func (kx *KeyExchange) exchange2() ([]byte, error) {
reply, err := kx.meetingPlace.Exchange(kx.Log, kx.meeting2[:], kx.message2[:], kx.ShutdownChan)
if err != nil {
return nil, err
}
var nonce [24]byte
if len(reply) < len(nonce) {
return nil, errors.New("panda: meeting point reply too small")
}
if kx.sharedKey[0] == 0 && kx.sharedKey[1] == 0 {
panic("here")
}
copy(nonce[:], reply)
message, ok := secretbox.Open(nil, reply[24:], &nonce, &kx.sharedKey)
if !ok {
return nil, errors.New("panda: peer's message cannot be authenticated")
}
if len(message) < 4 {
return nil, errors.New("panda: peer's message is invalid")
}
l := binary.LittleEndian.Uint32(message)
message = message[4:]
if l > uint32(len(message)) {
return nil, errors.New("panda: peer's message is truncated")
}
message = message[:int(l)]
return message, nil
}
// OpenWithKey is the same as Open, but a different key can be passed in.
func (s *Service) OpenWithKey(e *SealedBytes, secretKey *[SecretKeyLength]byte) (byt []byte, err error) {
// once function is complete, check if we are returning err or not.
// if we are, return emit a failure metric, if not a success metric.
defer func() {
if err == nil {
s.metricsClient.Inc("success", 1, 1)
} else {
s.metricsClient.Inc("failure", 1, 1)
}
}()
// check that we either initialized with a key or one was passed in
if secretKey == nil {
return nil, fmt.Errorf("secret key is nil")
}
// convert nonce to an array
nonce, err := nonceSliceToArray(e.Nonce)
if err != nil {
return nil, err
}
// decrypt
var decrypted []byte
decrypted, ok := secretbox.Open(decrypted, e.Ciphertext, nonce, secretKey)
if !ok {
return nil, fmt.Errorf("unable to decrypt message")
}
return decrypted, nil
}
func (nd *NaClDecryptor) decrypt(buf []byte) ([]byte, bool) {
seqNoAndDF := binary.BigEndian.Uint64(buf[:8])
df := (seqNoAndDF & (1 << 63)) != 0
seqNo := seqNoAndDF & ((1 << 63) - 1)
var di *NaClDecryptorInstance
if df {
di = nd.instanceDF
} else {
di = nd.instance
}
binary.BigEndian.PutUint64(di.nonce[16:24], seqNoAndDF)
result, success := secretbox.Open(nil, buf[8:], &di.nonce, nd.sessionKey)
if !success {
return nil, false
}
// Drop duplicates. We do this *after* decryption since we must
// not advance our state unless decryption succeeded. Doing so
// would open an easy attack vector where an adversary could
// inject a packet with a sequence number of (1 << 63) - 1,
// causing all subsequent genuine packets to get dropped.
offset, usedOffsets := di.advanceState(seqNo)
if usedOffsets == nil || usedOffsets.Contains(offset) {
// We have detected a possible replay attack, but it is
// possible we may have just received a very old packet, or
// duplication may have occurred in the network. So let's just
// drop the packet silently.
return nil, true
}
usedOffsets.Add(offset)
return result, success
}
func (receiver *EncryptedTCPReceiver) Decode(msg []byte) ([]byte, error) {
decodedMsg, success := secretbox.Open(nil, msg, &receiver.state.nonce, receiver.state.sessionKey)
if !success {
return nil, fmt.Errorf("Unable to decrypt TCP msg")
}
receiver.state.advance()
return decodedMsg, nil
}
// decrypt extracts the nonce from the ciphertext, and attempts to
// decrypt with NaCl's secretbox.
func decrypt(key *[keySize]byte, in []byte) ([]byte, bool) {
if len(in) < nonceSize {
return nil, false
}
var nonce [nonceSize]byte
copy(nonce[:], in)
return secretbox.Open(nil, in[nonceSize:], &nonce, key)
}
// trySavedKeys tries to decrypt ciphertext using keys saved for missing messages.
func (r *Ratchet) trySavedKeys(ciphertext []byte) ([]byte, error) {
if len(ciphertext) < sealedHeaderSize {
return nil, errors.New("ratchet: header too small to be valid")
}
sealedHeader := ciphertext[:sealedHeaderSize]
var nonce [24]byte
copy(nonce[:], sealedHeader)
sealedHeader = sealedHeader[len(nonce):]
for headerKey, messageKeys := range r.saved {
header, ok := secretbox.Open(nil, sealedHeader, &nonce, &headerKey)
if !ok {
continue
}
if len(header) != headerSize {
continue
}
msgNum := binary.LittleEndian.Uint32(header[:4])
msgKey, ok := messageKeys[msgNum]
if !ok {
// This is a fairly common case: the message key might
// not have been saved because it's the next message
// key.
return nil, nil
}
sealedMessage := ciphertext[sealedHeaderSize:]
copy(nonce[:], header[nonceInHeaderOffset:])
msg, ok := secretbox.Open(nil, sealedMessage, &nonce, &msgKey.key)
if !ok {
return nil, errors.New("ratchet: corrupt message")
}
delete(messageKeys, msgNum)
if len(messageKeys) == 0 {
delete(r.saved, headerKey)
}
return msg, nil
}
return nil, nil
}
func (c *Conn) Read(out []byte) (n int, err error) {
if len(c.readPending) > 0 {
n = copy(out, c.readPending)
c.readPending = c.readPending[n:]
return
}
if c.readBuffer == nil {
c.readBuffer = make([]byte, blockSize+2)
}
if _, err := io.ReadFull(c.conn, c.readBuffer[:2]); err != nil {
return 0, err
}
n = int(c.readBuffer[0]) | int(c.readBuffer[1])<<8
if n > len(c.readBuffer) {
return 0, errors.New("transport: peer's message too large for Read")
}
if _, err := io.ReadFull(c.conn, c.readBuffer[:n]); err != nil {
return 0, err
}
var ok bool
if len(out) >= n-secretbox.Overhead {
// We can decrypt directly into the output buffer.
out, ok = secretbox.Open(out[:0], c.readBuffer[:n], &c.readSequence, &c.readKey)
n = len(out)
} else {
// We need to decrypt into a side buffer and copy a prefix of
// the result into the caller's buffer.
c.decryptBuffer, ok = secretbox.Open(c.decryptBuffer[:0], c.readBuffer[:n], &c.readSequence, &c.readKey)
n = copy(out, c.decryptBuffer)
c.readPending = c.decryptBuffer[n:]
}
incSequence(&c.readSequence)
if !ok {
c.readPending = c.readPending[:0]
return 0, errors.New("transport: bad MAC")
}
return
}
func (c *Conn) decrypt(data []byte) ([]byte, error) {
if !c.readKeyValid {
return data, nil
}
decrypted, ok := secretbox.Open(nil, data, &c.readSequence, &c.readKey)
incSequence(&c.readSequence)
if !ok {
return nil, errors.New("transport: bad MAC")
}
return decrypted, nil
}
func decrypt(key, ciphertext []byte) ([]byte, error) {
if len(ciphertext) < nonceLen+secretbox.Overhead {
return nil, fmt.Errorf("message too short")
}
var nonce [nonceLen]byte
copy(nonce[:], ciphertext)
ciphertext = ciphertext[nonceLen:]
text, ok := secretbox.Open(nil, ciphertext, &nonce, makeKey(key))
if !ok {
return nil, fmt.Errorf("decryption failure")
}
return text, nil
}
// Decrypt decrypts a message using XSalsa20-Poly1305 and outputs it to dst.
// Returns false if decryption failed (authentication tag mismatch).
func (sb *secretBoxMode) Decrypt(dst []byte, src []byte, nonce []byte) bool {
if len(src) <= sb.Overhead() {
panic("cryptstate: bad src")
}
if len(nonce) != 24 {
panic("cryptstate: bad nonce length")
}
noncePtr := (*[24]byte)(unsafe.Pointer(&nonce[0]))
_, ok := secretbox.Open(dst[0:0], src, noncePtr, &sb.key)
return ok
}
func DecryptPrefixNonce(ciphertxt []byte, secret *[32]byte) ([]byte, bool) {
if len(ciphertxt) < secretbox.Overhead+24 {
return nil, false
}
// There is no way to nicely convert from a slice to an
// array. So have to used the following loop.
var nonce [24]byte
for idx, e := range ciphertxt[0:24] {
nonce[idx] = e
}
ciphertxt = ciphertxt[24:]
return secretbox.Open(nil, ciphertxt, &nonce, secret)
}
// TODO : consider caching the last deciphered chunk
func (this *CipherReaderAt) ReadAt(p []byte, off int64) (n int, err error) {
log.Printf("ReadAt len(p):%v, off:%v\n", len(p), off)
// read Nonce if not yet read
if this.Nonce == nil {
this.Nonce = &[24]byte{}
_, err := this.Reader.ReadAt(this.Nonce[:], 0)
if err != nil {
return 0, err
}
}
// ...
for len(p) > 0 {
chunkIndex := off / (this.ChunkSize - secretbox.Overhead)
chunkStart := chunkIndex * this.ChunkSize
offChunk := off - chunkIndex*(this.ChunkSize-secretbox.Overhead)
log.Printf(" - chunkIndex: %v, chunkStart: %v, offChunk: %v\n", chunkIndex, chunkStart, offChunk)
// compute nonce, basically a base 256 addition operation
var nonce [24]byte
copy(nonce[:], this.Nonce[:])
{
ci := chunkIndex // copy
i := 0
carry := int16(0)
for ci > 0 || carry > 0 {
sum := int16(ci % 256)
sum += int16(nonce[i])
sum += int16(carry)
nonce[i] = byte(sum % 256)
carry = int16(sum >> 8)
ci >>= 8
i++
}
log.Printf(" - nonce: %v", nonce)
}
numRead, err := this.Reader.ReadAt(this.Chunk, 24+chunkStart)
if err != nil && err != io.EOF {
return n, err
}
openedChunk, ok := secretbox.Open(nil, this.Chunk[:numRead], &nonce, this.Key)
//fmt.Println(colors.Cyan("nonce:", nonce, " key:", this.Key, " numRead:", numRead))
if !ok {
return n, errors.New(fmt.Sprintf("Failed to decipher chunk %v", chunkIndex))
}
copied := copy(p, openedChunk[offChunk:])
p = p[copied:]
n += copied
off += int64(copied)
}
return n, nil
}
func (s *Convergent) Get(key []byte) ([]byte, error) {
boxedkey := s.computeBoxedKey(key)
box, err := s.untrusted.Get(boxedkey)
if err != nil {
return nil, err
}
nonce := s.makeNonce(key)
plain, ok := secretbox.Open(nil, box, nonce, s.secret)
if !ok {
return nil, Corrupt{Key: key}
}
return plain, nil
}
// decrypt extracts the nonce from the ciphertext, and attempts to
// decrypt with NaCl's secretbox.
func decrypt(key *[keySize]byte, message []byte) ([]byte, error) {
if len(message) < (nonceSize + secretbox.Overhead) {
return nil, ErrDecrypt
}
var nonce [nonceSize]byte
copy(nonce[:], message[:nonceSize])
out, ok := secretbox.Open(nil, message[nonceSize:], &nonce, key)
if !ok {
return nil, ErrDecrypt
}
return out, nil
}
func unbox(key *[32]byte, body []byte) ([]byte, error) {
var nonce [24]byte
if len(body) < len(nonce)+secretbox.Overhead+2 {
return nil, errors.New("panda: reply from server is too short to be valid")
}
copy(nonce[:], body)
unsealed, ok := secretbox.Open(nil, body[len(nonce):], &nonce, key)
if !ok {
return nil, errors.New("panda: failed to authenticate reply from server")
}
l := int(unsealed[0]) | int(unsealed[1])<<8
unsealed = unsealed[2:]
if l > len(unsealed) {
return nil, errors.New("panda: corrupt but authentic message found")
}
return unsealed[:l], nil
}
// importTombFile decrypts a file with the given path, using a hex-encoded key
// and loads the client state from the result.
func (c *client) importTombFile(stateFile *disk.StateFile, keyHex, path string) error {
keyBytes, err := hex.DecodeString(keyHex)
if err != nil {
return err
}
var key [32]byte
var nonce [24]byte
if len(keyBytes) != len(key) {
return fmt.Errorf("Incorrect key length: %d (want %d)", len(keyBytes), len(key))
}
copy(key[:], keyBytes)
tombBytes, err := ioutil.ReadFile(path)
if err != nil {
return err
}
plaintext, ok := secretbox.Open(nil, tombBytes, &nonce, &key)
if !ok {
return errors.New("Incorrect key")
}
c.stateLock, err = stateFile.Lock(true /* create */)
if c.stateLock == nil && err == nil {
return errors.New("Output statefile is locked.")
}
if err != nil {
return err
}
writerChan := make(chan disk.NewState)
writerDone := make(chan struct{})
go stateFile.StartWriter(writerChan, writerDone)
writerChan <- disk.NewState{State: plaintext}
close(writerChan)
<-writerDone
return nil
}
func (m *secretboxMode) Decrypt(encrypted []byte) ([]byte, bool) {
var opened []byte
var nonce [24]byte
if len(encrypted) < 24 {
log.Printf("secretbox: Not good: len (%d) < 24\n", len(encrypted))
return nil, false
}
for i := 0; i < 24; i++ {
nonce[i] = encrypted[len(encrypted)-24+i]
}
data := encrypted[:len(encrypted)-24]
opened, ok := secretbox.Open(opened[:0], data, &nonce, &m.key)
if !ok {
log.Printf("secretbox: Not good: Open() returned false\n")
}
return opened, ok
}
func (c *client) loadState(b []byte, key *[32]byte) error {
if len(b) < sCryptSaltLen+24*smearedCopies {
return errors.New("state file is too small to be valid")
}
b = b[sCryptSaltLen:]
var nonce [24]byte
for i := 0; i < smearedCopies; i++ {
for j := 0; j < 24; j++ {
nonce[j] ^= b[24*i+j]
}
}
b = b[24*smearedCopies:]
plaintext, ok := secretbox.Open(nil, b, &nonce, key)
if !ok {
return badPasswordError
}
if len(plaintext) < 4 {
return errors.New("state file corrupt")
}
length := binary.LittleEndian.Uint32(plaintext[:4])
plaintext = plaintext[4:]
if length > 1<<31 || length > uint32(len(plaintext)) {
return errors.New("state file corrupt")
}
plaintext = plaintext[:int(length)]
var state protos.State
if err := proto.Unmarshal(plaintext, &state); err != nil {
return err
}
if err := c.unmarshal(&state); err != nil {
return err
}
return nil
}
func loadOldState(b []byte, key *[32]byte) (*State, error) {
const (
SCryptSaltLen = 32
smearedCopies = 32768 / 24
)
if len(b) < SCryptSaltLen+24*smearedCopies {
return nil, errors.New("state file is too small to be valid")
}
var nonce [24]byte
for i := 0; i < smearedCopies; i++ {
for j := 0; j < 24; j++ {
nonce[j] ^= b[24*i+j]
}
}
b = b[24*smearedCopies:]
plaintext, ok := secretbox.Open(nil, b, &nonce, key)
if !ok {
return nil, BadPasswordError
}
if len(plaintext) < 4 {
return nil, errors.New("state file corrupt")
}
length := binary.LittleEndian.Uint32(plaintext[:4])
plaintext = plaintext[4:]
if length > 1<<31 || length > uint32(len(plaintext)) {
return nil, errors.New("state file corrupt")
}
plaintext = plaintext[:int(length)]
var state State
if err := proto.Unmarshal(plaintext, &state); err != nil {
return nil, err
}
return &state, nil
}
func (s *httpService) getBackendSticky(req *http.Request) (*httputil.ClientConn, *http.Cookie) {
cookie, err := req.Cookie(stickyCookie)
if err != nil {
return s.getNewBackendSticky()
}
data, err := base64.StdEncoding.DecodeString(cookie.Value)
if err != nil {
return s.getNewBackendSticky()
}
var nonce [24]byte
if len(data) < len(nonce) {
return s.getNewBackendSticky()
}
copy(nonce[:], data)
res, ok := secretbox.Open(nil, data[len(nonce):], &nonce, s.cookieKey)
if !ok {
return s.getNewBackendSticky()
}
addr := string(res)
ok = false
for _, a := range s.ss.Addrs() {
if a == addr {
ok = true
break
}
}
if !ok {
return s.getNewBackendSticky()
}
backend, err := net.Dial("tcp", string(addr))
if err != nil {
return s.getNewBackendSticky()
}
return httputil.NewClientConn(backend, nil), nil
}
func main() {
runtime.GOMAXPROCS(2)
flag.Parse()
if len(*secret) == 0 {
fmt.Fprintf(os.Stderr, "The shared secret must be given as --secret\n")
os.Exit(2)
}
if len(*keyFile) == 0 {
fmt.Fprintf(os.Stderr, "The path to a find containing the public key material to exchange must be given as --key-file\n")
os.Exit(2)
}
pubKeyBytes, err := ioutil.ReadFile(*keyFile)
if err != nil {
fmt.Fprintf(os.Stderr, "Failed to read key file: %s\n", err)
os.Exit(2)
}
const maxBody = 4096
if limit := maxBody - 24 - secretbox.Overhead; len(pubKeyBytes) > limit {
fmt.Fprintf(os.Stderr, "--key-file is too large (%d bytes of a maximum of %d)\n", len(pubKeyBytes), limit)
os.Exit(2)
}
// Run scrypt on a goroutine so that we can overlap it with the network
// delay.
keyChan := make(chan []byte)
go deriveKey(keyChan, *secret)
var dialer proxy.Dialer
dialer = proxy.Direct
if len(*torProxy) > 0 {
fmt.Fprintf(os.Stderr, "Using SOCKS5 proxy at %s\n", *torProxy)
dialer, err = proxy.SOCKS5("tcp", *torProxy, nil, dialer)
if err != nil {
panic(err)
}
}
fmt.Fprintf(os.Stderr, "Starting TCP connection to %s\n", *server)
rawConn, err := dialer.Dial("tcp", *server)
if err != nil {
fmt.Fprintf(os.Stderr, "Failed to connect to server: %s\n", err)
os.Exit(2)
}
var conn net.Conn
if *useTLS {
hostname, _, err := net.SplitHostPort(*server)
if err != nil {
fmt.Fprintf(os.Stderr, "Failed to split %s into host and post: %s\n", *server, err)
os.Exit(2)
}
tlsConn := tls.Client(rawConn, &tls.Config{
ServerName: hostname,
})
fmt.Fprintf(os.Stderr, "Starting TLS handshake\n")
if err := tlsConn.Handshake(); err != nil {
rawConn.Close()
fmt.Fprintf(os.Stderr, "TLS handshake failed: %s\n", err)
os.Exit(2)
}
conn = tlsConn
} else {
conn = rawConn
}
defer conn.Close()
var keySlice []byte
select {
case keySlice = <-keyChan:
default:
fmt.Fprintf(os.Stderr, "Waiting for key derivation to complete. This may take some time.\n")
keySlice = <-keyChan
}
var key [32]byte
copy(key[:], keySlice)
mac := hmac.New(sha256.New, key[:])
mac.Write(pubKeyBytes)
nonceSlice := mac.Sum(nil)
var nonce [24]byte
copy(nonce[:], nonceSlice)
box := make([]byte, len(nonce)+secretbox.Overhead+len(pubKeyBytes))
copy(box, nonce[:])
secretbox.Seal(box[len(nonce):len(nonce)], pubKeyBytes, &nonce, &key)
h := sha256.New()
h.Write(key[:])
tag := h.Sum(nil)
body := bytes.NewReader(box)
request, err := http.NewRequest("POST", "http://"+*server+"/exchange/"+hex.EncodeToString(tag), body)
if err != nil {
panic(err)
}
request.ContentLength = int64(len(box))
request.Header.Add("Content-Type", "application/octet-stream")
request.Write(conn)
fmt.Fprintf(os.Stderr, "Request sent. Waiting for HTTP reply\n")
replyReader := bufio.NewReader(conn)
response, err := http.ReadResponse(replyReader, request)
if err != nil {
fmt.Fprintf(os.Stderr, "Error reading reply from server: %s\n", err)
os.Exit(2)
}
switch response.StatusCode {
case 409:
fmt.Fprintf(os.Stderr, "The transaction failed because this key has been used recently by two other parties.\n")
os.Exit(2)
case 204:
fmt.Fprintf(os.Stderr, "Material submitted, but the other party has yet to start the process. Try again later with the same arguments.\n")
os.Exit(1)
case 200:
r := &io.LimitedReader{R: response.Body, N: maxBody + 1}
body, err := ioutil.ReadAll(r)
if err != nil {
fmt.Fprintf(os.Stderr, "Error reading from server: %s\n", err)
os.Exit(2)
}
if len(body) > maxBody {
fmt.Fprintf(os.Stderr, "Reply from server is too large\n")
os.Exit(2)
}
if len(body) < len(nonce)+secretbox.Overhead {
fmt.Fprintf(os.Stderr, "Reply from server is too short to be valid: %x\n", body)
os.Exit(2)
}
copy(nonce[:], body)
unsealed, ok := secretbox.Open(nil, body[len(nonce):], &nonce, &key)
if !ok {
fmt.Fprintf(os.Stderr, "Failed to authenticate reply from server\n")
os.Exit(2)
}
os.Stdout.Write(unsealed)
default:
fmt.Fprintf(os.Stderr, "HTTP error from server: %s\n", response.Status)
io.Copy(os.Stderr, response.Body)
os.Exit(2)
}
}
func saveDecrypted(c chan interface{}, outPath string, id uint64, in *os.File, detachment *pond.Message_Detachment, killChan chan bool) error {
out, err := os.OpenFile(outPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
if err != nil {
return errors.New("failed to open output: " + err.Error())
}
defer out.Close()
var key [32]byte
var nonce [24]byte
blockSize := *detachment.ChunkSize + secretbox.Overhead
if blockSize > 1<<20 {
return errors.New("chunk size too large")
}
copy(key[:], detachment.Key)
var bytesIn, bytesOut uint64
buf := make([]byte, blockSize)
var decrypted []byte
var lastUpdate time.Time
BlockLoop:
for {
n, err := io.ReadFull(in, buf)
switch err {
case nil:
break
case io.ErrUnexpectedEOF, io.EOF:
break BlockLoop
default:
return errors.New("failed to read from source: " + err.Error())
}
bytesIn += uint64(n)
var ok bool
decrypted, ok = secretbox.Open(decrypted[:0], buf, &nonce, &key)
if !ok {
os.Remove(outPath)
return errors.New("input corrupt")
}
if bytesOut != *detachment.Size {
if n := bytesOut + uint64(len(decrypted)); n > *detachment.Size {
decrypted = decrypted[:*detachment.Size-bytesOut]
}
bytesOut += uint64(len(decrypted))
if _, err := out.Write(decrypted); err != nil {
return errors.New("failed to write to destination: " + err.Error())
}
}
if bytesIn > *detachment.PaddedSize {
// This means that we downloaded more bytes than we
// expected.
break
}
incNonce(&nonce)
now := time.Now()
if lastUpdate.IsZero() || now.Sub(lastUpdate) > 500*time.Millisecond {
lastUpdate = now
select {
case c <- DetachmentProgress{
id: id,
done: bytesIn,
total: *detachment.PaddedSize,
}:
break
default:
}
}
select {
case <-killChan:
os.Remove(outPath)
return backgroundCanceledError
default:
break
}
}
if bytesIn != *detachment.PaddedSize {
return errors.New("input truncated")
}
return nil
}
// If valid == true, pb[176:] is replaced by the plaintext contents of
// the Initiate C'->S' box.
func (s *server) checkInitiate(pb []byte) (serverShortTermKey []byte, domain string, valid bool) {
valid = false
if len(pb) < 544 || !bytes.Equal(pb[:8], initiateMagic) {
return
}
// Try to open the cookie.
var nonce [24]byte
copy(nonce[:], minuteNoncePrefix)
copy(nonce[len(minuteNoncePrefix):], pb[72:72+16])
var cookie [64]byte
if _, ok := secretbox.Open(cookie[:0], pb[88:168], &nonce, &s.minuteKey); !ok {
if _, ok = secretbox.Open(cookie[:0], pb[88:168], &nonce, &s.prevMinuteKey); !ok {
return
}
}
// Check that the cookie and client match
if !bytes.Equal(cookie[:32], pb[40:40+32]) {
return
}
// Extract server short-term secret key
var serverKey [32]byte
serverShortTermKey = serverKey[:]
copy(serverShortTermKey, cookie[32:])
// Open the Initiate box using both short-term secret keys.
copy(nonce[:], initiateNoncePrefix)
copy(nonce[len(initiateNoncePrefix):], pb[168:168+8])
var clientShortTermKey [32]byte
copy(clientShortTermKey[:], pb[40:40+32])
initiate := make([]byte, len(pb[176:])-box.Overhead)
if _, ok := box.Open(initiate[:0], pb[176:], &nonce, &clientShortTermKey, &serverKey); !ok {
return
}
if domain = domainToString(initiate[96 : 96+256]); domain == "" {
return
}
// Extract client long-term public key and check the vouch
// subpacket.
var clientLongTermKey [32]byte
copy(clientLongTermKey[:], initiate[:32])
copy(nonce[:], vouchNoncePrefix)
copy(nonce[len(vouchNoncePrefix):], initiate[32:32+16])
var vouch [32]byte
if _, ok := box.Open(vouch[:0], initiate[48:48+48], &nonce, &clientLongTermKey, &s.longTermSecretKey); !ok {
return
}
if !bytes.Equal(vouch[:], pb[40:40+32]) {
return
}
// The Initiate packet is valid, replace the encrypted box with
// the plaintext and return.
copy(pb[176:], initiate)
for i := len(pb) - box.Overhead; i < len(pb); i++ {
pb[i] = 0
}
valid = true
return
}
func (r *Ratchet) Decrypt(ciphertext []byte) ([]byte, error) {
msg, err := r.trySavedKeys(ciphertext)
if err != nil || msg != nil {
return msg, err
}
sealedHeader := ciphertext[:sealedHeaderSize]
sealedMessage := ciphertext[sealedHeaderSize:]
var nonce [24]byte
copy(nonce[:], sealedHeader)
sealedHeader = sealedHeader[len(nonce):]
header, ok := secretbox.Open(nil, sealedHeader, &nonce, &r.recvHeaderKey)
ok = ok && !isZeroKey(&r.recvHeaderKey)
if ok {
if len(header) != headerSize {
return nil, errors.New("ratchet: incorrect header size")
}
messageNum := binary.LittleEndian.Uint32(header[:4])
provisionalChainKey, messageKey, savedKeys, err := r.saveKeys(&r.recvHeaderKey, &r.recvChainKey, messageNum, r.recvCount)
if err != nil {
return nil, err
}
copy(nonce[:], header[nonceInHeaderOffset:])
msg, ok := secretbox.Open(nil, sealedMessage, &nonce, &messageKey)
if !ok {
return nil, errors.New("ratchet: corrupt message")
}
copy(r.recvChainKey[:], provisionalChainKey[:])
r.mergeSavedKeys(savedKeys)
r.recvCount = messageNum + 1
return msg, nil
}
header, ok = secretbox.Open(nil, sealedHeader, &nonce, &r.nextRecvHeaderKey)
if !ok {
return nil, errors.New("ratchet: cannot decrypt")
}
if len(header) != headerSize {
return nil, errors.New("ratchet: incorrect header size")
}
if r.ratchet {
return nil, errors.New("ratchet: received message encrypted to next header key without ratchet flag set")
}
messageNum := binary.LittleEndian.Uint32(header[:4])
prevMessageCount := binary.LittleEndian.Uint32(header[4:8])
_, _, oldSavedKeys, err := r.saveKeys(&r.recvHeaderKey, &r.recvChainKey, prevMessageCount, r.recvCount)
if err != nil {
return nil, err
}
var dhPublic, sharedKey, rootKey, chainKey, keyMaterial [32]byte
copy(dhPublic[:], header[8:])
curve25519.ScalarMult(&sharedKey, &r.sendRatchetPrivate, &dhPublic)
sha := sha256.New()
sha.Write(rootKeyUpdateLabel)
sha.Write(r.rootKey[:])
sha.Write(sharedKey[:])
var rootKeyHMAC hash.Hash
if r.v2 {
sha.Sum(keyMaterial[:0])
rootKeyHMAC = hmac.New(sha256.New, keyMaterial[:])
deriveKey(&rootKey, rootKeyLabel, rootKeyHMAC)
} else {
sha.Sum(rootKey[:0])
rootKeyHMAC = hmac.New(sha256.New, rootKey[:])
}
deriveKey(&chainKey, chainKeyLabel, rootKeyHMAC)
provisionalChainKey, messageKey, savedKeys, err := r.saveKeys(&r.nextRecvHeaderKey, &chainKey, messageNum, 0)
if err != nil {
return nil, err
}
copy(nonce[:], header[nonceInHeaderOffset:])
msg, ok = secretbox.Open(nil, sealedMessage, &nonce, &messageKey)
if !ok {
return nil, errors.New("ratchet: corrupt message")
}
copy(r.rootKey[:], rootKey[:])
copy(r.recvChainKey[:], provisionalChainKey[:])
copy(r.recvHeaderKey[:], r.nextRecvHeaderKey[:])
deriveKey(&r.nextRecvHeaderKey, sendHeaderKeyLabel, rootKeyHMAC)
for i := range r.sendRatchetPrivate {
r.sendRatchetPrivate[i] = 0
}
copy(r.recvRatchetPublic[:], dhPublic[:])
r.recvCount = messageNum + 1
r.mergeSavedKeys(oldSavedKeys)
r.mergeSavedKeys(savedKeys)
r.ratchet = true
return msg, nil
}
func (sf *StateFile) Read(pw string) (*State, error) {
b, err := ioutil.ReadFile(sf.Path)
if err != nil {
return nil, err
}
if len(b) < len(headerMagic)+4 {
return nil, errors.New("state file is too small to be valid")
}
if !bytes.Equal(b[:len(headerMagic)], headerMagic[:]) {
sf.header.NoErasureStorage = proto.Bool(true)
if len(pw) > 0 {
sf.header.Scrypt = new(Header_SCrypt)
sf.header.KdfSalt = b[:32]
if err := sf.deriveKey(pw); err != nil {
return nil, err
}
}
b = b[32:]
state, err := sf.readOldStyle(b)
if err != nil {
return nil, err
}
return state, nil
}
b = b[len(headerMagic):]
headerLen := binary.LittleEndian.Uint32(b)
b = b[4:]
if headerLen > 1<<16 {
return nil, errors.New("state file corrupt")
}
if len(b) < int(headerLen) {
return nil, errors.New("state file truncated")
}
headerBytes := b[:int(headerLen)]
b = b[int(headerLen):]
if err := proto.Unmarshal(headerBytes, &sf.header); err != nil {
return nil, err
}
if len(pw) > 0 {
if err := sf.deriveKey(pw); err != nil {
return nil, err
}
}
if !sf.header.GetNoErasureStorage() {
for _, erasureMethod := range erasureRegistry {
sf.Erasure = erasureMethod(&sf.header)
if sf.Erasure != nil {
break
}
}
if sf.Erasure == nil {
return nil, errors.New("unknown erasure storage method")
}
mask, err := sf.Erasure.Read(&sf.key)
if err != nil {
return nil, err
}
copy(sf.mask[:], mask[:])
}
smearedCopies := int(sf.header.GetNonceSmearCopies())
if len(b) < 24*smearedCopies {
return nil, errors.New("state file truncated")
}
var nonce [24]byte
for i := 0; i < smearedCopies; i++ {
for j := 0; j < 24; j++ {
nonce[j] ^= b[24*i+j]
}
}
b = b[24*smearedCopies:]
var effectiveKey [kdfKeyLen]byte
for i := range effectiveKey {
effectiveKey[i] = sf.mask[i] ^ sf.key[i]
}
plaintext, ok := secretbox.Open(nil, b, &nonce, &effectiveKey)
if !ok {
return nil, BadPasswordError
}
if len(plaintext) < 4 {
return nil, errors.New("state file corrupt")
}
length := binary.LittleEndian.Uint32(plaintext[:4])
plaintext = plaintext[4:]
if length > 1<<31 || length > uint32(len(plaintext)) {
return nil, errors.New("state file corrupt")
}
plaintext = plaintext[:int(length)]
var state State
if err := proto.Unmarshal(plaintext, &state); err != nil {
return nil, err
}
return &state, nil
}
// Open authenticates and decrypts a box produced by Seal and appends the
// message to out, which must not overlap box. The output will be Overhead
// bytes smaller than box.
func Open(out, box []byte, nonce *[24]byte, peersPublicKey, privateKey *[32]byte) ([]byte, bool) {
var sharedKey [32]byte
Precompute(&sharedKey, peersPublicKey, privateKey)
return secretbox.Open(out, box, nonce, &sharedKey)
}
func (nd *NaClDecryptor) decrypt(buf []byte) ([]byte, error) {
offset := binary.BigEndian.Uint16(buf[:2])
df := (offset & (1 << 15)) != 0
offsetNoFlags := offset & ((1 << 15) - 1)
var decState *NaClDecryptorInstance
if df {
decState = nd.instanceDF
} else {
decState = nd.instance
}
var nonce *[24]byte
var usedOffsets *bit.Set
var ok bool
if decState.nonce == nil {
if offsetNoFlags > (1 << 13) {
// offset is already beyond the first quarter and it's the
// first thing we've seen?! I don't think so.
return nil, fmt.Errorf("Unexpected offset when decrypting UDP packet")
}
decState.nonce, ok = <-decState.nonceChan
if !ok {
return nil, fmt.Errorf("Nonce chan closed")
}
nonce = decState.nonce
usedOffsets = decState.usedOffsets
decState.highestOffsetSeen = offsetNoFlags
} else {
highestOffsetSeen := decState.highestOffsetSeen
if offsetNoFlags < (1<<13) && highestOffsetSeen > ((1<<14)+(1<<13)) &&
(highestOffsetSeen-offsetNoFlags) > ((1<<14)+(1<<13)) {
// offset is in the first quarter, highestOffsetSeen is in
// the top quarter and under a quarter behind us. We
// interpret this as we need to move to the next nonce
decState.previousUsedOffsets = decState.usedOffsets
decState.usedOffsets = bit.New()
decState.previousNonce = decState.nonce
decState.nonce, ok = <-decState.nonceChan
if !ok {
return nil, fmt.Errorf("Nonce chan closed")
}
decState.highestOffsetSeen = offsetNoFlags
nonce = decState.nonce
usedOffsets = decState.usedOffsets
} else if offsetNoFlags > highestOffsetSeen &&
(offsetNoFlags-highestOffsetSeen) < (1<<13) {
// offset is under a quarter above highestOffsetSeen. This
// is ok - maybe some packet loss
decState.highestOffsetSeen = offsetNoFlags
nonce = decState.nonce
usedOffsets = decState.usedOffsets
} else if offsetNoFlags <= highestOffsetSeen &&
(highestOffsetSeen-offsetNoFlags) < (1<<13) {
// offset is within a quarter of the highest we've
// seen. This is ok - just assuming some out-of-order
// delivery.
nonce = decState.nonce
usedOffsets = decState.usedOffsets
} else if highestOffsetSeen < (1<<13) && offsetNoFlags > ((1<<14)+(1<<13)) &&
(offsetNoFlags-highestOffsetSeen) > ((1<<14)+(1<<13)) {
// offset is in the last quarter, highestOffsetSeen is in
// the first quarter, and offset is under a quarter behind
// us. This is ok - as above, just some out of order. But
// here it means we're dealing with the previous nonce
nonce = decState.previousNonce
usedOffsets = decState.previousUsedOffsets
} else {
return nil, fmt.Errorf("Unexpected offset when decrypting UDP packet")
}
}
offsetNoFlagsInt := int(offsetNoFlags)
if usedOffsets.Contains(offsetNoFlagsInt) {
return nil, fmt.Errorf("Suspected replay attack detected when decrypting UDP packet")
}
SetNonceLow15Bits(nonce, offsetNoFlags)
result, success := secretbox.Open(nil, buf[2:], nonce, nd.conn.SessionKey)
if success {
usedOffsets.Add(offsetNoFlagsInt)
return result, nil
} else {
return nil, fmt.Errorf("Unable to decrypt msg via UDP: %v", buf)
}
}
// OpenAfterPrecomputation performs the same actions as Open, but takes a
// shared key as generated by Precompute.
func OpenAfterPrecomputation(out, box []byte, nonce *[24]byte, sharedKey *[32]byte) ([]byte, bool) {
return secretbox.Open(out, box, nonce, sharedKey)
}
func do(keyFile string) error {
contents, err := ioutil.ReadFile(os.Args[1])
if err != nil {
return err
}
var detachment pond.Message_Detachment
if err := proto.Unmarshal(contents, &detachment); err != nil {
return err
}
size := detachment.GetSize()
paddedSize := detachment.GetPaddedSize()
chunkSize := uint64(detachment.GetChunkSize())
blockSize := chunkSize + secretbox.Overhead
if blockSize > 1<<20 {
return errors.New("chunk size too large")
}
if paddedSize%blockSize != 0 {
return errors.New("padded size is not a multiple of the chunk size")
}
fmt.Fprintf(os.Stderr, `Pond decryption:
Original filename: %s
Size: %d
Padded size: %d
Chunk size: %d
`, sanitiseForTerminal(detachment.GetFilename()), size, paddedSize, chunkSize)
var key [32]byte
var nonce [24]byte
copy(key[:], detachment.Key)
var read, written uint64
buf := make([]byte, blockSize)
var decrypted []byte
for read < paddedSize {
if _, err := io.ReadFull(os.Stdin, buf); err != nil {
return err
}
read += uint64(len(buf))
var ok bool
decrypted, ok := secretbox.Open(decrypted[:0], buf, &nonce, &key)
if !ok {
return errors.New("decryption error")
}
incNonce(&nonce)
todo := size - written
if n := uint64(len(decrypted)); todo > n {
todo = n
}
if _, err := os.Stdout.Write(decrypted[:todo]); err != nil {
return err
}
written += todo
}
return nil
}