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Diffstat (limited to 'src/vendor/golang.org/x/crypto/chacha20poly1305/chacha20poly1305.go')
-rw-r--r-- | src/vendor/golang.org/x/crypto/chacha20poly1305/chacha20poly1305.go | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/src/vendor/golang.org/x/crypto/chacha20poly1305/chacha20poly1305.go b/src/vendor/golang.org/x/crypto/chacha20poly1305/chacha20poly1305.go new file mode 100644 index 0000000..93da732 --- /dev/null +++ b/src/vendor/golang.org/x/crypto/chacha20poly1305/chacha20poly1305.go @@ -0,0 +1,98 @@ +// Copyright 2016 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 implements the ChaCha20-Poly1305 AEAD and its +// extended nonce variant XChaCha20-Poly1305, as specified in RFC 8439 and +// draft-irtf-cfrg-xchacha-01. +package chacha20poly1305 // import "golang.org/x/crypto/chacha20poly1305" + +import ( + "crypto/cipher" + "errors" +) + +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 the standard variant of this + // AEAD, in bytes. + // + // Note that this is too short to be safely generated at random if the same + // key is reused more than 2³² times. + NonceSize = 12 + + // NonceSizeX is the size of the nonce used with the XChaCha20-Poly1305 + // variant of this AEAD, in bytes. + NonceSizeX = 24 + + // Overhead is the size of the Poly1305 authentication tag, and the + // difference between a ciphertext length and its plaintext. + Overhead = 16 +) + +type chacha20poly1305 struct { + key [KeySize]byte +} + +// New returns a ChaCha20-Poly1305 AEAD that uses the given 256-bit key. +func New(key []byte) (cipher.AEAD, error) { + if len(key) != KeySize { + return nil, errors.New("chacha20poly1305: bad key length") + } + ret := new(chacha20poly1305) + copy(ret.key[:], key) + return ret, nil +} + +func (c *chacha20poly1305) NonceSize() int { + return NonceSize +} + +func (c *chacha20poly1305) Overhead() int { + return Overhead +} + +func (c *chacha20poly1305) Seal(dst, nonce, plaintext, additionalData []byte) []byte { + if len(nonce) != NonceSize { + panic("chacha20poly1305: bad nonce length passed to Seal") + } + + if uint64(len(plaintext)) > (1<<38)-64 { + panic("chacha20poly1305: plaintext too large") + } + + return c.seal(dst, nonce, plaintext, additionalData) +} + +var errOpen = errors.New("chacha20poly1305: message authentication failed") + +func (c *chacha20poly1305) Open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) { + if len(nonce) != NonceSize { + 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") + } + + return c.open(dst, nonce, ciphertext, additionalData) +} + +// sliceForAppend takes a slice and a requested number of bytes. It returns a +// slice with the contents of the given slice followed by that many bytes and a +// second slice that aliases into it and contains only the extra bytes. If the +// original slice has sufficient capacity then no allocation is performed. +func sliceForAppend(in []byte, n int) (head, tail []byte) { + if total := len(in) + n; cap(in) >= total { + head = in[:total] + } else { + head = make([]byte, total) + copy(head, in) + } + tail = head[len(in):] + return +} |