1package dns 2 3import ( 4 "errors" 5 "net" 6 "strconv" 7) 8 9const hexDigit = "0123456789abcdef" 10 11// Everything is assumed in ClassINET. 12 13// SetReply creates a reply message from a request message. 14func (dns *Msg) SetReply(request *Msg) *Msg { 15 dns.Id = request.Id 16 dns.RecursionDesired = request.RecursionDesired // Copy rd bit 17 dns.Response = true 18 dns.Opcode = OpcodeQuery 19 dns.Rcode = RcodeSuccess 20 if len(request.Question) > 0 { 21 dns.Question = make([]Question, 1) 22 dns.Question[0] = request.Question[0] 23 } 24 return dns 25} 26 27// SetQuestion creates a question message, it sets the Question 28// section, generates an Id and sets the RecursionDesired (RD) 29// bit to true. 30func (dns *Msg) SetQuestion(z string, t uint16) *Msg { 31 dns.Id = Id() 32 dns.RecursionDesired = true 33 dns.Question = make([]Question, 1) 34 dns.Question[0] = Question{z, t, ClassINET} 35 return dns 36} 37 38// SetNotify creates a notify message, it sets the Question 39// section, generates an Id and sets the Authoritative (AA) 40// bit to true. 41func (dns *Msg) SetNotify(z string) *Msg { 42 dns.Opcode = OpcodeNotify 43 dns.Authoritative = true 44 dns.Id = Id() 45 dns.Question = make([]Question, 1) 46 dns.Question[0] = Question{z, TypeSOA, ClassINET} 47 return dns 48} 49 50// SetRcode creates an error message suitable for the request. 51func (dns *Msg) SetRcode(request *Msg, rcode int) *Msg { 52 dns.SetReply(request) 53 dns.Rcode = rcode 54 return dns 55} 56 57// SetRcodeFormatError creates a message with FormError set. 58func (dns *Msg) SetRcodeFormatError(request *Msg) *Msg { 59 dns.Rcode = RcodeFormatError 60 dns.Opcode = OpcodeQuery 61 dns.Response = true 62 dns.Authoritative = false 63 dns.Id = request.Id 64 return dns 65} 66 67// SetUpdate makes the message a dynamic update message. It 68// sets the ZONE section to: z, TypeSOA, ClassINET. 69func (dns *Msg) SetUpdate(z string) *Msg { 70 dns.Id = Id() 71 dns.Response = false 72 dns.Opcode = OpcodeUpdate 73 dns.Compress = false // BIND9 cannot handle compression 74 dns.Question = make([]Question, 1) 75 dns.Question[0] = Question{z, TypeSOA, ClassINET} 76 return dns 77} 78 79// SetIxfr creates message for requesting an IXFR. 80func (dns *Msg) SetIxfr(z string, serial uint32, ns, mbox string) *Msg { 81 dns.Id = Id() 82 dns.Question = make([]Question, 1) 83 dns.Ns = make([]RR, 1) 84 s := new(SOA) 85 s.Hdr = RR_Header{z, TypeSOA, ClassINET, defaultTtl, 0} 86 s.Serial = serial 87 s.Ns = ns 88 s.Mbox = mbox 89 dns.Question[0] = Question{z, TypeIXFR, ClassINET} 90 dns.Ns[0] = s 91 return dns 92} 93 94// SetAxfr creates message for requesting an AXFR. 95func (dns *Msg) SetAxfr(z string) *Msg { 96 dns.Id = Id() 97 dns.Question = make([]Question, 1) 98 dns.Question[0] = Question{z, TypeAXFR, ClassINET} 99 return dns 100} 101 102// SetTsig appends a TSIG RR to the message. 103// This is only a skeleton TSIG RR that is added as the last RR in the 104// additional section. The Tsig is calculated when the message is being send. 105func (dns *Msg) SetTsig(z, algo string, fudge, timesigned int64) *Msg { 106 t := new(TSIG) 107 t.Hdr = RR_Header{z, TypeTSIG, ClassANY, 0, 0} 108 t.Algorithm = algo 109 t.Fudge = 300 110 t.TimeSigned = uint64(timesigned) 111 t.OrigId = dns.Id 112 dns.Extra = append(dns.Extra, t) 113 return dns 114} 115 116// SetEdns0 appends a EDNS0 OPT RR to the message. 117// TSIG should always the last RR in a message. 118func (dns *Msg) SetEdns0(udpsize uint16, do bool) *Msg { 119 e := new(OPT) 120 e.Hdr.Name = "." 121 e.Hdr.Rrtype = TypeOPT 122 e.SetUDPSize(udpsize) 123 if do { 124 e.SetDo() 125 } 126 dns.Extra = append(dns.Extra, e) 127 return dns 128} 129 130// IsTsig checks if the message has a TSIG record as the last record 131// in the additional section. It returns the TSIG record found or nil. 132func (dns *Msg) IsTsig() *TSIG { 133 if len(dns.Extra) > 0 { 134 if dns.Extra[len(dns.Extra)-1].Header().Rrtype == TypeTSIG { 135 return dns.Extra[len(dns.Extra)-1].(*TSIG) 136 } 137 } 138 return nil 139} 140 141// IsEdns0 checks if the message has a EDNS0 (OPT) record, any EDNS0 142// record in the additional section will do. It returns the OPT record 143// found or nil. 144func (dns *Msg) IsEdns0() *OPT { 145 // EDNS0 is at the end of the additional section, start there. 146 // We might want to change this to *only* look at the last two 147 // records. So we see TSIG and/or OPT - this a slightly bigger 148 // change though. 149 for i := len(dns.Extra) - 1; i >= 0; i-- { 150 if dns.Extra[i].Header().Rrtype == TypeOPT { 151 return dns.Extra[i].(*OPT) 152 } 153 } 154 return nil 155} 156 157// IsDomainName checks if s is a valid domain name, it returns the number of 158// labels and true, when a domain name is valid. Note that non fully qualified 159// domain name is considered valid, in this case the last label is counted in 160// the number of labels. When false is returned the number of labels is not 161// defined. Also note that this function is extremely liberal; almost any 162// string is a valid domain name as the DNS is 8 bit protocol. It checks if each 163// label fits in 63 characters, but there is no length check for the entire 164// string s. I.e. a domain name longer than 255 characters is considered valid. 165func IsDomainName(s string) (labels int, ok bool) { 166 _, labels, err := packDomainName(s, nil, 0, nil, false) 167 return labels, err == nil 168} 169 170// IsSubDomain checks if child is indeed a child of the parent. If child and parent 171// are the same domain true is returned as well. 172func IsSubDomain(parent, child string) bool { 173 // Entire child is contained in parent 174 return CompareDomainName(parent, child) == CountLabel(parent) 175} 176 177// IsMsg sanity checks buf and returns an error if it isn't a valid DNS packet. 178// The checking is performed on the binary payload. 179func IsMsg(buf []byte) error { 180 // Header 181 if len(buf) < 12 { 182 return errors.New("dns: bad message header") 183 } 184 // Header: Opcode 185 // TODO(miek): more checks here, e.g. check all header bits. 186 return nil 187} 188 189// IsFqdn checks if a domain name is fully qualified. 190func IsFqdn(s string) bool { 191 l := len(s) 192 if l == 0 { 193 return false 194 } 195 return s[l-1] == '.' 196} 197 198// IsRRset checks if a set of RRs is a valid RRset as defined by RFC 2181. 199// This means the RRs need to have the same type, name, and class. Returns true 200// if the RR set is valid, otherwise false. 201func IsRRset(rrset []RR) bool { 202 if len(rrset) == 0 { 203 return false 204 } 205 if len(rrset) == 1 { 206 return true 207 } 208 rrHeader := rrset[0].Header() 209 rrType := rrHeader.Rrtype 210 rrClass := rrHeader.Class 211 rrName := rrHeader.Name 212 213 for _, rr := range rrset[1:] { 214 curRRHeader := rr.Header() 215 if curRRHeader.Rrtype != rrType || curRRHeader.Class != rrClass || curRRHeader.Name != rrName { 216 // Mismatch between the records, so this is not a valid rrset for 217 //signing/verifying 218 return false 219 } 220 } 221 222 return true 223} 224 225// Fqdn return the fully qualified domain name from s. 226// If s is already fully qualified, it behaves as the identity function. 227func Fqdn(s string) string { 228 if IsFqdn(s) { 229 return s 230 } 231 return s + "." 232} 233 234// Copied from the official Go code. 235 236// ReverseAddr returns the in-addr.arpa. or ip6.arpa. hostname of the IP 237// address suitable for reverse DNS (PTR) record lookups or an error if it fails 238// to parse the IP address. 239func ReverseAddr(addr string) (arpa string, err error) { 240 ip := net.ParseIP(addr) 241 if ip == nil { 242 return "", &Error{err: "unrecognized address: " + addr} 243 } 244 if ip.To4() != nil { 245 return strconv.Itoa(int(ip[15])) + "." + strconv.Itoa(int(ip[14])) + "." + strconv.Itoa(int(ip[13])) + "." + 246 strconv.Itoa(int(ip[12])) + ".in-addr.arpa.", nil 247 } 248 // Must be IPv6 249 buf := make([]byte, 0, len(ip)*4+len("ip6.arpa.")) 250 // Add it, in reverse, to the buffer 251 for i := len(ip) - 1; i >= 0; i-- { 252 v := ip[i] 253 buf = append(buf, hexDigit[v&0xF]) 254 buf = append(buf, '.') 255 buf = append(buf, hexDigit[v>>4]) 256 buf = append(buf, '.') 257 } 258 // Append "ip6.arpa." and return (buf already has the final .) 259 buf = append(buf, "ip6.arpa."...) 260 return string(buf), nil 261} 262 263// String returns the string representation for the type t. 264func (t Type) String() string { 265 if t1, ok := TypeToString[uint16(t)]; ok { 266 return t1 267 } 268 return "TYPE" + strconv.Itoa(int(t)) 269} 270 271// String returns the string representation for the class c. 272func (c Class) String() string { 273 if c1, ok := ClassToString[uint16(c)]; ok { 274 return c1 275 } 276 return "CLASS" + strconv.Itoa(int(c)) 277} 278 279// String returns the string representation for the name n. 280func (n Name) String() string { 281 return sprintName(string(n)) 282} 283