Under a strict memory protection policy, UEFI may give out EfiLoaderData
memory with the XN attribute set. So use EfiLoaderCode explicitly.
At the same time, use a page based allocation rather than a pool
allocation, which is more appropriate when loading PE/COFF images.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Previously we were returning EFI_ACCESS_DENIED at some places and
EFI_SECURITY_VIOLATION at others. When we're checking whether to run
MokManager, we're checking EFI_SECURITY_VIOLATION, which is more or less
analogous with what the spec says StartImage() returns. So we should
always have that as the return code.
I believe this will fix github issue #44.
Signed-off-by: Peter Jones <pjones@redhat.com>
Some machines have already embedded MokSBStateRT varaible with
EFI_VARIABLE_NON_VOLATILE attribute, and some users might disable shim
vailidation manually by creating MokSBStateRT. It causes mirroring MokSBState
fail because the variable cannot be set with different attribute again, and gets
error massage every time when booting.
Fix it with checking the MokSBStateRT existence and deleting it before
mirroring it.
Signed-off-by: Ivan Hu <ivan.hu@canonical.com>
Currently generate_hash() attempts to include any trailing data at the
end of the binary in the resulting digest, but it won't include such
data if the size computed is wrong because context->SecDir->Size is
invalid. In this case the return code is EFI_SUCCESS, and the hash will
match any a binary as if the Attribute Certificate Table and anything
after it are missing. This is wrong.
Signed-off-by: Peter Jones <pjones@redhat.com>
For starters; don't allow the "module signing" OID; which ought to
only ever be used for signing kernel modules, not signing EFI binaries.
Signed-off-by: Mathieu Trudel-Lapierre <mathieu.trudel-lapierre@canonical.com>
Authenticode Certificate length is available in Certificate Table
(inside PE header) and also in signature header(WIN_CERTIFICATE) itself.
Code in 'check_backlist()' method uses length from signature header,
whereas, AuthenticodeVerify() call inside 'verify_buffer()' method uses
the length in signature header. This causes a security vulnerability issue :
Good Scenario : Assume shim1.crt is used for signing grub.efi and
shim1.crt is embedded inside shim.efi. Also, assume shim1.crt got
compromised and therefore it was added in 'dbx' database. Now, when
shim.efi will attempt to load grub.efi, it will fail loading with
log message "Binary is blacklisted" because 'check_blacklist' call
will detect the presence of 'shim1.crt' in 'dbx'.
Vulnerable Scenario : Similar as above. Add 'shim1.crt' in dbx database.
Also, tamper the earlier signed grub.efi file by placing 0x0000 in the
WIN_CERTIFICATE.dwLength.
(Open grub.efi/vmlinuz signed binary with hex editor.
Go to 0x128 address and read out the address from 0x128 until
0x12B in little Indian order from right to left.
Jump to the address from 0x128 address area.
First 8bytes are the signature header area which consist of
signature size(4bytes), revision(2bytes) and type(2bytes).
So tamper the first 4 bytes for signature size and save the binary.
)
With this tampered grub.efi, shim.efi loads it successfully because
'check_blacklist()' call fails to detect the presence of shim1.crt in 'dbx'
database.
Signed-off-by: Sachin Agrawal <sachin.agrawal@intel.com>
When fallback.efi is not present, the should_use_fallback error path
attempts to close a file that has already been closed, resulting in a
hang. This issue only affects certain systems.
This is a regression from version 0.8 and was introduced by commit
4794822.
Signed-off-by: Benjamin Antin <ben.antin@endlessm.com>
Fix the compilation error from gcc:
shim.c: In function ‘handle_image’:
shim.c:1121:15: error: unused variable ‘size’ [-Werror=unused-variable]
unsigned int size;
^~~~
Signed-off-by: Gary Lin <glin@suse.com>
This commit adds the basic support for HTTPBoot, i.e. to fetch
the next stage loader with the HTTP protocol.
It requires gnu-efi >= 3.0.3 to support the URI device path and
Ip4Config2 or Ip6Config protocol support in the UEFI implementation.
To build shim.efi with HTTPBoot support:
make ENABLE_HTTPBOOT=1 shim.efi
Signed-off-by: Gary Ching-Pang Lin <glin@suse.com>
On baytrail, we've got 32-bit firmware, 32-bit efi utilities, and 64-bit
kernel. So since most distros will want 32+64 EFI media booting a
64-bit kernel, we have to name them better on the filesystem.
Signed-off-by: Peter Jones <pjones@redhat.com>
Add support for measuring the MOK database and secure boot state into a
TPM, and do the same for the second stage loader. This avoids a hole in
TPM measurement between the firmware and the second stage loader.
The second stage set is not working after commit
3322257e61 for those which load option
only have one string.
Signed-off-by: Ivan Hu <ivan.hu@canonical.com>
I found a machine whose BDS gives us relative paths, yay! The rest of
the code still works without that leading slash, so just make it one
more item we let through our StrnCaseCmp() filter.
Signed-off-by: Peter Jones <pjones@redhat.com>
ExitBootServices() and Exit() should both clean these up anyway, but we
should do the right thing nonetheless.
Signed-off-by: Peter Jones <pjones@redhat.com>
We decide if it's a full path by if it starts with \\EFI\\. That's
quite lazy, but we can't just check \\ like you'd hope, because we need
to stay compatible with what we've set as DEFAULT_LOADER in the past,
and I don't feel like writing the full path traversal file test.
Signed-off-by: Peter Jones <pjones@redhat.com>
Woops. The net outcome of these is going to be a sleep of unknown
duration, followed by either a) ResetSystem() with some random selection
of warm/cold boot, or b) ResetSystem() returning an error and shim
returning error from efi_main().
Signed-off-by: Peter Jones <pjones@redhat.com>
Right now applications run by shim get our wrapper for Exit(), but it
doesn't do as much cleanup as it should - shim itself also exits, but
currently is not doing all the cleanup it should be doing.
This changes it so all of shim's cleanup is also performed.
Based on a patch and lots of review from Gary Lin.
Signed-off-by: Peter Jones <pjones@redhat.com>
Right now if shim_verify() sees secure_mode()==0, it exits with
EFI_SUCCESS, but accidentally leaves in_protocol=1. This means any
other call will have supressed error/warning messages.
That's wrong, so don't do it.
Signed-off-by: Peter Jones <pjones@redhat.com>
Don't run MokManager on any random error from start_image(second_stage);
only try it if it /is/ the second stage, or if start_image gave us
EFI_SECURITY_VIOLATION.
Signed-off-by: Peter Jones <pjones@redhat.com>
System services haven't been hooked if we're not in secure mode, so
do_exit() will never be called. In this case shim never gets control
once grub exits, which means if booting fails and the firmware tries
another boot option, it'll attempt to talk to the shim protocol we
installed.
This is wrong, because it is allowed to have been cleared from ram at
this time, since the task it's under has exited.
So just don't install the protocols when we're not enforcing.
This version also has a message and a 2-second stall after calling
start_image(), so that we can tell if we are on the expected return path
of our execution flow.
Turns out a) the codegen on aarch64 generates code that has real
alignment needs, and b) if we check the length of discardable sections
before discarding them, we error for no reason.
So do the error checking in the right order, and always enforce some
alignment because we know we have to.
Signed-off-by: Peter Jones <pjones@redhat.com>
We replaced the build key with an empty file while compiling shim
for our distro. Skip the verification with the empty build key
since this makes no sense.
Signed-off-by: Gary Ching-Pang Lin <glin@suse.com>
Find the relocations based on the *file* address in the old binary,
because it's only the same as the virtual address some of the time.
Also perform some extra validation before processing it, and don't bail
out in /error/ if both ReloceBase and RelocEnd are null - that condition
is fine.
Signed-off-by: Peter Jones <pjones@redhat.com>
When I merged 4bfb13d and fixed the conflicts, I managed to make the
in_protocol test exactly backwards, so that's why we don't currently see
error messages.
Signed-off-by: Peter Jones <pjones@redhat.com>
Actually check the size of our vendor cert quite early, so that there's
no confusion as to what's going on.
This isn't strictly necessary, in that in all cases if vendor_cert_size
is 0, then AuthenticodeVerify -> Pkcs7Verify() -> d2i_X509() will result
in a NULL "Cert", and it will return FALSE, and we'll reject the
signature, but better to avoid all that code in the first place. Belt
and suspenders and whatnot.
Based on a patch from https://github.com/TBOpen .
Signed-off-by: Peter Jones <pjones@redhat.com>
I screwed one of these up when working on 750584c, and it's a real pain
to figure out, so that means we should be validating them.
Signed-off-by: Peter Jones <pjones@redhat.com>
This is mostly based on a patch (https://github.com/mjg59/shim/issues/30)
from https://github.com/TBOpen , which refactors our __LP64__
tests to be tests of the header magic instead. I've simplified things
by using what we've pre-loaded into "context" and making some helper
functions so the conditionals in most of the code say what they do,
instead of how they work.
Note that we're only allowing that from in_protocol's loader - that is,
we'll let 64-bit grub load a 32-bit kernel or 32-bit grub load a 64-bit
kernel, but 32-bit shim isn't loading a 64-bit grub.
Signed-off-by: Peter Jones <pjones@redhat.com>
Currently when we process base relocations, we get the correct Data
Directory pointer from the headers (context->RelocDir), and that header
has been copied into our pristine allocated image when we copied up to
SizeOfHeaders. But the data it points to has not been mirrored in to
the new image, so it is whatever data AllocPool() gave us.
This patch changes relocate_coff() to refer to the base relocation table
from the image we loaded from disk, but apply the fixups to the new
copy.
I have no idea how x86_64 worked without this, but I can't make aarch64
work without it. I also don't know how Ard or Leif have seen aarch64
work. Maybe they haven't? Leif indicated on irc that they may have
only tested shim with simple "hello world" applications from gnu-efi;
they are certainly much less complex than grub.efi, and are generated
through a different linking process.
My only theory is that we're getting recycled data there pretty reliably
that just makes us /not/ process any relocations, but since our
ImageBase is 0, and I don't think we ever load grub with 0 as its base
virtual address, that doesn't follow. I'm open to any other ideas
anybody has.
I do know that on x86_64 (and presumably aarch64 as well), we don't
actually start seeing *symptoms* of this bug until the first chunk[0] of
94c9a77f is applied[1]. Once that is applied, relocate_coff() starts
seeing zero[2] for both RelocBase->VirtualAddress and
RelocBase->SizeOfBlock, because RelocBase is a (generated, relative)
pointer that only makes sense in the context of the original binary, not
our partial copy. Since RelocBase->SizeOfBlock is tested first,
relocate_base() gives us "Reloc block size is invalid"[3] and returns
EFI_UNSUPPORTED. At that point shim exits with an error.
[0] The second chunk of 94c9a77f patch makes no difference on this
issue.
[1] I don't see why at all.
[2] Which could really be any value since it's AllocatePool() and not
AllocateZeroPool() results, but 0 is all I've observed; I think
AllocatePool() has simply never recycled any memory in my test
cases.
[3] which is silent because perror() tries to avoid talking because that
has caused much crashing in the past; work needs to go in to 0.9 for
this.
Signed-off-by: Peter Jones <pjones@redhat.com>
Since in theory you could, for example, get an x86_64 binary signed that
also behaves as an ARM executable, we should be checking this before
people build on other architectures.
Signed-off-by: Peter Jones <pjones@redhat.com>
On archs where no EFI aware objcopy is available, the generated PE/COFF
header contains a .reloc section which is completely empty. Handle this by
- returning early from relocate_coff() with EFI_SUCCESS,
- ignoring discardable sections in the section loader.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
MokSBState and MokDBState are just 1 byte variables, so a UINT8
local variable is sufficient to include the content.
Signed-off-by: Gary Ching-Pang Lin <glin@suse.com>
Conflicts:
shim.c
