Safari causing HTTP 421 Errors

Safari on mobile devices and possibly desktop devices throws HTTP 421 errors for perfectly valid CDN URLs like https://food-access-images-cdn.azureedge.net/production/6cb808d2-5e77-480c-a114-f13034c92397.png . It causes people to be entirely unable to view images on Apple devices. Can you fix this issue? It's entirely explained here https://serverfault.com/a/938265 if you need to give your development team every detail they need to fix it.


Thank you,

Shane

Posted on Apr 24, 2023 1:04 PM

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Posted on Apr 26, 2023 7:51 AM

Ok, where can I address Apple?


Also, yes, I realize I didn't completely explain the bug, but it's outlined in the serverfault link. Essentially if you have two different images coming from two different domains using the same SSL certificate (like domain1.azureedge.net and domain2.azureedge.net), Safari tries to connect to the second domain using the same TLS connection from the first domain with the first domain in the SNI Header. Safari gets back a 421 Error because Azure considers that domain fronting, a security risk. Then Safari never retries the connection. We're probably going to consolidate to a single CDN domain, but it's still a pretty glaring issue so I thought I'd at least share as other browsers seem to reconnect gracefully, but on Safari no file ever loads.

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Question marked as Top-ranking reply

Apr 26, 2023 7:51 AM in response to John Galt

Ok, where can I address Apple?


Also, yes, I realize I didn't completely explain the bug, but it's outlined in the serverfault link. Essentially if you have two different images coming from two different domains using the same SSL certificate (like domain1.azureedge.net and domain2.azureedge.net), Safari tries to connect to the second domain using the same TLS connection from the first domain with the first domain in the SNI Header. Safari gets back a 421 Error because Azure considers that domain fronting, a security risk. Then Safari never retries the connection. We're probably going to consolidate to a single CDN domain, but it's still a pretty glaring issue so I thought I'd at least share as other browsers seem to reconnect gracefully, but on Safari no file ever loads.

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Safari causing HTTP 421 Errors

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