How I solved the Safari 13 and High Sierra problem with idmsa.apple.com unsecure connection (all Apple logins)

• I have had this problem for at least a year. I can't use Safari on my MBP 15" (HighSierra 10.13.6) to access the apple store, use iCloud.com, or check my orders; instead, I have to use Chrome or Firefox (on the same mac) to access. When I tried installing the certificate "Apple IST CA 2 - G1 Certificate" as per above, I get a warning that the certificates are locked and I can't get past that error.
• I tried the Python script mentioned below and that was, finally and thank god, successful. (See https://discussions.apple.com/thread/251210686?answerId=252326921022#252326921022).

Thanks to all for finally getting a fix that works.

I solved this without installing the intermediate certificate. The issue actually has to do with certificate pinning:

https://discussions.apple.com/thread/251210686?answerId=252326921022#252326921022

thanks! that worked.

I did see the python script to fix the pinning pretty interesting, but already had installed the cert.

so this is due to OS X High Sierra bug of some kind.

thanks again for the help everyone

Thank you Taro-71- consider yourself a genius!

This problem has been bugging me for ages! Running High Sierra and I keep updating to the latest version of Safari and yet the login problem kept occuring- I had to use Chrome, ironically, to log in to any Apple sites, such as this, which needed a sign in.

The certificate solved all that and it was an easy fix.

I'm really surprised that something so straight forward wasn't captured and rectified in one of the software updates.

Thanks again!

It is really unbelievable impudence, but typical for Apple's arrogance and ignorance, that this problem, about which so many users complain, is not communicated by Apple and they are left alone with the problem.

Thanks to Taro-71 for the solution, which I had to search for a very long time.

I did. It didn’t work either. It was actually across all of my devices and I suspect it was a lingering issue from the iCloud outage earlier in the day. The next day around 1-2am EST it started working again.

Brilliant!!!

You did what Apple has been trying to fix for months, thanks! :)

I think Taro-71should be immediately elevated to Level 10 and offered a job as an Apple Engineer!!

I bid Level 11 & 2 Apple Engineers! :)

Hello Taro-71. This solved my problem (installing the intermediate certificate in Keychain Access). Thank you!!! :-)

Thank you. This fixed my Safari 12 and High Sierra problem.

Thank you, Taro-71. This seems to have worked for me.

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srb

You sir are a genius. Thank you very much for posting this!

Thank you so much for this, after hours of time machine restore and many other attempts to solve this, I came across your post, I did as you instructed and it worked, thank you so much.