95 lines
1.8 KiB
Go
95 lines
1.8 KiB
Go
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package crypto
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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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"errors"
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)
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const (
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aesNonceLength = 12
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)
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func EncryptSymmetric(key, plaintext []byte) ([]byte, error) {
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block, err := aes.NewCipher(key)
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if err != nil {
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return nil, err
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}
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// Never use more than 2^32 random nonces with a given key because of the risk of a repeat.
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salt, err := generateSecureRandomData(aesNonceLength)
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if err != nil {
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return nil, 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, err
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}
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encrypted, err := aesgcm.Seal(nil, salt, plaintext, nil), nil
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if err != nil {
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return nil, err
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}
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return append(encrypted, salt...), nil
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}
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func DecryptSymmetric(key []byte, cyphertext []byte) ([]byte, error) {
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// symmetric messages are expected to contain the 12-byte nonce at the end of the payload
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if len(cyphertext) < aesNonceLength {
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return nil, errors.New("missing salt or invalid payload in symmetric message")
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}
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salt := cyphertext[len(cyphertext)-aesNonceLength:]
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block, err := aes.NewCipher(key)
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if err != nil {
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return nil, 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, err
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}
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decrypted, err := aesgcm.Open(nil, salt, cyphertext[:len(cyphertext)-aesNonceLength], nil)
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if err != nil {
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return nil, err
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}
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return decrypted, nil
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}
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func containsOnlyZeros(data []byte) bool {
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for _, b := range data {
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if b != 0 {
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return false
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}
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}
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return true
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}
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func validateDataIntegrity(k []byte, expectedSize int) bool {
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if len(k) != expectedSize {
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return false
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}
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if containsOnlyZeros(k) {
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return false
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}
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return true
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}
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func generateSecureRandomData(length int) ([]byte, error) {
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res := make([]byte, length)
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_, err := rand.Read(res)
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if err != nil {
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return nil, err
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}
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if !validateDataIntegrity(res, length) {
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return nil, errors.New("crypto/rand failed to generate secure random data")
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}
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return res, nil
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}
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