From 56c5812623f95313f6a46fbf0beee7fa17c68bbf Mon Sep 17 00:00:00 2001 From: Eric Snowberg Date: Fri, 22 Jan 2021 13:10:51 -0500 Subject: certs: Add EFI_CERT_X509_GUID support for dbx entries MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: David Howells Reviewed-by: Jarkko Sakkinen cc: Randy Dunlap cc: Mickaël Salaün cc: Arnd Bergmann 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] --- security/integrity/platform_certs/keyring_handler.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'security') diff --git a/security/integrity/platform_certs/keyring_handler.c b/security/integrity/platform_certs/keyring_handler.c index c5ba695c10e3..5604bd57c990 100644 --- a/security/integrity/platform_certs/keyring_handler.c +++ b/security/integrity/platform_certs/keyring_handler.c @@ -55,6 +55,15 @@ static __init void uefi_blacklist_binary(const char *source, uefi_blacklist_hash(source, data, len, "bin:", 4); } +/* + * Add an X509 cert to the revocation list. + */ +static __init void uefi_revocation_list_x509(const char *source, + const void *data, size_t len) +{ + add_key_to_revocation_list(data, len); +} + /* * Return the appropriate handler for particular signature list types found in * the UEFI db and MokListRT tables. @@ -76,5 +85,7 @@ __init efi_element_handler_t get_handler_for_dbx(const efi_guid_t *sig_type) return uefi_blacklist_x509_tbs; if (efi_guidcmp(*sig_type, efi_cert_sha256_guid) == 0) return uefi_blacklist_binary; + if (efi_guidcmp(*sig_type, efi_cert_x509_guid) == 0) + return uefi_revocation_list_x509; return 0; } -- cgit v1.2.3 From ebd9c2ae369a45bdd9f8615484db09be58fc242b Mon Sep 17 00:00:00 2001 From: Eric Snowberg Date: Fri, 22 Jan 2021 13:10:54 -0500 Subject: integrity: Load mokx variables into the blacklist keyring During boot the Secure Boot Forbidden Signature Database, dbx, is loaded into the blacklist keyring. Systems booted with shim have an equivalent Forbidden Signature Database called mokx. Currently mokx is only used by shim and grub, the contents are ignored by the kernel. Add the ability to load mokx into the blacklist keyring during boot. Signed-off-by: Eric Snowberg Suggested-by: James Bottomley Signed-off-by: David Howells Reviewed-by: Jarkko Sakkinen cc: keyrings@vger.kernel.org Link: https://lore.kernel.org/r/c33c8e3839a41e9654f41cc92c7231104931b1d7.camel@HansenPartnership.com/ Link: https://lore.kernel.org/r/20210122181054.32635-5-eric.snowberg@oracle.com/ # v5 Link: https://lore.kernel.org/r/161428674320.677100.12637282414018170743.stgit@warthog.procyon.org.uk/ Link: https://lore.kernel.org/r/161433313205.902181.2502803393898221637.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/161529607422.163428.13530426573612578854.stgit@warthog.procyon.org.uk/ # v3 --- security/integrity/platform_certs/load_uefi.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) (limited to 'security') diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c index ee4b4c666854..f290f78c3f30 100644 --- a/security/integrity/platform_certs/load_uefi.c +++ b/security/integrity/platform_certs/load_uefi.c @@ -132,8 +132,9 @@ static int __init load_moklist_certs(void) static int __init load_uefi_certs(void) { efi_guid_t secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID; - void *db = NULL, *dbx = NULL; - unsigned long dbsize = 0, dbxsize = 0; + efi_guid_t mok_var = EFI_SHIM_LOCK_GUID; + void *db = NULL, *dbx = NULL, *mokx = NULL; + unsigned long dbsize = 0, dbxsize = 0, mokxsize = 0; efi_status_t status; int rc = 0; @@ -175,6 +176,21 @@ static int __init load_uefi_certs(void) kfree(dbx); } + mokx = get_cert_list(L"MokListXRT", &mok_var, &mokxsize, &status); + if (!mokx) { + if (status == EFI_NOT_FOUND) + pr_debug("mokx variable wasn't found\n"); + else + pr_info("Couldn't get mokx list\n"); + } else { + rc = parse_efi_signature_list("UEFI:MokListXRT", + mokx, mokxsize, + get_handler_for_dbx); + if (rc) + pr_err("Couldn't parse mokx signatures %d\n", rc); + kfree(mokx); + } + /* Load the MokListRT certs */ rc = load_moklist_certs(); -- cgit v1.2.3