Re: setting the TLS cipher list for HTTPS booting

["Wu, Jiaxin" <jiaxin.wu@intel.com>]

Leaving the variable up to the platform setting is good to me. 

Mike,

If you have no comments, we will follow the variable solution. 

Thanks,
Jiaxin

> -----Original Message-----
> From: Laszlo Ersek [mailto:lersek@redhat.com]
> Sent: Monday, February 5, 2018 6:47 PM
> To: Wu, Jiaxin <jiaxin.wu@intel.com>; Kinney, Michael D
> <michael.d.kinney@intel.com>; Fu, Siyuan <siyuan.fu@intel.com>; Ye, Ting
> <ting.ye@intel.com>; Li, Ruth <ruth.li@intel.com>; Long, Qin
> <qin.long@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>; Hsiung, Harry L
> <harry.l.hsiung@intel.com>
> Cc: edk2-devel-01 <edk2-devel@lists.01.org>
> Subject: Re: setting the TLS cipher list for HTTPS booting
> 
> On 02/05/18 04:33, Wu, Jiaxin wrote:
> > Hi Laszlo,
> >
> > In recent days, we received the comment from Kinney about the PCD
> > usage in UEFI driver.  Kinney doesn't recommend us to use the *dynamic
> > PCD* in *soft-loading* UEFI driver even though it's not prohibited.
> >
> > So, we want to confirm with you whether this is the urgent request
> > need us to support it ASAP or it's in low priority.
> >
> > If you need us support the feature ASAP, we can use the  private
> > variable solution as we discussed before since there is no security
> > issue and the size requirement is not big.
> >
> > If not urgency, we might consider whether need to define a platform to
> > driver configuration protocol or not. You know it will take a long
> > time to scandalize one protocol for platform HTTPS configuration in
> > the future UEFI spec.
> 
> The variable approach sounds good to me, but with a small twist:
> 
> Could we please leave it up to the platform whether the private variable
> is non-volatile versus volatile? Because platform X might want to
> configure the cipher suite list once, permanently, while platform Y
> might want to configure the cipher suite list dynamically on each boot.
> For platform Y, spending any flash space (and flash writing time) on the
> variable is superfluous.
> 
> For QEMU / OVMF specifically, I would prefer a volatile, boot-time only
> variable. After setting this variable, I think OVMF platform code should
> even lock it down with the edk2 variable lock protocol. In effect this
> would behave like a "read only" PCD -- no flash impact at all.
> 
> As long as HttpDxe only calls gRT->GetVariable() (or equivalent wrappers
> from UefiLib) on the new variable, the variable's attributes should not
> matter; they can be left to the platform.
> 
> Thanks!
> Laszlo
> 
> 
> >> -----Original Message-----
> >> From: Laszlo Ersek [mailto:lersek@redhat.com]
> >> Sent: Thursday, January 25, 2018 8:42 PM
> >> To: Wu, Jiaxin <jiaxin.wu@intel.com>; Fu, Siyuan <siyuan.fu@intel.com>;
> Ye,
> >> Ting <ting.ye@intel.com>; Long, Qin <qin.long@intel.com>; Yao, Jiewen
> >> <jiewen.yao@intel.com>; Hsiung, Harry L <harry.l.hsiung@intel.com>
> >> Cc: edk2-devel-01 <edk2-devel@lists.01.org>
> >> Subject: Re: setting the TLS cipher list for HTTPS booting
> >>
> >> On 01/25/18 05:52, Wu, Jiaxin wrote:
> >>> Hi Laszlo,
> >>>
> >>> The HttpDxe driver needs to install the Driver Binding Protocol so as
> >>> to check if a specific controller is supported by HttpDxe. HttpDxe
> >>> can only be started if the TcpServiceBindingProtocol existed. So, it
> >>> has to follow the UEFI Driver Model.
> >>>
> >>> For the PCD usage, I think it should be fine to cover the
> >>> configuration of UEFI Drivers through the PCD settings. The
> >>> requirement of *.inf needs to include the PcdLib and the section of
> >>> [Pcd]. We already have the similar pattern for this usage, for
> >>> example, Ps2KeyboardDxe, PciBusDxe, PciSioSerialDxe, and etc in
> >>> MdeModulePkg. Besides, there are some advantages by using PCD
> >>> compared to the variable. First, PCD is one kind of interface that
> >>> more formal than a private variable, the setting by PCD is more
> >>> acceptable by the consumer. Secondly, from a *security* standpoint,
> >>> variable can be dumped easily from the flash region. Here, even
> >>> though it's no security impact towards the cipher list storage
> >>> because it will be public shared to remote server, but we need to
> >>> think and *align* with other configurations for TLS in HTTPS level.
> >>> For example, in the future, we might support the HTTPS mutual
> >>> authentication, than the host PrivateKey/Password
> >>> (EfiTlsConfigDataTypeHostPrivateKey) *mustn't* be saved as a variable
> >>> due to its confidentiality, while PCD is good choice. At that time,
> >>> we will also provide the PCD for EfiTlsConfigDataTypeCACertificate,
> >>> which is currently setting by the variable (TlsCaCertificate), so as
> >>> to align all the configuration setting on one line, which can reduce
> >>> the complexity of platform usage. Finally, we can also save the
> >>> variable space.
> >>>
> >>> From the above, the dynamic PCD is a solution I still preferred.
> >>
> >> OK, it works for me. Thanks!
> >> Laszlo