[PATCH 1/4] tools: mkeficapsule: add firmwware image signing

Heinrich Schuchardt
2021-05-13T06:52:18Z

Am 13. Mai 2021 08:44:24 MESZ schrieb Masami Hiramatsu <masami.hiramatsu@linaro.org>:
>Hi Heinrich,
>
>2021?5?13?(?) 14:50 Heinrich Schuchardt <xypron.glpk@gmx.de>:
>>
>> On 5/13/21 7:12 AM, Masami Hiramatsu wrote:
>> > Hi Heinrich,
>> >
>> > 2021?5?13?(?) 13:22 Heinrich Schuchardt <xypron.glpk@gmx.de>:
>> >>
>> >> On 5/13/21 5:08 AM, AKASHI Takahiro wrote:
>> >>> On Wed, May 12, 2021 at 10:56:41AM +0200, Heinrich Schuchardt
>wrote:
>> >>>> On 12.05.21 06:57, AKASHI Takahiro wrote:
>> >>>>> With this enhancement, mkeficapsule will be able to create a
>capsule
>> >>>>> file with a signature which will be verified later by FMP's
>SetImage().
>> >>>>>
>> >>>>> We will have to specify addtional command parameters:
>> >>>>> -monotonic-cout <count> : monotonic count
>> >>>>> -private-key <private key file> : private key file
>> >>>>> -certificate <certificate file> : certificate file
>> >>>>> Only when those parameters are given, a signature will be added
>> >>>>> to a capsule file.
>> >>>>>
>> >>>>> Users are expected to maintain the monotonic count for each
>firmware
>> >>>>> image.
>> >>>>>
>> >>>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
>> >>>>> ---
>> >>>>> tools/Makefile | 4 +
>> >>>>> tools/mkeficapsule.c | 324
>+++++++++++++++++++++++++++++++++++++++----
>> >>>>> 2 files changed, 303 insertions(+), 25 deletions(-)
>> >>>>>
>> >>>>> diff --git a/tools/Makefile b/tools/Makefile
>> >>>>> index d020c55d6644..02eae0286e20 100644
>> >>>>> --- a/tools/Makefile
>> >>>>> +++ b/tools/Makefile
>> >>>>> @@ -231,6 +231,10 @@ hostprogs-$(CONFIG_MIPS) += mips-relocs
>> >>>>> hostprogs-$(CONFIG_ASN1_COMPILER) += asn1_compiler
>> >>>>> HOSTCFLAGS_asn1_compiler.o = -idirafter $(srctree)/include
>> >>>>>
>> >>>>> +ifneq ($(CONFIG_EFI_CAPSULE_AUTHENTICATE),)
>> >>>>> +HOSTLDLIBS_mkeficapsule += \
>> >>>>> + $(shell pkg-config --libs libssl libcrypto 2> /dev/null ||
>echo "-lssl -lcrypto")
>> >>>>
>> >>>> I don't expect any user wants to install two tool versions in
>parallel.
>> >>>>
>> >>>> The tool should always be able to add a signature.
>> >>>> Adding a signature must be optional.
>> >>>
>> >>> It seems to me that those two statements mutually contradict.
>> >>> Or do you intend to say that we should have a separate kconfig
>> >>> option to enable/disable signing feature in mkeficapsule?
>> >>>
>> >>> If so, I can agree.
>> >>>
>> >>> In either way, we should have an option to turn on/off this
>functionality
>> >>> as not all users use signed capsules.
>> >>
>> >> I want to have a single binary to distribute with Linux distros
>(e.g.
>> >> Debian/Ubuntu package u-boot-tools).
>> >
>> > I couldn't catch your point. If so, the distros can build u-boot
>with
>> > CONFIG_EFI_CAPSULE_AUTHENTICATE=y...
>>
>> Why should the tool depend on board configuration?
>
>Yeah, at this point I agreed. I think there should be a separated
>CONFIG
>for tools or forcibly link those libraries. (I think most people don't
>mind if it requires new libraries to be built, that usually happens.)
>
>> Who would want capsule updates without authentication?
>
>Hm, so you think even CONFIG_EFI_CAPSULE_AUTHENTICATE is
>only for development. Capsule must be signed, right?
>Then, all distro should build u-boot with
>CONFIG_EFI_CAPSULE_AUTHENTICATE=y, isn't it?

There will still be U-Boot images without capsule updates.

>
>> > BTW, IMHO, if u-boot.bin can not find the ESL in the device tree,
>> > it should skip authentication too.
>>
>> In this case the capsule should be rejected (if
>> CONFIG_EFI_CAPSULE_AUTHENTICATE=y).
>
>I meant U-Boot has NO key to authenticate the capsule. I think in that
>case U-Boot build process must require the key (ESL) and if user
>doesn't
>provide it, the build should fail (if it doesn't skip capsule
>authentication.)
>Or, we have no way to update U-Boot anymore.
>
>> > Then, user can choose whether enabling capsule authentication or
>not
>> > by embedding ESL into their devicetree.
>>
>> The user shall not be able to decide anything that might hamper
>> security. The U-Boot binary must dictate if a capsule is safe.
>
>Hmm, I think the root issue is that the ESL embedding process is not
>integrated into the build process yet. For the safe capsule update,
>we must enable capsule authentication with keys. (unsafe one is only
>for testing/development)
>Moreover, the key is stored in the U-Boot itself OR, in the secure
>storage
>outside of U-Boot (Hardware OTP or TPM/HSM are preferable.)
>
>Thus,
>CONFIG_EFI_CAPSULE_AUTHENTICATE must depend on (or select)
>a new config which points the path for the ESL file (this is embedded
>while
>the build process), OR, the platform driver provides key from its
>hardware
>secure storage.
>
>What would you think about this idea?

That is the direction I would like to go.

Best regards

Heinrich

>
>Thank you,
>
>>
>> Best regards
>>
>> Heinrich
>>
>> >
>> > Thank you
>> >
>> >>
>> >> This should allow both
>> >>
>> >> - create signed capsules
>> >> - create unsigned capsules
>> >>
>> >> The user shall select signing via command line parameters.
>> >>
>> >> Support for signing via the tool shall not depend on board Kconfig
>> >> parameters.
>> >>
>> >> Best regards
>> >>
>> >> Heinrich
>> >>
>> >>>
>> >>>>> +endif
>> >>>>> mkeficapsule-objs := mkeficapsule.o $(LIBFDT_OBJS)
>> >>>>> hostprogs-$(CONFIG_EFI_HAVE_CAPSULE_SUPPORT) += mkeficapsule
>> >>>>>
>> >>>>> diff --git a/tools/mkeficapsule.c b/tools/mkeficapsule.c
>> >>>>> index de0a62898886..34ff1bdd82eb 100644
>> >>>>> --- a/tools/mkeficapsule.c
>> >>>>> +++ b/tools/mkeficapsule.c
>> >>>>> @@ -18,7 +18,17 @@
>> >>>>> #include <sys/stat.h>
>> >>>>> #include <sys/types.h>
>> >>>>>
>> >>>>> -#include "fdt_host.h"
>> >>>>> +#include <linux/kconfig.h>
>> >>>>> +#if IS_ENABLED(CONFIG_EFI_CAPSULE_AUTHENTICATE)
>> >>>>
>> >>>> see above
>> >>>>
>> >>>>> +#include <openssl/asn1.h>
>> >>>>> +#include <openssl/bio.h>
>> >>>>> +#include <openssl/evp.h>
>> >>>>> +#include <openssl/err.h>
>> >>>>> +#include <openssl/pem.h>
>> >>>>> +#include <openssl/pkcs7.h>
>> >>>>> +#endif
>> >>>>> +
>> >>>>> +#include <linux/libfdt.h>
>> >>>>>
>> >>>>> typedef __u8 u8;
>> >>>>> typedef __u16 u16;
>> >>>>> @@ -46,6 +56,13 @@ efi_guid_t efi_guid_image_type_uboot_fit =
>> >>>>> EFI_FIRMWARE_IMAGE_TYPE_UBOOT_FIT_GUID;
>> >>>>> efi_guid_t efi_guid_image_type_uboot_raw =
>> >>>>> EFI_FIRMWARE_IMAGE_TYPE_UBOOT_RAW_GUID;
>> >>>>> +efi_guid_t efi_guid_cert_type_pkcs7 =
>EFI_CERT_TYPE_PKCS7_GUID;
>> >>>>> +
>> >>>>> +#if IS_ENABLED(CONFIG_EFI_CAPSULE_AUTHENTICATE)
>> >>>>
>> >>>> see above
>> >>>>
>> >>>>> +static const char *opts_short = "f:r:i:I:v:D:K:P:C:m:dOh";
>> >>>>> +#else
>> >>>>> +static const char *opts_short = "f:r:i:I:v:D:K:Oh";
>> >>>>> +#endif
>> >>>>>
>> >>>>> static struct option options[] = {
>> >>>>> {"fit", required_argument, NULL, 'f'},
>> >>>>> @@ -54,6 +71,12 @@ static struct option options[] = {
>> >>>>> {"instance", required_argument, NULL, 'I'},
>> >>>>> {"dtb", required_argument, NULL, 'D'},
>> >>>>> {"public key", required_argument, NULL, 'K'},
>> >>>>> +#if IS_ENABLED(CONFIG_EFI_CAPSULE_AUTHENTICATE)
>> >>>>> + {"private-key", required_argument, NULL, 'P'},
>> >>>>> + {"certificate", required_argument, NULL, 'C'},
>> >>>>> + {"monotonic-count", required_argument, NULL, 'm'},
>> >>>>
>> >>>> These options should not be required.
>> >>>
>> >>> I don't get you. What do you mean?
>> >>>
>> >>>>> + {"dump-sig", no_argument, NULL, 'd'},
>> >>>>> +#endif
>> >>>>> {"overlay", no_argument, NULL, 'O'},
>> >>>>> {"help", no_argument, NULL, 'h'},
>> >>>>> {NULL, 0, NULL, 0},
>> >>>>> @@ -70,6 +93,12 @@ static void print_usage(void)
>> >>>>> "\t-I, --instance <instance> update hardware
>instance\n"
>> >>>>> "\t-K, --public-key <key file> public key esl
>file\n"
>> >>>>> "\t-D, --dtb <dtb file> dtb file\n"
>> >>>>> +#if IS_ENABLED(CONFIG_EFI_CAPSULE_AUTHENTICATE)
>> >>>>
>> >>>> see above
>> >>>>
>> >>>>> + "\t-P, --private-key <privkey file> private key
>file\n"
>> >>>>> + "\t-C, --certificate <cert file> signer's
>certificate file\n"
>> >>>>> + "\t-m, --monotonic-count <count> monotonic
>count\n"
>> >>>>> + "\t-d, --dump_sig dump signature
>(*.p7)\n"
>> >>>>> +#endif
>> >>>>> "\t-O, --overlay the dtb file is an
>overlay\n"
>> >>>>> "\t-h, --help print a help
>message\n",
>> >>>>> tool_name);
>> >>>>> @@ -249,12 +278,167 @@ err:
>> >>>>> return ret;
>> >>>>> }
>> >>>>>
>> >>>>> +struct auth_context {
>> >>>>> + char *key_file;
>> >>>>> + char *cert_file;
>> >>>>> + u8 *image_data;
>> >>>>> + size_t image_size;
>> >>>>> + struct efi_firmware_image_authentication auth;
>> >>>>> + u8 *sig_data;
>> >>>>> + size_t sig_size;
>> >>>>> +};
>> >>>>> +
>> >>>>> +static int dump_sig;
>> >>>>> +
>> >>>>> +#if IS_ENABLED(CONFIG_EFI_CAPSULE_AUTHENTICATE)
>> >>>>
>> >>>> see above
>> >>>>
>> >>>>> +static EVP_PKEY *fileio_read_pkey(const char *filename)
>> >>>>> +{
>> >>>>> + EVP_PKEY *key = NULL;
>> >>>>> + BIO *bio;
>> >>>>> +
>> >>>>> + bio = BIO_new_file(filename, "r");
>> >>>>> + if (!bio)
>> >>>>> + goto out;
>> >>>>> +
>> >>>>> + key = PEM_read_bio_PrivateKey(bio, NULL, NULL, NULL);
>> >>>>> +
>> >>>>> +out:
>> >>>>> + BIO_free_all(bio);
>> >>>>> + if (!key) {
>> >>>>> + printf("Can't load key from file '%s'\n",
>filename);
>> >>>>
>> >>>> Please, you use fprintf(stderr,) for error messages.
>> >>>>
>> >>>>> + ERR_print_errors_fp(stderr);
>> >>>>> + }
>> >>>>> +
>> >>>>> + return key;
>> >>>>> +}
>> >>>>> +
>> >>>>> +static X509 *fileio_read_cert(const char *filename)
>> >>>>> +{
>> >>>>> + X509 *cert = NULL;
>> >>>>> + BIO *bio;
>> >>>>> +
>> >>>>> + bio = BIO_new_file(filename, "r");
>> >>>>> + if (!bio)
>> >>>>> + goto out;
>> >>>>> +
>> >>>>> + cert = PEM_read_bio_X509(bio, NULL, NULL, NULL);
>> >>>>> +
>> >>>>> +out:
>> >>>>> + BIO_free_all(bio);
>> >>>>> + if (!cert) {
>> >>>>> + printf("Can't load certificate from file '%s'\n",
>filename);
>> >>>>
>> >>>> fprintf(stderr,)
>> >>>>
>> >>>>> + ERR_print_errors_fp(stderr);
>> >>>>> + }
>> >>>>> +
>> >>>>> + return cert;
>> >>>>> +}
>> >>>>> +
>> >>>>> +static int create_auth_data(struct auth_context *ctx)
>> >>>>> +{
>> >>>>> + EVP_PKEY *key = NULL;
>> >>>>> + X509 *cert = NULL;
>> >>>>> + BIO *data_bio = NULL;
>> >>>>> + const EVP_MD *md;
>> >>>>> + PKCS7 *p7;
>> >>>>> + int flags, ret = -1;
>> >>>>> +
>> >>>>> + OpenSSL_add_all_digests();
>> >>>>> + OpenSSL_add_all_ciphers();
>> >>>>> + ERR_load_crypto_strings();
>> >>>>> +
>> >>>>> + key = fileio_read_pkey(ctx->key_file);
>> >>>>> + if (!key)
>> >>>>> + goto err;
>> >>>>> + cert = fileio_read_cert(ctx->cert_file);
>> >>>>> + if (!cert)
>> >>>>> + goto err;
>> >>>>> +
>> >>>>> + /*
>> >>>>> + * create a BIO, containing:
>> >>>>> + * * firmware image
>> >>>>> + * * monotonic count
>> >>>>> + * in this order!
>> >>>>> + * See EDK2's FmpAuthenticatedHandlerRsa2048Sha256()
>> >>>>> + */
>> >>>>> + data_bio = BIO_new(BIO_s_mem());
>> >>>>> + BIO_write(data_bio, ctx->image_data, ctx->image_size);
>> >>>>> + BIO_write(data_bio, &ctx->auth.monotonic_count,
>> >>>>> + sizeof(ctx->auth.monotonic_count));
>> >>>>> +
>> >>>>> + md = EVP_get_digestbyname("SHA256");
>> >>>>> + if (!md)
>> >>>>> + goto err;
>> >>>>> +
>> >>>>> + /* create signature */
>> >>>>> + /* TODO: maybe add PKCS7_NOATTR and PKCS7_NOSMIMECAP */
>> >>>>
>> >>>> PKCS7_NOATTR is a value without any documentation in the code.
>> >>>
>> >>> Nak.
>> >>> Those macros are part of openssl library. See openssl/pkcs7.h.
>> >>>
>> >>>> Please, replace variable names by a long text describing what it
>missing.
>> >>>>
>> >>>>> + flags = PKCS7_BINARY | PKCS7_DETACHED;
>> >>>>
>> >>>> Those constants lack documentation in the code.
>> >>>
>> >>> Nak again.
>> >>>
>> >>>>> + p7 = PKCS7_sign(NULL, NULL, NULL, data_bio, flags |
>PKCS7_PARTIAL);
>> >>>>> + if (!p7)
>> >>>>> + goto err;
>> >>>>> + if (!PKCS7_sign_add_signer(p7, cert, key, md, flags))
>> >>>>> + goto err;
>> >>>>> + if (!PKCS7_final(p7, data_bio, flags))
>> >>>>> + goto err;
>> >>>>> +
>> >>>>> + /* convert pkcs7 into DER */
>> >>>>> + ctx->sig_data = NULL;
>> >>>>> + ctx->sig_size = ASN1_item_i2d((ASN1_VALUE *)p7,
>&ctx->sig_data,
>> >>>>> + ASN1_ITEM_rptr(PKCS7));
>> >>>>> + if (!ctx->sig_size)
>> >>>>> + goto err;
>> >>>>> +
>> >>>>> + /* fill auth_info */
>> >>>>> + ctx->auth.auth_info.hdr.dwLength =
>sizeof(ctx->auth.auth_info)
>> >>>>> + + ctx->sig_size;
>> >>>>> + ctx->auth.auth_info.hdr.wRevision = WIN_CERT_REVISION_2_0;
>> >>>>> + ctx->auth.auth_info.hdr.wCertificateType =
>WIN_CERT_TYPE_EFI_GUID;
>> >>>>> + memcpy(&ctx->auth.auth_info.cert_type,
>&efi_guid_cert_type_pkcs7,
>> >>>>> + sizeof(efi_guid_cert_type_pkcs7));
>> >>>>> +
>> >>>>> + ret = 0;
>> >>>>> +err:
>> >>>>> + BIO_free_all(data_bio);
>> >>>>> + EVP_PKEY_free(key);
>> >>>>> + X509_free(cert);
>> >>>>> +
>> >>>>> + return ret;
>> >>>>> +}
>> >>>>> +
>> >>>>> +static int dump_signature(const char *path, u8 *signature,
>size_t sig_size)
>> >>>>> +{
>> >>>>> + char *sig_path;
>> >>>>> + FILE *f;
>> >>>>> + size_t size;
>> >>>>> + int ret = -1;
>> >>>>> +
>> >>>>> + sig_path = malloc(strlen(path) + 3 + 1);
>> >>>>> + if (!sig_path)
>> >>>>> + return ret;
>> >>>>> +
>> >>>>> + sprintf(sig_path, "%s.p7", path);
>> >>>>> + f = fopen(sig_path, "w");
>> >>>>> + if (!f)
>> >>>>> + goto err;
>> >>>>> +
>> >>>>> + size = fwrite(signature, 1, sig_size, f);
>> >>>>> + if (size == sig_size)
>> >>>>> + ret = 0;
>> >>>>> +
>> >>>>> + fclose(f);
>> >>>>> +err:
>> >>>>> + free(sig_path);
>> >>>>> + return ret;
>> >>>>> +}
>> >>>>> +#endif
>> >>>>> +
>> >>>>> static int create_fwbin(char *path, char *bin, efi_guid_t
>*guid,
>> >>>>> - unsigned long index, unsigned long
>instance)
>> >>>>> + unsigned long index, unsigned long
>instance,
>> >>>>> + uint64_t mcount, char *privkey_file, char
>*cert_file)
>> >>>>> {
>> >>>>> struct efi_capsule_header header;
>> >>>>> struct efi_firmware_management_capsule_header capsule;
>> >>>>> struct efi_firmware_management_capsule_image_header image;
>> >>>>> + struct auth_context auth_context;
>> >>>>> FILE *f, *g;
>> >>>>> struct stat bin_stat;
>> >>>>> u8 *data;
>> >>>>> @@ -266,6 +450,7 @@ static int create_fwbin(char *path, char
>*bin, efi_guid_t *guid,
>> >>>>> printf("\tbin: %s\n\ttype: %pUl\n", bin, guid);