66 lines
1.5 KiB
Go
66 lines
1.5 KiB
Go
package dns
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import (
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"crypto/hmac"
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"io"
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)
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// Need to lookup the actual codes
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const (
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HmacMD5 = iota
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HmacSHA1
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)
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// The following values must be put in wireformat, so that
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// the MAC can be calculated
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// RFC 2845, section 3.4.2. TSIG Variables
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type tsig_generation_fmt struct {
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// From RR_HEADER
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Name string "domain-name"
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Class uint16
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Ttl uint32
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// Rdata of the TSIG
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Algorithm string "domain-name"
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TimeSigned [3]uint16 "TSIG"
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Fudge uint16
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// MACSize, MAC and OrigId excluded
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Error uint16
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OtherLen uint16
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OtherData string
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}
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// Generate the HMAC for msg. The TSIG RR is modified
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// to include the MAC and MACSize. Note the the msg Id must
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// be set, otherwise the MAC is not correct
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func (rr *RR_TSIG) GenerateMAC(msg *Msg, secret string) bool {
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buf := make([]byte, 4096) // TODO(mg) bufsize!
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tsigbuf := new(tsig_generation_fmt)
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// Fill the struct and generate the wiredata
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tsigbuf.Name = rr.Header().Name
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tsigbuf.Class = rr.Header().Class
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tsigbuf.Ttl = rr.Header().Ttl
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tsigbuf.Algorithm = rr.Algorithm
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tsigbuf.TimeSigned = rr.TimeSigned
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tsigbuf.Fudge = rr.Fudge
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tsigbuf.Error = rr.Error
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tsigbuf.OtherLen = rr.OtherLen
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tsigbuf.OtherData = rr.OtherData
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packStruct(tsigbuf, buf, 0)
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msgbuf, ok := msg.Pack()
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if !ok {
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return false
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}
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buf = append(buf, msgbuf...)
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//func NewMD5(key []byte) hash.Hash
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hmac := hmac.NewMD5([]byte(secret))
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io.WriteString(hmac, string(buf))
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rr.MAC = string(hmac.Sum())
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rr.MACSize = uint16(len(rr.MAC))
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rr.OrigId = msg.MsgHdr.Id
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return true
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}
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