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authorDavid Howells <dhowells@redhat.com>2013-09-24 10:35:19 +0100
committerDavid Howells <dhowells@redhat.com>2013-09-24 10:35:19 +0100
commitf36f8c75ae2e7d4da34f4c908cebdb4aa42c977e (patch)
tree09d5dd4ffe2e8cc499f97b0fc3895b7e3f35ccbf /security/keys
parentKEYS: Implement a big key type that can save to tmpfs (diff)
downloadlinux-dev-f36f8c75ae2e7d4da34f4c908cebdb4aa42c977e.tar.xz
linux-dev-f36f8c75ae2e7d4da34f4c908cebdb4aa42c977e.zip
KEYS: Add per-user_namespace registers for persistent per-UID kerberos caches
Add support for per-user_namespace registers of persistent per-UID kerberos caches held within the kernel. This allows the kerberos cache to be retained beyond the life of all a user's processes so that the user's cron jobs can work. The kerberos cache is envisioned as a keyring/key tree looking something like: struct user_namespace \___ .krb_cache keyring - The register \___ _krb.0 keyring - Root's Kerberos cache \___ _krb.5000 keyring - User 5000's Kerberos cache \___ _krb.5001 keyring - User 5001's Kerberos cache \___ tkt785 big_key - A ccache blob \___ tkt12345 big_key - Another ccache blob Or possibly: struct user_namespace \___ .krb_cache keyring - The register \___ _krb.0 keyring - Root's Kerberos cache \___ _krb.5000 keyring - User 5000's Kerberos cache \___ _krb.5001 keyring - User 5001's Kerberos cache \___ tkt785 keyring - A ccache \___ krbtgt/REDHAT.COM@REDHAT.COM big_key \___ http/REDHAT.COM@REDHAT.COM user \___ afs/REDHAT.COM@REDHAT.COM user \___ nfs/REDHAT.COM@REDHAT.COM user \___ krbtgt/KERNEL.ORG@KERNEL.ORG big_key \___ http/KERNEL.ORG@KERNEL.ORG big_key What goes into a particular Kerberos cache is entirely up to userspace. Kernel support is limited to giving you the Kerberos cache keyring that you want. The user asks for their Kerberos cache by: krb_cache = keyctl_get_krbcache(uid, dest_keyring); The uid is -1 or the user's own UID for the user's own cache or the uid of some other user's cache (requires CAP_SETUID). This permits rpc.gssd or whatever to mess with the cache. The cache returned is a keyring named "_krb.<uid>" that the possessor can read, search, clear, invalidate, unlink from and add links to. Active LSMs get a chance to rule on whether the caller is permitted to make a link. Each uid's cache keyring is created when it first accessed and is given a timeout that is extended each time this function is called so that the keyring goes away after a while. The timeout is configurable by sysctl but defaults to three days. Each user_namespace struct gets a lazily-created keyring that serves as the register. The cache keyrings are added to it. This means that standard key search and garbage collection facilities are available. The user_namespace struct's register goes away when it does and anything left in it is then automatically gc'd. Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Simo Sorce <simo@redhat.com> cc: Serge E. Hallyn <serge.hallyn@ubuntu.com> cc: Eric W. Biederman <ebiederm@xmission.com>
Diffstat (limited to 'security/keys')
-rw-r--r--security/keys/Kconfig17
-rw-r--r--security/keys/Makefile1
-rw-r--r--security/keys/compat.c3
-rw-r--r--security/keys/internal.h9
-rw-r--r--security/keys/keyctl.c3
-rw-r--r--security/keys/persistent.c169
-rw-r--r--security/keys/sysctl.c11
7 files changed, 213 insertions, 0 deletions
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index b56362275ec8..53d8748c9564 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -20,6 +20,23 @@ config KEYS
If you are unsure as to whether this is required, answer N.
+config PERSISTENT_KEYRINGS
+ bool "Enable register of persistent per-UID keyrings"
+ depends on KEYS
+ help
+ This option provides a register of persistent per-UID keyrings,
+ primarily aimed at Kerberos key storage. The keyrings are persistent
+ in the sense that they stay around after all processes of that UID
+ have exited, not that they survive the machine being rebooted.
+
+ A particular keyring may be accessed by either the user whose keyring
+ it is or by a process with administrative privileges. The active
+ LSMs gets to rule on which admin-level processes get to access the
+ cache.
+
+ Keyrings are created and added into the register upon demand and get
+ removed if they expire (a default timeout is set upon creation).
+
config BIG_KEYS
tristate "Large payload keys"
depends on KEYS
diff --git a/security/keys/Makefile b/security/keys/Makefile
index c487c77a00be..dfb3a7bededf 100644
--- a/security/keys/Makefile
+++ b/security/keys/Makefile
@@ -18,6 +18,7 @@ obj-y := \
obj-$(CONFIG_KEYS_COMPAT) += compat.o
obj-$(CONFIG_PROC_FS) += proc.o
obj-$(CONFIG_SYSCTL) += sysctl.o
+obj-$(CONFIG_PERSISTENT_KEYRINGS) += persistent.o
#
# Key types
diff --git a/security/keys/compat.c b/security/keys/compat.c
index d65fa7fa29ba..bbd32c729dbb 100644
--- a/security/keys/compat.c
+++ b/security/keys/compat.c
@@ -138,6 +138,9 @@ asmlinkage long compat_sys_keyctl(u32 option,
case KEYCTL_INVALIDATE:
return keyctl_invalidate_key(arg2);
+ case KEYCTL_GET_PERSISTENT:
+ return keyctl_get_persistent(arg2, arg3);
+
default:
return -EOPNOTSUPP;
}
diff --git a/security/keys/internal.h b/security/keys/internal.h
index 581c6f688352..80b2aac4f50c 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -255,6 +255,15 @@ extern long keyctl_invalidate_key(key_serial_t);
extern long keyctl_instantiate_key_common(key_serial_t,
const struct iovec *,
unsigned, size_t, key_serial_t);
+#ifdef CONFIG_PERSISTENT_KEYRINGS
+extern long keyctl_get_persistent(uid_t, key_serial_t);
+extern unsigned persistent_keyring_expiry;
+#else
+static inline long keyctl_get_persistent(uid_t uid, key_serial_t destring)
+{
+ return -EOPNOTSUPP;
+}
+#endif
/*
* Debugging key validation
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 33cfd27b4de2..cee72ce64222 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1667,6 +1667,9 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
case KEYCTL_INVALIDATE:
return keyctl_invalidate_key((key_serial_t) arg2);
+ case KEYCTL_GET_PERSISTENT:
+ return keyctl_get_persistent((uid_t)arg2, (key_serial_t)arg3);
+
default:
return -EOPNOTSUPP;
}
diff --git a/security/keys/persistent.c b/security/keys/persistent.c
new file mode 100644
index 000000000000..82f4957a7acf
--- /dev/null
+++ b/security/keys/persistent.c
@@ -0,0 +1,169 @@
+/* General persistent per-UID keyrings register
+ *
+ * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/user_namespace.h>
+#include "internal.h"
+
+unsigned persistent_keyring_expiry = 3 * 24 * 3600; /* Expire after 3 days of non-use */
+
+/*
+ * Create the persistent keyring register for the current user namespace.
+ *
+ * Called with the namespace's sem locked for writing.
+ */
+static int key_create_persistent_register(struct user_namespace *ns)
+{
+ struct key *reg = keyring_alloc(".persistent_register",
+ KUIDT_INIT(0), KGIDT_INIT(0),
+ current_cred(),
+ ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
+ KEY_USR_VIEW | KEY_USR_READ),
+ KEY_ALLOC_NOT_IN_QUOTA, NULL);
+ if (IS_ERR(reg))
+ return PTR_ERR(reg);
+
+ ns->persistent_keyring_register = reg;
+ return 0;
+}
+
+/*
+ * Create the persistent keyring for the specified user.
+ *
+ * Called with the namespace's sem locked for writing.
+ */
+static key_ref_t key_create_persistent(struct user_namespace *ns, kuid_t uid,
+ struct keyring_index_key *index_key)
+{
+ struct key *persistent;
+ key_ref_t reg_ref, persistent_ref;
+
+ if (!ns->persistent_keyring_register) {
+ long err = key_create_persistent_register(ns);
+ if (err < 0)
+ return ERR_PTR(err);
+ } else {
+ reg_ref = make_key_ref(ns->persistent_keyring_register, true);
+ persistent_ref = find_key_to_update(reg_ref, index_key);
+ if (persistent_ref)
+ return persistent_ref;
+ }
+
+ persistent = keyring_alloc(index_key->description,
+ uid, INVALID_GID, current_cred(),
+ ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
+ KEY_USR_VIEW | KEY_USR_READ),
+ KEY_ALLOC_NOT_IN_QUOTA,
+ ns->persistent_keyring_register);
+ if (IS_ERR(persistent))
+ return ERR_CAST(persistent);
+
+ return make_key_ref(persistent, true);
+}
+
+/*
+ * Get the persistent keyring for a specific UID and link it to the nominated
+ * keyring.
+ */
+static long key_get_persistent(struct user_namespace *ns, kuid_t uid,
+ key_ref_t dest_ref)
+{
+ struct keyring_index_key index_key;
+ struct key *persistent;
+ key_ref_t reg_ref, persistent_ref;
+ char buf[32];
+ long ret;
+
+ /* Look in the register if it exists */
+ index_key.type = &key_type_keyring;
+ index_key.description = buf;
+ index_key.desc_len = sprintf(buf, "_persistent.%u", from_kuid(ns, uid));
+
+ if (ns->persistent_keyring_register) {
+ reg_ref = make_key_ref(ns->persistent_keyring_register, true);
+ down_read(&ns->persistent_keyring_register_sem);
+ persistent_ref = find_key_to_update(reg_ref, &index_key);
+ up_read(&ns->persistent_keyring_register_sem);
+
+ if (persistent_ref)
+ goto found;
+ }
+
+ /* It wasn't in the register, so we'll need to create it. We might
+ * also need to create the register.
+ */
+ down_write(&ns->persistent_keyring_register_sem);
+ persistent_ref = key_create_persistent(ns, uid, &index_key);
+ up_write(&ns->persistent_keyring_register_sem);
+ if (!IS_ERR(persistent_ref))
+ goto found;
+
+ return PTR_ERR(persistent_ref);
+
+found:
+ ret = key_task_permission(persistent_ref, current_cred(), KEY_LINK);
+ if (ret == 0) {
+ persistent = key_ref_to_ptr(persistent_ref);
+ ret = key_link(key_ref_to_ptr(dest_ref), persistent);
+ if (ret == 0) {
+ key_set_timeout(persistent, persistent_keyring_expiry);
+ ret = persistent->serial;
+ }
+ }
+
+ key_ref_put(persistent_ref);
+ return ret;
+}
+
+/*
+ * Get the persistent keyring for a specific UID and link it to the nominated
+ * keyring.
+ */
+long keyctl_get_persistent(uid_t _uid, key_serial_t destid)
+{
+ struct user_namespace *ns = current_user_ns();
+ key_ref_t dest_ref;
+ kuid_t uid;
+ long ret;
+
+ /* -1 indicates the current user */
+ if (_uid == (uid_t)-1) {
+ uid = current_uid();
+ } else {
+ uid = make_kuid(ns, _uid);
+ if (!uid_valid(uid))
+ return -EINVAL;
+
+ /* You can only see your own persistent cache if you're not
+ * sufficiently privileged.
+ */
+ if (uid_eq(uid, current_uid()) &&
+ uid_eq(uid, current_suid()) &&
+ uid_eq(uid, current_euid()) &&
+ uid_eq(uid, current_fsuid()) &&
+ !ns_capable(ns, CAP_SETUID))
+ return -EPERM;
+ }
+
+ /* There must be a destination keyring */
+ dest_ref = lookup_user_key(destid, KEY_LOOKUP_CREATE, KEY_WRITE);
+ if (IS_ERR(dest_ref))
+ return PTR_ERR(dest_ref);
+ if (key_ref_to_ptr(dest_ref)->type != &key_type_keyring) {
+ ret = -ENOTDIR;
+ goto out_put_dest;
+ }
+
+ ret = key_get_persistent(ns, uid, dest_ref);
+
+out_put_dest:
+ key_ref_put(dest_ref);
+ return ret;
+}
diff --git a/security/keys/sysctl.c b/security/keys/sysctl.c
index ee32d181764a..8c0af08760c8 100644
--- a/security/keys/sysctl.c
+++ b/security/keys/sysctl.c
@@ -61,5 +61,16 @@ ctl_table key_sysctls[] = {
.extra1 = (void *) &zero,
.extra2 = (void *) &max,
},
+#ifdef CONFIG_PERSISTENT_KEYRINGS
+ {
+ .procname = "persistent_keyring_expiry",
+ .data = &persistent_keyring_expiry,
+ .maxlen = sizeof(unsigned),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = (void *) &zero,
+ .extra2 = (void *) &max,
+ },
+#endif
{ }
};