diff options
Diffstat (limited to 'cryptfs')
| -rw-r--r-- | cryptfs/cryptfile.go | 226 | ||||
| -rw-r--r-- | cryptfs/cryptfs.go | 172 | ||||
| -rw-r--r-- | cryptfs/cryptfs_content.go | 94 | ||||
| -rw-r--r-- | cryptfs/cryptfs_names.go | 150 | ||||
| -rw-r--r-- | cryptfs/intrablock.go | 39 |
5 files changed, 285 insertions, 396 deletions
diff --git a/cryptfs/cryptfile.go b/cryptfs/cryptfile.go deleted file mode 100644 index e5e9462..0000000 --- a/cryptfs/cryptfile.go +++ /dev/null @@ -1,226 +0,0 @@ -package cryptfs - -import ( - //"fmt" - "os" - //"io" - "errors" - "crypto/cipher" -) - -type CryptFile struct { - file *os.File - gcm cipher.AEAD -} - -// decryptBlock - Verify and decrypt GCM block -func (be *CryptFS) DecryptBlock(ciphertext []byte) ([]byte, error) { - - // Empty block? - if len(ciphertext) == 0 { - return ciphertext, nil - } - - if len(ciphertext) < NONCE_LEN { - warn.Printf("decryptBlock: Block is too short: %d bytes\n", len(ciphertext)) - return nil, errors.New("Block is too short") - } - - // Extract nonce - nonce := ciphertext[:NONCE_LEN] - ciphertext = ciphertext[NONCE_LEN:] - - // Decrypt - var plaintext []byte - plaintext, err := be.gcm.Open(plaintext, nonce, ciphertext, nil) - if err != nil { - return nil, err - } - - return plaintext, nil -} - -// encryptBlock - Encrypt and add MAC using GCM -func (be *CryptFS) EncryptBlock(plaintext []byte) []byte { - - // Empty block? - if len(plaintext) == 0 { - return plaintext - } - - // Get fresh nonce - nonce := gcmNonce.Get() - - // Encrypt plaintext and append to nonce - ciphertext := be.gcm.Seal(nonce, nonce, plaintext, nil) - - return ciphertext -} - -/* -// readCipherBlock - Read ciphertext block number "blockNo", decrypt, -// return plaintext -func (be *CryptFile) readCipherBlock(blockNo int64) ([]byte, error) { - off := blockNo * int64(be.cipherBS) - buf := make([]byte, be.cipherBS) - - readN, err := be.file.ReadAt(buf, off) - - if err != nil && err != io.EOF { - return nil, err - } - - // Truncate buffer to actually read bytes - buf = buf[:readN] - - // Empty block? - if len(buf) == 0 { - return buf, nil - } - - if len(buf) < NONCE_LEN { - warn.Printf("readCipherBlock: Block is too short: %d bytes\n", len(buf)) - return nil, errors.New("Block is too short") - } - - // Extract nonce - nonce := buf[:NONCE_LEN] - buf = buf[NONCE_LEN:] - - // Decrypt - var plainBuf []byte - plainBuf, err = be.gcm.Open(plainBuf, nonce, buf, nil) - if err != nil { - fmt.Printf("gcm.Open() failed: %d\n", err) - return nil, err - } - - return plainBuf, nil -} -*/ - -// intraBlock identifies a part of a file block -type intraBlock struct { - BlockNo uint64 // Block number in file - Offset uint64 // Offset into block plaintext - Length uint64 // Length of data from this block - fs *CryptFS -} - -// isPartial - is the block partial? This means we have to do read-modify-write. -func (ib *intraBlock) IsPartial() bool { - if ib.Offset > 0 || ib.Length < ib.fs.plainBS { - return true - } - return false -} - -// CiphertextRange - get byte range in ciphertext file corresponding to BlockNo -// (complete block) -func (ib *intraBlock) CiphertextRange() (offset uint64, length uint64) { - return ib.BlockNo * ib.fs.cipherBS, ib.fs.cipherBS -} - -// PlaintextRange - get byte range in plaintext corresponding to BlockNo -// (complete block) -func (ib *intraBlock) PlaintextRange() (offset uint64, length uint64) { - return ib.BlockNo * ib.fs.plainBS, ib.fs.plainBS -} - -// CropBlock - crop a potentially larger plaintext block down to the relevant part -func (ib *intraBlock) CropBlock(d []byte) []byte{ - lenHave := len(d) - lenWant := int(ib.Offset+ib.Length) - if lenHave < lenWant { - return d[ib.Offset:lenHave] - } - return d[ib.Offset:lenWant] -} - -// Split a plaintext byte range into (possible partial) blocks -func (be *CryptFS) SplitRange(offset uint64, length uint64) []intraBlock { - var b intraBlock - var parts []intraBlock - - b.fs = be - - for length > 0 { - b.BlockNo = offset / be.plainBS - b.Offset = offset % be.plainBS - b.Length = be.minu64(length, be.plainBS - b.Offset) - parts = append(parts, b) - offset += b.Length - length -= b.Length - } - return parts -} - -func (be *CryptFS) minu64(x uint64, y uint64) uint64 { - if x < y { - return x - } - return y -} - -/* -// writeCipherBlock - Encrypt plaintext and write it to file block "blockNo" -func (be *CryptFile) writeCipherBlock(blockNo int64, plain []byte) error { - - if int64(len(plain)) > be.plainBS { - panic("writeCipherBlock: Cannot write block that is larger than plainBS") - } - - // Get fresh nonce - nonce := gcmNonce.Get() - // Encrypt data and append to nonce - cipherBuf := be.gcm.Seal(nonce, nonce, plain, nil) - - // WriteAt retries short writes autmatically - written, err := be.file.WriteAt(cipherBuf, blockNo * be.cipherBS) - - debug.Printf("writeCipherBlock: wrote %d ciphertext bytes to block %d\n", - written, blockNo) - - return err -} - -// Perform RMW cycle on block -// Write "data" into file location specified in "b" -func (be *CryptFile) rmwWrite(b intraBlock, data []byte, f *os.File) error { - if b.Length != uint64(len(data)) { - panic("Length mismatch") - } - - oldBlock, err := be.readCipherBlock(b.BlockNo) - if err != nil { - return err - } - newBlockLen := b.Offset + b.Length - debug.Printf("newBlockLen := %d + %d\n", b.Offset, b.Length) - var newBlock []byte - - // Write goes beyond the old block and grows the file? - // Must create a bigger newBlock - if newBlockLen > uint64(len(oldBlock)) { - newBlock = make([]byte, newBlockLen) - } else { - newBlock = make([]byte, len(oldBlock)) - } - - // Fill with old data - copy(newBlock, oldBlock) - // Then overwrite the relevant parts with new data - copy(newBlock[b.Offset:b.Offset + b.Length], data) - - // Actual write - err = be.writeCipherBlock(b.BlockNo, newBlock) - - if err != nil { - // An incomplete write to a ciphertext block means that the whole block - // is destroyed. - fmt.Printf("rmwWrite: Write error: %s\n", err) - } - - return err -} -*/ diff --git a/cryptfs/cryptfs.go b/cryptfs/cryptfs.go index d385a77..9ec511a 100644 --- a/cryptfs/cryptfs.go +++ b/cryptfs/cryptfs.go @@ -1,21 +1,16 @@ package cryptfs +// CryptFS is the crypto backend of GoCryptFS + import ( "crypto/cipher" "crypto/aes" - "fmt" - "strings" - "encoding/base64" - "errors" ) const ( NONCE_LEN = 12 AUTH_TAG_LEN = 16 DEFAULT_PLAINBS = 4096 - - ENCRYPT = true - DECRYPT = false ) type CryptFS struct { @@ -45,169 +40,6 @@ func NewCryptFS(key [16]byte) *CryptFS { } } -/* -func (fs *CryptFS) NewFile(f *os.File) *CryptFile { - return &CryptFile { - file: f, - gcm: fs.gcm, - plainBS: fs.plainBS, - cipherBS: fs.cipherBS, - } -} -*/ - func (be *CryptFS) PlainBS() uint64 { return be.plainBS } - -// DecryptName - decrypt filename -func (be *CryptFS) decryptName(cipherName string) (string, error) { - - bin, err := base64.URLEncoding.DecodeString(cipherName) - if err != nil { - return "", err - } - - if len(bin) % aes.BlockSize != 0 { - return "", errors.New(fmt.Sprintf("Name len=%d is not a multiple of 16", len(bin))) - } - - iv := make([]byte, aes.BlockSize) // TODO ? - cbc := cipher.NewCBCDecrypter(be.blockCipher, iv) - cbc.CryptBlocks(bin, bin) - - bin, err = be.unPad16(bin) - if err != nil { - return "", err - } - - plain := string(bin) - return plain, err -} - -// EncryptName - encrypt filename -func (be *CryptFS) encryptName(plainName string) string { - - bin := []byte(plainName) - bin = be.pad16(bin) - - iv := make([]byte, 16) // TODO ? - cbc := cipher.NewCBCEncrypter(be.blockCipher, iv) - cbc.CryptBlocks(bin, bin) - - cipherName64 := base64.URLEncoding.EncodeToString(bin) - - return cipherName64 -} - -// TranslatePath - encrypt or decrypt path. Just splits the string on "/" -// and hands the parts to EncryptName() / DecryptName() -func (be *CryptFS) translatePath(path string, op bool) (string, error) { - var err error - - // Empty string means root directory - if path == "" { - return path, err - } - - // Run operation on each path component - var translatedParts []string - parts := strings.Split(path, "/") - for _, part := range parts { - var newPart string - if op == ENCRYPT { - newPart = be.encryptName(part) - } else { - newPart, err = be.decryptName(part) - if err != nil { - return "", err - } - } - translatedParts = append(translatedParts, newPart) - } - - return strings.Join(translatedParts, "/"), err -} - -// EncryptPath - encrypt filename or path. Just hands it to TranslatePath(). -func (be *CryptFS) EncryptPath(path string) string { - newPath, _ := be.translatePath(path, ENCRYPT) - return newPath -} - -// DecryptPath - decrypt filename or path. Just hands it to TranslatePath(). -func (be *CryptFS) DecryptPath(path string) (string, error) { - return be.translatePath(path, DECRYPT) -} - -// PlainSize - calculate plaintext size from ciphertext size -func (be *CryptFS) PlainSize(size uint64) uint64 { - // Zero sized files stay zero-sized - if size > 0 { - overhead := be.cipherBS - be.plainBS - nBlocks := (size + be.cipherBS - 1) / be.cipherBS - size -= nBlocks * overhead - } - return size -} - - -// plainSizeFromCipherSize - calculate plaintext size from ciphertext size -func (be *CryptFS) plainSizeFromCipherSize(size int64) int64 { - if size > 0 { - - } - return size -} -// pad16 - pad filename to 16 byte blocks using standard PKCS#7 padding -// https://tools.ietf.org/html/rfc5652#section-6.3 -func (be *CryptFS) pad16(orig []byte) (padded []byte) { - oldLen := len(orig) - if oldLen == 0 { - panic("Padding zero-length string makes no sense") - } - padLen := aes.BlockSize - oldLen % aes.BlockSize - if padLen == 0 { - padLen = aes.BlockSize - } - newLen := oldLen + padLen - padded = make([]byte, newLen) - copy(padded, orig) - padByte := byte(padLen) - for i := oldLen; i < newLen; i++ { - padded[i] = padByte - } - return padded -} - -// unPad16 - remove padding -func (be *CryptFS) unPad16(orig []byte) ([]byte, error) { - oldLen := len(orig) - if oldLen % aes.BlockSize != 0 { - return nil, errors.New("Unaligned size") - } - // The last byte is always a padding byte - padByte := orig[oldLen -1] - // The padding byte's value is the padding length - padLen := int(padByte) - // Padding must be at least 1 byte - if padLen <= 0 { - return nil, errors.New("Padding cannot be zero-length") - } - // Larger paddings make no sense - if padLen > aes.BlockSize { - return nil, errors.New("Padding cannot be larger than 16") - } - // All padding bytes must be identical - for i := oldLen - padLen; i < oldLen; i++ { - if orig[i] != padByte { - return nil, errors.New(fmt.Sprintf("Padding byte at i=%d is invalid", i)) - } - } - newLen := oldLen - padLen - // Padding an empty string makes no sense - if newLen == 0 { - return nil, errors.New("Unpadded length is zero") - } - return orig[0:newLen], nil -} diff --git a/cryptfs/cryptfs_content.go b/cryptfs/cryptfs_content.go new file mode 100644 index 0000000..b3c7f95 --- /dev/null +++ b/cryptfs/cryptfs_content.go @@ -0,0 +1,94 @@ +package cryptfs + +// File content encryption / decryption + +import ( + "os" + "errors" + "crypto/cipher" +) + +type CryptFile struct { + file *os.File + gcm cipher.AEAD +} + +// decryptBlock - Verify and decrypt GCM block +func (be *CryptFS) DecryptBlock(ciphertext []byte) ([]byte, error) { + + // Empty block? + if len(ciphertext) == 0 { + return ciphertext, nil + } + + if len(ciphertext) < NONCE_LEN { + warn.Printf("decryptBlock: Block is too short: %d bytes\n", len(ciphertext)) + return nil, errors.New("Block is too short") + } + + // Extract nonce + nonce := ciphertext[:NONCE_LEN] + ciphertext = ciphertext[NONCE_LEN:] + + // Decrypt + var plaintext []byte + plaintext, err := be.gcm.Open(plaintext, nonce, ciphertext, nil) + if err != nil { + return nil, err + } + + return plaintext, nil +} + +// encryptBlock - Encrypt and add MAC using GCM +func (be *CryptFS) EncryptBlock(plaintext []byte) []byte { + + // Empty block? + if len(plaintext) == 0 { + return plaintext + } + + // Get fresh nonce + nonce := gcmNonce.Get() + + // Encrypt plaintext and append to nonce + ciphertext := be.gcm.Seal(nonce, nonce, plaintext, nil) + + return ciphertext +} + +// Split a plaintext byte range into (possible partial) blocks +func (be *CryptFS) SplitRange(offset uint64, length uint64) []intraBlock { + var b intraBlock + var parts []intraBlock + + b.fs = be + + for length > 0 { + b.BlockNo = offset / be.plainBS + b.Offset = offset % be.plainBS + b.Length = be.minu64(length, be.plainBS - b.Offset) + parts = append(parts, b) + offset += b.Length + length -= b.Length + } + return parts +} + +// PlainSize - calculate plaintext size from ciphertext size +func (be *CryptFS) PlainSize(size uint64) uint64 { + // Zero sized files stay zero-sized + if size > 0 { + overhead := be.cipherBS - be.plainBS + nBlocks := (size + be.cipherBS - 1) / be.cipherBS + size -= nBlocks * overhead + } + return size +} + +func (be *CryptFS) minu64(x uint64, y uint64) uint64 { + if x < y { + return x + } + return y +} diff --git a/cryptfs/cryptfs_names.go b/cryptfs/cryptfs_names.go new file mode 100644 index 0000000..3dfcae9 --- /dev/null +++ b/cryptfs/cryptfs_names.go @@ -0,0 +1,150 @@ +package cryptfs + +// Filename encryption / decryption function + +import ( + "crypto/cipher" + "crypto/aes" + "fmt" + "strings" + "encoding/base64" + "errors" +) + +const ( + ENCRYPT = true + DECRYPT = false +) + +// DecryptName - decrypt filename +func (be *CryptFS) decryptName(cipherName string) (string, error) { + + bin, err := base64.URLEncoding.DecodeString(cipherName) + if err != nil { + return "", err + } + + if len(bin) % aes.BlockSize != 0 { + return "", errors.New(fmt.Sprintf("Name len=%d is not a multiple of 16", len(bin))) + } + + iv := make([]byte, aes.BlockSize) // TODO ? + cbc := cipher.NewCBCDecrypter(be.blockCipher, iv) + cbc.CryptBlocks(bin, bin) + + bin, err = be.unPad16(bin) + if err != nil { + return "", err + } + + plain := string(bin) + return plain, err +} + +// EncryptName - encrypt filename +func (be *CryptFS) encryptName(plainName string) string { + + bin := []byte(plainName) + bin = be.pad16(bin) + + iv := make([]byte, 16) // TODO ? + cbc := cipher.NewCBCEncrypter(be.blockCipher, iv) + cbc.CryptBlocks(bin, bin) + + cipherName64 := base64.URLEncoding.EncodeToString(bin) + + return cipherName64 +} + +// TranslatePath - encrypt or decrypt path. Just splits the string on "/" +// and hands the parts to EncryptName() / DecryptName() +func (be *CryptFS) translatePath(path string, op bool) (string, error) { + var err error + + // Empty string means root directory + if path == "" { + return path, err + } + + // Run operation on each path component + var translatedParts []string + parts := strings.Split(path, "/") + for _, part := range parts { + var newPart string + if op == ENCRYPT { + newPart = be.encryptName(part) + } else { + newPart, err = be.decryptName(part) + if err != nil { + return "", err + } + } + translatedParts = append(translatedParts, newPart) + } + + return strings.Join(translatedParts, "/"), err +} + +// EncryptPath - encrypt filename or path. Just hands it to TranslatePath(). +func (be *CryptFS) EncryptPath(path string) string { + newPath, _ := be.translatePath(path, ENCRYPT) + return newPath +} + +// DecryptPath - decrypt filename or path. Just hands it to TranslatePath(). +func (be *CryptFS) DecryptPath(path string) (string, error) { + return be.translatePath(path, DECRYPT) +} + +// pad16 - pad filename to 16 byte blocks using standard PKCS#7 padding +// https://tools.ietf.org/html/rfc5652#section-6.3 +func (be *CryptFS) pad16(orig []byte) (padded []byte) { + oldLen := len(orig) + if oldLen == 0 { + panic("Padding zero-length string makes no sense") + } + padLen := aes.BlockSize - oldLen % aes.BlockSize + if padLen == 0 { + padLen = aes.BlockSize + } + newLen := oldLen + padLen + padded = make([]byte, newLen) + copy(padded, orig) + padByte := byte(padLen) + for i := oldLen; i < newLen; i++ { + padded[i] = padByte + } + return padded +} + +// unPad16 - remove padding +func (be *CryptFS) unPad16(orig []byte) ([]byte, error) { + oldLen := len(orig) + if oldLen % aes.BlockSize != 0 { + return nil, errors.New("Unaligned size") + } + // The last byte is always a padding byte + padByte := orig[oldLen -1] + // The padding byte's value is the padding length + padLen := int(padByte) + // Padding must be at least 1 byte + if padLen <= 0 { + return nil, errors.New("Padding cannot be zero-length") + } + // Larger paddings make no sense + if padLen > aes.BlockSize { + return nil, errors.New("Padding cannot be larger than 16") + } + // All padding bytes must be identical + for i := oldLen - padLen; i < oldLen; i++ { + if orig[i] != padByte { + return nil, errors.New(fmt.Sprintf("Padding byte at i=%d is invalid", i)) + } + } + newLen := oldLen - padLen + // Padding an empty string makes no sense + if newLen == 0 { + return nil, errors.New("Unpadded length is zero") + } + return orig[0:newLen], nil +} diff --git a/cryptfs/intrablock.go b/cryptfs/intrablock.go new file mode 100644 index 0000000..78fd140 --- /dev/null +++ b/cryptfs/intrablock.go @@ -0,0 +1,39 @@ +package cryptfs + +// intraBlock identifies a part of a file block +type intraBlock struct { + BlockNo uint64 // Block number in file + Offset uint64 // Offset into block plaintext + Length uint64 // Length of data from this block + fs *CryptFS +} + +// isPartial - is the block partial? This means we have to do read-modify-write. +func (ib *intraBlock) IsPartial() bool { + if ib.Offset > 0 || ib.Length < ib.fs.plainBS { + return true + } + return false +} + +// CiphertextRange - get byte range in ciphertext file corresponding to BlockNo +// (complete block) +func (ib *intraBlock) CiphertextRange() (offset uint64, length uint64) { + return ib.BlockNo * ib.fs.cipherBS, ib.fs.cipherBS +} + +// PlaintextRange - get byte range in plaintext corresponding to BlockNo +// (complete block) +func (ib *intraBlock) PlaintextRange() (offset uint64, length uint64) { + return ib.BlockNo * ib.fs.plainBS, ib.fs.plainBS +} + +// CropBlock - crop a potentially larger plaintext block down to the relevant part +func (ib *intraBlock) CropBlock(d []byte) []byte{ + lenHave := len(d) + lenWant := int(ib.Offset+ib.Length) + if lenHave < lenWant { + return d[ib.Offset:lenHave] + } + return d[ib.Offset:lenWant] +} |