diff options
Diffstat (limited to 'vendor/golang.org/x/crypto/poly1305/poly1305.go')
| -rw-r--r-- | vendor/golang.org/x/crypto/poly1305/poly1305.go | 80 |
1 files changed, 65 insertions, 15 deletions
diff --git a/vendor/golang.org/x/crypto/poly1305/poly1305.go b/vendor/golang.org/x/crypto/poly1305/poly1305.go index f562fa57..d076a562 100644 --- a/vendor/golang.org/x/crypto/poly1305/poly1305.go +++ b/vendor/golang.org/x/crypto/poly1305/poly1305.go @@ -2,21 +2,19 @@ // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. -/* -Package poly1305 implements Poly1305 one-time message authentication code as -specified in https://cr.yp.to/mac/poly1305-20050329.pdf. - -Poly1305 is a fast, one-time authentication function. It is infeasible for an -attacker to generate an authenticator for a message without the key. However, a -key must only be used for a single message. Authenticating two different -messages with the same key allows an attacker to forge authenticators for other -messages with the same key. - -Poly1305 was originally coupled with AES in order to make Poly1305-AES. AES was -used with a fixed key in order to generate one-time keys from an nonce. -However, in this package AES isn't used and the one-time key is specified -directly. -*/ +// Package poly1305 implements Poly1305 one-time message authentication code as +// specified in https://cr.yp.to/mac/poly1305-20050329.pdf. +// +// Poly1305 is a fast, one-time authentication function. It is infeasible for an +// attacker to generate an authenticator for a message without the key. However, a +// key must only be used for a single message. Authenticating two different +// messages with the same key allows an attacker to forge authenticators for other +// messages with the same key. +// +// Poly1305 was originally coupled with AES in order to make Poly1305-AES. AES was +// used with a fixed key in order to generate one-time keys from an nonce. +// However, in this package AES isn't used and the one-time key is specified +// directly. package poly1305 // import "golang.org/x/crypto/poly1305" import "crypto/subtle" @@ -31,3 +29,55 @@ func Verify(mac *[16]byte, m []byte, key *[32]byte) bool { Sum(&tmp, m, key) return subtle.ConstantTimeCompare(tmp[:], mac[:]) == 1 } + +// New returns a new MAC computing an authentication +// tag of all data written to it with the given key. +// This allows writing the message progressively instead +// of passing it as a single slice. Common users should use +// the Sum function instead. +// +// The key must be unique for each message, as authenticating +// two different messages with the same key allows an attacker +// to forge messages at will. +func New(key *[32]byte) *MAC { + return &MAC{ + mac: newMAC(key), + finalized: false, + } +} + +// MAC is an io.Writer computing an authentication tag +// of the data written to it. +// +// MAC cannot be used like common hash.Hash implementations, +// because using a poly1305 key twice breaks its security. +// Therefore writing data to a running MAC after calling +// Sum causes it to panic. +type MAC struct { + mac // platform-dependent implementation + + finalized bool +} + +// Size returns the number of bytes Sum will return. +func (h *MAC) Size() int { return TagSize } + +// Write adds more data to the running message authentication code. +// It never returns an error. +// +// It must not be called after the first call of Sum. +func (h *MAC) Write(p []byte) (n int, err error) { + if h.finalized { + panic("poly1305: write to MAC after Sum") + } + return h.mac.Write(p) +} + +// Sum computes the authenticator of all data written to the +// message authentication code. +func (h *MAC) Sum(b []byte) []byte { + var mac [TagSize]byte + h.mac.Sum(&mac) + h.finalized = true + return append(b, mac[:]...) +} |