Re: [PATCH 0/4] MdeModulePkg, OvmfPkg: support large CA cert list for HTTPS boot

["Palmer, Thomas" <thomas.palmer@hpe.com>]

Laszlo,

	(First, are you are plugfest? Let's chat.)

	Second, what need do you see for having KB worth of CA at UEFI's disposal? If HTTPS feature is primarily for PXE booting OS's, then it is likely the IT administrator who setup the PXE server also has a single CA they want use for PXE.   By allowing any and every CA to be installed (instead of having the user pick only the immediately needed CAs), we inadvertently open HTTPS to state-backed/well-financed malicious actors who can pay for quality SSL signing services.   (The less CAs then the less that can go wrong).

	This is not to prevent your patches going in, but would like to ensure manufacturers / admins know how to properly use the CA list

	
Regards,

Thomas Palmer

"I have only made this letter longer because I have not had the time to make it shorter" - Blaise Pascal


-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Laszlo Ersek
Sent: Wednesday, March 28, 2018 3:27 PM
To: edk2-devel-01 <edk2-devel@lists.01.org>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>; Eric Dong <eric.dong@intel.com>; Ard Biesheuvel <ard.biesheuvel@linaro.org>; Jordan Justen <jordan.l.justen@intel.com>; Gary Ching-Pang Lin <glin@suse.com>; Anthony Perard <anthony.perard@citrix.com>; Star Zeng <star.zeng@intel.com>
Subject: [edk2] [PATCH 0/4] MdeModulePkg, OvmfPkg: support large CA cert list for HTTPS boot

Repo:   https://github.com/lersek/edk2.git
Branch: https_cacert_rhbz_1536624

The trusted CA certificates for HTTPS boot can be specified in EFI_TLS_CA_CERTIFICATE_VARIABLE. The platform may choose to create this variable as volatile and set it on every boot as appropriate. The OVMF feature is that the virtualization host passes down an fw_cfg blob that carries the CA certs trusted on the host side, and the OVMF HTTPS boot will verify web servers against that certificate bundle. (For (part of) the host side implementation, refer to
<https://github.com/p11-glue/p11-kit/pull/137.)

The challenge for edk2 is that the CA cert list from the host side is huge; on my laptop it is 182KB when formatted to the EFI_SIGNATURE_LIST sequence expected by NetworkPkg/HttpDxe. Storing this in a non-volatile EFI_TLS_CA_CERTIFICATE_VARIABLE is out of the question, but even when making EFI_TLS_CA_CERTIFICATE_VARIABLE volatile, there are two limits that need raising:

(1) the individual limit on volatile variables,
(2) the cumulative limit on volatile variables.

Regarding (1), the edk2 variable driver does not distinguish a limit for volatile non-auth vs. non-volatile non-auth variables. The first patch introduces "PcdMaxVolatileVariableSize" for this, in a backwards compatible way (i.e. platforms that don't care need not learn about it).
The new PCD lets a platform raise the individual limit just for volatile non-auth variables.

Regarding (2), OvmfPkg/EmuVariableFvbRuntimeDxe has a bug where it abuses the cumulative limit on volatile variables for the live size of the emulated non-volatile variable store. The difference is that "volatile variables" are volatile on the UEFI service API level
(gRT->SetVariable() etc), and the driver stack expects the FVB impls to use the non-volatile storage PCDs (regardless of the actual FVB backing store). Patch #2 fixes this (without change in behavior) in OvmfPkg/EmuVariableFvbRuntimeDxe.

Patch #3 adds a bit of documentation to the OVMF DSC files, as a continuation of patch #2.

Patch #4 implements the feature, raising both limits (liberated in earlier patches) and populating EFI_TLS_CA_CERTIFICATE_VARIABLE from fw_cfg.

I've done reasonable HTTPS boot testing and regression testing too (including "-bios" with OVMF and pflash with ArmVirtQemu). Indepdent testing would be highly appreciated (feature and regression alike).

This email is too long and so are the commit messages, but I'm too tired to trim them; apologies.

Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Gary Ching-Pang Lin <glin@suse.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Julien Grall <julien.grall@linaro.org>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Star Zeng <star.zeng@intel.com>

Thanks,
Laszlo

Laszlo Ersek (4):
  MdeModulePkg/Variable/RuntimeDxe: introduce PcdMaxVolatileVariableSize
  OvmfPkg/EmuVariableFvbRuntimeDxe: stop using PcdVariableStoreSize
  OvmfPkg: annotate "PcdVariableStoreSize :=
    PcdFlashNvStorageVariableSize"
  OvmfPkg/TlsAuthConfigLib: configure trusted CA certs for HTTPS boot

 MdeModulePkg/MdeModulePkg.dec                                     |   8 ++
 MdeModulePkg/MdeModulePkg.uni                                     |   8 ++
 MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c             |  50 ++++++--
 MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.h             |  12 ++
 MdeModulePkg/Universal/Variable/RuntimeDxe/VariableRuntimeDxe.inf |   1 +
 MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmm.c          |   2 +-
 MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmm.inf        |   1 +
 OvmfPkg/EmuVariableFvbRuntimeDxe/Fvb.c                            |   6 +-
 OvmfPkg/EmuVariableFvbRuntimeDxe/Fvb.inf                          |   3 +-
 OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.c               | 133 ++++++++++++++++++++
 OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.inf             |  55 ++++++++
 OvmfPkg/OvmfPkgIa32.dsc                                           |  15 ++-
 OvmfPkg/OvmfPkgIa32X64.dsc                                        |  15 ++-
 OvmfPkg/OvmfPkgX64.dsc                                            |  15 ++-
 14 files changed, 308 insertions(+), 16 deletions(-)  create mode 100644 OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.c
 create mode 100644 OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.inf

--
2.14.1.3.gb7cf6e02401b

_______________________________________________
edk2-devel mailing list
edk2-devel@lists.01.org
https://lists.01.org/mailman/listinfo/edk2-devel