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verifiers: Add possibility to defer verification to other verifiers

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This way if a verifier requires verification of a given file it can defer task
to another verifier (another authority) if it is not able to do it itself. E.g.
shim_lock verifier, posted as a subsequent patch, is able to verify only PE
files. This means that it is not able to verify any of GRUB2 modules which have
to be trusted on UEFI systems with secure boot enabled. So, it can defer
verification to other verifier, e.g. PGP one.

I silently assume that other verifiers are trusted and will do good job for us.
Or at least they will not do any harm.

Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Ross Philipson <ross.philipson@oracle.com>
This commit is contained in:
Daniel Kiper 2018-09-26 13:17:52 +02:00
parent 4d4a8c96e3
commit 5b8d535395
2 changed files with 23 additions and 4 deletions
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23
grub-core/commands/verifiers.c
View file

@ -83,6 +83,7 @@ grub_verifiers_open (grub_file_t io, enum grub_file_type type)
void *context;
grub_file_t ret = 0;
grub_err_t err;
int defer = 0;
grub_dprintf ("verify", "file: %s type: %d\n", io->name, type);
@ -102,13 +103,27 @@ grub_verifiers_open (grub_file_t io, enum grub_file_type type)
err = ver->init (io, type, &context, &flags);
if (err)
goto fail_noclose;
if (flags & GRUB_VERIFY_FLAGS_DEFER_AUTH)
{
defer = 1;
continue;
}
if (!(flags & GRUB_VERIFY_FLAGS_SKIP_VERIFICATION))
break;
}
if (!ver)
/* No verifiers wanted to verify. Just return underlying file. */
return io;
{
if (defer)
{
grub_error (GRUB_ERR_ACCESS_DENIED,
N_("verification requested but nobody cares: %s"), io->name);
goto fail_noclose;
}
/* No verifiers wanted to verify. Just return underlying file. */
return io;
}
ret = grub_malloc (sizeof (*ret));
if (!ret)
@ -160,7 +175,9 @@ grub_verifiers_open (grub_file_t io, enum grub_file_type type)
err = ver->init (io, type, &context, &flags);
if (err)
goto fail_noclose;
if (flags & GRUB_VERIFY_FLAGS_SKIP_VERIFICATION)
if (flags & GRUB_VERIFY_FLAGS_SKIP_VERIFICATION ||
/* Verification done earlier. So, we are happy here. */
flags & GRUB_VERIFY_FLAGS_DEFER_AUTH)
continue;
err = ver->write (context, verified->buf, ret->size);
if (err)

4
include/grub/verify.h
View file

@ -22,7 +22,9 @@
enum grub_verify_flags
{
GRUB_VERIFY_FLAGS_SKIP_VERIFICATION = 1,
GRUB_VERIFY_FLAGS_SINGLE_CHUNK = 2
GRUB_VERIFY_FLAGS_SINGLE_CHUNK = 2,
/* Defer verification to another authority. */
GRUB_VERIFY_FLAGS_DEFER_AUTH = 4
};
enum grub_verify_string_type