NETransparentProxyProvider and AirDrop. Catch everything except AirDrop.

Question

DanilKorotenko OP

Created Jul ’22

Replies 4

Boosts 0

Views 1.2k

Participants 3

Hello.

How does excludedNetworkRules work? Can I setup such rules that allow me to catch everything except specified ports (AirDrop for example)?

I found that if my extension start with these rules:

[Extension ....]: provider set tunnel configuration to 
    tunnelRemoteAddress = <9-char-str>
    includedNetworkRules = (
        {
            matchRemoteEndpoint = 0.0.0.0:80
            matchRemotePrefix = 0
            matchProtocol = <3-char-str>
            matchDirection = <8-char-str>
            appliesToLoopback = NO
        },
        {
            matchRemoteEndpoint = 0.0.0.0:81
            matchRemotePrefix = 0
            matchProtocol = <3-char-str>
            matchDirection = <8-char-str>
            appliesToLoopback = NO
        },
        {
            matchRemoteEndpoint = 0.0.0.0:8080
            matchRemotePrefix = 0
            matchProtocol = <3-char-str>
            matchDirection = <8-char-str>
            appliesToLoopback = NO
        },
        {
            matchRemoteEndpoint = 0.0.0.0:443
            matchRemotePrefix = 0
            matchProtocol = <3-char-str>
            matchDirection = <8-char-str>
            appliesToLoopback = NO
        },
        {
            matchRemoteEndpoint = 0.0.0.0:25
            matchRemotePrefix = 0
            matchProtocol = <3-char-str>
            matchDirection = <8-char-str>
            appliesToLoopback = NO
        },
        {
            matchRemoteEndpoint = 0.0.0.0:587
            matchRemotePrefix = 0
            matchProtocol = <3-char-str>
            matchDirection = <8-char-str>
            appliesToLoopback = NO
        },
        {
            matchRemoteEndpoint = 0.0.0.0:465
            matchRemotePrefix = 0
            matchProtocol = <3-char-str>
            matchDirection = <8-char-str>
            appliesToLoopback = NO
        },
        {
            matchRemotePrefix = 0
            matchProtocol = <3-char-str>
            matchDirection = <8-char-str>
            appliesToLoopback = NO
        },
    )
    excludedNetworkRules = (
        {
            matchRemoteEndpoint = 0.0.0.0:8770
            matchRemotePrefix = 0
            matchProtocol = <3-char-str>
            matchDirection = <8-char-str>
            appliesToLoopback = NO
        },
        {
            matchRemoteEndpoint = 0.0.0.0:8770
            matchRemotePrefix = 0
            matchProtocol = <3-char-str>
            matchDirection = <8-char-str>
            appliesToLoopback = NO
        },
    )
    isFullyTransparent = YES

Note that rules contains wildcard rule:

        {
            matchRemotePrefix = 0
            matchProtocol = <3-char-str>
            matchDirection = <8-char-str>
            appliesToLoopback = NO
        },

Airdrop is not working.

I see in logs that connection is delivered to my extension, and it rejects it.:

(1899100530): New flow: NEFlow type = stream, app = com.apple.sharingd, name = 69e95d47-5e35-45d9-a0cf-252f226ec444.local, fe80:d::6c5b:6bff:fecc:e0a.0 <-> fe80::fc46:29ff:feaa:24ab.8770, filter_id = , interface = awdl0

(1899100530): Delivering to client

[Extension ....]: Calling handleNewFlow with TCP com.apple.sharingd[{length = 20, bytes = 0x890032e8aa2f6d927360921d19502b76ecd24700}] remote: fe80::fc46:29ff:feaa:24ab%awdl0.8770 interface awdl0

[Extension .....]: provider rejected new flow TCP com.apple.sharingd[{length = 20, bytes = 0x890032e8aa2f6d927360921d19502b76ecd24700}] remote: fe80::fc46:29ff:feaa:24ab%awdl0.8770 interface awdl0

(1899100530): Dropping the director

(1899100530): Destroying, client tx 0, client rx 0, kernel rx 0, kernel tx 0

If I specify exact ports to catch, Airdrop is working.

Could you help me, please?

Answered by DTS Engineer in 748656022

This recently came up in another thread so I figured I should post an update…

As I mentioned above, DanilKorotenko and I investigated this issue in another context. The conclusion was that this looks like a bug (r. 98382363). You can create a trivial transparent proxy, one that returns false to all handle-new-flow requests, and that still breaks AirDrop. Sadly, I was unable to find any sort of workaround.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Boost

Answer 1

Systems Engineer OP

Apple

Jul ’22

How does excludedNetworkRules work?

Can you post a code example of how your includedNetworkRules and excludedNetworkRules are setup on your NETransparentProxyNetworkSettings? I believe I get the gist of them but I want to make sure I understand your wildcard rule.

0

Answer 2

DTS Engineer OP

Apple

Jul ’22

I’ll be helping DanilKorotenko via a different channel.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

0

Answer 3

DanilKorotenko OP

Aug ’22

Can you post a code example of how your includedNetworkRules and excludedNetworkRules are setup on your NETransparentProxyNetworkSettings? I believe I get the gist of them but I want to make sure I understand your wildcard rule.

The reason why I raise this question is that AirDrop is not working if my extension is up.

I thought that I should exclude AirDrop port 8770 from connections. That is why I asked about exclude rules.

Code example. Here is how my extension start:

- (void)startProxyWithOptions:(NSDictionary *)options
  completionHandler:(void (^)(NSError *))completionHandler
{
  NETransparentProxyNetworkSettings *settings =
      [[NETransparentProxyNetworkSettings alloc]
        initWithTunnelRemoteAddress:@"127.0.0.1"];

  NENetworkRule *rule = [[NENetworkRule alloc]
    initWithRemoteNetwork:nil
    remotePrefix:0
    localNetwork:nil
    localPrefix:0
    protocol:NENetworkRuleProtocolTCP
    direction:NETrafficDirectionOutbound];

  settings.includedNetworkRules =
    @[
      rule
    ];

  [self setTunnelNetworkSettings:settings
    completionHandler:^(NSError * _Nullable error)
    {
      if (error)
      {
        NSLog(@"setTunnelNetworkSettings: %@", error.localizedDescription);
      }
    }];

  if (completionHandler != nil)
  {
    completionHandler(nil);
  }
}

And I always return NO in handleNewFlow:

- (BOOL)handleNewFlow:(NEAppProxyFlow *)flow
{
  return NO;
}

And AirDrop is not working.

0

Answer 4

DTS Engineer OP

Apple

Mar ’23

Accepted Answer

This recently came up in another thread so I figured I should post an update…

As I mentioned above, DanilKorotenko and I investigated this issue in another context. The conclusion was that this looks like a bug (r. 98382363). You can create a trivial transparent proxy, one that returns false to all handle-new-flow requests, and that still breaks AirDrop. Sadly, I was unable to find any sort of workaround.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

0