Re: [PATCH v5 11/23] mkeficapsule: Add support for generating empty capsules

Sughosh Ganu
2022-06-13T12:33:58Z

On Thu, 9 Jun 2022 at 21:58, Heinrich Schuchardt <xypron.glpk@gmx.de> wrote:
>
> On 6/9/22 14:29, Sughosh Ganu wrote:
> > The Dependable Boot specification[1] describes the structure of the
> > firmware accept and revert capsules. These are empty capsules which
> > are used for signalling the acceptance or rejection of the updated
> > firmware by the OS. Add support for generating these empty capsules.
> >
> > [1] - https://git.codelinaro.org/linaro/dependable-boot/mbfw/uploads/6f7ddfe3be24e18d4319e108a758d02e/mbfw.pdf
> >
> > Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
> > ---
> > doc/mkeficapsule.1 | 29 ++++++---
> > tools/eficapsule.h | 8 +++
> > tools/mkeficapsule.c | 139 +++++++++++++++++++++++++++++++++++++------
> > 3 files changed, 151 insertions(+), 25 deletions(-)

<snip>

> > diff --git a/tools/mkeficapsule.c b/tools/mkeficapsule.c
> > index 5f74d23b9e..e8eb6b070d 100644
> > --- a/tools/mkeficapsule.c
> > +++ b/tools/mkeficapsule.c
> > @@ -29,7 +29,16 @@ static const char *tool_name = "mkeficapsule";
> > efi_guid_t efi_guid_fm_capsule = EFI_FIRMWARE_MANAGEMENT_CAPSULE_ID_GUID;
> > efi_guid_t efi_guid_cert_type_pkcs7 = EFI_CERT_TYPE_PKCS7_GUID;
> >
> > -static const char *opts_short = "g:i:I:v:p:c:m:dh";
> > +static const char *opts_short = "g:i:I:v:p:c:m:dhAR";
> > +
> > +static bool empty_capsule;
> > +static unsigned char capsule;
> > +
> > +enum {
> > + CAPSULE_NORMAL_BLOB = 0,
> > + CAPSULE_ACCEPT,
> > + CAPSULE_REVERT,
> > +} capsule_type;
> >
> > static struct option options[] = {
> > {"guid", required_argument, NULL, 'g'},
> > @@ -39,24 +48,47 @@ static struct option options[] = {
> > {"certificate", required_argument, NULL, 'c'},
> > {"monotonic-count", required_argument, NULL, 'm'},
> > {"dump-sig", no_argument, NULL, 'd'},
> > + {"fw-accept", no_argument, NULL, 'A'},
> > + {"fw-revert", no_argument, NULL, 'R'},
> > {"help", no_argument, NULL, 'h'},
> > {NULL, 0, NULL, 0},
> > };
> >
> > static void print_usage(void)
> > {
> > - fprintf(stderr, "Usage: %s [options] <image blob> \n"
> > - "Options:\n"
> > -
> > - "\t-g, --guid <guid string> guid for image blob type\n"
> > - "\t-i, --index <index> update image index\n"
> > - "\t-I, --instance <instance> update hardware instance\n"
> > - "\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"
> > - "\t-h, --help print a help message\n",
> > - tool_name);
> > + if (empty_capsule) {
> > + if (capsule == CAPSULE_ACCEPT) {
> > + fprintf(stderr, "Usage: %s [options] \n",
>
> My expectation is that this function always provides the same output.
>
> If different scenarios allow only specific combinations of arguments you
> may describe it here.

Okay

>
>
> > + tool_name);
> > + fprintf(stderr, "Options:\n"
> > + "\t-A, --fw-accept firmware accept capsule\n"
> > + "\t-g, --guid <guid string> guid for image blob type\n"
> > + "\t-h, --help print a help message\n"
> > + );
> > + } else {
> > + fprintf(stderr, "Usage: %s [options] \n",
> > + tool_name);
> > + fprintf(stderr, "Options:\n"
> > + "\t-R, --fw-revert firmware revert capsule\n"
> > + "\t-h, --help print a help message\n"
> > + );
> > + }
> > + } else {
> > + fprintf(stderr, "Usage: %s [options] <image blob> \n"
> > + "Options:\n"
> > +
> > + "\t-g, --guid <guid string> guid for image blob type\n"
> > + "\t-i, --index <index> update image index\n"
> > + "\t-I, --instance <instance> update hardware instance\n"
> > + "\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"
> > + "\t-A, --fw-accept firmware accept capsule\n"
>
> "\t-A, --fw-accept firmware accept capsule, requires GUID\n"
>
> > + "\t-R, --fw-revert firmware revert capsule\n"
>
> "\t-R, --fw-revert firmware revert capsule, takes no GUID\n"
>
> > + "\t-h, --help print a help message\n",
> > + tool_name);
> > + }
> > }
> >
> > /**
> > @@ -564,6 +596,50 @@ void convert_uuid_to_guid(unsigned char *buf)
> > buf[7] = c;
> > }
> >
> > +static int create_empty_capsule(char *path, efi_guid_t *guid, bool fw_accept)
> > +{
> > + struct efi_capsule_header header;
> > + FILE *f = NULL;
> > + int ret = -1;
> > + efi_guid_t fw_accept_guid = FW_ACCEPT_OS_GUID;
> > + efi_guid_t fw_revert_guid = FW_REVERT_OS_GUID;
> > + efi_guid_t payload, capsule_guid;
> > +
> > + f = fopen(path, "w");
> > + if (!f) {
> > + fprintf(stderr, "cannot open %s\n", path);
> > + goto err;
> > + }
> > +
> > + capsule_guid = fw_accept ? fw_accept_guid : fw_revert_guid;
> > +
> > + memcpy(&header.capsule_guid, &capsule_guid, sizeof(efi_guid_t));
> > + header.header_size = sizeof(header);
> > + header.flags = 0;
> > +
> > + header.capsule_image_size = fw_accept ?
> > + sizeof(header) + sizeof(efi_guid_t) : sizeof(header);
> > +
> > + if (write_capsule_file(f, &header, sizeof(header),
> > + "Capsule header"))
> > + goto err;
> > +
> > + if (fw_accept) {
> > + memcpy(&payload, guid, sizeof(efi_guid_t));
> > + if (write_capsule_file(f, &payload, sizeof(payload),
> > + "FW Accept Capsule Payload"))
> > + goto err;
> > + }
> > +
> > + ret = 0;
> > +
> > +err:
> > + if (f)
> > + fclose(f);
> > +
> > + return ret;
> > +}
> > +
> > /**
> > * main - main entry function of mkeficapsule
> > * @argc: Number of arguments
> > @@ -639,22 +715,49 @@ int main(int argc, char **argv)
>
> > case 'd':
> > dump_sig = 1;
> > break;
> > + case 'A':
> > + capsule |= CAPSULE_ACCEPT;
> > + break;
> > + case 'R':
> > + capsule |= CAPSULE_REVERT;
> > + break;
> > case 'h':
>
> You must handle '?' and ':' here too. Just use
>
> default:

Okay

>
>
> > print_usage();
> > exit(EXIT_SUCCESS);
> > }
> > }
> >
> > + if (capsule == (CAPSULE_ACCEPT | CAPSULE_REVERT)) {
> > + fprintf(stderr,
> > + "Select either of Accept or Revert capsule generation\n");
> > + exit(EXIT_FAILURE);
> > + }
> > +
> > + empty_capsule = (capsule == CAPSULE_ACCEPT ||
> > + capsule == CAPSULE_REVERT);
> > +
> > /* check necessary parameters */
> > - if ((argc != optind + 2) || !guid ||
> > - ((privkey_file && !cert_file) ||
> > - (!privkey_file && cert_file))) {
> > + if ((!empty_capsule &&
> > + ((argc != optind + 2) || !guid ||
> > + ((privkey_file && !cert_file) ||
> > + (!privkey_file && cert_file)))) ||
> > + (empty_capsule &&
> > + ((argc != optind + 1) ||
> > + ((capsule == CAPSULE_ACCEPT) && !guid) ||
> > + ((capsule == CAPSULE_REVERT) && guid)))) {
>
> Please, write a message explaining to the user what was wrong, e.g.
>
> "Option -A does not take a GUID" or
> "Option -R requires a GUID"

We are calling the print_usage function where I am adding the
additional information that you suggested above. I think that would
suffice. Else we are basically repeating the same information twice.

>
>
> > print_usage();
> > exit(EXIT_FAILURE);
> > }
> >
> > - if (create_fwbin(argv[argc - 1], argv[argc - 2], guid, index, instance,
> > - mcount, privkey_file, cert_file) < 0) {
> > + if (empty_capsule) {
> > + if (create_empty_capsule(argv[argc - 1], guid,
> > + capsule == CAPSULE_ACCEPT) < 0) {
> > + fprintf(stderr, "Creating empty capsule failed\n");
>
> The called function should provide a message that describes what went wrong.

The create_empty_capsule function calls the write_capsule_file
function for creation of the capsule file, and passes the string that
is to be printed in case of an error condition.

-sughosh

>
> Best regards
>
> Heinrich
>
>
> > + exit(EXIT_FAILURE);
> > + }
> > + } else if (create_fwbin(argv[argc - 1], argv[argc - 2], guid,
> > + index, instance, mcount, privkey_file,
> > + cert_file) < 0) {
> > fprintf(stderr, "Creating firmware capsule failed\n");
> > exit(EXIT_FAILURE);
> > }
>