I want to confirm the specifications and behavior of Safari.
We have a system built on Microsoft Azure that uses Azure AD B2C for authentication. When we logging in, there is a phone authentication feature where a call is made to the registered phone number. However, this phone authentication does not work properly only on iPhone's Safari. The specific situation is listed below:
When performing phone authentication on iPhone's Safari, a call is made from Azure AD B2C, and pressing the # button on the Safari screen can be done. But then, it transitions to an error screen. We tried multiple iPhone devices and multiple iOS versions, but the result was the same. But when accessing the system on a PC, and performing phone authentication, it works without any errors. Also when we use browsers other than Safari (for example, Google Chrome and Firefox) on the iPhone, the phone authentication works without any errors, too. Even with Safari, if the device displaying the login screen and the device making the call are different, phone authentication works without any errors, too.(it fails if they are the same device).
We reached out Microsoft about this issue, and they responded that: The Azure resource called FrontDoor at the front end of Azure AD B2C supports the HTTP/2 protocol, and HTTP/2 protocol is used in communication with Safari. In Safari's HTTP/2 communication, when a call is received while the screen is displayed, a reset packet is sent to the web server (in this case, the web server is FrontDoor). This interrupts the session, causing a session termination error on the Azure AD B2C side, and phone authentication fails.
Therefore, we would like to ask you the following two points: In HTTP/2 communication, does the Safari browser send a reset packet to the web server when it receives a phone call? If so, what is the cause of this behavior? And are there any measures to prevent the reset packet from being sent?