Go Hmac SHA1 generates hash different from Hmac SHA1 in Java

Question

I'm just starting to learn Go and I'm trying to rewrite my existing small application from Java to Go.

I need to create Base64 hash of input string with key using Hmac SHA1 algorithm.

My Java code:

private String getSignedBody(String input, String key) {
    String result = "";
    try {
        SecretKeySpec signingKey = new SecretKeySpec(key.getBytes("UTF-8"), "HmacSHA1");
        Mac mac = Mac.getInstance("HmacSHA1");
        mac.init(signingKey);
        byte[] rawHmac = mac.doFinal(input.getBytes("UTF-8"));
        result = Base64.encodeToString(rawHmac, false);
    } catch (Exception e) {
        Logger.error("Failed to generate signature: " + e.getMessage());
    }
    return result;
}

My Go code:

func GetSignature(input, key string) string {
    key_for_sign := []byte(key)
    h := hmac.New(sha1.New, key_for_sign)
    h.Write([]byte(input))
    return base64.StdEncoding.EncodeToString(h.Sum(nil))
}

The problem is that Go code generates output that is not expected. For example, for input string "qwerty" and key "key" Java output will be RiD1vimxoaouU3VB1sVmchwhfhg= and Go output will be 9Cuw7rAY671Fl65yE3EexgdghD8=.

Where did I make mistakes in the Go code?

Answer 1

The Go code you provided gives exactly the same output as the Java code.

Try it on the Go Playground.

Output:

RiD1vimxoaouU3VB1sVmchwhfhg=

You made the mistake when you called your GetSignature() function. Call it like the linked example code:

fmt.Println(GetSignature("qwerty", "key"))

Your mistake was that you passed an empty input to your GetSignature() function. Calling it with empty "" input and "key" key produces the non-expected output you provided:

fmt.Println(GetSignature("", "key"))

Output:

9Cuw7rAY671Fl65yE3EexgdghD8=