Re: [PATCH v3 4/5] efi: call get_event_log before ExitBootServices

["Marc-André Lureau" <marcandre.lureau@gmail.com>]

Hi Thiebaud

On Wed, Sep 20, 2017 at 10:13 AM, Thiebaud Weksteen <tweek@google.com> wrote:
> With TPM 2.0 specification, the event logs may only be accessible by
> calling an EFI Boot Service. Modify the EFI stub to copy the log area to
> a new Linux-specific EFI configuration table so it remains accessible
> once booted.
>
> When calling this service, it is possible to specify the expected format
> of the logs: TPM 1.2 (SHA1) or TPM 2.0 ("Crypto Agile"). For now, only the
> first format is retrieved.
>

Do you have plans to add support for the crypto-agile format? I am
working on uefi/ovmf support, and I am wondering if it is at all
necessary to add support for the 1.2 format. What do you think? I can
eventually try to work on 2.0 format support.

Thanks

> Signed-off-by: Thiebaud Weksteen <tweek@google.com>
> ---
>  arch/x86/boot/compressed/eboot.c      |  1 +
>  drivers/firmware/efi/Makefile         |  2 +-
>  drivers/firmware/efi/efi.c            |  4 ++
>  drivers/firmware/efi/libstub/Makefile |  3 +-
>  drivers/firmware/efi/libstub/tpm.c    | 81 +++++++++++++++++++++++++++++++++++
>  drivers/firmware/efi/tpm.c            | 40 +++++++++++++++++
>  include/linux/efi.h                   | 46 ++++++++++++++++++++
>  7 files changed, 174 insertions(+), 3 deletions(-)
>  create mode 100644 drivers/firmware/efi/tpm.c
>
> diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
> index a1686f3dc295..ef6abe8b3788 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(sys_table);
>
>         setup_graphics(boot_params);
>
> diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
> index 0329d319d89a..2f074b5cde87 100644
> --- a/drivers/firmware/efi/Makefile
> +++ b/drivers/firmware/efi/Makefile
> @@ -10,7 +10,7 @@
>  KASAN_SANITIZE_runtime-wrappers.o      := n
>
>  obj-$(CONFIG_ACPI_BGRT)                += efi-bgrt.o
> -obj-$(CONFIG_EFI)                      += efi.o vars.o reboot.o memattr.o
> +obj-$(CONFIG_EFI)                      += efi.o vars.o reboot.o memattr.o tpm.o
>  obj-$(CONFIG_EFI)                      += capsule.o memmap.o
>  obj-$(CONFIG_EFI_VARS)                 += efivars.o
>  obj-$(CONFIG_EFI_ESRT)                 += esrt.o
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index f97f272e16ee..0308acfaaf76 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -52,6 +52,7 @@ struct efi __read_mostly efi = {
>         .properties_table       = EFI_INVALID_TABLE_ADDR,
>         .mem_attr_table         = EFI_INVALID_TABLE_ADDR,
>         .rng_seed               = EFI_INVALID_TABLE_ADDR,
> +       .tpm_log                = EFI_INVALID_TABLE_ADDR
>  };
>  EXPORT_SYMBOL(efi);
>
> @@ -444,6 +445,7 @@ static __initdata efi_config_table_type_t common_tables[] = {
>         {EFI_PROPERTIES_TABLE_GUID, "PROP", &efi.properties_table},
>         {EFI_MEMORY_ATTRIBUTES_TABLE_GUID, "MEMATTR", &efi.mem_attr_table},
>         {LINUX_EFI_RANDOM_SEED_TABLE_GUID, "RNG", &efi.rng_seed},
> +       {LINUX_EFI_TPM_EVENT_LOG_GUID, "TPMEventLog", &efi.tpm_log},
>         {NULL_GUID, NULL, NULL},
>  };
>
> @@ -532,6 +534,8 @@ int __init efi_config_parse_tables(void *config_tables, int count, int sz,
>         if (efi_enabled(EFI_MEMMAP))
>                 efi_memattr_init();
>
> +       efi_tpm_eventlog_init();
> +
>         /* Parse the EFI Properties table if it exists */
>         if (efi.properties_table != EFI_INVALID_TABLE_ADDR) {
>                 efi_properties_table_t *tbl;
> 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..da661bf8cb96 100644
> --- a/drivers/firmware/efi/libstub/tpm.c
> +++ b/drivers/firmware/efi/libstub/tpm.c
> @@ -4,15 +4,18 @@
>   * 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.
>   */
>  #include <linux/efi.h>
> +#include <linux/tpm_eventlog.h>
>  #include <asm/efi.h>
>
>  #include "efistub.h"
>
> +#ifdef 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 +59,81 @@ 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(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;
> +       unsigned long first_entry_addr, last_entry_addr;
> +       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;
> +       first_entry_addr = (unsigned long) log_location;
> +
> +       /*
> +        * We populate the EFI table even if the logs are empty.
> +        */
> +       if (!log_last_entry) {
> +               log_size = 0;
> +       } else {
> +               last_entry_addr = (unsigned long) log_last_entry;
> +               /*
> +                * 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 *) last_entry_addr)->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_LOADER_DATA,
> +                               sizeof(*log_tbl) + log_size,
> +                               (void **) &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 *) first_entry_addr, 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(efi_system_table_t *sys_table_arg)
> +{
> +       /* Only try to retrieve the logs in 1.2 format. */
> +       efi_retrieve_tpm2_eventlog_1_2(sys_table_arg);
> +}
> diff --git a/drivers/firmware/efi/tpm.c b/drivers/firmware/efi/tpm.c
> new file mode 100644
> index 000000000000..0cbeb3d46b18
> --- /dev/null
> +++ b/drivers/firmware/efi/tpm.c
> @@ -0,0 +1,40 @@
> +/*
> + * Copyright (C) 2017 Google, Inc.
> + *     Thiebaud Weksteen <tweek@google.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/efi.h>
> +#include <linux/init.h>
> +#include <linux/memblock.h>
> +
> +#include <asm/early_ioremap.h>
> +
> +/*
> + * Reserve the memory associated with the TPM Event Log configuration table.
> + */
> +int __init efi_tpm_eventlog_init(void)
> +{
> +       struct linux_efi_tpm_eventlog *log_tbl;
> +       unsigned int tbl_size;
> +
> +       if (efi.tpm_log == EFI_INVALID_TABLE_ADDR)
> +               return 0;
> +
> +       log_tbl = early_memremap(efi.tpm_log, sizeof(*log_tbl));
> +       if (!log_tbl) {
> +               pr_err("Failed to map TPM Event Log table @ 0x%lx\n",
> +                       efi.tpm_log);
> +               efi.tpm_log = EFI_INVALID_TABLE_ADDR;
> +               return -ENOMEM;
> +       }
> +
> +       tbl_size = sizeof(*log_tbl) + log_tbl->size;
> +       memblock_reserve(efi.tpm_log, tbl_size);
> +       early_memunmap(log_tbl, sizeof(*log_tbl));
> +       return 0;
> +}
> +
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index 8dc3d94a3e3c..c5805eb601b1 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -472,6 +472,39 @@ 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;
> +
> +typedef u32 efi_tcg2_event_log_format;
> +
> +typedef struct {
> +       void *get_capability;
> +       efi_status_t (*get_event_log)(efi_handle_t, efi_tcg2_event_log_format,
> +               efi_physical_addr_t *, efi_physical_addr_t *, efi_bool_t *);
> +       void *hash_log_extend_event;
> +       void *submit_command;
> +       void *get_active_pcr_banks;
> +       void *set_active_pcr_banks;
> +       void *get_result_of_set_active_pcr_banks;
> +} efi_tcg2_protocol_t;
> +
>  /*
>   * Types and defines for EFI ResetSystem
>   */
> @@ -622,6 +655,7 @@ 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 +668,7 @@ 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;
> @@ -908,6 +943,7 @@ extern struct efi {
>         unsigned long properties_table; /* properties table */
>         unsigned long mem_attr_table;   /* memory attributes table */
>         unsigned long rng_seed;         /* UEFI firmware random seed */
> +       unsigned long tpm_log;          /* TPM2 Event Log table */
>         efi_get_time_t *get_time;
>         efi_set_time_t *set_time;
>         efi_get_wakeup_time_t *get_wakeup_time;
> @@ -1504,6 +1540,8 @@ static inline void
>  efi_enable_reset_attack_mitigation(efi_system_table_t *sys_table_arg) { }
>  #endif
>
> +void efi_retrieve_tpm2_eventlog(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 +1609,12 @@ struct linux_efi_random_seed {
>         u8      bits[];
>  };
>
> +struct linux_efi_tpm_eventlog {
> +       u32     size;
> +       u8      version;
> +       u8      log[];
> +};
> +
> +extern int efi_tpm_eventlog_init(void);
> +
>  #endif /* _LINUX_EFI_H */
> --
> 2.14.1.821.g8fa685d3b7-goog
>



-- 
Marc-André Lureau