diff options
Diffstat (limited to 'src/mongo/gotools/vendor/src/golang.org/x/crypto/openpgp/packet/ocfb.go')
-rw-r--r-- | src/mongo/gotools/vendor/src/golang.org/x/crypto/openpgp/packet/ocfb.go | 143 |
1 files changed, 143 insertions, 0 deletions
diff --git a/src/mongo/gotools/vendor/src/golang.org/x/crypto/openpgp/packet/ocfb.go b/src/mongo/gotools/vendor/src/golang.org/x/crypto/openpgp/packet/ocfb.go new file mode 100644 index 00000000000..ce2a33a547c --- /dev/null +++ b/src/mongo/gotools/vendor/src/golang.org/x/crypto/openpgp/packet/ocfb.go @@ -0,0 +1,143 @@ +// Copyright 2010 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// OpenPGP CFB Mode. http://tools.ietf.org/html/rfc4880#section-13.9 + +package packet + +import ( + "crypto/cipher" +) + +type ocfbEncrypter struct { + b cipher.Block + fre []byte + outUsed int +} + +// An OCFBResyncOption determines if the "resynchronization step" of OCFB is +// performed. +type OCFBResyncOption bool + +const ( + OCFBResync OCFBResyncOption = true + OCFBNoResync OCFBResyncOption = false +) + +// NewOCFBEncrypter returns a cipher.Stream which encrypts data with OpenPGP's +// cipher feedback mode using the given cipher.Block, and an initial amount of +// ciphertext. randData must be random bytes and be the same length as the +// cipher.Block's block size. Resync determines if the "resynchronization step" +// from RFC 4880, 13.9 step 7 is performed. Different parts of OpenPGP vary on +// this point. +func NewOCFBEncrypter(block cipher.Block, randData []byte, resync OCFBResyncOption) (cipher.Stream, []byte) { + blockSize := block.BlockSize() + if len(randData) != blockSize { + return nil, nil + } + + x := &ocfbEncrypter{ + b: block, + fre: make([]byte, blockSize), + outUsed: 0, + } + prefix := make([]byte, blockSize+2) + + block.Encrypt(x.fre, x.fre) + for i := 0; i < blockSize; i++ { + prefix[i] = randData[i] ^ x.fre[i] + } + + block.Encrypt(x.fre, prefix[:blockSize]) + prefix[blockSize] = x.fre[0] ^ randData[blockSize-2] + prefix[blockSize+1] = x.fre[1] ^ randData[blockSize-1] + + if resync { + block.Encrypt(x.fre, prefix[2:]) + } else { + x.fre[0] = prefix[blockSize] + x.fre[1] = prefix[blockSize+1] + x.outUsed = 2 + } + return x, prefix +} + +func (x *ocfbEncrypter) XORKeyStream(dst, src []byte) { + for i := 0; i < len(src); i++ { + if x.outUsed == len(x.fre) { + x.b.Encrypt(x.fre, x.fre) + x.outUsed = 0 + } + + x.fre[x.outUsed] ^= src[i] + dst[i] = x.fre[x.outUsed] + x.outUsed++ + } +} + +type ocfbDecrypter struct { + b cipher.Block + fre []byte + outUsed int +} + +// NewOCFBDecrypter returns a cipher.Stream which decrypts data with OpenPGP's +// cipher feedback mode using the given cipher.Block. Prefix must be the first +// blockSize + 2 bytes of the ciphertext, where blockSize is the cipher.Block's +// block size. If an incorrect key is detected then nil is returned. On +// successful exit, blockSize+2 bytes of decrypted data are written into +// prefix. Resync determines if the "resynchronization step" from RFC 4880, +// 13.9 step 7 is performed. Different parts of OpenPGP vary on this point. +func NewOCFBDecrypter(block cipher.Block, prefix []byte, resync OCFBResyncOption) cipher.Stream { + blockSize := block.BlockSize() + if len(prefix) != blockSize+2 { + return nil + } + + x := &ocfbDecrypter{ + b: block, + fre: make([]byte, blockSize), + outUsed: 0, + } + prefixCopy := make([]byte, len(prefix)) + copy(prefixCopy, prefix) + + block.Encrypt(x.fre, x.fre) + for i := 0; i < blockSize; i++ { + prefixCopy[i] ^= x.fre[i] + } + + block.Encrypt(x.fre, prefix[:blockSize]) + prefixCopy[blockSize] ^= x.fre[0] + prefixCopy[blockSize+1] ^= x.fre[1] + + if prefixCopy[blockSize-2] != prefixCopy[blockSize] || + prefixCopy[blockSize-1] != prefixCopy[blockSize+1] { + return nil + } + + if resync { + block.Encrypt(x.fre, prefix[2:]) + } else { + x.fre[0] = prefix[blockSize] + x.fre[1] = prefix[blockSize+1] + x.outUsed = 2 + } + copy(prefix, prefixCopy) + return x +} + +func (x *ocfbDecrypter) XORKeyStream(dst, src []byte) { + for i := 0; i < len(src); i++ { + if x.outUsed == len(x.fre) { + x.b.Encrypt(x.fre, x.fre) + x.outUsed = 0 + } + + c := src[i] + dst[i] = x.fre[x.outUsed] ^ src[i] + x.fre[x.outUsed] = c + x.outUsed++ + } +} |