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// Copyright (c) 2019 Andreas Auernhammer. All rights reserved.
// Use of this source code is governed by a license that can be
// found in the LICENSE file.
// Package sioutil implements some I/O utility functions.
package sioutil
import (
"crypto/rand"
"io"
"golang.org/x/sys/cpu"
)
type nopCloser struct {
io.Writer
}
func (nopCloser) Close() error { return nil }
// NopCloser returns a WriteCloser that wraps w
// and implements Close as a no-op.
func NopCloser(w io.Writer) io.WriteCloser {
return nopCloser{w}
}
// NativeAES returns true when the executing CPU
// provides AES-GCM hardware instructions and
// an optimized assembler implementation is
// available.
//
// It is strongly recommended to only use AES-GCM
// when NativeAES() returns true. Otherwise, the
// AES-GCM implementation may be vulnerable to
// timing attacks.
// See: https://golang.org/pkg/crypto/aes
func NativeAES() bool {
if cpu.X86.HasAES && cpu.X86.HasPCLMULQDQ {
return true
}
if cpu.ARM64.HasAES {
return true
}
// Go 1.14 introduces an AES-GCM asm implementation
// for PPC64le. Therefore, we have to use build tags
// to determine whether we're compiling for PPC64 and
// use Go 1.14 (or newer).
// TODO(aead): Once we drop Go 1.13 support
// (bump go version in go.mod) we can remove
// pcc64-related build tags again.
if ppcHasAES {
return true
}
// On s390x, aes.NewCipher(...) returns a type
// that provides AES asm implementations only
// if all (CBC, CTR and GCM) AES hardware
// instructions are available.
// See: https://golang.org/src/crypto/aes/cipher_s390x.go#L39
return cpu.S390X.HasAES && cpu.S390X.HasAESCBC && cpu.S390X.HasAESCTR &&
(cpu.S390X.HasAESGCM || cpu.S390X.HasGHASH)
}
// Random returns n randomly generated bytes if
// and only if err == nil.
//
// Random uses crypto/rand.Reader as cryptographically
// secure random number generator (CSPRNG).
func Random(n int) (b []byte, err error) {
b = make([]byte, n)
if _, err = io.ReadFull(rand.Reader, b); err != nil {
return nil, err
}
return b, nil
}
// MustRandom returns n randomly generated bytes.
// It panics if it fails to read n random bytes
// from its entropy source.
//
// MustRandom uses crypto/rand.Reader as cryptographically
// secure random number generator (CSPRNG).
func MustRandom(n int) []byte {
b, err := Random(n)
if err != nil {
panic("sioutil: out of entropy: " + err.Error())
}
return b
}
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