Email Traffic Blocked by Automatic Proxy Settings in iOS and iPadOS 13

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Level 1

41 points

Email Traffic Blocked by Automatic Proxy Settings in iOS and iPadOS 13

After upgrading to iOS and iPadOS 13, all internet email accounts (Gmail, ISP, all port 993 IMAP accounts) are unable to sync when the Settings>Wi-Fi> HTTP PROXY > Automatic Proxy is set to any proxy.pac file that uses a proxy.

All other traffic works and is routed correctly through the proxy, and all email and web traffic on all iOS 12 devices works correctly.

Does anyone else see this and know of a workaround?

I have created a minimum working example of the bug. Here is a sample proxy.pac file that shows the problem:

function FindProxyForURL(url, host)

{

// return "DIRECT";

return "PROXY 10.0.1.3:3129";

}

I have confirmed the issue with my own deployed proxy, and a standalone "mitmproxy" proxy to debug this issue. Here's a fast way to stand up a proxy:

sudo port install python37 py37-pip

sudo pip-3.7 install mitmproxy ruamel.yaml ruamel.yaml.clib

mitmproxy-3.7 --listen-host servername --listen-port 3129 --set flow_detail=2 --set termlog_verbosity=debug --verbose

iPad Pro 12.9-inch, 2nd Gen, Wi-Fi

Posted on Sep 30, 2019 5:49 PM

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Answer 1

Oct 13, 2019 5:45 AM in response to essandess

I had this problem too. There is in fact a workaround - albeit a tedious one.

for every server mail needs to connect on the map port you have to specify "DIRECT".

For example:

function FindProxyForURL(url, host)
{
    if (dnsDomainIs(host, ".gmail.com") || (host == "gmail.com"))
    {
        return 'DIRECT';
    }
    return "PROXY 10.0.1.3:3129";
}

This obviously has side effects and is probably no good in a corporate environment where outbound access is prohibited...

Anyone knows a way to specify a rule only for http, ftp and https requests matching?

What url-schemes does your mitmproxy log for mail requests?

Cheers

Oskar

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Answer 2

essandess Author

Level 1

41 points

Nov 18, 2019 3:18 AM in response to unido!jhf

Still no resolution.

I strongly encourage everyone affected by this issue to open bug reports at https://feedbackassistant.apple.com/ . I posted one last month, and have not yet received any response, and their ticket field of "Recent Similar Reports" says "Less than 10", which indicates that it's not on their radar yet.

My ticket title is "Email Traffic Blocked by Automatic Proxy Settings in iOS and iPadOS".

Though using manual proxy settings provides a workaround for basic functionality, it offers none of the fine-grain capabilities used in PAC files, which is why we're using these in the first place.

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Email Traffic Blocked by Automatic Proxy Settings in iOS and iPadOS 13

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