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crypto/subtle/hkdf.go

@@ -0,0 +1,55 @@
+package subtle
+
+import (
+	"errors"
+	"fmt"
+	"io"
+
+	"golang.org/x/crypto/hkdf"
+)
+
+const (
+	// Minimum tag size in bytes. This provides minimum 80-bit security strength.
+	minTagSizeInBytes = uint32(10)
+)
+
+var errHKDFInvalidInput = errors.New("HKDF: invalid input")
+
+// validateHKDFParams validates parameters of HKDF constructor.
+func validateHKDFParams(hash string, _ uint32, tagSize uint32) error {
+	// validate tag size
+	digestSize, err := GetHashDigestSize(hash)
+	if err != nil {
+		return err
+	}
+	if tagSize > 255*digestSize {
+		return fmt.Errorf("tag size too big")
+	}
+	if tagSize < minTagSizeInBytes {
+		return fmt.Errorf("tag size too small")
+	}
+	return nil
+}
+
+// ComputeHKDF extracts a pseudorandom key.
+func ComputeHKDF(hashAlg string, key []byte, salt []byte, info []byte, tagSize uint32) ([]byte, error) {
+	keySize := uint32(len(key))
+	if err := validateHKDFParams(hashAlg, keySize, tagSize); err != nil {
+		return nil, fmt.Errorf("hkdf: %s", err)
+	}
+	hashFunc := GetHashFunc(hashAlg)
+	if hashFunc == nil {
+		return nil, fmt.Errorf("hkdf: invalid hash algorithm")
+	}
+	if len(salt) == 0 {
+		salt = make([]byte, hashFunc().Size())
+	}
+
+	result := make([]byte, tagSize)
+	kdf := hkdf.New(hashFunc, key, salt, info)
+	n, err := io.ReadFull(kdf, result)
+	if n != len(result) || err != nil {
+		return nil, fmt.Errorf("compute of hkdf failed")
+	}
+	return result, nil
+}

crypto/subtle/random/random.go

@@ -0,0 +1,22 @@
+package random
+
+import (
+	"crypto/rand"
+	"encoding/binary"
+)
+
+// GetRandomBytes randomly generates n bytes.
+func GetRandomBytes(n uint32) []byte {
+	buf := make([]byte, n)
+	_, err := rand.Read(buf)
+	if err != nil {
+		panic(err) // out of randomness, should never happen
+	}
+	return buf
+}
+
+// GetRandomUint32 randomly generates an unsigned 32-bit integer.
+func GetRandomUint32() uint32 {
+	b := GetRandomBytes(4)
+	return binary.BigEndian.Uint32(b)
+}

crypto/subtle/random/random_test.go

@@ -0,0 +1,16 @@
+package random_test
+
+import (
+	"testing"
+
+	"github.com/onsonr/hway/crypto/subtle/random"
+)
+
+func TestGetRandomBytes(t *testing.T) {
+	for i := 0; i <= 32; i++ {
+		buf := random.GetRandomBytes(uint32(i))
+		if len(buf) != i {
+			t.Errorf("length of the output doesn't match the input")
+		}
+	}
+}

crypto/subtle/subtle.go

@@ -0,0 +1,130 @@
+package subtle
+
+import (
+	"crypto/elliptic"
+	"crypto/sha1"
+	"crypto/sha256"
+	"crypto/sha512"
+	"encoding/hex"
+	"errors"
+	"hash"
+	"math/big"
+)
+
+var errNilHashFunc = errors.New("nil hash function")
+
+// hashDigestSize maps hash algorithms to their digest size in bytes.
+var hashDigestSize = map[string]uint32{
+	"SHA1":   uint32(20),
+	"SHA224": uint32(28),
+	"SHA256": uint32(32),
+	"SHA384": uint32(48),
+	"SHA512": uint32(64),
+}
+
+// GetHashDigestSize returns the digest size of the specified hash algorithm.
+func GetHashDigestSize(hash string) (uint32, error) {
+	digestSize, ok := hashDigestSize[hash]
+	if !ok {
+		return 0, errors.New("invalid hash algorithm")
+	}
+	return digestSize, nil
+}
+
+// TODO(ckl): Perhaps return an explicit error instead of ""/nil for the
+// following functions.
+
+// ConvertHashName converts different forms of a hash name to the
+// hash name that tink recognizes.
+func ConvertHashName(name string) string {
+	switch name {
+	case "SHA-224":
+		return "SHA224"
+	case "SHA-256":
+		return "SHA256"
+	case "SHA-384":
+		return "SHA384"
+	case "SHA-512":
+		return "SHA512"
+	case "SHA-1":
+		return "SHA1"
+	default:
+		return ""
+	}
+}
+
+// ConvertCurveName converts different forms of a curve name to the
+// name that tink recognizes.
+func ConvertCurveName(name string) string {
+	switch name {
+	case "secp256r1", "P-256":
+		return "NIST_P256"
+	case "secp384r1", "P-384":
+		return "NIST_P384"
+	case "secp521r1", "P-521":
+		return "NIST_P521"
+	default:
+		return ""
+	}
+}
+
+// GetHashFunc returns the corresponding hash function of the given hash name.
+func GetHashFunc(hash string) func() hash.Hash {
+	switch hash {
+	case "SHA1":
+		return sha1.New
+	case "SHA224":
+		return sha256.New224
+	case "SHA256":
+		return sha256.New
+	case "SHA384":
+		return sha512.New384
+	case "SHA512":
+		return sha512.New
+	default:
+		return nil
+	}
+}
+
+// GetCurve returns the curve object that corresponds to the given curve type.
+// It returns null if the curve type is not supported.
+func GetCurve(curve string) elliptic.Curve {
+	switch curve {
+	case "NIST_P256":
+		return elliptic.P256()
+	case "NIST_P384":
+		return elliptic.P384()
+	case "NIST_P521":
+		return elliptic.P521()
+	default:
+		return nil
+	}
+}
+
+// ComputeHash calculates a hash of the given data using the given hash function.
+func ComputeHash(hashFunc func() hash.Hash, data []byte) ([]byte, error) {
+	if hashFunc == nil {
+		return nil, errNilHashFunc
+	}
+	h := hashFunc()
+
+	_, err := h.Write(data)
+	if err != nil {
+		return nil, err
+	}
+
+	return h.Sum(nil), nil
+}
+
+// NewBigIntFromHex returns a big integer from a hex string.
+func NewBigIntFromHex(s string) (*big.Int, error) {
+	if len(s)%2 == 1 {
+		s = "0" + s
+	}
+	b, err := hex.DecodeString(s)
+	if err != nil {
+		return nil, err
+	}
+	ret := new(big.Int).SetBytes(b)
+	return ret, nil
+}

crypto/subtle/x25519.go

@@ -0,0 +1,25 @@
+package subtle
+
+import (
+	"crypto/rand"
+
+	"golang.org/x/crypto/curve25519"
+)
+
+// GeneratePrivateKeyX25519 generates a new 32-byte private key.
+func GeneratePrivateKeyX25519() ([]byte, error) {
+	privKey := make([]byte, curve25519.ScalarSize)
+	_, err := rand.Read(privKey)
+	return privKey, err
+}
+
+// ComputeSharedSecretX25519 returns the 32-byte shared key, i.e.
+// privKey * pubValue on the curve.
+func ComputeSharedSecretX25519(privKey, pubValue []byte) ([]byte, error) {
+	return curve25519.X25519(privKey, pubValue)
+}
+
+// PublicFromPrivateX25519 computes privKey's corresponding public key.
+func PublicFromPrivateX25519(privKey []byte) ([]byte, error) {
+	return ComputeSharedSecretX25519(privKey, curve25519.Basepoint)
+}