ibmvtpm: Add support for trusted boot using a vTPM 2.0

Add support for trusted boot using a vTPM 2.0 on the IBM IEEE1275
PowerPC platform. With this patch grub now measures text and binary data
into the TPM's PCRs 8 and 9 in the same way as the x86_64 platform
does.

This patch requires Daniel Axtens's patches for claiming more memory.

Note: The tpm_init() function cannot be called from GRUB_MOD_INIT() since
it does not find the device nodes upon module initialization and
therefore the call to tpm_init() must be deferred to grub_tpm_measure().

For vTPM support to work on PowerVM, system driver levels 1010.30
or 1020.00 are required.

Note: Previous versions of firmware levels with the 2hash-ext-log
API call have a bug that, once this API call is invoked, has the
effect of disabling the vTPM driver under Linux causing an error
message to be displayed in the Linux kernel log. Those users will
have to update their machines to the firmware levels mentioned
above.

Cc: Eric Snowberg <[email protected]>
Signed-off-by: Stefan Berger <[email protected]>
Signed-off-by: Daniel Axtens <[email protected]>
Reviewed-by: Daniel Kiper <[email protected]>
(cherry picked from commit 2aa5ef83743dfea79377309ff4f5e9c9a55de355)

docs/grub.texi

@@ -6221,7 +6221,8 @@ tpm module is loaded. As such it is recommended that the tpm module be built
 into @file{core.img} in order to avoid a potential gap in measurement between
 @file{core.img} being loaded and the tpm module being loaded.
 
-Measured boot is currently only supported on EFI platforms.
+Measured boot is currently only supported on EFI and IBM IEEE1275 PowerPC
+platforms.
 
 @node Lockdown
 @section Lockdown when booting on a secure setup

grub-core/Makefile.core.def

@@ -1172,6 +1172,13 @@ module = {
   enable = powerpc_ieee1275;
 };
 
+module = {
+  name = tpm;
+  common = commands/tpm.c;
+  ieee1275 = commands/ieee1275/ibmvtpm.c;
+  enable = powerpc_ieee1275;
+};
+
 module = {
   name = terminal;
   common = commands/terminal.c;

grub-core/commands/ieee1275/ibmvtpm.c

@@ -0,0 +1,155 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2022  Free Software Foundation, Inc.
+ *  Copyright (C) 2022  IBM Corporation
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *  IBM vTPM support code.
+ */
+
+#include <grub/err.h>
+#include <grub/types.h>
+#include <grub/tpm.h>
+#include <grub/ieee1275/ieee1275.h>
+#include <grub/mm.h>
+#include <grub/misc.h>
+
+static grub_ieee1275_ihandle_t tpm_ihandle;
+static grub_uint8_t tpm_version;
+
+#define IEEE1275_IHANDLE_INVALID ((grub_ieee1275_ihandle_t) 0)
+
+static void
+tpm_get_tpm_version (void)
+{
+  grub_ieee1275_phandle_t vtpm;
+  char buffer[20];
+
+  if (!grub_ieee1275_finddevice ("/vdevice/vtpm", &vtpm) &&
+      !grub_ieee1275_get_property (vtpm, "compatible", buffer,
+				   sizeof (buffer), NULL) &&
+      !grub_strcmp (buffer, "IBM,vtpm20"))
+    tpm_version = 2;
+}
+
+static grub_err_t
+tpm_init (void)
+{
+  static int init_success = 0;
+
+  if (!init_success)
+    {
+      if (grub_ieee1275_open ("/vdevice/vtpm", &tpm_ihandle) < 0)
+	{
+	  tpm_ihandle = IEEE1275_IHANDLE_INVALID;
+	  return GRUB_ERR_UNKNOWN_DEVICE;
+	}
+
+      init_success = 1;
+
+      tpm_get_tpm_version ();
+    }
+
+  return GRUB_ERR_NONE;
+}
+
+static int
+ibmvtpm_2hash_ext_log (grub_uint8_t pcrindex,
+		       grub_uint32_t eventtype,
+		       const char *description,
+		       grub_size_t description_size,
+		       void *buf, grub_size_t size)
+{
+  struct tpm_2hash_ext_log
+  {
+    struct grub_ieee1275_common_hdr common;
+    grub_ieee1275_cell_t method;
+    grub_ieee1275_cell_t ihandle;
+    grub_ieee1275_cell_t size;
+    grub_ieee1275_cell_t buf;
+    grub_ieee1275_cell_t description_size;
+    grub_ieee1275_cell_t description;
+    grub_ieee1275_cell_t eventtype;
+    grub_ieee1275_cell_t pcrindex;
+    grub_ieee1275_cell_t catch_result;
+    grub_ieee1275_cell_t rc;
+  };
+  struct tpm_2hash_ext_log args;
+
+  INIT_IEEE1275_COMMON (&args.common, "call-method", 8, 2);
+  args.method = (grub_ieee1275_cell_t) "2hash-ext-log";
+  args.ihandle = tpm_ihandle;
+  args.pcrindex = pcrindex;
+  args.eventtype = eventtype;
+  args.description = (grub_ieee1275_cell_t) description;
+  args.description_size = description_size;
+  args.buf = (grub_ieee1275_cell_t) buf;
+  args.size = (grub_ieee1275_cell_t) size;
+
+  if (IEEE1275_CALL_ENTRY_FN (&args) == -1)
+    return -1;
+
+  /*
+   * catch_result is set if firmware does not support 2hash-ext-log
+   * rc is GRUB_IEEE1275_CELL_FALSE (0) on failure
+   */
+  if ((args.catch_result) || args.rc == GRUB_IEEE1275_CELL_FALSE)
+    return -1;
+
+  return 0;
+}
+
+static grub_err_t
+tpm2_log_event (unsigned char *buf, grub_size_t size, grub_uint8_t pcr,
+		const char *description)
+{
+  static int error_displayed = 0;
+  int rc;
+
+  rc = ibmvtpm_2hash_ext_log (pcr, EV_IPL,
+			      description, grub_strlen(description) + 1,
+			      buf, size);
+  if (rc && !error_displayed)
+    {
+      error_displayed++;
+      return grub_error (GRUB_ERR_BAD_DEVICE,
+			 "2HASH-EXT-LOG failed: Firmware is likely too old.\n");
+    }
+
+  return GRUB_ERR_NONE;
+}
+
+grub_err_t
+grub_tpm_measure (unsigned char *buf, grub_size_t size, grub_uint8_t pcr,
+		  const char *description)
+{
+  /*
+   * Call tpm_init() 'late' rather than from GRUB_MOD_INIT() so that device nodes
+   * can be found.
+   */
+  grub_err_t err = tpm_init ();
+
+  /* Absence of a TPM isn't a failure. */
+  if (err != GRUB_ERR_NONE)
+    return GRUB_ERR_NONE;
+
+  grub_dprintf ("tpm", "log_event, pcr = %d, size = 0x%" PRIxGRUB_SIZE ", %s\n",
+		pcr, size, description);
+
+  if (tpm_version == 2)
+    return tpm2_log_event (buf, size, pcr, description);
+
+  return GRUB_ERR_NONE;
+}

include/grub/ieee1275/ieee1275.h

@@ -24,6 +24,9 @@
 #include <grub/types.h>
 #include <grub/machine/ieee1275.h>
 
+#define GRUB_IEEE1275_CELL_FALSE       ((grub_ieee1275_cell_t) 0)
+#define GRUB_IEEE1275_CELL_TRUE        ((grub_ieee1275_cell_t) -1)
+
 struct grub_ieee1275_mem_region
 {
   unsigned int start;