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Swift中的BSD套接字如何使用安全传输TLS ?



我正在尝试使用Swift使用BSD套接字的安全传输。它看起来应该足够简单，但是我无法使它工作，而且关于这个主题的文档很少。

我把我的问题归结为一个简单的"Socket"类，在那里我(据我所知)满足了安全传输的要求。

import Cocoa
class Socket: NSObject {
    private let hello = "Hello!"
    private var socketfd: Int32
    private var sock_addr: sockaddr
    private var sslContext: SSLContext?
    var sslWriteCallbackFunc: SSLWriteFunc {
        get {
            let ump = UnsafeMutablePointer<((SSLConnectionRef, UnsafePointer<Void>,
                UnsafeMutablePointer<Int>) -> OSStatus)>.alloc(1)
            ump.initialize(sslWriteCallback)
            return CFunctionPointer<((SSLConnectionRef, UnsafePointer<Void>,
                UnsafeMutablePointer<Int>) -> OSStatus)>(COpaquePointer(ump))
        }
    }
    var sslReadCallbackFunc: SSLReadFunc {
        get {
            let ump = UnsafeMutablePointer<((SSLConnectionRef, UnsafeMutablePointer<Void>,
                UnsafeMutablePointer<Int>) -> OSStatus)>.alloc(1)
            ump.initialize(sslReadCallback)
            return CFunctionPointer<((SSLConnectionRef, UnsafeMutablePointer<Void>,
                UnsafeMutablePointer<Int>) -> OSStatus)>(COpaquePointer(ump))
        }
    }
    init(address: String, port: UInt16) {
        socketfd = Darwin.socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)
        var addr = Darwin.sockaddr_in(sin_len: __uint8_t(sizeof(sockaddr_in)), sin_family: sa_family_t(AF_INET), sin_port: CFSwapInt16(port), sin_addr: in_addr(s_addr: inet_addr(address)), sin_zero: (0, 0, 0, 0, 0, 0, 0, 0))
        sock_addr = Darwin.sockaddr(sa_len: 0, sa_family: 0, sa_data: (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
        Darwin.memcpy(&sock_addr, &addr, Int(sizeof(sockaddr_in)))
        super.init()
    }
    func connect() -> Socket {
        let err = Darwin.connect(socketfd, &sock_addr, socklen_t(sizeof(sockaddr_in)))
        return self
    }
    func makeSecure() -> Socket {
        if let umc = SSLCreateContext(nil, kSSLClientSide, kSSLStreamType) {
            sslContext = umc.takeRetainedValue()
            var status = SSLSetIOFuncs(sslContext!, sslReadCallbackFunc, sslWriteCallbackFunc)
            status = SSLSetConnection(sslContext!, &socketfd)
            SSLHandshake(sslContext!)
        }
        return self
    }
    func sendHello() -> Socket {
        let bytes = [UInt8](hello.utf8)
        let data = NSData(bytes: bytes, length: bytes.count)
        let test = UnsafeMutablePointer<Int>.alloc(1)
        test.initialize(bytes.count)
        self.sslWriteCallback(&socketfd, data: data.bytes, dataLength: test)
        return self
    }
    // MARK: - SSL Callback Methods
    func sslReadCallback(connection: SSLConnectionRef,
        data: UnsafeMutablePointer<Void>,
        dataLength: UnsafeMutablePointer<Int>) -> OSStatus {
            let bytesRead = read(socketfd, data, UnsafePointer<Int>(dataLength).memory)
            return noErr
    }
    func sslWriteCallback(connection: SSLConnectionRef,
        data: UnsafePointer<Void>,
        dataLength: UnsafeMutablePointer<Int>) -> OSStatus {
            let sent = Darwin.sendto(socketfd, data, UnsafePointer<Int>(dataLength).memory, 0, &sock_addr, socklen_t(sizeof(sockaddr_in)))
            if (sent < 0) {
                let error = NSError(domain: NSPOSIXErrorDomain, code: Int(errno), userInfo: nil)
                println(error.localizedDescription)
            } else {
                println("Sent (sent) bytes ((hello))")
            }
            return noErr
    }
}
我通过创建一个简单的实例测试了非tls套接字通信: 
let socket = Socket(address: "some-ip-address", port: 8080)
socket.connect().sendHello()

，并使用netcat在目标机器上运行echo服务器。

nc -l -p 8080

尝试在安全传输的TLS中包装套接字(调用makeSecure()方法)在调用SSLHandshake(…)时崩溃，并出现EXC_BAD_ADDRESS(code=2, address=…)错误。有谁能告诉我我遗漏了什么吗?

编辑

我可以看到控制台输出:

04/06/15 09:20:48,000 kernel[0]: Data/Stack execution not permitted: TheProject[pid 29184] at virtual address 0x100602000, protections were read-write

编辑2

我在Xcode 7测试版中使用了Swift 2。看到下面。

从Xcode 7 beta中包含的Swift 2开始，函数指针在Swift中的工作和已经大大简化了。我把上面的例子变成了这样:

import Foundation
func sslReadCallback(connection: SSLConnectionRef,
    data: UnsafeMutablePointer<Void>,
    var dataLength: UnsafeMutablePointer<Int>) -> OSStatus {
        let socketfd = UnsafePointer<Int32>(connection).memory
        let bytesRequested = dataLength.memory
        let bytesRead = read(socketfd, data, UnsafePointer<Int>(dataLength).memory)
        if (bytesRead > 0) {
            dataLength = UnsafeMutablePointer<Int>.alloc(1)
            dataLength.initialize(bytesRead)
            if bytesRequested > bytesRead {
                return Int32(errSSLWouldBlock)
            } else {
                return noErr
            }
        } else if (bytesRead == 0) {
            dataLength = UnsafeMutablePointer<Int>.alloc(1)
            dataLength.initialize(0)
            return Int32(errSSLClosedGraceful)
        } else {
            dataLength = UnsafeMutablePointer<Int>.alloc(1)
            dataLength.initialize(0)
            switch (errno) {
            case ENOENT: return Int32(errSSLClosedGraceful)
            case EAGAIN: return Int32(errSSLWouldBlock)
            case ECONNRESET: return Int32(errSSLClosedAbort)
            default: return Int32(errSecIO)
            }
        }
}
func sslWriteCallback(connection: SSLConnectionRef,
    data: UnsafePointer<Void>,
    var dataLength: UnsafeMutablePointer<Int>) -> OSStatus {
        let socketfd = UnsafePointer<Int32>(connection).memory
        let bytesToWrite = dataLength.memory
        let bytesWritten = write(socketfd, data, UnsafePointer<Int>(dataLength).memory)
        if (bytesWritten > 0) {
            dataLength = UnsafeMutablePointer<Int>.alloc(1)
            dataLength.initialize(bytesWritten)
            if (bytesToWrite > bytesWritten) {
                return Int32(errSSLWouldBlock)
            } else {
                return noErr
            }
        } else if (bytesWritten == 0) {
            dataLength = UnsafeMutablePointer<Int>.alloc(1)
            dataLength.initialize(0)
            return Int32(errSSLClosedGraceful)
        } else {
            dataLength = UnsafeMutablePointer<Int>.alloc(1)
            dataLength.initialize(0)
            if (EAGAIN == errno) {
                return Int32(errSSLWouldBlock)
            } else {
                return Int32(errSecIO)
            }
        }
}
var socketfd = Darwin.socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)
var addr = Darwin.sockaddr_in(sin_len: __uint8_t(sizeof(sockaddr_in)), sin_family: sa_family_t(AF_INET), sin_port: CFSwapInt16(8080), sin_addr: in_addr(s_addr: inet_addr("192.168.0.113")), sin_zero: (0, 0, 0, 0, 0, 0, 0, 0))
var sock_addr = Darwin.sockaddr(sa_len: 0, sa_family: 0, sa_data: (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
Darwin.memcpy(&sock_addr, &addr, Int(sizeof(sockaddr_in)))
var err = Darwin.connect(socketfd, &sock_addr, socklen_t(sizeof(sockaddr_in)))
if let umc = SSLCreateContext(kCFAllocatorDefault, kSSLClientSide, kSSLStreamType) {
    var sslContext = umc.takeRetainedValue()
    SSLSetIOFuncs(sslContext, sslReadCallback, sslWriteCallback)
    SSLSetConnection(sslContext, &socketfd)
    SSLSetSessionOption(sslContext, kSSLSessionOptionBreakOnClientAuth, Boolean(1))
    SSLHandshake(sslContext)
}

Hans的回答似乎不必要地分配了内存。下面是一个Swift 3.1版本，有更多的错误检查和URL支持，并抓取通用名称返回(而不是实际读取或写入数据)。

func getCNforSSL(at url:URL, port:UInt16) -> String? {
  var socketfd = Darwin.socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)
  guard let ip = urlToIP(url) else {
    NSLog("Could not get IP from URL (url)")
    return nil
  }
  let inAddr = in_addr(s_addr: inet_addr(ip))
  var addr = sockaddr_in(sin_len: __uint8_t(MemoryLayout<sockaddr_in>.size),
                         sin_family: sa_family_t(AF_INET),
                         sin_port: CFSwapInt16(port),
                         sin_addr: inAddr,
                         sin_zero: (0, 0, 0, 0, 0, 0, 0, 0))
  var sock_addr = sockaddr(sa_len: 0,
                           sa_family: 0,
                           sa_data: (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
  _ = memcpy(&sock_addr, &addr, MemoryLayout<sockaddr_in>.size)
  guard connect(socketfd, &sock_addr, socklen_t(MemoryLayout<sockaddr_in>.size)) == 0 else {
    NSLog("Failed connection for (url) port (port) with error (Darwin.errno)")
    return nil
  }
  defer {
    if close(socketfd) != 0 {
      NSLog("Error closing socket for (url) port (port) with error (Darwin.errno)")
    }
  }
  guard let sslContext = SSLCreateContext(kCFAllocatorDefault, .clientSide, .streamType) else {
    NSLog("Could not create SSL Context for (url) port (port)")
    return nil
  }
  defer {
    SSLClose(sslContext)
  }
  SSLSetIOFuncs(sslContext, sslReadCallback, sslWriteCallback)
  SSLSetConnection(sslContext, &socketfd)
  SSLSetSessionOption(sslContext, .breakOnServerAuth, true)
  var secTrust:SecTrust? = nil
  var status:OSStatus = 0
  var subject:String? = nil
  repeat {
    status = SSLHandshake(sslContext)
    if status == errSSLPeerAuthCompleted {
      SSLCopyPeerTrust(sslContext, &secTrust)
      if let trust = secTrust {
        // 0 always garunteed to exist
        let cert = SecTrustGetCertificateAtIndex(trust, 0)!
        subject = SecCertificateCopySubjectSummary(cert) as String?
      }
    }
  } while status == errSSLWouldBlock
  guard status == errSSLPeerAuthCompleted else {
    NSLog("SSL Handshake Error for (url) port (port) OSStatus (status)")
    return nil
  }
  return subject
}
func sslReadCallback(connection: SSLConnectionRef,
                            data: UnsafeMutableRawPointer,
                            dataLength: UnsafeMutablePointer<Int>) -> OSStatus {
  let socketfd = connection.load(as: Int32.self)
  let bytesRequested = dataLength.pointee
  let bytesRead = read(socketfd, data, UnsafePointer<Int>(dataLength).pointee)
  if (bytesRead > 0) {
    dataLength.initialize(to: bytesRead)
    if bytesRequested > bytesRead {
      return Int32(errSSLWouldBlock)
    } else {
      return noErr
    }
  } else if (bytesRead == 0) {
    dataLength.initialize(to: 0)
    return Int32(errSSLClosedGraceful)
  } else {
    dataLength.initialize(to: 0)
    switch (errno) {
    case ENOENT: return Int32(errSSLClosedGraceful)
    case EAGAIN: return Int32(errSSLWouldBlock)
    case ECONNRESET: return Int32(errSSLClosedAbort)
    default: return Int32(errSecIO)
    }
  }
}
func sslWriteCallback(connection: SSLConnectionRef,
                             data: UnsafeRawPointer,
                             dataLength: UnsafeMutablePointer<Int>) -> OSStatus {
  let socketfd = connection.load(as: Int32.self)
  let bytesToWrite = dataLength.pointee
  let bytesWritten = write(socketfd, data, UnsafePointer<Int>(dataLength).pointee)
  if (bytesWritten > 0) {
    dataLength.initialize(to: bytesWritten)
    if (bytesToWrite > bytesWritten) {
      return Int32(errSSLWouldBlock)
    } else {
      return noErr
    }
  } else if (bytesWritten == 0) {
    dataLength.initialize(to: 0)
    return Int32(errSSLClosedGraceful)
  } else {
    dataLength.initialize(to: 0)
    if (EAGAIN == errno) {
      return Int32(errSSLWouldBlock)
    } else {
      return Int32(errSecIO)
    }
  }
}
private func urlToIP(_ url:URL) -> String? {
  guard let hostname = url.host else {
    return nil
  }
  guard let host = hostname.withCString({gethostbyname($0)}) else {
    return nil
  }
  guard host.pointee.h_length > 0 else {
    return nil
  }
  var addr = in_addr()
  memcpy(&addr.s_addr, host.pointee.h_addr_list[0], Int(host.pointee.h_length))
  guard let remoteIPAsC = inet_ntoa(addr) else {
    return nil
  }
  return String.init(cString: remoteIPAsC)
}

我问了一个网络大师同行你的问题;这是他的回答:

这个人是SOL，因为安全传输要求你实现C函数回调，而Swift目前不支持。

我建议开发者使用CFSocketStream，它负责TLS，并且很容易从Swift调用。参见TLSTool示例代码。

https://developer.apple.com/library/mac/samplecode/SC1236/

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