From 2ea9db77f27192fa1f7fd2be30278cf02f2d8bb2 Mon Sep 17 00:00:00 2001
From: Sergey Matveev <stargrave@stargrave.org>
Date: Sun, 9 Jun 2019 14:59:27 +0300
Subject: [PATCH] KDF_GOSTR3411_2012_256

---
 README                                        |  1 +
 .../gogost/gost34112012256/kdf.go             | 42 ++++++++++++++++++
 .../gogost/gost34112012256/kdf_test.go        | 44 +++++++++++++++++++
 3 files changed, 87 insertions(+)
 create mode 100644 src/cypherpunks.ru/gogost/gost34112012256/kdf.go
 create mode 100644 src/cypherpunks.ru/gogost/gost34112012256/kdf_test.go

diff --git a/README b/README
index 0c97b62..a5eeb17 100644
--- a/README
+++ b/README
@@ -12,6 +12,7 @@ GOST is GOvernment STandard of Russian Federation (and Soviet Union).
 * various 34.10 curve parameters included
 * VKO GOST R 34.10-2001 key agreement function (RFC 4357)
 * VKO GOST R 34.10-2012 key agreement function (RFC 7836)
+* KDF_GOSTR3411_2012_256 KDF function (RFC 7836)
 * GOST R 34.12-2015 128-bit block cipher Кузнечик (Kuznechik) (RFC 7801)
 * GOST R 34.12-2015 64-bit block cipher Магма (Magma)
 * GOST R 34.13-2015 padding methods
diff --git a/src/cypherpunks.ru/gogost/gost34112012256/kdf.go b/src/cypherpunks.ru/gogost/gost34112012256/kdf.go
new file mode 100644
index 0000000..daa2ab3
--- /dev/null
+++ b/src/cypherpunks.ru/gogost/gost34112012256/kdf.go
@@ -0,0 +1,42 @@
+// GoGOST -- Pure Go GOST cryptographic functions library
+// Copyright (C) 2015-2019 Sergey Matveev <stargrave@stargrave.org>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package gost34112012256
+
+import (
+	"crypto/hmac"
+	"hash"
+)
+
+type KDF struct {
+	h hash.Hash
+}
+
+func NewKDF(key []byte) *KDF {
+	return &KDF{hmac.New(New, key)}
+}
+
+func (kdf *KDF) Derive(dst, label, seed []byte) (r []byte) {
+	kdf.h.Write([]byte{0x01})
+	kdf.h.Write(label)
+	kdf.h.Write([]byte{0x00})
+	kdf.h.Write(seed)
+	kdf.h.Write([]byte{0x01})
+	kdf.h.Write([]byte{0x00})
+	r = kdf.h.Sum(dst)
+	kdf.h.Reset()
+	return r
+}
diff --git a/src/cypherpunks.ru/gogost/gost34112012256/kdf_test.go b/src/cypherpunks.ru/gogost/gost34112012256/kdf_test.go
new file mode 100644
index 0000000..2b66b19
--- /dev/null
+++ b/src/cypherpunks.ru/gogost/gost34112012256/kdf_test.go
@@ -0,0 +1,44 @@
+// GoGOST -- Pure Go GOST cryptographic functions library
+// Copyright (C) 2015-2019 Sergey Matveev <stargrave@stargrave.org>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package gost34112012256
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestKDFGOSTR34112012256(t *testing.T) {
+	kdf := NewKDF([]byte{
+		0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+		0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+		0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+		0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+	})
+	derived := kdf.Derive(
+		nil,
+		[]byte{0x26, 0xbd, 0xb8, 0x78},
+		[]byte{0xaf, 0x21, 0x43, 0x41, 0x45, 0x65, 0x63, 0x78},
+	)
+	if bytes.Compare(derived, []byte{
+		0xa1, 0xaa, 0x5f, 0x7d, 0xe4, 0x02, 0xd7, 0xb3,
+		0xd3, 0x23, 0xf2, 0x99, 0x1c, 0x8d, 0x45, 0x34,
+		0x01, 0x31, 0x37, 0x01, 0x0a, 0x83, 0x75, 0x4f,
+		0xd0, 0xaf, 0x6d, 0x7c, 0xd4, 0x92, 0x2e, 0xd9,
+	}) != 0 {
+		t.FailNow()
+	}
+}
-- 
2.44.0