[PATCH v2 4/4] ibmvtpm: Add support for trusted boot using a vTPM 2.0

[Stefan Berger]

From: Stefan Berger <stefanb@linux.ibm.com>

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.

Cc: Eric Snowberg <eric.snowberg@oracle.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 docs/grub.texi                        |   3 +-
 grub-core/Makefile.core.def           |   7 ++
 grub-core/commands/ieee1275/ibmvtpm.c | 169 ++++++++++++++++++++++++++
 3 files changed, 178 insertions(+), 1 deletion(-)
 create mode 100644 grub-core/commands/ieee1275/ibmvtpm.c

diff --git a/docs/grub.texi b/docs/grub.texi
index f8b4b3b21..23d2f2d90 100644
--- a/docs/grub.texi
+++ b/docs/grub.texi
@@ -6023,7 +6023,8 @@ 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
diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def
index 8022e1c0a..e6ac50704 100644
--- a/grub-core/Makefile.core.def
+++ b/grub-core/Makefile.core.def
@@ -1118,6 +1118,13 @@ 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;
diff --git a/grub-core/commands/ieee1275/ibmvtpm.c 
b/grub-core/commands/ieee1275/ibmvtpm.c
new file mode 100644
index 000000000..d61cb111a
--- /dev/null
+++ b/grub-core/commands/ieee1275/ibmvtpm.c
@@ -0,0 +1,169 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2021  Free Software Foundation, Inc.
+ *  Copyright (C) 2021  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>
+
+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;
+};
+
+#define IEEE1275_CELL_TRUE     ((grub_ieee1275_cell_t) -1)
+
+static grub_ieee1275_ihandle_t tpm_ihandle;
+static grub_uint8_t tpm_version;
+
+static grub_ieee1275_ihandle_t
+tpm_init (void)
+{
+  static int init_called = 0;
+
+  if (!init_called)
+    {
+      init_called = 1;
+      grub_ieee1275_open ("/vdevice/vtpm", &tpm_ihandle);
+    }
+
+  return tpm_ihandle;
+}
+
+static void
+tpm_get_tpm_version (void)
+{
+  static int version_probed = 0;
+  grub_ieee1275_phandle_t vtpm;
+  char buffer[20];
+  grub_ssize_t buffer_size;
+
+  if (!version_probed)
+    {
+      version_probed = 1;
+      if (!grub_ieee1275_finddevice ("/vdevice/vtpm", &vtpm) &&
+         !grub_ieee1275_get_property (vtpm, "compatible", buffer,
+                                      sizeof buffer, &buffer_size) &&
+         !grub_strcmp (buffer, "IBM,vtpm20"))
+       {
+         tpm_version = 2;
+       }
+    }
+}
+
+static grub_err_t
+tpm_handle_find (grub_ieee1275_ihandle_t *tpm_handle)
+{
+  *tpm_handle = tpm_init ();
+  if (*tpm_handle == 0)
+      return GRUB_ERR_UNKNOWN_DEVICE;
+
+  tpm_get_tpm_version ();
+
+  return GRUB_ERR_NONE;
+}
+
+static int
+ibmvtpm_2hash_ext_log (grub_uint32_t ihandle,
+                      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 args;
+
+  INIT_IEEE1275_COMMON (&args.common, "call-method", 8, 2);
+  args.method = (grub_ieee1275_cell_t) "2hash-ext-log";
+  args.ihandle = 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 TRUE (-1) on success
+   */
+  if ((args.catch_result) || args.rc != IEEE1275_CELL_TRUE)
+      return -1;
+
+  return 0;
+}
+
+static grub_err_t
+tpm2_log_event (grub_ieee1275_ihandle_t tpm_handle, unsigned char *buf,
+                    grub_size_t size, grub_uint8_t pcr,
+                    const char *description)
+{
+  static int error_displayed;
+  int err;
+
+  err = ibmvtpm_2hash_ext_log (tpm_handle,
+                              pcr, EV_IPL,
+                              description,
+                              grub_strlen(description) + 1,
+                              buf, size);
+  if (err && error_displayed < 1)
+    {
+      error_displayed++;
+      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)
+{
+  grub_ieee1275_ihandle_t tpm_handle;
+
+  /* Absence of a TPM isn't a failure. */
+  if (tpm_handle_find (&tpm_handle) != 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 (tpm_handle, buf, size, pcr, description);
+
+  return GRUB_ERR_NONE;
+}
-- 
2.25.1