Add a secondary system keyring that can be added to by root whilst the
system is running - provided the key being added is vouched for by a key
built into the kernel or already added to the secondary keyring.
Rename .system_keyring to .builtin_trusted_keys to distinguish it more
obviously from the new keyring (called .secondary_trusted_keys).
The new keyring needs to be enabled with CONFIG_SECONDARY_TRUSTED_KEYRING.
If the secondary keyring is enabled, a link is created from that to
.builtin_trusted_keys so that the the latter will automatically be searched
too if the secondary keyring is searched.
Signed-off-by: David Howells <dhowe...@redhat.com>
---
certs/Kconfig | 8 ++++
certs/system_keyring.c | 79 ++++++++++++++++++++++++++++++++++-------
include/keys/system_keyring.h | 4 ++
3 files changed, 78 insertions(+), 13 deletions(-)
diff --git a/certs/Kconfig b/certs/Kconfig
index 743d480f5f6f..fc5955f5fc8a 100644
--- a/certs/Kconfig
+++ b/certs/Kconfig
@@ -56,4 +56,12 @@ config SYSTEM_EXTRA_CERTIFICATE_SIZE
This is the number of bytes reserved in the kernel image for a
certificate to be inserted.
+config SECONDARY_TRUSTED_KEYRING
+ bool "Provide a keyring to which extra trustable keys may be added"
+ depends on SYSTEM_TRUSTED_KEYRING
+ help
+ If set, provide a keyring to which extra keys may be added, provided
+ those keys are not blacklisted and are vouched for by a key built
+ into the kernel or already in the secondary trusted keyring.
+
endmenu
diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index 3cfc88c76aee..9700f37350ff 100644
--- a/certs/system_keyring.c
+++ b/certs/system_keyring.c
@@ -18,7 +18,10 @@
#include <keys/system_keyring.h>
#include <crypto/pkcs7.h>
-static struct key *system_trusted_keyring;
+static struct key *builtin_trusted_keys;
+#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
+static struct key *secondary_trusted_keys;
+#endif
extern __initconst const u8 system_certificate_list[];
extern __initconst const unsigned long system_certificate_list_size;
@@ -33,26 +36,68 @@ int restrict_link_by_system_trusted(struct key *keyring,
const struct key_type *type,
const union key_payload *payload)
{
- return restrict_link_by_signature(system_trusted_keyring,
- type, payload);
+ /* If we have a secondary trusted keyring, then that contains a link
+ * through to the builtin keyring and the search will follow that link.
+ */
+#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
+ if (type == &key_type_keyring &&
+ keyring == secondary_trusted_keys &&
+ payload == &builtin_trusted_keys->payload)
+ /* Allow the builtin keyring to be added to the secondary */
+ return 0;
+
+ return restrict_link_by_signature(secondary_trusted_keys, type,
payload);
+#else
+ return restrict_link_by_signature(builtin_trusted_keys, type, payload);
+#endif
+}
+
+/**
+ * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA
+ *
+ * Restrict the addition of keys into a keyring based on the key-to-be-added
+ * being vouched for by a key in the built in system keyring.
+ */
+int restrict_link_by_builtin_trusted(struct key *keyring,
+ const struct key_type *type,
+ const union key_payload *payload)
+{
+ return restrict_link_by_signature(builtin_trusted_keys, type, payload);
}
/*
- * Load the compiled-in keys
+ * Create the trusted keyrings
*/
static __init int system_trusted_keyring_init(void)
{
- pr_notice("Initialise system trusted keyring\n");
+ pr_notice("Initialise system trusted keyrings\n");
- system_trusted_keyring =
- keyring_alloc(".system_keyring",
+ builtin_trusted_keys =
+ keyring_alloc(".builtin_trusted_keys",
KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
((KEY_POS_ALL & ~KEY_POS_SETATTR) |
KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
KEY_ALLOC_NOT_IN_QUOTA,
+ NULL, NULL);
+ if (IS_ERR(builtin_trusted_keys))
+ panic("Can't allocate builtin trusted keyring\n");
+
+#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
+ secondary_trusted_keys =
+ keyring_alloc(".secondary_trusted_keys",
+ KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
+ ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
+ KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
+ KEY_USR_WRITE),
+ KEY_ALLOC_NOT_IN_QUOTA,
restrict_link_by_system_trusted, NULL);
- if (IS_ERR(system_trusted_keyring))
- panic("Can't allocate system trusted keyring\n");
+ if (IS_ERR(secondary_trusted_keys))
+ panic("Can't allocate secondary trusted keyring\n");
+
+ if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
+ panic("Can't link trusted keyrings\n");
+#endif
+
return 0;
}
@@ -88,7 +133,7 @@ static __init int load_system_certificate_list(void)
if (plen > end - p)
goto dodgy_cert;
- key = key_create_or_update(make_key_ref(system_trusted_keyring,
1),
+ key = key_create_or_update(make_key_ref(builtin_trusted_keys,
1),
"asymmetric",
NULL,
p,
@@ -125,7 +170,8 @@ late_initcall(load_system_certificate_list);
* @len: Size of @data.
* @raw_pkcs7: The PKCS#7 message that is the signature.
* @pkcs7_len: The size of @raw_pkcs7.
- * @trusted_keys: Trusted keys to use (NULL for system_trusted_keyring).
+ * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
+ * (void *)1UL for all trusted keys).
* @usage: The use to which the key is being put.
* @view_content: Callback to gain access to content.
* @ctx: Context for callback.
@@ -157,8 +203,15 @@ int verify_pkcs7_signature(const void *data, size_t len,
if (ret < 0)
goto error;
- if (!trusted_keys)
- trusted_keys = system_trusted_keyring;
+ if (!trusted_keys) {
+ trusted_keys = builtin_trusted_keys;
+ } else if (trusted_keys == (void *)1UL) {
+#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
+ trusted_keys = secondary_trusted_keys;
+#else
+ trusted_keys = builtin_trusted_keys;
+#endif
+ }
ret = pkcs7_validate_trust(pkcs7, trusted_keys);
if (ret < 0) {
if (ret == -ENOKEY)
diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
index 71f3e2523767..c6c05f1513f5 100644
--- a/include/keys/system_keyring.h
+++ b/include/keys/system_keyring.h
@@ -19,9 +19,13 @@
extern int restrict_link_by_system_trusted(struct key *keyring,
const struct key_type *type,
const union key_payload *payload);
+extern int restrict_link_by_builtin_trusted(struct key *keyring,
+ const struct key_type *type,
+ const union key_payload *payload);
#else
#define restrict_link_by_system_trusted restrict_link_reject
+#define restrict_link_by_builtin_trusted restrict_link_reject
#endif
#ifdef CONFIG_IMA_MOK_KEYRING
