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Message-ID: <CAKv+Gu8Wpjq90xVkRxSd2JhJxwk7z+SaGhsX=-LvVvDNBWMdNg@mail.gmail.com>
Date: Tue, 21 May 2019 10:29:47 +0100
From: Ard Biesheuvel <ard.biesheuvel@...aro.org>
To: Matthew Garrett <matthewgarrett@...gle.com>
Cc: linux-integrity <linux-integrity@...r.kernel.org>,
Peter Hüwe <peterhuewe@....de>,
Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
Jason Gunthorpe <jgg@...pe.ca>,
Roberto Sassu <roberto.sassu@...wei.com>,
linux-efi <linux-efi@...r.kernel.org>,
linux-security-module <linux-security-module@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Thiebaud Weksteen <tweek@...gle.com>,
Bartosz Szczepanek <bsz@...ihalf.com>,
Matthew Garrett <mjg59@...gle.com>
Subject: Re: [PATCH V7 2/4] tpm: Reserve the TPM final events table
On Mon, 20 May 2019 at 21:55, Matthew Garrett <matthewgarrett@...gle.com> wrote:
>
> From: Matthew Garrett <mjg59@...gle.com>
>
> UEFI systems provide a boot services protocol for obtaining the TPM
> event log, but this is unusable after ExitBootServices() is called.
> Unfortunately ExitBootServices() itself triggers additional TPM events
> that then can't be obtained using this protocol. The platform provides a
> mechanism for the OS to obtain these events by recording them to a
> separate UEFI configuration table which the OS can then map.
>
> Unfortunately this table isn't self describing in terms of providing its
> length, so we need to parse the events inside it to figure out how long
> it is. Since the table isn't mapped at this point, we need to extend the
> length calculation function to be able to map the event as it goes
> along.
>
> (Fixes by Bartosz Szczepanek <bsz@...ihalf.com>)
>
> Signed-off-by: Matthew Garrett <mjg59@...gle.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> ---
> drivers/char/tpm/eventlog/tpm2.c | 2 +-
> drivers/firmware/efi/efi.c | 2 +
> drivers/firmware/efi/tpm.c | 62 ++++++++++++++++++-
> include/linux/efi.h | 9 +++
> include/linux/tpm_eventlog.h | 102 ++++++++++++++++++++++++++++---
> 5 files changed, 164 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/char/tpm/eventlog/tpm2.c b/drivers/char/tpm/eventlog/tpm2.c
> index 1a977bdd3bd2..de1d9f7e5a92 100644
> --- a/drivers/char/tpm/eventlog/tpm2.c
> +++ b/drivers/char/tpm/eventlog/tpm2.c
> @@ -40,7 +40,7 @@
> static size_t calc_tpm2_event_size(struct tcg_pcr_event2_head *event,
> struct tcg_pcr_event *event_header)
> {
> - return __calc_tpm2_event_size(event, event_header);
> + return __calc_tpm2_event_size(event, event_header, false);
> }
>
> static void *tpm2_bios_measurements_start(struct seq_file *m, loff_t *pos)
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index 55b77c576c42..6b11c41e0575 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -53,6 +53,7 @@ struct efi __read_mostly efi = {
> .mem_attr_table = EFI_INVALID_TABLE_ADDR,
> .rng_seed = EFI_INVALID_TABLE_ADDR,
> .tpm_log = EFI_INVALID_TABLE_ADDR,
> + .tpm_final_log = EFI_INVALID_TABLE_ADDR,
> .mem_reserve = EFI_INVALID_TABLE_ADDR,
> };
> EXPORT_SYMBOL(efi);
> @@ -485,6 +486,7 @@ static __initdata efi_config_table_type_t common_tables[] = {
> {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},
> + {LINUX_EFI_TPM_FINAL_LOG_GUID, "TPMFinalLog", &efi.tpm_final_log},
> {LINUX_EFI_MEMRESERVE_TABLE_GUID, "MEMRESERVE", &efi.mem_reserve},
> {NULL_GUID, NULL, NULL},
> };
> diff --git a/drivers/firmware/efi/tpm.c b/drivers/firmware/efi/tpm.c
> index 3a689b40ccc0..2c912ea08166 100644
> --- a/drivers/firmware/efi/tpm.c
> +++ b/drivers/firmware/efi/tpm.c
> @@ -4,34 +4,90 @@
> * Thiebaud Weksteen <tweek@...gle.com>
> */
>
> +#define TPM_MEMREMAP(start, size) early_memremap(start, size)
> +#define TPM_MEMUNMAP(start, size) early_memunmap(start, size)
> +
> #include <linux/efi.h>
> #include <linux/init.h>
> #include <linux/memblock.h>
> +#include <linux/tpm_eventlog.h>
>
> #include <asm/early_ioremap.h>
>
> +int efi_tpm_final_log_size;
> +EXPORT_SYMBOL(efi_tpm_final_log_size);
> +
> +static int tpm2_calc_event_log_size(void *data, int count, void *size_info)
> +{
> + struct tcg_pcr_event2_head *header;
> + int event_size, size = 0;
> +
> + while (count > 0) {
> + header = data + size;
> + event_size = __calc_tpm2_event_size(header, size_info, true);
> + if (event_size == 0)
> + return -1;
> + size += event_size;
> + count--;
> + }
> +
> + return size;
> +}
> +
> /*
> * 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;
> + struct efi_tcg2_final_events_table *final_tbl;
> unsigned int tbl_size;
> + int ret = 0;
>
> - if (efi.tpm_log == EFI_INVALID_TABLE_ADDR)
> + if (efi.tpm_log == EFI_INVALID_TABLE_ADDR) {
> + /*
> + * We can't calculate the size of the final events without the
> + * first entry in the TPM log, so bail here.
> + */
> 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.tpm_log = EFI_INVALID_TABLE_ADDR;
> return -ENOMEM;
> }
>
> tbl_size = sizeof(*log_tbl) + log_tbl->size;
> memblock_reserve(efi.tpm_log, tbl_size);
> +
> + if (efi.tpm_final_log == EFI_INVALID_TABLE_ADDR)
> + goto out;
> +
> + final_tbl = early_memremap(efi.tpm_final_log, sizeof(*final_tbl));
> +
> + if (!final_tbl) {
> + pr_err("Failed to map TPM Final Event Log table @ 0x%lx\n",
> + efi.tpm_final_log);
> + efi.tpm_final_log = EFI_INVALID_TABLE_ADDR;
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + tbl_size = tpm2_calc_event_log_size(efi.tpm_final_log
> + + sizeof(final_tbl->version)
> + + sizeof(final_tbl->nr_events),
> + final_tbl->nr_events,
> + log_tbl->log);
> + memblock_reserve((unsigned long)final_tbl,
> + tbl_size + sizeof(*final_tbl));
> + early_memunmap(final_tbl, sizeof(*final_tbl));
> + efi_tpm_final_log_size = tbl_size;
> +
> +out:
> early_memunmap(log_tbl, sizeof(*log_tbl));
> - return 0;
> + return ret;
> }
>
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index 54357a258b35..e33c70a52a9d 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -689,6 +689,7 @@ void efi_native_runtime_setup(void);
> #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)
> +#define LINUX_EFI_TPM_FINAL_LOG_GUID EFI_GUID(0x1e2ed096, 0x30e2, 0x4254, 0xbd, 0x89, 0x86, 0x3b, 0xbe, 0xf8, 0x23, 0x25)
> #define LINUX_EFI_MEMRESERVE_TABLE_GUID EFI_GUID(0x888eb0c6, 0x8ede, 0x4ff5, 0xa8, 0xf0, 0x9a, 0xee, 0x5c, 0xb9, 0x77, 0xc2)
>
> typedef struct {
> @@ -996,6 +997,7 @@ extern struct efi {
> unsigned long mem_attr_table; /* memory attributes table */
> unsigned long rng_seed; /* UEFI firmware random seed */
> unsigned long tpm_log; /* TPM2 Event Log table */
> + unsigned long tpm_final_log; /* TPM2 Final Events Log table */
> unsigned long mem_reserve; /* Linux EFI memreserve table */
> efi_get_time_t *get_time;
> efi_set_time_t *set_time;
> @@ -1707,6 +1709,13 @@ struct linux_efi_tpm_eventlog {
>
> extern int efi_tpm_eventlog_init(void);
>
> +struct efi_tcg2_final_events_table {
> + u64 version;
> + u64 nr_events;
> + u8 events[];
> +};
> +extern int efi_tpm_final_log_size;
> +
> /*
> * efi_runtime_service() function identifiers.
> * "NONE" is used by efi_recover_from_page_fault() to check if the page
> diff --git a/include/linux/tpm_eventlog.h b/include/linux/tpm_eventlog.h
> index 6a86144e13f1..63238c84dc0b 100644
> --- a/include/linux/tpm_eventlog.h
> +++ b/include/linux/tpm_eventlog.h
> @@ -112,10 +112,35 @@ struct tcg_pcr_event2_head {
> struct tpm_digest digests[];
> } __packed;
>
> +struct tcg_algorithm_size {
> + u16 algorithm_id;
> + u16 algorithm_size;
> +};
> +
> +struct tcg_algorithm_info {
> + u8 signature[16];
> + u32 platform_class;
> + u8 spec_version_minor;
> + u8 spec_version_major;
> + u8 spec_errata;
> + u8 uintn_size;
> + u32 number_of_algorithms;
> + struct tcg_algorithm_size digest_sizes[];
> +};
> +
> +#ifndef TPM_MEMREMAP
> +#define TPM_MEMREMAP(start, size) NULL
> +#endif
> +
> +#ifndef TPM_MEMUNMAP
> +#define TPM_MEMUNMAP(start, size) do{} while(0)
> +#endif
> +
> /**
> * __calc_tpm2_event_size - calculate the size of a TPM2 event log entry
> * @event: Pointer to the event whose size should be calculated
> * @event_header: Pointer to the initial event containing the digest lengths
> + * @do_mapping: Whether or not the event needs to be mapped
> *
> * The TPM2 event log format can contain multiple digests corresponding to
> * separate PCR banks, and also contains a variable length of the data that
> @@ -131,10 +156,13 @@ struct tcg_pcr_event2_head {
> */
>
> static inline int __calc_tpm2_event_size(struct tcg_pcr_event2_head *event,
> - struct tcg_pcr_event *event_header)
> + struct tcg_pcr_event *event_header,
> + bool do_mapping)
> {
> struct tcg_efi_specid_event_head *efispecid;
> struct tcg_event_field *event_field;
> + void *mapping = NULL;
> + int mapping_size;
> void *marker;
> void *marker_start;
> u32 halg_size;
> @@ -148,16 +176,49 @@ static inline int __calc_tpm2_event_size(struct tcg_pcr_event2_head *event,
> marker = marker + sizeof(event->pcr_idx) + sizeof(event->event_type)
> + sizeof(event->count);
>
> + /* Map the event header */
> + if (do_mapping) {
> + mapping_size = marker - marker_start;
> + mapping = TPM_MEMREMAP((unsigned long)marker_start,
> + mapping_size);
> + if (!mapping) {
> + size = 0;
> + goto out;
> + }
> + } else {
> + mapping = marker_start;
> + }
> +
> + event = (struct tcg_pcr_event2_head *)mapping;
> +
> efispecid = (struct tcg_efi_specid_event_head *)event_header->event;
>
> /* Check if event is malformed. */
> - if (event->count > efispecid->num_algs)
> - return 0;
> + if (event->count > efispecid->num_algs) {
> + size = 0;
> + goto out;
> + }
>
> for (i = 0; i < event->count; i++) {
> halg_size = sizeof(event->digests[i].alg_id);
> - memcpy(&halg, marker, halg_size);
> +
> + /* Map the digest's algorithm identifier */
> + if (do_mapping) {
> + TPM_MEMUNMAP(mapping, mapping_size);
> + mapping_size = halg_size;
> + mapping = TPM_MEMREMAP((unsigned long)marker,
> + mapping_size);
> + if (!mapping) {
> + size = 0;
> + goto out;
> + }
> + } else {
> + mapping = marker;
> + }
> +
> + memcpy(&halg, mapping, halg_size);
> marker = marker + halg_size;
> +
> for (j = 0; j < efispecid->num_algs; j++) {
> if (halg == efispecid->digest_sizes[j].alg_id) {
> marker +=
> @@ -166,18 +227,41 @@ static inline int __calc_tpm2_event_size(struct tcg_pcr_event2_head *event,
> }
> }
> /* Algorithm without known length. Such event is unparseable. */
> - if (j == efispecid->num_algs)
> - return 0;
> + if (j == efispecid->num_algs) {
> + size = 0;
> + goto out;
> + }
> + }
> +
> + /*
> + * Map the event size - we don't read from the event itself, so
> + * we don't need to map it
> + */
> + if (do_mapping) {
> + TPM_MEMUNMAP(mapping, mapping_size);
> + mapping_size += sizeof(event_field->event_size);
> + mapping = TPM_MEMREMAP((unsigned long)marker,
> + mapping_size);
> + if (!mapping) {
> + size = 0;
> + goto out;
> + }
> + } else {
> + mapping = marker;
> }
>
> - event_field = (struct tcg_event_field *)marker;
> + event_field = (struct tcg_event_field *)mapping;
> +
> marker = marker + sizeof(event_field->event_size)
> + event_field->event_size;
> size = marker - marker_start;
>
> if ((event->event_type == 0) && (event_field->event_size == 0))
> - return 0;
> -
> + size = 0;
> +out:
> + if (do_mapping)
> + TPM_MEMUNMAP(mapping, mapping_size);
> return size;
> }
> +
> #endif
> --
> 2.21.0.1020.gf2820cf01a-goog
>
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