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

AKASHI Takahiro
2021-05-12T04:57:50Z

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")
+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)
+#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)
+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'},
+ {"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)
+ "\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)
+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;
+}
+
+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;
+}
+
+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;
+}
+
+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)
+ 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)
+ 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)
+ 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);
--
2.31.0