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106 lines
3.2 KiB
106 lines
3.2 KiB
// Package hkdfchacha20poly1305 creates an AEAD using hkdf, chacha20, and poly1305
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// When sealing and opening, the hkdf is used to obtain the nonce and subkey for
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// chacha20. Other than the change for the how the subkey and nonce for chacha
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// are obtained, this is the same as chacha20poly1305
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package hkdfchacha20poly1305
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import (
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"crypto/cipher"
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"crypto/sha256"
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"errors"
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"io"
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"golang.org/x/crypto/chacha20poly1305"
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"golang.org/x/crypto/hkdf"
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)
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// Implements crypto.AEAD
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type hkdfchacha20poly1305 struct {
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key [KeySize]byte
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}
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const (
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// KeySize is the size of the key used by this AEAD, in bytes.
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KeySize = 32
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// NonceSize is the size of the nonce used with this AEAD, in bytes.
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NonceSize = 24
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// TagSize is the size added from poly1305
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TagSize = 16
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// MaxPlaintextSize is the max size that can be passed into a single call of Seal
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MaxPlaintextSize = (1 << 38) - 64
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// MaxCiphertextSize is the max size that can be passed into a single call of Open,
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// this differs from plaintext size due to the tag
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MaxCiphertextSize = (1 << 38) - 48
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// HkdfInfo is the parameter used internally for Hkdf's info parameter.
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HkdfInfo = "TENDERMINT_SECRET_CONNECTION_FRAME_KEY_DERIVE"
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)
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//New xChaChapoly1305 AEAD with 24 byte nonces
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func New(key []byte) (cipher.AEAD, error) {
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if len(key) != KeySize {
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return nil, errors.New("chacha20poly1305: bad key length")
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}
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ret := new(hkdfchacha20poly1305)
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copy(ret.key[:], key)
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return ret, nil
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}
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func (c *hkdfchacha20poly1305) NonceSize() int {
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return NonceSize
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}
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func (c *hkdfchacha20poly1305) Overhead() int {
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return TagSize
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}
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func (c *hkdfchacha20poly1305) Seal(dst, nonce, plaintext, additionalData []byte) []byte {
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if len(nonce) != NonceSize {
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panic("hkdfchacha20poly1305: bad nonce length passed to Seal")
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}
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if uint64(len(plaintext)) > MaxPlaintextSize {
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panic("hkdfchacha20poly1305: plaintext too large")
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}
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subKey, chachaNonce := getSubkeyAndChachaNonceFromHkdf(&c.key, &nonce)
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aead, err := chacha20poly1305.New(subKey[:])
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if err != nil {
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panic("hkdfchacha20poly1305: failed to initialize chacha20poly1305")
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}
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return aead.Seal(dst, chachaNonce[:], plaintext, additionalData)
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}
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func (c *hkdfchacha20poly1305) Open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) {
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if len(nonce) != NonceSize {
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return nil, errors.New("hkdfchacha20poly1305: bad nonce length passed to Open")
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}
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if uint64(len(ciphertext)) > MaxCiphertextSize {
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return nil, errors.New("hkdfchacha20poly1305: ciphertext too large")
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}
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subKey, chachaNonce := getSubkeyAndChachaNonceFromHkdf(&c.key, &nonce)
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aead, err := chacha20poly1305.New(subKey[:])
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if err != nil {
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panic("hkdfchacha20poly1305: failed to initialize chacha20poly1305")
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}
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return aead.Open(dst, chachaNonce[:], ciphertext, additionalData)
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}
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func getSubkeyAndChachaNonceFromHkdf(cKey *[32]byte, nonce *[]byte) (
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subKey [KeySize]byte, chachaNonce [chacha20poly1305.NonceSize]byte) {
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hash := sha256.New
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hkdf := hkdf.New(hash, (*cKey)[:], *nonce, []byte(HkdfInfo))
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_, err := io.ReadFull(hkdf, subKey[:])
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if err != nil {
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panic("hkdfchacha20poly1305: failed to read subkey from hkdf")
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}
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_, err = io.ReadFull(hkdf, chachaNonce[:])
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if err != nil {
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panic("hkdfchacha20poly1305: failed to read chachaNonce from hkdf")
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}
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return
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}
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