mirror of
https://github.com/ceph/ceph-csi.git
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99 lines
2.9 KiB
Go
99 lines
2.9 KiB
Go
/*
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* rand.go - Reader used to generate secure random data for fscrypt.
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*
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* Copyright 2017 Google Inc.
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* Author: Joe Richey (joerichey@google.com)
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may not
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* use this file except in compliance with the License. You may obtain a copy of
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* the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations under
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* the License.
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*/
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package crypto
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import (
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"io"
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"github.com/pkg/errors"
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"golang.org/x/sys/unix"
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)
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// NewRandomBuffer uses the Linux Getrandom() syscall to create random bytes. If
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// the operating system has insufficient randomness, the buffer creation will
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// fail. This is an improvement over Go's built-in crypto/rand which will still
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// return bytes if the system has insufficiency entropy.
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// See: https://github.com/golang/go/issues/19274
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//
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// While this syscall was only introduced in Kernel v3.17, it predates the
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// introduction of filesystem encryption, so it introduces no additional
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// compatibility issues.
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func NewRandomBuffer(length int) ([]byte, error) {
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buffer := make([]byte, length)
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if _, err := io.ReadFull(randReader{}, buffer); err != nil {
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return nil, err
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}
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return buffer, nil
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}
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// NewRandomKey creates a random key of the specified length. This function uses
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// the same random number generation process as NewRandomBuffer.
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func NewRandomKey(length int) (*Key, error) {
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return NewFixedLengthKeyFromReader(randReader{}, length)
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}
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// NewRandomPassphrase creates a random passphrase of the specified length
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// containing random alphabetic characters.
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func NewRandomPassphrase(length int) (*Key, error) {
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chars := []byte("abcdefghijklmnopqrstuvwxyz")
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passphrase, err := NewBlankKey(length)
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if err != nil {
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return nil, err
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}
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for i := 0; i < length; {
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// Get some random bytes.
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raw, err := NewRandomKey((length - i) * 2)
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if err != nil {
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return nil, err
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}
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// Translate the random bytes into random characters.
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for _, b := range raw.data {
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if int(b) >= 256-(256%len(chars)) {
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// Avoid bias towards the first characters in the list.
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continue
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}
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c := chars[int(b)%len(chars)]
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passphrase.data[i] = c
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i++
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if i == length {
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break
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}
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}
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raw.Wipe()
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}
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return passphrase, nil
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}
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// randReader just calls into Getrandom, so no internal data is needed.
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type randReader struct{}
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func (r randReader) Read(buffer []byte) (int, error) {
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n, err := unix.Getrandom(buffer, unix.GRND_NONBLOCK)
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switch err {
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case nil:
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return n, nil
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case unix.EAGAIN:
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err = errors.New("insufficient entropy in pool")
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case unix.ENOSYS:
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err = errors.New("kernel must be v3.17 or later")
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}
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return 0, errors.Wrap(err, "getrandom() failed")
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}
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