使用Swift生成base64 url​​编码的X.509格式2048位RSA公钥？

Question

在Apple Swift for iOS中工作.我必须为后端生成这个,因为它是一个安全的应用程序.

我是安全和证书的新手,现在一直在寻找一天没有结果.

如何使用swift生成base64 url​​编码的X.509格式2048位RSA公钥？

任何帮助都非常感谢.

Answer 1

在我最近创建的一个名为Heimdall的 Swift中有一个用于处理公钥 - 私钥对的库,它允许您轻松导出公钥的X.509格式化Base64字符串.

为了遵守SO规则,我还将在此答案中包含实现(以便它不言自明)

public func X509PublicKey() -> NSString? {
    // Fetch the key, so that key = NSData of the public key
    let result = NSMutableData()

    let encodingLength: Int = {
        if key.length + 1 < 128 {
            return 1
        } else {
            return ((key.length + 1) / 256) + 2
        }
    }()

    let OID: [CUnsignedChar] = [0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86,
        0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05, 0x00]

    var builder: [CUnsignedChar] = []

    // ASN.1 SEQUENCE
    builder.append(0x30)

    // Overall size, made of OID + bitstring encoding + actual key
    let size = OID.count + 2 + encodingLength + key.length
    let encodedSize = encodeLength(size)
    builder.extend(encodedSize)
    result.appendBytes(builder, length: builder.count)
    result.appendBytes(OID, length: OID.count)
    builder.removeAll(keepCapacity: false)

    builder.append(0x03)
    builder.extend(encodeLength(key.length + 1))
    builder.append(0x00)
    result.appendBytes(builder, length: builder.count)

    // Actual key bytes
    result.appendData(key)

    // Convert to Base64 and make safe for URLs
    var string = result.base64EncodedStringWithOptions(.allZeros)
    string = string.stringByReplacingOccurrencesOfString("/", withString: "_")
    string = string.stringByReplacingOccurrencesOfString("+", withString: "-")

    return string
}

public func encodeLength(length: Int) -> [CUnsignedChar] {
    if length < 128 {
        return [CUnsignedChar(length)];
    }

    var i = (length / 256) + 1
    var len = length
    var result: [CUnsignedChar] = [CUnsignedChar(i + 0x80)]

    for (var j = 0; j < i; j++) {
        result.insert(CUnsignedChar(len & 0xFF), atIndex: 1)
        len = len >> 8
    }

    return result
}

我已经删除了数据提取代码,请参考Heimdall的来源或Jeff Hay的答案

Answer 2

如果公钥已在您的钥匙串中，则可以查找公钥，并以类似于以下内容的方式将数据作为base64返回：

// Create dictionary to specify attributes for the key we're
// searching for.  Swift will automatically bridge native values 
// to to right types for the SecItemCopyMatching() call.
var queryAttrs = [NSString:AnyObject]() 
queryAttrs[kSecClass] = kSecClassKey 
queryAttrs[kSecAttrApplicationTag] = publicKeyTag
queryAttrs[kSecAttrKeyType] = kSecAttrKeyTypeRSA
queryAttrs[kSecReturnData] = true

var publicKeyBits = Unmanaged<AnyObject>?()
SecItemCopyMatching(queryAttrs, &publicKeyBits)

// Work around a compiler bug with Unmanaged<AnyObject> types
//  the following two lines should simply be 
//  let publicKeyData : NSData = publicKeyRef!.takeRetainedValue() as NSData
let opaqueBits = publicKeyBits?.toOpaque() 
let publicKeyData = Unmanaged<NSData>.fromOpaque(opaqueBits).takeUnretainedValue()

let publicKeyBase64 = publicKeyData.base64EncodedData(NSDataBase64EncodingOptions.Encoding64CharacterLineLength)

如果您需要生成密钥对并将其存储在钥匙串中，请按照以下方式使用：

// Create dictionaries to specify key attributes.  Swift will
// automatically bridge native values to to right types for the
// SecKeyGeneratePair() call.
var pairAttrs = [NSString:AnyObject]()
var privateAttrs = [NSString:AnyObject]()
var publicAttrs = [NSString:AnyObject]()

privateAttrs[kSecAttrIsPermanent] = true
privateAttrs[kSecAttrApplicationTag] = privateKeyTag

publicAttrs[kSecAttrIsPermanent] = true
publicAttrs[kSecAttrApplicationTag] = publicKeyTag

pairAttrs[kSecAttrKeyType] = kSecAttrKeyTypeRSA
pairAttrs[kSecAttrKeySizeInBits] = 2048
pairAttrs[(kSecPrivateKeyAttrs.takeUnretainedValue() as! String)] = privateAttrs
pairAttrs[(kSecPublicKeyAttrs.takeUnretainedValue() as! String)] = publicAttrs

var publicKeyPtr = Unmanaged<SecKey>?()
var privateKeyPtr = Unmanaged<SecKey>?()

let status = SecKeyGeneratePair(pairAttrs, &publicKeyPtr, &privateKeyPtr)

注意： publicKeyTag和privateKeyTag是用于标识密钥库中密钥的字符串。Apple建议使用反向DNS表示法（com.company.key.xxx），但只要它们是唯一的，一切都应该很好。