在JavaScript中使用SubtleCrypto进行HMAC验证的错误结果

Question

我正在尝试使用SubtleCrypto API验证HMAC签名。整个东西应该在Cloudflare Workers中运行，我正在使用他们的wrangler工具在本地测试它。

这是目前为止我的代码，但是它生成了错误的签名。

const message = "(query params from an url)";
const given_signature = "(extracted from the query params)";
const SECRET = "...";
const algorithm = { name: 'HMAC', hash: 'SHA-256' };
const encoder = new TextEncoder();
const key = await crypto.subtle.importKey(
'raw',
encoder.encode(SECRET),
algorithm,
false,
['sign', 'verify']
);
const signature = await crypto.subtle.sign(
algorithm.name,
key,
encoder.encode(message)
);
const digest = btoa(String.fromCharCode(...new Uint8Array(signature)));
// The digest does not match the signature extracted from the query params
// If I, for example, want to verify the signature directly, the result is still false.
const verify = await crypto.subtle.verify(
algorithm.name,
key,
encoder.encode(given_signature),
encoder.encode(message)
);

如果我在在线HMAC测试工具中使用相同的秘密和消息，我得到了正确的结果，所以我确信我的代码中一定有错误。

我发现有趣的是，我的代码生成的签名比给定的签名短得多(例如3fn0mhrebHTJMhtOyvRP5nZIhogX/M1OKQ5GojniZTM=vsddf9f49a1ade6c74c9321b4ecaf44fe67648868817fccd4e290e46a239e26533)。

有人知道我在哪里出错了吗?

Answer 1

感谢这些有用的评论!简而言之，问题在于提供的签名被编码为HEX字符串，而生成的签名是base64编码的字符串。

为了保持简洁，这里有一个使用crypto.subtle.verify函数的工作版本:

const message = "(query params from an url w/o the hmac signature)";
const given_signature = "(the given hmac signature extracted from the query params)";
const SECRET = "(my secret key)";
const hexToBuffer = (hex: string) => {
const matches = hex.match(/[da-f]{2}/gi) ?? [];
const typedArray = new Uint8Array(
matches.map(function (h) {
return parseInt(h, 16);
})
);
return typedArray.buffer;
};
const algorithm = { name: "HMAC", hash: "SHA-256" };
const encoder = new TextEncoder();
const key = await crypto.subtle.importKey(
"raw",
encoder.encode(SECRET),
algorithm,
false,
["sign", "verify"]
);
const result: boolean = await crypto.subtle.verify(
algorithm.name,
key,
hexToBuffer(given_signature),
encoder.encode(message)
);