diff options
Diffstat (limited to 'sha3/shake.go')
| -rw-r--r-- | sha3/shake.go | 172 |
1 files changed, 49 insertions, 123 deletions
diff --git a/sha3/shake.go b/sha3/shake.go index a6b3a42..6f3f70c 100644 --- a/sha3/shake.go +++ b/sha3/shake.go @@ -4,24 +4,10 @@ package sha3 -// This file defines the ShakeHash interface, and provides -// functions for creating SHAKE and cSHAKE instances, as well as utility -// functions for hashing bytes to arbitrary-length output. -// -// -// SHAKE implementation is based on FIPS PUB 202 [1] -// cSHAKE implementations is based on NIST SP 800-185 [2] -// -// [1] https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.202.pdf -// [2] https://doi.org/10.6028/NIST.SP.800-185 - import ( - "bytes" - "encoding/binary" - "errors" + "crypto/sha3" "hash" "io" - "math/bits" ) // ShakeHash defines the interface to hash functions that support @@ -32,7 +18,7 @@ type ShakeHash interface { hash.Hash // Read reads more output from the hash; reading affects the hash's - // state. (ShakeHash.Read is thus very different from Hash.Sum) + // state. (ShakeHash.Read is thus very different from Hash.Sum.) // It never returns an error, but subsequent calls to Write or Sum // will panic. io.Reader @@ -41,115 +27,18 @@ type ShakeHash interface { Clone() ShakeHash } -// cSHAKE specific context -type cshakeState struct { - *state // SHA-3 state context and Read/Write operations - - // initBlock is the cSHAKE specific initialization set of bytes. It is initialized - // by newCShake function and stores concatenation of N followed by S, encoded - // by the method specified in 3.3 of [1]. - // It is stored here in order for Reset() to be able to put context into - // initial state. - initBlock []byte -} - -func bytepad(data []byte, rate int) []byte { - out := make([]byte, 0, 9+len(data)+rate-1) - out = append(out, leftEncode(uint64(rate))...) - out = append(out, data...) - if padlen := rate - len(out)%rate; padlen < rate { - out = append(out, make([]byte, padlen)...) - } - return out -} - -func leftEncode(x uint64) []byte { - // Let n be the smallest positive integer for which 2^(8n) > x. - n := (bits.Len64(x) + 7) / 8 - if n == 0 { - n = 1 - } - // Return n || x with n as a byte and x an n bytes in big-endian order. - b := make([]byte, 9) - binary.BigEndian.PutUint64(b[1:], x) - b = b[9-n-1:] - b[0] = byte(n) - return b -} - -func newCShake(N, S []byte, rate, outputLen int, dsbyte byte) ShakeHash { - c := cshakeState{state: &state{rate: rate, outputLen: outputLen, dsbyte: dsbyte}} - c.initBlock = make([]byte, 0, 9+len(N)+9+len(S)) // leftEncode returns max 9 bytes - c.initBlock = append(c.initBlock, leftEncode(uint64(len(N))*8)...) - c.initBlock = append(c.initBlock, N...) - c.initBlock = append(c.initBlock, leftEncode(uint64(len(S))*8)...) - c.initBlock = append(c.initBlock, S...) - c.Write(bytepad(c.initBlock, c.rate)) - return &c -} - -// Reset resets the hash to initial state. -func (c *cshakeState) Reset() { - c.state.Reset() - c.Write(bytepad(c.initBlock, c.rate)) -} - -// Clone returns copy of a cSHAKE context within its current state. -func (c *cshakeState) Clone() ShakeHash { - b := make([]byte, len(c.initBlock)) - copy(b, c.initBlock) - return &cshakeState{state: c.clone(), initBlock: b} -} - -// Clone returns copy of SHAKE context within its current state. -func (c *state) Clone() ShakeHash { - return c.clone() -} - -func (c *cshakeState) MarshalBinary() ([]byte, error) { - return c.AppendBinary(make([]byte, 0, marshaledSize+len(c.initBlock))) -} - -func (c *cshakeState) AppendBinary(b []byte) ([]byte, error) { - b, err := c.state.AppendBinary(b) - if err != nil { - return nil, err - } - b = append(b, c.initBlock...) - return b, nil -} - -func (c *cshakeState) UnmarshalBinary(b []byte) error { - if len(b) <= marshaledSize { - return errors.New("sha3: invalid hash state") - } - if err := c.state.UnmarshalBinary(b[:marshaledSize]); err != nil { - return err - } - c.initBlock = bytes.Clone(b[marshaledSize:]) - return nil -} - // NewShake128 creates a new SHAKE128 variable-output-length ShakeHash. // Its generic security strength is 128 bits against all attacks if at // least 32 bytes of its output are used. func NewShake128() ShakeHash { - return newShake128() + return &shakeWrapper{sha3.NewSHAKE128(), 32, false, sha3.NewSHAKE128} } // NewShake256 creates a new SHAKE256 variable-output-length ShakeHash. // Its generic security strength is 256 bits against all attacks if // at least 64 bytes of its output are used. func NewShake256() ShakeHash { - return newShake256() -} - -func newShake128Generic() *state { - return &state{rate: rateK256, outputLen: 32, dsbyte: dsbyteShake} -} - -func newShake256Generic() *state { - return &state{rate: rateK512, outputLen: 64, dsbyte: dsbyteShake} + return &shakeWrapper{sha3.NewSHAKE256(), 64, false, sha3.NewSHAKE256} } // NewCShake128 creates a new instance of cSHAKE128 variable-output-length ShakeHash, @@ -159,10 +48,9 @@ func newShake256Generic() *state { // computations on same input with different S yield unrelated outputs. // When N and S are both empty, this is equivalent to NewShake128. func NewCShake128(N, S []byte) ShakeHash { - if len(N) == 0 && len(S) == 0 { - return NewShake128() - } - return newCShake(N, S, rateK256, 32, dsbyteCShake) + return &shakeWrapper{sha3.NewCSHAKE128(N, S), 32, false, func() *sha3.SHAKE { + return sha3.NewCSHAKE128(N, S) + }} } // NewCShake256 creates a new instance of cSHAKE256 variable-output-length ShakeHash, @@ -172,10 +60,9 @@ func NewCShake128(N, S []byte) ShakeHash { // computations on same input with different S yield unrelated outputs. // When N and S are both empty, this is equivalent to NewShake256. func NewCShake256(N, S []byte) ShakeHash { - if len(N) == 0 && len(S) == 0 { - return NewShake256() - } - return newCShake(N, S, rateK512, 64, dsbyteCShake) + return &shakeWrapper{sha3.NewCSHAKE256(N, S), 64, false, func() *sha3.SHAKE { + return sha3.NewCSHAKE256(N, S) + }} } // ShakeSum128 writes an arbitrary-length digest of data into hash. @@ -191,3 +78,42 @@ func ShakeSum256(hash, data []byte) { h.Write(data) h.Read(hash) } + +// shakeWrapper adds the Size, Sum, and Clone methods to a sha3.SHAKE +// to implement the ShakeHash interface. +type shakeWrapper struct { + *sha3.SHAKE + outputLen int + squeezing bool + newSHAKE func() *sha3.SHAKE +} + +func (w *shakeWrapper) Read(p []byte) (n int, err error) { + w.squeezing = true + return w.SHAKE.Read(p) +} + +func (w *shakeWrapper) Clone() ShakeHash { + s := w.newSHAKE() + b, err := w.MarshalBinary() + if err != nil { + panic(err) // unreachable + } + if err := s.UnmarshalBinary(b); err != nil { + panic(err) // unreachable + } + return &shakeWrapper{s, w.outputLen, w.squeezing, w.newSHAKE} +} + +func (w *shakeWrapper) Size() int { return w.outputLen } + +func (w *shakeWrapper) Sum(b []byte) []byte { + if w.squeezing { + panic("sha3: Sum after Read") + } + out := make([]byte, w.outputLen) + // Clone the state so that we don't affect future Write calls. + s := w.Clone() + s.Read(out) + return append(b, out...) +} |