96 lines
2.3 KiB
Go
96 lines
2.3 KiB
Go
package andotp
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import (
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"crypto/aes"
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"crypto/cipher"
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"crypto/rand"
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"crypto/sha1"
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"encoding/binary"
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"fmt"
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"math/big"
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"golang.org/x/crypto/pbkdf2"
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)
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const (
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ivLen = 12
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keyLen = 32
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iterationLen = 4
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saltLen = 12
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maxIterations = 160000
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minIterations = 140000
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)
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func Encrypt(password, plaintext []byte) ([]byte, error) {
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iter := make([]byte, iterationLen)
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iv := make([]byte, ivLen)
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salt := make([]byte, saltLen)
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maxMinIterationsSubtracted, err := rand.Int(rand.Reader, big.NewInt(int64(maxIterations-minIterations)))
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if err != nil {
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return nil, fmt.Errorf("rand.Int: %w", err)
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}
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iterations := int(maxMinIterationsSubtracted.Int64() + minIterations)
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binary.BigEndian.PutUint32(iter, uint32(iterations))
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_, err = rand.Read(iv)
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if err != nil {
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return nil, fmt.Errorf("rand.Read: %w", err)
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}
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_, err = rand.Read(salt)
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if err != nil {
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return nil, fmt.Errorf("rand.Read: %w", err)
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}
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secretKey := pbkdf2.Key(password, salt, iterations, keyLen, sha1.New)
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block, err := aes.NewCipher(secretKey)
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if err != nil {
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return nil, fmt.Errorf("aes.NewCipher: %w", err)
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}
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aesGCM, err := cipher.NewGCM(block)
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if err != nil {
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return nil, fmt.Errorf("cipher.NewGCM: %w", err)
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}
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cipherText := aesGCM.Seal(nil, iv, plaintext, nil)
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finalCipher := make([]byte, 0, len(iter)+len(salt)+len(iv)+len(cipherText))
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finalCipher = append(finalCipher, iter...)
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finalCipher = append(finalCipher, salt...)
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finalCipher = append(finalCipher, iv...)
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finalCipher = append(finalCipher, cipherText...)
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return finalCipher, nil
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}
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func Decrypt(password, text []byte) ([]byte, error) {
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iterations := text[:iterationLen]
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salt := text[iterationLen : iterationLen+saltLen]
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iv := text[iterationLen+saltLen : iterationLen+saltLen+ivLen]
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cipherText := text[iterationLen+saltLen+ivLen:]
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iter := int(binary.BigEndian.Uint32(iterations))
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secretKey := pbkdf2.Key(password, salt, iter, keyLen, sha1.New)
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block, err := aes.NewCipher(secretKey)
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if err != nil {
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return nil, fmt.Errorf("aes.NewCipher: %w", err)
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}
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aesGCM, err := cipher.NewGCM(block)
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if err != nil {
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return nil, fmt.Errorf("cipher.NewGCM: %w", err)
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}
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plaintext, err := aesGCM.Open(nil, iv, cipherText, nil)
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if err != nil {
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return nil, fmt.Errorf("aesGCM.Open: %w", err)
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}
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return plaintext, nil
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}
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