diff options
author | Serge E. Hallyn <serge@hallyn.com> | 2011-03-23 23:43:17 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-03-24 02:47:02 (GMT) |
commit | 3486740a4f32a6a466f5ac931654d154790ba648 (patch) | |
tree | ac5d968a66057fa84933b8f89fd3e916270dffed /security | |
parent | 59607db367c57f515183cb203642291bb14d9c40 (diff) | |
download | linux-3486740a4f32a6a466f5ac931654d154790ba648.tar.xz |
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>
Diffstat (limited to 'security')
-rw-r--r-- | security/apparmor/lsm.c | 5 | ||||
-rw-r--r-- | security/commoncap.c | 38 | ||||
-rw-r--r-- | security/security.c | 16 | ||||
-rw-r--r-- | security/selinux/hooks.c | 13 |
4 files changed, 52 insertions, 20 deletions
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_capget(struct task_struct *target, kernel_cap_t *effective, } 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 @@ EXPORT_SYMBOL(cap_netlink_recv); * 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 @@ EXPORT_SYMBOL(cap_netlink_recv); * 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 @@ static inline int cap_inh_is_capped(void) /* 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 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, & (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_vm_enough_memory(struct mm_struct *mm, long pages) { 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 cap_file_mmap(struct file *file, unsigned long reqprot, 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 @@ int security_capset(struct cred *new, const struct cred *old, 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_capset(struct cred *new, const struct cred *old, */ 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 @@ static int selinux_vm_enough_memory(struct mm_struct *mm, long pages) { 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 @@ static int selinux_inode_getsecurity(const struct inode *inode, const char *name * 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 @@ static int selinux_file_ioctl(struct file *file, unsigned int cmd, 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 |