unipdf/core/security/ecb.go

/*
 * This file is subject to the terms and conditions defined in
 * file 'LICENSE.md', which is part of this source code package.
 */

package security

import (
	"crypto/cipher"

	"github.com/unidoc/unipdf/v3/common"
)

// ecb implements an Electronic Codebook encryption mode.
// This mode is used to compute or validate document permissions for R=6.
type ecb struct {
	b         cipher.Block
	blockSize int
}

func newECB(b cipher.Block) *ecb {
	return &ecb{
		b:         b,
		blockSize: b.BlockSize(),
	}
}

type ecbEncrypter ecb

func newECBEncrypter(b cipher.Block) cipher.BlockMode {
	return (*ecbEncrypter)(newECB(b))
}

func (x *ecbEncrypter) BlockSize() int { return x.blockSize }

func (x *ecbEncrypter) CryptBlocks(dst, src []byte) {
	if len(src)%x.blockSize != 0 {
		common.Log.Error("ERROR: ECB encrypt: input not full blocks")
		return
	}
	if len(dst) < len(src) {
		common.Log.Error("ERROR: ECB encrypt: output smaller than input")
		return
	}
	for len(src) > 0 {
		x.b.Encrypt(dst, src[:x.blockSize])
		src = src[x.blockSize:]
		dst = dst[x.blockSize:]
	}
}

type ecbDecrypter ecb

func newECBDecrypter(b cipher.Block) cipher.BlockMode {
	return (*ecbDecrypter)(newECB(b))
}

func (x *ecbDecrypter) BlockSize() int { return x.blockSize }

func (x *ecbDecrypter) CryptBlocks(dst, src []byte) {
	if len(src)%x.blockSize != 0 {
		common.Log.Error("ERROR: ECB decrypt: input not full blocks")
		return
	}
	if len(dst) < len(src) {
		common.Log.Error("ERROR: ECB decrypt: output smaller than input")
		return
	}
	for len(src) > 0 {
		x.b.Decrypt(dst, src[:x.blockSize])
		src = src[x.blockSize:]
		dst = dst[x.blockSize:]
	}
}