How about the attached? I've changed the function names to something that I think reads better, but otherwise it's the same.
David --- commit 8913866babb96fcfe452aac6042ca8862d4c0b53 Author: Eric Snowberg <eric.snowb...@oracle.com> Date: Tue Sep 15 20:49:27 2020 -0400 certs: Add EFI_CERT_X509_GUID support for dbx entries 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. Signed-off-by: Eric Snowberg <eric.snowb...@oracle.com> Reviewed-by: Jarkko Sakkinen <jarkko.sakki...@linux.intel.com> Signed-off-by: David Howells <dhowe...@redhat.com> diff --git a/certs/blacklist.c b/certs/blacklist.c index 6514f9ebc943..a7f021878a4b 100644 --- a/certs/blacklist.c +++ b/certs/blacklist.c @@ -100,6 +100,38 @@ int mark_hash_blacklisted(const char *hash) return 0; } +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; +} + +int is_key_on_revocation_list(struct pkcs7_message *pkcs7) +{ + int ret; + + ret = validate_trust(pkcs7, blacklist_keyring); + + if (ret == 0) + return -EKEYREJECTED; + + return -ENOKEY; +} + /** * is_hash_blacklisted - Determine if a hash is blacklisted * @hash: The hash to be checked as a binary blob diff --git a/certs/blacklist.h b/certs/blacklist.h index 1efd6fa0dc60..420bb7c86e07 100644 --- a/certs/blacklist.h +++ b/certs/blacklist.h @@ -1,3 +1,15 @@ #include <linux/kernel.h> +#include <linux/errno.h> +#include <crypto/pkcs7.h> extern const char __initconst *const blacklist_hashes[]; + +#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING +#define validate_trust pkcs7_validate_trust +#else +static inline int validate_trust(struct pkcs7_message *pkcs7, + struct key *trust_keyring) +{ + return -ENOKEY; +} +#endif diff --git a/certs/system_keyring.c b/certs/system_keyring.c index 798291177186..cc165b359ea3 100644 --- a/certs/system_keyring.c +++ b/certs/system_keyring.c @@ -241,6 +241,12 @@ int verify_pkcs7_message_sig(const void *data, size_t len, pr_devel("PKCS#7 platform keyring is not available\n"); goto error; } + + ret = is_key_on_revocation_list(pkcs7); + if (ret != -ENOKEY) { + pr_devel("PKCS#7 platform key is on revocation list\n"); + goto error; + } } ret = pkcs7_validate_trust(pkcs7, trusted_keys); if (ret < 0) { diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h index fb8b07daa9d1..61f98739e8b1 100644 --- a/include/keys/system_keyring.h +++ b/include/keys/system_keyring.h @@ -31,11 +31,14 @@ extern int restrict_link_by_builtin_and_secondary_trusted( #define restrict_link_by_builtin_and_secondary_trusted restrict_link_by_builtin_trusted #endif +extern struct pkcs7_message *pkcs7; #ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING extern int mark_hash_blacklisted(const char *hash); +extern int add_key_to_revocation_list(const char *data, size_t size); extern int is_hash_blacklisted(const u8 *hash, size_t hash_len, const char *type); extern int is_binary_blacklisted(const u8 *hash, size_t hash_len); +extern int is_key_on_revocation_list(struct pkcs7_message *pkcs7); #else static inline int is_hash_blacklisted(const u8 *hash, size_t hash_len, const char *type) @@ -47,6 +50,14 @@ static inline int is_binary_blacklisted(const u8 *hash, size_t hash_len) { return 0; } +static inline int add_key_to_revocation_list(const char *data, size_t size) +{ + return 0; +} +static inline int is_key_on_revocation_list(struct pkcs7_message *pkcs7) +{ + return -ENOKEY; +} #endif #ifdef CONFIG_IMA_BLACKLIST_KEYRING 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; }