KEYS: Add a 'trusted' flag and a 'trusted only' flag
Add KEY_FLAG_TRUSTED to indicate that a key either comes from a trusted source
or had a cryptographic signature chain that led back to a trusted key the
kernel already possessed.
Add KEY_FLAGS_TRUSTED_ONLY to indicate that a keyring will only accept links to
keys marked with KEY_FLAGS_TRUSTED.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
diff --git a/include/linux/key-type.h b/include/linux/key-type.h
index f58737b..a74c3a8 100644
--- a/include/linux/key-type.h
+++ b/include/linux/key-type.h
@@ -45,6 +45,7 @@
const void *data; /* Raw data */
size_t datalen; /* Raw datalen */
size_t quotalen; /* Quota length for proposed payload */
+ bool trusted; /* True if key is trusted */
};
typedef int (*request_key_actor_t)(struct key_construction *key,
diff --git a/include/linux/key.h b/include/linux/key.h
index 010dbb6..80d6774 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -168,6 +168,8 @@
#define KEY_FLAG_NEGATIVE 5 /* set if key is negative */
#define KEY_FLAG_ROOT_CAN_CLEAR 6 /* set if key can be cleared by root without permission */
#define KEY_FLAG_INVALIDATED 7 /* set if key has been invalidated */
+#define KEY_FLAG_TRUSTED 8 /* set if key is trusted */
+#define KEY_FLAG_TRUSTED_ONLY 9 /* set if keyring only accepts links to trusted keys */
/* the key type and key description string
* - the desc is used to match a key against search criteria
@@ -218,6 +220,7 @@
#define KEY_ALLOC_IN_QUOTA 0x0000 /* add to quota, reject if would overrun */
#define KEY_ALLOC_QUOTA_OVERRUN 0x0001 /* add to quota, permit even if overrun */
#define KEY_ALLOC_NOT_IN_QUOTA 0x0002 /* not in quota */
+#define KEY_ALLOC_TRUSTED 0x0004 /* Key should be flagged as trusted */
extern void key_revoke(struct key *key);
extern void key_invalidate(struct key *key);
diff --git a/kernel/system_keyring.c b/kernel/system_keyring.c
index 51c3514..5296721 100644
--- a/kernel/system_keyring.c
+++ b/kernel/system_keyring.c
@@ -40,6 +40,7 @@
if (IS_ERR(system_trusted_keyring))
panic("Can't allocate system trusted keyring\n");
+ set_bit(KEY_FLAG_TRUSTED_ONLY, &system_trusted_keyring->flags);
return 0;
}
@@ -82,7 +83,8 @@
plen,
(KEY_POS_ALL & ~KEY_POS_SETATTR) |
KEY_USR_VIEW,
- KEY_ALLOC_NOT_IN_QUOTA);
+ KEY_ALLOC_NOT_IN_QUOTA |
+ KEY_ALLOC_TRUSTED);
if (IS_ERR(key)) {
pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
PTR_ERR(key));
diff --git a/security/keys/key.c b/security/keys/key.c
index a819b5c..d331ea9 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -300,6 +300,8 @@
if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
key->flags |= 1 << KEY_FLAG_IN_QUOTA;
+ if (flags & KEY_ALLOC_TRUSTED)
+ key->flags |= 1 << KEY_FLAG_TRUSTED;
memset(&key->type_data, 0, sizeof(key->type_data));
@@ -813,6 +815,7 @@
prep.data = payload;
prep.datalen = plen;
prep.quotalen = index_key.type->def_datalen;
+ prep.trusted = flags & KEY_ALLOC_TRUSTED;
if (index_key.type->preparse) {
ret = index_key.type->preparse(&prep);
if (ret < 0) {
@@ -827,6 +830,11 @@
}
index_key.desc_len = strlen(index_key.description);
+ key_ref = ERR_PTR(-EPERM);
+ if (!prep.trusted && test_bit(KEY_FLAG_TRUSTED_ONLY, &keyring->flags))
+ goto error_free_prep;
+ flags |= prep.trusted ? KEY_ALLOC_TRUSTED : 0;
+
ret = __key_link_begin(keyring, &index_key, &edit);
if (ret < 0) {
key_ref = ERR_PTR(ret);
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index f7cdea2..9b6f6e0 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -1183,6 +1183,10 @@
key_check(keyring);
key_check(key);
+ if (test_bit(KEY_FLAG_TRUSTED_ONLY, &keyring->flags) &&
+ !test_bit(KEY_FLAG_TRUSTED, &key->flags))
+ return -EPERM;
+
ret = __key_link_begin(keyring, &key->index_key, &edit);
if (ret == 0) {
kdebug("begun {%d,%d}", keyring->serial, atomic_read(&keyring->usage));