[PATCH 1/2] efi: call get_event_log before ExitBootServices

Thiebaud Weksteen
2017-09-06T14:26:00Z

With TPM 2.0, access to the event log is only possible by using the
EFI TPM2 Boot Service. Modify the EFI stub to copy the log area to a new
Linux-specific EFI table so it remains accessible for future use.

Signed-off-by: Thiebaud Weksteen <tweek@google.com>
---
arch/x86/boot/compressed/eboot.c | 1 +
drivers/char/tpm/tpm.h | 29 ++++++++++---
drivers/char/tpm/tpm_eventlog.h | 26 +++---------
drivers/firmware/efi/libstub/Makefile | 3 +-
drivers/firmware/efi/libstub/tpm.c | 80 +++++++++++++++++++++++++++++++++++
include/linux/efi.h | 35 +++++++++++++++
6 files changed, 146 insertions(+), 28 deletions(-)

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index a1686f3dc295..97bec8df36ff 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -999,6 +999,7 @@ struct boot_params *efi_main(struct efi_config *c,

/* Ask the firmware to clear memory on unclean shutdown */
efi_enable_reset_attack_mitigation(sys_table);
+ efi_retrieve_tpm2_eventlog(boot_params, sys_table);

setup_graphics(boot_params);

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 04fbff2edbf3..efede7dc9340 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -40,6 +40,8 @@
#include <asm/intel-family.h>
#endif

+#include "tpm_eventlog.h"
+
enum tpm_const {
TPM_MINOR = 224, /* officially assigned */
TPM_BUFSIZE = 4096,
@@ -397,11 +399,6 @@ struct tpm_cmd_t {
tpm_cmd_params params;
} __packed;

-struct tpm2_digest {
- u16 alg_id;
- u8 digest[SHA512_DIGEST_SIZE];
-} __packed;
-
/* A string buffer type for constructing TPM commands. This is based on the
* ideas of string buffer code in security/keys/trusted.h but is heap based
* in order to keep the stack usage minimal.
@@ -581,4 +578,26 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u32 cc,
u8 *cmd);
int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space,
u32 cc, u8 *buf, size_t *bufsiz);
+
+extern const struct seq_operations tpm2_binary_b_measurements_seqops;
+
+#if defined(CONFIG_ACPI)
+int tpm_read_log_acpi(struct tpm_chip *chip);
+#else
+static inline int tpm_read_log_acpi(struct tpm_chip *chip)
+{
+ return -ENODEV;
+}
+#endif
+#if defined(CONFIG_OF)
+int tpm_read_log_of(struct tpm_chip *chip);
+#else
+static inline int tpm_read_log_of(struct tpm_chip *chip)
+{
+ return -ENODEV;
+}
+#endif
+
+int tpm_bios_log_setup(struct tpm_chip *chip);
+void tpm_bios_log_teardown(struct tpm_chip *chip);
#endif
diff --git a/drivers/char/tpm/tpm_eventlog.h b/drivers/char/tpm/tpm_eventlog.h
index b4b549559203..1009a2503985 100644
--- a/drivers/char/tpm/tpm_eventlog.h
+++ b/drivers/char/tpm/tpm_eventlog.h
@@ -104,6 +104,11 @@ struct tcg_event_field {
u8 event[0];
} __packed;

+struct tpm2_digest {
+ u16 alg_id;
+ u8 digest[SHA512_DIGEST_SIZE];
+} __packed;
+
struct tcg_pcr_event2 {
u32 pcr_idx;
u32 event_type;
@@ -112,26 +117,5 @@ struct tcg_pcr_event2 {
struct tcg_event_field event;
} __packed;

-extern const struct seq_operations tpm2_binary_b_measurements_seqops;
-
-#if defined(CONFIG_ACPI)
-int tpm_read_log_acpi(struct tpm_chip *chip);
-#else
-static inline int tpm_read_log_acpi(struct tpm_chip *chip)
-{
- return -ENODEV;
-}
-#endif
-#if defined(CONFIG_OF)
-int tpm_read_log_of(struct tpm_chip *chip);
-#else
-static inline int tpm_read_log_of(struct tpm_chip *chip)
-{
- return -ENODEV;
-}
-#endif
-
-int tpm_bios_log_setup(struct tpm_chip *chip);
-void tpm_bios_log_teardown(struct tpm_chip *chip);

#endif
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index dedf9bde44db..2abe6d22dc5f 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -29,8 +29,7 @@ OBJECT_FILES_NON_STANDARD := y
# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
KCOV_INSTRUMENT := n

-lib-y := efi-stub-helper.o gop.o secureboot.o
-lib-$(CONFIG_RESET_ATTACK_MITIGATION) += tpm.o
+lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o

# include the stub's generic dependencies from lib/ when building for ARM/arm64
arm-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c sort.c
diff --git a/drivers/firmware/efi/libstub/tpm.c b/drivers/firmware/efi/libstub/tpm.c
index 6224cdbc9669..ba2cb68833fb 100644
--- a/drivers/firmware/efi/libstub/tpm.c
+++ b/drivers/firmware/efi/libstub/tpm.c
@@ -4,6 +4,7 @@
* Copyright (C) 2016 CoreOS, Inc
* Copyright (C) 2017 Google, Inc.
* Matthew Garrett <mjg59@google.com>
+ * Thiebaud Weksteen <tweek@google.com>
*
* This file is part of the Linux kernel, and is made available under the
* terms of the GNU General Public License version 2.
@@ -12,7 +13,9 @@
#include <asm/efi.h>

#include "efistub.h"
+#include "../../../char/tpm/tpm_eventlog.h"

+#if IS_ENABLED(CONFIG_RESET_ATTACK_MITIGATION)
static const efi_char16_t efi_MemoryOverWriteRequest_name[] = {
'M', 'e', 'm', 'o', 'r', 'y', 'O', 'v', 'e', 'r', 'w', 'r', 'i', 't',
'e', 'R', 'e', 'q', 'u', 'e', 's', 't', 'C', 'o', 'n', 't', 'r', 'o',
@@ -56,3 +59,80 @@ void efi_enable_reset_attack_mitigation(efi_system_table_t *sys_table_arg)
EFI_VARIABLE_BOOTSERVICE_ACCESS |
EFI_VARIABLE_RUNTIME_ACCESS, sizeof(val), &val);
}
+
+#endif
+
+void efi_retrieve_tpm2_eventlog_1_2(struct boot_params *boot_params,
+ efi_system_table_t *sys_table_arg)
+{
+ efi_guid_t tcg2_guid = EFI_TCG2_PROTOCOL_GUID;
+ efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID;
+ efi_status_t status;
+ efi_physical_addr_t log_location, log_last_entry;
+ struct linux_efi_tpm_eventlog *log_tbl;
+ size_t log_size, last_entry_size;
+ efi_bool_t truncated;
+ void *tcg2_protocol;
+
+ status = efi_call_early(locate_protocol, &tcg2_guid, NULL,
+ &tcg2_protocol);
+ if (status != EFI_SUCCESS)
+ return;
+
+ status = efi_call_proto(efi_tcg2_protocol, get_event_log, tcg2_protocol,
+ EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2,
+ &log_location, &log_last_entry, &truncated);
+ if (status != EFI_SUCCESS)
+ return;
+
+ if (!log_location)
+ return;
+
+ /*
+ * If the logs are empty, we still populate the EFI table to surface
+ * this information to userland.
+ */
+ if (!log_last_entry) {
+ log_size = 0;
+ } else {
+ /*
+ * get_event_log only returns the address of the last entry.
+ * We need to calculate its size to deduce the full size of
+ * the logs.
+ */
+ last_entry_size = sizeof(struct tcpa_event) +
+ ((struct tcpa_event *)log_last_entry)->event_size;
+ log_size = log_last_entry - log_location + last_entry_size;
+ }
+
+ /* Allocate space for the logs and copy them. */
+ status = efi_call_early(allocate_pool, EFI_RUNTIME_SERVICES_DATA,
+ sizeof(*log_tbl) + log_size, &log_tbl);
+
+ if (status != EFI_SUCCESS) {
+ efi_printk(sys_table_arg,
+ "Unable to allocate memory for event log\n");
+ return;
+ }
+
+ memset(log_tbl, 0, sizeof(*log_tbl) + log_size);
+ log_tbl->size = log_size;
+ log_tbl->version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2;
+ memcpy(log_tbl->log, (void *)log_location, log_size);
+
+ status = efi_call_early(install_configuration_table,
+ &linux_eventlog_guid, log_tbl);
+ if (status != EFI_SUCCESS)
+ goto err_free;
+ return;
+
+err_free:
+ efi_call_early(free_pool, log_tbl);
+}
+
+void efi_retrieve_tpm2_eventlog(struct boot_params *boot_params,
+ efi_system_table_t *sys_table_arg)
+{
+ /* Only try to retrieve the logs in 1.2 format. */
+ efi_retrieve_tpm2_eventlog_1_2(boot_params, sys_table_arg);
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 8dc3d94a3e3c..5eaaa68ac58a 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -472,6 +472,26 @@ typedef struct {
u64 get_all;
} apple_properties_protocol_64_t;

+typedef struct {
+ u32 get_capability;
+ u32 get_event_log;
+ u32 hash_log_extend_event;
+ u32 submit_command;
+ u32 get_active_pcr_banks;
+ u32 set_active_pcr_banks;
+ u32 get_result_of_set_active_pcr_banks;
+} efi_tcg2_protocol_32_t;
+
+typedef struct {
+ u64 get_capability;
+ u64 get_event_log;
+ u64 hash_log_extend_event;
+ u64 submit_command;
+ u64 get_active_pcr_banks;
+ u64 set_active_pcr_banks;
+ u64 get_result_of_set_active_pcr_banks;
+} efi_tcg2_protocol_64_t;
+
/*
* Types and defines for EFI ResetSystem
*/
@@ -622,6 +642,7 @@ void efi_native_runtime_setup(void);
#define EFI_MEMORY_ATTRIBUTES_TABLE_GUID EFI_GUID(0xdcfa911d, 0x26eb, 0x469f, 0xa2, 0x20, 0x38, 0xb7, 0xdc, 0x46, 0x12, 0x20)
#define EFI_CONSOLE_OUT_DEVICE_GUID EFI_GUID(0xd3b36f2c, 0xd551, 0x11d4, 0x9a, 0x46, 0x00, 0x90, 0x27, 0x3f, 0xc1, 0x4d)
#define APPLE_PROPERTIES_PROTOCOL_GUID EFI_GUID(0x91bd12fe, 0xf6c3, 0x44fb, 0xa5, 0xb7, 0x51, 0x22, 0xab, 0x30, 0x3a, 0xe0)
+#define EFI_TCG2_PROTOCOL_GUID EFI_GUID(0x607f766c, 0x7455, 0x42be, 0x93, 0x0b, 0xe4, 0xd7, 0x6d, 0xb2, 0x72, 0x0f)

#define EFI_IMAGE_SECURITY_DATABASE_GUID EFI_GUID(0xd719b2cb, 0x3d3a, 0x4596, 0xa3, 0xbc, 0xda, 0xd0, 0x0e, 0x67, 0x65, 0x6f)
#define EFI_SHIM_LOCK_GUID EFI_GUID(0x605dab50, 0xe046, 0x4300, 0xab, 0xb6, 0x3d, 0xd8, 0x10, 0xdd, 0x8b, 0x23)
@@ -634,6 +655,7 @@ void efi_native_runtime_setup(void);
#define LINUX_EFI_ARM_SCREEN_INFO_TABLE_GUID EFI_GUID(0xe03fc20a, 0x85dc, 0x406e, 0xb9, 0x0e, 0x4a, 0xb5, 0x02, 0x37, 0x1d, 0x95)
#define LINUX_EFI_LOADER_ENTRY_GUID EFI_GUID(0x4a67b082, 0x0a4c, 0x41cf, 0xb6, 0xc7, 0x44, 0x0b, 0x29, 0xbb, 0x8c, 0x4f)
#define LINUX_EFI_RANDOM_SEED_TABLE_GUID EFI_GUID(0x1ce1e5bc, 0x7ceb, 0x42f2, 0x81, 0xe5, 0x8a, 0xad, 0xf1, 0x80, 0xf5, 0x7b)
+#define LINUX_EFI_TPM_EVENT_LOG_GUID EFI_GUID(0xb7799cb0, 0xeca2, 0x4943, 0x96, 0x67, 0x1f, 0xae, 0x07, 0xb7, 0x47, 0xfa)

typedef struct {
efi_guid_t guid;
@@ -1504,6 +1526,9 @@ static inline void
efi_enable_reset_attack_mitigation(efi_system_table_t *sys_table_arg) { }
#endif

+void efi_retrieve_tpm2_eventlog(struct boot_params *boot_params,
+ efi_system_table_t *sys_table);
+
/*
* Arch code can implement the following three template macros, avoiding
* reptition for the void/non-void return cases of {__,}efi_call_virt():
@@ -1571,4 +1596,14 @@ struct linux_efi_random_seed {
u8 bits[];
};

+
+#define EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2 0x1
+#define EFI_TCG2_EVENT_LOG_FORMAT_TCG_2 0x2
+
+struct linux_efi_tpm_eventlog {
+ u32 size;
+ u8 version;
+ u8 log[];
+};
+
#endif /* _LINUX_EFI_H */
--
2.14.1.581.gf28d330327-goog