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

Sughosh Ganu
2022-06-16T07:12:29Z

hi Takahiro,

On Thu, 16 Jun 2022 at 06:31, Takahiro Akashi
<takahiro.akashi@linaro.org> wrote:
>
> Sughosh,
>
> On Wed, Jun 15, 2022 at 04:19:56PM +0530, Sughosh Ganu wrote:
> > On Wed, 15 Jun 2022 at 10:41, Takahiro Akashi
> > <takahiro.akashi@linaro.org> wrote:
> > >
> > > On Thu, Jun 09, 2022 at 05:59:58PM +0530, 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(-)
> > > >
> > > > diff --git a/doc/mkeficapsule.1 b/doc/mkeficapsule.1
> > > > index 09bdc24295..77ca061efd 100644
> > > > --- a/doc/mkeficapsule.1
> > > > +++ b/doc/mkeficapsule.1
> > > > @@ -8,7 +8,7 @@ mkeficapsule \- Generate EFI capsule file for U-Boot
> > > >
> > > > .SH SYNOPSIS
> > > > .B mkeficapsule
> > > > -.RI [ options "] " image-blob " " capsule-file
> > > > +.RI [ options ] " " [ image-blob ] " " capsule-file
> > > >
> > > > .SH "DESCRIPTION"
> > > > .B mkeficapsule
> > > > @@ -23,8 +23,13 @@ Optionally, a capsule file can be signed with a given private key.
> > > > In this case, the update will be authenticated by verifying the signature
> > > > before applying.
> > > >
> > > > +Additionally, an empty capsule file can be generated for acceptance or
> > > > +rejection of firmware images by a governing component like an Operating
> > > > +System. The empty capsules do not require an image-blob input file.
> > > > +
> > > > +
> > > > .B mkeficapsule
> > > > -takes any type of image files, including:
> > > > +takes any type of image files when generating non empty capsules, including:
> > > > .TP
> > > > .I raw image
> > > > format is a single binary blob of any type of firmware.
> > > > @@ -36,18 +41,16 @@ multiple binary blobs in a single capsule file.
> > > > This type of image file can be generated by
> > > > .BR mkimage .
> > > >
> > > > -.PP
> > > > -If you want to use other types than above two, you should explicitly
> > > > -specify a guid for the FMP driver.
> > > > -
> > > > .SH "OPTIONS"
> > > > +
> > > > .TP
> > > > .BI "-g\fR,\fB --guid " guid-string
> > > > Specify guid for image blob type. The format is:
> > > > xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
> > > >
> > > > The first three elements are in little endian, while the rest
> > > > -is in big endian.
> > > > +is in big endian. The option must be specified for all non empty and
> > > > +image acceptance capsules
> > >
> > > "image acceptance" -> "firmware acceptance"
> >
> > Okay
> >
> > >
> > > I don't still understand why we need a guid for acceptance
> > > while revert doesn't require it.
> > > I believe that firmware update is "all or nothing", isn't it?
> >
> > I believe this gives more flexibility in that different components
> > might be required to accept the various firmware images. So, one
> > component might accept the optee_os, while another might be
> > responsible for accepting u-boot. In any case, we do check that all
> > the components have their accepted bit set, and only if so, does the
> > bank boot in the regular state.
>
> Probably I don't understand the behavior.
> Let's assume that we have firmware A and firmware B and then
> update both.
> When the firmware A is accepted and B is not (not yet issuing
> acceptance capsule) and I try to reboot the system, what happens?
> From which bank does the system boot, old one or new one?

Once any/all of the images have been updated, on subsequent reboot,
the platform would boot in Trial State from the updated bank. I have
introduced an EFI variable, TrialeStateCtr for counting the number of
times the system is booting in the trial state. The system remains in
trial state as long as all the images from the updated bank have not
been accepted. The platform boots in trial state for a particular
number of iterations(configurable), and once that count has exceeded,
the active bank value gets changed to the previous_active_index, and
the platform subsequently boots from the other bank. If all the images
do get accepted while the platform is in trial state, the platform
transitions to the regular state, and continues booting from that
bank.

-sughosh

>
> > In case of a firmware revert, it would
> > not matter which firmware component is being reverted -- the platform
> > would simply need to boot from the other bank. Do you see any issue
> > with the current method that we have?
> >
> > >
> > > If there is a good reason, please describe a possible/expected
> > > scenario.
> >
> > Where do you want me to explain this, in the feature documentation? Or
> > do you think this can be elaborated in greater detail in the spec.
>
> I prefer some explanation in U-Boot doc.
>
> > >
> > > > .TP
> > > > .BI "-i\fR,\fB --index " index
> > > > @@ -57,6 +60,18 @@ Specify an image index
> > > > .BI "-I\fR,\fB --instance " instance
> > > > Specify a hardware instance
> > > >
> > > > +.PP
> > > > +For generation of firmware accept empty capsule
> > > > +.BR --guid
> > > > +is mandatory
> > > > +.TP
> > > > +.BI "-A\fR,\fB --fw-accept "
> > > > +Generate a firmware acceptance empty capsule
> > > > +
> > > > +.TP
> > > > +.BI "-R\fR,\fB --fw-revert "
> > > > +Generate a firmware revert empty capsule
> > > > +
> > > > .TP
> > > > .BR -h ", " --help
> > > > Print a help message
> > > > diff --git a/tools/eficapsule.h b/tools/eficapsule.h
> > > > index d63b831443..072a4b5598 100644
> > > > --- a/tools/eficapsule.h
> > > > +++ b/tools/eficapsule.h
> > > > @@ -41,6 +41,14 @@ typedef struct {
> > > > EFI_GUID(0x4aafd29d, 0x68df, 0x49ee, 0x8a, 0xa9, \
> > > > 0x34, 0x7d, 0x37, 0x56, 0x65, 0xa7)
> > > >
> > > > +#define FW_ACCEPT_OS_GUID \
> > > > + EFI_GUID(0x0c996046, 0xbcc0, 0x4d04, 0x85, 0xec, \
> > > > + 0xe1, 0xfc, 0xed, 0xf1, 0xc6, 0xf8)
> > > > +
> > > > +#define FW_REVERT_OS_GUID \
> > > > + EFI_GUID(0xacd58b4b, 0xc0e8, 0x475f, 0x99, 0xb5, \
> > > > + 0x6b, 0x3f, 0x7e, 0x07, 0xaa, 0xf0)
> > > > +
> > > > /* flags */
> > > > #define CAPSULE_FLAGS_PERSIST_ACROSS_RESET 0x00010000
> > > >
> > > > 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",
> > > > + 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-R, --fw-revert firmware revert capsule\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));
> > >
> > > -> guidcpy()
> >
> > This being a host tool, guidcpy cannot be used. You have used memcpy
> > in the create_fwbin() for the same reason I guess.
>
> Ah, right.
>
> > >
> > > > + 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));
> > >
> > > ditto
> >
> > Same as above.
> >
> > >
> > > > + 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':
> > > > 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);
> > > > +
> > >
> > > So empty_capsule is redundant as empty_capsule is equivalent with
> > > "capsule == CAPSULE_NORMAL_BLOB".
> > > I think that a single variable, say capsule_type, is enough.
> >
> > I was using empty_capsule primarily to make the check done below look
> > more succinct and readable. But I can change that to capsule !=
> > CAPSULE_NORMAL_BLOB.
> >
> > >
> > > > /* 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)))) {
> > > > 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) {
> > >
> > > if (capsule_type != CAPSULE_NORMAL_BLOB)
> > > create_empty_capsule(..., capsule_type == CAPSULE_ACCEPT);
> > >
> > > Simple is the best :)
> >
> > Common, please don't tell me that the code above is complicated. Just
> > that we can do without the empty_capsule variable, yes.
>
> Sorry, not complicated, but having two variables make little sense.
>
> -Takahiro Akashi
>
> > -sughosh
> >
> > >
> > > -Takahiro Akashi
> > > > + fprintf(stderr, "Creating empty capsule failed\n");
> > > > + 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);
> > > > }
> > > > --
> > > > 2.25.1
> > > >