diff options
Diffstat (limited to 'src/vendor/golang.org/x/crypto/chacha20poly1305/xchacha20poly1305.go')
-rw-r--r-- | src/vendor/golang.org/x/crypto/chacha20poly1305/xchacha20poly1305.go | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/src/vendor/golang.org/x/crypto/chacha20poly1305/xchacha20poly1305.go b/src/vendor/golang.org/x/crypto/chacha20poly1305/xchacha20poly1305.go new file mode 100644 index 0000000..1cebfe9 --- /dev/null +++ b/src/vendor/golang.org/x/crypto/chacha20poly1305/xchacha20poly1305.go @@ -0,0 +1,86 @@ +// Copyright 2018 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package chacha20poly1305 + +import ( + "crypto/cipher" + "errors" + + "golang.org/x/crypto/chacha20" +) + +type xchacha20poly1305 struct { + key [KeySize]byte +} + +// NewX returns a XChaCha20-Poly1305 AEAD that uses the given 256-bit key. +// +// XChaCha20-Poly1305 is a ChaCha20-Poly1305 variant that takes a longer nonce, +// suitable to be generated randomly without risk of collisions. It should be +// preferred when nonce uniqueness cannot be trivially ensured, or whenever +// nonces are randomly generated. +func NewX(key []byte) (cipher.AEAD, error) { + if len(key) != KeySize { + return nil, errors.New("chacha20poly1305: bad key length") + } + ret := new(xchacha20poly1305) + copy(ret.key[:], key) + return ret, nil +} + +func (*xchacha20poly1305) NonceSize() int { + return NonceSizeX +} + +func (*xchacha20poly1305) Overhead() int { + return Overhead +} + +func (x *xchacha20poly1305) Seal(dst, nonce, plaintext, additionalData []byte) []byte { + if len(nonce) != NonceSizeX { + panic("chacha20poly1305: bad nonce length passed to Seal") + } + + // XChaCha20-Poly1305 technically supports a 64-bit counter, so there is no + // size limit. However, since we reuse the ChaCha20-Poly1305 implementation, + // the second half of the counter is not available. This is unlikely to be + // an issue because the cipher.AEAD API requires the entire message to be in + // memory, and the counter overflows at 256 GB. + if uint64(len(plaintext)) > (1<<38)-64 { + panic("chacha20poly1305: plaintext too large") + } + + c := new(chacha20poly1305) + hKey, _ := chacha20.HChaCha20(x.key[:], nonce[0:16]) + copy(c.key[:], hKey) + + // The first 4 bytes of the final nonce are unused counter space. + cNonce := make([]byte, NonceSize) + copy(cNonce[4:12], nonce[16:24]) + + return c.seal(dst, cNonce[:], plaintext, additionalData) +} + +func (x *xchacha20poly1305) Open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) { + if len(nonce) != NonceSizeX { + panic("chacha20poly1305: bad nonce length passed to Open") + } + if len(ciphertext) < 16 { + return nil, errOpen + } + if uint64(len(ciphertext)) > (1<<38)-48 { + panic("chacha20poly1305: ciphertext too large") + } + + c := new(chacha20poly1305) + hKey, _ := chacha20.HChaCha20(x.key[:], nonce[0:16]) + copy(c.key[:], hKey) + + // The first 4 bytes of the final nonce are unused counter space. + cNonce := make([]byte, NonceSize) + copy(cNonce[4:12], nonce[16:24]) + + return c.open(dst, cNonce[:], ciphertext, additionalData) +} |