Re: [edk2-devel] [PATCH v2] OvmfPkg: use DxeTpmMeasurementLib if and only if TPM2_ENABLE

["Laszlo Ersek" <lersek@redhat.com>]

On 07/04/19 06:07, Gary Lin wrote:
> (a) OvmfPkg first had to resolve the TpmMeasurementLib class -- for
>     SECURE_BOOT_ENABLE only -- when the DxeImageVerificationLib instance
>     became dependent on TpmMeasurementLib. For details, refer to commit
>     0d28d286bf4d ("OvmfPkg: resolve TpmMeasurementLib dependency
>     introduced in r14687", 2013-09-21).
> 
> (b) At the time, only one instance of TpmMeasurementLib existed, namely
>     DxeTpmMeasurementLib. This lib instance didn't do anything -- like it
>     was desirable for OVMF --, because OVMF didn't include any Tcg / TrEE
>     protocol implementations.
> 
> (c) In commit 308521b13354 ("MdeModulePkg: Move TpmMeasurementLib
>     LibraryClass from SecurityPkg", 2015-07-01), TpmMeasurementLibNull was
>     introduced.
> 
> (d) In commit 285542ebbb03 ("OvmfPkg: Link AuthVariableLib for following
>     merged variable driver deploy", 2015-07-01), a TpmMeasurementLib
>     resolution became necessary regardless of SECURE_BOOT_ENABLE. And so
>     TpmMeasurementLib was resolved to TpmMeasurementLibNull in OVMF, but
>     only in the non-SECURE_BOOT_ENABLE case. This step -- possibly, the
>     larger series containing commit 285542ebbb03 -- missed an opportunity
>     for simplification: given (b), the DxeTpmMeasurementLib instance
>     should have been simply replaced with the TpmMeasurementLibNull
>     instance, regardless of SECURE_BOOT_ENABLE.
> 
> (e) In commit 1abfa4ce4835 ("Add TPM2 support defined in trusted computing
>     group.", 2015-08-13), the TrEE dependency was replaced with a Tcg2
>     dependency in DxeTpmMeasurementLib.
> 
> (f) Starting with commit 0c0a50d6b3ff ("OvmfPkg: include Tcg2Dxe module",
>     2018-03-09), OVMF would include a Tcg2 protocol implementation,
>     thereby satisfying DxeTpmMeasurementLib's dependency. With
>     TPM2_ENABLE, it would actually make sense to consume
>     DxeTpmMeasurementLib -- however, DxeTpmMeasurementLib would never be
>     used without SECURE_BOOT_ENABLE.
> 
> Therefore, we have the following four scenarios:
> 
> - TPM2_ENABLE + SECURE_BOOT_ENABLE: works as expected.
> 
> - Neither enabled: works as expected.
> 
> - Only TPM2_ENABLE: this build is currently incorrect, because
>   Variable/RuntimeDxe consumes TpmMeasurementLib directly, but
>   TpmMeasureAndLogData() will never reach the TPM because we link
>   TpmMeasurementLibNull into the variable driver. This is a problem from
>   the larger series containing (f).
> 
> - Only SECURE_BOOT_ENABLE: this build works as expected, but it is
>   wasteful -- given that the protocol database will never contain Tcg2
>   without TPM2_ENABLE, we should simply use TpmMeasurementLibNull. This is
>   a problem from (d).
> 
> Resolving TpmMeasurementLib to DxeTpmMeasurementLib as a function of
> *only* TPM2_ENABLE, we can fix / optimize the last two cases.
> 
> v2:
>   - Amend the title and description suggested by Laszlo
>   - Move TpmMeasurementLib to the existed TPM2_ENABLE block
> 
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
> Cc: Stefan Berger <stefanb@linux.ibm.com>
> Signed-off-by: Gary Lin <glin@suse.com>
> ---
>  OvmfPkg/OvmfPkgIa32.dsc    | 4 ++--
>  OvmfPkg/OvmfPkgIa32X64.dsc | 4 ++--
>  OvmfPkg/OvmfPkgX64.dsc     | 4 ++--
>  3 files changed, 6 insertions(+), 6 deletions(-)

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Pushed as commit 1ec05b81e59f.

Thanks!
Laszlo

> diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
> index 87716123997a..5bbf87540ab9 100644
> --- a/OvmfPkg/OvmfPkgIa32.dsc
> +++ b/OvmfPkg/OvmfPkgIa32.dsc
> @@ -178,10 +178,8 @@ [LibraryClasses]
>  
>  !if $(SECURE_BOOT_ENABLE) == TRUE
>    PlatformSecureLib|OvmfPkg/Library/PlatformSecureLib/PlatformSecureLib.inf
> -  TpmMeasurementLib|SecurityPkg/Library/DxeTpmMeasurementLib/DxeTpmMeasurementLib.inf
>    AuthVariableLib|SecurityPkg/Library/AuthVariableLib/AuthVariableLib.inf
>  !else
> -  TpmMeasurementLib|MdeModulePkg/Library/TpmMeasurementLibNull/TpmMeasurementLibNull.inf
>    AuthVariableLib|MdeModulePkg/Library/AuthVariableLibNull/AuthVariableLibNull.inf
>  !endif
>    VarCheckLib|MdeModulePkg/Library/VarCheckLib/VarCheckLib.inf
> @@ -207,8 +205,10 @@ [LibraryClasses]
>    Tpm2CommandLib|SecurityPkg/Library/Tpm2CommandLib/Tpm2CommandLib.inf
>    Tcg2PhysicalPresenceLib|OvmfPkg/Library/Tcg2PhysicalPresenceLibQemu/DxeTcg2PhysicalPresenceLib.inf
>    Tcg2PpVendorLib|SecurityPkg/Library/Tcg2PpVendorLibNull/Tcg2PpVendorLibNull.inf
> +  TpmMeasurementLib|SecurityPkg/Library/DxeTpmMeasurementLib/DxeTpmMeasurementLib.inf
>  !else
>    Tcg2PhysicalPresenceLib|OvmfPkg/Library/Tcg2PhysicalPresenceLibNull/DxeTcg2PhysicalPresenceLib.inf
> +  TpmMeasurementLib|MdeModulePkg/Library/TpmMeasurementLibNull/TpmMeasurementLibNull.inf
>  !endif
>  
>  [LibraryClasses.common]
> diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
> index ad20531ceb8b..5015e92b6eea 100644
> --- a/OvmfPkg/OvmfPkgIa32X64.dsc
> +++ b/OvmfPkg/OvmfPkgIa32X64.dsc
> @@ -183,10 +183,8 @@ [LibraryClasses]
>  
>  !if $(SECURE_BOOT_ENABLE) == TRUE
>    PlatformSecureLib|OvmfPkg/Library/PlatformSecureLib/PlatformSecureLib.inf
> -  TpmMeasurementLib|SecurityPkg/Library/DxeTpmMeasurementLib/DxeTpmMeasurementLib.inf
>    AuthVariableLib|SecurityPkg/Library/AuthVariableLib/AuthVariableLib.inf
>  !else
> -  TpmMeasurementLib|MdeModulePkg/Library/TpmMeasurementLibNull/TpmMeasurementLibNull.inf
>    AuthVariableLib|MdeModulePkg/Library/AuthVariableLibNull/AuthVariableLibNull.inf
>  !endif
>    VarCheckLib|MdeModulePkg/Library/VarCheckLib/VarCheckLib.inf
> @@ -212,8 +210,10 @@ [LibraryClasses]
>    Tpm2CommandLib|SecurityPkg/Library/Tpm2CommandLib/Tpm2CommandLib.inf
>    Tcg2PhysicalPresenceLib|OvmfPkg/Library/Tcg2PhysicalPresenceLibQemu/DxeTcg2PhysicalPresenceLib.inf
>    Tcg2PpVendorLib|SecurityPkg/Library/Tcg2PpVendorLibNull/Tcg2PpVendorLibNull.inf
> +  TpmMeasurementLib|SecurityPkg/Library/DxeTpmMeasurementLib/DxeTpmMeasurementLib.inf
>  !else
>    Tcg2PhysicalPresenceLib|OvmfPkg/Library/Tcg2PhysicalPresenceLibNull/DxeTcg2PhysicalPresenceLib.inf
> +  TpmMeasurementLib|MdeModulePkg/Library/TpmMeasurementLibNull/TpmMeasurementLibNull.inf
>  !endif
>  
>  [LibraryClasses.common]
> diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
> index 0542ac2235b4..dda8dac18441 100644
> --- a/OvmfPkg/OvmfPkgX64.dsc
> +++ b/OvmfPkg/OvmfPkgX64.dsc
> @@ -183,10 +183,8 @@ [LibraryClasses]
>  
>  !if $(SECURE_BOOT_ENABLE) == TRUE
>    PlatformSecureLib|OvmfPkg/Library/PlatformSecureLib/PlatformSecureLib.inf
> -  TpmMeasurementLib|SecurityPkg/Library/DxeTpmMeasurementLib/DxeTpmMeasurementLib.inf
>    AuthVariableLib|SecurityPkg/Library/AuthVariableLib/AuthVariableLib.inf
>  !else
> -  TpmMeasurementLib|MdeModulePkg/Library/TpmMeasurementLibNull/TpmMeasurementLibNull.inf
>    AuthVariableLib|MdeModulePkg/Library/AuthVariableLibNull/AuthVariableLibNull.inf
>  !endif
>    VarCheckLib|MdeModulePkg/Library/VarCheckLib/VarCheckLib.inf
> @@ -212,8 +210,10 @@ [LibraryClasses]
>    Tpm2CommandLib|SecurityPkg/Library/Tpm2CommandLib/Tpm2CommandLib.inf
>    Tcg2PhysicalPresenceLib|OvmfPkg/Library/Tcg2PhysicalPresenceLibQemu/DxeTcg2PhysicalPresenceLib.inf
>    Tcg2PpVendorLib|SecurityPkg/Library/Tcg2PpVendorLibNull/Tcg2PpVendorLibNull.inf
> +  TpmMeasurementLib|SecurityPkg/Library/DxeTpmMeasurementLib/DxeTpmMeasurementLib.inf
>  !else
>    Tcg2PhysicalPresenceLib|OvmfPkg/Library/Tcg2PhysicalPresenceLibNull/DxeTcg2PhysicalPresenceLib.inf
> +  TpmMeasurementLib|MdeModulePkg/Library/TpmMeasurementLibNull/TpmMeasurementLibNull.inf
>  !endif
>  
>  [LibraryClasses.common]
>