* [RFC PATCH 2/2] fs: Grant CAP_TRUSTED rw access to trusted xattrs
2017-10-21 13:45 [RFC PATCH 1/2] security, capabilities: create CAP_TRUSTED Nicolas Belouin
@ 2017-10-21 13:45 ` Nicolas Belouin
2017-10-21 16:03 ` [RFC PATCH 1/2] security, capabilities: create CAP_TRUSTED Serge E. Hallyn
2017-10-21 17:25 ` [kernel-hardening] " Casey Schaufler
2 siblings, 0 replies; 6+ messages in thread
From: Nicolas Belouin @ 2017-10-21 13:45 UTC (permalink / raw)
To: linux-security-module
The trusted xattrs read/write access is the perfect use case for
CAP_TRUSTED.
Signed-off-by: Nicolas Belouin <nicolas@belouin.fr>
---
fs/ext2/xattr_trusted.c | 2 +-
fs/ext4/xattr_trusted.c | 2 +-
fs/f2fs/xattr.c | 6 +++---
fs/hfsplus/xattr.c | 2 +-
fs/jffs2/xattr_trusted.c | 2 +-
fs/jfs/xattr.c | 3 ++-
fs/ocfs2/xattr.c | 2 +-
fs/overlayfs/inode.c | 3 ++-
fs/reiserfs/xattr_trusted.c | 11 ++++++++---
fs/squashfs/xattr.c | 2 +-
fs/ubifs/xattr.c | 3 ++-
fs/xattr.c | 4 ++--
12 files changed, 25 insertions(+), 17 deletions(-)
diff --git a/fs/ext2/xattr_trusted.c b/fs/ext2/xattr_trusted.c
index 65049b71af13..8006c24f8ee0 100644
--- a/fs/ext2/xattr_trusted.c
+++ b/fs/ext2/xattr_trusted.c
@@ -11,7 +11,7 @@
static bool
ext2_xattr_trusted_list(struct dentry *dentry)
{
- return capable(CAP_SYS_ADMIN);
+ return capable(CAP_SYS_ADMIN) || capable(CAP_TRUSTED);
}
static int
diff --git a/fs/ext4/xattr_trusted.c b/fs/ext4/xattr_trusted.c
index c7765c735714..9849d1e0ebb9 100644
--- a/fs/ext4/xattr_trusted.c
+++ b/fs/ext4/xattr_trusted.c
@@ -15,7 +15,7 @@
static bool
ext4_xattr_trusted_list(struct dentry *dentry)
{
- return capable(CAP_SYS_ADMIN);
+ return capable(CAP_SYS_ADMIN) || capable(CAP_TRUSTED);
}
static int
diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
index 7c65540148f8..ef572464deca 100644
--- a/fs/f2fs/xattr.c
+++ b/fs/f2fs/xattr.c
@@ -37,7 +37,7 @@ static int f2fs_xattr_generic_get(const struct xattr_handler *handler,
return -EOPNOTSUPP;
break;
case F2FS_XATTR_INDEX_TRUSTED:
- if (!capable(CAP_SYS_ADMIN))
+ if (!capable(CAP_SYS_ADMIN) && !capable(CAP_TRUSTED))
return -EPERM;
break;
case F2FS_XATTR_INDEX_SECURITY:
@@ -62,7 +62,7 @@ static int f2fs_xattr_generic_set(const struct xattr_handler *handler,
return -EOPNOTSUPP;
break;
case F2FS_XATTR_INDEX_TRUSTED:
- if (!capable(CAP_SYS_ADMIN))
+ if (!capable(CAP_SYS_ADMIN) && !capable(CAP_TRUSTED))
return -EPERM;
break;
case F2FS_XATTR_INDEX_SECURITY:
@@ -83,7 +83,7 @@ static bool f2fs_xattr_user_list(struct dentry *dentry)
static bool f2fs_xattr_trusted_list(struct dentry *dentry)
{
- return capable(CAP_SYS_ADMIN);
+ return capable(CAP_SYS_ADMIN) || capable(CAP_TRUSTED);
}
static int f2fs_xattr_advise_get(const struct xattr_handler *handler,
diff --git a/fs/hfsplus/xattr.c b/fs/hfsplus/xattr.c
index ae03a19196ef..0ec6d02ee7e9 100644
--- a/fs/hfsplus/xattr.c
+++ b/fs/hfsplus/xattr.c
@@ -606,7 +606,7 @@ static inline int can_list(const char *xattr_name)
return !strncmp(xattr_name, XATTR_TRUSTED_PREFIX,
XATTR_TRUSTED_PREFIX_LEN) ||
- capable(CAP_SYS_ADMIN);
+ capable(CAP_SYS_ADMIN) || capable(CAP_TRUSTED);
}
static ssize_t hfsplus_listxattr_finder_info(struct dentry *dentry,
diff --git a/fs/jffs2/xattr_trusted.c b/fs/jffs2/xattr_trusted.c
index 5d6030826c52..3c7ae98e4525 100644
--- a/fs/jffs2/xattr_trusted.c
+++ b/fs/jffs2/xattr_trusted.c
@@ -35,7 +35,7 @@ static int jffs2_trusted_setxattr(const struct xattr_handler *handler,
static bool jffs2_trusted_listxattr(struct dentry *dentry)
{
- return capable(CAP_SYS_ADMIN);
+ return capable(CAP_SYS_ADMIN) || capable(CAP_TRUSTED);
}
const struct xattr_handler jffs2_trusted_xattr_handler = {
diff --git a/fs/jfs/xattr.c b/fs/jfs/xattr.c
index 1c46573a96ed..e4f44f5133a1 100644
--- a/fs/jfs/xattr.c
+++ b/fs/jfs/xattr.c
@@ -859,7 +859,8 @@ ssize_t __jfs_getxattr(struct inode *inode, const char *name, void *data,
static inline int can_list(struct jfs_ea *ea)
{
return (!strncmp(ea->name, XATTR_TRUSTED_PREFIX,
- XATTR_TRUSTED_PREFIX_LEN) || capable(CAP_SYS_ADMIN));
+ XATTR_TRUSTED_PREFIX_LEN) ||
+ capable(CAP_SYS_ADMIN) || capable(CAP_TRUSTED));
}
ssize_t jfs_listxattr(struct dentry * dentry, char *data, size_t buf_size)
diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
index 5fdf269ba82e..2b3994d192c6 100644
--- a/fs/ocfs2/xattr.c
+++ b/fs/ocfs2/xattr.c
@@ -906,7 +906,7 @@ static int ocfs2_xattr_list_entry(struct super_block *sb,
break;
case OCFS2_XATTR_INDEX_TRUSTED:
- if (!capable(CAP_SYS_ADMIN))
+ if (!capable(CAP_SYS_ADMIN) && !capable(CAP_TRUSTED))
return 0;
break;
}
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index a619addecafc..c627003d3a74 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -264,7 +264,8 @@ static bool ovl_can_list(const char *s)
return true;
/* Never list trusted.overlay, list other trusted for superuser only */
- return !ovl_is_private_xattr(s) && capable(CAP_SYS_ADMIN);
+ return !ovl_is_private_xattr(s) &&
+ (capable(CAP_SYS_ADMIN) || capable(CAP_TRUSTED));
}
ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
diff --git a/fs/reiserfs/xattr_trusted.c b/fs/reiserfs/xattr_trusted.c
index f15a5f9e84ce..6f3fa0db8272 100644
--- a/fs/reiserfs/xattr_trusted.c
+++ b/fs/reiserfs/xattr_trusted.c
@@ -7,11 +7,16 @@
#include "xattr.h"
#include <linux/uaccess.h>
+inline bool trusted_capable(void)
+{
+ return capable(CAP_SYS_ADMIN) || capable(CAP_TRUSTED);
+}
+
static int
trusted_get(const struct xattr_handler *handler, struct dentry *unused,
struct inode *inode, const char *name, void *buffer, size_t size)
{
- if (!capable(CAP_SYS_ADMIN) || IS_PRIVATE(inode))
+ if (!trusted_capable() || IS_PRIVATE(inode))
return -EPERM;
return reiserfs_xattr_get(inode, xattr_full_name(handler, name),
@@ -23,7 +28,7 @@ trusted_set(const struct xattr_handler *handler, struct dentry *unused,
struct inode *inode, const char *name, const void *buffer,
size_t size, int flags)
{
- if (!capable(CAP_SYS_ADMIN) || IS_PRIVATE(inode))
+ if (!trusted_capable() || IS_PRIVATE(inode))
return -EPERM;
return reiserfs_xattr_set(inode,
@@ -33,7 +38,7 @@ trusted_set(const struct xattr_handler *handler, struct dentry *unused,
static bool trusted_list(struct dentry *dentry)
{
- return capable(CAP_SYS_ADMIN) && !IS_PRIVATE(d_inode(dentry));
+ return trusted_capable() && !IS_PRIVATE(d_inode(dentry));
}
const struct xattr_handler reiserfs_xattr_trusted_handler = {
diff --git a/fs/squashfs/xattr.c b/fs/squashfs/xattr.c
index 1548b3784548..e0a285ab1f7e 100644
--- a/fs/squashfs/xattr.c
+++ b/fs/squashfs/xattr.c
@@ -237,7 +237,7 @@ static const struct xattr_handler squashfs_xattr_user_handler = {
*/
static bool squashfs_trusted_xattr_handler_list(struct dentry *d)
{
- return capable(CAP_SYS_ADMIN);
+ return capable(CAP_SYS_ADMIN) || capable(CAP_TRUSTED);
}
static const struct xattr_handler squashfs_xattr_trusted_handler = {
diff --git a/fs/ubifs/xattr.c b/fs/ubifs/xattr.c
index c13eae819cbc..f3aa8be72a66 100644
--- a/fs/ubifs/xattr.c
+++ b/fs/ubifs/xattr.c
@@ -406,7 +406,8 @@ static bool xattr_visible(const char *name)
/* Show trusted namespace only for "power" users */
if (strncmp(name, XATTR_TRUSTED_PREFIX,
- XATTR_TRUSTED_PREFIX_LEN) == 0 && !capable(CAP_SYS_ADMIN))
+ XATTR_TRUSTED_PREFIX_LEN) == 0 &&
+ !capable(CAP_SYS_ADMIN) && !capable(CAP_TRUSTED))
return false;
return true;
diff --git a/fs/xattr.c b/fs/xattr.c
index 61cd28ba25f3..d9e9a0083dbb 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -113,7 +113,7 @@ xattr_permission(struct inode *inode, const char *name, int mask)
* The trusted.* namespace can only be accessed by privileged users.
*/
if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
- if (!capable(CAP_SYS_ADMIN))
+ if (!capable(CAP_SYS_ADMIN) && !capable(CAP_TRUSTED))
return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
return 0;
}
@@ -945,7 +945,7 @@ static int xattr_list_one(char **buffer, ssize_t *remaining_size,
ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
char *buffer, size_t size)
{
- bool trusted = capable(CAP_SYS_ADMIN);
+ bool trusted = capable(CAP_SYS_ADMIN) || capable(CAP_TRUSTED);
struct simple_xattr *xattr;
ssize_t remaining_size = size;
int err = 0;
--
2.14.2
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^ permalink raw reply related [flat|nested] 6+ messages in thread* [kernel-hardening] [RFC PATCH 1/2] security, capabilities: create CAP_TRUSTED
2017-10-21 13:45 [RFC PATCH 1/2] security, capabilities: create CAP_TRUSTED Nicolas Belouin
2017-10-21 13:45 ` [RFC PATCH 2/2] fs: Grant CAP_TRUSTED rw access to trusted xattrs Nicolas Belouin
2017-10-21 16:03 ` [RFC PATCH 1/2] security, capabilities: create CAP_TRUSTED Serge E. Hallyn
@ 2017-10-21 17:25 ` Casey Schaufler
2017-10-21 19:04 ` nicolas at belouin.fr
2 siblings, 1 reply; 6+ messages in thread
From: Casey Schaufler @ 2017-10-21 17:25 UTC (permalink / raw)
To: linux-security-module
On 10/21/2017 6:45 AM, Nicolas Belouin wrote:
> with CAP_SYS_ADMIN being bloated, the usefulness of using it to
> flag a process to be entrusted for e.g reading and writing trusted
> xattr is near zero.
> CAP_TRUSTED aims to provide userland with a way to mark a process as
> entrusted to do specific (not specially admin-centered) actions. It
> would for example allow a process to red/write the trusted xattrs.
Please explain how this is different from CAP_MAC_ADMIN in
any existing use case. If it is significantly different, how
would the two interact?
> Signed-off-by: Nicolas Belouin <nicolas@belouin.fr>
> ---
> include/uapi/linux/capability.h | 6 +++++-
> security/selinux/include/classmap.h | 5 +++--
> 2 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/include/uapi/linux/capability.h b/include/uapi/linux/capability.h
> index ce230aa6d928..27e457b93c84 100644
> --- a/include/uapi/linux/capability.h
> +++ b/include/uapi/linux/capability.h
> @@ -369,7 +369,11 @@ struct vfs_ns_cap_data {
>
> #define CAP_SYS_MOUNT 38
>
> -#define CAP_LAST_CAP CAP_SYS_MOUNT
> +/* Allow read/write trusted xattr */
> +
> +#define CAP_TRUSTED 39
> +
> +#define CAP_LAST_CAP CAP_TRUSTED
>
> #define cap_valid(x) ((x) >= 0 && (x) <= CAP_LAST_CAP)
>
> diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
> index a873dce97fd5..f5dc8e109f5a 100644
> --- a/security/selinux/include/classmap.h
> +++ b/security/selinux/include/classmap.h
> @@ -24,9 +24,10 @@
> "audit_control", "setfcap"
>
> #define COMMON_CAP2_PERMS "mac_override", "mac_admin", "syslog", \
> - "wake_alarm", "block_suspend", "audit_read", "sys_mount"
> + "wake_alarm", "block_suspend", "audit_read", "sys_mount", \
> + "trusted"
>
> -#if CAP_LAST_CAP > CAP_SYS_MOUNT
> +#if CAP_LAST_CAP > CAP_TRUSTED
> #error New capability defined, please update COMMON_CAP2_PERMS.
> #endif
>
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^ permalink raw reply [flat|nested] 6+ messages in thread