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entropy.go
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entropy.go
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package rng
import (
"context"
"encoding/binary"
"github.com/tevino/abool"
"github.com/safing/portbase/container"
)
const (
minFeedEntropy = 256
)
var (
rngFeeder = make(chan []byte)
)
// The Feeder is used to feed entropy to the RNG.
type Feeder struct {
input chan *entropyData
entropy int64
needsEntropy *abool.AtomicBool
buffer *container.Container
}
type entropyData struct {
data []byte
entropy int
}
// NewFeeder returns a new entropy Feeder.
func NewFeeder() *Feeder {
new := &Feeder{
input: make(chan *entropyData),
needsEntropy: abool.NewBool(true),
buffer: container.New(),
}
module.StartServiceWorker("feeder", 0, new.run)
return new
}
// NeedsEntropy returns whether the feeder is currently gathering entropy.
func (f *Feeder) NeedsEntropy() bool {
return f.needsEntropy.IsSet()
}
// SupplyEntropy supplies entropy to to the Feeder, it will block until the Feeder has read from it.
func (f *Feeder) SupplyEntropy(data []byte, entropy int) {
f.input <- &entropyData{
data: data,
entropy: entropy,
}
}
// SupplyEntropyIfNeeded supplies entropy to to the Feeder, but will not block if no entropy is currently needed.
func (f *Feeder) SupplyEntropyIfNeeded(data []byte, entropy int) {
if f.needsEntropy.IsSet() {
return
}
select {
case f.input <- &entropyData{
data: data,
entropy: entropy,
}:
default:
}
}
// SupplyEntropyAsInt supplies entropy to to the Feeder, it will block until the Feeder has read from it.
func (f *Feeder) SupplyEntropyAsInt(n int64, entropy int) {
b := make([]byte, 8)
binary.LittleEndian.PutUint64(b, uint64(n))
f.SupplyEntropy(b, entropy)
}
// SupplyEntropyAsIntIfNeeded supplies entropy to to the Feeder, but will not block if no entropy is currently needed.
func (f *Feeder) SupplyEntropyAsIntIfNeeded(n int64, entropy int) {
if f.needsEntropy.IsSet() { // avoid allocating a slice if possible
b := make([]byte, 8)
binary.LittleEndian.PutUint64(b, uint64(n))
f.SupplyEntropyIfNeeded(b, entropy)
}
}
// CloseFeeder stops the feed processing - the responsible goroutine exits. The input channel is closed and the feeder may not be used anymore in any way.
func (f *Feeder) CloseFeeder() {
close(f.input)
}
func (f *Feeder) run(ctx context.Context) error {
defer f.needsEntropy.UnSet()
for {
// gather
f.needsEntropy.Set()
gather:
for {
select {
case newEntropy := <-f.input:
// check if feed has been closed
if newEntropy == nil {
return nil
}
// append to buffer
f.buffer.Append(newEntropy.data)
f.entropy += int64(newEntropy.entropy)
if f.entropy >= minFeedEntropy {
break gather
}
case <-ctx.Done():
return nil
}
}
// feed
f.needsEntropy.UnSet()
select {
case rngFeeder <- f.buffer.CompileData():
case <-ctx.Done():
return nil
}
f.buffer = container.New()
}
}