[PATCH v3 1/5] tools: mkeficapsule: add firmwware image signing

Heinrich Schuchardt xypron.glpk at gmx.de
Tue Aug 31 07:53:21 CEST 2021


On 8/31/21 4:46 AM, AKASHI Takahiro wrote:
> With this enhancement, mkeficapsule will be able to sign a capsule
> file when it is created. A signature added will be used later
> in the verification at FMP's SetImage() call.
>
> To do that, We need specify additional command parameters:

nits

%s/need/need to/

>    -monotonic-cout <count> : monotonic count
>    -private-key <private key file> : private key file
>    -certificate <certificate file> : certificate file
> Only when all of those parameters are given, a signature will be added
> to a capsule file.
>
> Users are expected to maintain and increment the monotonic count at

%s/at//

> every time of the update for each firmware image.
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> ---
>   tools/Kconfig        |   7 +
>   tools/Makefile       |   8 +-
>   tools/mkeficapsule.c | 435 +++++++++++++++++++++++++++++++++++++++----
>   3 files changed, 416 insertions(+), 34 deletions(-)
>
> diff --git a/tools/Kconfig b/tools/Kconfig
> index d6f82cd949b5..9a37ed035311 100644
> --- a/tools/Kconfig
> +++ b/tools/Kconfig
> @@ -20,4 +20,11 @@ config TOOLS_LIBCRYPTO
>   	  This selection does not affect target features, such as runtime FIT
>   	  signature verification.
>
> +config TOOLS_MKEFICAPSULE
> +	bool "Build efimkcapsule command"

Having different versions of efimkcapsule with different capabilities is
very confusing for users.

Please, add

	select TOOLS_LIBCRYPTO

> +	default y if EFI_CAPSULE_ON_DISK
> +	help
> +	  This command allows users to create a UEFI capsule file and,
> +	  optionally sign that file. If you want to enable UEFI capsule
> +	  update feature on your target, you certainly need this.
>   endmenu
> diff --git a/tools/Makefile b/tools/Makefile
> index 4a86321f6467..6ea3033dbfb8 100644
> --- a/tools/Makefile
> +++ b/tools/Makefile
> @@ -237,8 +237,12 @@ hostprogs-$(CONFIG_MIPS) += mips-relocs
>   hostprogs-$(CONFIG_ASN1_COMPILER)	+= asn1_compiler
>   HOSTCFLAGS_asn1_compiler.o = -idirafter $(srctree)/include
>
> -mkeficapsule-objs	:= mkeficapsule.o $(LIBFDT_OBJS)
> -hostprogs-$(CONFIG_EFI_HAVE_CAPSULE_SUPPORT) += mkeficapsule
> +HOSTLDLIBS_mkeficapsule += -luuid
> +ifeq ($(CONFIG_TOOLS_LIBCRYPTO),y)
> +HOSTLDLIBS_mkeficapsule += \
> +	$(shell pkg-config --libs libssl libcrypto 2> /dev/null || echo "-lssl -lcrypto")
> +endif
> +hostprogs-$(CONFIG_TOOLS_MKEFICAPSULE) += mkeficapsule
>
>   # We build some files with extra pedantic flags to try to minimize things
>   # that won't build on some weird host compiler -- though there are lots of
> diff --git a/tools/mkeficapsule.c b/tools/mkeficapsule.c
> index 4995ba4e0c2a..090fb02de68d 100644
> --- a/tools/mkeficapsule.c
> +++ b/tools/mkeficapsule.c
> @@ -15,6 +15,16 @@
>   #include <sys/stat.h>
>   #include <sys/types.h>
>
> +#include <linux/kconfig.h>
> +#ifdef CONFIG_TOOLS_LIBCRYPTO
> +#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
> +
>   typedef __u8 u8;
>   typedef __u16 u16;
>   typedef __u32 u32;
> @@ -38,12 +48,25 @@ 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;
> +
> +#ifdef CONFIG_TOOLS_LIBCRYPTO
> +static const char *opts_short = "f:r:i:I:v:p:c:m:dh";
> +#else
> +static const char *opts_short = "f:r:i:I:v:h";
> +#endif
>
>   static struct option options[] = {
>   	{"fit", required_argument, NULL, 'f'},
>   	{"raw", required_argument, NULL, 'r'},
>   	{"index", required_argument, NULL, 'i'},
>   	{"instance", required_argument, NULL, 'I'},
> +#ifdef CONFIG_TOOLS_LIBCRYPTO
> +	{"private-key", required_argument, NULL, 'p'},
> +	{"certificate", required_argument, NULL, 'c'},
> +	{"monotonic-count", required_argument, NULL, 'm'},
> +	{"dump-sig", no_argument, NULL, 'd'},
> +#endif

If I get you right, you ideentified two use cases:

* unsigned capsules
* signed capsules

Should it be allowable to have unsigned capsules with some board
configurations then mkeficapsule compiled with CONFIG_TOOLS_LIBCRYPTO=y
must be able to produce unsigned capsules.

>   	{"help", no_argument, NULL, 'h'},
>   	{NULL, 0, NULL, 0},
>   };
> @@ -57,16 +80,280 @@ static void print_usage(void)
>   	       "\t-r, --raw <raw image>       new raw image file\n"
>   	       "\t-i, --index <index>         update image index\n"
>   	       "\t-I, --instance <instance>   update hardware instance\n"
> +#ifdef CONFIG_TOOLS_LIBCRYPTO
> +	       "\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-h, --help                  print a help message\n",
>   	       tool_name);
>   }
>
> +/**
> + * auth_context - authentication context
> + * @key_file:	Path to a private key file
> + * @cert_file:	Path to a certificate file
> + * @image_data:	Pointer to firmware data
> + * @image_size:	Size of firmware data
> + * @auth:	Authentication header
> + * @sig_data:	Signature data
> + * @sig_size:	Size of signature data
> + *
> + * Data structure used in create_auth_data(). @key_file through
> + * @image_size are input parameters. @auth, @sig_data and @sig_size
> + * are filled in by create_auth_data().
> + */
> +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;
> +
> +#ifdef CONFIG_TOOLS_LIBCRYPTO
> +/**
> + * fileio-read_pkey - read out a private key
> + * @filename:	Path to a private key file
> + *
> + * Read out a private key file and parse it into "EVP_PKEY" structure.
> + *
> + * Return:
> + * * Pointer to private key structure  - on success
> + * * NULL - on failure
> + */
> +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);
> +		ERR_print_errors_fp(stderr);
> +	}
> +
> +	return key;
> +}
> +
> +/**
> + * fileio-read_cert - read out a certificate
> + * @filename:	Path to a certificate file
> + *
> + * Read out a certificate file and parse it into "X509" structure.
> + *
> + * Return:
> + * * Pointer to certificate structure  - on success
> + * * NULL - on failure
> + */
> +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);
> +		ERR_print_errors_fp(stderr);
> +	}
> +
> +	return cert;
> +}
> +
> +/**
> + * create_auth_data - compose authentication data in capsule
> + * @auth_context:	Pointer to authentication context
> + *
> + * Fill up an authentication header (.auth) and signature data (.sig_data)
> + * in @auth_context, using library functions from openssl.
> + * All the parameters in @auth_context must be filled in by a caller.
> + *
> + * Return:
> + * * 0  - on success
> + * * -1 - on failure
> + */
> +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 */
> +	flags = PKCS7_BINARY | PKCS7_DETACHED;
> +	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;
> +}
> +
> +/**
> + * dump_signature - dump out a signature
> + * @path:	Path to a capsule file
> + * @signature:	Signature data
> + * @sig_size:	Size of signature data
> + *
> + * Signature data pointed to by @signature will be saved into
> + * a file whose file name is @path with ".p7" suffix.
> + *
> + * Return:
> + * * 0  - on success
> + * * -1 - on failure
> + */
> +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;
> +}
> +
> +/**
> + * free_sig_data - free out signature data
> + * @ctx:	Pointer to authentication context
> + *
> + * Free signature data allocated in create_auth_data().
> + */
> +static void free_sig_data(struct auth_context *ctx)
> +{
> +	if (ctx->sig_size)
> +		OPENSSL_free(ctx->sig_data);
> +}
> +#else
> +static int create_auth_data(struct auth_context *ctx)
> +{
> +	return 0;
> +}
> +
> +static int dump_signature(const char *path, u8 *signature, size_t sig_size)
> +{
> +	return 0;
> +}
> +
> +static void free_sig_data(struct auth_context *ctx) {}
> +#endif
> +
> +/**
> + * create_fwbin - create an uefi capsule file
> + * @path:	Path to a created capsule file
> + * @bin:	Path to a firmware binary to encapsulate
> + * @guid:	GUID of related FMP driver
> + * @index:	Index number in capsule
> + * @instance:	Instance number in capsule
> + * @mcount:	Monolitic count in authentication information
> + * @private_file:	Path to a private key file
> + * @cert_file:	Path to a certificate file
> + *
> + * This function actually does the job of creating an uefi capsule file.
> + * All the arguments must be supplied.
> + * If either @private_file ror @cert_file is NULL, the capsule file
> + * won't be signed.
> + *
> + * Return:
> + * * 0  - on success
> + * * -1 - on failure
> + */
>   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;
> @@ -76,8 +363,9 @@ static int create_fwbin(char *path, char *bin, efi_guid_t *guid,
>   #ifdef DEBUG
>   	printf("For output: %s\n", path);
>   	printf("\tbin: %s\n\ttype: %pUl\n", bin, guid);
> -	printf("\tindex: %ld\n\tinstance: %ld\n", index, instance);
> +	printf("\tindex: %lu\n\tinstance: %lu\n", index, instance);
>   #endif
> +	auth_context.sig_size = 0;
>
>   	g = fopen(bin, "r");
>   	if (!g) {
> @@ -93,11 +381,34 @@ static int create_fwbin(char *path, char *bin, efi_guid_t *guid,
>   		printf("cannot allocate memory: %zx\n", (size_t)bin_stat.st_size);
>   		goto err_1;
>   	}
> -	f = fopen(path, "w");
> -	if (!f) {
> -		printf("cannot open %s\n", path);
> +
> +	size = fread(data, 1, bin_stat.st_size, g);
> +	if (size < bin_stat.st_size) {
> +		printf("read failed (%zx)\n", size);
>   		goto err_2;
>   	}
> +
> +	/* first, calculate signature to determine its size */
> +	if (privkey_file && cert_file) {
> +		auth_context.key_file = privkey_file;
> +		auth_context.cert_file = cert_file;
> +		auth_context.auth.monotonic_count = mcount;
> +		auth_context.image_data = data;
> +		auth_context.image_size = bin_stat.st_size;
> +
> +		if (create_auth_data(&auth_context)) {
> +			printf("Signing firmware image failed\n");
> +			goto err_3;
> +		}
> +
> +		if (dump_sig &&
> +		    dump_signature(path, auth_context.sig_data,
> +				   auth_context.sig_size)) {
> +			printf("Creating signature file failed\n");
> +			goto err_3;
> +		}
> +	}
> +
>   	header.capsule_guid = efi_guid_fm_capsule;
>   	header.header_size = sizeof(header);
>   	/* TODO: The current implementation ignores flags */
> @@ -106,11 +417,20 @@ static int create_fwbin(char *path, char *bin, efi_guid_t *guid,
>   					+ sizeof(capsule) + sizeof(u64)
>   					+ sizeof(image)
>   					+ bin_stat.st_size;
> +	if (auth_context.sig_size)
> +		header.capsule_image_size += sizeof(auth_context.auth)
> +				+ auth_context.sig_size;
> +
> +	f = fopen(path, "w");
> +	if (!f) {
> +		printf("cannot open %s\n", path);
> +		goto err_3;
> +	}
>
>   	size = fwrite(&header, 1, sizeof(header), f);
>   	if (size < sizeof(header)) {
>   		printf("write failed (%zx)\n", size);
> -		goto err_3;
> +		goto err_4;
>   	}
>
>   	capsule.version = 0x00000001;
> @@ -119,13 +439,13 @@ static int create_fwbin(char *path, char *bin, efi_guid_t *guid,
>   	size = fwrite(&capsule, 1, sizeof(capsule), f);
>   	if (size < (sizeof(capsule))) {
>   		printf("write failed (%zx)\n", size);
> -		goto err_3;
> +		goto err_4;
>   	}
>   	offset = sizeof(capsule) + sizeof(u64);
>   	size = fwrite(&offset, 1, sizeof(offset), f);
>   	if (size < sizeof(offset)) {
>   		printf("write failed (%zx)\n", size);
> -		goto err_3;
> +		goto err_4;
>   	}
>
>   	image.version = 0x00000003;
> @@ -135,34 +455,53 @@ static int create_fwbin(char *path, char *bin, efi_guid_t *guid,
>   	image.reserved[1] = 0;
>   	image.reserved[2] = 0;
>   	image.update_image_size = bin_stat.st_size;
> +	if (auth_context.sig_size)
> +		image.update_image_size += sizeof(auth_context.auth)
> +				+ auth_context.sig_size;
>   	image.update_vendor_code_size = 0; /* none */
>   	image.update_hardware_instance = instance;
>   	image.image_capsule_support = 0;
> +	if (auth_context.sig_size)
> +		image.image_capsule_support |= CAPSULE_SUPPORT_AUTHENTICATION;
>
>   	size = fwrite(&image, 1, sizeof(image), f);
>   	if (size < sizeof(image)) {
>   		printf("write failed (%zx)\n", size);
> -		goto err_3;
> +		goto err_4;
>   	}
> -	size = fread(data, 1, bin_stat.st_size, g);
> -	if (size < bin_stat.st_size) {
> -		printf("read failed (%zx)\n", size);
> -		goto err_3;
> +
> +	if (auth_context.sig_size) {
> +		size = fwrite(&auth_context.auth, 1,
> +			      sizeof(auth_context.auth), f);
> +		if (size < sizeof(auth_context.auth)) {
> +			printf("write failed (%zx)\n", size);
> +			goto err_4;
> +		}
> +		size = fwrite(auth_context.sig_data, 1,
> +			      auth_context.sig_size, f);
> +		if (size < auth_context.sig_size) {
> +			printf("write failed (%zx)\n", size);
> +			goto err_4;
> +		}
>   	}
> +
>   	size = fwrite(data, 1, bin_stat.st_size, f);
>   	if (size < bin_stat.st_size) {
>   		printf("write failed (%zx)\n", size);
> -		goto err_3;
> +		goto err_4;
>   	}
>
>   	fclose(f);
>   	fclose(g);
>   	free(data);
> +	free_sig_data(&auth_context);
>
>   	return 0;
>
> -err_3:
> +err_4:
>   	fclose(f);
> +err_3:
> +	free_sig_data(&auth_context);
>   err_2:
>   	free(data);
>   err_1:
> @@ -171,23 +510,37 @@ err_1:
>   	return -1;
>   }
>
> -/*
> - * Usage:
> - *   $ mkeficapsule -f <firmware binary> <output file>
> +/**
> + * main - main entry function of mkeficapsule
> + * @argc:	Number of arguments
> + * @argv:	Array of pointers to arguments
> + *
> + * Create an uefi capsule file, optionally signing it.
> + * Parse all the arguments and pass them on to create_fwbin().
> + *
> + * Return:
> + * * 0  - on success
> + * * -1 - on failure
>    */
>   int main(int argc, char **argv)
>   {
>   	char *file;
>   	efi_guid_t *guid;
>   	unsigned long index, instance;
> +	uint64_t mcount;
> +	char *privkey_file, *cert_file;
>   	int c, idx;
>
>   	file = NULL;
>   	guid = NULL;
>   	index = 0;
>   	instance = 0;
> +	mcount = 0;
> +	privkey_file = NULL;
> +	cert_file = NULL;
> +	dump_sig = 0;
>   	for (;;) {
> -		c = getopt_long(argc, argv, "f:r:i:I:v:h", options, &idx);
> +		c = getopt_long(argc, argv, opts_short, options, &idx);
>   		if (c == -1)
>   			break;
>
> @@ -214,29 +567,47 @@ int main(int argc, char **argv)
>   		case 'I':
>   			instance = strtoul(optarg, NULL, 0);
>   			break;
> +#ifdef CONFIG_TOOLS_LIBCRYPTO
> +		case 'p':
> +			if (privkey_file) {
> +				printf("Private Key already specified\n");
> +				return -1;
> +			}
> +			privkey_file = optarg;
> +			break;
> +		case 'c':
> +			if (cert_file) {
> +				printf("Certificate file already specified\n");
> +				return -1;
> +			}
> +			cert_file = optarg;
> +			break;
> +		case 'm':
> +			mcount = strtoul(optarg, NULL, 0);
> +			break;
> +		case 'd':
> +			dump_sig = 1;
> +			break;
> +#endif /* CONFIG_TOOLS_LIBCRYPTO */
>   		case 'h':
>   			print_usage();
>   			return 0;
>   		}
>   	}
>
> -	/* need an output file */
> -	if (argc != optind + 1) {
> -		print_usage();
> -		exit(EXIT_FAILURE);
> -	}
> -
> -	/* need a fit image file or raw image file */
> -	if (!file) {
> +	/* check necessary parameters */
> +	if ((argc != optind + 1) || !file ||

This needs to be changed to support signed and unsigned capsules.

> +	    ((privkey_file && !cert_file) ||
> +	     (!privkey_file && cert_file))) {
>   		print_usage();
> -		exit(EXIT_SUCCESS);
> +		return -1;

Please use EXIT_FALURE.

>   	}
>
> -	if (create_fwbin(argv[optind], file, guid, index, instance)
> -			< 0) {
> +	if (create_fwbin(argv[optind], file, guid, index, instance,
> +			 mcount, privkey_file, cert_file) < 0) {
>   		printf("Creating firmware capsule failed\n");
> -		exit(EXIT_FAILURE);
> +		return -1;

return EXIT_FAILURE;

>   	}
>
> -	exit(EXIT_SUCCESS);
> +	return 0;

In main, please, use

	return EXIT_SUCCESS;

Best regards

Heinrich

>   }
>



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