Make repository work with go get

padding/padding.go

@@ -0,0 +1,46 @@
+// Package padding adds and removes padding for AES-CBC mode.
+//
+// Copyright (c) 2013 CloudFlare, Inc.
+
+package padding
+
+import "errors"
+
+// The final byte of a padded []byte indicates the number of padding
+// bytes that were added. The padding bytes are always NUL bytes and
+// up to 16 bytes may be added.
+//
+// Examples:
+//
+// 1. Data to be padded has a length divisible by 16. 16 bytes will be
+// added where the first 15 are 0x00 and the final byte is 0x10.
+//
+// 2. Data to be padded has a length with remainder 15 when divided by
+// 16. One byte will be added and that byte will be 0x01 (indicating
+// one byte of padding).
+//
+// 3. Data to be padded has a length with remainder 2 when divided by
+// 16. 14 bytes will be added. The first 13 will be 0x00 and then final
+// byte will be 0x0e.
+//
+// Removing padding is trivial: the number of bytes specified by the
+// final byte are removed.
+
+// RemovePadding removes padding from data that was added with
+// AddPadding
+func RemovePadding(b []byte) ([]byte, error) {
+	l := int(b[len(b)-1])
+	if l > 16 {
+		return nil, errors.New("Padding incorrect")
+	}
+
+	return b[:len(b)-l], nil
+}
+
+// AddPadding adds padding to a block of data
+func AddPadding(b []byte) []byte {
+	l := 16 - len(b)%16
+	padding := make([]byte, l)
+	padding[l-1] = byte(l)
+	return append(b, padding...)
+}

padding/padding_test.go

@@ -0,0 +1,72 @@
+// padding_test.go: tests for padding.go
+//
+// Copyright (c) 2013 CloudFlare, Inc.
+
+package padding
+
+import (
+	"bytes"
+	"testing"
+)
+
+func assert(t *testing.T, b bool) {
+	if !b {
+		t.Fail()
+	}
+}
+
+func TestAddPadding(t *testing.T) {
+	b := make([]byte, 16)
+	c := AddPadding(b)
+	assert(t, len(c) == 32)
+	assert(t, c[31] == 16)
+
+	b = make([]byte, 32)
+	c = AddPadding(b)
+	assert(t, len(c) == 48)
+	assert(t, c[47] == 16)
+
+	b = make([]byte, 1)
+	c = AddPadding(b)
+	assert(t, len(c) == 16)
+	assert(t, c[15] == 15)
+
+	b = make([]byte, 15)
+	c = AddPadding(b)
+	assert(t, len(c) == 16)
+	assert(t, c[15] == 1)
+}
+
+func TestRemovePadding(t *testing.T) {
+	b := []byte("0123456789ABCDEF")
+	c := AddPadding(b)
+	assert(t, len(c) == 32)
+	assert(t, c[31] == 16)
+	assert(t, bytes.Compare(c[:16], b[:16]) == 0)
+	d, err := RemovePadding(c)
+	assert(t, err == nil)
+	assert(t, len(d) == 16)
+	assert(t, bytes.Compare(b, d) == 0)
+
+	b = []byte("0123456789")
+	c = AddPadding(b)
+	assert(t, len(c) == 16)
+	assert(t, c[15] == 6)
+	assert(t, bytes.Compare(c[:10], b[:10]) == 0)
+	d, err = RemovePadding(c)
+	assert(t, err == nil)
+	assert(t, len(d) == 10)
+	assert(t, bytes.Compare(b, d) == 0)
+}
+
+func TestDetectBadPadding(t *testing.T) {
+	b := []byte("0123456789ABCDEF")
+	c := AddPadding(b)
+	assert(t, len(c) == 32)
+	assert(t, c[31] == 16)
+	assert(t, bytes.Compare(c[:16], b[:16]) == 0)
+	c[31] = 42
+	d, err := RemovePadding(c)
+	assert(t, err != nil)
+	assert(t, d == nil)
+}