Re: [PATCH 4/4] OvmfPkg/TlsAuthConfigLib: configure trusted CA certs for HTTPS boot

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On 28 March 2018 at 21:26, Laszlo Ersek <lersek@redhat.com> wrote:
> Introduce TlsAuthConfigLib to read the list of trusted CA certificates
> from fw_cfg and to store it to EFI_TLS_CA_CERTIFICATE_VARIABLE.
>
> The fw_cfg file is formatted by the "p11-kit" and "update-ca-trust"
> utilities on the host side, so that the host settings take effect in guest
> HTTPS boot as well. QEMU forwards the file intact to the firmware. The
> contents are sanity-checked by NetworkPkg/HttpDxe code that was added in
> commit 0fd13678a681.
>
> Link TlsAuthConfigLib via NULL resolution into TlsAuthConfigDxe. This sets
> EFI_TLS_CA_CERTIFICATE_VARIABLE in time for both
> NetworkPkg/TlsAuthConfigDxe (for possible HII interaction with the user)
> and for NetworkPkg/HttpDxe (for the effective TLS configuration).
>
> The file formatted by "p11-kit" can be large. On a RHEL-7 host, the the
> Mozilla CA root certificate bundle -- installed with the "ca-certificates"
> package -- is processed into a 182KB file. Thus, create
> EFI_TLS_CA_CERTIFICATE_VARIABLE as a volatile & boot-time only variable.
> Also, in TLS_ENABLE builds, set the cumulative limit for volatile
> variables (PcdVariableStoreSize) to 512KB, and the individual limit for
> the same (PcdMaxVolatileVariableSize) to 256KB.
>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Gary Ching-Pang Lin <glin@suse.com>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Laszlo Ersek <lersek@redhat.com>

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> ---
>  OvmfPkg/OvmfPkgIa32.dsc                               |  13 +-
>  OvmfPkg/OvmfPkgIa32X64.dsc                            |  13 +-
>  OvmfPkg/OvmfPkgX64.dsc                                |  13 +-
>  OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.inf |  55 ++++++++
>  OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.c   | 133 ++++++++++++++++++++
>  5 files changed, 224 insertions(+), 3 deletions(-)
>
> diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
> index 7664b50ddef9..c9eb248506c5 100644
> --- a/OvmfPkg/OvmfPkgIa32.dsc
> +++ b/OvmfPkg/OvmfPkgIa32.dsc
> @@ -439,15 +439,23 @@ [PcdsFixedAtBuild]
>  !if ($(FD_SIZE_IN_KB) == 1024) || ($(FD_SIZE_IN_KB) == 2048)
>    gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x2000
>    gEfiMdeModulePkgTokenSpaceGuid.PcdMaxAuthVariableSize|0x2800
> +!if $(TLS_ENABLE) == FALSE
>    # match PcdFlashNvStorageVariableSize purely for convenience
>    gEfiMdeModulePkgTokenSpaceGuid.PcdVariableStoreSize|0xe000
>  !endif
> +!endif
>  !if $(FD_SIZE_IN_KB) == 4096
>    gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x8400
>    gEfiMdeModulePkgTokenSpaceGuid.PcdMaxAuthVariableSize|0x8400
> +!if $(TLS_ENABLE) == FALSE
>    # match PcdFlashNvStorageVariableSize purely for convenience
>    gEfiMdeModulePkgTokenSpaceGuid.PcdVariableStoreSize|0x40000
>  !endif
> +!endif
> +!if $(TLS_ENABLE) == TRUE
> +  gEfiMdeModulePkgTokenSpaceGuid.PcdVariableStoreSize|0x80000
> +  gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVolatileVariableSize|0x40000
> +!endif
>
>    gEfiMdeModulePkgTokenSpaceGuid.PcdVpdBaseAddress|0x0
>
> @@ -796,7 +804,10 @@ [Components]
>  !endif
>  !if $(TLS_ENABLE) == TRUE
>    NetworkPkg/TlsDxe/TlsDxe.inf
> -  NetworkPkg/TlsAuthConfigDxe/TlsAuthConfigDxe.inf
> +  NetworkPkg/TlsAuthConfigDxe/TlsAuthConfigDxe.inf {
> +    <LibraryClasses>
> +      NULL|OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.inf
> +  }
>  !endif
>    OvmfPkg/VirtioNetDxe/VirtioNet.inf
>
> diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
> index e5969090d437..17aef2d4830f 100644
> --- a/OvmfPkg/OvmfPkgIa32X64.dsc
> +++ b/OvmfPkg/OvmfPkgIa32X64.dsc
> @@ -444,15 +444,23 @@ [PcdsFixedAtBuild]
>  !if ($(FD_SIZE_IN_KB) == 1024) || ($(FD_SIZE_IN_KB) == 2048)
>    gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x2000
>    gEfiMdeModulePkgTokenSpaceGuid.PcdMaxAuthVariableSize|0x2800
> +!if $(TLS_ENABLE) == FALSE
>    # match PcdFlashNvStorageVariableSize purely for convenience
>    gEfiMdeModulePkgTokenSpaceGuid.PcdVariableStoreSize|0xe000
>  !endif
> +!endif
>  !if $(FD_SIZE_IN_KB) == 4096
>    gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x8400
>    gEfiMdeModulePkgTokenSpaceGuid.PcdMaxAuthVariableSize|0x8400
> +!if $(TLS_ENABLE) == FALSE
>    # match PcdFlashNvStorageVariableSize purely for convenience
>    gEfiMdeModulePkgTokenSpaceGuid.PcdVariableStoreSize|0x40000
>  !endif
> +!endif
> +!if $(TLS_ENABLE) == TRUE
> +  gEfiMdeModulePkgTokenSpaceGuid.PcdVariableStoreSize|0x80000
> +  gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVolatileVariableSize|0x40000
> +!endif
>
>    gEfiMdeModulePkgTokenSpaceGuid.PcdVpdBaseAddress|0x0
>
> @@ -805,7 +813,10 @@ [Components.X64]
>  !endif
>  !if $(TLS_ENABLE) == TRUE
>    NetworkPkg/TlsDxe/TlsDxe.inf
> -  NetworkPkg/TlsAuthConfigDxe/TlsAuthConfigDxe.inf
> +  NetworkPkg/TlsAuthConfigDxe/TlsAuthConfigDxe.inf {
> +    <LibraryClasses>
> +      NULL|OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.inf
> +  }
>  !endif
>    OvmfPkg/VirtioNetDxe/VirtioNet.inf
>
> diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
> index 7197c1984a7c..8af763ea9e9e 100644
> --- a/OvmfPkg/OvmfPkgX64.dsc
> +++ b/OvmfPkg/OvmfPkgX64.dsc
> @@ -444,15 +444,23 @@ [PcdsFixedAtBuild]
>  !if ($(FD_SIZE_IN_KB) == 1024) || ($(FD_SIZE_IN_KB) == 2048)
>    gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x2000
>    gEfiMdeModulePkgTokenSpaceGuid.PcdMaxAuthVariableSize|0x2800
> +!if $(TLS_ENABLE) == FALSE
>    # match PcdFlashNvStorageVariableSize purely for convenience
>    gEfiMdeModulePkgTokenSpaceGuid.PcdVariableStoreSize|0xe000
>  !endif
> +!endif
>  !if $(FD_SIZE_IN_KB) == 4096
>    gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x8400
>    gEfiMdeModulePkgTokenSpaceGuid.PcdMaxAuthVariableSize|0x8400
> +!if $(TLS_ENABLE) == FALSE
>    # match PcdFlashNvStorageVariableSize purely for convenience
>    gEfiMdeModulePkgTokenSpaceGuid.PcdVariableStoreSize|0x40000
>  !endif
> +!endif
> +!if $(TLS_ENABLE) == TRUE
> +  gEfiMdeModulePkgTokenSpaceGuid.PcdVariableStoreSize|0x80000
> +  gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVolatileVariableSize|0x40000
> +!endif
>
>    gEfiMdeModulePkgTokenSpaceGuid.PcdVpdBaseAddress|0x0
>
> @@ -803,7 +811,10 @@ [Components]
>  !endif
>  !if $(TLS_ENABLE) == TRUE
>    NetworkPkg/TlsDxe/TlsDxe.inf
> -  NetworkPkg/TlsAuthConfigDxe/TlsAuthConfigDxe.inf
> +  NetworkPkg/TlsAuthConfigDxe/TlsAuthConfigDxe.inf {
> +    <LibraryClasses>
> +      NULL|OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.inf
> +  }
>  !endif
>    OvmfPkg/VirtioNetDxe/VirtioNet.inf
>
> diff --git a/OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.inf b/OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.inf
> new file mode 100644
> index 000000000000..5f83582a8313
> --- /dev/null
> +++ b/OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.inf
> @@ -0,0 +1,55 @@
> +## @file
> +#
> +# A hook-in library for NetworkPkg/TlsAuthConfigDxe, in order to set volatile
> +# variables related to TLS configuration, before TlsAuthConfigDxe or HttpDxe
> +# (which is a UEFI_DRIVER) consume them.
> +#
> +# Copyright (C) 2013, 2015, 2018, Red Hat, Inc.
> +# Copyright (c) 2008 - 2012, Intel Corporation. All rights reserved.<BR>
> +#
> +# This program and the accompanying materials are licensed and made available
> +# under the terms and conditions of the BSD License which accompanies this
> +# distribution. The full text of the license may be found at
> +# http://opensource.org/licenses/bsd-license.php
> +#
> +# THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
> +# WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
> +#
> +##
> +
> +[Defines]
> +  INF_VERSION                    = 1.26
> +  BASE_NAME                      = TlsAuthConfigLib
> +  FILE_GUID                      = 660AB627-4C5F-4D42-A3B6-BD021E9028BD
> +  MODULE_TYPE                    = BASE
> +  VERSION_STRING                 = 1.0
> +  LIBRARY_CLASS                  = TlsAuthConfigLib|DXE_DRIVER
> +  CONSTRUCTOR                    = TlsAuthConfigInit
> +
> +#
> +# The following information is for reference only and not required by the build
> +# tools.
> +#
> +#  VALID_ARCHITECTURES           = IA32 X64 ARM AARCH64
> +#
> +
> +[Sources]
> +  TlsAuthConfigLib.c
> +
> +[Packages]
> +  MdePkg/MdePkg.dec
> +  NetworkPkg/NetworkPkg.dec
> +  OvmfPkg/OvmfPkg.dec
> +
> +[LibraryClasses]
> +  BaseLib
> +  DebugLib
> +  MemoryAllocationLib
> +  QemuFwCfgLib
> +  UefiRuntimeServicesTableLib
> +
> +[Guids]
> +  gEfiTlsCaCertificateGuid ## PRODUCES ## Variable:L"TlsCaCertificate"
> +
> +[Depex]
> +  gEfiVariableWriteArchProtocolGuid
> diff --git a/OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.c b/OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.c
> new file mode 100644
> index 000000000000..b5b33bc4fc69
> --- /dev/null
> +++ b/OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.c
> @@ -0,0 +1,133 @@
> +/** @file
> +
> +  A hook-in library for NetworkPkg/TlsAuthConfigDxe, in order to set volatile
> +  variables related to TLS configuration, before TlsAuthConfigDxe or HttpDxe
> +  (which is a UEFI_DRIVER) consume them.
> +
> +  Copyright (C) 2013, 2015, 2018, Red Hat, Inc.
> +  Copyright (c) 2008 - 2012, Intel Corporation. All rights reserved.<BR>
> +
> +  This program and the accompanying materials are licensed and made available
> +  under the terms and conditions of the BSD License which accompanies this
> +  distribution. The full text of the license may be found at
> +  http://opensource.org/licenses/bsd-license.php
> +
> +  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
> +  WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
> +
> +**/
> +
> +#include <Uefi/UefiBaseType.h>
> +#include <Uefi/UefiSpec.h>
> +
> +#include <Guid/TlsAuthentication.h>
> +
> +#include <Library/BaseLib.h>
> +#include <Library/DebugLib.h>
> +#include <Library/MemoryAllocationLib.h>
> +#include <Library/QemuFwCfgLib.h>
> +#include <Library/UefiRuntimeServicesTableLib.h>
> +
> +/**
> +  Read the list of trusted CA certificates from the fw_cfg file
> +  "etc/edk2/https/cacerts", and store it to
> +  gEfiTlsCaCertificateGuid:EFI_TLS_CA_CERTIFICATE_VARIABLE.
> +
> +  The contents are validated (for well-formedness) by NetworkPkg/HttpDxe.
> +**/
> +STATIC
> +VOID
> +SetCaCerts (
> +  VOID
> +  )
> +{
> +  EFI_STATUS           Status;
> +  FIRMWARE_CONFIG_ITEM HttpsCaCertsItem;
> +  UINTN                HttpsCaCertsSize;
> +  VOID                 *HttpsCaCerts;
> +
> +  Status = QemuFwCfgFindFile ("etc/edk2/https/cacerts", &HttpsCaCertsItem,
> +             &HttpsCaCertsSize);
> +  if (EFI_ERROR (Status)) {
> +    DEBUG ((DEBUG_VERBOSE, "%a:%a: not touching CA cert list\n",
> +      gEfiCallerBaseName, __FUNCTION__));
> +    return;
> +  }
> +
> +  //
> +  // Delete the current EFI_TLS_CA_CERTIFICATE_VARIABLE if it exists. This
> +  // serves two purposes:
> +  //
> +  // (a) If the variable exists with EFI_VARIABLE_NON_VOLATILE attribute, we
> +  //     cannot make it volatile without deleting it first.
> +  //
> +  // (b) If we fail to recreate the variable later, deleting the current one is
> +  //     still justified if the fw_cfg file exists. Emptying the set of trusted
> +  //     CA certificates will fail HTTPS boot, which is better than trusting
> +  //     any certificate that's possibly missing from the fw_cfg file.
> +  //
> +  Status = gRT->SetVariable (
> +                  EFI_TLS_CA_CERTIFICATE_VARIABLE, // VariableName
> +                  &gEfiTlsCaCertificateGuid,       // VendorGuid
> +                  0,                               // Attributes
> +                  0,                               // DataSize
> +                  NULL                             // Data
> +                  );
> +  if (EFI_ERROR (Status) && (Status != EFI_NOT_FOUND)) {
> +    //
> +    // This is fatal.
> +    //
> +    DEBUG ((DEBUG_ERROR, "%a:%a: failed to delete %g:\"%s\"\n",
> +      gEfiCallerBaseName, __FUNCTION__, &gEfiTlsCaCertificateGuid,
> +      EFI_TLS_CA_CERTIFICATE_VARIABLE));
> +    ASSERT_EFI_ERROR (Status);
> +    CpuDeadLoop ();
> +  }
> +
> +  if (HttpsCaCertsSize == 0) {
> +    DEBUG ((DEBUG_VERBOSE, "%a:%a: applied empty CA cert list\n",
> +      gEfiCallerBaseName, __FUNCTION__));
> +    return;
> +  }
> +
> +  HttpsCaCerts = AllocatePool (HttpsCaCertsSize);
> +  if (HttpsCaCerts == NULL) {
> +    DEBUG ((DEBUG_ERROR, "%a:%a: failed to allocate HttpsCaCerts\n",
> +      gEfiCallerBaseName, __FUNCTION__));
> +    return;
> +  }
> +
> +  QemuFwCfgSelectItem (HttpsCaCertsItem);
> +  QemuFwCfgReadBytes (HttpsCaCertsSize, HttpsCaCerts);
> +
> +  Status = gRT->SetVariable (
> +                  EFI_TLS_CA_CERTIFICATE_VARIABLE, // VariableName
> +                  &gEfiTlsCaCertificateGuid,       // VendorGuid
> +                  EFI_VARIABLE_BOOTSERVICE_ACCESS, // Attributes
> +                  HttpsCaCertsSize,                // DataSize
> +                  HttpsCaCerts                     // Data
> +                  );
> +  if (EFI_ERROR (Status)) {
> +    DEBUG ((DEBUG_ERROR, "%a:%a: failed to set %g:\"%s\": %r\n",
> +      gEfiCallerBaseName, __FUNCTION__, &gEfiTlsCaCertificateGuid,
> +      EFI_TLS_CA_CERTIFICATE_VARIABLE, Status));
> +    goto FreeHttpsCaCerts;
> +  }
> +
> +  DEBUG ((DEBUG_VERBOSE, "%a:%a: stored CA cert list (%Lu byte(s))\n",
> +    gEfiCallerBaseName, __FUNCTION__, (UINT64)HttpsCaCertsSize));
> +
> +FreeHttpsCaCerts:
> +  FreePool (HttpsCaCerts);
> +}
> +
> +RETURN_STATUS
> +EFIAPI
> +TlsAuthConfigInit (
> +  VOID
> +  )
> +{
> +  SetCaCerts ();
> +
> +  return RETURN_SUCCESS;
> +}
> --
> 2.14.1.3.gb7cf6e02401b
>