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

AKASHI Takahiro
2021-05-13T03:08:39Z

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.

> > +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;
> > + }
> >
> > 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;
> > @@ -307,13 +526,13 @@ 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;
> > @@ -323,34 +542,61 @@ 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 IS_ENABLED(CONFIG_EFI_CAPSULE_AUTHENTICATE)
>
> We don't want to use #if if avoidable.

For this specific chunk of code, we can remove #ifdef,
but we should not remove #ifdef elsewhere.

-Takahiro Akashi

> > + 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;
> > + }
> > }
> > +#endif
> > +
> > 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);
> > +#if IS_ENABLED(CONFIG_EFI_CAPSULE_AUTHENTICATE)
> > + if (auth_context.sig_size)
> > + OPENSSL_free(auth_context.sig_data);
> > +#endif
> >
> > return 0;
> >
> > -err_3:
> > +err_4:
> > fclose(f);
> > +err_3:
> > +#if IS_ENABLED(CONFIG_EFI_CAPSULE_AUTHENTICATE)
> > + if (auth_context.sig_size)
> > + OPENSSL_free(auth_context.sig_data);
> > +#endif
> > err_2:
> > free(data);
> > err_1:
> > @@ -359,10 +605,6 @@ err_1:
> > return -1;
> > }
> >
> > -/*
> > - * Usage:
> > - * $ mkeficapsule -f <firmware binary>
> > - */
> > int main(int argc, char **argv)
> > {
> > char *file;
> > @@ -370,6 +612,8 @@ int main(int argc, char **argv)
> > char *dtb_file;
> > efi_guid_t *guid;
> > unsigned long index, instance;
> > + uint64_t mcount;
> > + char *privkey_file, *cert_file;
> > int c, idx;
> > int ret;
> > bool overlay = false;
> > @@ -380,8 +624,12 @@ int main(int argc, char **argv)
> > 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:D:K:Oh", options, &idx);
> > + c = getopt_long(argc, argv, opts_short, options, &idx);
> > if (c == -1)
> > break;
> >
> > @@ -422,6 +670,28 @@ int main(int argc, char **argv)
> > }
> > dtb_file = optarg;
> > break;
> > +#if IS_ENABLED(CONFIG_EFI_CAPSULE_AUTHENTICATE)
>
> see above
>
> Best regards
>
> Heinrich
>
> > + 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
> > case 'O':
> > overlay = true;
> > break;
> > @@ -431,8 +701,12 @@ int main(int argc, char **argv)
> > }
> > }
> >
> > - /* need a fit image file or raw image file */
> > - if (!file && !pkey_file && !dtb_file) {
> > + /* check necessary parameters */
> > + if ((file && (!(optind < argc) ||
> > + (privkey_file && !cert_file) ||
> > + (!privkey_file && cert_file))) ||
> > + ((pkey_file && !dtb_file) ||
> > + (!pkey_file && dtb_file))) {
> > print_usage();
> > exit(EXIT_FAILURE);
> > }
> > @@ -442,12 +716,12 @@ int main(int argc, char **argv)
> > if (ret == -1) {
> > printf("Adding public key to the dtb failed\n");
> > exit(EXIT_FAILURE);
> > - } else {
> > - exit(EXIT_SUCCESS);
> > }
> > }
> >
> > - if (create_fwbin(argv[optind], file, guid, index, instance)
> > + if (optind < argc &&
> > + create_fwbin(argv[optind], file, guid, index, instance,
> > + mcount, privkey_file, cert_file)
> > < 0) {
> > printf("Creating firmware capsule failed\n");
> > exit(EXIT_FAILURE);
> >
>