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 <[email protected]>
---
v3:
Fixed an issue when CONFIG_PKCS7_MESSAGE_PARSER is not builtin and defined
as a module instead, pointed out by Randy Dunlap
v2:
Fixed build issue reported by kernel test robot <[email protected]>
Commit message update (suggested by Jarkko Sakkinen)
---
certs/blacklist.c | 33 +++++++++++++++++++
certs/blacklist.h | 12 +++++++
certs/system_keyring.c | 6 ++++
include/keys/system_keyring.h | 11 +++++++
.../platform_certs/keyring_handler.c | 11 +++++++
5 files changed, 73 insertions(+)
diff --git a/certs/blacklist.c b/certs/blacklist.c
index 6514f9ebc943..3d1514ba5d47 100644
--- a/certs/blacklist.c
+++ b/certs/blacklist.c
@@ -100,6 +100,39 @@ int mark_hash_blacklisted(const char *hash)
return 0;
}
+int mark_key_revocationlisted(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_revocationlisted(struct pkcs7_message *pkcs7)
+{
+ int ret;
+
+ ret = validate_trust(pkcs7, blacklist_keyring);
+
+ if (ret == 0)
+ return -EKEYREJECTED;
+
+ return -ENOKEY;
+}
+EXPORT_SYMBOL_GPL(is_key_revocationlisted);
+
/**
* 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..f8ea96219155 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_revocationlisted(pkcs7);
+ if (ret != -ENOKEY) {
+ pr_devel("PKCS#7 platform key revocationlisted\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..b6991cfe1b6d 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 mark_key_revocationlisted(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_revocationlisted(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 mark_key_revocationlisted(const char *data, size_t size)
+{
+ return 0;
+}
+static inline int is_key_revocationlisted(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..cc5a43804bc4 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);
}
+/*
+ * Revocationlist the X509 cert
+ */
+static __init void uefi_revocationlist_x509(const char *source,
+ const void *data, size_t len)
+{
+ mark_key_revocationlisted(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_revocationlist_x509;
return 0;
}
--
2.18.1
> On Sep 14, 2020, at 12:12 PM, Jarkko Sakkinen <[email protected]> wrote:
>
> On Fri, Sep 11, 2020 at 02:22:30PM -0400, Eric Snowberg wrote:
>> 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 <[email protected]>
>> ---
>> v3:
>> Fixed an issue when CONFIG_PKCS7_MESSAGE_PARSER is not builtin and defined
>> as a module instead, pointed out by Randy Dunlap
>>
>> v2:
>> Fixed build issue reported by kernel test robot <[email protected]>
>> Commit message update (suggested by Jarkko Sakkinen)
>> ---
>> certs/blacklist.c | 33 +++++++++++++++++++
>> certs/blacklist.h | 12 +++++++
>> certs/system_keyring.c | 6 ++++
>> include/keys/system_keyring.h | 11 +++++++
>> .../platform_certs/keyring_handler.c | 11 +++++++
>> 5 files changed, 73 insertions(+)
>>
>> diff --git a/certs/blacklist.c b/certs/blacklist.c
>> index 6514f9ebc943..3d1514ba5d47 100644
>> --- a/certs/blacklist.c
>> +++ b/certs/blacklist.c
>> @@ -100,6 +100,39 @@ int mark_hash_blacklisted(const char *hash)
>> return 0;
>> }
>>
>> +int mark_key_revocationlisted(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_revocationlisted(struct pkcs7_message *pkcs7)
>> +{
>> + int ret;
>> +
>> + ret = validate_trust(pkcs7, blacklist_keyring);
>> +
>> + if (ret == 0)
>> + return -EKEYREJECTED;
>> +
>> + return -ENOKEY;
>> +}
>> +EXPORT_SYMBOL_GPL(is_key_revocationlisted);
>
> Hmm... ignore my previous comment about this. Export symbol is called
> only by system keyring code.
>
> Would be best if the commit message would explicitly reason new exports.
I don’t see a good reason to keep the export now, I’ll remove it from the
next version. Thanks.
On Tue, Sep 15, 2020 at 09:42:27AM -0600, Eric Snowberg wrote:
>
> > On Sep 14, 2020, at 12:12 PM, Jarkko Sakkinen <[email protected]> wrote:
> >
> > On Fri, Sep 11, 2020 at 02:22:30PM -0400, Eric Snowberg wrote:
> >> 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 <[email protected]>
> >> ---
> >> v3:
> >> Fixed an issue when CONFIG_PKCS7_MESSAGE_PARSER is not builtin and defined
> >> as a module instead, pointed out by Randy Dunlap
> >>
> >> v2:
> >> Fixed build issue reported by kernel test robot <[email protected]>
> >> Commit message update (suggested by Jarkko Sakkinen)
> >> ---
> >> certs/blacklist.c | 33 +++++++++++++++++++
> >> certs/blacklist.h | 12 +++++++
> >> certs/system_keyring.c | 6 ++++
> >> include/keys/system_keyring.h | 11 +++++++
> >> .../platform_certs/keyring_handler.c | 11 +++++++
> >> 5 files changed, 73 insertions(+)
> >>
> >> diff --git a/certs/blacklist.c b/certs/blacklist.c
> >> index 6514f9ebc943..3d1514ba5d47 100644
> >> --- a/certs/blacklist.c
> >> +++ b/certs/blacklist.c
> >> @@ -100,6 +100,39 @@ int mark_hash_blacklisted(const char *hash)
> >> return 0;
> >> }
> >>
> >> +int mark_key_revocationlisted(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_revocationlisted(struct pkcs7_message *pkcs7)
> >> +{
> >> + int ret;
> >> +
> >> + ret = validate_trust(pkcs7, blacklist_keyring);
> >> +
> >> + if (ret == 0)
> >> + return -EKEYREJECTED;
> >> +
> >> + return -ENOKEY;
> >> +}
> >> +EXPORT_SYMBOL_GPL(is_key_revocationlisted);
> >
> > Hmm... ignore my previous comment about this. Export symbol is called
> > only by system keyring code.
> >
> > Would be best if the commit message would explicitly reason new exports.
>
> I don’t see a good reason to keep the export now, I’ll remove it from the
> next version. Thanks.
OK, great, thanks.
Was somewhat puzzled with this for a while :-)
/Jarkko