58 lines
1.3 KiB
Go
58 lines
1.3 KiB
Go
package dht
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import (
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"crypto/sha1"
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"encoding/binary"
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"time"
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"github.com/bradfitz/iter"
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)
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// Manages creation and validation of tokens issued to querying nodes.
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type tokenServer struct {
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// Something only we know that peers can't guess, so they can't deduce valid tokens.
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secret []byte
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// How long between token changes.
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interval time.Duration
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// How many intervals may pass between the current interval, and one used to generate a token before it is invalid.
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maxIntervalDelta int
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timeNow func() time.Time
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}
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func (me tokenServer) CreateToken(addr Addr) string {
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return me.createToken(addr, me.getTimeNow())
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}
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func (me tokenServer) createToken(addr Addr, t time.Time) string {
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h := sha1.New()
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ip := addr.UDPAddr().IP.To16()
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if len(ip) != 16 {
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panic(ip)
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}
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h.Write(ip)
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ti := t.UnixNano() / int64(me.interval)
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var b [8]byte
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binary.BigEndian.PutUint64(b[:], uint64(ti))
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h.Write(b[:])
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h.Write(me.secret)
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return string(h.Sum(nil))
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}
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func (me *tokenServer) ValidToken(token string, addr Addr) bool {
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t := me.getTimeNow()
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for range iter.N(me.maxIntervalDelta + 1) {
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if me.createToken(addr, t) == token {
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return true
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}
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t = t.Add(-me.interval)
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}
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return false
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}
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func (me *tokenServer) getTimeNow() time.Time {
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if me.timeNow == nil {
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return time.Now()
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}
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return me.timeNow()
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}
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