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certs: Add EFI_CERT_X509_GUID support for dbx entries

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This fixes CVE-2020-26541.

The Secure Boot Forbidden Signature Database, dbx, contains a list of now
revoked signatures and keys previously approved to boot with UEFI Secure
Boot enabled.  The dbx is capable of containing any number of
EFI_CERT_X509_SHA256_GUID, EFI_CERT_SHA256_GUID, and EFI_CERT_X509_GUID
entries.

Currently when EFI_CERT_X509_GUID are contained in the dbx, the entries are
skipped.

Add support for EFI_CERT_X509_GUID dbx entries. When a EFI_CERT_X509_GUID
is found, it is added as an asymmetrical key to the .blacklist keyring.
Anytime the .platform keyring is used, the keys in the .blacklist keyring
are referenced, if a matching key is found, the key will be rejected.

[DH: Made the following changes:
 - Added to have a config option to enable the facility.  This allows a
   Kconfig solution to make sure that pkcs7_validate_trust() is
   enabled.[1][2]
 - Moved the functions out from the middle of the blacklist functions.
 - Added kerneldoc comments.]

Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
cc: Randy Dunlap <rdunlap@infradead.org>
cc: Mickaël Salaün <mic@digikod.net>
cc: Arnd Bergmann <arnd@kernel.org>
cc: keyrings@vger.kernel.org
Link: https://lore.kernel.org/r/20200901165143.10295-1-eric.snowberg@oracle.com/ # rfc
Link: https://lore.kernel.org/r/20200909172736.73003-1-eric.snowberg@oracle.com/ # v2
Link: https://lore.kernel.org/r/20200911182230.62266-1-eric.snowberg@oracle.com/ # v3
Link: https://lore.kernel.org/r/20200916004927.64276-1-eric.snowberg@oracle.com/ # v4
Link: https://lore.kernel.org/r/20210122181054.32635-2-eric.snowberg@oracle.com/ # v5
Link: https://lore.kernel.org/r/161428672051.677100.11064981943343605138.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/r/161433310942.902181.4901864302675874242.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/161529605075.163428.14625520893961300757.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/bc2c24e3-ed68-2521-0bf4-a1f6be4a895d@infradead.org/ [1]
Link: https://lore.kernel.org/r/20210225125638.1841436-1-arnd@kernel.org/ [2]
This commit is contained in:
Eric Snowberg
2021-01-22 13:10:51 -05:00
committed by David Howells
parent 8f0bfc25c9
commit 56c5812623
6 changed files with 86 additions and 0 deletions
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43
certs/blacklist.c
View File

@@ -145,6 +145,49 @@ int is_binary_blacklisted(const u8 *hash, size_t hash_len)
}
EXPORT_SYMBOL_GPL(is_binary_blacklisted);
#ifdef CONFIG_SYSTEM_REVOCATION_LIST
/**
* add_key_to_revocation_list - Add a revocation certificate to the blacklist
* @data: The data blob containing the certificate
* @size: The size of data blob
*/
int add_key_to_revocation_list(const char *data, size_t size)
{
key_ref_t key;
key = key_create_or_update(make_key_ref(blacklist_keyring, true),
"asymmetric",
NULL,
data,
size,
((KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW),
KEY_ALLOC_NOT_IN_QUOTA | KEY_ALLOC_BUILT_IN);
if (IS_ERR(key)) {
pr_err("Problem with revocation key (%ld)\n", PTR_ERR(key));
return PTR_ERR(key);
}
return 0;
}
/**
* is_key_on_revocation_list - Determine if the key for a PKCS#7 message is revoked
* @pkcs7: The PKCS#7 message to check
*/
int is_key_on_revocation_list(struct pkcs7_message *pkcs7)
{
int ret;
ret = pkcs7_validate_trust(pkcs7, blacklist_keyring);
if (ret == 0)
return -EKEYREJECTED;
return -ENOKEY;
}
#endif
/*
* Initialise the blacklist
*/