[PATCH] 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. Make grub_tpm_is_fail_fatal() global and move its body to
efi/tpm.c. Check environment variable tpm_fail_fatal to fallback to
previous behaviour.

Signed-off-by: Michał Grzelak <mchl.grzlk@gmail.com>
---
 grub-core/commands/efi/tpm.c | 10 +++++++++-
 grub-core/commands/tpm.c     | 11 ++---------
 include/grub/tpm.h           |  1 +
 3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/grub-core/commands/efi/tpm.c b/grub-core/commands/efi/tpm.c
index c616768f9..05f3064f7 100644
--- a/grub-core/commands/efi/tpm.c
+++ b/grub-core/commands/efi/tpm.c
@@ -18,6 +18,7 @@
  *  EFI TPM support code.
  */
 
+#include <grub/env.h>
 #include <grub/err.h>
 #include <grub/i18n.h>
 #include <grub/efi/api.h>
@@ -146,7 +147,8 @@ 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 (grub_tpm_is_fail_fatal () ? GRUB_ERR_UNKNOWN_DEVICE
+                         : GRUB_ERR_NONE, N_("unknown TPM error"));
     }
 }
 
@@ -266,6 +268,12 @@ grub_cc_log_event (unsigned char *buf, grub_size_t size, 
grub_uint8_t pcr,
     grub_efi_log_event_status (status);
 }
 
+bool
+grub_tpm_is_fail_fatal (void)
+{
+  return grub_env_get_bool ("tpm_fail_fatal", false);
+}
+
 grub_err_t
 grub_tpm_measure (unsigned char *buf, grub_size_t size, grub_uint8_t pcr,
                    const char *description)
diff --git a/grub-core/commands/tpm.c b/grub-core/commands/tpm.c
index 9f830916d..f86bdc81e 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)
 {
@@ -55,7 +48,7 @@ grub_tpm_verify_write (void *context, void *buf, grub_size_t 
size)
     return GRUB_ERR_NONE;
 
   grub_dprintf ("tpm", "Measuring buffer failed: %d\n", status);
-  return is_tpm_fail_fatal () ? status : GRUB_ERR_NONE;
+  return grub_tpm_is_fail_fatal () ? status : GRUB_ERR_NONE;
 }
 
 static grub_err_t
@@ -91,7 +84,7 @@ grub_tpm_verify_string (char *str, enum 
grub_verify_string_type type)
     return GRUB_ERR_NONE;
 
   grub_dprintf ("tpm", "Measuring string %s failed: %d\n", str, status);
-  return is_tpm_fail_fatal () ? status : GRUB_ERR_NONE;
+  return grub_tpm_is_fail_fatal () ? status : GRUB_ERR_NONE;
 }
 
 struct grub_file_verifier grub_tpm_verifier = {
diff --git a/include/grub/tpm.h b/include/grub/tpm.h
index c19fcbd0a..aea145dd1 100644
--- a/include/grub/tpm.h
+++ b/include/grub/tpm.h
@@ -36,5 +36,6 @@
 
 grub_err_t grub_tpm_measure (unsigned char *buf, grub_size_t size,
                             grub_uint8_t pcr, const char *description);
+bool grub_tpm_is_fail_fatal (void);
 int grub_tpm_present (void);
 #endif
-- 
2.37.3