crypto/pbkdf2: init package

This commit imports the x/crypto/pbkdf2 package as described in the
linked proposal. The code is unchanged with the exception of a few
small updates to reflect feedback from the proposal comment period:

* the Key function is made generic over a hash.Hash
* the h function is moved to be the first argument
* keyLen is renamed to keyLength
* an error return is added
* the unit tests were moved to the pbkdf2_test package

Updates #69488

Change-Id: If72f854daeb65a5c7fbe45ebd341e63a33340624
Reviewed-on: https://go-review.googlesource.com/c/go/+/628135
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Russ Cox <rsc@golang.org>

3 files changed, 263 insertions, 0 deletions

diff --git a/src/crypto/pbkdf2/pbkdf2.go b/src/crypto/pbkdf2/pbkdf2.go
new file mode 100644
index 0000000000..0887365388
--- /dev/null
+++ b/src/crypto/pbkdf2/pbkdf2.go
@@ -0,0 +1,77 @@
+// Copyright 2012 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 pbkdf2 implements the key derivation function PBKDF2 as defined in RFC
+2898 / PKCS #5 v2.0.
+
+A key derivation function is useful when encrypting data based on a password
+or any other not-fully-random data. It uses a pseudorandom function to derive
+a secure encryption key based on the password.
+
+While v2.0 of the standard defines only one pseudorandom function to use,
+HMAC-SHA1, the drafted v2.1 specification allows use of all five FIPS Approved
+Hash Functions SHA-1, SHA-224, SHA-256, SHA-384 and SHA-512 for HMAC. To
+choose, you can pass the `New` functions from the different SHA packages to
+pbkdf2.Key.
+*/
+package pbkdf2
+
+import (
+	"crypto/hmac"
+	"hash"
+)
+
+// Key derives a key from the password, salt and iteration count, returning a
+// []byte of length keyLength that can be used as cryptographic key. The key is
+// derived based on the method described as PBKDF2 with the HMAC variant using
+// the supplied hash function.
+//
+// For example, to use a HMAC-SHA-1 based PBKDF2 key derivation function, you
+// can get a derived key for e.g. AES-256 (which needs a 32-byte key) by
+// doing:
+//
+//	dk := pbkdf2.Key(sha1.New, []byte("some password"), salt, 4096, 32)
+//
+// Remember to get a good random salt. At least 8 bytes is recommended by the
+// RFC.
+//
+// Using a higher iteration count will increase the cost of an exhaustive
+// search but will also make derivation proportionally slower.
+func Key[Hash hash.Hash](h func() Hash, password string, salt []byte, iter, keyLength int) ([]byte, error) {
+	prf := hmac.New(func() hash.Hash { return h() }, []byte(password))
+	hashLen := prf.Size()
+	numBlocks := (keyLength + hashLen - 1) / hashLen
+
+	var buf [4]byte
+	dk := make([]byte, 0, numBlocks*hashLen)
+	U := make([]byte, hashLen)
+	for block := 1; block <= numBlocks; block++ {
+		// N.B.: || means concatenation, ^ means XOR
+		// for each block T_i = U_1 ^ U_2 ^ ... ^ U_iter
+		// U_1 = PRF(password, salt || uint(i))
+		prf.Reset()
+		prf.Write(salt)
+		buf[0] = byte(block >> 24)
+		buf[1] = byte(block >> 16)
+		buf[2] = byte(block >> 8)
+		buf[3] = byte(block)
+		prf.Write(buf[:4])
+		dk = prf.Sum(dk)
+		T := dk[len(dk)-hashLen:]
+		copy(U, T)
+
+		// U_n = PRF(password, U_(n-1))
+		for n := 2; n <= iter; n++ {
+			prf.Reset()
+			prf.Write(U)
+			U = U[:0]
+			U = prf.Sum(U)
+			for x := range U {
+				T[x] ^= U[x]
+			}
+		}
+	}
+	return dk[:keyLength], nil
+}
diff --git a/src/crypto/pbkdf2/pbkdf2_test.go b/src/crypto/pbkdf2/pbkdf2_test.go
new file mode 100644
index 0000000000..ecce26f8ba
--- /dev/null
+++ b/src/crypto/pbkdf2/pbkdf2_test.go
@@ -0,0 +1,184 @@
+// Copyright 2012 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 pbkdf2_test
+
+import (
+	"bytes"
+	"crypto/pbkdf2"
+	"crypto/sha1"
+	"crypto/sha256"
+	"hash"
+	"testing"
+)
+
+type testVector struct {
+	password string
+	salt     string
+	iter     int
+	output   []byte
+}
+
+// Test vectors from RFC 6070, http://tools.ietf.org/html/rfc6070
+var sha1TestVectors = []testVector{
+	{
+		"password",
+		"salt",
+		1,
+		[]byte{
+			0x0c, 0x60, 0xc8, 0x0f, 0x96, 0x1f, 0x0e, 0x71,
+			0xf3, 0xa9, 0xb5, 0x24, 0xaf, 0x60, 0x12, 0x06,
+			0x2f, 0xe0, 0x37, 0xa6,
+		},
+	},
+	{
+		"password",
+		"salt",
+		2,
+		[]byte{
+			0xea, 0x6c, 0x01, 0x4d, 0xc7, 0x2d, 0x6f, 0x8c,
+			0xcd, 0x1e, 0xd9, 0x2a, 0xce, 0x1d, 0x41, 0xf0,
+			0xd8, 0xde, 0x89, 0x57,
+		},
+	},
+	{
+		"password",
+		"salt",
+		4096,
+		[]byte{
+			0x4b, 0x00, 0x79, 0x01, 0xb7, 0x65, 0x48, 0x9a,
+			0xbe, 0xad, 0x49, 0xd9, 0x26, 0xf7, 0x21, 0xd0,
+			0x65, 0xa4, 0x29, 0xc1,
+		},
+	},
+	// // This one takes too long
+	// {
+	// 	"password",
+	// 	"salt",
+	// 	16777216,
+	// 	[]byte{
+	// 		0xee, 0xfe, 0x3d, 0x61, 0xcd, 0x4d, 0xa4, 0xe4,
+	// 		0xe9, 0x94, 0x5b, 0x3d, 0x6b, 0xa2, 0x15, 0x8c,
+	// 		0x26, 0x34, 0xe9, 0x84,
+	// 	},
+	// },
+	{
+		"passwordPASSWORDpassword",
+		"saltSALTsaltSALTsaltSALTsaltSALTsalt",
+		4096,
+		[]byte{
+			0x3d, 0x2e, 0xec, 0x4f, 0xe4, 0x1c, 0x84, 0x9b,
+			0x80, 0xc8, 0xd8, 0x36, 0x62, 0xc0, 0xe4, 0x4a,
+			0x8b, 0x29, 0x1a, 0x96, 0x4c, 0xf2, 0xf0, 0x70,
+			0x38,
+		},
+	},
+	{
+		"pass\000word",
+		"sa\000lt",
+		4096,
+		[]byte{
+			0x56, 0xfa, 0x6a, 0xa7, 0x55, 0x48, 0x09, 0x9d,
+			0xcc, 0x37, 0xd7, 0xf0, 0x34, 0x25, 0xe0, 0xc3,
+		},
+	},
+}
+
+// Test vectors from
+// http://stackoverflow.com/questions/5130513/pbkdf2-hmac-sha2-test-vectors
+var sha256TestVectors = []testVector{
+	{
+		"password",
+		"salt",
+		1,
+		[]byte{
+			0x12, 0x0f, 0xb6, 0xcf, 0xfc, 0xf8, 0xb3, 0x2c,
+			0x43, 0xe7, 0x22, 0x52, 0x56, 0xc4, 0xf8, 0x37,
+			0xa8, 0x65, 0x48, 0xc9,
+		},
+	},
+	{
+		"password",
+		"salt",
+		2,
+		[]byte{
+			0xae, 0x4d, 0x0c, 0x95, 0xaf, 0x6b, 0x46, 0xd3,
+			0x2d, 0x0a, 0xdf, 0xf9, 0x28, 0xf0, 0x6d, 0xd0,
+			0x2a, 0x30, 0x3f, 0x8e,
+		},
+	},
+	{
+		"password",
+		"salt",
+		4096,
+		[]byte{
+			0xc5, 0xe4, 0x78, 0xd5, 0x92, 0x88, 0xc8, 0x41,
+			0xaa, 0x53, 0x0d, 0xb6, 0x84, 0x5c, 0x4c, 0x8d,
+			0x96, 0x28, 0x93, 0xa0,
+		},
+	},
+	{
+		"passwordPASSWORDpassword",
+		"saltSALTsaltSALTsaltSALTsaltSALTsalt",
+		4096,
+		[]byte{
+			0x34, 0x8c, 0x89, 0xdb, 0xcb, 0xd3, 0x2b, 0x2f,
+			0x32, 0xd8, 0x14, 0xb8, 0x11, 0x6e, 0x84, 0xcf,
+			0x2b, 0x17, 0x34, 0x7e, 0xbc, 0x18, 0x00, 0x18,
+			0x1c,
+		},
+	},
+	{
+		"pass\000word",
+		"sa\000lt",
+		4096,
+		[]byte{
+			0x89, 0xb6, 0x9d, 0x05, 0x16, 0xf8, 0x29, 0x89,
+			0x3c, 0x69, 0x62, 0x26, 0x65, 0x0a, 0x86, 0x87,
+		},
+	},
+}
+
+func testHash(t *testing.T, h func() hash.Hash, hashName string, vectors []testVector) {
+	for i, v := range vectors {
+		o, err := pbkdf2.Key(h, v.password, []byte(v.salt), v.iter, len(v.output))
+		if err != nil {
+			t.Error(err)
+		}
+		if !bytes.Equal(o, v.output) {
+			t.Errorf("%s %d: expected %x, got %x", hashName, i, v.output, o)
+		}
+	}
+}
+
+func TestWithHMACSHA1(t *testing.T) {
+	testHash(t, sha1.New, "SHA1", sha1TestVectors)
+}
+
+func TestWithHMACSHA256(t *testing.T) {
+	testHash(t, sha256.New, "SHA256", sha256TestVectors)
+}
+
+var sink uint8
+
+func benchmark(b *testing.B, h func() hash.Hash) {
+	var err error
+	password := make([]byte, h().Size())
+	salt := make([]byte, 8)
+	for i := 0; i < b.N; i++ {
+		password, err = pbkdf2.Key(h, string(password), salt, 4096, len(password))
+		if err != nil {
+			b.Error(err)
+		}
+	}
+	sink += password[0]
+}
+
+func BenchmarkHMACSHA1(b *testing.B) {
+	benchmark(b, sha1.New)
+}
+
+func BenchmarkHMACSHA256(b *testing.B) {
+	benchmark(b, sha256.New)
+}
diff --git a/src/go/build/deps_test.go b/src/go/build/deps_test.go
index bbaedbfbd8..a4003442ae 100644
--- a/src/go/build/deps_test.go
+++ b/src/go/build/deps_test.go
@@ -516,6 +516,8 @@ var depsRules = `
 	crypto/boring, crypto/internal/fips140/edwards25519/field
 	< crypto/ecdh;
 
+	crypto/hmac < crypto/pbkdf2;
+
 	# Unfortunately, stuck with reflect via encoding/binary.
 	encoding/binary, crypto/boring < golang.org/x/crypto/sha3;