144 lines
3.8 KiB
Go
144 lines
3.8 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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"encoding/hex"
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"time"
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"io"
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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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// 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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// Now the owner name
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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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owner = owner[:off1]
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// digest buffer
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digest := append(owner, buf...)
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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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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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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 0
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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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for i, v := range buf[start:end] {
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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) Secure(rrset []RR, 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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return false
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}
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if s.Hdr.Class != k.Hdr.Class {
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return false
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}
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if s.Algorithm != k.Algorithm {
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return false
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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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