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

AKASHI Takahiro
2021-05-13T07:23:59Z

On Thu, May 13, 2021 at 08:55:17AM +0200, Heinrich Schuchardt wrote:
> Am 13. Mai 2021 08:50:54 MESZ schrieb AKASHI Takahiro <takahiro.akashi@linaro.org>:
> >On Thu, May 13, 2021 at 07:50:52AM +0200, Heinrich Schuchardt wrote:
> >> On 5/13/21 7:12 AM, Masami Hiramatsu wrote:
> >> > Hi Heinrich,
> >> >
> >> > 2021?5?13?(?) 13:22 Heinrich Schuchardt <xypron.glpk@gmx.de>:
> >> > >
> >> > > 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).
> >> >
> >> > I couldn't catch your point. If so, the distros can build u-boot
> >with
> >> > CONFIG_EFI_CAPSULE_AUTHENTICATE=y...
> >>
> >> Why should the tool depend on board configuration?
> >> Who would want capsule updates without authentication?
> >
> >I believe that there are bunch of users who don't need authentication
> >on their own systems.
> >
>
> They should think again.

Why?

> >> >
> >> > BTW, IMHO, if u-boot.bin can not find the ESL in the device tree,
> >> > it should skip authentication too.
> >>
> >> In this case the capsule should be rejected (if
> >> CONFIG_EFI_CAPSULE_AUTHENTICATE=y).
> >
> >That's basically right.
> >But as I mentioned in my comment against Sughosh's patch,
> >the authentication process will be enforced only if the capsule has
> >an attribute, IMAGE_ATTRIBUTE_AUTHENTICATION_REQUIRED.
> >
>
> That would be a security desaster.

The requirement that I mentioned above is clearly described
in UEFI specification.
If you think that it is a disaster, please discuss the topic
in UEFI Forum first.

-Takahiro Akashi

> Best regards
>
> Heinrich
>
> >I believe that this flag should be able to be specified and managed
> >outside U-Boot configuration.
> >So there can be a case where FW update is performed even if
> >the key/certificate is not found in the device tree.
> >
> >> >
> >> > Then, user can choose whether enabling capsule authentication or
> >not
> >> > by embedding ESL into their devicetree.
> >
> >Same comment above.
> >
> >-Takahiro Akashi
> >
> >> The user shall not be able to decide anything that might hamper
> >> security. The U-Boot binary must dictate if a capsule is safe.
> >>
> >> Best regards
> >>
> >> Heinrich
> >>
> >> >
> >> > Thank you
> >> >
> >> > >
> >> > > 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.
> >> > >
> >> > > 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)) {
>