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100 lines
2.3 KiB
100 lines
2.3 KiB
package crypto
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import (
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"crypto/aes"
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"crypto/cipher"
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crand "crypto/rand"
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"encoding/hex"
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"io"
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"sync"
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. "github.com/tendermint/tmlibs/common"
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)
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var gRandInfo *randInfo
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func init() {
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gRandInfo = &randInfo{}
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gRandInfo.MixEntropy(randBytes(32)) // Init
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}
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// Mix additional bytes of randomness, e.g. from hardware, user-input, etc.
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// It is OK to call it multiple times. It does not diminish security.
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func MixEntropy(seedBytes []byte) {
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gRandInfo.MixEntropy(seedBytes)
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}
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// This only uses the OS's randomness
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func randBytes(numBytes int) []byte {
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b := make([]byte, numBytes)
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_, err := crand.Read(b)
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if err != nil {
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PanicCrisis(err)
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}
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return b
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}
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// This uses the OS and the Seed(s).
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func CRandBytes(numBytes int) []byte {
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b := make([]byte, numBytes)
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_, err := gRandInfo.Read(b)
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if err != nil {
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PanicCrisis(err)
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}
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return b
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}
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// RandHex(24) gives 96 bits of randomness, strong enough for most purposes.
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func CRandHex(numDigits int) string {
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return hex.EncodeToString(CRandBytes(numDigits / 2))
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}
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// Returns a crand.Reader mixed with user-supplied entropy
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func CReader() io.Reader {
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return gRandInfo
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}
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//--------------------------------------------------------------------------------
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type randInfo struct {
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mtx sync.Mutex
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seedBytes [32]byte
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cipherAES256 cipher.Block
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streamAES256 cipher.Stream
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reader io.Reader
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}
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// You can call this as many times as you'd like.
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// XXX TODO review
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func (ri *randInfo) MixEntropy(seedBytes []byte) {
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ri.mtx.Lock()
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defer ri.mtx.Unlock()
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// Make new ri.seedBytes
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hashBytes := Sha256(seedBytes)
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hashBytes32 := [32]byte{}
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copy(hashBytes32[:], hashBytes)
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ri.seedBytes = xorBytes32(ri.seedBytes, hashBytes32)
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// Create new cipher.Block
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var err error
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ri.cipherAES256, err = aes.NewCipher(ri.seedBytes[:])
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if err != nil {
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PanicSanity("Error creating AES256 cipher: " + err.Error())
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}
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// Create new stream
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ri.streamAES256 = cipher.NewCTR(ri.cipherAES256, randBytes(aes.BlockSize))
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// Create new reader
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ri.reader = &cipher.StreamReader{S: ri.streamAES256, R: crand.Reader}
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}
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func (ri *randInfo) Read(b []byte) (n int, err error) {
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ri.mtx.Lock()
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defer ri.mtx.Unlock()
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return ri.reader.Read(b)
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}
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func xorBytes32(bytesA [32]byte, bytesB [32]byte) (res [32]byte) {
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for i, b := range bytesA {
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res[i] = b ^ bytesB[i]
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}
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return res
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}
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