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![Christian Brauner](/assets/img/avatar_default.png)
The posix acl permission checking helpers determine whether a caller is privileged over an inode according to the acls associated with the inode. Add helpers that make it possible to handle acls on idmapped mounts. The vfs and the filesystems targeted by this first iteration make use of posix_acl_fix_xattr_from_user() and posix_acl_fix_xattr_to_user() to translate basic posix access and default permissions such as the ACL_USER and ACL_GROUP type according to the initial user namespace (or the superblock's user namespace) to and from the caller's current user namespace. Adapt these two helpers to handle idmapped mounts whereby we either map from or into the mount's user namespace depending on in which direction we're translating. Similarly, cap_convert_nscap() is used by the vfs to translate user namespace and non-user namespace aware filesystem capabilities from the superblock's user namespace to the caller's user namespace. Enable it to handle idmapped mounts by accounting for the mount's user namespace. In addition the fileystems targeted in the first iteration of this patch series make use of the posix_acl_chmod() and, posix_acl_update_mode() helpers. Both helpers perform permission checks on the target inode. Let them handle idmapped mounts. These two helpers are called when posix acls are set by the respective filesystems to handle this case we extend the ->set() method to take an additional user namespace argument to pass the mount's user namespace down. Link: https://lore.kernel.org/r/20210121131959.646623-9-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
279 lines
8.2 KiB
C
279 lines
8.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* This is <linux/capability.h>
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*
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* Andrew G. Morgan <morgan@kernel.org>
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* Alexander Kjeldaas <astor@guardian.no>
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* with help from Aleph1, Roland Buresund and Andrew Main.
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*
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* See here for the libcap library ("POSIX draft" compliance):
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*
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* ftp://www.kernel.org/pub/linux/libs/security/linux-privs/kernel-2.6/
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*/
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#ifndef _LINUX_CAPABILITY_H
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#define _LINUX_CAPABILITY_H
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#include <uapi/linux/capability.h>
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#include <linux/uidgid.h>
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#define _KERNEL_CAPABILITY_VERSION _LINUX_CAPABILITY_VERSION_3
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#define _KERNEL_CAPABILITY_U32S _LINUX_CAPABILITY_U32S_3
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extern int file_caps_enabled;
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typedef struct kernel_cap_struct {
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__u32 cap[_KERNEL_CAPABILITY_U32S];
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} kernel_cap_t;
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/* same as vfs_ns_cap_data but in cpu endian and always filled completely */
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struct cpu_vfs_cap_data {
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__u32 magic_etc;
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kernel_cap_t permitted;
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kernel_cap_t inheritable;
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kuid_t rootid;
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};
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#define _USER_CAP_HEADER_SIZE (sizeof(struct __user_cap_header_struct))
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#define _KERNEL_CAP_T_SIZE (sizeof(kernel_cap_t))
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struct file;
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struct inode;
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struct dentry;
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struct task_struct;
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struct user_namespace;
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extern const kernel_cap_t __cap_empty_set;
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extern const kernel_cap_t __cap_init_eff_set;
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/*
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* Internal kernel functions only
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*/
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#define CAP_FOR_EACH_U32(__capi) \
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for (__capi = 0; __capi < _KERNEL_CAPABILITY_U32S; ++__capi)
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/*
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* CAP_FS_MASK and CAP_NFSD_MASKS:
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*
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* The fs mask is all the privileges that fsuid==0 historically meant.
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* At one time in the past, that included CAP_MKNOD and CAP_LINUX_IMMUTABLE.
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*
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* It has never meant setting security.* and trusted.* xattrs.
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*
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* We could also define fsmask as follows:
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* 1. CAP_FS_MASK is the privilege to bypass all fs-related DAC permissions
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* 2. The security.* and trusted.* xattrs are fs-related MAC permissions
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*/
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# define CAP_FS_MASK_B0 (CAP_TO_MASK(CAP_CHOWN) \
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| CAP_TO_MASK(CAP_MKNOD) \
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| CAP_TO_MASK(CAP_DAC_OVERRIDE) \
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| CAP_TO_MASK(CAP_DAC_READ_SEARCH) \
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| CAP_TO_MASK(CAP_FOWNER) \
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| CAP_TO_MASK(CAP_FSETID))
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# define CAP_FS_MASK_B1 (CAP_TO_MASK(CAP_MAC_OVERRIDE))
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#if _KERNEL_CAPABILITY_U32S != 2
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# error Fix up hand-coded capability macro initializers
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#else /* HAND-CODED capability initializers */
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#define CAP_LAST_U32 ((_KERNEL_CAPABILITY_U32S) - 1)
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#define CAP_LAST_U32_VALID_MASK (CAP_TO_MASK(CAP_LAST_CAP + 1) -1)
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# define CAP_EMPTY_SET ((kernel_cap_t){{ 0, 0 }})
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# define CAP_FULL_SET ((kernel_cap_t){{ ~0, CAP_LAST_U32_VALID_MASK }})
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# define CAP_FS_SET ((kernel_cap_t){{ CAP_FS_MASK_B0 \
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| CAP_TO_MASK(CAP_LINUX_IMMUTABLE), \
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CAP_FS_MASK_B1 } })
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# define CAP_NFSD_SET ((kernel_cap_t){{ CAP_FS_MASK_B0 \
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| CAP_TO_MASK(CAP_SYS_RESOURCE), \
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CAP_FS_MASK_B1 } })
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#endif /* _KERNEL_CAPABILITY_U32S != 2 */
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# define cap_clear(c) do { (c) = __cap_empty_set; } while (0)
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#define cap_raise(c, flag) ((c).cap[CAP_TO_INDEX(flag)] |= CAP_TO_MASK(flag))
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#define cap_lower(c, flag) ((c).cap[CAP_TO_INDEX(flag)] &= ~CAP_TO_MASK(flag))
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#define cap_raised(c, flag) ((c).cap[CAP_TO_INDEX(flag)] & CAP_TO_MASK(flag))
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#define CAP_BOP_ALL(c, a, b, OP) \
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do { \
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unsigned __capi; \
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CAP_FOR_EACH_U32(__capi) { \
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c.cap[__capi] = a.cap[__capi] OP b.cap[__capi]; \
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} \
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} while (0)
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#define CAP_UOP_ALL(c, a, OP) \
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do { \
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unsigned __capi; \
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CAP_FOR_EACH_U32(__capi) { \
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c.cap[__capi] = OP a.cap[__capi]; \
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} \
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} while (0)
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static inline kernel_cap_t cap_combine(const kernel_cap_t a,
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const kernel_cap_t b)
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{
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kernel_cap_t dest;
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CAP_BOP_ALL(dest, a, b, |);
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return dest;
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}
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static inline kernel_cap_t cap_intersect(const kernel_cap_t a,
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const kernel_cap_t b)
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{
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kernel_cap_t dest;
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CAP_BOP_ALL(dest, a, b, &);
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return dest;
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}
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static inline kernel_cap_t cap_drop(const kernel_cap_t a,
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const kernel_cap_t drop)
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{
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kernel_cap_t dest;
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CAP_BOP_ALL(dest, a, drop, &~);
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return dest;
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}
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static inline kernel_cap_t cap_invert(const kernel_cap_t c)
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{
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kernel_cap_t dest;
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CAP_UOP_ALL(dest, c, ~);
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return dest;
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}
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static inline bool cap_isclear(const kernel_cap_t a)
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{
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unsigned __capi;
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CAP_FOR_EACH_U32(__capi) {
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if (a.cap[__capi] != 0)
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return false;
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}
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return true;
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}
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/*
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* Check if "a" is a subset of "set".
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* return true if ALL of the capabilities in "a" are also in "set"
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* cap_issubset(0101, 1111) will return true
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* return false if ANY of the capabilities in "a" are not in "set"
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* cap_issubset(1111, 0101) will return false
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*/
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static inline bool cap_issubset(const kernel_cap_t a, const kernel_cap_t set)
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{
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kernel_cap_t dest;
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dest = cap_drop(a, set);
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return cap_isclear(dest);
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}
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/* Used to decide between falling back on the old suser() or fsuser(). */
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static inline kernel_cap_t cap_drop_fs_set(const kernel_cap_t a)
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{
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const kernel_cap_t __cap_fs_set = CAP_FS_SET;
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return cap_drop(a, __cap_fs_set);
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}
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static inline kernel_cap_t cap_raise_fs_set(const kernel_cap_t a,
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const kernel_cap_t permitted)
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{
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const kernel_cap_t __cap_fs_set = CAP_FS_SET;
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return cap_combine(a,
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cap_intersect(permitted, __cap_fs_set));
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}
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static inline kernel_cap_t cap_drop_nfsd_set(const kernel_cap_t a)
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{
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const kernel_cap_t __cap_fs_set = CAP_NFSD_SET;
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return cap_drop(a, __cap_fs_set);
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}
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static inline kernel_cap_t cap_raise_nfsd_set(const kernel_cap_t a,
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const kernel_cap_t permitted)
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{
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const kernel_cap_t __cap_nfsd_set = CAP_NFSD_SET;
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return cap_combine(a,
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cap_intersect(permitted, __cap_nfsd_set));
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}
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#ifdef CONFIG_MULTIUSER
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extern bool has_capability(struct task_struct *t, int cap);
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extern bool has_ns_capability(struct task_struct *t,
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struct user_namespace *ns, int cap);
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extern bool has_capability_noaudit(struct task_struct *t, int cap);
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extern bool has_ns_capability_noaudit(struct task_struct *t,
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struct user_namespace *ns, int cap);
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extern bool capable(int cap);
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extern bool ns_capable(struct user_namespace *ns, int cap);
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extern bool ns_capable_noaudit(struct user_namespace *ns, int cap);
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extern bool ns_capable_setid(struct user_namespace *ns, int cap);
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#else
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static inline bool has_capability(struct task_struct *t, int cap)
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{
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return true;
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}
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static inline bool has_ns_capability(struct task_struct *t,
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struct user_namespace *ns, int cap)
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{
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return true;
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}
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static inline bool has_capability_noaudit(struct task_struct *t, int cap)
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{
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return true;
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}
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static inline bool has_ns_capability_noaudit(struct task_struct *t,
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struct user_namespace *ns, int cap)
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{
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return true;
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}
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static inline bool capable(int cap)
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{
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return true;
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}
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static inline bool ns_capable(struct user_namespace *ns, int cap)
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{
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return true;
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}
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static inline bool ns_capable_noaudit(struct user_namespace *ns, int cap)
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{
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return true;
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}
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static inline bool ns_capable_setid(struct user_namespace *ns, int cap)
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{
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return true;
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}
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#endif /* CONFIG_MULTIUSER */
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bool privileged_wrt_inode_uidgid(struct user_namespace *ns,
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struct user_namespace *mnt_userns,
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const struct inode *inode);
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bool capable_wrt_inode_uidgid(struct user_namespace *mnt_userns,
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const struct inode *inode, int cap);
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extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap);
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extern bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns);
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static inline bool perfmon_capable(void)
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{
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return capable(CAP_PERFMON) || capable(CAP_SYS_ADMIN);
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}
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static inline bool bpf_capable(void)
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{
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return capable(CAP_BPF) || capable(CAP_SYS_ADMIN);
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}
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static inline bool checkpoint_restore_ns_capable(struct user_namespace *ns)
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{
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return ns_capable(ns, CAP_CHECKPOINT_RESTORE) ||
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ns_capable(ns, CAP_SYS_ADMIN);
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}
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/* audit system wants to get cap info from files as well */
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extern int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps);
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int cap_convert_nscap(struct user_namespace *mnt_userns, struct dentry *dentry,
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const void **ivalue, size_t size);
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#endif /* !_LINUX_CAPABILITY_H */
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