235 lines
6.1 KiB
Go
235 lines
6.1 KiB
Go
package dns
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import (
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"crypto/sha1"
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"crypto/sha256"
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"crypto/rsa"
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"encoding/hex"
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"encoding/base64"
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"time"
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"io"
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"big"
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"sort"
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"strings"
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"fmt" //tmp
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"os" //tmp
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)
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const (
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// RFC1982 serial arithmetic
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year68 = 2 << (32 - 1)
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)
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// An RRset is just a bunch a RRs. No restrictions
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type RRset []RR
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func (r RRset) Len() int { return len(r) }
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func (r RRset) Less(i, j int) bool { return r[i].Header().Name < r[j].Header().Name }
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func (r RRset) Swap(i, j int) { r[i], r[j] = r[j], r[i] }
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// Convert an DNSKEY record to a DS record.
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func (k *RR_DNSKEY) ToDS(hash int) *RR_DS {
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ds := new(RR_DS)
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ds.Hdr.Name = k.Hdr.Name
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ds.Hdr.Class = k.Hdr.Class
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ds.Hdr.Ttl = k.Hdr.Ttl
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ds.Hdr.Rrtype = TypeDS
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ds.KeyTag = k.KeyTag()
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ds.Algorithm = k.Algorithm
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ds.DigestType = uint8(hash)
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// Generic function that gives back a buffer with the rdata?? TODO(MG)
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// Find the rdata portion for the key (again)
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// (keytag does this too)
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buf := make([]byte, 4096)
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off1, ok := packRR(k, buf, 0)
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if !ok {
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return nil
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}
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start := off1 - int(k.Header().Rdlength)
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end := start + int(k.Header().Rdlength)
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// buf[start:end] is the rdata of the key
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buf = buf[start:end]
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owner := make([]byte, 255)
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off1, ok = packDomainName(k.Hdr.Name, owner, 0)
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if !ok {
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return nil
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}
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/*
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* from RFC4034
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* digest = digest_algorithm( DNSKEY owner name | DNSKEY RDATA);
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* "|" denotes concatenation
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* DNSKEY RDATA = Flags | Protocol | Algorithm | Public Key.
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*/
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owner = owner[:off1]
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// digest buffer
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digest := append(owner, buf...)
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switch hash {
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case HashSHA1:
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s := sha1.New()
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io.WriteString(s, string(digest))
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ds.Digest = hex.EncodeToString(s.Sum())
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case HashSHA256:
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s := sha256.New()
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io.WriteString(s, string(digest))
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ds.Digest = hex.EncodeToString(s.Sum())
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case HashGOST94:
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default:
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// wrong hash value
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return nil
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}
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return ds
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}
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// Calculate the keytag of the DNSKEY.
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func (k *RR_DNSKEY) KeyTag() uint16 {
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var keytag int
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switch k.Algorithm {
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case AlgRSAMD5:
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println("Keytag RSAMD5. Todo")
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keytag = 0
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default:
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// Might encode header length too, so that
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// we dont need to pack/unpack all the time
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// Or a shadow structure, with the wiredata and header
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wire, ok := wireRdata(k)
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if !ok {
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return 0
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}
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for i, v := range wire {
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if i&1 != 0 {
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keytag += int(v) // must be larger than uint32
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} else {
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keytag += int(v) << 8
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}
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}
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keytag += (keytag >> 16) & 0xFFFF
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keytag &= 0xFFFF
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}
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return uint16(keytag)
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}
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// Validate an rrset with the signature and key. This is the
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// cryptographic test, the validity period most be check separately.
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func (s *RR_RRSIG) Verify(rrset RRset, k *RR_DNSKEY) bool {
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// Frist the easy checks
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if s.KeyTag != k.KeyTag() {
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println(s.KeyTag)
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println(k.KeyTag())
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return false
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}
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if s.Hdr.Class != k.Hdr.Class {
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println("Class")
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return false
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}
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if s.Algorithm != k.Algorithm {
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println("Class")
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return false
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}
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if s.SignerName != k.Hdr.Name {
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println(s.SignerName)
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println(k.Hdr.Name)
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return false
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}
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for _, r := range rrset {
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if r.Header().Class != s.Hdr.Class {
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return false
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}
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if r.Header().Rrtype != s.TypeCovered {
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return false
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}
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// Number of labels. TODO(mg) add helper functions
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}
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sort.Sort(rrset)
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// RFC 4035 5.3.2. Reconstructing the Signed Data
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signeddata := make([]byte, 10240) // 10 Kb??
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// Copy the sig, except the rrsig data
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// Can this be done easier? TODO(mg)
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s1 := &RR_RRSIG{s.Hdr, s.TypeCovered, s.Algorithm, s.Labels, s.OrigTtl, s.Expiration, s.Inception, s.KeyTag, s.SignerName, ""}
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buf, ok := wireRdata(s1)
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if !ok {
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return false
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}
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copy(signeddata, buf)
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off := len(buf)
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fmt.Fprintf(os.Stderr, "off %d\n", off)
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for _, r := range rrset {
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h := r.Header()
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// RFC 4034: 6.2. Canonical RR Form. (2) - domain name to lowercase
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name := h.Name
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h.Name = strings.ToLower(h.Name)
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// 6.2. Canonical RR Form. (3) - domain rdata to lowercaser
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switch h.Rrtype {
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case TypeNS, TypeCNAME, TypeSOA, TypeMB, TypeMG, TypeMR, TypePTR:
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case TypeHINFO, TypeMINFO, TypeMX /* TypeRP, TypeAFSDB, TypeRT */ :
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case TypeSIG /* TypePX, TypeNXT /* TypeNAPTR, TypeKX */ :
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case TypeSRV, /* TypeDNAME, TypeA6 */ TypeRRSIG, TypeNSEC:
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/* do something */
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// lower case the strings rdata //
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}
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// 6.2. Canonical RR Form. (4) - wildcards, don't understand
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// 6.2. Canonical RR Form. (5) - origTTL
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ttl := h.Ttl
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h.Ttl = s.OrigTtl
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off, ok = packRR(r, signeddata, off)
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h.Ttl = ttl // restore the order in the universe
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h.Name = name
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if !ok {
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println("Failure to pack")
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return false
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}
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}
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signeddata = signeddata[:off]
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keybuf := make([]byte, 1024)
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keybuflen := base64.StdEncoding.DecodedLen(len(k.PubKey))
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base64.StdEncoding.Decode(keybuf[0:keybuflen], []byte(k.PubKey))
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sigbuf := make([]byte, 1024)
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sigbuflen := base64.StdEncoding.DecodedLen(len(s.Signature))
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base64.StdEncoding.Decode(sigbuf[0:sigbuflen], []byte(s.Signature))
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switch s.Algorithm {
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case AlgRSASHA1:
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case AlgRSASHA256:
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// RFC 3110, section 2. RSA Public KEY Resource Records
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// Assume length is in the first byte!
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_E := int(keybuf[3]) <<16
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_E += int(keybuf[2]) <<8
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_E += int(keybuf[1])
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pubkey := new(rsa.PublicKey)
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pubkey.E = _E
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pubkey.N = big.NewInt(0)
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pubkey.N.SetBytes(keybuf[4:])
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fmt.Fprintf(os.Stderr, "%s\n", pubkey.N)
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}
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return true
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}
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// Using RFC1982 calculate if a signature period is valid
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func (s *RR_RRSIG) PeriodOK() bool {
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utc := time.UTC().Seconds()
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modi := (int64(s.Inception) - utc) / year68
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mode := (int64(s.Expiration) - utc) / year68
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ti := int64(s.Inception) + (modi * year68)
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te := int64(s.Expiration) + (mode * year68)
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return ti <= utc && utc <= te
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}
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// Translate the RRSIG's incep. and expir. time to the correct date.
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// Taking into account serial arithmetic (RFC 1982)
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func timeToDate(t uint32) string {
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utc := time.UTC().Seconds()
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mod := (int64(t) - utc) / year68
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// If needed assume wrap around(s)
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ti := time.SecondsToUTC(int64(t) + (mod * year68)) // abs()? TODO
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return ti.Format("20060102030405")
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}
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