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March 19, 2023 06:48
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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.
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| <!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> |
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| 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); | |
| }); |
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| 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"); |
Notice that Hmac.update(query) should get a Buffer and not a string.
It's case problems on unicode strings..
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.
@tymat How can I achieve that? I wast searching like a crazy the best way to implement a secure HMAC protection for node.
Thank you.
you saved my day
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
@mfn I think this should fixes the timing attack.
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");
}
Awesome ! thanks !
@mfn I think this should fixes the timing attack.
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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or maybe we're assuming that the client only arrives at the page (or receives code-on-demand) after initial login...