在iOS / Swift中创建并导出为Java无法识别的base64的RSA公钥

TL; DR：无法识别在iOS中生成并存储在钥匙串中,作为base64导出并发送到Java后端的RSA公钥.

我正在iOS应用程序中实现聊天加密功能,并且使用对称非对称密钥来处理它.

无需赘述,在后端,我使用用户的公共密钥来加密用于加密和解密消息的对称密钥.

我分别在Swift和Java(后端)中创建了两个框架来处理密钥生成,加密,解密等.我也对它们进行了测试,因此我100％都能按预期工作.

但是,后端似乎无法识别从iOS传递的公钥格式.双方都使用RSA,这是我在Swift中用于生成密钥的代码：

// private key parameters
static let privateKeyParams: [String : Any] = [
        kSecAttrIsPermanent as String: true,
        kSecAttrApplicationTag as String: "..." // I have a proper unique tag here
]

// public  key parameters
static let publicKeyParams: [String : Any] = [
        kSecAttrIsPermanent as String: true,
        kSecAttrApplicationTag as String: "..." // I have a proper unique tag here
]

// global parameters for our key generation
static let keyCreationParameters: [String : Any] = [
        kSecAttrKeyType as String: kSecAttrKeyTypeRSA,
        kSecAttrKeySizeInBits as String: 2048,
        kSecPublicKeyAttrs as String: publicKeyParams,
        kSecPrivateKeyAttrs as String: privateKeyParams
]

...

var publicKey, privateKey: SecKey?
let status = SecKeyGeneratePair(Constants.keyCreationParameters as CFDictionary, &publicKey, &privateKey)

我使用镜面代码从钥匙串中读取钥匙.

这是我用来将公钥导出为base64字符串的代码：

extension SecKey {
  func asBase64() throws -> String {
    var dataPtr: CFTypeRef?
    let query: [String:Any] = [
      kSecClass as String: kSecClassKey,
      kSecAttrApplicationTag as String: "...", // Same unique tag here
      kSecAttrKeyType as String: kSecAttrKeyTypeRSA,
      kSecReturnData as String: kCFBooleanTrue
    ]
    let result = SecItemCopyMatching(query as CFDictionary, &dataPtr)

    switch (result, dataPtr) {
    case (errSecSuccess, .some(let data)):
      // convert to Base64 string
      let base64PublicKey = data.base64EncodedString(options: [])
      return base64PublicKey
    default:
      throw CryptoError.keyConversionError
    }
  }
}

在后端级别,我使用以下Java代码将base64字符串转换为公钥：

public PublicKey publicKeyFrom(String data) throws NoSuchAlgorithmException, InvalidKeySpecException {
    byte[] publicBytes = Base64.decodeBase64(data);
    X509EncodedKeySpec keySpec = new X509EncodedKeySpec(publicBytes);
    KeyFactory keyFactory = KeyFactory.getInstance("RSA");
    return keyFactory.generatePublic(keySpec);
}

但这在最后一行失败,但有以下例外：

java.security.spec.InvalidKeySpecException: java.security.InvalidKeyException: IOException: algid parse error, not a sequence

在进行一些手动调试时,我注意到公钥的格式是不同的-当我在iOS中生成密钥然后导出为base 64时,它看起来像这样：

MIIBCgKCAQEA4M/bRDdH0f6qFIXxOg13RHka+g4Yv8u9PpPp1IR6pSwrM1aq8B6cyKRwnLe/MOkvODvDfJzvGXGQ01zSTxYWAW1B4uc/NCEemCmZqMosSB/VUJdNxxWtt2hJxpz06hAawqV+6HmweAB2dUn9tDEsQLsNHdwYouOKpyRZGimcF9qRFn1RjR0Q54sUh1tQAj/EwmgY2S2bI5TqtZnZw7X7Waji7wWi6Gz88IkuzLAzB9VBNDeV1cfJFiWsZ/MIixSvhpW3dMNCrJShvBouIG8nS+vykBlbFVRGy3gJr8+OcmIq5vuHVhqrWwHNOs+WR87K/qTFO/CB7MiyiIV1b1x5DQIDAQAB

总共有360个字符,而在Java中(仍然使用RSA)做同样的事情,就像：

MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCAAnWO4BXUGP0qM3Op36YXkWNxb4I2pPZuZ7jJtfUO7v+IO1mq43WzNaxLqqLPkTnMrv2ACRDK55vin+leQlL1z0LzVxjtZ9F6pajQo1r7PqBlL5N8bzBFKpagEf0QfyHPw0/0kG9DMnvQ+Im881QyN2zdl33wp5Fi+jRT7cunFQIDAQAB

长度为216个字符.

我无法弄清楚出了什么问题-如果iOS处理其他密钥中的密钥,并且需要进行特殊处理才能与其他人交谈,那么我显然不会感到惊讶.

任何想法？

解决方法:

Java需要以DER格式编码的公共密钥.不幸的是,iOS不支持此标准格式,因此需要进行额外的转换(我不知道在最新版本的swift中是否会有所改善)

查看我的答案here您可以使用CryptoExportImportManager转换密钥

func exportPublicKeyToDER(keyId:String) -> NSData?{

    let publicKey = loadKeyStringFromKeyChainAsNSData(PUBLIC_KEY + keyId)
    let keyType = kSecAttrKeyTypeRSA
    let keySize = 2048
    let exportImportManager = CryptoExportImportManager()
    if let exportableDERKey = exportImportManager.exportPublicKeyToDER(publicKey, keyType: keyType as String, keySize: keySize) {
        return exportableDERKey
    } else {
        return nil
    }
}

标签：swift,rsa,public-key,ios,java
来源： https://codeday.me/bug/20191108/2007288.html