JWT 使用 HMACSHA256 验证签名并通过 Swift 显示 "Invalid Signature"

Question

我有一个关于 JWT 的问题。
我尝试创建自己的签名并使用硬编码密钥 "hello1234567890987654321test1234"。
然后我使用我的函数创建签名并使用 post 到 https://jwt.io/ 进行解码。
然后这个网页告诉我 "Invalid Signature".
我的 HMACSHA256 函数有什么问题？
我在网页上找到了“-”，“_”，并在我的输出签名中转换了“+”，“/”。
如何修复我的输出签名？
这个签名正确吗？

我也在 Google 中搜索了两个 HMACSHA256 方法。我不知道哪个更好。
请给我一些选择的建议。
谢谢。

图片：

方法一：

enum CryptoAlgorithm {
    case MD5, SHA1, SHA224, SHA256, SHA384, SHA512
    var HMACAlgorithm: CCHmacAlgorithm {
        var result: Int = 0
        switch self {
        case .MD5:      result = kCCHmacAlgMD5
        case .SHA1:     result = kCCHmacAlgSHA1
        case .SHA224:   result = kCCHmacAlgSHA224
        case .SHA256:   result = kCCHmacAlgSHA256
        case .SHA384:   result = kCCHmacAlgSHA384
        case .SHA512:   result = kCCHmacAlgSHA512
        }
        return CCHmacAlgorithm(result)
    }
    var digestLength: Int {
        var result: Int32 = 0
        switch self {
        case .MD5:      result = CC_MD5_DIGEST_LENGTH
        case .SHA1:     result = CC_SHA1_DIGEST_LENGTH
        case .SHA224:   result = CC_SHA224_DIGEST_LENGTH
        case .SHA256:   result = CC_SHA256_DIGEST_LENGTH
        case .SHA384:   result = CC_SHA384_DIGEST_LENGTH
        case .SHA512:   result = CC_SHA512_DIGEST_LENGTH
        }
        return Int(result)
    }
}

extension String {
    func hmac1(algorithm: CryptoAlgorithm, key: String) -> String {
        var result: [CUnsignedChar]
        if let ckey = key.cString(using: String.Encoding.utf8), let cdata = self.cString(using: String.Encoding.utf8) {
            result = Array(repeating: 0, count: Int(algorithm.digestLength))
            CCHmac(algorithm.HMACAlgorithm, ckey, ckey.count-1, cdata, cdata.count-1, &result)
        } else {
            fatalError("Nil returned when processing input strings as UTF8")
        }

        return Data(bytes: result, count: result.count).base64EncodedString()
    }
}

方法二：

enum HMACAlgorithm {
    case MD5, SHA1, SHA224, SHA256, SHA384, SHA512

    func toCCHmacAlgorithm() -> CCHmacAlgorithm {
        var result: Int = 0
        switch self {
        case .MD5:
            result = kCCHmacAlgMD5
        case .SHA1:
            result = kCCHmacAlgSHA1
        case .SHA224:
            result = kCCHmacAlgSHA224
        case .SHA256:
            result = kCCHmacAlgSHA256
        case .SHA384:
            result = kCCHmacAlgSHA384
        case .SHA512:
            result = kCCHmacAlgSHA512
        }
        return CCHmacAlgorithm(result)
    }

    func digestLength() -> Int {
        var result: CInt = 0
        switch self {
        case .MD5:
            result = CC_MD5_DIGEST_LENGTH
        case .SHA1:
            result = CC_SHA1_DIGEST_LENGTH
        case .SHA224:
            result = CC_SHA224_DIGEST_LENGTH
        case .SHA256:
            result = CC_SHA256_DIGEST_LENGTH
        case .SHA384:
            result = CC_SHA384_DIGEST_LENGTH
        case .SHA512:
            result = CC_SHA512_DIGEST_LENGTH
        }
        return Int(result)
    }
}

extension String {
    func hmac2(algorithm: HMACAlgorithm, key: String) -> String {
        let cKey = key.cString(using: String.Encoding.utf8)
        let cData = self.cString(using: String.Encoding.utf8)
        var result = [CUnsignedChar](repeating: 0, count: Int(algorithm.digestLength()))
        CCHmac(algorithm.toCCHmacAlgorithm(), cKey!, strlen(cKey!), cData!, strlen(cData!), &result)
        let hmacData:NSData = NSData(bytes: result, length: (Int(algorithm.digestLength())))
        let hmacBase64 = hmacData.base64EncodedString(options: .lineLength76Characters)
        return String(hmacBase64)
    }
}

用法：

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let headerString: String = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9"
        let payloadString: String = "eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ"
        let totalString: String = headerString + "." + payloadString

        let signature1 = totalString.hmac1(algorithm: .SHA256, key: "hello1234567890987654321test1234")
        let signature2 = totalString.hmac2(algorithm: .SHA256, key: "hello1234567890987654321test1234")

        print("signature1 : \(signature1)") // signature1 : L9YSDasvO2B5i8FZUczC+MAtSsTuM0Dj+FEpfn6uoRs=
        print("signature2 : \(signature2)") // signature2 : L9YSDasvO2B5i8FZUczC+MAtSsTuM0Dj+FEpfn6uoRs=

    }
}

Answer 1

问题出在编码上。 JWT uses base64url encoding :

A JWT is represented as a sequence of URL-safe parts separated by period ('.') characters. Each part contains a base64url-encoded value.

但是您在签名中使用了 base64 编码，如您的代码示例所示。

base64url encoding和base64编码的区别在于，普通base64输出的字符'+'和'/'将被替换为'-'和'_'以及结尾的'=' (padding) 将被省略。

你说：

And I found the "-","_" in webside and convert "+","/" in my output signature.

使用“-”和“_”而不是“+”和“/”，您的输出是正确的。

当你有像这样的 base64url 编码签名时

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.L9YSDasvO2B5i8FZUczC-MAtSsTuM0Dj-FEpfn6uoRs

签名将被验证。

JWT 使用 HMACSHA256 验证签名并通过 Swift 显示 "Invalid Signature"

JWT verify signature using HMACSHA256 and show "Invalid Signature" by Swift

ios

swift

jwt

sha256

hmac