[PATCH v2 1/1] tpm: Enable boot despite unknown firmware failure

[Michał Grzelak]

Currently booting the system is prevented when call to EFI firmware
hash_log_extend_event() returns unknown error. Solve this by following
convention used in commit a4356538d (commands/tpm: Don't propagate
measurement failures to the verifiers layer).

Let the system to be bootable by default when unknown TPM error is
encountered. Check environment variable tpm_fail_fatal to fallback to
previous behaviour.

Signed-off-by: Michał Grzelak <mchl.grzlk@gmail.com>
---
 docs/grub.texi               | 5 +++++
 grub-core/commands/efi/tpm.c | 3 ++-
 grub-core/commands/tpm.c     | 7 -------
 include/grub/tpm.h           | 9 +++++++++
 4 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/docs/grub.texi b/docs/grub.texi
index 9b58886a9..fc4e08f2c 100644
--- a/docs/grub.texi
+++ b/docs/grub.texi
@@ -3841,6 +3841,11 @@ If this variable is set and true (i.e., not set to 
``0'', ``false'',
 fatal. Otherwise, they will merely be debug-logged and boot will
 continue.
 
+Call to EFI firmware, like hash_log_extend_event(), can return an unknown
+error, i.e. due to bug present in firmware. When this variable is set and
+true (same values as with TPM measurements) this situation will be considered
+to be fatal and error-logged as ``unknown TPM error''. If not set, booting
+the OS will be enabled.
 
 @node Environment block
 @section The GRUB environment block
diff --git a/grub-core/commands/efi/tpm.c b/grub-core/commands/efi/tpm.c
index c616768f9..508ae8b3a 100644
--- a/grub-core/commands/efi/tpm.c
+++ b/grub-core/commands/efi/tpm.c
@@ -146,7 +146,8 @@ grub_efi_log_event_status (grub_efi_status_t status)
     case GRUB_EFI_NOT_FOUND:
       return grub_error (GRUB_ERR_UNKNOWN_DEVICE, N_("TPM unavailable"));
     default:
-      return grub_error (GRUB_ERR_UNKNOWN_DEVICE, N_("unknown TPM error"));
+      return grub_error (is_tpm_fail_fatal () ? GRUB_ERR_UNKNOWN_DEVICE
+                         : GRUB_ERR_NONE, N_("unknown TPM error"));
     }
 }
 
diff --git a/grub-core/commands/tpm.c b/grub-core/commands/tpm.c
index 9f830916d..c7e599170 100644
--- a/grub-core/commands/tpm.c
+++ b/grub-core/commands/tpm.c
@@ -18,7 +18,6 @@
  *  Core TPM support code.
  */
 
-#include <grub/env.h>
 #include <grub/err.h>
 #include <grub/i18n.h>
 #include <grub/misc.h>
@@ -40,12 +39,6 @@ grub_tpm_verify_init (grub_file_t io,
   return GRUB_ERR_NONE;
 }
 
-static inline bool
-is_tpm_fail_fatal (void)
-{
-  return grub_env_get_bool ("tpm_fail_fatal", false);
-}
-
 static grub_err_t
 grub_tpm_verify_write (void *context, void *buf, grub_size_t size)
 {
diff --git a/include/grub/tpm.h b/include/grub/tpm.h
index c19fcbd0a..11238da18 100644
--- a/include/grub/tpm.h
+++ b/include/grub/tpm.h
@@ -19,6 +19,8 @@
 #ifndef GRUB_TPM_HEADER
 #define GRUB_TPM_HEADER 1
 
+#include <grub/env.h>
+
 #define GRUB_STRING_PCR 8
 #define GRUB_BINARY_PCR 9
 
@@ -37,4 +39,11 @@
 grub_err_t grub_tpm_measure (unsigned char *buf, grub_size_t size,
                             grub_uint8_t pcr, const char *description);
 int grub_tpm_present (void);
+
+static inline bool
+is_tpm_fail_fatal (void)
+{
+  return grub_env_get_bool ("tpm_fail_fatal", false);
+}
+
 #endif
-- 
2.37.3