Re: [edk2-devel] [RFC][PATCH 0/2] Introduce HTTPS Platform TLS policy

["Michael Brown" <mcb30@ipxe.org>]

On 29/12/2023 15:07, Chang, Abner via groups.io wrote:
> To locate TLS protocol from the HTTP handle and configure TLS configuration data at the return from EfiHttpRequest during that short window of non-blocking request is not reliable. It also doesn't make sense to ask upper layer application to do this when it first time invokes EfiHttpRequest.
> I already refactored TlsCreateChild to install TLS protocol on HTTP handle. I also implemented the corresponding code in Redfish REST EX to listen the installation of TLS protocol and hook the SetSessionData. It works fine on the system, however I really don’t like having the upper layer application to do this much just for overriding TLS configuration data. The code looked a specific implementation to hack the TLS protocol interface. Plus I still have to add few code in TlsConfigCertificate to skip configure certificate with checking TlsVerifyMethod.
> We should sit back to consider introducing a new protocol for upper layer application to provide their own TLS configuration data, as the root cause is that hard coded TLS configuration data in HttpSupport.c. We shouldn't have the code like that and add the burdens to application.
> 
> What my thought is as below and maybe more elegant than the patch a sent,
> - Still install TLS on HTTP handle, then upper layer application can listen to the installation of EFI TLS protocol to find the correct HTTP handle.
> - Move TLS_CONFIG_DATA in a public header file.
> - Introduce a new protocol called EDKII_HTTP_TLS_CONFIGURATION_DATA
> - Upper layer application installs this protocol with their own TLS_CONFIG_DATA.
> - TlsConfigureSession locates EDKII_HTTP_TLS_CONFIGURATION_DATA to replace the default TLS_CONFIG_DATA.
> 
> This way we can remove that hardcoded code and fix the root cause, also the upper layer application do not have to take the burden.
> What do you think?

Firstly, thank you very much for taking the time to dig through this and 
work towards a cleaner design - I, for one, really appreciate it.

I think we're completely agreed that installing the TLS protocols on the 
HTTP handle is the right thing to do - that seems to be a clear 
improvement over the status quo where there's no introspectable 
relationship between the two handles.

I'm torn on the use of TLS_CONFIG_DATA.  For better or worse, the 
existing and standardised EFI_TLS_CONFIGURATION_PROTOCOL is verb-based, 
using SetData() and GetData() methods.  Adding a noun-based protocol for 
TLS configuration seems to cut across this, with the potential to look 
confusing: a new reader of the code could legitimately wonder why the 
codebase contains two competing solutions to what is essentially the 
same problem.

Given that the verb-based approach of EFI_TLS_CONFIGURATION_PROTOCOL has 
made it as far as being standardised and included in the UEFI 
specification, I think we probably need to accept that this is the 
"correct" way to perform TLS configuration within UEFI code.  The 
problem with HttpsSupport.c then becomes that there is no good 
opportunity for a consumer to call SetData(), since (a) 
EFI_TLS_CONFIGURATION_PROTOCOL comes into existence only halfway through 
the call to EFI_HTTP_PROTOCOL.Request() and (b) the call to 
TlsConfigureSession() will overwrite the configuration anyway.

Is there a way that TlsConfigureSession() could sensibly provide an 
opportunity for the consumer to make calls to SetData(), so that the 
consumer could cleanly override any default configuration?

Looking through the code, TlsConfigureSession() is called only from 
HttpInitSession(), which in turn is called only from EfiHttpRequest(). 
This call is followed immediately by the line:

   HttpNotify (HttpEventInitSession, Status);

which seems to already use an existing EDKII_HTTP_CALLBACK_PROTOCOL to 
notify an arbitrary list of interested consumers that an event has taken 
place (in this case, that a session has just been initialised).

What do you think about:

- installing TLS on HTTP handle (as you have already implemented)

- using EDKII_HTTP_CALLBACK_PROTOCOL to catch the HttpEventInitSession 
and perform whatever calls are needed to SetData() to modify the TLS 
configuration?

Thanks,

Michael



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