[PATCH 2/2] efi_loader: add PE/COFF image measurement
Heinrich Schuchardt
xypron.glpk at gmx.de
Thu Apr 22 10:18:38 CEST 2021
On 22.04.21 10:09, Ilias Apalodimas wrote:
>>>> + if (!(active & alg_to_mask(hash_alg)))
>>>> + continue;
>>>> + switch (hash_alg) {
>>>> + case TPM2_ALG_SHA1:
>>>
>>> SHA1 is known to be unsafe. Why would we support it?
>>
>> Basically I agree with removing SHA1 support.
>> This efi_tcg2.c implementation aims to support TCG v2, so there is no
>> reason to keep SHA1.
>> Anyway, SHA1 is supported in tcg2_create_digest() for the measurement
>> other than PE/COFF image. Do we also remove SHA1 from
>> tcg2_create_digest()?
>>
>
> The hardware dictates what kind of SHAxxx you are supposed to add in the
> EventLog and the PCRs. Why would we remove the functionality? If someone
> considers SHA1 unsafe, he can just disable it from his hardware and remove it
> from the active algorithms.
>
>
> Cheers
> /Ilias
The TCG EFI ProtocolSpecification explicitely enumerates the four
hashing algorithms of Masahisa's patch, see chapter 6.4.3, "Related
Definitions".
So let's support them.
Best regards
Heinrich
>
>> For other comments, I will modify the code and send v2 patch.
>>
>> Thanks,
>> Masahisa
>>
>>
>> On Wed, 21 Apr 2021 at 19:57, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>>>
>>> On 4/15/21 3:30 PM, Masahisa Kojima wrote:
>>>> "TCG PC Client Platform Firmware Profile Specification"
>>>> requires to measure every attempt to load and execute
>>>> a OS Loader(a UEFI application) into PCR[4].
>>>> This commit adds the PE/COFF image measurement, extends PCR,
>>>> and appends measurement into Event Log.
>>>>
>>>> Signed-off-by: Masahisa Kojima <masahisa.kojima at linaro.org>
>>>> ---
>>>> include/efi_loader.h | 4 +
>>>> include/efi_tcg2.h | 10 ++
>>>> include/tpm-v2.h | 1 +
>>>> lib/efi_loader/efi_image_loader.c | 7 ++
>>>> lib/efi_loader/efi_tcg2.c | 187 ++++++++++++++++++++++++++++--
>>>> 5 files changed, 199 insertions(+), 10 deletions(-)
>>>>
>>>> diff --git a/include/efi_loader.h b/include/efi_loader.h
>>>> index de1a496a97..b02bc93c8e 100644
>>>> --- a/include/efi_loader.h
>>>> +++ b/include/efi_loader.h
>>>> @@ -426,6 +426,10 @@ efi_status_t efi_disk_register(void);
>>>> efi_status_t efi_rng_register(void);
>>>> /* Called by efi_init_obj_list() to install EFI_TCG2_PROTOCOL */
>>>> efi_status_t efi_tcg2_register(void);
>>>> +/* measure the pe-coff image, extend PCR and add Event Log */
>>>> +efi_status_t tcg2_measure_pe_image(void *efi, u64 efi_size,
>>>> + struct efi_loaded_image_obj *handle,
>>>> + struct efi_loaded_image *loaded_image_info);
>>>> /* Create handles and protocols for the partitions of a block device */
>>>> int efi_disk_create_partitions(efi_handle_t parent, struct blk_desc *desc,
>>>> const char *if_typename, int diskid,
>>>> diff --git a/include/efi_tcg2.h b/include/efi_tcg2.h
>>>> index 40e241ce31..f8d46c5fd2 100644
>>>> --- a/include/efi_tcg2.h
>>>> +++ b/include/efi_tcg2.h
>>>> @@ -9,6 +9,8 @@
>>>> #if !defined _EFI_TCG2_PROTOCOL_H_
>>>> #define _EFI_TCG2_PROTOCOL_H_
>>>>
>>>> +#include <efi.h>
>>>
>>> This include is already included in efi_api.h.
>>>
>>>> +#include <efi_api.h>
>>>> #include <tpm-v2.h>
>>>>
>>>> #define EFI_TCG2_PROTOCOL_GUID \
>>>> @@ -53,6 +55,14 @@ struct efi_tcg2_event {
>>>> u8 event[];
>>>> } __packed;
>>>>
>>>> +struct uefi_image_load_event {
>>>> + efi_physical_addr_t image_location_in_memory;
>>>> + u64 image_length_in_memory;
>>>> + u64 image_link_time_address;
>>>> + u64 length_of_device_path;
>>>> + struct efi_device_path device_path[];
>>>
>>> A device path is not an array of struct efi_device_path. But the first
>>> element is of this type. So ok.
>>>
>>>> +} __packed;
>>>
>>> Why should this be __packed? You don't use arrays of this structure and
>>> it is naturally packed.
>>>
>>>> +
>>>> struct efi_tcg2_boot_service_capability {
>>>> u8 size;
>>>> struct efi_tcg2_version structure_version;
>>>> diff --git a/include/tpm-v2.h b/include/tpm-v2.h
>>>> index df67a196cf..ab9c04dc0a 100644
>>>> --- a/include/tpm-v2.h
>>>> +++ b/include/tpm-v2.h
>>>> @@ -61,6 +61,7 @@ struct udevice;
>>>> #define EV_S_CRTM_VERSION ((u32)0x00000008)
>>>> #define EV_CPU_MICROCODE ((u32)0x00000009)
>>>> #define EV_TABLE_OF_DEVICES ((u32)0x0000000B)
>>>
>>> Please, add a comment here that the following values are defined in the
>>> "TCG EFI Platform Specification".
>>>
>>>> +#define EV_EFI_BOOT_SERVICES_APPLICATION ((u32)0x80000003)
>>>
>>> Please, add all EV_EFI_* constants.
>>>
>>>>
>>>> /* TPMS_TAGGED_PROPERTY Structure */
>>>> struct tpms_tagged_property {
>>>> diff --git a/lib/efi_loader/efi_image_loader.c b/lib/efi_loader/efi_image_loader.c
>>>> index 2c35cb5651..b032ec5dd8 100644
>>>> --- a/lib/efi_loader/efi_image_loader.c
>>>> +++ b/lib/efi_loader/efi_image_loader.c
>>>> @@ -829,6 +829,13 @@ efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle,
>>>> goto err;
>>>> }
>>>>
>>>> +#if CONFIG_IS_ENABLED(EFI_TCG2_PROTOCOL)
>>>> + /* Measure an PE/COFF image */
>>>> + if (tcg2_measure_pe_image(efi, efi_size, handle,
>>>> + loaded_image_info))
>>>> + log_err("PE image measurement failed\n");
>>>> +#endif
>>>> +
>>>> /* Copy PE headers */
>>>> memcpy(efi_reloc, efi,
>>>> sizeof(*dos)
>>>> diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
>>>> index ed86a220fb..9fab07605f 100644
>>>> --- a/lib/efi_loader/efi_tcg2.c
>>>> +++ b/lib/efi_loader/efi_tcg2.c
>>>> @@ -13,8 +13,10 @@
>>>> #include <efi_loader.h>
>>>> #include <efi_tcg2.h>
>>>> #include <log.h>
>>>> +#include <malloc.h>
>>>> #include <version.h>
>>>> #include <tpm-v2.h>
>>>> +#include <u-boot/rsa.h>
>>>> #include <u-boot/sha1.h>
>>>> #include <u-boot/sha256.h>
>>>> #include <u-boot/sha512.h>
>>>> @@ -709,6 +711,172 @@ out:
>>>> return EFI_EXIT(ret);
>>>> }
>>>>
>>>> +static efi_status_t tcg2_hash_pe_image(void *efi, u64 efi_size,
>>>> + struct tpml_digest_values *digest_list)
>>>> +{
>>>> + IMAGE_NT_HEADERS32 *nt;
>>>> + WIN_CERTIFICATE *wincerts = NULL;
>>>> + size_t wincerts_len;
>>>> + struct efi_image_regions *regs = NULL;
>>>> + void *new_efi = NULL;
>>>> + size_t new_efi_size;
>>>> + u8 hash[TPM2_SHA512_DIGEST_SIZE];
>>>> + efi_status_t ret;
>>>> + u32 active;
>>>> + int i;
>>>> +
>>>> + ret = efi_check_pe(efi, efi_size, (void **)&nt);
>>> Why are you calling this function? It is already called in efi_load_pe().
>>>
>>>> + if (ret != EFI_SUCCESS) {
>>>> + log_err("Not a valid PE-COFF file\n");
>>>> + return EFI_INVALID_PARAMETER;
>>>> + }
>>>> +
>>>> + /*
>>>> + * Size must be 8-byte aligned and the trailing bytes must be
>>>> + * zero'ed. Otherwise hash value may be incorrect.
>>>> + */
>>>> + if (!IS_ALIGNED(efi_size, 8)) {
>>>> + new_efi_size = ALIGN(efi_size, 8);
>>>> + new_efi = calloc(new_efi_size, 1);
>>>> + if (!new_efi)
>>>> + return EFI_OUT_OF_RESOURCES;
>>>> + memcpy(new_efi, efi, efi_size);
>>>> + efi = new_efi;
>>>> + efi_size = new_efi_size;
>>>> + }
>>>> +
>>>> + if (!efi_image_parse(efi, efi_size, ®s, &wincerts,
>>>> + &wincerts_len)) {
>>>> + log_err("Parsing PE executable image failed\n");
>>>> + ret = EFI_INVALID_PARAMETER;
>>>> + goto out;
>>>> + }
>>>
>>> Please, don't duplicate code from efi_image_authenticate(). Extract a
>>> common function instead.
>>>
>>>> +
>>>> + ret = __get_active_pcr_banks(&active);
>>>> + if (ret != EFI_SUCCESS) {
>>>> + ret = EFI_DEVICE_ERROR;
>>>> + goto out;
>>>> + }
>>>> +
>>>> + digest_list->count = 0;
>>>> + for (i = 0; i < MAX_HASH_COUNT; i++) {
>>>> + u16 hash_alg = hash_algo_list[i].hash_alg;
>>>> +
>>>> + if (!(active & alg_to_mask(hash_alg)))
>>>> + continue;
>>>> + switch (hash_alg) {
>>>> + case TPM2_ALG_SHA1:
>>>
>>> SHA1 is known to be unsafe. Why would we support it?
>>>
>>>> + hash_calculate("sha1", regs->reg, regs->num, hash);
>>>> + digest_list->count++;
>>>
>>> Why do you repeat this line in every case of the switch statement?
>>> Please, put it below.
>>>
>>>> + break;
>>>> + case TPM2_ALG_SHA256:
>>>> + hash_calculate("sha256", regs->reg, regs->num, hash);
>>>> + digest_list->count++;
>>>> + break;
>>>> + case TPM2_ALG_SHA384:
>>>> + hash_calculate("sha384", regs->reg, regs->num, hash);
>>>> + digest_list->count++;
>>>> + break;
>>>> + case TPM2_ALG_SHA512:
>>>> + hash_calculate("sha512", regs->reg, regs->num, hash);
>>>> + digest_list->count++;
>>>> + break;
>>>> + default:
>>>> + EFI_PRINT("Unsupported algorithm %x\n", hash_alg);
>>>> + return EFI_INVALID_PARAMETER;
>>>> + }
>>>> + digest_list->digests[i].hash_alg = hash_alg;
>>>> + memcpy(&digest_list->digests[i].digest, hash, (u32)alg_to_len(hash_alg));
>>>> + }
>>>> +
>>>> +out:
>>>> + free(new_efi);
>>>> + free(regs);
>>>> +
>>>> + return ret;
>>>> +}
>>>> +
>>>> +efi_status_t tcg2_measure_pe_image(void *efi, u64 efi_size,
>>>> + struct efi_loaded_image_obj *handle,
>>>> + struct efi_loaded_image *loaded_image)
>>>> +{
>>>> + struct tpml_digest_values digest_list;
>>>> + efi_status_t ret;
>>>> + struct udevice *dev;
>>>> + u32 pcr_index, event_type, event_size;
>>>> + struct uefi_image_load_event *image_load_event;
>>>> + u8 *event;
>>>
>>> The variable event is not needed. You can use image_load_event directly.
>>>
>>>> + struct efi_device_path *device_path;
>>>> + u32 device_path_length;
>>>> + IMAGE_DOS_HEADER *dos;
>>>> + IMAGE_NT_HEADERS32 *nt;
>>>> +
>>>> + ret = platform_get_tpm2_device(&dev);
>>>> + if (ret != EFI_SUCCESS)
>>>> + return ret;
>>>> +
>>>> + if (handle->image_type == IMAGE_SUBSYSTEM_EFI_APPLICATION) {
>>>
>>> We should measure drivers too. Cf.
>>> EV_EFI_BOOT_SERVICES_DRIVER, EV_EFI_RUNTIME_SERVICES_DRIVER.
>>>
>>>> + pcr_index = 4;
>>>> + event_type = EV_EFI_BOOT_SERVICES_APPLICATION;
>>>> + } else {
>>>> + return EFI_UNSUPPORTED;
>>>> + }
>>>> +
>>>> + ret = tcg2_hash_pe_image(efi, efi_size, &digest_list);
>>>> + if (ret != EFI_SUCCESS)
>>>> + return ret;
>>>> +
>>>> + ret = tcg2_pcr_extend(dev, pcr_index, &digest_list);
>>>> + if (ret != EFI_SUCCESS)
>>>> + return ret;
>>>> +
>>>> + loaded_image->system_table->boottime->handle_protocol(&handle->header,
>>>> + &efi_guid_loaded_image_device_path,
>>>> + (void **)&device_path);
>>>
>>> You would have to use EFI_CALL() here.
>>>
>>> Please, use efi_search_protocol() instead of all this indirection.
>>>
>>> Best regards
>>>
>>> Heinrich
>>>
>>>> + device_path_length = efi_dp_size(device_path);
>>>> + if (device_path_length > 0) {
>>>> + /* add end node size */
>>>> + device_path_length += sizeof(struct efi_device_path);
>>>> + }
>>>> + event_size = sizeof(struct uefi_image_load_event) + device_path_length;
>>>> + event = malloc(event_size);
>>>> + if (!event)
>>>> + return EFI_OUT_OF_RESOURCES;
>>>> +
>>>> + image_load_event = (struct uefi_image_load_event *)event;
>>>> + image_load_event->image_location_in_memory = (efi_physical_addr_t)efi;
>>>> + image_load_event->image_length_in_memory = efi_size;
>>>> + image_load_event->length_of_device_path = device_path_length;
>>>> +
>>>> + dos = (IMAGE_DOS_HEADER *)efi;
>>>> + nt = (IMAGE_NT_HEADERS32 *)(efi + dos->e_lfanew);
>>>> + if (nt->OptionalHeader.Magic == IMAGE_NT_OPTIONAL_HDR64_MAGIC) {
>>>> + IMAGE_NT_HEADERS64 *nt64 = (IMAGE_NT_HEADERS64 *)nt;
>>>> +
>>>> + image_load_event->image_link_time_address =
>>>> + nt64->OptionalHeader.ImageBase;
>>>> + } else if (nt->OptionalHeader.Magic == IMAGE_NT_OPTIONAL_HDR32_MAGIC) {
>>>> + image_load_event->image_link_time_address =
>>>> + nt->OptionalHeader.ImageBase;
>>>> + } else {
>>>> + ret = EFI_INVALID_PARAMETER;
>>>> + goto out;
>>>> + }
>>>> +
>>>> + if (device_path_length > 0) {
>>>> + memcpy(image_load_event->device_path, device_path,
>>>> + device_path_length);
>>>> + }
>>>> +
>>>> + ret = tcg2_agile_log_append(pcr_index, event_type, &digest_list,
>>>> + event_size, event);
>>>> +
>>>> +out:
>>>> + free(event);
>>>> +
>>>> + return ret;
>>>> +}
>>>> +
>>>> /**
>>>> * efi_tcg2_hash_log_extend_event() - extend and optionally log events
>>>> *
>>>> @@ -761,24 +929,23 @@ efi_tcg2_hash_log_extend_event(struct efi_tcg2_protocol *this, u64 flags,
>>>> /*
>>>> * if PE_COFF_IMAGE is set we need to make sure the image is not
>>>> * corrupted, verify it and hash the PE/COFF image in accordance with
>>>> - * the procedure specified in "Calculating the PE Image Hash"
>>>> - * section of the "Windows Authenticode Portable Executable Signature
>>>> + * the procedure specified in "Calculating the PE Image Hash"
>>>> + * section of the "Windows Authenticode Portable Executable Signature
>>>> * Format"
>>>> - * Not supported for now
>>>> */
>>>> if (flags & PE_COFF_IMAGE) {
>>>> - ret = EFI_UNSUPPORTED;
>>>> - goto out;
>>>> + ret = tcg2_hash_pe_image((void *)data_to_hash, data_to_hash_len,
>>>> + &digest_list);
>>>> + } else {
>>>> + ret = tcg2_create_digest((u8 *)data_to_hash, data_to_hash_len,
>>>> + &digest_list);
>>>> }
>>>> + if (ret != EFI_SUCCESS)
>>>> + goto out;
>>>>
>>>> pcr_index = efi_tcg_event->header.pcr_index;
>>>> event_type = efi_tcg_event->header.event_type;
>>>>
>>>> - ret = tcg2_create_digest((u8 *)data_to_hash, data_to_hash_len,
>>>> - &digest_list);
>>>> - if (ret != EFI_SUCCESS)
>>>> - goto out;
>>>> -
>>>> ret = tcg2_pcr_extend(dev, pcr_index, &digest_list);
>>>> if (ret != EFI_SUCCESS)
>>>> goto out;
>>>>
>>>
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