The general rule of accepting or rejecting an image is
1. Is the sha256 of the image in dbx
2. Is the image signed with a certificate that's found in db and
not in dbx
3. The image carries a cert which is signed by a cert in db (and
not in dbx) and the image can be verified against the former
4. Is the sha256 of the image in db
For example SHIM is signed by "CN=Microsoft Windows UEFI Driver Publisher",
which is issued by "CN=Microsoft Corporation UEFI CA 2011", which in it's
turn is issued by "CN=Microsoft Corporation Third Party Marketplace Root".
The latter is a self-signed CA certificate and with our current implementation
allows shim to execute if we insert it in db.
However it's the CA cert in the middle of the chain which usually ends up
in the system's db. pkcs7_verify_one() might or might not return the root
certificate for a given chain. But when verifying executables in UEFI, the
trust anchor can be in the middle of the chain, as long as that certificate
is present in db. Currently we only allow this check on self-signed
certificates, so let's remove that check and allow all certs to try a
match an entry in db.
Open questions:
- Does this break any aspect of variable authentication since
efi_signature_verify() is used on those as well?
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
We don't have to recalculate the image hash every time we check against a
new db/dbx entry. So let's add a flag forcing it to run once since we only
support sha256 hashes
Suggested-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
A mix of signatures and hashes in db doesn't always work as intended.
Currently if the digest algorithm is not explicitly set to sha256 we
stop walking the security database and reject the image.
That's problematic in case we find and try to check a signature before
inspecting the sha256 hash. If the image is unsigned we will reject it
even if the digest matches.
Since we no longer reject the image on unknown algorithms add an explicit
check and reject the image if any other hash algorithm apart from sha256
is detected on dbx.
Suggested-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
For printing GUIDs with macro EFI_ENTRY use %pUs instead of %pUl to provide
readable debug output.
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Simplify efi_sigstore_parse_sigdb() by using existing functions.
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
This is preparation for PE/COFF measurement support.
PE/COFF image hash calculation is same in both
UEFI Secure Boot image verification and measurement in
measured boot. PE/COFF image parsing functions are
gathered into efi_image_loader.c, and exposed even if
UEFI Secure Boot is not enabled.
This commit also adds the EFI_SIGNATURE_SUPPORT option
to decide if efi_signature.c shall be compiled.
Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Add support for authenticating uefi capsules. Most of the signature
verification functionality is shared with the uefi secure boot
feature.
The root certificate containing the public key used for the signature
verification is stored as part of the device tree blob. The root
certificate is stored as an efi signature list(esl) file -- this file
contains the x509 certificate which is the root certificate.
Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
The efi_sigstore_parse_sigdb function reads the uefi authenticated
variable, stored in the signature database format and builds the
signature store structure. Factor out the code for building
the signature store. This can then be used by the capsule
authentication routine to build the signature store even when the
signature database is not stored as an uefi authenticated variable
Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
The pkcs7 header parsing functionality is pretty generic, and can be
used by other features like capsule authentication. Make the function
an extern, also changing it's name to efi_parse_pkcs7_header
Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Under the current implementation, all the signatures, if any, in
a signed image must be verified before loading it.
Meanwhile, UEFI specification v2.8b section 32.5.3.3 says,
Multiple signatures are allowed to exist in the binary’s certificate
table (as per PE/COFF Section “Attribute Certificate Table”). Only
one hash or signature is required to be present in db in order to pass
validation, so long as neither the SHA-256 hash of the binary nor any
present signature is reflected in dbx.
This patch makes the semantics of signature verification compliant with
the specification mentioned above.
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
In this commit, efi_signature_verify(with_sigdb) will be re-implemented
using pcks7_verify_one() in order to support certificates chain, where
the signer's certificate will be signed by an intermediate CA (certificate
authority) and the latter's certificate will also be signed by another CA
and so on.
What we need to do here is to search for certificates in a signature,
build up a chain of certificates and verify one by one. pkcs7_verify_one()
handles most of these steps except the last one.
pkcs7_verify_one() returns, if succeeded, the last certificate to verify,
which can be either a self-signed one or one that should be signed by one
of certificates in "db". Re-worked efi_signature_verify() will take care
of this step.
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
In case that a type of certificate in "db" or "dbx" is
EFI_CERT_X509_SHA256_GUID, it is actually not a certificate which contains
a public key for RSA decryption, but a digest of image to be loaded.
If the value matches to a value calculated from a given binary image, it is
granted for loading.
With this patch, common digest check code, which used to be used for
unsigned image verification, will be extracted from
efi_signature_verify_with_sigdb() into efi_signature_lookup_digest(), and
extra step for digest check will be added to efi_image_authenticate().
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
A signed image may have multiple signatures in
- each WIN_CERTIFICATE in authenticode, and/or
- each SignerInfo in pkcs7 SignedData (of WIN_CERTIFICATE)
In the initial implementation of efi_image_authenticate(), the criteria
of verification check for multiple signatures case is a bit ambiguous
and it may cause inconsistent result.
With this patch, we will make sure that verification check in
efi_image_authenticate() should pass against all the signatures.
The only exception would be
- the case where a digest algorithm used in signature is not supported by
U-Boot, or
- the case where parsing some portion of authenticode has failed
In those cases, we don't know how the signature be handled and should
just ignore them.
Please note that, due to this change, efi_signature_verify_with_sigdb()'s
function prototype will be modified, taking "dbx" as well as "db"
instead of outputing a "certificate." If "dbx" is null, the behavior would
be the exact same as before.
The function's name will be changed to efi_signature_verify() once
current efi_signature_verify() has gone due to further improvement
in intermediate certificates support.
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
There are a couple of occurrences of hash calculations in which a new
efi_hash_regions will be commonly used.
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Since the size check against an entry in efi_search_siglist() is
incorrect, this function will never find out a to-be-matched certificate
and its associated revocation time in the signature list.
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Just for style consistency, replace all the uses of debug to
EFI_PRINT in efi_signature.c
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
The global variable, efi_guid_cert_type_pkcs7, will also be used in
efi_image_loader.c in a succeeding patch so as to correctly handle
a signature type of authenticode in signed image.
Meanwhile, it is currently defined in efi_variable.c. Once some secure
storage solution for UEFI variables is introduced, efi_variable.c may
not always be compiled in.
So move the definition to efi_signature.c as a common place.
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
"if (left < esl->signature_size)" is not reachable in a while loop.
But it is still valuable in case that a given signature database is
somehow corrupted. So fix the while loop condition.
Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Pkcs7_parse.h and x509_parser.h are used in UEFI subsystem, in particular,
secure boot. So move them to include/crypto to avoid relative paths.
Suggested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Don't include include x509_parser.h twice.
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
efi_signature_parse_sigdb() is a helper function will be used to parse
signature database variable and instantiate a signature store structure
in later patches.
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
In this commit, implemented are a couple of helper functions which will be
used to materialize variable authentication as well as image authentication
in later patches.
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
