contentenc

package
v0.0.0-...-ece74ff Latest Latest
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 Go to latest Published: Jun 11, 2021 License: MIT Imports: 12 Imported by: 0

Documentation

Overview

Package contentenc encrypts and decrypts file blocks.

Index

Constants

View Source 
const (
	// CurrentVersion is the current On-Disk-Format version
	CurrentVersion = 2

	// HeaderLen is the total header length
	HeaderLen = headerVersionLen + headerIDLen
)

Variables

This section is empty.

Functions

func JointPlaintextRange 

func JointPlaintextRange(blocks []IntraBlock) (offset uint64, length uint64)

JointPlaintextRange is the plaintext range corresponding to the sum of all "blocks" (complete blocks)

func MinUint64 

func MinUint64(x uint64, y uint64) uint64

MinUint64 returns the minimum of two uint64 values.

Types

type ContentEnc 

type ContentEnc struct {

	// Ciphertext request data pool. Always returns byte slices of size
	// fuse.MAX_KERNEL_WRITE + encryption overhead.
	// Used by Read() to temporarily store the ciphertext as it is read from
	// disk.
	CReqPool bPool
	// Plaintext request data pool. Slice have size fuse.MAX_KERNEL_WRITE.
	PReqPool bPool
	// contains filtered or unexported fields
}

ContentEnc is used to encipher and decipher file content.

func New 

func New(cc *cryptocore.CryptoCore, plainBS uint64, forceDecode bool) *ContentEnc

New returns an initialized ContentEnc instance.

func (*ContentEnc) BlockNoToCipherOff 

func (be *ContentEnc) BlockNoToCipherOff(blockNo uint64) uint64

BlockNoToCipherOff gets the ciphertext offset of block "blockNo"

func (*ContentEnc) BlockNoToPlainOff 

func (be *ContentEnc) BlockNoToPlainOff(blockNo uint64) uint64

BlockNoToPlainOff gets the plaintext offset of block "blockNo"

func (*ContentEnc) BlockOverhead 

func (be *ContentEnc) BlockOverhead() uint64

BlockOverhead returns the per-block overhead.

func (*ContentEnc) CipherBS 

func (be *ContentEnc) CipherBS() uint64

CipherBS returns the ciphertext block size

func (*ContentEnc) CipherOffToBlockNo 

func (be *ContentEnc) CipherOffToBlockNo(cipherOffset uint64) uint64

CipherOffToBlockNo converts the ciphertext offset to the plaintext block number.

func (*ContentEnc) CipherSizeToPlainSize 

func (be *ContentEnc) CipherSizeToPlainSize(cipherSize uint64) uint64

CipherSizeToPlainSize calculates the plaintext size `plainSize` from a ciphertext size `cipherSize` (in bytes).

Not all ciphertext sizes are legal due to the per-block overheads. For an illegal cipherSize, we return a best guess plainSize.

func (*ContentEnc) DecryptBlock 

func (be *ContentEnc) DecryptBlock(ciphertext []byte, blockNo uint64, fileID []byte) ([]byte, error)

DecryptBlock - Verify and decrypt GCM block

Corner case: A full-sized block of all-zero ciphertext bytes is translated to an all-zero plaintext block, i.e. file hole passthrough.

func (*ContentEnc) DecryptBlocks 

func (be *ContentEnc) DecryptBlocks(ciphertext []byte, firstBlockNo uint64, fileID []byte) ([]byte, error)

DecryptBlocks decrypts a number of blocks

func (*ContentEnc) EncryptBlock 

func (be *ContentEnc) EncryptBlock(plaintext []byte, blockNo uint64, fileID []byte) []byte

EncryptBlock - Encrypt plaintext using a random nonce. blockNo and fileID are used as associated data. The output is nonce + ciphertext + tag.

func (*ContentEnc) EncryptBlockNonce 

func (be *ContentEnc) EncryptBlockNonce(plaintext []byte, blockNo uint64, fileID []byte, nonce []byte) []byte

EncryptBlockNonce - Encrypt plaintext using a nonce chosen by the caller. blockNo and fileID are used as associated data. The output is nonce + ciphertext + tag. This function can only be used in SIV mode.

func (*ContentEnc) EncryptBlocks 

func (be *ContentEnc) EncryptBlocks(plaintextBlocks [][]byte, firstBlockNo uint64, fileID []byte) []byte

EncryptBlocks is like EncryptBlock but takes multiple plaintext blocks. Returns a byte slice from CReqPool - so don't forget to return it to the pool.

func (*ContentEnc) ExplodeCipherRange 

func (be *ContentEnc) ExplodeCipherRange(offset uint64, length uint64) []IntraBlock

ExplodeCipherRange splits a ciphertext byte range into (possibly partial) blocks This is used in reverse mode when reading files

func (*ContentEnc) ExplodePlainRange 

func (be *ContentEnc) ExplodePlainRange(offset uint64, length uint64) []IntraBlock

ExplodePlainRange splits a plaintext byte range into (possibly partial) blocks Returns an empty slice if length == 0.

func (*ContentEnc) MergeBlocks 

func (be *ContentEnc) MergeBlocks(oldData []byte, newData []byte, offset int) []byte

MergeBlocks - Merge newData into oldData at offset New block may be bigger than both newData and oldData

func (*ContentEnc) PlainBS 

func (be *ContentEnc) PlainBS() uint64

PlainBS returns the plaintext block size

func (*ContentEnc) PlainOffToBlockNo 

func (be *ContentEnc) PlainOffToBlockNo(plainOffset uint64) uint64

PlainOffToBlockNo converts a plaintext offset to the ciphertext block number.

func (*ContentEnc) PlainOffToCipherOff 

func (be *ContentEnc) PlainOffToCipherOff(plainOff uint64) uint64

PlainOffToCipherOff tells you the highest ciphertext offset that is *guaranteed* to be written/read when you write/read at `plainOff`.

func (*ContentEnc) PlainSizeToCipherSize 

func (be *ContentEnc) PlainSizeToCipherSize(plainSize uint64) uint64

PlainSizeToCipherSize calculates the ciphertext size from a plaintext size.

func (*ContentEnc) Wipe 

func (be *ContentEnc) Wipe()

Wipe tries to wipe secret keys from memory by overwriting them with zeros and/or setting references to nil.

type FileHeader 

type FileHeader struct {
	Version uint16
	ID      []byte
}

FileHeader represents the header stored on each non-empty file.

func ParseHeader 

func ParseHeader(buf []byte) (*FileHeader, error)

ParseHeader - parse "buf" into fileHeader object

func RandomHeader 

func RandomHeader() *FileHeader

RandomHeader - create new fileHeader object with random Id

func (*FileHeader) Pack 

func (h *FileHeader) Pack() []byte

Pack - serialize fileHeader object

type IntraBlock 

type IntraBlock struct {
	// BlockNo is the block number in the file
	BlockNo uint64
	// Skip is an offset into the block payload
	// In forward mode: block plaintext
	// In reverse mode: offset into block ciphertext. Takes the header into
	// account.
	Skip uint64
	// Length of payload data in this block
	// In forward mode: length of the plaintext
	// In reverse mode: length of the ciphertext. Takes header and trailer into
	// account.
	Length uint64
	// contains filtered or unexported fields
}

IntraBlock identifies a part of a file block

func (*IntraBlock) BlockCipherOff 

func (ib *IntraBlock) BlockCipherOff() (offset uint64)

BlockCipherOff returns the ciphertext offset corresponding to BlockNo

func (*IntraBlock) BlockPlainOff 

func (ib *IntraBlock) BlockPlainOff() (offset uint64)

BlockPlainOff returns the plaintext offset corresponding to BlockNo

func (*IntraBlock) CropBlock 

func (ib *IntraBlock) CropBlock(d []byte) []byte

CropBlock - crop a potentially larger plaintext block down to the relevant part

func (*IntraBlock) IsPartial 

func (ib *IntraBlock) IsPartial() bool

IsPartial - is the block partial? This means we have to do read-modify-write.

func (*IntraBlock) JointCiphertextRange 

func (ib *IntraBlock) JointCiphertextRange(blocks []IntraBlock) (offset uint64, length uint64)

JointCiphertextRange is the ciphertext range corresponding to the sum of all "blocks" (complete blocks)

type NonceMode 

type NonceMode int

NonceMode determines how nonces are created. 

const (
	// DefaultBS is the default plaintext block size
	DefaultBS = 4096
	// DefaultIVBits is the default length of IV, in bits.
	// We always use 128-bit IVs for file content, but the
	// master key in the config file is encrypted with a 96-bit IV for
	// gocryptfs v1.2 and earlier. v1.3 switched to 128 bit.
	DefaultIVBits = 128

	// RandomNonce chooses a random nonce.
	RandomNonce NonceMode = iota
	// ReverseDeterministicNonce chooses a deterministic nonce, suitable for
	// use in reverse mode.
	ReverseDeterministicNonce NonceMode = iota
	// ExternalNonce derives a nonce from external sources.
	ExternalNonce NonceMode = iota
)

Source Files

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