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

[Heinrich Schuchardt <xypron.glpk@gmx.de>]

Am 13. Mai 2021 08:36:05 MESZ schrieb AKASHI Takahiro <takahiro.akashi@linaro.org>:
>On Thu, May 13, 2021 at 07:35:36AM +0200, Heinrich Schuchardt wrote:
>> On 5/13/21 7:00 AM, AKASHI Takahiro wrote:
>> > On Thu, May 13, 2021 at 06:22:39AM +0200, Heinrich Schuchardt
>wrote:
>> > > 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).
>> > > 
>> > > 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.
>> > 
>> > That is why I proposed that we create a new kconfig option.
>> 
>> What do you want to configure? Signing shall always be enabled in
>> mkeficapsule.
>
>I don't think so.

Capsule updates without authentication should never be rolled out in production for security reasons.

>
>> > 
>> > Please note that enabling signing feature in mkeficapsule
>> > requires openssl library, and we should not enforce users who don't
>> > need this feature to install an unnecessary package.
>> 
>> Why? There are dozens of other packages depending on OpenSSL on a
>> developer's machine.
>
>We don't expect all users have openssl-related packages on their
>desktop.

We are not talking about users but developers here.

I haven't seen a Linux distro without an OpenSSL package. The package management system will pull it in when u-boot-tools is installed.

Best regards

Heinrich

>
>-Takahiro Akashi
>
>
>> Best regards
>> 
>> Heinrich
>> 
>> > 
>> > -Takahiro Akashi
>> > 
>> > > 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);
>> > > > > >    	printf("\tindex: %ld\n\tinstance: %ld\n", index,
>instance);
>> > > > > >    #endif
>> > > > > > +	auth_context.sig_size = 0;
>> > > > > > 
>> > > > > >    	g = fopen(bin, "r");
>> > > > > >    	if (!g) {
>> > > > > > @@ -281,11 +466,36 @@ 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 IS_ENABLED(CONFIG_EFI_CAPSULE_AUTHENTICATE)
>> > > > > 
>> > > > > see above
>> > > > > 
>> > > > > > +	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;
>> > > > > > +		}
>> > > > > > +	}
>> > > > > > +#endif
>> > > > > > +
>> > > > > >    	header.capsule_guid = efi_guid_fm_capsule;
>> > > > > >    	header.header_size = sizeof(header);
>> > > > > >    	/* TODO: The current implementation ignores flags */
>> > > > > > @@ -294,11 +504,20 @@ 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;