You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
 
 
 
 

106 lines
3.2 KiB

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