Re: [PATCH v4 01/16] ima: Add IMA namespace support
From: Stefan Berger
Date: Wed Dec 08 2021 - 09:50:40 EST
On 12/8/21 06:54, Christian Brauner wrote:
On Wed, Dec 08, 2021 at 12:29:18PM +0100, Christian Brauner wrote:
On Tue, Dec 07, 2021 at 03:21:12PM -0500, Stefan Berger wrote:
Implement an IMA namespace data structure that gets created alongside a
user namespace with CLONE_NEWUSER. This lays down the foundation for
namespacing the different aspects of IMA (eg. IMA-audit, IMA-measurement,
IMA-appraisal).
Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
Suggested-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
---
include/linux/ima.h | 59 +++++++++++++++++
include/linux/user_namespace.h | 4 ++
init/Kconfig | 10 +++
kernel/user.c | 9 ++-
kernel/user_namespace.c | 16 +++++
security/integrity/ima/Makefile | 3 +-
security/integrity/ima/ima.h | 4 ++
security/integrity/ima/ima_init.c | 4 ++
security/integrity/ima/ima_init_ima_ns.c | 32 +++++++++
security/integrity/ima/ima_ns.c | 82 ++++++++++++++++++++++++
10 files changed, 221 insertions(+), 2 deletions(-)
create mode 100644 security/integrity/ima/ima_init_ima_ns.c
create mode 100644 security/integrity/ima/ima_ns.c
diff --git a/include/linux/ima.h b/include/linux/ima.h
index b6ab66a546ae..86d126b9ff2f 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -11,6 +11,7 @@
#include <linux/fs.h>
#include <linux/security.h>
#include <linux/kexec.h>
+#include <linux/user_namespace.h>
#include <crypto/hash_info.h>
struct linux_binprm;
@@ -210,6 +211,64 @@ static inline int ima_inode_removexattr(struct dentry *dentry,
}
#endif /* CONFIG_IMA_APPRAISE */
+struct ima_namespace {
+ struct kref kref;
+ struct user_namespace *user_ns;
+};
+
+extern struct ima_namespace init_ima_ns;
+
+#ifdef CONFIG_IMA_NS
+
+void free_ima_ns(struct kref *kref);
+
+static inline struct ima_namespace *get_ima_ns(struct ima_namespace *ns)
+{
+ if (ns)
+ kref_get(&ns->kref);
+
+ return ns;
+}
+
+static inline void put_ima_ns(struct ima_namespace *ns)
+{
+ if (ns) {
+ pr_debug("DEREF ima_ns: 0x%p ctr: %d\n", ns, kref_read(&ns->kref));
+ kref_put(&ns->kref, free_ima_ns);
+ }
+}
+
+struct ima_namespace *copy_ima_ns(struct ima_namespace *old_ns,
+ struct user_namespace *user_ns);
+
+static inline struct ima_namespace *get_current_ns(void)
+{
+ return current_user_ns()->ima_ns;
+}
+
+#else
+
+static inline struct ima_namespace *get_ima_ns(struct ima_namespace *ns)
+{
+ return ns;
+}
+
+static inline void put_ima_ns(struct ima_namespace *ns)
+{
+}
+
+static inline struct ima_namespace *copy_ima_ns(struct ima_namespace *old_ns,
+ struct user_namespace *user_ns)
+{
+ return old_ns;
+}
+
+static inline struct ima_namespace *get_current_ns(void)
+{
+ return &init_ima_ns;
+}
+#endif /* CONFIG_IMA_NS */
+
#if defined(CONFIG_IMA_APPRAISE) && defined(CONFIG_INTEGRITY_TRUSTED_KEYRING)
extern bool ima_appraise_signature(enum kernel_read_file_id func);
#else
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 33a4240e6a6f..5249db04d62b 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -36,6 +36,7 @@ struct uid_gid_map { /* 64 bytes -- 1 cache line */
#define USERNS_INIT_FLAGS USERNS_SETGROUPS_ALLOWED
struct ucounts;
+struct ima_namespace;
enum ucount_type {
UCOUNT_USER_NAMESPACES,
@@ -99,6 +100,9 @@ struct user_namespace {
#endif
struct ucounts *ucounts;
long ucount_max[UCOUNT_COUNTS];
+#ifdef CONFIG_IMA
+ struct ima_namespace *ima_ns;
+#endif
} __randomize_layout;
struct ucounts {
diff --git a/init/Kconfig b/init/Kconfig
index 11f8a845f259..27890607e8cb 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1242,6 +1242,16 @@ config NET_NS
Allow user space to create what appear to be multiple instances
of the network stack.
+config IMA_NS
+ bool "IMA namespace"
+ depends on USER_NS
+ depends on IMA
+ default y
+ help
+ Allow the creation of IMA namespaces for each user namespace.
+ Namespaced IMA enables having IMA features work separately
+ in each IMA namespace.
+
endif # NAMESPACES
config CHECKPOINT_RESTORE
diff --git a/kernel/user.c b/kernel/user.c
index e2cf8c22b539..b5dc803a033d 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -20,6 +20,10 @@
#include <linux/user_namespace.h>
#include <linux/proc_ns.h>
+#ifdef CONFIG_IMA
+extern struct ima_namespace init_ima_ns;
+#endif
+
/*
* userns count is 1 for root user, 1 for init_uts_ns,
* and 1 for... ?
@@ -55,7 +59,7 @@ struct user_namespace init_user_ns = {
},
},
},
- .ns.count = REFCOUNT_INIT(3),
+ .ns.count = REFCOUNT_INIT(4),
.owner = GLOBAL_ROOT_UID,
.group = GLOBAL_ROOT_GID,
.ns.inum = PROC_USER_INIT_INO,
@@ -67,6 +71,9 @@ struct user_namespace init_user_ns = {
.keyring_name_list = LIST_HEAD_INIT(init_user_ns.keyring_name_list),
.keyring_sem = __RWSEM_INITIALIZER(init_user_ns.keyring_sem),
#endif
+#ifdef CONFIG_IMA
+ .ima_ns = &init_ima_ns,
+#endif
};
EXPORT_SYMBOL_GPL(init_user_ns);
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 6b2e3ca7ee99..c26885343b19 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -20,6 +20,7 @@
#include <linux/fs_struct.h>
#include <linux/bsearch.h>
#include <linux/sort.h>
+#include <linux/ima.h>
static struct kmem_cache *user_ns_cachep __read_mostly;
static DEFINE_MUTEX(userns_state_mutex);
@@ -141,8 +142,20 @@ int create_user_ns(struct cred *new)
if (!setup_userns_sysctls(ns))
goto fail_keyring;
+#if CONFIG_IMA
+ ns->ima_ns = copy_ima_ns(parent_ns->ima_ns, ns);
+ if (IS_ERR(ns->ima_ns)) {
+ ret = PTR_ERR(ns->ima_ns);
+ goto fail_userns_sysctls;
+ }
+#endif
+
set_cred_user_ns(new, ns);
return 0;
+#if CONFIG_IMA
+fail_userns_sysctls:
+ retire_userns_sysctls(ns);
+#endif
If you rewrite copy_ima_ns() put_ima_ns() a little you can remove all
the ifdefs in here and make this patch tiny.
Make copy_ima_ns() return an int. Afaict, you can remove passing the
parent ima_ns completely but if you have to pass through the
parent_userns.
Then you can initialize new_userns->ima_ns inside of copy_ima_ns() and
the ifdef will only need to be visible inside copy_ima_ns() and not in
create_user_ns(). Similar put_ima_ns() is only called in a single place
namely kernel/user_namespace.c. Make it take a user_namespace argument
and you can remove the ifdef in __put_user_ns() for put_ima_ns() too.
So something -- COMPLETELY UNTESTED -- like the below should work:
Thanks. I did this now for v5.
Stefan