From 646d2d54cea75ec550f015a9eb61ba1642730908 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Connes?= <cedric.connes@gmail.com>
Date: Tue, 26 May 2020 23:19:08 +0200
Subject: [PATCH] Replace ctrutil with cipherio for AES-CBC

---
 cia.go            |   4 +-
 ctrutil/cipher.go | 101 ----------------------------------------------
 go.mod            |   1 +
 3 files changed, 4 insertions(+), 102 deletions(-)
 delete mode 100644 ctrutil/cipher.go

diff --git a/cia.go b/cia.go
index 1a5ba93..b8f6138 100644
--- a/cia.go
+++ b/cia.go
@@ -10,6 +10,8 @@ import (
 	"io"
 	"io/ioutil"
 
+	"github.com/connesc/cipherio"
+
 	"github.com/connesc/ctrsigcheck/ctrutil"
 )
 
@@ -217,7 +219,7 @@ func CheckCIA(input io.Reader) (*CIA, error) {
 			}
 			contentIV := make([]byte, contentCipher.BlockSize())
 			binary.BigEndian.PutUint16(contentIV, uint16(content.Index))
-			data = ctrutil.NewCipherReader(data, cipher.NewCBCDecrypter(contentCipher, contentIV))
+			data = cipherio.NewBlockReader(data, cipher.NewCBCDecrypter(contentCipher, contentIV))
 		}
 
 		hash := sha256.New()
diff --git a/ctrutil/cipher.go b/ctrutil/cipher.go
deleted file mode 100644
index 8801aaf..0000000
--- a/ctrutil/cipher.go
+++ /dev/null
@@ -1,101 +0,0 @@
-package ctrutil
-
-import (
-	"crypto/cipher"
-	"io"
-)
-
-type cipherReader struct {
-	src       io.Reader
-	blockMode cipher.BlockMode
-	blockSize int
-	buf       []byte // used to store remaining bytes (before or after crypting)
-	crypted   int    // if > 0, then buf contains remaining crypted bytes
-	eof       bool
-}
-
-// NewCipherReader wraps the given Reader to add on-the-fly encryption or decryption using the
-// given BlockMode.
-//
-// The input must be aligned to the cipher block size: ErrUnexpectedEOF is returned if EOF is
-// reached in the middle of a block.
-//
-// This Reader limits buffering and copies to the minimum: lookahead can only happen if the last
-// requested block is incomplete. In that case, it is guaranteed that the wrapped Reader is never
-// read beyond the end of the incomplete block. In particular, it is safe to stop reading from this
-// Reader at a block boundary and then start using the wrapped Reader for something else.
-func NewCipherReader(src io.Reader, blockMode cipher.BlockMode) io.Reader {
-	blockSize := blockMode.BlockSize()
-
-	return &cipherReader{
-		src:       src,
-		blockMode: blockMode,
-		blockSize: blockSize,
-		buf:       make([]byte, 0, blockSize),
-		crypted:   0,
-		eof:       false,
-	}
-}
-
-func (r *cipherReader) Read(p []byte) (int, error) {
-	count := 0
-
-	if r.crypted > 0 {
-		copied := copy(p, r.buf[r.blockSize-r.crypted:])
-		p = p[copied:]
-		count += copied
-		r.crypted -= copied
-		if r.crypted > 0 {
-			return count, nil
-		}
-		r.buf = r.buf[:0]
-	}
-
-	if r.eof {
-		return count, io.EOF
-	}
-	if len(p) == 0 {
-		return count, nil
-	}
-
-	if len(p) < r.blockSize {
-		n, err := r.src.Read(r.buf[len(r.buf):r.blockSize])
-		r.buf = r.buf[:len(r.buf)+n]
-		if len(r.buf) == r.blockSize {
-			r.blockMode.CryptBlocks(r.buf, r.buf)
-			copied := copy(p, r.buf)
-			count += copied
-			r.crypted = r.blockSize - copied
-		}
-		if err == io.EOF {
-			if r.crypted > 0 {
-				err = nil
-				r.eof = true
-			} else if len(r.buf) > 0 {
-				err = io.ErrUnexpectedEOF
-			}
-		}
-		return count, err
-	}
-
-	n, err := r.src.Read(p[len(r.buf):])
-	available := len(r.buf) + n
-	buffered := available % r.blockSize
-	crypted := available - buffered
-
-	if crypted > 0 {
-		copy(p, r.buf)
-		r.buf = r.buf[:0]
-		r.blockMode.CryptBlocks(p[:crypted], p[:crypted])
-		count += crypted
-	}
-
-	newlyBuffered := buffered - len(r.buf)
-	r.buf = r.buf[:buffered]
-	copy(r.buf[buffered-newlyBuffered:], p[available-newlyBuffered:])
-
-	if err == io.EOF && buffered > 0 {
-		err = io.ErrUnexpectedEOF
-	}
-	return count, err
-}
diff --git a/go.mod b/go.mod
index 6677af5..0b89fc8 100644
--- a/go.mod
+++ b/go.mod
@@ -3,6 +3,7 @@ module github.com/connesc/ctrsigcheck
 go 1.14
 
 require (
+	github.com/connesc/cipherio v0.1.0
 	github.com/spf13/cobra v1.0.0
 	github.com/spf13/pflag v1.0.3
 )