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

Ard Biesheuvel
2017-09-06T14:54:51Z

On 6 September 2017 at 15:53, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> Hi Thiebaud,
>
> On 6 September 2017 at 15:25, Thiebaud Weksteen <tweek@google.com> wrote:
>> 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(-)
>>
>
> Why is this x86 only?
>
>
>> 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
>>
>
> Did you build test on ARM/arm64 as well?
>
>> # 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"
>>

Oh, and please don't use includes like this. If there are data
structures that are not local to drivers/char, put them in a .h file
by themselves under include/linux somewhere.

>> +#if IS_ENABLED(CONFIG_RESET_ATTACK_MITIGATION)
>
> IS_ENABLED() is intended for C style if()s rather than preprocessor
> conditionals. Please replace with #ifdef
>
>> 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,
>
> Does this function actually use struct 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);
>
> Please indent appropriately.
>
>> + 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
>
> I am not a native English speaker, but 'to surface' sounds a bit awkward here.
>
>> + * 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,
>
> Why is this runtime services data? You are passing your own data
> across the UEFI / kernel handover, and so if you parse your config
> table early enough, you can just reserve this memory.
>
> Runtime services data will be given a virtual mapping by the firmware
> so it is accessible to the firmware itself during runtime services
> invocations, and on ARM/arm64, we actually have to omit if from the
> ordinary direct mapping of memory, which may lead to page table
> fragmentation and increased TLB pressure.
>
> In summary, don't use it as a convenience so you don'y have to think
> about when/how to reserve it from normal allocation by the kernel.
>
>> + 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);
>
> Indentation please.
>
>> + 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
>>
>> --
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