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authorDavid Howells <dhowells@redhat.com>2019-06-27 23:03:07 +0100
committerDavid Howells <dhowells@redhat.com>2019-07-03 13:05:22 +0100
commit7a1ade847596dadc94b37e49f8c03f167fd71748 (patch)
tree22ba37dfcac2fff9ad83c41bc1dd84e5d268ad35 /security
parentkeys: Replace uid/gid/perm permissions checking with an ACL (diff)
downloadlinux-dev-7a1ade847596dadc94b37e49f8c03f167fd71748.tar.xz
linux-dev-7a1ade847596dadc94b37e49f8c03f167fd71748.zip
keys: Provide KEYCTL_GRANT_PERMISSION
Provide a keyctl() operation to grant/remove permissions. The grant operation, wrapped by libkeyutils, looks like: int ret = keyctl_grant_permission(key_serial_t key, enum key_ace_subject_type type, unsigned int subject, unsigned int perm); Where key is the key to be modified, type and subject represent the subject to which permission is to be granted (or removed) and perm is the set of permissions to be granted. 0 is returned on success. SET_SECURITY permission is required for this. The subject type currently must be KEY_ACE_SUBJ_STANDARD for the moment (other subject types will come along later). For subject type KEY_ACE_SUBJ_STANDARD, the following subject values are available: KEY_ACE_POSSESSOR The possessor of the key KEY_ACE_OWNER The owner of the key KEY_ACE_GROUP The key's group KEY_ACE_EVERYONE Everyone perm lists the permissions to be granted: KEY_ACE_VIEW Can view the key metadata KEY_ACE_READ Can read the key content KEY_ACE_WRITE Can update/modify the key content KEY_ACE_SEARCH Can find the key by searching/requesting KEY_ACE_LINK Can make a link to the key KEY_ACE_SET_SECURITY Can set security KEY_ACE_INVAL Can invalidate KEY_ACE_REVOKE Can revoke KEY_ACE_JOIN Can join this keyring KEY_ACE_CLEAR Can clear this keyring If an ACE already exists for the subject, then the permissions mask will be overwritten; if perm is 0, it will be deleted. Currently, the internal ACL is limited to a maximum of 16 entries. For example: int ret = keyctl_grant_permission(key, KEY_ACE_SUBJ_STANDARD, KEY_ACE_OWNER, KEY_ACE_VIEW | KEY_ACE_READ); Signed-off-by: David Howells <dhowells@redhat.com>
Diffstat (limited to 'security')
-rw-r--r--security/keys/compat.c2
-rw-r--r--security/keys/internal.h5
-rw-r--r--security/keys/keyctl.c8
-rw-r--r--security/keys/permission.c119
4 files changed, 133 insertions, 1 deletions
diff --git a/security/keys/compat.c b/security/keys/compat.c
index a53e30da20c5..1eebb9a237b8 100644
--- a/security/keys/compat.c
+++ b/security/keys/compat.c
@@ -161,6 +161,8 @@ COMPAT_SYSCALL_DEFINE5(keyctl, u32, option,
case KEYCTL_MOVE:
return keyctl_keyring_move(arg2, arg3, arg4, arg5);
+ case KEYCTL_GRANT_PERMISSION:
+ return keyctl_grant_permission(arg2, arg3, arg4, arg5);
case KEYCTL_CAPABILITIES:
return keyctl_capabilities(compat_ptr(arg2), arg3);
diff --git a/security/keys/internal.h b/security/keys/internal.h
index 9375d6289bb9..5e27ebdf1937 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -342,6 +342,11 @@ static inline long keyctl_pkey_e_d_s(int op,
extern long keyctl_capabilities(unsigned char __user *_buffer, size_t buflen);
+extern long keyctl_grant_permission(key_serial_t keyid,
+ enum key_ace_subject_type type,
+ unsigned int subject,
+ unsigned int perm);
+
/*
* Debugging key validation
*/
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index c8911b430e59..aa096c4080b2 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -41,7 +41,8 @@ static const unsigned char keyrings_capabilities[2] = {
KEYCTL_CAPS0_MOVE
),
[1] = (KEYCTL_CAPS1_NS_KEYRING_NAME |
- KEYCTL_CAPS1_NS_KEY_TAG),
+ KEYCTL_CAPS1_NS_KEY_TAG |
+ KEYCTL_CAPS1_ACL_ALTERABLE),
};
static int key_get_type_from_user(char *type,
@@ -1891,6 +1892,11 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
(key_serial_t)arg3,
(key_serial_t)arg4,
(unsigned int)arg5);
+ case KEYCTL_GRANT_PERMISSION:
+ return keyctl_grant_permission((key_serial_t)arg2,
+ (enum key_ace_subject_type)arg3,
+ (unsigned int)arg4,
+ (unsigned int)arg5);
case KEYCTL_CAPABILITIES:
return keyctl_capabilities((unsigned char __user *)arg2, (size_t)arg3);
diff --git a/security/keys/permission.c b/security/keys/permission.c
index e3237bb2e970..11655a827ba1 100644
--- a/security/keys/permission.c
+++ b/security/keys/permission.c
@@ -278,3 +278,122 @@ long key_set_acl(struct key *key, struct key_acl *acl)
key_put_acl(acl);
return 0;
}
+
+/*
+ * Allocate a new ACL with an extra ACE slot.
+ */
+static struct key_acl *key_alloc_acl(const struct key_acl *old_acl, int nr, int skip)
+{
+ struct key_acl *acl;
+ int nr_ace, i, j = 0;
+
+ nr_ace = old_acl->nr_ace + nr;
+ if (nr_ace > 16)
+ return ERR_PTR(-EINVAL);
+
+ acl = kzalloc(struct_size(acl, aces, nr_ace), GFP_KERNEL);
+ if (!acl)
+ return ERR_PTR(-ENOMEM);
+
+ refcount_set(&acl->usage, 1);
+ acl->nr_ace = nr_ace;
+ for (i = 0; i < old_acl->nr_ace; i++) {
+ if (i == skip)
+ continue;
+ acl->aces[j] = old_acl->aces[i];
+ j++;
+ }
+ return acl;
+}
+
+/*
+ * Generate the revised ACL.
+ */
+static long key_change_acl(struct key *key, struct key_ace *new_ace)
+{
+ struct key_acl *acl, *old;
+ int i;
+
+ old = rcu_dereference_protected(key->acl, lockdep_is_held(&key->sem));
+
+ for (i = 0; i < old->nr_ace; i++)
+ if (old->aces[i].type == new_ace->type &&
+ old->aces[i].subject_id == new_ace->subject_id)
+ goto found_match;
+
+ if (new_ace->perm == 0)
+ return 0; /* No permissions to remove. Add deny record? */
+
+ acl = key_alloc_acl(old, 1, -1);
+ if (IS_ERR(acl))
+ return PTR_ERR(acl);
+ acl->aces[i] = *new_ace;
+ goto change;
+
+found_match:
+ if (new_ace->perm == 0)
+ goto delete_ace;
+ if (new_ace->perm == old->aces[i].perm)
+ return 0;
+ acl = key_alloc_acl(old, 0, -1);
+ if (IS_ERR(acl))
+ return PTR_ERR(acl);
+ acl->aces[i].perm = new_ace->perm;
+ goto change;
+
+delete_ace:
+ acl = key_alloc_acl(old, -1, i);
+ if (IS_ERR(acl))
+ return PTR_ERR(acl);
+ goto change;
+
+change:
+ return key_set_acl(key, acl);
+}
+
+/*
+ * Add, alter or remove (if perm == 0) an ACE in a key's ACL.
+ */
+long keyctl_grant_permission(key_serial_t keyid,
+ enum key_ace_subject_type type,
+ unsigned int subject,
+ unsigned int perm)
+{
+ struct key_ace new_ace;
+ struct key *key;
+ key_ref_t key_ref;
+ long ret;
+
+ new_ace.type = type;
+ new_ace.perm = perm;
+
+ switch (type) {
+ case KEY_ACE_SUBJ_STANDARD:
+ if (subject >= nr__key_ace_standard_subject)
+ return -ENOENT;
+ new_ace.subject_id = subject;
+ break;
+
+ default:
+ return -ENOENT;
+ }
+
+ key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_NEED_SETSEC);
+ if (IS_ERR(key_ref)) {
+ ret = PTR_ERR(key_ref);
+ goto error;
+ }
+
+ key = key_ref_to_ptr(key_ref);
+
+ down_write(&key->sem);
+
+ /* If we're not the sysadmin, we can only change a key that we own */
+ ret = -EACCES;
+ if (capable(CAP_SYS_ADMIN) || uid_eq(key->uid, current_fsuid()))
+ ret = key_change_acl(key, &new_ace);
+ up_write(&key->sem);
+ key_put(key);
+error:
+ return ret;
+}