java - 在 mbedtls Diffie-Hellman 中使用来自 Java 的 DER key

Question

我有一个 Java 应用程序正在为 Diffie-Hellman key 交换生成 key 。生成这些 key ，并导出公钥如下:

/*
 * Alice creates her own DH key pair with 2048-bit key size
 */
System.out.println("ALICE: Generate DH keypair ...");
KeyPairGenerator aliceKpairGen = KeyPairGenerator.getInstance("DH");
aliceKpairGen.initialize(2048);
KeyPair aliceKpair = aliceKpairGen.generateKeyPair();

// Alice creates and initializes her DH KeyAgreement object
System.out.println("ALICE: Initialization ...");
KeyAgreement aliceKeyAgree = KeyAgreement.getInstance("DH");
aliceKeyAgree.init(aliceKpair.getPrivate());

// Alice encodes her public key, and sends it over to Bob.
byte[] alicePubKeyEnc = aliceKpair.getPublic().getEncoded();

包含在 alicePubKeyEnc 中的是我发送到我的 C++ 应用程序的公钥。据我了解，此数据是我的 DHE 参数的编码 DER key 。另一方面，我正尝试将此 key 与 mbedtls 一起使用，如下所示:

// An example DER (?) key from Java.
unsigned char buf[] = {
    0x30, 0x82, 0x02, 0x28, 0x30, 0x82, 0x01, 0x1b, 0x06, 0x09, 0x2a, 0x86,
    0x48, 0x86, 0xf7, 0x0d, 0x01, 0x03, 0x01, 0x30, 0x82, 0x01, 0x0c, 0x02,
    0x82, 0x01, 0x01, 0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
    0xc9, 0x0f, 0xda, 0xa2, 0x21, 0x68, 0xc2, 0x34, 0xc4, 0xc6, 0x62, 0x8b,
    0x80, 0xdc, 0x1c, 0xd1, 0x29, 0x02, 0x4e, 0x08, 0x8a, 0x67, 0xcc, 0x74,
    0x02, 0x0b, 0xbe, 0xa6, 0x3b, 0x13, 0x9b, 0x22, 0x51, 0x4a, 0x08, 0x79,
    0x8e, 0x34, 0x04, 0xdd, 0xef, 0x95, 0x19, 0xb3, 0xcd, 0x3a, 0x43, 0x1b,
    0x30, 0x2b, 0x0a, 0x6d, 0xf2, 0x5f, 0x14, 0x37, 0x4f, 0xe1, 0x35, 0x6d,
    0x6d, 0x51, 0xc2, 0x45, 0xe4, 0x85, 0xb5, 0x76, 0x62, 0x5e, 0x7e, 0xc6,
    0xf4, 0x4c, 0x42, 0xe9, 0xa6, 0x37, 0xed, 0x6b, 0x0b, 0xff, 0x5c, 0xb6,
    0xf4, 0x06, 0xb7, 0xed, 0xee, 0x38, 0x6b, 0xfb, 0x5a, 0x89, 0x9f, 0xa5,
    0xae, 0x9f, 0x24, 0x11, 0x7c, 0x4b, 0x1f, 0xe6, 0x49, 0x28, 0x66, 0x51,
    0xec, 0xe4, 0x5b, 0x3d, 0xc2, 0x00, 0x7c, 0xb8, 0xa1, 0x63, 0xbf, 0x05,
    0x98, 0xda, 0x48, 0x36, 0x1c, 0x55, 0xd3, 0x9a, 0x69, 0x16, 0x3f, 0xa8,
    0xfd, 0x24, 0xcf, 0x5f, 0x83, 0x65, 0x5d, 0x23, 0xdc, 0xa3, 0xad, 0x96,
    0x1c, 0x62, 0xf3, 0x56, 0x20, 0x85, 0x52, 0xbb, 0x9e, 0xd5, 0x29, 0x07,
    0x70, 0x96, 0x96, 0x6d, 0x67, 0x0c, 0x35, 0x4e, 0x4a, 0xbc, 0x98, 0x04,
    0xf1, 0x74, 0x6c, 0x08, 0xca, 0x18, 0x21, 0x7c, 0x32, 0x90, 0x5e, 0x46,
    0x2e, 0x36, 0xce, 0x3b, 0xe3, 0x9e, 0x77, 0x2c, 0x18, 0x0e, 0x86, 0x03,
    0x9b, 0x27, 0x83, 0xa2, 0xec, 0x07, 0xa2, 0x8f, 0xb5, 0xc5, 0x5d, 0xf0,
    0x6f, 0x4c, 0x52, 0xc9, 0xde, 0x2b, 0xcb, 0xf6, 0x95, 0x58, 0x17, 0x18,
    0x39, 0x95, 0x49, 0x7c, 0xea, 0x95, 0x6a, 0xe5, 0x15, 0xd2, 0x26, 0x18,
    0x98, 0xfa, 0x05, 0x10, 0x15, 0x72, 0x8e, 0x5a, 0x8a, 0xac, 0xaa, 0x68,
    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x02, 0x01, 0x02, 0x02,
    0x02, 0x04, 0x00, 0x03, 0x82, 0x01, 0x05, 0x00, 0x02, 0x82, 0x01, 0x00,
    0x2f, 0x6e, 0xa3, 0xd8, 0x5c, 0xca, 0x06, 0x99, 0xbd, 0x35, 0x90, 0xb5,
    0xc3, 0x11, 0xa6, 0x48, 0x5b, 0x5a, 0xe9, 0x14, 0xac, 0x4a, 0xed, 0x2d,
    0x46, 0xb1, 0x6b, 0xc7, 0x5b, 0x88, 0xc6, 0xa7, 0x51, 0x07, 0xa0, 0x4d,
    0x5f, 0xc0, 0x32, 0x54, 0x9d, 0x63, 0x35, 0xa2, 0x3b, 0x6a, 0x9a, 0x0a,
    0xb9, 0x46, 0xff, 0x0b, 0x78, 0x5d, 0xa7, 0x17, 0x94, 0x58, 0x28, 0x28,
    0xf2, 0xa0, 0xea, 0x3a, 0xf0, 0xe8, 0x8f, 0xc2, 0xa1, 0x7c, 0xb1, 0x50,
    0x38, 0xb7, 0x01, 0xe1, 0x69, 0x42, 0x30, 0x1e, 0x06, 0x06, 0x06, 0x17,
    0x46, 0xc8, 0x1f, 0xb1, 0xb4, 0xd2, 0xff, 0xf1, 0x32, 0xdc, 0xc2, 0xfc,
    0x2c, 0x15, 0xe4, 0xfe, 0xae, 0xb2, 0x1f, 0x8b, 0x20, 0x29, 0x87, 0xbe,
    0x31, 0x8c, 0xf2, 0x01, 0x95, 0x51, 0x35, 0x76, 0x4c, 0x83, 0xe4, 0x06,
    0x46, 0x96, 0x62, 0x42, 0x2f, 0x23, 0xb4, 0xb7, 0xc7, 0x41, 0x4b, 0x4e,
    0xf5, 0xab, 0x20, 0xb0, 0x45, 0x27, 0x52, 0x64, 0x63, 0x18, 0x87, 0x72,
    0xa7, 0x41, 0x80, 0xbd, 0x15, 0x4d, 0xa8, 0x48, 0x69, 0x69, 0x8b, 0x64,
    0x38, 0x03, 0xa7, 0x72, 0xf7, 0xeb, 0x2b, 0xdd, 0x19, 0x2d, 0x63, 0x3a,
    0xa6, 0x1b, 0x6f, 0xcc, 0x81, 0x14, 0xde, 0x29, 0xd9, 0x55, 0x66, 0xd1,
    0x95, 0x8d, 0x2f, 0x15, 0x5e, 0x29, 0xad, 0xf8, 0x82, 0xf0, 0x68, 0xac,
    0x65, 0xf7, 0x54, 0x4f, 0x3e, 0x52, 0x64, 0xe8, 0x28, 0x52, 0x0f, 0x7c,
    0xbe, 0xc4, 0xf2, 0x20, 0x40, 0x97, 0xfa, 0x0a, 0x78, 0x5b, 0x1d, 0xf8,
    0xdb, 0x15, 0x02, 0xbe, 0xc3, 0xf0, 0xb0, 0x3a, 0xda, 0x6a, 0xe6, 0x5f,
    0x74, 0x48, 0x74, 0x0e, 0xe9, 0x1d, 0x02, 0xda, 0x25, 0x37, 0x4f, 0x41,
    0x11, 0x63, 0x32, 0x93, 0x44, 0xfe, 0x5b, 0x3a, 0x7e, 0x25, 0xcc, 0x9f,
    0xd5, 0x99, 0x41, 0x9f, 0x00
};

size_t size = 557; // 556 + NULL terminating byte per the docs.

mbedtls_dhm_context ctx;
mbedtls_dhm_init(&ctx);
int res = mbedtls_dhm_parse_dhm(&ctx, buf, size);

if (res != 0) {
    printf("FAIL\n", -res);
}

res 产生负的非零值 (0xffffcc1e)。我检查了 mbedtls 中 x509 解析的错误代码，但找不到匹配的错误代码。

知道为什么我无法加载此证书吗？

更新

我更新了我的 C 代码以打印出 mbedtls 的相关错误消息:

0x0000023c4f9fb2b0 "DHM - The ASN.1 data is not formatted correctly : ASN1 - ASN1 tag was of an unexpected value"

所以我从我的 key 中获取了十六进制值并通过 http://lapo.it/asn1js/ 运行它(<-- 链接 key 的实际输出)指示我的 key 的某种结构，似乎 可以很好地解析 key 。也许这是我将 key 传递给 mbedtls 的方式的问题？

Answer 1

您将错误的内容传递给了 mbed TLS 的 mbedtls_dhm_parse_dhm。该函数需要 DER(或 PEM)编码的 DH 参数，而不是 key 。

使用 BouncyCaSTLe 的 DHParameter你可以像这样获得 DER 编码的参数:

DHParameterSpec dhParams = ((DHPublicKey) aliceKeyPair.getPublic()).getParams();
DHParameter dhP = new DHParameter(dhParams.getP(), dhParams.getG(), 0);
byte[] encodedParams = dhP.getEncoded(ASN1Encodable.DER);

这将为您提供字节，然后您可以将这些字节传递给 mbedtls_dhm_parse_dhm，可以是您现在正在做的原始字节，也可以是 PEM 编码，因为该函数也可以接受。请注意，我为 L 传递了 0，因为 mbed TLS 无论如何都会丢弃它。另请注意 getEncoded 会抛出异常，因此请务必处理异常。

完成 key 交换的步骤:

在 Java 中:

KeyPairGenerator aliceKpairGen = KeyPairGenerator.getInstance("DH");
aliceKpairGen.initialize(2048);
KeyPair aliceKpair = aliceKpairGen.generateKeyPair();
KeyAgreement aliceKeyAgree = KeyAgreement.getInstance("DH");
aliceKeyAgree.init(aliceKpair.getPrivate());
DHParameterSpec dhParams = ((DHPublicKey) aliceKpair.getPublic()).getParams();
DHParameter dhP = new DHParameter(dhParams.getP(), dhParams.getG(), 0);
byte[] encodedParams = dhP.getEncoded(ASN1Encodable.DER);
byte[] javaPub = ((DHPublicKey)aliceKeyPair.getPublic()).getY().toByteArray();

然后在 C++ 中:

mbedtls_dhm_context ctx;
mbedtls_dhm_init(&ctx);
...
mbedtls_dhm_parse_dhm(&ctx, encodedParams, encodedParamsLen);
...
uint_8t mbedtlspub[128];
mbedtls_dhm_make_public(&ctx, 128, mbedtlspub, sizeof(mbedtlspub), mbedtls_ctr_drbg_random, &rnd_info);
...
mbedtls_dhm_read_public(&ctx, javaPub, javaPubLen);
...
uint_8t mbedtlssecret[128];
mbedtls_dhm_calc_secret(&ctx, mbedtlssecret, (size_t)secret_len, &olen, mbedtls_ctr_drbg_random, &rnd_info);

回到 Java(假设您从前面的步骤中使用 Base64 对 mbedtlspub 进行了编码，但您可以随心所欲地进行):

byte[] yBinary = Base64.decodeBase64(mbedtlspub.getBytes()); 
BigInteger y = new BigInteger(yBinary); 
DHPublicKeySpec dhPublicKeySpec = new DHPublicKeySpec(y, dhParams.getP(), dhParams.getG()); 
KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM); 
DHPublicKey mbedtlsPubKey = (DHPublicKey) KeyFactory.generatePublic(dhPublicKeySpec);
aliceKeyAgree.doPhase(mbedtlsPubKey, true);
byte[] javaSecretKey = aliceKeyAgree.generateSecret();

这就完成了 key 交换，此时 mbedtlssecret 和 javaSecretKey 应该匹配。所以传递的数据是encodedParams和javaPub(来自Java)和mbedtlspub(来自C++)。我省略了一些细节以专注于核心步骤。另请注意，其中许多函数要么返回错误代码，要么抛出异常，因此请小心使用它们。