How should Secure Transport TLS be used with BSD s

问题:

I'm trying to use Secure Transport with BSD sockets using Swift. It seems like it should be simple enough, but I can't get it to work and documentation on the subject is scarce.

I've boiled my issue down to a simple "Socket" class, where I've (to the best of my knowledge) fulfilled the requirements of Secure Transport.

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
    }
}

I've tested the non-TLS socket communication by making a simple instance:

let socket = Socket(address: "some-ip-address", port: 8080)
socket.connect().sendHello()

and running an echo server on the target machine using netcat. This works fine.

nc -l -p 8080

Trying to wrap the socket in Secure Transport's TLS (calling the makeSecure() method) crashes at the call to SSLHandshake(...) with a EXC_BAD_ADDRESS(code=2, address=...) error. Does anyone have any pointers as to what it is I'm missing here?

EDIT

I can see Console puts out:

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

EDIT 2

I got it working with Swift 2 in the Xcode 7 beta. See below.

回答1:

Starting with Swift 2 included with the Xcode 7 beta, Function Pointers in Swift work and have been greatly simplified. I turned my example above into this, which works:

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)
}

回答2:

The answer by Hans appears to allocate memory unnecessarily. The following is a Swift 3.1 version with more error checking and URL support and grabs the common name to return (rather than actually reading or writing data).

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)
}

回答3:

I asked a network guru peer your question; this was his response:

This person is SOL because Secure Transport requires that you implement C function callbacks and Swift does not currently support that .

I recommend that developer use CFSocketStream, which takes care of TLS and is easily callable from Swift. See the TLSTool sample code.

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