Hmac Sha256错误的结果值AWS-Java

Question

public static void main(String[] args) throws SignatureException {
    String data = "GET"+"\n"+"webservices.amazon.com"+"\n"+"/onca/xml"+"\n"+"AWSAccessKeyId=AKIAIOSFODNN7EXAMPLE&ItemId=0679722769&Operation=ItemLookup&ResponeGroup=ItemAttributes%2COffers%2CImages%2CReviews&Service=AWSECommerceService&Timestamp=2009-01-01T12%3A00%3A00Z&Version=2009-01-06";
    String key = "1234567890";
    String result = calculateRFC2104HMAC(data, key);
    System.out.println(result);

}

private static final String HMAC_SHA_ALGORITHM = "HmacSHA256";


public static String calculateRFC2104HMAC(String data, String key)throws java.security.SignatureException{
    String result;
    try {

    // get an hmac_sha256 key from the raw key bytes
    SecretKeySpec signingKey = new SecretKeySpec(key.getBytes("UTF-8"), HMAC_SHA_ALGORITHM);

    // get an hmac_sha256 Mac instance and initialize with the signing key
    Mac mac = Mac.getInstance(HMAC_SHA_ALGORITHM);
    mac.init(signingKey);

    // compute the hmac256 on input data bytes
    byte[] rawHmac = mac.doFinal(data.getBytes("UTF-8"));

    // base64-encode the hmac256
    result = Base64.encodeBase64String(rawHmac);

    } catch (Exception e) {
        throw new SignatureException("Failed to generate HMAC : " + e.getMessage());
    }
    return result;
    }

So I am trying to calculate this hmac with sha256 for AWS, but I do not get the excpected result, even though this example is taken from official AWS docs: http://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/AuthJavaSampleHMACSignature.html And the only thing changed is the algorithm, which did not break the program, so it should work, but it does not.

The result I get: k1T/qvVoXgEvmdFhTEh71vLDznqEVCyKcslA5RRSB6s= The result I expect: M/y0+EAFFGaUAp4bWv/WEuXYah99pVsxvqtAuC8YN7I=

Does anyone have any idea what is wrong?

Answer 1

It may have to do with how the newline character is interpreted. \\n can be a cr, lf, or cr-lf depending on your OS.

Answer 2

AWS uses to two different HMAC functions, the first returns the string representation, the other returns the binary representation. This is from my C++ implementation using OpenSSL, hope it helps:

string hmacHex(string key, string msg)
{
    unsigned char hash[32];

    HMAC_CTX hmac;
    HMAC_CTX_init(&hmac);
    HMAC_Init_ex(&hmac, &key[0], key.length(), EVP_sha256(), NULL);
    HMAC_Update(&hmac, (unsigned char*)&msg[0], msg.length());
    unsigned int len = 32;
    HMAC_Final(&hmac, hash, &len);
    HMAC_CTX_cleanup(&hmac);

    std::stringstream ss;
    ss << std::hex << std::setfill('0');
    for (int i = 0; i < len; i++)
    {   
        ss << std::hex << std::setw(2)  << (unsigned int)hash[i];
    }

    return (ss.str());
}

the string implementation

string hmac(string key, string msg)
{
    unsigned char hash[32];

    HMAC_CTX hmac;
    HMAC_CTX_init(&hmac);
    HMAC_Init_ex(&hmac, &key[0], key.length(), EVP_sha256(), NULL);
    HMAC_Update(&hmac, ( unsigned char* )&msg[0], msg.length());
    unsigned int len = 32;
    HMAC_Final(&hmac, hash, &len);
    HMAC_CTX_cleanup(&hmac);

    std::stringstream ss;
    ss << std::setfill('0');
    for (int i = 0; i < len; i++)
    {
        ss  << hash[i];
    }

    return (ss.str());
}

If you are using Java, I'd recommend using the corresponding SDK. I my experience the API's tend to change rather quickly.