[PATCH v2 1/9] OvmfPkg/TlsAuthConfigLib: configure trusted cipher suites for HTTPS boot

[Laszlo Ersek <lersek@redhat.com>]

Read the list of trusted cipher suites from fw_cfg and to store it to
EFI_TLS_CA_CERTIFICATE_VARIABLE.

The fw_cfg file is formatted by the "update-crypto-policies" utility 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
forwarded by NetworkPkg/HttpDxe (in TlsConfigCipherList()) to
NetworkPkg/TlsDxe (TlsSetSessionData()) and TlsLib (TlsSetCipherList()).

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>
---

Notes:
    v2:
    - no change

 OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.inf |  3 +-
 OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.c   | 98 ++++++++++++++++++++
 2 files changed, 100 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.inf b/OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.inf
index 5f83582a8313..40754ea5a2f3 100644
--- a/OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.inf
+++ b/OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.inf
@@ -46,10 +46,11 @@ [LibraryClasses]
   DebugLib
   MemoryAllocationLib
   QemuFwCfgLib
   UefiRuntimeServicesTableLib
 
 [Guids]
-  gEfiTlsCaCertificateGuid ## PRODUCES ## Variable:L"TlsCaCertificate"
+  gEdkiiHttpTlsCipherListGuid ## PRODUCES ## Variable:L"HttpTlsCipherList"
+  gEfiTlsCaCertificateGuid    ## PRODUCES ## Variable:L"TlsCaCertificate"
 
 [Depex]
   gEfiVariableWriteArchProtocolGuid
diff --git a/OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.c b/OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.c
index b5b33bc4fc69..74c393e5462f 100644
--- a/OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.c
+++ b/OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.c
@@ -17,12 +17,13 @@
 
 **/
 
 #include <Uefi/UefiBaseType.h>
 #include <Uefi/UefiSpec.h>
 
+#include <Guid/HttpTlsCipherList.h>
 #include <Guid/TlsAuthentication.h>
 
 #include <Library/BaseLib.h>
 #include <Library/DebugLib.h>
 #include <Library/MemoryAllocationLib.h>
 #include <Library/QemuFwCfgLib.h>
@@ -118,16 +119,113 @@ SetCaCerts (
     gEfiCallerBaseName, __FUNCTION__, (UINT64)HttpsCaCertsSize));
 
 FreeHttpsCaCerts:
   FreePool (HttpsCaCerts);
 }
 
+/**
+  Read the list of trusted cipher suites from the fw_cfg file
+  "etc/edk2/https/ciphers", and store it to
+  gEdkiiHttpTlsCipherListGuid:EDKII_HTTP_TLS_CIPHER_LIST_VARIABLE.
+
+  The contents are propagated by NetworkPkg/HttpDxe to NetworkPkg/TlsDxe; the
+  list is processed by the latter.
+**/
+STATIC
+VOID
+SetCipherSuites (
+  VOID
+  )
+{
+  EFI_STATUS           Status;
+  FIRMWARE_CONFIG_ITEM HttpsCiphersItem;
+  UINTN                HttpsCiphersSize;
+  VOID                 *HttpsCiphers;
+
+  Status = QemuFwCfgFindFile ("etc/edk2/https/ciphers", &HttpsCiphersItem,
+             &HttpsCiphersSize);
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_VERBOSE, "%a:%a: not touching cipher suites\n",
+      gEfiCallerBaseName, __FUNCTION__));
+    return;
+  }
+  //
+  // From this point on, any failure is fatal. An ordered cipher preference
+  // list is available from QEMU, thus we cannot let the firmware attempt HTTPS
+  // boot with either pre-existent or non-existent preferences. An empty set of
+  // cipher suites does not fail HTTPS boot automatically; the default cipher
+  // suite preferences would take effect, and we must prevent that.
+  //
+  // Delete the current EDKII_HTTP_TLS_CIPHER_LIST_VARIABLE if it exists. If
+  // the variable exists with EFI_VARIABLE_NON_VOLATILE attribute, we cannot
+  // make it volatile without deleting it first.
+  //
+  Status = gRT->SetVariable (
+                  EDKII_HTTP_TLS_CIPHER_LIST_VARIABLE, // VariableName
+                  &gEdkiiHttpTlsCipherListGuid,        // VendorGuid
+                  0,                                   // Attributes
+                  0,                                   // DataSize
+                  NULL                                 // Data
+                  );
+  if (EFI_ERROR (Status) && (Status != EFI_NOT_FOUND)) {
+    DEBUG ((DEBUG_ERROR, "%a:%a: failed to delete %g:\"%s\"\n",
+      gEfiCallerBaseName, __FUNCTION__, &gEdkiiHttpTlsCipherListGuid,
+      EDKII_HTTP_TLS_CIPHER_LIST_VARIABLE));
+    goto Done;
+  }
+
+  if (HttpsCiphersSize == 0) {
+    DEBUG ((DEBUG_ERROR, "%a:%a: list of cipher suites must not be empty\n",
+      gEfiCallerBaseName, __FUNCTION__));
+    Status = EFI_INVALID_PARAMETER;
+    goto Done;
+  }
+
+  HttpsCiphers = AllocatePool (HttpsCiphersSize);
+  if (HttpsCiphers == NULL) {
+    DEBUG ((DEBUG_ERROR, "%a:%a: failed to allocate HttpsCiphers\n",
+      gEfiCallerBaseName, __FUNCTION__));
+    Status = EFI_OUT_OF_RESOURCES;
+    goto Done;
+  }
+
+  QemuFwCfgSelectItem (HttpsCiphersItem);
+  QemuFwCfgReadBytes (HttpsCiphersSize, HttpsCiphers);
+
+  Status = gRT->SetVariable (
+                  EDKII_HTTP_TLS_CIPHER_LIST_VARIABLE, // VariableName
+                  &gEdkiiHttpTlsCipherListGuid,        // VendorGuid
+                  EFI_VARIABLE_BOOTSERVICE_ACCESS,     // Attributes
+                  HttpsCiphersSize,                    // DataSize
+                  HttpsCiphers                         // Data
+                  );
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_ERROR, "%a:%a: failed to set %g:\"%s\"\n",
+      gEfiCallerBaseName, __FUNCTION__, &gEdkiiHttpTlsCipherListGuid,
+      EDKII_HTTP_TLS_CIPHER_LIST_VARIABLE));
+    goto FreeHttpsCiphers;
+  }
+
+  DEBUG ((DEBUG_VERBOSE, "%a:%a: stored list of cipher suites (%Lu byte(s))\n",
+    gEfiCallerBaseName, __FUNCTION__, (UINT64)HttpsCiphersSize));
+
+FreeHttpsCiphers:
+  FreePool (HttpsCiphers);
+
+Done:
+  if (EFI_ERROR (Status)) {
+    ASSERT_EFI_ERROR (Status);
+    CpuDeadLoop ();
+  }
+}
+
 RETURN_STATUS
 EFIAPI
 TlsAuthConfigInit (
   VOID
   )
 {
   SetCaCerts ();
+  SetCipherSuites ();
 
   return RETURN_SUCCESS;
 }
-- 
2.14.1.3.gb7cf6e02401b