Bumping k8s dependencies to 1.13

vendor/golang.org/x/crypto/hkdf/hkdf.go

@@ -8,8 +8,6 @@
 // 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 (
@@ -19,6 +17,21 @@ import (
 	"io"
 )
 
+// Extract generates a pseudorandom key for use with Expand from an input secret
+// and an optional independent salt.
+//
+// Only use this function if you need to reuse the extracted key with multiple
+// Expand invocations and different context values. Most common scenarios,
+// including the generation of multiple keys, should use New instead.
+func Extract(hash func() hash.Hash, secret, salt []byte) []byte {
+	if salt == nil {
+		salt = make([]byte, hash().Size())
+	}
+	extractor := hmac.New(hash, salt)
+	extractor.Write(secret)
+	return extractor.Sum(nil)
+}
+
 type hkdf struct {
 	expander hash.Hash
 	size     int
@@ -26,22 +39,22 @@ type hkdf struct {
 	info    []byte
 	counter byte
 
-	prev  []byte
-	cache []byte
+	prev []byte
+	buf  []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
+	remains := len(f.buf) + 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)
+	// Read any leftover from the buffer
+	n := copy(p, f.buf)
 	p = p[n:]
 
-	// Fill the buffer
+	// Fill the rest of the buffer
 	for len(p) > 0 {
 		f.expander.Reset()
 		f.expander.Write(f.prev)
@@ -51,25 +64,30 @@ func (f *hkdf) Read(p []byte) (int, error) {
 		f.counter++
 
 		// Copy the new batch into p
-		f.cache = f.prev
-		n = copy(p, f.cache)
+		f.buf = f.prev
+		n = copy(p, f.buf)
 		p = p[n:]
 	}
 	// Save leftovers for next run
-	f.cache = f.cache[n:]
+	f.buf = f.buf[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}
+// Expand returns a Reader, from which keys can be read, using the given
+// pseudorandom key and optional context info, skipping the extraction step.
+//
+// The pseudorandomKey should have been generated by Extract, or be a uniformly
+// random or pseudorandom cryptographically strong key. See RFC 5869, Section
+// 3.3. Most common scenarios will want to use New instead.
+func Expand(hash func() hash.Hash, pseudorandomKey, info []byte) io.Reader {
+	expander := hmac.New(hash, pseudorandomKey)
+	return &hkdf{expander, expander.Size(), info, 1, nil, nil}
+}
+
+// New returns a Reader, from which keys can be read, using the given hash,
+// secret, salt and context info. Salt and info can be nil.
+func New(hash func() hash.Hash, secret, salt, info []byte) io.Reader {
+	prk := Extract(hash, secret, salt)
+	return Expand(hash, prk, info)
 }