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container.go
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container.go
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package xmssmt
import (
"container/heap"
"encoding/binary"
"encoding/hex"
"io"
"os"
"path/filepath"
"github.com/bwesterb/byteswriter"
"github.com/edsrzf/mmap-go"
"github.com/hashicorp/go-multierror"
"github.com/nightlyone/lockfile"
)
// A PrivateKeyContainer has two tasks
//
// 1. It has to store the XMSS[MT] secret key and sequence number of the first
// unused signature.
// 2. It has to cache the precomputed subtrees to increase signing performance.
//
// NOTE A PrivateKeyContainer does not have to be thread safe.
type PrivateKeyContainer interface {
// Reset (or initialize) the cache that stores the subtrees. It is always
// called before use.
ResetCache() Error
// Returns the buffer for the given subtree. If the subtree does not
// have a buffer yet, allocate it of the size params.CachedSubTreeSize()
// with params as specified in the last call to Reset().
// The exists return value indicates whether the subtree was present.
// The container should write changes to buf back to the storage.
// The containe does not have to ensure integrity, a checksum is added
// to the end of the buffer.
GetSubTree(address SubTreeAddress) (buf []byte, exists bool, err Error)
// Returns whether the given subtree is in the cache. Returns false
// if the cache is not initialized.
HasSubTree(address SubTreeAddress) bool
// Drops the given subtree from the cache (if it was even cached to begin
// with).
DropSubTree(address SubTreeAddress) Error
// Returns the list of cached subtrees
ListSubTrees() ([]SubTreeAddress, Error)
// Reset (or initialize) the container with the given private key
// and parameters. Calls ResetCache().
Reset(privateKey []byte, params Params) Error
// Returns the current signature sequence number and increment
// the stored sequence number by the given amount.
// The user can use the signatures in this range freely,
// but should call SetSeqNo() later to record the actual number
// of signatures used.
BorrowSeqNos(amount uint32) (SignatureSeqNo, Error)
// Sets the signature sequence number to the given value.
// Removes the possible-lost-signatures record set by BorrowSeqNos.
SetSeqNo(seqNo SignatureSeqNo) Error
// Returns the current signature sequence number.
// If BorrowSeqNos() has been called without corresponding SetSeqNo()
// there might have been signatures lost. In that case, calls to
// GetSeqNo will return the number of possibly lost signatures
// until SetSeqNo() has been called.
GetSeqNo() (seqNo SignatureSeqNo, lostSigs uint32, err Error)
// Returns the private key.
GetPrivateKey() ([]byte, Error)
// Returns the algorithm parameters if the container is initialized
// (eg. the file exist) and nil if not.
Initialized() *Params
// Returns whether the cache is initialized. If not, it can be
// initialized by calling ResetCache().
CacheInitialized() bool
// Closes the container.
Close() Error
}
type mmapedSubTree struct {
mmap mmap.MMap
buf []byte
}
// PrivateKeyContainer backed by three files:
//
// path/to/key contains the secret key and signature sequence number
// path/to/key.lock a lockfile
// path/to/key.cache cached subtrees
type fsContainer struct {
// Fields relevant to a container, initialized or not
flock lockfile.Lockfile // file lock
path string // absolute base path
initialized bool
cacheInitialized bool
closed bool
// Fields set in an initialized container
params Params // parameters of the algorithm
privateKey []byte
seqNo SignatureSeqNo
borrowed uint32
// Fields relevant to a container with an initialized cache
cacheFile *os.File // the opened cache file
allocatedSubTrees uint32 // number of allocated cached subtrees
// maps subtree address to the index of the subtree in the cache
cacheIdxLut map[SubTreeAddress]uint32
// maps subtree address to an mmaped buffer
cacheBufLut map[SubTreeAddress]mmapedSubTree
cacheFreeIdx *uint32Heap // list of allocated but unused subtrees
subTreeAlignment int // multiple to which subtrees are aligned
pageSize int
}
const (
// First 8 bytes (in hex) of the secret key file
FS_CONTAINER_KEY_MAGIC = "4089430a5ced6844"
// First 8 bytes (in hex) of the subtree cache file
FS_CONTAINER_CACHE_MAGIC = "e77957607ef79446"
FS_CONTAINER_CACHE_MAGIC2 = "5a11d7cf4a1f6314"
)
// Returns a PrivateKeyContainer backed by the filesystem.
func OpenFSPrivateKeyContainer(path string) (PrivateKeyContainer, Error) {
var ctr fsContainer
var err error
ctr.path, err = filepath.Abs(path)
if err != nil {
return nil, wrapErrorf(err,
"Could not turn %s into an absolute path", path)
}
// Acquire lock
lockFilePath := ctr.path + ".lock"
ctr.flock, err = lockfile.New(lockFilePath)
if err != nil {
return nil, wrapErrorf(err,
"Failed to create lockfile %s", lockFilePath)
}
err = ctr.flock.TryLock()
if _, ok := err.(interface {
Temporary() bool
}); ok {
err2 := errorf("%s is locked", path)
err2.locked = true
return nil, err2
}
// Check if the container exists
if _, err = os.Stat(ctr.path); os.IsNotExist(err) {
return &ctr, nil
}
// Open the container.
file, err := os.Open(ctr.path)
if err != nil {
return &ctr, wrapErrorf(err, "Failed to open keyfile %s", path)
}
defer file.Close()
var keyHeader fsKeyHeader
err = binary.Read(file, binary.BigEndian, &keyHeader)
if err != nil {
return &ctr, wrapErrorf(err, "Failed to read keyfile header")
}
if FS_CONTAINER_KEY_MAGIC != hex.EncodeToString(keyHeader.Magic[:]) {
return &ctr, wrapErrorf(err, "Keyfile has invalid magic")
}
ctr.params = keyHeader.Params
ctr.privateKey = make([]byte, ctr.params.PrivateKeySize())
ctr.seqNo = keyHeader.SeqNo
ctr.borrowed = keyHeader.Borrowed
_, err = io.ReadAtLeast(file, ctr.privateKey, ctr.params.PrivateKeySize())
if err != nil {
return &ctr, wrapErrorf(err, "Failed to read private key")
}
ctr.initialized = true
return &ctr, ctr.openCache()
}
func (ctr *fsContainer) openCache() Error {
var err error
ctr.cacheIdxLut = make(map[SubTreeAddress]uint32)
ctr.cacheBufLut = make(map[SubTreeAddress]mmapedSubTree)
emptyHeap := uint32Heap([]uint32{})
ctr.cacheFreeIdx = &emptyHeap
heap.Init(ctr.cacheFreeIdx)
// Open cache file
cachePath := ctr.path + ".cache"
ctr.cacheFile, err = os.OpenFile(cachePath, os.O_RDWR, 0)
if err != nil {
return wrapErrorf(err, "Failed to open cache file")
}
// Read header
var header fsCacheHeader
err = binary.Read(ctr.cacheFile, binary.BigEndian, &header)
if err != nil {
return wrapErrorf(err, "Failed to read cache file header")
}
magic := hex.EncodeToString(header.Magic[:])
if magic != FS_CONTAINER_CACHE_MAGIC && magic != FS_CONTAINER_CACHE_MAGIC2 {
return wrapErrorf(err, "Cache file magic is wrong")
}
if magic == FS_CONTAINER_CACHE_MAGIC {
if header.Version != 0 {
return wrapErrorf(err, "Cache file version does not match magic")
}
ctr.subTreeAlignment = 4096
} else {
if header.Version != 1 {
return wrapErrorf(err, "Unsupported cache file version: %d",
header.Version)
}
ctr.subTreeAlignment = int(header.SubTreeAlignment)
}
ctr.pageSize = os.Getpagesize()
ctr.allocatedSubTrees = header.AllocatedSubTrees
// Read subtrees
var idx uint32
for idx = 0; idx < ctr.allocatedSubTrees; idx++ {
_, err = ctr.cacheFile.Seek(int64(ctr.subTreeOffset(idx)), 0)
if err != nil {
return wrapErrorf(err, "Failed to seek to subtree in cache")
}
var treeHeader fsSubTreeHeader
err = binary.Read(ctr.cacheFile, binary.BigEndian, &treeHeader)
if err != nil {
return wrapErrorf(err, "Failed to read subtree header in cache")
}
if treeHeader.Allocated == 0 {
heap.Push(ctr.cacheFreeIdx, idx)
} else {
ctr.cacheIdxLut[treeHeader.Address] = idx
}
}
ctr.cacheInitialized = true
return nil
}
// Header of the key file
type fsKeyHeader struct {
Magic [8]byte // Should be FS_CONTAINER_KEY_MAGIC
Params Params // Parameters
SeqNo SignatureSeqNo // Signature seqno
Borrowed uint32 // Number of signatures borrowed.
}
// Header of the cache file
type fsCacheHeader struct {
// Magic should be FS_CONTAINER_CACHE_MAGIC for version 0
// or FS_CONTAINER_CACHE_MAGIC2 for version ≥1.
Magic [8]byte
AllocatedSubTrees uint32 // Number of allocated subtrees
// The following fields are nonzero for format version ≥1.
// Version of the cache format.
//
// 0 Original with magic FS_CONTAINER_CACHE_MAGIC2
// 1 Second version which includes subtree alignment.
// Has magic FS_CONTAINER_CACHE_MAGIC2.
Version uint8
// Multiple to which subtrees are aligned. Zero is interpreted
// as 4096.
SubTreeAlignment uint32
}
// Header of a cached subtree
type fsSubTreeHeader struct {
// In older versions of Go, binary.Read/Write do not support bool
Allocated uint8
Address SubTreeAddress
}
func (ctr *fsContainer) CacheInitialized() bool {
return ctr.cacheInitialized
}
func (ctr *fsContainer) Initialized() *Params {
if !ctr.initialized {
return nil
}
return &ctr.params
}
func (ctr *fsContainer) ResetCache() Error {
var err Error
var err2 error
if !ctr.initialized {
err = errorf("Container is not initialized")
return err
}
// Close old cache
if ctr.cacheInitialized {
ctr.closeCache() // we ignore munmap failures
}
ctr.cacheBufLut = make(map[SubTreeAddress]mmapedSubTree)
ctr.cacheIdxLut = make(map[SubTreeAddress]uint32)
ctr.pageSize = os.Getpagesize()
ctr.subTreeAlignment = ctr.pageSize
if ctr.subTreeAlignment < 4096 {
ctr.subTreeAlignment = 4096
}
ctr.allocatedSubTrees = 0
emptyHeap := uint32Heap([]uint32{})
ctr.cacheFreeIdx = &emptyHeap
heap.Init(ctr.cacheFreeIdx)
// Open new cache
cachePath := ctr.path + ".cache"
ctr.cacheFile, err2 = os.OpenFile(
cachePath,
os.O_RDWR|os.O_CREATE|os.O_TRUNC,
0600)
if err2 != nil {
return wrapErrorf(err, "failed to create cache file")
}
if err = ctr.writeCacheHeader(); err != nil {
return err
}
ctr.cacheInitialized = true
return nil
}
func (ctr *fsContainer) writeCacheHeader() Error {
var err error
_, err = ctr.cacheFile.Seek(0, 0)
if err != nil {
return wrapErrorf(err, "failed to seek to start of cache file")
}
cacheHeader := fsCacheHeader{
AllocatedSubTrees: ctr.allocatedSubTrees,
Version: 1,
SubTreeAlignment: uint32(ctr.subTreeAlignment),
}
magic, _ := hex.DecodeString(FS_CONTAINER_CACHE_MAGIC2)
copy(cacheHeader.Magic[:], magic)
err = binary.Write(ctr.cacheFile, binary.BigEndian, &cacheHeader)
if err != nil {
ctr.cacheFile.Close()
return wrapErrorf(err, "failed to write to cache file")
}
return nil
}
// Returns the offset of the given cached subtree entry in the cache file.
// This offset point to the 13-byte header just in front of the actual data.
func (ctr *fsContainer) subTreeOffset(idx uint32) int {
// Find the smallest multiple of ctr.subTreeAlignment
// above CachedSubTreeSize() + 13, where 13 is the size of fsSubTreeHeader.
paddedSize := ((((ctr.params.CachedSubTreeSize() + 13) - 1) /
ctr.subTreeAlignment) + 1) * ctr.subTreeAlignment
return int(idx)*paddedSize + ctr.subTreeAlignment
}
func (ctr *fsContainer) mmapSubTree(idx uint32) (mmapedSubTree, error) {
realOffset := ctr.subTreeOffset(idx)
offset := realOffset % ctr.pageSize
buf, err := mmap.MapRegion(
ctr.cacheFile,
ctr.params.CachedSubTreeSize()+13+offset, // length
mmap.RDWR, // prot
0, // flags
int64(realOffset-offset),
)
if err != nil {
return mmapedSubTree{}, err
}
return mmapedSubTree{
mmap: buf,
buf: buf[offset:],
}, nil
}
func (ctr *fsContainer) GetSubTree(address SubTreeAddress) (
ret []byte, exists bool, err Error) {
if !ctr.cacheInitialized {
err = errorf("Cache is not initialized")
return nil, false, err
}
var err2 error
if buf, ok := ctr.cacheBufLut[address]; ok {
return []byte(buf.buf)[13:], true, nil
}
// Check if the subtree exists
if idx, ok := ctr.cacheIdxLut[address]; ok {
buf, err2 := ctr.mmapSubTree(idx)
if err2 != nil {
return nil, false, wrapErrorf(err2, "Failed to mmap subtree")
}
ctr.cacheBufLut[address] = buf
return []byte(buf.buf)[13:], true, nil
}
// Find a free cached subtree index
var idx uint32
if ctr.cacheFreeIdx.Len() != 0 {
idx = heap.Pop(ctr.cacheFreeIdx).(uint32)
} else {
idx = ctr.allocatedSubTrees
ctr.allocatedSubTrees += 1
err2 = ctr.cacheFile.Truncate(int64(
ctr.subTreeOffset(ctr.allocatedSubTrees)))
if err2 != nil {
return nil, false, wrapErrorf(err2,
"Failed to allocate space for subtree")
}
err = ctr.writeCacheHeader()
if err != nil {
return nil, false, err
}
}
buf, err2 := ctr.mmapSubTree(idx)
if err2 != nil {
return nil, false, wrapErrorf(err2, "Failed to mmap subtree from cache")
}
// Write information
header := fsSubTreeHeader{
Allocated: 1,
Address: address,
}
bufWriter := byteswriter.NewWriter(buf.buf)
err2 = binary.Write(bufWriter, binary.BigEndian, &header)
if err2 != nil {
err = wrapErrorf(err2, "Failed to write subtree header in cache")
return
}
ctr.cacheBufLut[address] = buf
ctr.cacheIdxLut[address] = idx
return buf.buf[13:], false, nil
}
func (ctr *fsContainer) ListSubTrees() ([]SubTreeAddress, Error) {
if !ctr.cacheInitialized {
return nil, errorf("Cache is not initialized")
}
ret := make([]SubTreeAddress, len(ctr.cacheIdxLut))
i := 0
for addr, _ := range ctr.cacheIdxLut {
ret[i] = addr
i++
}
return ret, nil
}
func (ctr *fsContainer) HasSubTree(address SubTreeAddress) bool {
if !ctr.cacheInitialized {
return false
}
_, ok := ctr.cacheIdxLut[address]
return ok
}
func (ctr *fsContainer) DropSubTree(address SubTreeAddress) Error {
if !ctr.cacheInitialized {
return errorf("Cache is not initialized")
}
// TODO decrement allocatedSubTrees and cacheFile.Truncate when
// applicable to free disk space.
var err2 error
idx, ok := ctr.cacheIdxLut[address]
if !ok {
return nil
}
buf, ok := ctr.cacheBufLut[address]
if !ok {
buf, err2 = ctr.mmapSubTree(idx)
}
if err2 != nil {
return wrapErrorf(err2, "Failed to mmap subtree from cache")
}
bufWriter := byteswriter.NewWriter(buf.buf)
var bFalse uint8 = 0
err2 = binary.Write(bufWriter, binary.BigEndian, &bFalse)
if err2 != nil {
return wrapErrorf(err2, "Failed to write subtree header in cache")
}
heap.Push(ctr.cacheFreeIdx, idx)
delete(ctr.cacheIdxLut, address)
delete(ctr.cacheBufLut, address)
err2 = buf.mmap.Unmap()
if err2 != nil {
return wrapErrorf(err2, "Failed to unmap sub tree")
}
return nil
}
func (ctr *fsContainer) Reset(privateKey []byte, params Params) Error {
if ctr.closed {
return errorf("Container is closed")
}
// Even if closing the cache fails, we will try to write the key file.
closeCacheErr := ctr.closeCache()
ctr.params = params
ctr.privateKey = privateKey
ctr.seqNo = 0
ctr.borrowed = 0
ctr.cacheInitialized = false
if err := ctr.writeKeyFile(); err != nil {
return err
}
if closeCacheErr != nil {
return wrapErrorf(closeCacheErr, "Failed to close old cache")
}
ctr.initialized = true
if err := ctr.ResetCache(); err != nil {
return err
}
return nil
}
func (ctr *fsContainer) BorrowSeqNos(amount uint32) (SignatureSeqNo, Error) {
if !ctr.initialized {
return 0, errorf("Container is not initialized")
}
ctr.borrowed += amount
ctr.seqNo += SignatureSeqNo(amount)
if err := ctr.writeKeyFile(); err != nil {
// rollback
ctr.borrowed -= amount
ctr.seqNo -= SignatureSeqNo(amount)
return 0, err
}
return ctr.seqNo - SignatureSeqNo(amount), nil
}
// Write key file to disk
func (ctr *fsContainer) writeKeyFile() Error {
var err error
// (1) Write to a temp file. (2) fsync this tempfile to get the data out.
// (3) Rename the tempfile to the acutal key file. (4) Finally, fsync
// the parent directory.
tmpPath := ctr.path + ".tmp"
tmpFile, err := os.OpenFile(
tmpPath,
os.O_WRONLY|os.O_CREATE|os.O_TRUNC,
0600)
if err != nil {
return wrapErrorf(err, "failed to create temporary key file")
}
// (1) Write temp file.
keyHeader := fsKeyHeader{
Params: ctr.params,
SeqNo: ctr.seqNo,
Borrowed: ctr.borrowed,
}
magic, _ := hex.DecodeString(FS_CONTAINER_KEY_MAGIC)
copy(keyHeader.Magic[:], magic)
if err = binary.Write(tmpFile, binary.BigEndian, &keyHeader); err != nil {
tmpFile.Close()
return wrapErrorf(err, "failed to write temporary key file")
}
if _, err = tmpFile.Write(ctr.privateKey); err != nil {
tmpFile.Close()
return wrapErrorf(err, "failed to write temporary key file")
}
// (2) Sync the tempfile
if err = tmpFile.Sync(); err != nil {
tmpFile.Close()
return wrapErrorf(err, "failed to sync temporary key file")
}
if err = tmpFile.Close(); err != nil {
return wrapErrorf(err, "failed to close temporary key file")
}
// (3) Rename the tempfile
if err = os.Rename(tmpPath, ctr.path); err != nil {
return wrapErrorf(err, "failed to replace key file")
}
// (4) Sync the parent directory. If this fails we have no way of knowing
// whether the changes have been written out to disk. We will assume that
// it did not, so that we won't reuse signatures.
dirName := filepath.Dir(ctr.path)
dir, err := os.Open(dirName)
if err != nil {
return wrapErrorf(err, "failed to sync key file: open(%s):", dirName)
}
if err = dir.Sync(); err != nil {
dir.Close()
return wrapErrorf(err, "failed to sync key file")
}
if err = dir.Close(); err != nil {
return wrapErrorf(err, "failed to sync key file (close)")
}
return nil
}
func (ctr *fsContainer) SetSeqNo(seqNo SignatureSeqNo) Error {
if !ctr.initialized {
return errorf("Container is not initialized")
}
oldBorrowed := ctr.borrowed
oldSeqNo := ctr.seqNo
ctr.borrowed = 0
ctr.seqNo = seqNo
if err := ctr.writeKeyFile(); err != nil {
// rollback
ctr.borrowed = oldBorrowed
ctr.seqNo = oldSeqNo
return err
}
return nil
}
func (ctr *fsContainer) GetSeqNo() (
seqNo SignatureSeqNo, lostSigs uint32, err Error) {
if !ctr.initialized {
err = errorf("Container is not initialized")
return
}
return ctr.seqNo, ctr.borrowed, nil
}
func (ctr *fsContainer) GetPrivateKey() ([]byte, Error) {
if !ctr.initialized {
return nil, errorf("Container is not initialized")
}
return ctr.privateKey, nil
}
func (ctr *fsContainer) closeCache() (err error) {
ctr.cacheInitialized = false
if ctr.cacheBufLut != nil {
for _, buf := range ctr.cacheBufLut {
if err2 := buf.mmap.Unmap(); err2 != nil {
err = multierror.Append(err, wrapErrorf(err2,
"Failed to unmap cached subtree"))
}
}
ctr.cacheBufLut = nil
}
if ctr.cacheFile != nil {
if err2 := ctr.cacheFile.Close(); err2 != nil {
err = multierror.Append(err, wrapErrorf(err2,
"Failed to close cache file"))
}
ctr.cacheFile = nil
}
return
}
func (ctr *fsContainer) Close() Error {
var err error
if err2 := ctr.closeCache(); err2 != nil {
err = multierror.Append(err, wrapErrorf(err2,
"Could not close cache"))
}
if err2 := ctr.flock.Unlock(); err2 != nil {
err = multierror.Append(err, wrapErrorf(err2,
"Could not release file lock"))
}
ctr.closed = true
ctr.initialized = false
if err != nil {
return wrapErrorf(err, "")
}
return nil
}