userns: security: make capabilities relative to the user namespace
- Introduce ns_capable to test for a capability in a non-default
user namespace.
- Teach cap_capable to handle capabilities in a non-default
user namespace.
The motivation is to get to the unprivileged creation of new
namespaces. It looks like this gets us 90% of the way there, with
only potential uid confusion issues left.
I still need to handle getting all caps after creation but otherwise I
think I have a good starter patch that achieves all of your goals.
Changelog:
11/05/2010: [serge] add apparmor
12/14/2010: [serge] fix capabilities to created user namespaces
Without this, if user serge creates a user_ns, he won't have
capabilities to the user_ns he created. THis is because we
were first checking whether his effective caps had the caps
he needed and returning -EPERM if not, and THEN checking whether
he was the creator. Reverse those checks.
12/16/2010: [serge] security_real_capable needs ns argument in !security case
01/11/2011: [serge] add task_ns_capable helper
01/11/2011: [serge] add nsown_capable() helper per Bastian Blank suggestion
02/16/2011: [serge] fix a logic bug: the root user is always creator of
init_user_ns, but should not always have capabilities to
it! Fix the check in cap_capable().
02/21/2011: Add the required user_ns parameter to security_capable,
fixing a compile failure.
02/23/2011: Convert some macros to functions as per akpm comments. Some
couldn't be converted because we can't easily forward-declare
them (they are inline if !SECURITY, extern if SECURITY). Add
a current_user_ns function so we can use it in capability.h
without #including cred.h. Move all forward declarations
together to the top of the #ifdef __KERNEL__ section, and use
kernel-doc format.
02/23/2011: Per dhowells, clean up comment in cap_capable().
02/23/2011: Per akpm, remove unreachable 'return -EPERM' in cap_capable.
(Original written and signed off by Eric; latest, modified version
acked by him)
[akpm@linux-foundation.org: fix build]
[akpm@linux-foundation.org: export current_user_ns() for ecryptfs]
[serge.hallyn@canonical.com: remove unneeded extra argument in selinux's task_has_capability]
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Daniel Lezcano <daniel.lezcano@free.fr>
Acked-by: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index c85438a..a8a277a 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -369,7 +369,7 @@
u8 *data = (u8*) buf;
/* Several chips lock up trying to read undefined config space */
- if (security_capable(filp->f_cred, CAP_SYS_ADMIN) == 0) {
+ if (security_capable(&init_user_ns, filp->f_cred, CAP_SYS_ADMIN) == 0) {
size = dev->cfg_size;
} else if (dev->hdr_type == PCI_HEADER_TYPE_CARDBUS) {
size = 128;
diff --git a/include/linux/capability.h b/include/linux/capability.h
index fb16a36..7c9c829 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -368,6 +368,17 @@
#ifdef __KERNEL__
+struct dentry;
+struct user_namespace;
+
+extern struct user_namespace init_user_ns;
+
+struct user_namespace *current_user_ns(void);
+
+extern const kernel_cap_t __cap_empty_set;
+extern const kernel_cap_t __cap_full_set;
+extern const kernel_cap_t __cap_init_eff_set;
+
/*
* Internal kernel functions only
*/
@@ -530,10 +541,6 @@
cap_intersect(permitted, __cap_nfsd_set));
}
-extern const kernel_cap_t __cap_empty_set;
-extern const kernel_cap_t __cap_full_set;
-extern const kernel_cap_t __cap_init_eff_set;
-
/**
* has_capability - Determine if a task has a superior capability available
* @t: The task in question
@@ -544,7 +551,7 @@
*
* Note that this does not set PF_SUPERPRIV on the task.
*/
-#define has_capability(t, cap) (security_real_capable((t), (cap)) == 0)
+#define has_capability(t, cap) (security_real_capable((t), &init_user_ns, (cap)) == 0)
/**
* has_capability_noaudit - Determine if a task has a superior capability available (unaudited)
@@ -558,12 +565,25 @@
* Note that this does not set PF_SUPERPRIV on the task.
*/
#define has_capability_noaudit(t, cap) \
- (security_real_capable_noaudit((t), (cap)) == 0)
+ (security_real_capable_noaudit((t), &init_user_ns, (cap)) == 0)
-extern int capable(int cap);
+extern bool capable(int cap);
+extern bool ns_capable(struct user_namespace *ns, int cap);
+extern bool task_ns_capable(struct task_struct *t, int cap);
+
+/**
+ * nsown_capable - Check superior capability to one's own user_ns
+ * @cap: The capability in question
+ *
+ * Return true if the current task has the given superior capability
+ * targeted at its own user namespace.
+ */
+static inline bool nsown_capable(int cap)
+{
+ return ns_capable(current_user_ns(), cap);
+}
/* audit system wants to get cap info from files as well */
-struct dentry;
extern int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps);
#endif /* __KERNEL__ */
diff --git a/include/linux/cred.h b/include/linux/cred.h
index 4aaeab3..9aeeb0b 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -354,9 +354,11 @@
#define current_fsgid() (current_cred_xxx(fsgid))
#define current_cap() (current_cred_xxx(cap_effective))
#define current_user() (current_cred_xxx(user))
-#define current_user_ns() (current_cred_xxx(user)->user_ns)
+#define _current_user_ns() (current_cred_xxx(user)->user_ns)
#define current_security() (current_cred_xxx(security))
+extern struct user_namespace *current_user_ns(void);
+
#define current_uid_gid(_uid, _gid) \
do { \
const struct cred *__cred; \
diff --git a/include/linux/security.h b/include/linux/security.h
index 56cac52..ca02f17 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -47,13 +47,14 @@
struct ctl_table;
struct audit_krule;
+struct user_namespace;
/*
* These functions are in security/capability.c and are used
* as the default capabilities functions
*/
extern int cap_capable(struct task_struct *tsk, const struct cred *cred,
- int cap, int audit);
+ struct user_namespace *ns, int cap, int audit);
extern int cap_settime(const struct timespec *ts, const struct timezone *tz);
extern int cap_ptrace_access_check(struct task_struct *child, unsigned int mode);
extern int cap_ptrace_traceme(struct task_struct *parent);
@@ -1262,6 +1263,7 @@
* credentials.
* @tsk contains the task_struct for the process.
* @cred contains the credentials to use.
+ * @ns contains the user namespace we want the capability in
* @cap contains the capability <include/linux/capability.h>.
* @audit: Whether to write an audit message or not
* Return 0 if the capability is granted for @tsk.
@@ -1384,7 +1386,7 @@
const kernel_cap_t *inheritable,
const kernel_cap_t *permitted);
int (*capable) (struct task_struct *tsk, const struct cred *cred,
- int cap, int audit);
+ struct user_namespace *ns, int cap, int audit);
int (*quotactl) (int cmds, int type, int id, struct super_block *sb);
int (*quota_on) (struct dentry *dentry);
int (*syslog) (int type);
@@ -1665,9 +1667,12 @@
const kernel_cap_t *effective,
const kernel_cap_t *inheritable,
const kernel_cap_t *permitted);
-int security_capable(const struct cred *cred, int cap);
-int security_real_capable(struct task_struct *tsk, int cap);
-int security_real_capable_noaudit(struct task_struct *tsk, int cap);
+int security_capable(struct user_namespace *ns, const struct cred *cred,
+ int cap);
+int security_real_capable(struct task_struct *tsk, struct user_namespace *ns,
+ int cap);
+int security_real_capable_noaudit(struct task_struct *tsk,
+ struct user_namespace *ns, int cap);
int security_quotactl(int cmds, int type, int id, struct super_block *sb);
int security_quota_on(struct dentry *dentry);
int security_syslog(int type);
@@ -1860,28 +1865,29 @@
return cap_capset(new, old, effective, inheritable, permitted);
}
-static inline int security_capable(const struct cred *cred, int cap)
+static inline int security_capable(struct user_namespace *ns,
+ const struct cred *cred, int cap)
{
- return cap_capable(current, cred, cap, SECURITY_CAP_AUDIT);
+ return cap_capable(current, cred, ns, cap, SECURITY_CAP_AUDIT);
}
-static inline int security_real_capable(struct task_struct *tsk, int cap)
+static inline int security_real_capable(struct task_struct *tsk, struct user_namespace *ns, int cap)
{
int ret;
rcu_read_lock();
- ret = cap_capable(tsk, __task_cred(tsk), cap, SECURITY_CAP_AUDIT);
+ ret = cap_capable(tsk, __task_cred(tsk), ns, cap, SECURITY_CAP_AUDIT);
rcu_read_unlock();
return ret;
}
static inline
-int security_real_capable_noaudit(struct task_struct *tsk, int cap)
+int security_real_capable_noaudit(struct task_struct *tsk, struct user_namespace *ns, int cap)
{
int ret;
rcu_read_lock();
- ret = cap_capable(tsk, __task_cred(tsk), cap,
+ ret = cap_capable(tsk, __task_cred(tsk), ns, cap,
SECURITY_CAP_NOAUDIT);
rcu_read_unlock();
return ret;
diff --git a/kernel/capability.c b/kernel/capability.c
index 9e9385f..0a3d2c8 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -14,6 +14,7 @@
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/pid_namespace.h>
+#include <linux/user_namespace.h>
#include <asm/uaccess.h>
/*
@@ -299,17 +300,48 @@
* This sets PF_SUPERPRIV on the task if the capability is available on the
* assumption that it's about to be used.
*/
-int capable(int cap)
+bool capable(int cap)
+{
+ return ns_capable(&init_user_ns, cap);
+}
+EXPORT_SYMBOL(capable);
+
+/**
+ * ns_capable - Determine if the current task has a superior capability in effect
+ * @ns: The usernamespace we want the capability in
+ * @cap: The capability to be tested for
+ *
+ * Return true if the current task has the given superior capability currently
+ * available for use, false if not.
+ *
+ * This sets PF_SUPERPRIV on the task if the capability is available on the
+ * assumption that it's about to be used.
+ */
+bool ns_capable(struct user_namespace *ns, int cap)
{
if (unlikely(!cap_valid(cap))) {
printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap);
BUG();
}
- if (security_capable(current_cred(), cap) == 0) {
+ if (security_capable(ns, current_cred(), cap) == 0) {
current->flags |= PF_SUPERPRIV;
- return 1;
+ return true;
}
- return 0;
+ return false;
}
-EXPORT_SYMBOL(capable);
+EXPORT_SYMBOL(ns_capable);
+
+/**
+ * task_ns_capable - Determine whether current task has a superior
+ * capability targeted at a specific task's user namespace.
+ * @t: The task whose user namespace is targeted.
+ * @cap: The capability in question.
+ *
+ * Return true if it does, false otherwise.
+ */
+bool task_ns_capable(struct task_struct *t, int cap)
+{
+ return ns_capable(task_cred_xxx(t, user)->user_ns, cap);
+}
+EXPORT_SYMBOL(task_ns_capable);
diff --git a/kernel/cred.c b/kernel/cred.c
index 2343c132..5557b55 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -741,6 +741,12 @@
}
EXPORT_SYMBOL(set_create_files_as);
+struct user_namespace *current_user_ns(void)
+{
+ return _current_user_ns();
+}
+EXPORT_SYMBOL(current_user_ns);
+
#ifdef CONFIG_DEBUG_CREDENTIALS
bool creds_are_invalid(const struct cred *cred)
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index d21a427..ae3a698 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -22,6 +22,7 @@
#include <linux/ctype.h>
#include <linux/sysctl.h>
#include <linux/audit.h>
+#include <linux/user_namespace.h>
#include <net/sock.h>
#include "include/apparmor.h"
@@ -136,11 +137,11 @@
}
static int apparmor_capable(struct task_struct *task, const struct cred *cred,
- int cap, int audit)
+ struct user_namespace *ns, int cap, int audit)
{
struct aa_profile *profile;
/* cap_capable returns 0 on success, else -EPERM */
- int error = cap_capable(task, cred, cap, audit);
+ int error = cap_capable(task, cred, ns, cap, audit);
if (!error) {
profile = aa_cred_profile(cred);
if (!unconfined(profile))
diff --git a/security/commoncap.c b/security/commoncap.c
index 49c57fd..43a205b 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -27,6 +27,7 @@
#include <linux/sched.h>
#include <linux/prctl.h>
#include <linux/securebits.h>
+#include <linux/user_namespace.h>
/*
* If a non-root user executes a setuid-root binary in
@@ -67,6 +68,7 @@
* cap_capable - Determine whether a task has a particular effective capability
* @tsk: The task to query
* @cred: The credentials to use
+ * @ns: The user namespace in which we need the capability
* @cap: The capability to check for
* @audit: Whether to write an audit message or not
*
@@ -78,10 +80,30 @@
* cap_has_capability() returns 0 when a task has a capability, but the
* kernel's capable() and has_capability() returns 1 for this case.
*/
-int cap_capable(struct task_struct *tsk, const struct cred *cred, int cap,
- int audit)
+int cap_capable(struct task_struct *tsk, const struct cred *cred,
+ struct user_namespace *targ_ns, int cap, int audit)
{
- return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
+ for (;;) {
+ /* The creator of the user namespace has all caps. */
+ if (targ_ns != &init_user_ns && targ_ns->creator == cred->user)
+ return 0;
+
+ /* Do we have the necessary capabilities? */
+ if (targ_ns == cred->user->user_ns)
+ return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
+
+ /* Have we tried all of the parent namespaces? */
+ if (targ_ns == &init_user_ns)
+ return -EPERM;
+
+ /*
+ *If you have a capability in a parent user ns, then you have
+ * it over all children user namespaces as well.
+ */
+ targ_ns = targ_ns->creator->user_ns;
+ }
+
+ /* We never get here */
}
/**
@@ -176,7 +198,8 @@
/* they are so limited unless the current task has the CAP_SETPCAP
* capability
*/
- if (cap_capable(current, current_cred(), CAP_SETPCAP,
+ if (cap_capable(current, current_cred(),
+ current_cred()->user->user_ns, CAP_SETPCAP,
SECURITY_CAP_AUDIT) == 0)
return 0;
return 1;
@@ -828,7 +851,8 @@
& (new->securebits ^ arg2)) /*[1]*/
|| ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
|| (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
- || (cap_capable(current, current_cred(), CAP_SETPCAP,
+ || (cap_capable(current, current_cred(),
+ current_cred()->user->user_ns, CAP_SETPCAP,
SECURITY_CAP_AUDIT) != 0) /*[4]*/
/*
* [1] no changing of bits that are locked
@@ -893,7 +917,7 @@
{
int cap_sys_admin = 0;
- if (cap_capable(current, current_cred(), CAP_SYS_ADMIN,
+ if (cap_capable(current, current_cred(), &init_user_ns, CAP_SYS_ADMIN,
SECURITY_CAP_NOAUDIT) == 0)
cap_sys_admin = 1;
return __vm_enough_memory(mm, pages, cap_sys_admin);
@@ -920,7 +944,7 @@
int ret = 0;
if (addr < dac_mmap_min_addr) {
- ret = cap_capable(current, current_cred(), CAP_SYS_RAWIO,
+ ret = cap_capable(current, current_cred(), &init_user_ns, CAP_SYS_RAWIO,
SECURITY_CAP_AUDIT);
/* set PF_SUPERPRIV if it turns out we allow the low mmap */
if (ret == 0)
diff --git a/security/security.c b/security/security.c
index 9187665..1011423 100644
--- a/security/security.c
+++ b/security/security.c
@@ -154,29 +154,33 @@
effective, inheritable, permitted);
}
-int security_capable(const struct cred *cred, int cap)
+int security_capable(struct user_namespace *ns, const struct cred *cred,
+ int cap)
{
- return security_ops->capable(current, cred, cap, SECURITY_CAP_AUDIT);
+ return security_ops->capable(current, cred, ns, cap,
+ SECURITY_CAP_AUDIT);
}
-int security_real_capable(struct task_struct *tsk, int cap)
+int security_real_capable(struct task_struct *tsk, struct user_namespace *ns,
+ int cap)
{
const struct cred *cred;
int ret;
cred = get_task_cred(tsk);
- ret = security_ops->capable(tsk, cred, cap, SECURITY_CAP_AUDIT);
+ ret = security_ops->capable(tsk, cred, ns, cap, SECURITY_CAP_AUDIT);
put_cred(cred);
return ret;
}
-int security_real_capable_noaudit(struct task_struct *tsk, int cap)
+int security_real_capable_noaudit(struct task_struct *tsk,
+ struct user_namespace *ns, int cap)
{
const struct cred *cred;
int ret;
cred = get_task_cred(tsk);
- ret = security_ops->capable(tsk, cred, cap, SECURITY_CAP_NOAUDIT);
+ ret = security_ops->capable(tsk, cred, ns, cap, SECURITY_CAP_NOAUDIT);
put_cred(cred);
return ret;
}
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 6475e1f..c67f863 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -79,6 +79,7 @@
#include <linux/mutex.h>
#include <linux/posix-timers.h>
#include <linux/syslog.h>
+#include <linux/user_namespace.h>
#include "avc.h"
#include "objsec.h"
@@ -1846,11 +1847,11 @@
*/
static int selinux_capable(struct task_struct *tsk, const struct cred *cred,
- int cap, int audit)
+ struct user_namespace *ns, int cap, int audit)
{
int rc;
- rc = cap_capable(tsk, cred, cap, audit);
+ rc = cap_capable(tsk, cred, ns, cap, audit);
if (rc)
return rc;
@@ -1931,7 +1932,8 @@
{
int rc, cap_sys_admin = 0;
- rc = selinux_capable(current, current_cred(), CAP_SYS_ADMIN,
+ rc = selinux_capable(current, current_cred(),
+ &init_user_ns, CAP_SYS_ADMIN,
SECURITY_CAP_NOAUDIT);
if (rc == 0)
cap_sys_admin = 1;
@@ -2834,7 +2836,8 @@
* and lack of permission just means that we fall back to the
* in-core context value, not a denial.
*/
- error = selinux_capable(current, current_cred(), CAP_MAC_ADMIN,
+ error = selinux_capable(current, current_cred(),
+ &init_user_ns, CAP_MAC_ADMIN,
SECURITY_CAP_NOAUDIT);
if (!error)
error = security_sid_to_context_force(isec->sid, &context,
@@ -2968,7 +2971,7 @@
case KDSKBENT:
case KDSKBSENT:
error = task_has_capability(current, cred, CAP_SYS_TTY_CONFIG,
- SECURITY_CAP_AUDIT);
+ SECURITY_CAP_AUDIT);
break;
/* default case assumes that the command will go