aes-256-gcm从PHP到Golang的解密

我在PHP中使用了一个加密函数

function Encrypt(?string $Content, string $Key): string {
    return openssl_encrypt($Content, 'aes-256-gcm', $Key, OPENSSL_RAW_DATA, $IV = random_bytes(16), $Tag, '', 16) . $IV . $Tag;
}

与解密函数配对

function Decrypt(?string $Ciphertext, string $Key): ?string {
    if (strlen($Ciphertext) < 32)
        return null;

    $Content = substr($Ciphertext, 0, -32);
    $IV = substr($Ciphertext, -32, -16);
    $Tag = substr($Ciphertext, -16);

    try {
        return openssl_decrypt($Content, 'aes-256-gcm', $Key, OPENSSL_RAW_DATA, $IV, $Tag);
    } catch (Exception $e) {
        return null;
    }
}

我将加密函数中加密的数据存储到数据库中,现在我正试图在Go中解密这些值,但是我得到了 cipher: message authentication failed 我不知道我错过了什么。

c := []byte(`encrypted bytes of sorts`) // the bytes from the db

content := c[:len(c)-32]
iv := c[len(c)-32 : len(c)-16]
tag := c[len(c)-16:]

block, err := aes.NewCipher(key[:32])
if err != nil {
    panic(err.Error())
}

aesgcm, err := cipher.NewGCMWithNonceSize(block, 16)
if err != nil {
    panic(err.Error())
}

fmt.Println(aesgcm.NonceSize(), aesgcm.Overhead()) // making sure iv and tag are both 16 bytes

plaintext, err := aesgcm.Open(nil, iv, append(content, tag...), nil)
if err != nil {
    panic(err.Error())
}

值得注意的是,我使用的密钥不是32字节(它要大得多),因为我不知道需要/应该是32字节的密钥,所以我不完全确定PHP用它做了什么(比如将它截断为32字节,而用32字节的输出对它进行散列,而不是其他东西)。

在看 Open

// copied from C:\Go\src\crypto\cipher\gcm.go, Go version 1.11
func (g *gcm) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
    if len(nonce) != g.nonceSize {
        panic("cipher: incorrect nonce length given to GCM")
    }

    if len(ciphertext) < gcmTagSize {
        return nil, errOpen
    }
    if uint64(len(ciphertext)) > ((1<<32)-2)*uint64(g.cipher.BlockSize())+gcmTagSize {
        return nil, errOpen
    }

    tag := ciphertext[len(ciphertext)-gcmTagSize:]
    ciphertext = ciphertext[:len(ciphertext)-gcmTagSize]

    var counter, tagMask [gcmBlockSize]byte
    g.deriveCounter(&counter, nonce)

    g.cipher.Encrypt(tagMask[:], counter[:])
    gcmInc32(&counter)

    var expectedTag [gcmTagSize]byte
    g.auth(expectedTag[:], ciphertext, data, &tagMask)

    ret, out := sliceForAppend(dst, len(ciphertext))

    if subtle.ConstantTimeCompare(expectedTag[:], tag) != 1 {
        // The AESNI code decrypts and authenticates concurrently, and
        // so overwrites dst in the event of a tag mismatch. That
        // behavior is mimicked here in order to be consistent across
        // platforms.
        for i := range out {
            out[i] = 0
        }
        return nil, errOpen
    }

    g.counterCrypt(out, ciphertext, &counter)

    return ret, nil
}

使用上述函数的PHP示例

$Key = 'outspoken outburst treading cramp cringing';

echo bin2hex($Enc = Encrypt('yeet', $Key)), '<br>'; // 924b3ba418f49edc1757f3fe88adcaa7ec4c1e7d15811fd0b712b0b091433073f6a38d7b
var_export(Decrypt($Enc, $Key)); // 'yeet'

c, err := hex.DecodeString(`924b3ba418f49edc1757f3fe88adcaa7ec4c1e7d15811fd0b712b0b091433073f6a38d7b`)
if err != nil {
    panic(err.Error())
}
key := []byte(`outspoken outburst treading cramp cringing`)

content := c[:len(c)-32]
iv := c[len(c)-32 : len(c)-16]
tag := c[len(c)-16:]

block, err := aes.NewCipher(key[:32])
if err != nil {
    panic(err.Error())
}

aesgcm, err := cipher.NewGCMWithNonceSize(block, 16)
if err != nil {
    panic(err.Error())
}

ciphertext := append(content, tag...) // or `ciphertext := content`, same error

plaintext, err := aesgcm.Open(nil, iv, ciphertext, nil)
if err != nil {
    panic(err.Error()) // panic: cipher: message authentication failed
}