Webcrypto PBKDF2-SHA1

Question

我在将 PBKDF2 与 Webcrypto 结合使用时遇到问题。我想将 PBKDF2 与 SHA-1 算法一起使用。目前，我有，

const ENCODING = "utf-8";
const HMACSHA1 = {name: "HMAC", "hash" : "SHA-1"};
const PBKDF2SHA1 = {name: "PBKDF2", "hash": "SHA-1"};

// str2binb takes a string and outputs an ArrayBuffer

async function pbkdf2_generate_key_from_string(string) { //  Working
  return crypto.subtle.importKey(
    "raw",
    str2binb(string),
    PBKDF2SHA1,
    false,
    ["deriveKey", "deriveBits"],
  );
}

async function pbkdf2_derive_salted_key(key, salt, iterations) {  // Not working
  return crypto.subtle.deriveKey(
    {
      "name": "PBKDF2",
      "salt": salt,
      "iterations": iterations,
      "hash": "SHA-1",
      "length": 160
    },
    key,
    {
      "name": "HMAC"
      "hash": "SHA-1",
      "length": 160
    },
    true,
    [ "encrypt", "decrypt"]
  );
}

但是我知道我一定是用错了，因为它是一种受支持的密钥派生算法，并且根据 Mozilla 的精彩文档，在 derivedKeyAlgorithm 下支持 HMAC 以及 HMAC-SHA1。我也很直接地使用它 AES-GCM。

我尝试时收到的错误消息，

salt = b64binb("QSXCR+Q6sek8bf92"); // ArrayBuffer
key = await pbkdf2_generate_key_from_string("pencil");
x = await pbkdf2_derive_salted_key(key, salt, 4096)

是Uncaught DOMException: Cannot create a key using the specified key usages.

注意：我知道不再推荐使用 SHA1，这是为了支持旧版。

注意 2：当我将上面的替换为

时它有效

async function pbkdf2_derive_salted_key(key, data, salt, iterations) {  // Not working
  return crypto.subtle.deriveKey(
    {
      "name": "PBKDF2",
      salt: salt,
      "iterations": iterations,
      "hash": "SHA-1",
    },
    key,
    {
      "name": "AES-GCM",
      "length": 256
    },
    true,
    [ "encrypt", "decrypt"]
  );
}

谢谢。

Answer 1

在deriveKey中，参数keyUsages必须改为["sign", "verify"]。然后代码有效（因为 b64binb、str2binb 未发布，以下代码使用适当的替代品）：

const b64binb = base64String => Uint8Array.from(atob(base64String), c => c.charCodeAt(0));
const str2binb = str => new TextEncoder().encode(str);
const buf2hex = buffer => Array.prototype.map.call(new Uint8Array(buffer), x => ('00' + x.toString(16)).slice(-2)).join('');

async function pbkdf2_generate_key_from_string(string) { 
    return crypto.subtle.importKey(
        "raw",
        str2binb(string),
        {
            name: "PBKDF2",
        },
        false,
        ["deriveKey", "deriveBits"], 
    );
}

async function pbkdf2_derive_salted_key(key, salt, iterations) {  
    return crypto.subtle.deriveKey(
        {
            name: "PBKDF2",
            salt: salt,
            iterations: iterations,
            hash: {name: "SHA-1"}
        },
        key,
        {
            name: "HMAC",
            hash: "SHA-1",
            length: 160
        },
        true,
        ["sign", "verify"] // <--------------------- Fix!
    );
}

async function test(){
    salt = b64binb("QSXCR+Q6sek8bf92"); // ArrayBuffer
    key = await pbkdf2_generate_key_from_string("pencil");
    x = await pbkdf2_derive_salted_key(key, salt, 4096)

    console.log(buf2hex(await window.crypto.subtle.exportKey("raw", x)));
}

test();

使用此密钥，window.crypto.subtle.sign 使用 HMAC-SHA1 创建签名。

更新：

由于在 SubtleCrypto 中通常指定了密钥的使用，因此必须将 ["encrypt", "decrypt"] 应用为 AES-GCM 的 keyUsages 参数和 HMAC-SHA 的 ["sign", "verify"] .

为什么 ["encrypt", "decrypt"] 用于 AES-GCM？ AES-GCM 用于加密/解密 消息：AES describes a block cipher (allowing the encryption of a single block) and GCM the mode of operation（允许加密更多比一个块）。 GCM 提供机密性、真实性和完整性。

为什么 ["sign", "verify"] 用于 HMAC-SHA？ HMAC 用于 签名/验证 消息：某些操作模式，例如 CBC only provide confidentiality. To additionally supply authenticity and integrity, the message can be signed with a MAC (e.g. an HMAC which is a specific type of MAC based on a cryptographic hash function e.g. one of the SHA family). The MAC is typically calculated from the ciphertext and not the plaintext (Encrypt-then-MAC). With regard to the SHA1 vulnerabilities, see for a comparison of HMAC-SHA1 and HMAC-SHA256 here and here.

Webcrypto PBKDF2-SHA1

Webcrypto PBKDF2-SHA1

javascript

cryptography

pbkdf2

hmacsha1

webcrypto