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Hash DRBG implementation in Go (Golang) from the TOR project
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/* | |
* Copyright (c) 2014, Yawning Angel <yawning at torproject dot org> | |
* All rights reserved. | |
* | |
* Redistribution and use in source and binary forms, with or without | |
* modification, are permitted provided that the following conditions are met: | |
* | |
* * Redistributions of source code must retain the above copyright notice, | |
* this list of conditions and the following disclaimer. | |
* | |
* * Redistributions in binary form must reproduce the above copyright notice, | |
* this list of conditions and the following disclaimer in the documentation | |
* and/or other materials provided with the distribution. | |
* | |
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" | |
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE | |
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR | |
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF | |
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS | |
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN | |
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) | |
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE | |
* POSSIBILITY OF SUCH DAMAGE. | |
*/ | |
// Package csrand implements the math/rand interface over crypto/rand, along | |
// with some utility functions for common random number/byte related tasks. | |
// | |
// Not all of the convinience routines are replicated, only those that are | |
// immediately useful. The Rand variable provides access to the full math/rand | |
// API. | |
package csrand | |
import ( | |
cryptRand "crypto/rand" | |
"encoding/binary" | |
"fmt" | |
"io" | |
"math/rand" | |
) | |
var ( | |
csRandSourceInstance csRandSource | |
// Rand is a math/rand instance backed by crypto/rand CSPRNG. | |
Rand = rand.New(csRandSourceInstance) | |
) | |
type csRandSource struct { | |
// This does not keep any state as it is backed by crypto/rand. | |
} | |
func (r csRandSource) Int63() int64 { | |
var src [8]byte | |
if err := Bytes(src[:]); err != nil { | |
panic(err) | |
} | |
val := binary.BigEndian.Uint64(src[:]) | |
val &= (1<<63 - 1) | |
return int64(val) | |
} | |
func (r csRandSource) Seed(seed int64) { | |
// No-op. | |
} | |
// Intn returns, as a int, a pseudo random number in [0, n). | |
func Intn(n int) int { | |
return Rand.Intn(n) | |
} | |
// Float64 returns, as a float64, a pesudo random number in [0.0,1.0). | |
func Float64() float64 { | |
return Rand.Float64() | |
} | |
// IntRange returns a uniformly distributed int [min, max]. | |
func IntRange(min, max int) int { | |
if max < min { | |
panic(fmt.Sprintf("IntRange: min > max (%d, %d)", min, max)) | |
} | |
r := (max + 1) - min | |
ret := Rand.Intn(r) | |
return ret + min | |
} | |
// Bytes fills the slice with random data. | |
func Bytes(buf []byte) error { | |
if _, err := io.ReadFull(cryptRand.Reader, buf); err != nil { | |
return err | |
} | |
return nil | |
} | |
// Reader is a alias of rand.Reader. | |
var Reader = cryptRand.Reader |
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/* | |
* Copyright (c) 2014, Yawning Angel <yawning at torproject dot org> | |
* All rights reserved. | |
* | |
* Redistribution and use in source and binary forms, with or without | |
* modification, are permitted provided that the following conditions are met: | |
* | |
* * Redistributions of source code must retain the above copyright notice, | |
* this list of conditions and the following disclaimer. | |
* | |
* * Redistributions in binary form must reproduce the above copyright notice, | |
* this list of conditions and the following disclaimer in the documentation | |
* and/or other materials provided with the distribution. | |
* | |
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" | |
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE | |
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR | |
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF | |
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS | |
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN | |
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) | |
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE | |
* POSSIBILITY OF SUCH DAMAGE. | |
*/ | |
// Package drbg implements a minimalistic DRBG based off SipHash-2-4 in OFB | |
// mode. | |
package drbg | |
import ( | |
"encoding/binary" | |
"encoding/hex" | |
"fmt" | |
"hash" | |
"github.com/dchest/siphash" | |
"git.torproject.org/pluggable-transports/obfs4.git/common/csrand" | |
) | |
// Size is the length of the HashDrbg output. | |
const Size = siphash.Size | |
// SeedLength is the length of the HashDrbg seed. | |
const SeedLength = 16 + Size | |
// Seed is the initial state for a HashDrbg. It consists of a SipHash-2-4 | |
// key, and 8 bytes of initial data. | |
type Seed [SeedLength]byte | |
// Bytes returns a pointer to the raw HashDrbg seed. | |
func (seed *Seed) Bytes() *[SeedLength]byte { | |
return (*[SeedLength]byte)(seed) | |
} | |
// Hex returns the hexdecimal representation of the seed. | |
func (seed *Seed) Hex() string { | |
return hex.EncodeToString(seed.Bytes()[:]) | |
} | |
// NewSeed returns a Seed initialized with the runtime CSPRNG. | |
func NewSeed() (seed *Seed, err error) { | |
seed = new(Seed) | |
if err = csrand.Bytes(seed.Bytes()[:]); err != nil { | |
return nil, err | |
} | |
return | |
} | |
// SeedFromBytes creates a Seed from the raw bytes, truncating to SeedLength as | |
// appropriate. | |
func SeedFromBytes(src []byte) (seed *Seed, err error) { | |
if len(src) < SeedLength { | |
return nil, InvalidSeedLengthError(len(src)) | |
} | |
seed = new(Seed) | |
copy(seed.Bytes()[:], src) | |
return | |
} | |
// SeedFromHex creates a Seed from the hexdecimal representation, truncating to | |
// SeedLength as appropriate. | |
func SeedFromHex(encoded string) (seed *Seed, err error) { | |
var raw []byte | |
if raw, err = hex.DecodeString(encoded); err != nil { | |
return nil, err | |
} | |
return SeedFromBytes(raw) | |
} | |
// InvalidSeedLengthError is the error returned when the seed provided to the | |
// DRBG is an invalid length. | |
type InvalidSeedLengthError int | |
func (e InvalidSeedLengthError) Error() string { | |
return fmt.Sprintf("invalid seed length: %d", int(e)) | |
} | |
// HashDrbg is a CSDRBG based off of SipHash-2-4 in OFB mode. | |
type HashDrbg struct { | |
sip hash.Hash64 | |
ofb [Size]byte | |
} | |
// NewHashDrbg makes a HashDrbg instance based off an optional seed. The seed | |
// is truncated to SeedLength. | |
func NewHashDrbg(seed *Seed) (*HashDrbg, error) { | |
drbg := new(HashDrbg) | |
if seed == nil { | |
var err error | |
if seed, err = NewSeed(); err != nil { | |
return nil, err | |
} | |
} | |
drbg.sip = siphash.New(seed.Bytes()[:16]) | |
copy(drbg.ofb[:], seed.Bytes()[16:]) | |
return drbg, nil | |
} | |
// Int63 returns a uniformly distributed random integer [0, 1 << 63). | |
func (drbg *HashDrbg) Int63() int64 { | |
block := drbg.NextBlock() | |
ret := binary.BigEndian.Uint64(block) | |
ret &= (1<<63 - 1) | |
return int64(ret) | |
} | |
// Seed does nothing, call NewHashDrbg if you want to reseed. | |
func (drbg *HashDrbg) Seed(seed int64) { | |
// No-op. | |
} | |
// NextBlock returns the next 8 byte DRBG block. | |
func (drbg *HashDrbg) NextBlock() []byte { | |
drbg.sip.Write(drbg.ofb[:]) | |
copy(drbg.ofb[:], drbg.sip.Sum(nil)) | |
ret := make([]byte, Size) | |
copy(ret, drbg.ofb[:]) | |
return ret | |
} |
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