Add support for encrypted ssh keys

vendor/github.com/dchest/bcrypt_pbkdf/bcrypt_pbkdf.go

@@ -0,0 +1,97 @@
+// Copyright 2014 Dmitry Chestnykh. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package bcrypt_pbkdf implements password-based key derivation function based
+// on bcrypt compatible with bcrypt_pbkdf(3) from OpenBSD.
+package bcrypt_pbkdf
+
+import (
+	"crypto/sha512"
+	"errors"
+
+	// NOTE! Requires blowfish package version from Aug 1, 2014 or later.
+	// Will produce incorrect results if the package is older.
+	// See commit message for details: http://goo.gl/wx6g8O
+	"golang.org/x/crypto/blowfish"
+)
+
+// Key derives a key from the password, salt and rounds count, returning a
+// []byte of length keyLen that can be used as cryptographic key.
+//
+// Remember to get a good random salt of at least 16 bytes.  Using a higher
+// rounds count will increase the cost of an exhaustive search but will also
+// make derivation proportionally slower.
+func Key(password, salt []byte, rounds, keyLen int) ([]byte, error) {
+	if rounds < 1 {
+		return nil, errors.New("bcrypt_pbkdf: number of rounds is too small")
+	}
+	if len(password) == 0 {
+		return nil, errors.New("bcrypt_pbkdf: empty password")
+	}
+	if len(salt) == 0 || len(salt) > 1<<20 {
+		return nil, errors.New("bcrypt_pbkdf: bad salt length")
+	}
+	if keyLen > 1024 {
+		return nil, errors.New("bcrypt_pbkdf: keyLen is too large")
+	}
+	var shapass, shasalt [sha512.Size]byte
+	var out, tmp [32]byte
+	var cnt [4]byte
+
+	numBlocks := (keyLen + len(out) - 1) / len(out)
+	key := make([]byte, numBlocks*len(out))
+
+	h := sha512.New()
+	h.Write(password)
+	h.Sum(shapass[:0])
+
+	for block := 1; block <= numBlocks; block++ {
+		h.Reset()
+		h.Write(salt)
+		cnt[0] = byte(block >> 24)
+		cnt[1] = byte(block >> 16)
+		cnt[2] = byte(block >> 8)
+		cnt[3] = byte(block)
+		h.Write(cnt[:])
+		bcryptHash(tmp[:], shapass[:], h.Sum(shasalt[:0]))
+		copy(out[:], tmp[:])
+
+		for i := 2; i <= rounds; i++ {
+			h.Reset()
+			h.Write(tmp[:])
+			bcryptHash(tmp[:], shapass[:], h.Sum(shasalt[:0]))
+			for j := 0; j < len(out); j++ {
+				out[j] ^= tmp[j]
+			}
+		}
+
+		for i, v := range out {
+			key[i*numBlocks+(block-1)] = v
+		}
+	}
+	return key[:keyLen], nil
+}
+
+var magic = []byte("OxychromaticBlowfishSwatDynamite")
+
+func bcryptHash(out, shapass, shasalt []byte) {
+	c, err := blowfish.NewSaltedCipher(shapass, shasalt)
+	if err != nil {
+		panic(err)
+	}
+	for i := 0; i < 64; i++ {
+		blowfish.ExpandKey(shasalt, c)
+		blowfish.ExpandKey(shapass, c)
+	}
+	copy(out[:], magic)
+	for i := 0; i < 32; i += 8 {
+		for j := 0; j < 64; j++ {
+			c.Encrypt(out[i:i+8], out[i:i+8])
+		}
+	}
+	// Swap bytes due to different endianness.
+	for i := 0; i < 32; i += 4 {
+		out[i+3], out[i+2], out[i+1], out[i] = out[i], out[i+1], out[i+2], out[i+3]
+	}
+}