From 166a2809d65b282272c474835ec22c882a39ca1b Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Fri, 7 Jun 2019 13:51:47 -0700 Subject: [PATCH] tpm: Don't duplicate events from the final event log in the TCG2 log After the first call to GetEventLog() on UEFI systems using the TCG2 crypto agile log format, any further log events (other than those triggered by ExitBootServices()) will be logged in both the main log and also in the Final Events Log. While the kernel only calls GetEventLog() immediately before ExitBootServices(), we can't control whether earlier parts of the boot process have done so. This will result in log entries that exist in both logs, and so the current approach of simply appending the Final Event Log to the main log will result in events being duplicated. We can avoid this problem by looking at the size of the Final Event Log just before we call ExitBootServices() and exporting this to the main kernel. The kernel can then skip over all events that occured before ExitBootServices() and only append events that were not also logged to the main log. Signed-off-by: Matthew Garrett Reported-by: Joe Richey Suggested-by: Joe Richey Acked-by: Ard Biesheuvel Reviewed-by: Jarkko Sakkinen Tested-by: Jarkko Sakkinen Signed-off-by: Jarkko Sakkinen --- drivers/char/tpm/eventlog/efi.c | 11 ++++++++++- drivers/firmware/efi/libstub/tpm.c | 30 ++++++++++++++++++++++++++++++ include/linux/efi.h | 1 + 3 files changed, 41 insertions(+), 1 deletion(-) diff --git a/drivers/char/tpm/eventlog/efi.c b/drivers/char/tpm/eventlog/efi.c index 73b981026627..6bb023de17f1 100644 --- a/drivers/char/tpm/eventlog/efi.c +++ b/drivers/char/tpm/eventlog/efi.c @@ -75,6 +75,8 @@ int tpm_read_log_efi(struct tpm_chip *chip) goto out; } + efi_tpm_final_log_size -= log_tbl->final_events_preboot_size; + tmp = krealloc(log->bios_event_log, log_size + efi_tpm_final_log_size, GFP_KERNEL); @@ -85,8 +87,15 @@ int tpm_read_log_efi(struct tpm_chip *chip) } log->bios_event_log = tmp; + + /* + * Copy any of the final events log that didn't also end up in the + * main log. Events can be logged in both if events are generated + * between GetEventLog() and ExitBootServices(). + */ memcpy((void *)log->bios_event_log + log_size, - final_tbl->events, efi_tpm_final_log_size); + final_tbl->events + log_tbl->final_events_preboot_size, + efi_tpm_final_log_size); log->bios_event_log_end = log->bios_event_log + log_size + efi_tpm_final_log_size; diff --git a/drivers/firmware/efi/libstub/tpm.c b/drivers/firmware/efi/libstub/tpm.c index 6b3b507a54eb..eb9af83e4d59 100644 --- a/drivers/firmware/efi/libstub/tpm.c +++ b/drivers/firmware/efi/libstub/tpm.c @@ -64,11 +64,13 @@ void efi_retrieve_tpm2_eventlog(efi_system_table_t *sys_table_arg) efi_status_t status; efi_physical_addr_t log_location = 0, log_last_entry = 0; struct linux_efi_tpm_eventlog *log_tbl = NULL; + struct efi_tcg2_final_events_table *final_events_table; unsigned long first_entry_addr, last_entry_addr; size_t log_size, last_entry_size; efi_bool_t truncated; int version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_2; void *tcg2_protocol = NULL; + int final_events_size = 0; status = efi_call_early(locate_protocol, &tcg2_guid, NULL, &tcg2_protocol); @@ -134,8 +136,36 @@ void efi_retrieve_tpm2_eventlog(efi_system_table_t *sys_table_arg) return; } + /* + * Figure out whether any events have already been logged to the + * final events structure, and if so how much space they take up + */ + final_events_table = get_efi_config_table(sys_table_arg, + LINUX_EFI_TPM_FINAL_LOG_GUID); + if (final_events_table && final_events_table->nr_events) { + struct tcg_pcr_event2_head *header; + int offset; + void *data; + int event_size; + int i = final_events_table->nr_events; + + data = (void *)final_events_table; + offset = sizeof(final_events_table->version) + + sizeof(final_events_table->nr_events); + + while (i > 0) { + header = data + offset + final_events_size; + event_size = __calc_tpm2_event_size(header, + (void *)(long)log_location, + false); + final_events_size += event_size; + i--; + } + } + memset(log_tbl, 0, sizeof(*log_tbl) + log_size); log_tbl->size = log_size; + log_tbl->final_events_preboot_size = final_events_size; log_tbl->version = version; memcpy(log_tbl->log, (void *) first_entry_addr, log_size); diff --git a/include/linux/efi.h b/include/linux/efi.h index b391263d8ec6..f87fabea4a85 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -1708,6 +1708,7 @@ struct linux_efi_random_seed { struct linux_efi_tpm_eventlog { u32 size; + u32 final_events_preboot_size; u8 version; u8 log[]; };