Forward-port to Go 1.12.7

LICENSE

@@ -0,0 +1,30 @@
+Copyright (c) 2009 The Go Authors. All rights reserved.
+Copyright (c) 2015 Alex Mullins
+Copyright (c) 2016 Yakub Kristianto
+Copyright (c) 2019 Hilko Bengen
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

README.md

@@ -0,0 +1,14 @@
+# Go `archive/zip` plus encryption support
+
+[![GoDoc](https://godoc.org/github.com/hillu/go-archive-zip-crypto?status.svg)](https://godoc.org/github.com/hillu/go-archive-zip-crypto)
+[![Go Report Card](https://goreportcard.com/badge/github.com/hillu/go-archive-zip-crypto)](https://goreportcard.com/report/github.com/hillu/go-archive-zip-crypto)
+
+This is a fork of the `archive/zip` package from the Go standard
+library which adds support for both the legacy
+(insecure) ZIP encryption scheme and for newer AES-based encryption
+schemes introduced with WinZip. It is based on Go 1.14.
+
+This is based on work by [Alex Mullins](https://github.com/alexmullins/zip) and
+[Yakub Kristianto](https://github.com/yeka/zip). The forward-port was done to
+introduce bugfixes and enhancements, such as missing support for large
+(>= 4GB) ZIP files like those distributed by [VirusShare](https://virusshare.com/).

crypto.go

@@ -19,7 +19,14 @@ import (
 	"golang.org/x/crypto/pbkdf2"
 )
 
+type EncryptionMethod int
+
 const (
+	StandardEncryption EncryptionMethod = 1
+	AES128Encryption   EncryptionMethod = 2
+	AES192Encryption   EncryptionMethod = 3
+	AES256Encryption   EncryptionMethod = 4
+
 	// AES key lengths
 	aes128 = 16
 	aes192 = 24
@@ -379,13 +386,14 @@ func encryptStream(key []byte, w io.Writer) (io.Writer, error) {
 // newEncryptionWriter returns an io.Writer that when written to, 1. writes
 // out the salt, 2. writes out pwv, and 3. writes out authenticated, encrypted
 // data. The authcode will be written out in fileWriter.close().
-func newEncryptionWriter(w io.Writer, password passwordFn, fw *fileWriter) (io.Writer, error) {
-	var salt [16]byte
+func newEncryptionWriter(w io.Writer, password passwordFn, fw *fileWriter, aesstrength byte) (io.Writer, error) {
+	keysize := aesKeyLen(aesstrength)
+	salt := make([]byte, keysize/2)
 	_, err := rand.Read(salt[:])
 	if err != nil {
 		return nil, errors.New("zip: unable to generate random salt")
 	}
-	ekey, akey, pwv := generateKeys(password(), salt[:], aes256)
+	ekey, akey, pwv := generateKeys(password(), salt[:], keysize)
 	fw.hmac = hmac.New(sha1.New, akey)
 	aw := &authWriter{
 		hmac: fw.hmac,
@@ -420,15 +428,27 @@ func (h *FileHeader) writeWinZipExtra() {
 	// total size is 11 bytes
 	var buf [11]byte
 	eb := writeBuf(buf[:])
-	eb.uint16(winzipAesExtraId) // 0x9901
+	eb.uint16(winzipAesExtraID) // 0x9901
 	eb.uint16(7)                // following data size is 7
 	eb.uint16(2)                // ae 2
 	eb.uint16(0x4541)           // "AE"
-	eb.uint8(3)                 // aes256
+	eb.uint8(h.aesStrength)     // aes256
 	eb.uint16(h.Method)         // original compression method
 	h.Extra = append(h.Extra, buf[:]...)
 }
 
+func (h *FileHeader) setEncryptionMethod(enc EncryptionMethod) {
+	h.encryption = enc
+	switch enc {
+	case AES128Encryption:
+		h.aesStrength = 1
+	case AES192Encryption:
+		h.aesStrength = 2
+	case AES256Encryption:
+		h.aesStrength = 3
+	}
+}
+
 func (h *FileHeader) setEncryptionBit() {
 	h.Flags |= 0x1
 }
@@ -452,11 +472,12 @@ type passwordFn func() []byte
 // contents will be encrypted with AES-256 using the given password. The
 // file's contents must be written to the io.Writer before the next call
 // to Create, CreateHeader, or Close.
-func (w *Writer) Encrypt(name string, password string) (io.Writer, error) {
+func (w *Writer) Encrypt(name string, password string, enc EncryptionMethod) (io.Writer, error) {
 	fh := &FileHeader{
 		Name:   name,
 		Method: Deflate,
 	}
 	fh.SetPassword(password)
+	fh.setEncryptionMethod(enc)
 	return w.CreateHeader(fh)
 }