129 lines
3.3 KiB
Go
129 lines
3.3 KiB
Go
package paddingx
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import (
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"bytes"
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"errors"
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"strings"
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)
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const (
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PKCS5 = "PKCS5"
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PKCS7 = "PKCS7"
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ZERO = "ZERO"
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ANSIX923 = "ANSIX923"
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)
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func Pad(data []byte, blockSize int, mode string) ([]byte, error) {
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if blockSize <= 0 {
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return nil, errors.New("block size must be greater than zero")
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}
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switch normalizeMode(mode) {
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case "", PKCS7:
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return PKCS7Padding(data, blockSize), nil
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case PKCS5:
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// Compatibility mode: historically PKCS5 was used generically in this project.
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return PKCS7Padding(data, blockSize), nil
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case ZERO:
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return zeroPadding(data, blockSize), nil
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case ANSIX923:
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return ansiX923Padding(data, blockSize), nil
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default:
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return nil, errors.New("padding type not supported")
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}
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}
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func Unpad(data []byte, blockSize int, mode string) ([]byte, error) {
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if blockSize <= 0 {
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return nil, errors.New("block size must be greater than zero")
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}
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switch normalizeMode(mode) {
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case "", PKCS7:
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return PKCS7Unpadding(data, blockSize)
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case PKCS5:
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// Compatibility mode: historically PKCS5 was used generically in this project.
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return PKCS7Unpadding(data, blockSize)
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case ZERO:
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return zeroUnpadding(data)
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case ANSIX923:
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return ansiX923Unpadding(data, blockSize)
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default:
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return nil, errors.New("padding type not supported")
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}
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}
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func PKCS7Padding(data []byte, blockSize int) []byte {
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padding := blockSize - len(data)%blockSize
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padText := bytes.Repeat([]byte{byte(padding)}, padding)
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return append(data, padText...)
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}
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func PKCS7Unpadding(data []byte, blockSize int) ([]byte, error) {
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if len(data) == 0 || len(data)%blockSize != 0 {
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return nil, errors.New("invalid PKCS7 padding")
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}
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padding := int(data[len(data)-1])
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if padding <= 0 || padding > blockSize || padding > len(data) {
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return nil, errors.New("invalid PKCS7 padding")
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}
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for i := len(data) - padding; i < len(data); i++ {
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if int(data[i]) != padding {
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return nil, errors.New("invalid PKCS7 padding")
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}
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}
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return data[:len(data)-padding], nil
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}
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func PKCS5Padding(data []byte) []byte {
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return PKCS7Padding(data, 8)
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}
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func PKCS5Unpadding(data []byte) ([]byte, error) {
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return PKCS7Unpadding(data, 8)
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}
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func zeroPadding(data []byte, blockSize int) []byte {
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padding := blockSize - len(data)%blockSize
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if padding == blockSize {
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return data
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}
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return append(data, bytes.Repeat([]byte{0x00}, padding)...)
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}
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func zeroUnpadding(data []byte) ([]byte, error) {
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idx := len(data)
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for idx > 0 && data[idx-1] == 0x00 {
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idx--
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}
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return data[:idx], nil
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}
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func ansiX923Padding(data []byte, blockSize int) []byte {
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padding := blockSize - len(data)%blockSize
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if padding == 0 {
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padding = blockSize
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}
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pad := make([]byte, padding)
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pad[len(pad)-1] = byte(padding)
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return append(data, pad...)
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}
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func ansiX923Unpadding(data []byte, blockSize int) ([]byte, error) {
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if len(data) == 0 || len(data)%blockSize != 0 {
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return nil, errors.New("invalid ANSI X9.23 padding")
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}
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padding := int(data[len(data)-1])
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if padding <= 0 || padding > blockSize || padding > len(data) {
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return nil, errors.New("invalid ANSI X9.23 padding")
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}
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for i := len(data) - padding; i < len(data)-1; i++ {
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if data[i] != 0x00 {
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return nil, errors.New("invalid ANSI X9.23 padding")
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}
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}
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return data[:len(data)-padding], nil
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}
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func normalizeMode(mode string) string {
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return strings.ToUpper(strings.TrimSpace(mode))
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}
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