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|
package handshake
import (
"crypto"
"crypto/aes"
"crypto/cipher"
"crypto/tls"
"fmt"
"golang.org/x/crypto/chacha20poly1305"
)
// These cipher suite implementations are copied from the standard library crypto/tls package.
const aeadNonceLength = 12
type cipherSuite struct {
ID uint16
Hash crypto.Hash
KeyLen int
AEAD func(key, nonceMask []byte) *xorNonceAEAD
}
func (s cipherSuite) IVLen() int { return aeadNonceLength }
func getCipherSuite(id uint16) *cipherSuite {
switch id {
case tls.TLS_AES_128_GCM_SHA256:
return &cipherSuite{ID: tls.TLS_AES_128_GCM_SHA256, Hash: crypto.SHA256, KeyLen: 16, AEAD: aeadAESGCMTLS13}
case tls.TLS_CHACHA20_POLY1305_SHA256:
return &cipherSuite{ID: tls.TLS_CHACHA20_POLY1305_SHA256, Hash: crypto.SHA256, KeyLen: 32, AEAD: aeadChaCha20Poly1305}
case tls.TLS_AES_256_GCM_SHA384:
return &cipherSuite{ID: tls.TLS_AES_256_GCM_SHA384, Hash: crypto.SHA384, KeyLen: 32, AEAD: aeadAESGCMTLS13}
default:
panic(fmt.Sprintf("unknown cypher suite: %d", id))
}
}
func aeadAESGCMTLS13(key, nonceMask []byte) *xorNonceAEAD {
if len(nonceMask) != aeadNonceLength {
panic("tls: internal error: wrong nonce length")
}
aes, err := aes.NewCipher(key)
if err != nil {
panic(err)
}
aead, err := cipher.NewGCM(aes)
if err != nil {
panic(err)
}
ret := &xorNonceAEAD{aead: aead}
copy(ret.nonceMask[:], nonceMask)
return ret
}
func aeadChaCha20Poly1305(key, nonceMask []byte) *xorNonceAEAD {
if len(nonceMask) != aeadNonceLength {
panic("tls: internal error: wrong nonce length")
}
aead, err := chacha20poly1305.New(key)
if err != nil {
panic(err)
}
ret := &xorNonceAEAD{aead: aead}
copy(ret.nonceMask[:], nonceMask)
return ret
}
// xorNonceAEAD wraps an AEAD by XORing in a fixed pattern to the nonce
// before each call.
type xorNonceAEAD struct {
nonceMask [aeadNonceLength]byte
aead cipher.AEAD
}
func (f *xorNonceAEAD) NonceSize() int { return 8 } // 64-bit sequence number
func (f *xorNonceAEAD) Overhead() int { return f.aead.Overhead() }
func (f *xorNonceAEAD) explicitNonceLen() int { return 0 }
func (f *xorNonceAEAD) Seal(out, nonce, plaintext, additionalData []byte) []byte {
for i, b := range nonce {
f.nonceMask[4+i] ^= b
}
result := f.aead.Seal(out, f.nonceMask[:], plaintext, additionalData)
for i, b := range nonce {
f.nonceMask[4+i] ^= b
}
return result
}
func (f *xorNonceAEAD) Open(out, nonce, ciphertext, additionalData []byte) ([]byte, error) {
for i, b := range nonce {
f.nonceMask[4+i] ^= b
}
result, err := f.aead.Open(out, f.nonceMask[:], ciphertext, additionalData)
for i, b := range nonce {
f.nonceMask[4+i] ^= b
}
return result, err
}
|
