Refactor away cipherio

Doing the decryption by hand isn't actually that difficult and fixes the
failing test case too.

go.mod

@@ -6,7 +6,6 @@ require (
 	github.com/andybalholm/brotli v1.0.5
 	github.com/bodgit/plumbing v1.3.0
 	github.com/bodgit/windows v1.0.1
-	github.com/connesc/cipherio v0.2.1
 	github.com/hashicorp/go-multierror v1.1.1
 	github.com/klauspost/compress v1.16.4
 	github.com/pierrec/lz4/v4 v4.1.17

go.sum

@@ -28,8 +28,6 @@ github.com/chzyer/logex v1.1.10/go.mod h1:+Ywpsq7O8HXn0nuIou7OrIPyXbp3wmkHB+jjWR
 github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e/go.mod h1:nSuG5e5PlCu98SY8svDHJxuZscDgtXS6KTTbou5AhLI=
 github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1/go.mod h1:Q3SI9o4m/ZMnBNeIyt5eFwwo7qiLfzFZmjNmxjkiQlU=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
-github.com/connesc/cipherio v0.2.1 h1:FGtpTPMbKNNWByNrr9aEBtaJtXjqOzkIXNYJp6OEycw=
-github.com/connesc/cipherio v0.2.1/go.mod h1:ukY0MWJDFnJEbXMQtOcn2VmTpRfzcTz4OoVrWGGJZcA=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -45,8 +43,6 @@ github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfb
 github.com/golang/mock v1.2.0/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=
 github.com/golang/mock v1.3.1/go.mod h1:sBzyDLLjw3U8JLTeZvSv8jJB+tU5PVekmnlKIyFUx0Y=
 github.com/golang/mock v1.4.0/go.mod h1:UOMv5ysSaYNkG+OFQykRIcU/QvvxJf3p21QfJ2Bt3cw=
-github.com/golang/mock v1.4.3 h1:GV+pQPG/EUUbkh47niozDcADz6go/dUwhVzdUQHIVRw=
-github.com/golang/mock v1.4.3/go.mod h1:UOMv5ysSaYNkG+OFQykRIcU/QvvxJf3p21QfJ2Bt3cw=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.2/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=

internal/aes7z/reader.go

@@ -1,28 +1,28 @@
 package aes7z
 
 import (
+	"bytes"
 	"crypto/aes"
 	"crypto/cipher"
 	"errors"
 	"io"
-
-	"github.com/connesc/cipherio"
 )
 
 var errProperties = errors.New("aes7z: not enough properties")
 
 type readCloser struct {
 	rc       io.ReadCloser
-	br       io.Reader
 	salt, iv []byte
 	cycles   int
+	cbc      cipher.BlockMode
+	buf      bytes.Buffer
 }
 
 func (rc *readCloser) Close() error {
 	var err error
 	if rc.rc != nil {
 		err = rc.rc.Close()
-		rc.rc, rc.br = nil, nil
+		rc.rc = nil
 	}
 
 	return err
@@ -34,7 +34,7 @@ func (rc *readCloser) Password(p string) error {
 		return err
 	}
 
-	rc.br = cipherio.NewBlockReader(rc.rc, cipher.NewCBCDecrypter(block, rc.iv))
+	rc.cbc = cipher.NewCBCDecrypter(block, rc.iv)
 
 	return nil
 }
@@ -44,11 +44,27 @@ func (rc *readCloser) Read(p []byte) (int, error) {
 		return 0, errors.New("aes7z: Read after Close")
 	}
 
-	if rc.br == nil {
+	if rc.cbc == nil {
 		return 0, errors.New("aes7z: no password set")
 	}
 
-	return rc.br.Read(p)
+	var block [aes.BlockSize]byte
+
+	for rc.buf.Len() < len(p) {
+		_, err := io.ReadFull(rc.rc, block[:])
+		if err != nil {
+			return 0, err
+		}
+
+		rc.cbc.CryptBlocks(block[:], block[:])
+
+		_, err = rc.buf.Write(block[:])
+		if err != nil {
+			return 0, err
+		}
+	}
+
+	return rc.buf.Read(p)
 }
 
 // NewReader returns a new AES-256-CBC & SHA-256 io.ReadCloser. The Password
@@ -78,7 +94,7 @@ func NewReader(p []byte, _ uint64, readers []io.ReadCloser) (io.ReadCloser, erro
 	}
 
 	rc.salt = p[2 : 2+salt]
-	rc.iv = make([]byte, 16)
+	rc.iv = make([]byte, aes.BlockSize)
 	copy(rc.iv, p[2+salt:])
 
 	rc.cycles = int(p[0] & 0x3f)