diff options
Diffstat (limited to 'vendor/golang.org/x/crypto/hkdf/hkdf.go')
-rw-r--r-- | vendor/golang.org/x/crypto/hkdf/hkdf.go | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/vendor/golang.org/x/crypto/hkdf/hkdf.go b/vendor/golang.org/x/crypto/hkdf/hkdf.go new file mode 100644 index 000000000..5bc246355 --- /dev/null +++ b/vendor/golang.org/x/crypto/hkdf/hkdf.go @@ -0,0 +1,75 @@ +// Copyright 2014 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 hkdf implements the HMAC-based Extract-and-Expand Key Derivation +// Function (HKDF) as defined in RFC 5869. +// +// HKDF is a cryptographic key derivation function (KDF) with the goal of +// expanding limited input keying material into one or more cryptographically +// strong secret keys. +// +// RFC 5869: https://tools.ietf.org/html/rfc5869 +package hkdf // import "golang.org/x/crypto/hkdf" + +import ( + "crypto/hmac" + "errors" + "hash" + "io" +) + +type hkdf struct { + expander hash.Hash + size int + + info []byte + counter byte + + prev []byte + cache []byte +} + +func (f *hkdf) Read(p []byte) (int, error) { + // Check whether enough data can be generated + need := len(p) + remains := len(f.cache) + int(255-f.counter+1)*f.size + if remains < need { + return 0, errors.New("hkdf: entropy limit reached") + } + // Read from the cache, if enough data is present + n := copy(p, f.cache) + p = p[n:] + + // Fill the buffer + for len(p) > 0 { + f.expander.Reset() + f.expander.Write(f.prev) + f.expander.Write(f.info) + f.expander.Write([]byte{f.counter}) + f.prev = f.expander.Sum(f.prev[:0]) + f.counter++ + + // Copy the new batch into p + f.cache = f.prev + n = copy(p, f.cache) + p = p[n:] + } + // Save leftovers for next run + f.cache = f.cache[n:] + + return need, nil +} + +// New returns a new HKDF using the given hash, the secret keying material to expand +// and optional salt and info fields. +func New(hash func() hash.Hash, secret, salt, info []byte) io.Reader { + if salt == nil { + salt = make([]byte, hash().Size()) + } + extractor := hmac.New(hash, salt) + extractor.Write(secret) + prk := extractor.Sum(nil) + + return &hkdf{hmac.New(hash, prk), extractor.Size(), info, 1, nil, nil} +} |