Proxy authentication Mac Client kCFErrorDomainCFNetwork error 310

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  1. Matt
    Matt avatar
    1 posts
    Member since:
    Oct 2018

    Posted 13 Oct 2018 Link to this post

    Fiddler on Windows does not allow Mac client's to connect through to https sites when basic auth is enabled in Fiddler. Requests sent to http sites work OK. Also when basic auth is disabled the Mac can connect to both http and https sites without any problems.

    It seems that Fiddler does not support the Mac request which includes the http headers:

    • Proxy-Connection: keep-alive
    • Connection: keep-alive

    Fiddler responds with a Connection: close header.

    On the Mac this results in a kCFErrorDomainCFNetwork error 310. You can see this most easily in Safari. Note that other applications that do not use the Mac API, such as Chrome work fine.

    Testing a proxy server written in C# it seems that the Mac wants the connection to be kept alive and cannot handle Fiddler closing the connection. If the proxy server returns a Connection: keep-alive then the Mac seems to be able to respond with the basic auth credentials.


    Can Fiddler be changed to honour the keep-alive header when denying access with a 407 proxy authentication required?


    Fiddler v5.0.20182.28034 installed on Windows. Configured to be the system proxy, allow remote computers to connect - enabled, reuse client and server connections - enabled.
    Mac High Sierra 10:13.6. Mac network settings configured to use Windows machine with Fiddler as the Web Proxy (HTTP) and Secure Web Proxy (HTTPS)

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