 0), nil + } + + // Emit sequence of counted strings, chopping at dots. + for i, begin := 0, 0; i < int(n.Length); i++ { + // Check for the end of the segment. + if n.Data[i] == '.' { + // The two most significant bits have special meaning. + // It isn't allowed for segments to be long enough to + // need them. + if i-begin >= 1<<6 { + return oldMsg, errSegTooLong + } + + // Segments must have a non-zero length. + if i-begin == 0 { + return oldMsg, errZeroSegLen + } + + msg = append(msg, byte(i-begin)) + + for j := begin; j < i; j++ { + msg = append(msg, n.Data[j]) + } + + begin = i + 1 + continue + } + + // We can only compress domain suffixes starting with a new + // segment. A pointer is two bytes with the two most significant + // bits set to 1 to indicate that it is a pointer. + if (i == 0 || n.Data[i-1] == '.') && compression != nil { + if ptr, ok := compression[string(n.Data[i:])]; ok { + // Hit. Emit a pointer instead of the rest of + // the domain. + return append(msg, byte(ptr>>8|0xC0), byte(ptr)), nil + } + + // Miss. Add the suffix to the compression table if the + // offset can be stored in the available 14 bytes. + if len(msg) <= int(^uint16(0)>>2) { + compression[string(n.Data[i:])] = len(msg) - compressionOff + } + } + } + return append(msg, 0), nil +} + +// unpack unpacks a domain name. +func (n *Name) unpack(msg []byte, off int) (int, error) { + return n.unpackCompressed(msg, off, true /* allowCompression */) +} + +func (n *Name) unpackCompressed(msg []byte, off int, allowCompression bool) (int, error) { + // currOff is the current working offset. + currOff := off + + // newOff is the offset where the next record will start. Pointers lead + // to data that belongs to other names and thus doesn't count towards to + // the usage of this name. + newOff := off + + // ptr is the number of pointers followed. + var ptr int + + // Name is a slice representation of the name data. + name := n.Data[:0] + +Loop: + for { + if currOff >= len(msg) { + return off, errBaseLen + } + c := int(msg[currOff]) + currOff++ + switch c & 0xC0 { + case 0x00: // String segment + if c == 0x00 { + // A zero length signals the end of the name. + break Loop + } + endOff := currOff + c + if endOff > len(msg) { + return off, errCalcLen + } + name = append(name, msg[currOff:endOff]...) + name = append(name, '.') + currOff = endOff + case 0xC0: // Pointer + if !allowCompression { + return off, errCompressedSRV + } + if currOff >= len(msg) { + return off, errInvalidPtr + } + c1 := msg[currOff] + currOff++ + if ptr == 0 { + newOff = currOff + } + // Don't follow too many pointers, maybe there's a loop. + if ptr++; ptr > 10 { + return off, errTooManyPtr + } + currOff = (c^0xC0)<<8 | int(c1) + default: + // Prefixes 0x80 and 0x40 are reserved. + return off, errReserved + } + } + if len(name) == 0 { + name = append(name, '.') + } + if len(name) > len(n.Data) { + return off, errCalcLen + } + n.Length = uint8(len(name)) + if ptr == 0 { + newOff = currOff + } + return newOff, nil +} + +func skipName(msg []byte, off int) (int, error) { + // newOff is the offset where the next record will start. Pointers lead + // to data that belongs to other names and thus doesn't count towards to + // the usage of this name. + newOff := off + +Loop: + for { + if newOff >= len(msg) { + return off, errBaseLen + } + c := int(msg[newOff]) + newOff++ + switch c & 0xC0 { + case 0x00: + if c == 0x00 { + // A zero length signals the end of the name. + break Loop + } + // literal string + newOff += c + if newOff > len(msg) { + return off, errCalcLen + } + case 0xC0: + // Pointer to somewhere else in msg. + + // Pointers are two bytes. + newOff++ + + // Don't follow the pointer as the data here has ended. + break Loop + default: + // Prefixes 0x80 and 0x40 are reserved. + return off, errReserved + } + } + + return newOff, nil +} + +// A Question is a DNS query. +type Question struct { + Name Name + Type Type + Class Class +} + +// pack appends the wire format of the Question to msg. +func (q *Question) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) { + msg, err := q.Name.pack(msg, compression, compressionOff) + if err != nil { + return msg, &nestedError{"Name", err} + } + msg = packType(msg, q.Type) + return packClass(msg, q.Class), nil +} + +func unpackResourceBody(msg []byte, off int, hdr ResourceHeader) (ResourceBody, int, error) { + var ( + r ResourceBody + err error + name string + ) + switch hdr.Type { + case TypeA: + var rb AResource + rb, err = unpackAResource(msg, off) + r = &rb + name = "A" + case TypeNS: + var rb NSResource + rb, err = unpackNSResource(msg, off) + r = &rb + name = "NS" + case TypeCNAME: + var rb CNAMEResource + rb, err = unpackCNAMEResource(msg, off) + r = &rb + name = "CNAME" + case TypeSOA: + var rb SOAResource + rb, err = unpackSOAResource(msg, off) + r = &rb + name = "SOA" + case TypePTR: + var rb PTRResource + rb, err = unpackPTRResource(msg, off) + r = &rb + name = "PTR" + case TypeMX: + var rb MXResource + rb, err = unpackMXResource(msg, off) + r = &rb + name = "MX" + case TypeTXT: + var rb TXTResource + rb, err = unpackTXTResource(msg, off, hdr.Length) + r = &rb + name = "TXT" + case TypeAAAA: + var rb AAAAResource + rb, err = unpackAAAAResource(msg, off) + r = &rb + name = "AAAA" + case TypeSRV: + var rb SRVResource + rb, err = unpackSRVResource(msg, off) + r = &rb + name = "SRV" + case TypeOPT: + var rb OPTResource + rb, err = unpackOPTResource(msg, off, hdr.Length) + r = &rb + name = "OPT" + } + if err != nil { + return nil, off, &nestedError{name + " record", err} + } + if r == nil { + return nil, off, errors.New("invalid resource type: " + string(hdr.Type+'0')) + } + return r, off + int(hdr.Length), nil +} + +// A CNAMEResource is a CNAME Resource record. +type CNAMEResource struct { + CNAME Name +} + +func (r *CNAMEResource) realType() Type { + return TypeCNAME +} + +// pack appends the wire format of the CNAMEResource to msg. +func (r *CNAMEResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) { + return r.CNAME.pack(msg, compression, compressionOff) +} + +func unpackCNAMEResource(msg []byte, off int) (CNAMEResource, error) { + var cname Name + if _, err := cname.unpack(msg, off); err != nil { + return CNAMEResource{}, err + } + return CNAMEResource{cname}, nil +} + +// An MXResource is an MX Resource record. +type MXResource struct { + Pref uint16 + MX Name +} + +func (r *MXResource) realType() Type { + return TypeMX +} + +// pack appends the wire format of the MXResource to msg. +func (r *MXResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) { + oldMsg := msg + msg = packUint16(msg, r.Pref) + msg, err := r.MX.pack(msg, compression, compressionOff) + if err != nil { + return oldMsg, &nestedError{"MXResource.MX", err} + } + return msg, nil +} + +func unpackMXResource(msg []byte, off int) (MXResource, error) { + pref, off, err := unpackUint16(msg, off) + if err != nil { + return MXResource{}, &nestedError{"Pref", err} + } + var mx Name + if _, err := mx.unpack(msg, off); err != nil { + return MXResource{}, &nestedError{"MX", err} + } + return MXResource{pref, mx}, nil +} + +// An NSResource is an NS Resource record. +type NSResource struct { + NS Name +} + +func (r *NSResource) realType() Type { + return TypeNS +} + +// pack appends the wire format of the NSResource to msg. +func (r *NSResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) { + return r.NS.pack(msg, compression, compressionOff) +} + +func unpackNSResource(msg []byte, off int) (NSResource, error) { + var ns Name + if _, err := ns.unpack(msg, off); err != nil { + return NSResource{}, err + } + return NSResource{ns}, nil +} + +// A PTRResource is a PTR Resource record. +type PTRResource struct { + PTR Name +} + +func (r *PTRResource) realType() Type { + return TypePTR +} + +// pack appends the wire format of the PTRResource to msg. +func (r *PTRResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) { + return r.PTR.pack(msg, compression, compressionOff) +} + +func unpackPTRResource(msg []byte, off int) (PTRResource, error) { + var ptr Name + if _, err := ptr.unpack(msg, off); err != nil { + return PTRResource{}, err + } + return PTRResource{ptr}, nil +} + +// An SOAResource is an SOA Resource record. +type SOAResource struct { + NS Name + MBox Name + Serial uint32 + Refresh uint32 + Retry uint32 + Expire uint32 + + // MinTTL the is the default TTL of Resources records which did not + // contain a TTL value and the TTL of negative responses. (RFC 2308 + // Section 4) + MinTTL uint32 +} + +func (r *SOAResource) realType() Type { + return TypeSOA +} + +// pack appends the wire format of the SOAResource to msg. +func (r *SOAResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) { + oldMsg := msg + msg, err := r.NS.pack(msg, compression, compressionOff) + if err != nil { + return oldMsg, &nestedError{"SOAResource.NS", err} + } + msg, err = r.MBox.pack(msg, compression, compressionOff) + if err != nil { + return oldMsg, &nestedError{"SOAResource.MBox", err} + } + msg = packUint32(msg, r.Serial) + msg = packUint32(msg, r.Refresh) + msg = packUint32(msg, r.Retry) + msg = packUint32(msg, r.Expire) + return packUint32(msg, r.MinTTL), nil +} + +func unpackSOAResource(msg []byte, off int) (SOAResource, error) { + var ns Name + off, err := ns.unpack(msg, off) + if err != nil { + return SOAResource{}, &nestedError{"NS", err} + } + var mbox Name + if off, err = mbox.unpack(msg, off); err != nil { + return SOAResource{}, &nestedError{"MBox", err} + } + serial, off, err := unpackUint32(msg, off) + if err != nil { + return SOAResource{}, &nestedError{"Serial", err} + } + refresh, off, err := unpackUint32(msg, off) + if err != nil { + return SOAResource{}, &nestedError{"Refresh", err} + } + retry, off, err := unpackUint32(msg, off) + if err != nil { + return SOAResource{}, &nestedError{"Retry", err} + } + expire, off, err := unpackUint32(msg, off) + if err != nil { + return SOAResource{}, &nestedError{"Expire", err} + } + minTTL, _, err := unpackUint32(msg, off) + if err != nil { + return SOAResource{}, &nestedError{"MinTTL", err} + } + return SOAResource{ns, mbox, serial, refresh, retry, expire, minTTL}, nil +} + +// A TXTResource is a TXT Resource record. +type TXTResource struct { + TXT []string +} + +func (r *TXTResource) realType() Type { + return TypeTXT +} + +// pack appends the wire format of the TXTResource to msg. +func (r *TXTResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) { + oldMsg := msg + for _, s := range r.TXT { + var err error + msg, err = packText(msg, s) + if err != nil { + return oldMsg, err + } + } + return msg, nil +} + +func unpackTXTResource(msg []byte, off int, length uint16) (TXTResource, error) { + txts := make([]string, 0, 1) + for n := uint16(0); n < length; { + var t string + var err error + if t, off, err = unpackText(msg, off); err != nil { + return TXTResource{}, &nestedError{"text", err} + } + // Check if we got too many bytes. + if length-n < uint16(len(t))+1 { + return TXTResource{}, errCalcLen + } + n += uint16(len(t)) + 1 + txts = append(txts, t) + } + return TXTResource{txts}, nil +} + +// An SRVResource is an SRV Resource record. +type SRVResource struct { + Priority uint16 + Weight uint16 + Port uint16 + Target Name // Not compressed as per RFC 2782. +} + +func (r *SRVResource) realType() Type { + return TypeSRV +} + +// pack appends the wire format of the SRVResource to msg. +func (r *SRVResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) { + oldMsg := msg + msg = packUint16(msg, r.Priority) + msg = packUint16(msg, r.Weight) + msg = packUint16(msg, r.Port) + msg, err := r.Target.pack(msg, nil, compressionOff) + if err != nil { + return oldMsg, &nestedError{"SRVResource.Target", err} + } + return msg, nil +} + +func unpackSRVResource(msg []byte, off int) (SRVResource, error) { + priority, off, err := unpackUint16(msg, off) + if err != nil { + return SRVResource{}, &nestedError{"Priority", err} + } + weight, off, err := unpackUint16(msg, off) + if err != nil { + return SRVResource{}, &nestedError{"Weight", err} + } + port, off, err := unpackUint16(msg, off) + if err != nil { + return SRVResource{}, &nestedError{"Port", err} + } + var target Name + if _, err := target.unpackCompressed(msg, off, false /* allowCompression */); err != nil { + return SRVResource{}, &nestedError{"Target", err} + } + return SRVResource{priority, weight, port, target}, nil +} + +// An AResource is an A Resource record. +type AResource struct { + A [4]byte +} + +func (r *AResource) realType() Type { + return TypeA +} + +// pack appends the wire format of the AResource to msg. +func (r *AResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) { + return packBytes(msg, r.A[:]), nil +} + +func unpackAResource(msg []byte, off int) (AResource, error) { + var a [4]byte + if _, err := unpackBytes(msg, off, a[:]); err != nil { + return AResource{}, err + } + return AResource{a}, nil +} + +// An AAAAResource is an AAAA Resource record. +type AAAAResource struct { + AAAA [16]byte +} + +func (r *AAAAResource) realType() Type { + return TypeAAAA +} + +// pack appends the wire format of the AAAAResource to msg. +func (r *AAAAResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) { + return packBytes(msg, r.AAAA[:]), nil +} + +func unpackAAAAResource(msg []byte, off int) (AAAAResource, error) { + var aaaa [16]byte + if _, err := unpackBytes(msg, off, aaaa[:]); err != nil { + return AAAAResource{}, err + } + return AAAAResource{aaaa}, nil +} + +// An OPTResource is an OPT pseudo Resource record. +// +// The pseudo resource record is part of the extension mechanisms for DNS +// as defined in RFC 6891. +type OPTResource struct { + Options []Option +} + +// An Option represents a DNS message option within OPTResource. +// +// The message option is part of the extension mechanisms for DNS as +// defined in RFC 6891. +type Option struct { + Code uint16 // option code + Data []byte +} + +func (r *OPTResource) realType() Type { + return TypeOPT +} + +func (r *OPTResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) { + for _, opt := range r.Options { + msg = packUint16(msg, opt.Code) + l := uint16(len(opt.Data)) + msg = packUint16(msg, l) + msg = packBytes(msg, opt.Data) + } + return msg, nil +} + +func unpackOPTResource(msg []byte, off int, length uint16) (OPTResource, error) { + var opts []Option + for oldOff := off; off < oldOff+int(length); { + var err error + var o Option + o.Code, off, err = unpackUint16(msg, off) + if err != nil { + return OPTResource{}, &nestedError{"Code", err} + } + var l uint16 + l, off, err = unpackUint16(msg, off) + if err != nil { + return OPTResource{}, &nestedError{"Data", err} + } + o.Data = make([]byte, l) + if copy(o.Data, msg[off:]) != int(l) { + return OPTResource{}, &nestedError{"Data", errCalcLen} + } + off += int(l) + opts = append(opts, o) + } + return OPTResource{opts}, nil +} -- cgit v1.2.3