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

Heinrich Schuchardt
2021-05-12T08:56:41Z

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.

> +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.

> + {"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.

Please, replace variable names by a long text describing what it missing.

> + flags = PKCS7_BINARY | PKCS7_DETACHED;

Those constants lack documentation in the code.

> + 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.

> + 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);
>