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Fiddler Certificate Error Bypass Question

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Gary
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Gary asked on 01 Nov 2019, 10:36 PM

Dear all,

I am working on a project that requires communicating and transferring files to a server that requires SSL communication. I'm currently developing in C# .NET 4.7.2 and have utilized RestSharp to communicate to this server via POST command. The issue I am running into now is I keep getting a certificate chain error, and I have captured this with fiddler. Fiddler gives me a popup as shown in the attachments. The curious thing is, if I don't have fiddler open, my code will not work and the file transfer fails, however, when fiddler is open and monitoring all processes, it will popup the certificate error, and if I click YES then the file will get transferred correctly.

Can any of the devs provide some insight on how I should implement my code to perform the same behavior that Fiddler does when ignoring unsafe errors? I have searched other resources online and have not been able to find a working solution.

I have found a few blog articles like this one: https://www.telerik.com/blogs/understanding-fiddler-certificate-generators

which have provided some insight but if anyone has more detail on how this implementation works I hope to build something similar like this in my application.

 

Really appreciate your help,

Thank you!

garyd

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Eric R | Senior Technical Support Engineer
Telerik team
answered on 06 Nov 2019, 10:36 PM

Hi Gary,

I am not entirely certain that Fiddler is helping in this scenario. The error is likely caused by Certificate Pinning where the client HTTPS stack has a fixed mapping of hostnames to certificates and when it sees the mismatch is terminates the request.

The best option for this scenario is to use a certificate trusted by the server or authentication. 

I hope this helps. Please let me know if you need any additional information. Thank you for using the Fiddler Forums.

Regards,


Eric R | Technical Support Engineer
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Eric R | Senior Technical Support Engineer
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