1 files changed, 180 insertions, 0 deletions
diff --git a/src/pkg/crypto/openpgp/s2k/s2k.go b/src/pkg/crypto/openpgp/s2k/s2k.go
new file mode 100644
index 000000000..da926a76e
--- /dev/null
+++ b/src/pkg/crypto/openpgp/s2k/s2k.go
@@ -0,0 +1,180 @@
+// Copyright 2011 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 s2k implements the various OpenPGP string-to-key transforms as
+// specified in RFC 4800 section 3.7.1.
+package s2k
+
+import (
+	"crypto"
+	"crypto/openpgp/error"
+	"hash"
+	"io"
+	"os"
+	"strconv"
+)
+
+// Simple writes to out the result of computing the Simple S2K function (RFC
+// 4880, section 3.7.1.1) using the given hash and input passphrase.
+func Simple(out []byte, h hash.Hash, in []byte) {
+	Salted(out, h, in, nil)
+}
+
+var zero [1]byte
+
+// Salted writes to out the result of computing the Salted S2K function (RFC
+// 4880, section 3.7.1.2) using the given hash, input passphrase and salt.
+func Salted(out []byte, h hash.Hash, in []byte, salt []byte) {
+	done := 0
+
+	for i := 0; done < len(out); i++ {
+		h.Reset()
+		for j := 0; j < i; j++ {
+			h.Write(zero[:])
+		}
+		h.Write(salt)
+		h.Write(in)
+		n := copy(out[done:], h.Sum())
+		done += n
+	}
+}
+
+// Iterated writes to out the result of computing the Iterated and Salted S2K
+// function (RFC 4880, section 3.7.1.3) using the given hash, input passphrase,
+// salt and iteration count.
+func Iterated(out []byte, h hash.Hash, in []byte, salt []byte, count int) {
+	combined := make([]byte, len(in)+len(salt))
+	copy(combined, salt)
+	copy(combined[len(salt):], in)
+
+	if count < len(combined) {
+		count = len(combined)
+	}
+
+	done := 0
+	for i := 0; done < len(out); i++ {
+		h.Reset()
+		for j := 0; j < i; j++ {
+			h.Write(zero[:])
+		}
+		written := 0
+		for written < count {
+			if written+len(combined) > count {
+				todo := count - written
+				h.Write(combined[:todo])
+				written = count
+			} else {
+				h.Write(combined)
+				written += len(combined)
+			}
+		}
+		n := copy(out[done:], h.Sum())
+		done += n
+	}
+}
+
+// Parse reads a binary specification for a string-to-key transformation from r
+// and returns a function which performs that transform.
+func Parse(r io.Reader) (f func(out, in []byte), err os.Error) {
+	var buf [9]byte
+
+	_, err = io.ReadFull(r, buf[:2])
+	if err != nil {
+		return
+	}
+
+	hash, ok := HashIdToHash(buf[1])
+	if !ok {
+		return nil, error.UnsupportedError("hash for S2K function: " + strconv.Itoa(int(buf[1])))
+	}
+	h := hash.New()
+	if h == nil {
+		return nil, error.UnsupportedError("hash not available: " + strconv.Itoa(int(hash)))
+	}
+
+	switch buf[0] {
+	case 1:
+		f := func(out, in []byte) {
+			Simple(out, h, in)
+		}
+		return f, nil
+	case 2:
+		_, err := io.ReadFull(r, buf[:8])
+		if err != nil {
+			return
+		}
+		f := func(out, in []byte) {
+			Salted(out, h, in, buf[:8])
+		}
+		return f, nil
+	case 3:
+		_, err := io.ReadFull(r, buf[:9])
+		if err != nil {
+			return
+		}
+		count := (16 + int(buf[8]&15)) << (uint32(buf[8]>>4) + 6)
+		f := func(out, in []byte) {
+			Iterated(out, h, in, buf[:8], count)
+		}
+		return f, nil
+	}
+
+	return nil, error.UnsupportedError("S2K function")
+}
+
+// Serialize salts and stretches the given passphrase and writes the resulting
+// key into key. It also serializes an S2K descriptor to w.
+func Serialize(w io.Writer, key []byte, rand io.Reader, passphrase []byte) os.Error {
+	var buf [11]byte
+	buf[0] = 3 /* iterated and salted */
+	buf[1], _ = HashToHashId(crypto.SHA1)
+	salt := buf[2:10]
+	if _, err := io.ReadFull(rand, salt); err != nil {
+		return err
+	}
+	const count = 65536 // this is the default in gpg
+	buf[10] = 96        // 65536 iterations
+	if _, err := w.Write(buf[:]); err != nil {
+		return err
+	}
+
+	Iterated(key, crypto.SHA1.New(), passphrase, salt, count)
+	return nil
+}
+
+// hashToHashIdMapping contains pairs relating OpenPGP's hash identifier with
+// Go's crypto.Hash type. See RFC 4880, section 9.4.
+var hashToHashIdMapping = []struct {
+	id   byte
+	hash crypto.Hash
+}{
+	{1, crypto.MD5},
+	{2, crypto.SHA1},
+	{3, crypto.RIPEMD160},
+	{8, crypto.SHA256},
+	{9, crypto.SHA384},
+	{10, crypto.SHA512},
+	{11, crypto.SHA224},
+}
+
+// HashIdToHash returns a crypto.Hash which corresponds to the given OpenPGP
+// hash id.
+func HashIdToHash(id byte) (h crypto.Hash, ok bool) {
+	for _, m := range hashToHashIdMapping {
+		if m.id == id {
+			return m.hash, true
+		}
+	}
+	return 0, false
+}
+
+// HashIdToHash returns an OpenPGP hash id which corresponds the given Hash.
+func HashToHashId(h crypto.Hash) (id byte, ok bool) {
+	for _, m := range hashToHashIdMapping {
+		if m.hash == h {
+			return m.id, true
+		}
+	}
+	return 0, false
+}