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HMAC-SHA256 example for verifying both the data integrity and the authentication of a request in Node.js and web browsers.
Raw
client.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>HMAC-SHA256 Example</title>
</head>
<body>
<script src="http://crypto.stanford.edu/sjcl/sjcl.js"></script>
<script>
var sharedSecret, query, signature, hmac, xhr;
// No longer secret shared secret ;-)
sharedSecret = "super-secret";
query = "key=value";
hmac = new sjcl.misc.hmac(sjcl.codec.utf8String.toBits(sharedSecret), sjcl.hash.sha256);
signature = sjcl.codec.hex.fromBits(hmac.encrypt(query));
xhr = new XMLHttpRequest();
xhr.open("GET", "http://localhost:1337/?" + query);
xhr.setRequestHeader("X-Signature", signature);
xhr.onload = function () {
console.log(xhr.status, xhr.responseText);
}
xhr.send(null);
</script>
</body>
</html>
Raw
client.js
var http, crypto, sharedSecret, query, signature;
http = require("http");
crypto = require("crypto");
sharedSecret = "super-secret";
query = "key=value";
signature = crypto.createHmac("sha256", sharedSecret).update(query).digest("hex");
http.get({
port: 1337,
path: "/?" + query,
headers: {
"X-Signature": signature
}
}, function (res) {
console.log(res.statusCode);
});
Raw
server.js
var http, url, crypto, sharedSecret;
http = require("http");
url = require("url");
crypto = require("crypto");
sharedSecret = "super-secret";
http.createServer(function (req, res) {
var retrievedSignature, parsedUrl, computedSignature;
// Deal with CORS.
res.setHeader("Access-Control-Allow-Origin", "*");
if (req.method === "OPTIONS") {
res.setHeader("Access-Control-Allow-Headers", "X-Signature");
res.writeHead(204);
res.end();
} else {
// Get signature.
retrievedSignature = req.headers["x-signature"];
// Recalculate signature.
parsedUrl = url.parse(req.url);
computedSignature = crypto.createHmac("sha256", sharedSecret).update(parsedUrl.query).digest("hex");
// Compare signatures.
if (computedSignature === retrievedSignature) {
res.writeHead(200, {
"Content-Type": "text/plain"
});
res.end("Hello World\n");
} else {
res.writeHead(403, {
"Content-Type": "text/plain"
});
res.end("Get Out\n");
}
}
}).listen(1337);
console.log("Server running on port 1337");
@kabala
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kabala commented Jul 10, 2017

@tymat How can I achieve that? I wast searching like a crazy the best way to implement a secure HMAC protection for node.

@MohammedEssehemy
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Thank you.
you saved my day

@mfn
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mfn commented Apr 29, 2018

This is an insecure implementation that is vulnerable to replay attacks. Each request should include an incremental nonce that is kept track on the server side.

Not only that, it's also vulnerable to timing attacks due to the comparison with pure ===, see https://gist.github.com/agrueneberg/6585680#file-server-js-L24

@xeaone
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xeaone commented Aug 21, 2018 •
edited
Loading

@mfn I think this should fixes the timing attack.

Modified Fork

        const computedSignatureBuffer = Buffer.from(computedSignature, 'hex');
        const retrievedSignatureBuffer = Buffer.from(retrievedSignature, 'hex');
        const valid = crypto.timingSafeEqual(computedSignatureBuffer, retrievedSignatureBuffer);

        if (valid) {
            res.writeHead(200, {
                "content-type": "text/plain"
            });
            res.end("hello world\n");
        } else {
            res.writeHead(403, {
                "content-type": "text/plain"
            });
            res.end("get out\n");
        }

@shide1989
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Awesome ! thanks !

@Blackening999
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@mfn I think this should fixes the timing attack.

Modified Fork

        const computedSignatureBuffer = Buffer.from(computedSignature, 'hex');
        const retrievedSignatureBuffer = Buffer.from(retrievedSignature, 'hex');
        const valid = crypto.timingSafeEqual(computedSignatureBuffer, retrievedSignatureBuffer);

        if (valid) {
            res.writeHead(200, {
                "content-type": "text/plain"
            });
            res.end("hello world\n");
        } else {
            res.writeHead(403, {
                "content-type": "text/plain"
            });
            res.end("get out\n");
        }

That helps!

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