Merge pull request #2054 from tendermint/dev/secret_connection
secret connection update
This commit is contained in:
commit
bdab37a626
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@ -5,6 +5,7 @@ BREAKING CHANGES:
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- breaks serialization/signing of all messages with a timestamp
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- [abci] Removed Fee from ResponseDeliverTx and ResponseCheckTx
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- [tools] Removed `make ensure_deps` in favor of `make get_vendor_deps`
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- [p2p] Remove salsa and ripemd primitives, in favor of using chacha as a stream cipher, and hkdf
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FEATURES:
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- [tools] Added `make check_dep`
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@ -143,6 +143,7 @@
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".",
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"hcl/ast",
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"hcl/parser",
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"hcl/printer",
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"hcl/scanner",
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"hcl/strconv",
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"hcl/token",
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@ -538,6 +539,7 @@
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"github.com/tendermint/go-amino",
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"golang.org/x/crypto/bcrypt",
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"golang.org/x/crypto/chacha20poly1305",
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"golang.org/x/crypto/curve25519",
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"golang.org/x/crypto/hkdf",
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"golang.org/x/crypto/nacl/box",
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"golang.org/x/crypto/nacl/secretbox",
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@ -27,27 +27,24 @@ Both handshakes have configurable timeouts (they should complete quickly).
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### Authenticated Encryption Handshake
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Tendermint implements the Station-to-Station protocol
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using ED25519 keys for Diffie-Helman key-exchange and NACL SecretBox for encryption.
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using X25519 keys for Diffie-Helman key-exchange and chacha20poly1305 for encryption.
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It goes as follows:
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- generate an emphemeral ED25519 keypair
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- generate an ephemeral X25519 keypair
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- send the ephemeral public key to the peer
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- wait to receive the peer's ephemeral public key
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- compute the Diffie-Hellman shared secret using the peers ephemeral public key and our ephemeral private key
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- generate two nonces to use for encryption (sending and receiving) as follows:
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- sort the ephemeral public keys in ascending order and concatenate them
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- RIPEMD160 the result
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- append 4 empty bytes (extending the hash to 24-bytes)
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- the result is nonce1
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- flip the last bit of nonce1 to get nonce2
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- if we had the smaller ephemeral pubkey, use nonce1 for receiving, nonce2 for sending;
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else the opposite
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- all communications from now on are encrypted using the shared secret and the nonces, where each nonce
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increments by 2 every time it is used
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- generate two keys to use for encryption (sending and receiving) and a challenge for authentication as follows:
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- create a hkdf-sha256 instance with the key being the diffie hellman shared secret, and info parameter as
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`TENDERMINT_SECRET_CONNECTION_KEY_AND_CHALLENGE_GEN`
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- get 96 bytes of output from hkdf-sha256
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- if we had the smaller ephemeral pubkey, use the first 32 bytes for the key for receiving, the second 32 bytes for sending; else the opposite
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- use the last 32 bytes of output for the challenge
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- use a seperate nonce for receiving and sending. Both nonces start at 0, and should support the full 96 bit nonce range
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- all communications from now on are encrypted in 1024 byte frames,
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using the respective secret and nonce. Each nonce is incremented by one after each use.
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- we now have an encrypted channel, but still need to authenticate
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- generate a common challenge to sign:
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- SHA256 of the sorted (lowest first) and concatenated ephemeral pub keys
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- sign the common challenge with our persistent private key
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- send the go-wire encoded persistent pubkey and signature to the peer
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- sign the common challenge obtained from the hkdf with our persistent private key
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- send the amino encoded persistent pubkey and signature to the peer
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- wait to receive the persistent public key and signature from the peer
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- verify the signature on the challenge using the peer's persistent public key
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@ -1,9 +1,3 @@
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// Uses nacl's secret_box to encrypt a net.Conn.
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// It is (meant to be) an implementation of the STS protocol.
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// Note we do not (yet) assume that a remote peer's pubkey
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// is known ahead of time, and thus we are technically
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// still vulnerable to MITM. (TODO!)
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// See docs/sts-final.pdf for more info
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package conn
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import (
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@ -16,36 +10,45 @@ import (
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"net"
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"time"
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"golang.org/x/crypto/chacha20poly1305"
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"golang.org/x/crypto/curve25519"
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"golang.org/x/crypto/nacl/box"
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"golang.org/x/crypto/nacl/secretbox"
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"golang.org/x/crypto/ripemd160"
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"github.com/tendermint/tendermint/crypto"
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cmn "github.com/tendermint/tendermint/libs/common"
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"golang.org/x/crypto/hkdf"
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)
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// 4 + 1024 == 1028 total frame size
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const dataLenSize = 4
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const dataMaxSize = 1024
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const totalFrameSize = dataMaxSize + dataLenSize
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const sealedFrameSize = totalFrameSize + secretbox.Overhead
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const aeadSizeOverhead = 16 // overhead of poly 1305 authentication tag
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const aeadKeySize = chacha20poly1305.KeySize
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const aeadNonceSize = chacha20poly1305.NonceSize
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// Implements net.Conn
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// SecretConnection implements net.conn.
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// It is an implementation of the STS protocol.
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// Note we do not (yet) assume that a remote peer's pubkey
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// is known ahead of time, and thus we are technically
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// still vulnerable to MITM. (TODO!)
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// See docs/sts-final.pdf for more info
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type SecretConnection struct {
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conn io.ReadWriteCloser
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recvBuffer []byte
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recvNonce *[24]byte
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sendNonce *[24]byte
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recvNonce *[aeadNonceSize]byte
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sendNonce *[aeadNonceSize]byte
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recvSecret *[aeadKeySize]byte
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sendSecret *[aeadKeySize]byte
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remPubKey crypto.PubKey
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shrSecret *[32]byte // shared secret
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}
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// Performs handshake and returns a new authenticated SecretConnection.
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// Returns nil if error in handshake.
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// MakeSecretConnection performs handshake and returns a new authenticated
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// SecretConnection.
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// Returns nil if there is an error in handshake.
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// Caller should call conn.Close()
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// See docs/sts-final.pdf for more information.
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func MakeSecretConnection(conn io.ReadWriteCloser, locPrivKey crypto.PrivKey) (*SecretConnection, error) {
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locPubKey := locPrivKey.PubKey()
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// Generate ephemeral keys for perfect forward secrecy.
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@ -59,29 +62,27 @@ func MakeSecretConnection(conn io.ReadWriteCloser, locPrivKey crypto.PrivKey) (*
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return nil, err
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}
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// Compute common shared secret.
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shrSecret := computeSharedSecret(remEphPub, locEphPriv)
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// Sort by lexical order.
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loEphPub, hiEphPub := sort32(locEphPub, remEphPub)
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loEphPub, _ := sort32(locEphPub, remEphPub)
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// Check if the local ephemeral public key
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// was the least, lexicographically sorted.
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locIsLeast := bytes.Equal(locEphPub[:], loEphPub[:])
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// Generate nonces to use for secretbox.
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recvNonce, sendNonce := genNonces(loEphPub, hiEphPub, locIsLeast)
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// Compute common diffie hellman secret using X25519.
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dhSecret := computeDHSecret(remEphPub, locEphPriv)
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// Generate common challenge to sign.
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challenge := genChallenge(loEphPub, hiEphPub)
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// generate the secret used for receiving, sending, challenge via hkdf-sha2 on dhSecret
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recvSecret, sendSecret, challenge := deriveSecretAndChallenge(dhSecret, locIsLeast)
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// Construct SecretConnection.
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sc := &SecretConnection{
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conn: conn,
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recvBuffer: nil,
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recvNonce: recvNonce,
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sendNonce: sendNonce,
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shrSecret: shrSecret,
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recvNonce: new([aeadNonceSize]byte),
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sendNonce: new([aeadNonceSize]byte),
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recvSecret: recvSecret,
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sendSecret: sendSecret,
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}
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// Sign the challenge bytes for authentication.
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@ -92,6 +93,7 @@ func MakeSecretConnection(conn io.ReadWriteCloser, locPrivKey crypto.PrivKey) (*
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if err != nil {
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return nil, err
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}
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remPubKey, remSignature := authSigMsg.Key, authSigMsg.Sig
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if !remPubKey.VerifyBytes(challenge[:], remSignature) {
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return nil, errors.New("Challenge verification failed")
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@ -102,7 +104,7 @@ func MakeSecretConnection(conn io.ReadWriteCloser, locPrivKey crypto.PrivKey) (*
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return sc, nil
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}
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// Returns authenticated remote pubkey
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// RemotePubKey returns authenticated remote pubkey
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func (sc *SecretConnection) RemotePubKey() crypto.PubKey {
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return sc.remPubKey
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}
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@ -124,14 +126,17 @@ func (sc *SecretConnection) Write(data []byte) (n int, err error) {
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binary.BigEndian.PutUint32(frame, uint32(chunkLength))
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copy(frame[dataLenSize:], chunk)
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aead, err := chacha20poly1305.New(sc.sendSecret[:])
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if err != nil {
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return n, errors.New("Invalid SecretConnection Key")
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}
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// encrypt the frame
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var sealedFrame = make([]byte, sealedFrameSize)
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secretbox.Seal(sealedFrame[:0], frame, sc.sendNonce, sc.shrSecret)
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// fmt.Printf("secretbox.Seal(sealed:%X,sendNonce:%X,shrSecret:%X\n", sealedFrame, sc.sendNonce, sc.shrSecret)
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incr2Nonce(sc.sendNonce)
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var sealedFrame = make([]byte, aeadSizeOverhead+totalFrameSize)
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aead.Seal(sealedFrame[:0], sc.sendNonce[:], frame, nil)
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incrNonce(sc.sendNonce)
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// end encryption
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_, err := sc.conn.Write(sealedFrame)
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_, err = sc.conn.Write(sealedFrame)
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if err != nil {
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return n, err
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}
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@ -148,7 +153,11 @@ func (sc *SecretConnection) Read(data []byte) (n int, err error) {
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return
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}
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sealedFrame := make([]byte, sealedFrameSize)
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aead, err := chacha20poly1305.New(sc.recvSecret[:])
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if err != nil {
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return n, errors.New("Invalid SecretConnection Key")
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}
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sealedFrame := make([]byte, totalFrameSize+aeadSizeOverhead)
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_, err = io.ReadFull(sc.conn, sealedFrame)
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if err != nil {
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return
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@ -156,12 +165,11 @@ func (sc *SecretConnection) Read(data []byte) (n int, err error) {
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// decrypt the frame
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var frame = make([]byte, totalFrameSize)
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// fmt.Printf("secretbox.Open(sealed:%X,recvNonce:%X,shrSecret:%X\n", sealedFrame, sc.recvNonce, sc.shrSecret)
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_, ok := secretbox.Open(frame[:0], sealedFrame, sc.recvNonce, sc.shrSecret)
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if !ok {
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_, err = aead.Open(frame[:0], sc.recvNonce[:], sealedFrame, nil)
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if err != nil {
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return n, errors.New("Failed to decrypt SecretConnection")
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}
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incr2Nonce(sc.recvNonce)
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incrNonce(sc.recvNonce)
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// end decryption
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var chunkLength = binary.BigEndian.Uint32(frame) // read the first two bytes
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@ -176,6 +184,7 @@ func (sc *SecretConnection) Read(data []byte) (n int, err error) {
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}
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// Implements net.Conn
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// nolint
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func (sc *SecretConnection) Close() error { return sc.conn.Close() }
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func (sc *SecretConnection) LocalAddr() net.Addr { return sc.conn.(net.Conn).LocalAddr() }
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func (sc *SecretConnection) RemoteAddr() net.Addr { return sc.conn.(net.Conn).RemoteAddr() }
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@ -204,18 +213,16 @@ func shareEphPubKey(conn io.ReadWriteCloser, locEphPub *[32]byte) (remEphPub *[3
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var _, err1 = cdc.MarshalBinaryWriter(conn, locEphPub)
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if err1 != nil {
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return nil, err1, true // abort
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} else {
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return nil, nil, false
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}
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return nil, nil, false
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},
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func(_ int) (val interface{}, err error, abort bool) {
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var _remEphPub [32]byte
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var _, err2 = cdc.UnmarshalBinaryReader(conn, &_remEphPub, 1024*1024) // TODO
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if err2 != nil {
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return nil, err2, true // abort
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} else {
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return _remEphPub, nil, false
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}
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return _remEphPub, nil, false
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},
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)
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@ -230,9 +237,40 @@ func shareEphPubKey(conn io.ReadWriteCloser, locEphPub *[32]byte) (remEphPub *[3
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return &_remEphPub, nil
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}
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func computeSharedSecret(remPubKey, locPrivKey *[32]byte) (shrSecret *[32]byte) {
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shrSecret = new([32]byte)
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box.Precompute(shrSecret, remPubKey, locPrivKey)
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func deriveSecretAndChallenge(dhSecret *[32]byte, locIsLeast bool) (recvSecret, sendSecret *[aeadKeySize]byte, challenge *[32]byte) {
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hash := sha256.New
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hkdf := hkdf.New(hash, dhSecret[:], nil, []byte("TENDERMINT_SECRET_CONNECTION_KEY_AND_CHALLENGE_GEN"))
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// get enough data for 2 aead keys, and a 32 byte challenge
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res := new([2*aeadKeySize + 32]byte)
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_, err := io.ReadFull(hkdf, res[:])
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if err != nil {
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panic(err)
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}
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challenge = new([32]byte)
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recvSecret = new([aeadKeySize]byte)
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sendSecret = new([aeadKeySize]byte)
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// Use the last 32 bytes as the challenge
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copy(challenge[:], res[2*aeadKeySize:2*aeadKeySize+32])
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// bytes 0 through aeadKeySize - 1 are one aead key.
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// bytes aeadKeySize through 2*aeadKeySize -1 are another aead key.
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// which key corresponds to sending and receiving key depends on whether
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// the local key is less than the remote key.
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if locIsLeast {
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copy(recvSecret[:], res[0:aeadKeySize])
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copy(sendSecret[:], res[aeadKeySize:aeadKeySize*2])
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} else {
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copy(sendSecret[:], res[0:aeadKeySize])
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copy(recvSecret[:], res[aeadKeySize:aeadKeySize*2])
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}
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return
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}
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func computeDHSecret(remPubKey, locPrivKey *[32]byte) (shrKey *[32]byte) {
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shrKey = new([32]byte)
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curve25519.ScalarMult(shrKey, locPrivKey, remPubKey)
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return
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}
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@ -247,25 +285,6 @@ func sort32(foo, bar *[32]byte) (lo, hi *[32]byte) {
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return
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}
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func genNonces(loPubKey, hiPubKey *[32]byte, locIsLo bool) (recvNonce, sendNonce *[24]byte) {
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nonce1 := hash24(append(loPubKey[:], hiPubKey[:]...))
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nonce2 := new([24]byte)
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copy(nonce2[:], nonce1[:])
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nonce2[len(nonce2)-1] ^= 0x01
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if locIsLo {
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recvNonce = nonce1
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sendNonce = nonce2
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} else {
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recvNonce = nonce2
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sendNonce = nonce1
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}
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return
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}
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func genChallenge(loPubKey, hiPubKey *[32]byte) (challenge *[32]byte) {
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return hash32(append(loPubKey[:], hiPubKey[:]...))
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}
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func signChallenge(challenge *[32]byte, locPrivKey crypto.PrivKey) (signature crypto.Signature) {
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signature, err := locPrivKey.Sign(challenge[:])
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// TODO(ismail): let signChallenge return an error instead
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@ -288,18 +307,16 @@ func shareAuthSignature(sc *SecretConnection, pubKey crypto.PubKey, signature cr
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var _, err1 = cdc.MarshalBinaryWriter(sc, authSigMessage{pubKey, signature})
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if err1 != nil {
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return nil, err1, true // abort
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} else {
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return nil, nil, false
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}
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return nil, nil, false
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},
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func(_ int) (val interface{}, err error, abort bool) {
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var _recvMsg authSigMessage
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var _, err2 = cdc.UnmarshalBinaryReader(sc, &_recvMsg, 1024*1024) // TODO
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if err2 != nil {
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return nil, err2, true // abort
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} else {
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return _recvMsg, nil, false
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}
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return _recvMsg, nil, false
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},
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)
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@ -315,36 +332,11 @@ func shareAuthSignature(sc *SecretConnection, pubKey crypto.PubKey, signature cr
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//--------------------------------------------------------------------------------
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// sha256
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func hash32(input []byte) (res *[32]byte) {
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hasher := sha256.New()
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hasher.Write(input) // nolint: errcheck, gas
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resSlice := hasher.Sum(nil)
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res = new([32]byte)
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copy(res[:], resSlice)
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return
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}
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// We only fill in the first 20 bytes with ripemd160
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func hash24(input []byte) (res *[24]byte) {
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hasher := ripemd160.New()
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hasher.Write(input) // nolint: errcheck, gas
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resSlice := hasher.Sum(nil)
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res = new([24]byte)
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copy(res[:], resSlice)
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return
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}
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// increment nonce big-endian by 2 with wraparound.
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func incr2Nonce(nonce *[24]byte) {
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incrNonce(nonce)
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incrNonce(nonce)
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}
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// increment nonce big-endian by 1 with wraparound.
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func incrNonce(nonce *[24]byte) {
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for i := 23; 0 <= i; i-- {
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func incrNonce(nonce *[aeadNonceSize]byte) {
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for i := aeadNonceSize - 1; 0 <= i; i-- {
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nonce[i]++
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// if this byte wrapped around to zero, we need to increment the next byte
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if nonce[i] != 0 {
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return
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}
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