* [RFC v0.1][PATCH] selinuxns: extend namespace support to security.selinux xattrs
@ 2017-10-30 10:04 James Morris
2017-10-30 15:55 ` Casey Schaufler
2017-10-30 19:16 ` Stephen Smalley
0 siblings, 2 replies; 11+ messages in thread
From: James Morris @ 2017-10-30 10:04 UTC (permalink / raw)
To: linux-security-module
This is a proof-of-concept patch to demonstrate an approach to supporting
SELinux namespaces for security.selinux xattr labels.
This follows on from the experimental SELinux namespace code posted by
Stephen: https://marc.info/?l=selinux&m=150696042210126&w=2
In the initial code, namespacing was only implemented for in-core inodes
per this posting: https://marc.info/?l=selinux&m=150696324110943&w=2
In this patch, namespacing is extended to on-disk inode labels (xattrs),
transparently to normal applications.
A summary of the approach is as follows:
1. Add a namespace "name" field to the SELinux namespace, which is
specified by writing to the selinuxfs unshare node (instead of the
current boolean value) during namespace creation.
e.g. if the namespace name is "vm8", run:
# echo vm8 > /sys/fs/selinux/unshare
followed by the remaining steps from the original code.
This value can also be read back from the node, and the initial SELinux
namespace is internally set to "init".
2. Transparently modify SELinux xattrs so that any non-initial namespace
xattrs include the namespace name.
e.g. if the namespace name is "vm6", the "security.selinux" xattr is
translated in the kernel to "security.selinux.ns.vm6" for disk read and
write of xattrs.
This allows each SELinux namespace to independently manage its own
xattr labels, transparently to applications. Namespaces only see their
own xattrs, which are acted on by their own namespaced policies.
Note that the "init" namespace performs no translation for apps, it
just uses regular old security.selinux xattrs.
Some examples:
[root at test]# cat /sys/fs/selinux/unshare
vm8
[root at test]# touch testfile
[root at test]# ls -Z testfile
-rw-r--r--. root root unconfined_u:object_r:unlabeled_t:s0 testfile
[root at test]# getfattr -n security.selinux testfile
# file: testfile
security.selinux="unconfined_u:object_r:unlabeled_t:s0"
# restorecon -v testfile
restorecon reset /root/selinux/testfile context unconfined_u:object_r:unlabeled_t:s0->unconfined_u:object_r:admin_home_t:s0
[root at test]# getfattr -n security.selinux testfile
# file: testfile
security.selinux="unconfined_u:object_r:admin_home_t:s0"
[root at test]# chcon -t etc_t testfile
[root at test]# getfattr -n security.selinux testfile
# file: testfile
security.selinux="unconfined_u:object_r:etc_t:s0"
Ok, so this all looks pretty normal, but what's happening on disk is not.
>From the init namespace, I'll access the same file:
[root at test]# cat /sys/fs/selinux/unshare
init
[root at test]# ls -Z testfile
-rw-r--r--. root root system_u:object_r:unlabeled_t:s0 testfile
[root at test]# getfattr -n security.selinux testfile
# file: testfile
security.selinux="system_u:object_r:unlabeled_t:s0"
There is in fact no security.selinux xattr yet on this file as it was
created in a different namespace and only initialized there. What you're
seeing here is the default unlabeled label. Dumping out the xattrs shows
what's on disk:
[root at test]# getfattr -d -m . testfile
# file: testfile
security.selinux.ns.vm8="unconfined_u:object_r:etc_t:s0"
The xattr belonging to "vm8" is there but not being interpreted outside
that namespace. Let's give it a proper label for the init ns:
# restorecon -v testfile
restorecon reset /root/selinux/testfile context system_u:object_r:unlabeled_t:s0->system_u:object_r:admin_home_t:s0
[root at test]# getfattr -d -m . testfile
# file: testfile
security.selinux="system_u:object_r:admin_home_t:s0"
security.selinux.ns.vm8="unconfined_u:object_r:etc_t:s0"
[root at test]# ls -Z testfile
-rw-r--r--. root root system_u:object_r:admin_home_t:s0 testfile
And if you go into the vm8 namespace you'll see the label there is:
[root at test]# echo vm8 > /sys/fs/selinux/unshare
[root at test]# unshare -m -n
[root at test]# umount /sys/fs/selinux && mount -t selinuxfs none /sys/fs/selinux && load_policy
[root at test]# runcon unconfined_u:unconfined_r:unconfined_t:s0:c0.c1023 /bin/bash
[root at test]# setenforce 1
[root at test]# ls -Z testfile
-rw-r--r--. root root unconfined_u:object_r:etc_t:s0 testfile
I hope that demonstrates the concept well enough: that there are zero
changes for applications and the namespaced policy always uses xattrs
belonging to that namespace.
The prototype code is far from complete, and also needs to implement
support for listxattr and removexattr, as well as provide appropriate
administrative access to raw (untranslated) xattrs, which you can
currently see from any ns but not write at all. Other TODO items include
accounting for dynamic xattr name size, nested policy enforcement,
uniqueness of namespace names, and better audit support.
Comments?
Patch below...
---
From: James Morris <james.l.morris@oracle.com>
Date: Mon, 30 Oct 2017 19:10:36 +1100
Subject: [PATCH] selinuxns: extend namespace support to security.selinux xattrs
Prototype code only.
Signed-off-by: James Morris <james.l.morris@oracle.com>
---
fs/xattr.c | 12 ++++--
include/linux/lsm_hooks.h | 2 +
include/linux/security.h | 6 +++
include/linux/xattr.h | 2 +-
include/uapi/linux/xattr.h | 3 ++
security/integrity/evm/evm_crypto.c | 2 +-
security/integrity/ima/ima_appraise.c | 2 +-
security/security.c | 6 +++
security/selinux/hooks.c | 75 ++++++++++++++++++++++++++++++-----
security/selinux/include/security.h | 7 +++-
security/selinux/selinuxfs.c | 63 ++++++++++++++++++-----------
security/smack/smack_lsm.c | 2 +-
12 files changed, 142 insertions(+), 40 deletions(-)
diff --git a/fs/xattr.c b/fs/xattr.c
index 4424f7f..d8107b7 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -157,6 +157,7 @@
*
* @dentry - object to perform setxattr on
* @name - xattr name to set
+ * @nsname - namespaced xattr name, use instead of @name if set
* @value - value to set @name to
* @size - size of @value
* @flags - flags to pass into filesystem operations
@@ -168,7 +169,7 @@
* permission checks.
*/
int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
- const void *value, size_t size, int flags)
+ const char *nsname, const void *value, size_t size, int flags)
{
struct inode *inode = dentry->d_inode;
int error = -EAGAIN;
@@ -178,7 +179,8 @@ int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
if (issec)
inode->i_flags &= ~S_NOSEC;
if (inode->i_opflags & IOP_XATTR) {
- error = __vfs_setxattr(dentry, inode, name, value, size, flags);
+ error = __vfs_setxattr(dentry, inode, nsname?:name, value,
+ size, flags);
if (!error) {
fsnotify_xattr(dentry);
security_inode_post_setxattr(dentry, name, value,
@@ -211,6 +213,7 @@ int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
{
struct inode *inode = dentry->d_inode;
int error;
+ char *nsname = NULL;
error = xattr_permission(inode, name, MAY_WRITE);
if (error)
@@ -221,8 +224,11 @@ int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
if (error)
goto out;
- error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
+ error = security_inode_translate_xattr_to_ns(name, &nsname);
+ if (error)
+ goto out;
+ error = __vfs_setxattr_noperm(dentry, name, nsname, value, size, flags);
out:
inode_unlock(inode);
return error;
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index c925812..e4eb43e 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1480,6 +1480,7 @@
void (*inode_getsecid)(struct inode *inode, u32 *secid);
int (*inode_copy_up)(struct dentry *src, struct cred **new);
int (*inode_copy_up_xattr)(const char *name);
+ int (*inode_translate_xattr_to_ns)(const char *name, char **tr);
int (*file_permission)(struct file *file, int mask);
int (*file_alloc_security)(struct file *file);
@@ -1760,6 +1761,7 @@ struct security_hook_heads {
struct list_head inode_getsecid;
struct list_head inode_copy_up;
struct list_head inode_copy_up_xattr;
+ struct list_head inode_translate_xattr_to_ns;
struct list_head file_permission;
struct list_head file_alloc_security;
struct list_head file_free_security;
diff --git a/include/linux/security.h b/include/linux/security.h
index ce62659..64297e1 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -302,6 +302,7 @@ void security_inode_post_setxattr(struct dentry *dentry, const char *name,
void security_inode_getsecid(struct inode *inode, u32 *secid);
int security_inode_copy_up(struct dentry *src, struct cred **new);
int security_inode_copy_up_xattr(const char *name);
+int security_inode_translate_xattr_to_ns(const char *name, char **tr);
int security_file_permission(struct file *file, int mask);
int security_file_alloc(struct file *file);
void security_file_free(struct file *file);
@@ -808,6 +809,11 @@ static inline int security_inode_copy_up_xattr(const char *name)
return -EOPNOTSUPP;
}
+static inline int security_inode_translate_xattr_to_ns(const char *name, char **tr)
+{
+ return 0;
+}
+
static inline int security_file_permission(struct file *file, int mask)
{
return 0;
diff --git a/include/linux/xattr.h b/include/linux/xattr.h
index e77605a..c25eb8a 100644
--- a/include/linux/xattr.h
+++ b/include/linux/xattr.h
@@ -50,7 +50,7 @@ struct xattr {
ssize_t vfs_getxattr(struct dentry *, const char *, void *, size_t);
ssize_t vfs_listxattr(struct dentry *d, char *list, size_t size);
int __vfs_setxattr(struct dentry *, struct inode *, const char *, const void *, size_t, int);
-int __vfs_setxattr_noperm(struct dentry *, const char *, const void *, size_t, int);
+int __vfs_setxattr_noperm(struct dentry *, const char *, const char *, const void *, size_t, int);
int vfs_setxattr(struct dentry *, const char *, const void *, size_t, int);
int __vfs_removexattr(struct dentry *, const char *);
int vfs_removexattr(struct dentry *, const char *);
diff --git a/include/uapi/linux/xattr.h b/include/uapi/linux/xattr.h
index 1590c49..528a5f7 100644
--- a/include/uapi/linux/xattr.h
+++ b/include/uapi/linux/xattr.h
@@ -51,6 +51,9 @@
#define XATTR_SELINUX_SUFFIX "selinux"
#define XATTR_NAME_SELINUX XATTR_SECURITY_PREFIX XATTR_SELINUX_SUFFIX
+#define XATTR_SELINUX_NS_INFIX ".ns."
+#define XATTR_NAME_SELINUX_NS XATTR_NAME_SELINUX XATTR_SELINUX_NS_INFIX
+#define XATTR_NAME_SELINUX_NS_LEN (sizeof(XATTR_NAME_SELINUX_NS) - 1)
#define XATTR_SMACK_SUFFIX "SMACK64"
#define XATTR_SMACK_IPIN "SMACK64IPIN"
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index 1d32cd2..2249186 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -260,7 +260,7 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
if (rc == 0) {
xattr_data.type = EVM_XATTR_HMAC;
rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
- &xattr_data,
+ NULL, &xattr_data,
sizeof(xattr_data), 0);
} else if (rc == -ENODATA && (inode->i_opflags & IOP_XATTR)) {
rc = __vfs_removexattr(dentry, XATTR_NAME_EVM);
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 809ba70..914cf5f 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -71,7 +71,7 @@ static int ima_fix_xattr(struct dentry *dentry,
iint->ima_hash->xattr.ng.algo = algo;
}
rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
- &iint->ima_hash->xattr.data[offset],
+ NULL, &iint->ima_hash->xattr.data[offset],
(sizeof(iint->ima_hash->xattr) - offset) +
iint->ima_hash->length, 0);
return rc;
diff --git a/security/security.c b/security/security.c
index 4bf0f57..7fce259 100644
--- a/security/security.c
+++ b/security/security.c
@@ -856,6 +856,12 @@ int security_inode_copy_up_xattr(const char *name)
}
EXPORT_SYMBOL(security_inode_copy_up_xattr);
+int security_inode_translate_xattr_to_ns(const char *name, char **tr)
+{
+ return call_int_hook(inode_translate_xattr_to_ns, 0, name, tr);
+}
+EXPORT_SYMBOL(security_inode_translate_xattr_to_ns);
+
int security_file_permission(struct file *file, int mask)
{
int ret;
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 3daad14..6b29d70 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -646,6 +646,22 @@ static int selinux_is_sblabel_mnt(struct super_block *sb)
!strcmp(sb->s_type->name, "cgroup2")));
}
+static char *current_xattr_suffix(void)
+{
+ if (current_selinux_ns != init_selinux_ns)
+ return current_selinux_ns->xattr_name + XATTR_SECURITY_PREFIX_LEN;
+ else
+ return XATTR_SELINUX_SUFFIX;
+}
+
+static char *current_xattr_name(void)
+{
+ if (current_selinux_ns != init_selinux_ns)
+ return current_selinux_ns->xattr_name;
+ else
+ return XATTR_NAME_SELINUX;
+}
+
static int sb_finish_set_opts(struct super_block *sb)
{
struct superblock_security_struct *sbsec = superblock_security(sb);
@@ -654,6 +670,8 @@ static int sb_finish_set_opts(struct super_block *sb)
int rc = 0;
if (sbsec->behavior == SECURITY_FS_USE_XATTR) {
+ char *name;
+
/* Make sure that the xattr handler exists and that no
error other than -ENODATA is returned by getxattr on
the root directory. -ENODATA is ok, as this may be
@@ -666,7 +684,9 @@ static int sb_finish_set_opts(struct super_block *sb)
goto out;
}
- rc = __vfs_getxattr(root, root_inode, XATTR_NAME_SELINUX, NULL, 0);
+ name = current_xattr_name();
+
+ rc = __vfs_getxattr(root, root_inode, name, NULL, 0);
if (rc < 0 && rc != -ENODATA) {
if (rc == -EOPNOTSUPP)
printk(KERN_WARNING "SELinux: (dev %s, type "
@@ -1660,6 +1680,7 @@ static int inode_doinit_with_dentry(struct inode *inode,
char *context = NULL;
unsigned len = 0;
int rc = 0;
+ char *name;
if (isec->initialized == LABEL_INITIALIZED)
return 0;
@@ -1729,12 +1750,14 @@ static int inode_doinit_with_dentry(struct inode *inode,
goto out;
}
context[len] = '\0';
- rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, context, len);
+
+ name = current_xattr_name();
+ rc = __vfs_getxattr(dentry, inode, name, context, len);
if (rc == -ERANGE) {
kfree(context);
/* Need a larger buffer. Query for the right size. */
- rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, NULL, 0);
+ rc = __vfs_getxattr(dentry, inode, name, NULL, 0);
if (rc < 0) {
dput(dentry);
goto out;
@@ -1747,7 +1770,7 @@ static int inode_doinit_with_dentry(struct inode *inode,
goto out;
}
context[len] = '\0';
- rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, context, len);
+ rc = __vfs_getxattr(dentry, inode, name, context, len);
}
dput(dentry);
if (rc < 0) {
@@ -3167,7 +3190,7 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
return -EOPNOTSUPP;
if (name)
- *name = XATTR_SELINUX_SUFFIX;
+ *name = current_xattr_suffix();
if (value && len) {
rc = security_sid_to_context_force(current_selinux_ns, newsid,
@@ -3382,6 +3405,10 @@ static bool has_cap_mac_admin(bool audit)
return true;
}
+/* TODO:
+ * - audit
+ * - handle raw namespaced xattrs
+ */
static int selinux_inode_setxattr(struct dentry *dentry, const char *name,
const void *value, size_t size, int flags)
{
@@ -3392,8 +3419,12 @@ static int selinux_inode_setxattr(struct dentry *dentry, const char *name,
u32 newsid, sid = current_sid();
int rc = 0;
- if (strcmp(name, XATTR_NAME_SELINUX))
+ if (strcmp(name, XATTR_NAME_SELINUX)) {
+ /* No raw namespaced xattrs, yet */
+ if (!strncmp(name, XATTR_NAME_SELINUX_NS, XATTR_NAME_SELINUX_NS_LEN))
+ return -EPERM;
return selinux_inode_setotherxattr(dentry, name);
+ }
sbsec = superblock_security(inode->i_sb);
if (!(sbsec->flags & SBLABEL_MNT))
@@ -3640,6 +3671,13 @@ static int selinux_inode_copy_up_xattr(const char *name)
return -EOPNOTSUPP;
}
+static int selinux_inode_translate_xattr_to_ns(const char *name, char **tr)
+{
+ if(!strcmp(name, XATTR_NAME_SELINUX))
+ *tr = current_xattr_name();
+ return 0;
+}
+
/* file security operations */
static int selinux_revalidate_file_permission(struct file *file, int mask)
@@ -6430,10 +6468,11 @@ static int selinux_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen
/*
* called with inode->i_mutex locked
+ * TODO: namespace translation
*/
static int selinux_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen)
{
- return __vfs_setxattr_noperm(dentry, XATTR_NAME_SELINUX, ctx, ctxlen, 0);
+ return __vfs_setxattr_noperm(dentry, XATTR_NAME_SELINUX, NULL, ctx, ctxlen, 0);
}
static int selinux_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
@@ -6647,6 +6686,7 @@ static void selinux_ib_free_security(void *ib_sec)
LSM_HOOK_INIT(inode_getsecid, selinux_inode_getsecid),
LSM_HOOK_INIT(inode_copy_up, selinux_inode_copy_up),
LSM_HOOK_INIT(inode_copy_up_xattr, selinux_inode_copy_up_xattr),
+ LSM_HOOK_INIT(inode_translate_xattr_to_ns, selinux_inode_translate_xattr_to_ns),
LSM_HOOK_INIT(file_permission, selinux_file_permission),
LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security),
@@ -6805,7 +6845,7 @@ static void selinux_ib_free_security(void *ib_sec)
static void selinux_ns_free(struct work_struct *work);
-int selinux_ns_create(struct selinux_ns *parent, struct selinux_ns **ns)
+int selinux_ns_create(struct selinux_ns *parent, struct selinux_ns **ns, const char *name)
{
struct selinux_ns *newns;
int rc;
@@ -6825,14 +6865,29 @@ int selinux_ns_create(struct selinux_ns *parent, struct selinux_ns **ns)
if (rc)
goto err;
+ newns->name = kstrdup(name, GFP_KERNEL);
+ if (!newns->name) {
+ rc = -ENOMEM;
+ goto err_avc;
+ }
+
+ newns->xattr_name = kasprintf(GFP_KERNEL, "%s.ns.%s", XATTR_NAME_SELINUX, name);
+ if (!newns->xattr_name) {
+ rc = -ENOMEM;
+ goto err_avc;
+ }
+
if (parent)
newns->parent = get_selinux_ns(parent);
*ns = newns;
return 0;
+err_avc:
+ selinux_avc_free(newns->avc);
err:
selinux_ss_free(newns->ss);
kfree(newns);
+ kfree(newns->name);
return rc;
}
@@ -6845,6 +6900,8 @@ static void selinux_ns_free(struct work_struct *work)
parent = ns->parent;
selinux_ss_free(ns->ss);
selinux_avc_free(ns->avc);
+ kfree(ns->name);
+ kfree(ns->xattr_name);
kfree(ns);
ns = parent;
} while (ns && refcount_dec_and_test(&ns->count));
@@ -6869,7 +6926,7 @@ static __init int selinux_init(void)
printk(KERN_INFO "SELinux: Initializing.\n");
- if (selinux_ns_create(NULL, &init_selinux_ns))
+ if (selinux_ns_create(NULL, &init_selinux_ns, SELINUX_NS_INIT_NAME))
panic("SELinux: Could not create initial namespace\n");
set_ns_enforcing(init_selinux_ns, selinux_enforcing_boot);
diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index b80f9bd..f5f5a31 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -92,6 +92,9 @@ enum {
/* limitation of boundary depth */
#define POLICYDB_BOUNDS_MAXDEPTH 4
+/* Name of SELinux initial namespace */
+#define SELINUX_NS_INIT_NAME "init"
+
struct selinux_avc;
struct selinux_ss;
@@ -108,9 +111,11 @@ struct selinux_ns {
struct selinux_avc *avc;
struct selinux_ss *ss;
struct selinux_ns *parent;
+ char *name;
+ char *xattr_name;
};
-int selinux_ns_create(struct selinux_ns *parent, struct selinux_ns **ns);
+int selinux_ns_create(struct selinux_ns *parent, struct selinux_ns **ns, const char *name);
void __put_selinux_ns(struct selinux_ns *ns);
int selinux_ss_create(struct selinux_ss **ss);
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 6c52d24..d190213 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -334,9 +334,10 @@ static ssize_t sel_write_unshare(struct file *file, const char __user *buf,
{
struct selinux_fs_info *fsi = file_inode(file)->i_sb->s_fs_info;
struct selinux_ns *ns = fsi->ns;
+ struct cred *cred;
+ struct task_security_struct *tsec;
char *page;
ssize_t length;
- bool set;
int rc;
if (ns != current_selinux_ns)
@@ -359,30 +360,32 @@ static ssize_t sel_write_unshare(struct file *file, const char __user *buf,
if (IS_ERR(page))
return PTR_ERR(page);
- length = -EINVAL;
- if (kstrtobool(page, &set))
- goto out;
+ /* strip any trailing newline */
+ if (page[strlen(page) - 1] == '\n')
+ page[strlen(page) - 1] = 0;
- if (set) {
- struct cred *cred = prepare_creds();
- struct task_security_struct *tsec;
+ /* TODO: check for uniqueness! */
+ if (!strcmp(SELINUX_NS_INIT_NAME, page)) {
+ length = -EINVAL;
+ goto out;
+ }
- if (!cred) {
- length = -ENOMEM;
- goto out;
- }
- tsec = cred->security;
- if (selinux_ns_create(ns, &tsec->ns)) {
- abort_creds(cred);
- length = -ENOMEM;
- goto out;
- }
- tsec->osid = tsec->sid = SECINITSID_KERNEL;
- tsec->exec_sid = tsec->create_sid = tsec->keycreate_sid =
- tsec->sockcreate_sid = SECSID_NULL;
- tsec->parent_cred = get_current_cred();
- commit_creds(cred);
+ cred = prepare_creds();
+ if (!cred) {
+ length = -ENOMEM;
+ goto out;
+ }
+ tsec = cred->security;
+ if (selinux_ns_create(ns, &tsec->ns, page)) {
+ abort_creds(cred);
+ length = -ENOMEM;
+ goto out;
}
+ tsec->osid = tsec->sid = SECINITSID_KERNEL;
+ tsec->exec_sid = tsec->create_sid = tsec->keycreate_sid =
+ tsec->sockcreate_sid = SECSID_NULL;
+ tsec->parent_cred = get_current_cred();
+ commit_creds(cred);
length = count;
out:
@@ -390,8 +393,22 @@ static ssize_t sel_write_unshare(struct file *file, const char __user *buf,
return length;
}
+static ssize_t sel_read_unshare(struct file *file, char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ struct selinux_fs_info *fsi = file_inode(file)->i_sb->s_fs_info;
+ struct selinux_ns *ns = fsi->ns;
+ char *name = ns->name;
+
+ if (ns != current_selinux_ns)
+ return -EPERM;
+
+ return simple_read_from_buffer(buf, count, ppos, name, strlen(name));
+}
+
static const struct file_operations sel_unshare_ops = {
.write = sel_write_unshare,
+ .read = sel_read_unshare,
.llseek = generic_file_llseek,
};
@@ -2021,7 +2038,7 @@ static int sel_fill_super(struct super_block *sb, void *data, int silent)
[SEL_POLICY] = {"policy", &sel_policy_ops, S_IRUGO},
[SEL_VALIDATE_TRANS] = {"validatetrans", &sel_transition_ops,
S_IWUGO},
- [SEL_UNSHARE] = {"unshare", &sel_unshare_ops, 0222},
+ [SEL_UNSHARE] = {"unshare", &sel_unshare_ops, 0666},
/* last one */ {""}
};
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 319add3..5ea841f 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4591,7 +4591,7 @@ static int smack_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen)
static int smack_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen)
{
- return __vfs_setxattr_noperm(dentry, XATTR_NAME_SMACK, ctx, ctxlen, 0);
+ return __vfs_setxattr_noperm(dentry, XATTR_NAME_SMACK, NULL, ctx, ctxlen, 0);
}
static int smack_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
--
1.8.3.1
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^ permalink raw reply related [flat|nested] 11+ messages in thread
* [RFC v0.1][PATCH] selinuxns: extend namespace support to security.selinux xattrs
2017-10-30 10:04 [RFC v0.1][PATCH] selinuxns: extend namespace support to security.selinux xattrs James Morris
@ 2017-10-30 15:55 ` Casey Schaufler
2017-10-30 19:16 ` Stephen Smalley
1 sibling, 0 replies; 11+ messages in thread
From: Casey Schaufler @ 2017-10-30 15:55 UTC (permalink / raw)
To: linux-security-module
On 10/30/2017 3:04 AM, James Morris wrote:
> This is a proof-of-concept patch to demonstrate an approach to supporting
> SELinux namespaces for security.selinux xattr labels.
>
> This follows on from the experimental SELinux namespace code posted by
> Stephen: https://marc.info/?l=selinux&m=150696042210126&w=2
>
> In the initial code, namespacing was only implemented for in-core inodes
> per this posting: https://marc.info/?l=selinux&m=150696324110943&w=2
>
> In this patch, namespacing is extended to on-disk inode labels (xattrs),
> transparently to normal applications.
>
> A summary of the approach is as follows:
>
> 1. Add a namespace "name" field to the SELinux namespace, which is
> specified by writing to the selinuxfs unshare node (instead of the
> current boolean value) during namespace creation.
>
> e.g. if the namespace name is "vm8", run:
>
> # echo vm8 > /sys/fs/selinux/unshare
>
> followed by the remaining steps from the original code.
>
> This value can also be read back from the node, and the initial SELinux
> namespace is internally set to "init".
>
>
> 2. Transparently modify SELinux xattrs so that any non-initial namespace
> xattrs include the namespace name.
>
> e.g. if the namespace name is "vm6", the "security.selinux" xattr is
> translated in the kernel to "security.selinux.ns.vm6" for disk read and
> write of xattrs.
>
> This allows each SELinux namespace to independently manage its own
> xattr labels, transparently to applications. Namespaces only see their
> own xattrs, which are acted on by their own namespaced policies.
>
> Note that the "init" namespace performs no translation for apps, it
> just uses regular old security.selinux xattrs.
>
>
> Some examples:
>
> [root at test]# cat /sys/fs/selinux/unshare
> vm8
>
> [root at test]# touch testfile
>
> [root at test]# ls -Z testfile
> -rw-r--r--. root root unconfined_u:object_r:unlabeled_t:s0 testfile
>
> [root at test]# getfattr -n security.selinux testfile
> # file: testfile
> security.selinux="unconfined_u:object_r:unlabeled_t:s0"
>
> # restorecon -v testfile
> restorecon reset /root/selinux/testfile context unconfined_u:object_r:unlabeled_t:s0->unconfined_u:object_r:admin_home_t:s0
>
> [root at test]# getfattr -n security.selinux testfile
> # file: testfile
> security.selinux="unconfined_u:object_r:admin_home_t:s0"
>
> [root at test]# chcon -t etc_t testfile
>
> [root at test]# getfattr -n security.selinux testfile
> # file: testfile
> security.selinux="unconfined_u:object_r:etc_t:s0"
>
>
> Ok, so this all looks pretty normal, but what's happening on disk is not.
> >From the init namespace, I'll access the same file:
>
> [root at test]# cat /sys/fs/selinux/unshare
> init
>
> [root at test]# ls -Z testfile
> -rw-r--r--. root root system_u:object_r:unlabeled_t:s0 testfile
>
> [root at test]# getfattr -n security.selinux testfile
> # file: testfile
> security.selinux="system_u:object_r:unlabeled_t:s0"
>
> There is in fact no security.selinux xattr yet on this file as it was
> created in a different namespace and only initialized there. What you're
> seeing here is the default unlabeled label. Dumping out the xattrs shows
> what's on disk:
>
> [root at test]# getfattr -d -m . testfile
> # file: testfile
> security.selinux.ns.vm8="unconfined_u:object_r:etc_t:s0"
>
> The xattr belonging to "vm8" is there but not being interpreted outside
> that namespace. Let's give it a proper label for the init ns:
>
> # restorecon -v testfile
> restorecon reset /root/selinux/testfile context system_u:object_r:unlabeled_t:s0->system_u:object_r:admin_home_t:s0
>
> [root at test]# getfattr -d -m . testfile
> # file: testfile
> security.selinux="system_u:object_r:admin_home_t:s0"
> security.selinux.ns.vm8="unconfined_u:object_r:etc_t:s0"
>
> [root at test]# ls -Z testfile
> -rw-r--r--. root root system_u:object_r:admin_home_t:s0 testfile
>
> And if you go into the vm8 namespace you'll see the label there is:
>
> [root at test]# echo vm8 > /sys/fs/selinux/unshare
> [root at test]# unshare -m -n
> [root at test]# umount /sys/fs/selinux && mount -t selinuxfs none /sys/fs/selinux && load_policy
> [root at test]# runcon unconfined_u:unconfined_r:unconfined_t:s0:c0.c1023 /bin/bash
> [root at test]# setenforce 1
>
> [root at test]# ls -Z testfile
> -rw-r--r--. root root unconfined_u:object_r:etc_t:s0 testfile
>
>
> I hope that demonstrates the concept well enough: that there are zero
> changes for applications and the namespaced policy always uses xattrs
> belonging to that namespace.
>
> The prototype code is far from complete, and also needs to implement
> support for listxattr and removexattr, as well as provide appropriate
> administrative access to raw (untranslated) xattrs, which you can
> currently see from any ns but not write at all. Other TODO items include
> accounting for dynamic xattr name size, nested policy enforcement,
> uniqueness of namespace names, and better audit support.
>
> Comments?
I haven't thought through all the details, but it looks like you
could detach the namespace label from the SELinux label and make
this work for any security module that uses filesystem xattrs. It
even looks like it would work if you had multiple security modules
that use xattrs. That would be really handy.
>
> Patch below...
>
> ---
> From: James Morris <james.l.morris@oracle.com>
> Date: Mon, 30 Oct 2017 19:10:36 +1100
> Subject: [PATCH] selinuxns: extend namespace support to security.selinux xattrs
>
> Prototype code only.
>
> Signed-off-by: James Morris <james.l.morris@oracle.com>
> ---
> fs/xattr.c | 12 ++++--
> include/linux/lsm_hooks.h | 2 +
> include/linux/security.h | 6 +++
> include/linux/xattr.h | 2 +-
> include/uapi/linux/xattr.h | 3 ++
> security/integrity/evm/evm_crypto.c | 2 +-
> security/integrity/ima/ima_appraise.c | 2 +-
> security/security.c | 6 +++
> security/selinux/hooks.c | 75 ++++++++++++++++++++++++++++++-----
> security/selinux/include/security.h | 7 +++-
> security/selinux/selinuxfs.c | 63 ++++++++++++++++++-----------
> security/smack/smack_lsm.c | 2 +-
> 12 files changed, 142 insertions(+), 40 deletions(-)
>
> diff --git a/fs/xattr.c b/fs/xattr.c
> index 4424f7f..d8107b7 100644
> --- a/fs/xattr.c
> +++ b/fs/xattr.c
> @@ -157,6 +157,7 @@
> *
> * @dentry - object to perform setxattr on
> * @name - xattr name to set
> + * @nsname - namespaced xattr name, use instead of @name if set
> * @value - value to set @name to
> * @size - size of @value
> * @flags - flags to pass into filesystem operations
> @@ -168,7 +169,7 @@
> * permission checks.
> */
> int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
> - const void *value, size_t size, int flags)
> + const char *nsname, const void *value, size_t size, int flags)
> {
> struct inode *inode = dentry->d_inode;
> int error = -EAGAIN;
> @@ -178,7 +179,8 @@ int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
> if (issec)
> inode->i_flags &= ~S_NOSEC;
> if (inode->i_opflags & IOP_XATTR) {
> - error = __vfs_setxattr(dentry, inode, name, value, size, flags);
> + error = __vfs_setxattr(dentry, inode, nsname?:name, value,
> + size, flags);
> if (!error) {
> fsnotify_xattr(dentry);
> security_inode_post_setxattr(dentry, name, value,
> @@ -211,6 +213,7 @@ int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
> {
> struct inode *inode = dentry->d_inode;
> int error;
> + char *nsname = NULL;
>
> error = xattr_permission(inode, name, MAY_WRITE);
> if (error)
> @@ -221,8 +224,11 @@ int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
> if (error)
> goto out;
>
> - error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
> + error = security_inode_translate_xattr_to_ns(name, &nsname);
> + if (error)
> + goto out;
>
> + error = __vfs_setxattr_noperm(dentry, name, nsname, value, size, flags);
> out:
> inode_unlock(inode);
> return error;
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index c925812..e4eb43e 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -1480,6 +1480,7 @@
> void (*inode_getsecid)(struct inode *inode, u32 *secid);
> int (*inode_copy_up)(struct dentry *src, struct cred **new);
> int (*inode_copy_up_xattr)(const char *name);
> + int (*inode_translate_xattr_to_ns)(const char *name, char **tr);
>
> int (*file_permission)(struct file *file, int mask);
> int (*file_alloc_security)(struct file *file);
> @@ -1760,6 +1761,7 @@ struct security_hook_heads {
> struct list_head inode_getsecid;
> struct list_head inode_copy_up;
> struct list_head inode_copy_up_xattr;
> + struct list_head inode_translate_xattr_to_ns;
> struct list_head file_permission;
> struct list_head file_alloc_security;
> struct list_head file_free_security;
> diff --git a/include/linux/security.h b/include/linux/security.h
> index ce62659..64297e1 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -302,6 +302,7 @@ void security_inode_post_setxattr(struct dentry *dentry, const char *name,
> void security_inode_getsecid(struct inode *inode, u32 *secid);
> int security_inode_copy_up(struct dentry *src, struct cred **new);
> int security_inode_copy_up_xattr(const char *name);
> +int security_inode_translate_xattr_to_ns(const char *name, char **tr);
> int security_file_permission(struct file *file, int mask);
> int security_file_alloc(struct file *file);
> void security_file_free(struct file *file);
> @@ -808,6 +809,11 @@ static inline int security_inode_copy_up_xattr(const char *name)
> return -EOPNOTSUPP;
> }
>
> +static inline int security_inode_translate_xattr_to_ns(const char *name, char **tr)
> +{
> + return 0;
> +}
> +
> static inline int security_file_permission(struct file *file, int mask)
> {
> return 0;
> diff --git a/include/linux/xattr.h b/include/linux/xattr.h
> index e77605a..c25eb8a 100644
> --- a/include/linux/xattr.h
> +++ b/include/linux/xattr.h
> @@ -50,7 +50,7 @@ struct xattr {
> ssize_t vfs_getxattr(struct dentry *, const char *, void *, size_t);
> ssize_t vfs_listxattr(struct dentry *d, char *list, size_t size);
> int __vfs_setxattr(struct dentry *, struct inode *, const char *, const void *, size_t, int);
> -int __vfs_setxattr_noperm(struct dentry *, const char *, const void *, size_t, int);
> +int __vfs_setxattr_noperm(struct dentry *, const char *, const char *, const void *, size_t, int);
> int vfs_setxattr(struct dentry *, const char *, const void *, size_t, int);
> int __vfs_removexattr(struct dentry *, const char *);
> int vfs_removexattr(struct dentry *, const char *);
> diff --git a/include/uapi/linux/xattr.h b/include/uapi/linux/xattr.h
> index 1590c49..528a5f7 100644
> --- a/include/uapi/linux/xattr.h
> +++ b/include/uapi/linux/xattr.h
> @@ -51,6 +51,9 @@
>
> #define XATTR_SELINUX_SUFFIX "selinux"
> #define XATTR_NAME_SELINUX XATTR_SECURITY_PREFIX XATTR_SELINUX_SUFFIX
> +#define XATTR_SELINUX_NS_INFIX ".ns."
> +#define XATTR_NAME_SELINUX_NS XATTR_NAME_SELINUX XATTR_SELINUX_NS_INFIX
> +#define XATTR_NAME_SELINUX_NS_LEN (sizeof(XATTR_NAME_SELINUX_NS) - 1)
>
> #define XATTR_SMACK_SUFFIX "SMACK64"
> #define XATTR_SMACK_IPIN "SMACK64IPIN"
> diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
> index 1d32cd2..2249186 100644
> --- a/security/integrity/evm/evm_crypto.c
> +++ b/security/integrity/evm/evm_crypto.c
> @@ -260,7 +260,7 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
> if (rc == 0) {
> xattr_data.type = EVM_XATTR_HMAC;
> rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
> - &xattr_data,
> + NULL, &xattr_data,
> sizeof(xattr_data), 0);
> } else if (rc == -ENODATA && (inode->i_opflags & IOP_XATTR)) {
> rc = __vfs_removexattr(dentry, XATTR_NAME_EVM);
> diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> index 809ba70..914cf5f 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -71,7 +71,7 @@ static int ima_fix_xattr(struct dentry *dentry,
> iint->ima_hash->xattr.ng.algo = algo;
> }
> rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
> - &iint->ima_hash->xattr.data[offset],
> + NULL, &iint->ima_hash->xattr.data[offset],
> (sizeof(iint->ima_hash->xattr) - offset) +
> iint->ima_hash->length, 0);
> return rc;
> diff --git a/security/security.c b/security/security.c
> index 4bf0f57..7fce259 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -856,6 +856,12 @@ int security_inode_copy_up_xattr(const char *name)
> }
> EXPORT_SYMBOL(security_inode_copy_up_xattr);
>
> +int security_inode_translate_xattr_to_ns(const char *name, char **tr)
> +{
> + return call_int_hook(inode_translate_xattr_to_ns, 0, name, tr);
> +}
> +EXPORT_SYMBOL(security_inode_translate_xattr_to_ns);
> +
> int security_file_permission(struct file *file, int mask)
> {
> int ret;
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 3daad14..6b29d70 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -646,6 +646,22 @@ static int selinux_is_sblabel_mnt(struct super_block *sb)
> !strcmp(sb->s_type->name, "cgroup2")));
> }
>
> +static char *current_xattr_suffix(void)
> +{
> + if (current_selinux_ns != init_selinux_ns)
> + return current_selinux_ns->xattr_name + XATTR_SECURITY_PREFIX_LEN;
> + else
> + return XATTR_SELINUX_SUFFIX;
> +}
> +
> +static char *current_xattr_name(void)
> +{
> + if (current_selinux_ns != init_selinux_ns)
> + return current_selinux_ns->xattr_name;
> + else
> + return XATTR_NAME_SELINUX;
> +}
> +
> static int sb_finish_set_opts(struct super_block *sb)
> {
> struct superblock_security_struct *sbsec = superblock_security(sb);
> @@ -654,6 +670,8 @@ static int sb_finish_set_opts(struct super_block *sb)
> int rc = 0;
>
> if (sbsec->behavior == SECURITY_FS_USE_XATTR) {
> + char *name;
> +
> /* Make sure that the xattr handler exists and that no
> error other than -ENODATA is returned by getxattr on
> the root directory. -ENODATA is ok, as this may be
> @@ -666,7 +684,9 @@ static int sb_finish_set_opts(struct super_block *sb)
> goto out;
> }
>
> - rc = __vfs_getxattr(root, root_inode, XATTR_NAME_SELINUX, NULL, 0);
> + name = current_xattr_name();
> +
> + rc = __vfs_getxattr(root, root_inode, name, NULL, 0);
> if (rc < 0 && rc != -ENODATA) {
> if (rc == -EOPNOTSUPP)
> printk(KERN_WARNING "SELinux: (dev %s, type "
> @@ -1660,6 +1680,7 @@ static int inode_doinit_with_dentry(struct inode *inode,
> char *context = NULL;
> unsigned len = 0;
> int rc = 0;
> + char *name;
>
> if (isec->initialized == LABEL_INITIALIZED)
> return 0;
> @@ -1729,12 +1750,14 @@ static int inode_doinit_with_dentry(struct inode *inode,
> goto out;
> }
> context[len] = '\0';
> - rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, context, len);
> +
> + name = current_xattr_name();
> + rc = __vfs_getxattr(dentry, inode, name, context, len);
> if (rc == -ERANGE) {
> kfree(context);
>
> /* Need a larger buffer. Query for the right size. */
> - rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, NULL, 0);
> + rc = __vfs_getxattr(dentry, inode, name, NULL, 0);
> if (rc < 0) {
> dput(dentry);
> goto out;
> @@ -1747,7 +1770,7 @@ static int inode_doinit_with_dentry(struct inode *inode,
> goto out;
> }
> context[len] = '\0';
> - rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, context, len);
> + rc = __vfs_getxattr(dentry, inode, name, context, len);
> }
> dput(dentry);
> if (rc < 0) {
> @@ -3167,7 +3190,7 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
> return -EOPNOTSUPP;
>
> if (name)
> - *name = XATTR_SELINUX_SUFFIX;
> + *name = current_xattr_suffix();
>
> if (value && len) {
> rc = security_sid_to_context_force(current_selinux_ns, newsid,
> @@ -3382,6 +3405,10 @@ static bool has_cap_mac_admin(bool audit)
> return true;
> }
>
> +/* TODO:
> + * - audit
> + * - handle raw namespaced xattrs
> + */
> static int selinux_inode_setxattr(struct dentry *dentry, const char *name,
> const void *value, size_t size, int flags)
> {
> @@ -3392,8 +3419,12 @@ static int selinux_inode_setxattr(struct dentry *dentry, const char *name,
> u32 newsid, sid = current_sid();
> int rc = 0;
>
> - if (strcmp(name, XATTR_NAME_SELINUX))
> + if (strcmp(name, XATTR_NAME_SELINUX)) {
> + /* No raw namespaced xattrs, yet */
> + if (!strncmp(name, XATTR_NAME_SELINUX_NS, XATTR_NAME_SELINUX_NS_LEN))
> + return -EPERM;
> return selinux_inode_setotherxattr(dentry, name);
> + }
>
> sbsec = superblock_security(inode->i_sb);
> if (!(sbsec->flags & SBLABEL_MNT))
> @@ -3640,6 +3671,13 @@ static int selinux_inode_copy_up_xattr(const char *name)
> return -EOPNOTSUPP;
> }
>
> +static int selinux_inode_translate_xattr_to_ns(const char *name, char **tr)
> +{
> + if(!strcmp(name, XATTR_NAME_SELINUX))
> + *tr = current_xattr_name();
> + return 0;
> +}
> +
> /* file security operations */
>
> static int selinux_revalidate_file_permission(struct file *file, int mask)
> @@ -6430,10 +6468,11 @@ static int selinux_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen
>
> /*
> * called with inode->i_mutex locked
> + * TODO: namespace translation
> */
> static int selinux_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen)
> {
> - return __vfs_setxattr_noperm(dentry, XATTR_NAME_SELINUX, ctx, ctxlen, 0);
> + return __vfs_setxattr_noperm(dentry, XATTR_NAME_SELINUX, NULL, ctx, ctxlen, 0);
> }
>
> static int selinux_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
> @@ -6647,6 +6686,7 @@ static void selinux_ib_free_security(void *ib_sec)
> LSM_HOOK_INIT(inode_getsecid, selinux_inode_getsecid),
> LSM_HOOK_INIT(inode_copy_up, selinux_inode_copy_up),
> LSM_HOOK_INIT(inode_copy_up_xattr, selinux_inode_copy_up_xattr),
> + LSM_HOOK_INIT(inode_translate_xattr_to_ns, selinux_inode_translate_xattr_to_ns),
>
> LSM_HOOK_INIT(file_permission, selinux_file_permission),
> LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security),
> @@ -6805,7 +6845,7 @@ static void selinux_ib_free_security(void *ib_sec)
>
> static void selinux_ns_free(struct work_struct *work);
>
> -int selinux_ns_create(struct selinux_ns *parent, struct selinux_ns **ns)
> +int selinux_ns_create(struct selinux_ns *parent, struct selinux_ns **ns, const char *name)
> {
> struct selinux_ns *newns;
> int rc;
> @@ -6825,14 +6865,29 @@ int selinux_ns_create(struct selinux_ns *parent, struct selinux_ns **ns)
> if (rc)
> goto err;
>
> + newns->name = kstrdup(name, GFP_KERNEL);
> + if (!newns->name) {
> + rc = -ENOMEM;
> + goto err_avc;
> + }
> +
> + newns->xattr_name = kasprintf(GFP_KERNEL, "%s.ns.%s", XATTR_NAME_SELINUX, name);
> + if (!newns->xattr_name) {
> + rc = -ENOMEM;
> + goto err_avc;
> + }
> +
> if (parent)
> newns->parent = get_selinux_ns(parent);
>
> *ns = newns;
> return 0;
> +err_avc:
> + selinux_avc_free(newns->avc);
> err:
> selinux_ss_free(newns->ss);
> kfree(newns);
> + kfree(newns->name);
> return rc;
> }
>
> @@ -6845,6 +6900,8 @@ static void selinux_ns_free(struct work_struct *work)
> parent = ns->parent;
> selinux_ss_free(ns->ss);
> selinux_avc_free(ns->avc);
> + kfree(ns->name);
> + kfree(ns->xattr_name);
> kfree(ns);
> ns = parent;
> } while (ns && refcount_dec_and_test(&ns->count));
> @@ -6869,7 +6926,7 @@ static __init int selinux_init(void)
>
> printk(KERN_INFO "SELinux: Initializing.\n");
>
> - if (selinux_ns_create(NULL, &init_selinux_ns))
> + if (selinux_ns_create(NULL, &init_selinux_ns, SELINUX_NS_INIT_NAME))
> panic("SELinux: Could not create initial namespace\n");
>
> set_ns_enforcing(init_selinux_ns, selinux_enforcing_boot);
> diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
> index b80f9bd..f5f5a31 100644
> --- a/security/selinux/include/security.h
> +++ b/security/selinux/include/security.h
> @@ -92,6 +92,9 @@ enum {
> /* limitation of boundary depth */
> #define POLICYDB_BOUNDS_MAXDEPTH 4
>
> +/* Name of SELinux initial namespace */
> +#define SELINUX_NS_INIT_NAME "init"
> +
> struct selinux_avc;
> struct selinux_ss;
>
> @@ -108,9 +111,11 @@ struct selinux_ns {
> struct selinux_avc *avc;
> struct selinux_ss *ss;
> struct selinux_ns *parent;
> + char *name;
> + char *xattr_name;
> };
>
> -int selinux_ns_create(struct selinux_ns *parent, struct selinux_ns **ns);
> +int selinux_ns_create(struct selinux_ns *parent, struct selinux_ns **ns, const char *name);
> void __put_selinux_ns(struct selinux_ns *ns);
>
> int selinux_ss_create(struct selinux_ss **ss);
> diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
> index 6c52d24..d190213 100644
> --- a/security/selinux/selinuxfs.c
> +++ b/security/selinux/selinuxfs.c
> @@ -334,9 +334,10 @@ static ssize_t sel_write_unshare(struct file *file, const char __user *buf,
> {
> struct selinux_fs_info *fsi = file_inode(file)->i_sb->s_fs_info;
> struct selinux_ns *ns = fsi->ns;
> + struct cred *cred;
> + struct task_security_struct *tsec;
> char *page;
> ssize_t length;
> - bool set;
> int rc;
>
> if (ns != current_selinux_ns)
> @@ -359,30 +360,32 @@ static ssize_t sel_write_unshare(struct file *file, const char __user *buf,
> if (IS_ERR(page))
> return PTR_ERR(page);
>
> - length = -EINVAL;
> - if (kstrtobool(page, &set))
> - goto out;
> + /* strip any trailing newline */
> + if (page[strlen(page) - 1] == '\n')
> + page[strlen(page) - 1] = 0;
>
> - if (set) {
> - struct cred *cred = prepare_creds();
> - struct task_security_struct *tsec;
> + /* TODO: check for uniqueness! */
> + if (!strcmp(SELINUX_NS_INIT_NAME, page)) {
> + length = -EINVAL;
> + goto out;
> + }
>
> - if (!cred) {
> - length = -ENOMEM;
> - goto out;
> - }
> - tsec = cred->security;
> - if (selinux_ns_create(ns, &tsec->ns)) {
> - abort_creds(cred);
> - length = -ENOMEM;
> - goto out;
> - }
> - tsec->osid = tsec->sid = SECINITSID_KERNEL;
> - tsec->exec_sid = tsec->create_sid = tsec->keycreate_sid =
> - tsec->sockcreate_sid = SECSID_NULL;
> - tsec->parent_cred = get_current_cred();
> - commit_creds(cred);
> + cred = prepare_creds();
> + if (!cred) {
> + length = -ENOMEM;
> + goto out;
> + }
> + tsec = cred->security;
> + if (selinux_ns_create(ns, &tsec->ns, page)) {
> + abort_creds(cred);
> + length = -ENOMEM;
> + goto out;
> }
> + tsec->osid = tsec->sid = SECINITSID_KERNEL;
> + tsec->exec_sid = tsec->create_sid = tsec->keycreate_sid =
> + tsec->sockcreate_sid = SECSID_NULL;
> + tsec->parent_cred = get_current_cred();
> + commit_creds(cred);
>
> length = count;
> out:
> @@ -390,8 +393,22 @@ static ssize_t sel_write_unshare(struct file *file, const char __user *buf,
> return length;
> }
>
> +static ssize_t sel_read_unshare(struct file *file, char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + struct selinux_fs_info *fsi = file_inode(file)->i_sb->s_fs_info;
> + struct selinux_ns *ns = fsi->ns;
> + char *name = ns->name;
> +
> + if (ns != current_selinux_ns)
> + return -EPERM;
> +
> + return simple_read_from_buffer(buf, count, ppos, name, strlen(name));
> +}
> +
> static const struct file_operations sel_unshare_ops = {
> .write = sel_write_unshare,
> + .read = sel_read_unshare,
> .llseek = generic_file_llseek,
> };
>
> @@ -2021,7 +2038,7 @@ static int sel_fill_super(struct super_block *sb, void *data, int silent)
> [SEL_POLICY] = {"policy", &sel_policy_ops, S_IRUGO},
> [SEL_VALIDATE_TRANS] = {"validatetrans", &sel_transition_ops,
> S_IWUGO},
> - [SEL_UNSHARE] = {"unshare", &sel_unshare_ops, 0222},
> + [SEL_UNSHARE] = {"unshare", &sel_unshare_ops, 0666},
> /* last one */ {""}
> };
>
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 319add3..5ea841f 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -4591,7 +4591,7 @@ static int smack_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen)
>
> static int smack_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen)
> {
> - return __vfs_setxattr_noperm(dentry, XATTR_NAME_SMACK, ctx, ctxlen, 0);
> + return __vfs_setxattr_noperm(dentry, XATTR_NAME_SMACK, NULL, ctx, ctxlen, 0);
> }
>
> static int smack_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
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^ permalink raw reply [flat|nested] 11+ messages in thread
* [RFC v0.1][PATCH] selinuxns: extend namespace support to security.selinux xattrs
2017-10-30 10:04 [RFC v0.1][PATCH] selinuxns: extend namespace support to security.selinux xattrs James Morris
2017-10-30 15:55 ` Casey Schaufler
@ 2017-10-30 19:16 ` Stephen Smalley
2017-10-31 3:11 ` James Morris
1 sibling, 1 reply; 11+ messages in thread
From: Stephen Smalley @ 2017-10-30 19:16 UTC (permalink / raw)
To: linux-security-module
On Mon, 2017-10-30 at 21:04 +1100, James Morris wrote:
> This is a proof-of-concept patch to demonstrate an approach to
> supporting?
> SELinux namespaces for security.selinux xattr labels.
>
> This follows on from the experimental SELinux namespace code posted
> by?
> Stephen: https://marc.info/?l=selinux&m=150696042210126&w=2
>
> In the initial code, namespacing was only implemented for in-core
> inodes?
> per this posting: https://marc.info/?l=selinux&m=150696324110943&w=2
>
> In this patch, namespacing is extended to on-disk inode labels
> (xattrs),?
> transparently to normal applications.
>
> A summary of the approach is as follows:
>
> 1. Add a namespace "name" field to the SELinux namespace, which is?
> ???specified by writing to the selinuxfs unshare node (instead of
> the?
> ???current boolean value) during namespace creation.
>
> ???e.g. if the namespace name is "vm8", run:?
>
> ???# echo vm8 > /sys/fs/selinux/unshare
>
> ???followed by the remaining steps from the original code.
>
> ???This value can also be read back from the node, and the initial
> SELinux?
> ???namespace is internally set to "init".
>
> ???
> 2. Transparently modify SELinux xattrs so that any non-initial
> namespace?
> ???xattrs include the namespace name.?
>
> ???e.g. if the namespace name is "vm6", the "security.selinux" xattr
> is?
> ???translated in the kernel to "security.selinux.ns.vm6" for disk
> read and
> ???write of xattrs.
>
> ???This allows each SELinux namespace to independently manage its
> own?
> ???xattr labels, transparently to applications. Namespaces only see
> their?
> ???own xattrs, which are acted on by their own namespaced policies.
>
> ???Note that the "init" namespace performs no translation for apps,
> it?
> ???just uses regular old security.selinux xattrs.
>
>
> Some examples:
>
> ? [root at test]# cat /sys/fs/selinux/unshare?
> ? vm8
>
> ? [root at test]# touch testfile
>
> ? [root at test]# ls -Z testfile?
> ? -rw-r--r--. root root unconfined_u:object_r:unlabeled_t:s0 testfile
>
> ? [root at test]# getfattr -n security.selinux testfile?
> ? # file: testfile
> ? security.selinux="unconfined_u:object_r:unlabeled_t:s0"
>
> ? # restorecon -v testfile?
> ? restorecon reset /root/selinux/testfile context
> unconfined_u:object_r:unlabeled_t:s0-
> >unconfined_u:object_r:admin_home_t:s0
>
> ? [root at test]# getfattr -n security.selinux testfile?
> ? # file: testfile
> ? security.selinux="unconfined_u:object_r:admin_home_t:s0"
>
> ? [root at test]# chcon -t etc_t testfile?
>
> ? [root at test]# getfattr -n security.selinux testfile?
> ? # file: testfile
> ? security.selinux="unconfined_u:object_r:etc_t:s0"
>
>
> Ok, so this all looks pretty normal, but what's happening on disk is
> not.??
> > From the init namespace, I'll access the same file:
>
> ? [root at test]# cat /sys/fs/selinux/unshare?
> ? init
>
> ? [root at test]# ls -Z testfile?
> ? -rw-r--r--. root root system_u:object_r:unlabeled_t:s0 testfile
>
> ? [root at test]# getfattr -n security.selinux testfile?
> ? # file: testfile
> ? security.selinux="system_u:object_r:unlabeled_t:s0"
>
> There is in fact no security.selinux xattr yet on this file as it
> was?
> created in a different namespace and only initialized there.??What
> you're?
> seeing here is the default unlabeled label.??Dumping out the xattrs
> shows?
> what's on disk:
>
> ? [root at test]# getfattr -d -m . testfile?
> ? # file: testfile
> ? security.selinux.ns.vm8="unconfined_u:object_r:etc_t:s0"
>
> The xattr belonging to "vm8" is there but not being interpreted
> outside?
> that namespace.??Let's give it a proper label for the init ns:
>
> ? # restorecon -v testfile?
> ? restorecon reset /root/selinux/testfile context
> system_u:object_r:unlabeled_t:s0->system_u:object_r:admin_home_t:s0
>
> ? [root at test]# getfattr -d -m . testfile?
> ? # file: testfile
> ? security.selinux="system_u:object_r:admin_home_t:s0"
> ? security.selinux.ns.vm8="unconfined_u:object_r:etc_t:s0"
>
> ? [root at test]# ls -Z testfile?
> ? -rw-r--r--. root root system_u:object_r:admin_home_t:s0 testfile
>
> And if you go into the vm8 namespace you'll see the label there is:
>
> ? [root at test]# echo??vm8 > /sys/fs/selinux/unshare?
> ? [root at test]# unshare -m -n
> ? [root at test]# umount /sys/fs/selinux && mount -t selinuxfs none
> /sys/fs/selinux && load_policy
> ? [root at test]# runcon
> unconfined_u:unconfined_r:unconfined_t:s0:c0.c1023 /bin/bash
> ? [root at test]# setenforce 1
>
> ? [root at test]# ls -Z testfile?
> ? -rw-r--r--. root root unconfined_u:object_r:etc_t:s0???testfile
>
>
> I hope that demonstrates the concept well enough: that there are
> zero?
> changes for applications and the namespaced policy always uses
> xattrs?
> belonging to that namespace.
>
> The prototype code is far from complete, and also needs to implement?
> support for listxattr and removexattr, as well as provide
> appropriate?
> administrative access to raw (untranslated) xattrs, which you can?
> currently see from any ns but not write at all.??Other TODO items
> include?
> accounting for dynamic xattr name size, nested policy enforcement,?
> uniqueness of namespace names, and better audit support.
>
> Comments?
Thanks, interesting approach. One drawback is that it doesn't presently
support any form of inheritance of labels from the parent namespace, so
files that are shared read-only from the init namespace will show up as
unlabeled in the child namespace until they are assigned the namespaced
attributes. This for example breaks running the selinux-testsuite with
this patch applied (unless perhaps you run restorecon -R / after
unsharing); otherwise just trying to invoke /usr/bin/runcon will fail
since it is unlabeled in the child. It seems like we should provide
some form of inheritance from the parent when there is no xattr for the
namespace itself.
Another potential concern is that files created in a non-init namespace
are left completely unlabeled in the init namespace (or in any parent).
As long as access to unlabeled is tightly controlled, this might
not be a problem, but I'm not sure that's guaranteed by the refpolicy
or Fedora/RHEL policies. We might want to initialize an xattr at every
level of the namespace hierarchy when a new file is created based on
the process and parent directory labels and policy at that level.
Otherwise, we lose all provenance information for the file outside of
the namespace. For example, suppose I want to leak information out of
my category set; I unshare and create files with the information, and
they appear in the init namespace with no categories.
>
> Patch below...
>
> ---
> From: James Morris <james.l.morris@oracle.com>
> Date: Mon, 30 Oct 2017 19:10:36 +1100
> Subject: [PATCH] selinuxns: extend namespace support to
> security.selinux xattrs
>
> Prototype code only.
>
> Signed-off-by: James Morris <james.l.morris@oracle.com>
> ---
> ?fs/xattr.c????????????????????????????| 12 ++++--
> ?include/linux/lsm_hooks.h?????????????|??2 +
> ?include/linux/security.h??????????????|??6 +++
> ?include/linux/xattr.h?????????????????|??2 +-
> ?include/uapi/linux/xattr.h????????????|??3 ++
> ?security/integrity/evm/evm_crypto.c???|??2 +-
> ?security/integrity/ima/ima_appraise.c |??2 +-
> ?security/security.c???????????????????|??6 +++
> ?security/selinux/hooks.c??????????????| 75
> ++++++++++++++++++++++++++++++-----
> ?security/selinux/include/security.h???|??7 +++-
> ?security/selinux/selinuxfs.c??????????| 63 ++++++++++++++++++-------
> ----
> ?security/smack/smack_lsm.c????????????|??2 +-
> ?12 files changed, 142 insertions(+), 40 deletions(-)
>
> diff --git a/fs/xattr.c b/fs/xattr.c
> index 4424f7f..d8107b7 100644
> --- a/fs/xattr.c
> +++ b/fs/xattr.c
> @@ -157,6 +157,7 @@
> ? *
> ? *??@dentry - object to perform setxattr on
> ? *??@name - xattr name to set
> + *??@nsname - namespaced xattr name, use instead of @name if set
> ? *??@value - value to set @name to
> ? *??@size - size of @value
> ? *??@flags - flags to pass into filesystem operations
> @@ -168,7 +169,7 @@
> ? *??permission checks.
> ? */
> ?int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
> - const void *value, size_t size, int flags)
> + const char *nsname, const void *value, size_t size,
> int flags)
> ?{
> ? struct inode *inode = dentry->d_inode;
> ? int error = -EAGAIN;
> @@ -178,7 +179,8 @@ int __vfs_setxattr_noperm(struct dentry *dentry,
> const char *name,
> ? if (issec)
> ? inode->i_flags &= ~S_NOSEC;
> ? if (inode->i_opflags & IOP_XATTR) {
> - error = __vfs_setxattr(dentry, inode, name, value,
> size, flags);
> + error = __vfs_setxattr(dentry, inode, nsname?:name,
> value,
> + size, flags);
> ? if (!error) {
> ? fsnotify_xattr(dentry);
> ? security_inode_post_setxattr(dentry, name,
> value,
> @@ -211,6 +213,7 @@ int __vfs_setxattr_noperm(struct dentry *dentry,
> const char *name,
> ?{
> ? struct inode *inode = dentry->d_inode;
> ? int error;
> + char *nsname = NULL;
> ?
> ? error = xattr_permission(inode, name, MAY_WRITE);
> ? if (error)
> @@ -221,8 +224,11 @@ int __vfs_setxattr_noperm(struct dentry *dentry,
> const char *name,
> ? if (error)
> ? goto out;
> ?
> - error = __vfs_setxattr_noperm(dentry, name, value, size,
> flags);
> + error = security_inode_translate_xattr_to_ns(name, &nsname);
> + if (error)
> + goto out;
> ?
> + error = __vfs_setxattr_noperm(dentry, name, nsname, value,
> size, flags);
> ?out:
> ? inode_unlock(inode);
> ? return error;
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index c925812..e4eb43e 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -1480,6 +1480,7 @@
> ? void (*inode_getsecid)(struct inode *inode, u32 *secid);
> ? int (*inode_copy_up)(struct dentry *src, struct cred **new);
> ? int (*inode_copy_up_xattr)(const char *name);
> + int (*inode_translate_xattr_to_ns)(const char *name, char
> **tr);
> ?
> ? int (*file_permission)(struct file *file, int mask);
> ? int (*file_alloc_security)(struct file *file);
> @@ -1760,6 +1761,7 @@ struct security_hook_heads {
> ? struct list_head inode_getsecid;
> ? struct list_head inode_copy_up;
> ? struct list_head inode_copy_up_xattr;
> + struct list_head inode_translate_xattr_to_ns;
> ? struct list_head file_permission;
> ? struct list_head file_alloc_security;
> ? struct list_head file_free_security;
> diff --git a/include/linux/security.h b/include/linux/security.h
> index ce62659..64297e1 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -302,6 +302,7 @@ void security_inode_post_setxattr(struct dentry
> *dentry, const char *name,
> ?void security_inode_getsecid(struct inode *inode, u32 *secid);
> ?int security_inode_copy_up(struct dentry *src, struct cred **new);
> ?int security_inode_copy_up_xattr(const char *name);
> +int security_inode_translate_xattr_to_ns(const char *name, char
> **tr);
> ?int security_file_permission(struct file *file, int mask);
> ?int security_file_alloc(struct file *file);
> ?void security_file_free(struct file *file);
> @@ -808,6 +809,11 @@ static inline int
> security_inode_copy_up_xattr(const char *name)
> ? return -EOPNOTSUPP;
> ?}
> ?
> +static inline int security_inode_translate_xattr_to_ns(const char
> *name, char **tr)
> +{
> + return 0;
> +}
> +
> ?static inline int security_file_permission(struct file *file, int
> mask)
> ?{
> ? return 0;
> diff --git a/include/linux/xattr.h b/include/linux/xattr.h
> index e77605a..c25eb8a 100644
> --- a/include/linux/xattr.h
> +++ b/include/linux/xattr.h
> @@ -50,7 +50,7 @@ struct xattr {
> ?ssize_t vfs_getxattr(struct dentry *, const char *, void *, size_t);
> ?ssize_t vfs_listxattr(struct dentry *d, char *list, size_t size);
> ?int __vfs_setxattr(struct dentry *, struct inode *, const char *,
> const void *, size_t, int);
> -int __vfs_setxattr_noperm(struct dentry *, const char *, const void
> *, size_t, int);
> +int __vfs_setxattr_noperm(struct dentry *, const char *, const char
> *, const void *, size_t, int);
> ?int vfs_setxattr(struct dentry *, const char *, const void *,
> size_t, int);
> ?int __vfs_removexattr(struct dentry *, const char *);
> ?int vfs_removexattr(struct dentry *, const char *);
> diff --git a/include/uapi/linux/xattr.h b/include/uapi/linux/xattr.h
> index 1590c49..528a5f7 100644
> --- a/include/uapi/linux/xattr.h
> +++ b/include/uapi/linux/xattr.h
> @@ -51,6 +51,9 @@
> ?
> ?#define XATTR_SELINUX_SUFFIX "selinux"
> ?#define XATTR_NAME_SELINUX XATTR_SECURITY_PREFIX
> XATTR_SELINUX_SUFFIX
> +#define XATTR_SELINUX_NS_INFIX ".ns."
> +#define XATTR_NAME_SELINUX_NS XATTR_NAME_SELINUX
> XATTR_SELINUX_NS_INFIX
> +#define XATTR_NAME_SELINUX_NS_LEN (sizeof(XATTR_NAME_SELINUX_NS) -
> 1)
> ?
> ?#define XATTR_SMACK_SUFFIX "SMACK64"
> ?#define XATTR_SMACK_IPIN "SMACK64IPIN"
> diff --git a/security/integrity/evm/evm_crypto.c
> b/security/integrity/evm/evm_crypto.c
> index 1d32cd2..2249186 100644
> --- a/security/integrity/evm/evm_crypto.c
> +++ b/security/integrity/evm/evm_crypto.c
> @@ -260,7 +260,7 @@ int evm_update_evmxattr(struct dentry *dentry,
> const char *xattr_name,
> ? if (rc == 0) {
> ? xattr_data.type = EVM_XATTR_HMAC;
> ? rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
> - ???&xattr_data,
> + ???NULL, &xattr_data,
> ? ???sizeof(xattr_data), 0);
> ? } else if (rc == -ENODATA && (inode->i_opflags & IOP_XATTR))
> {
> ? rc = __vfs_removexattr(dentry, XATTR_NAME_EVM);
> diff --git a/security/integrity/ima/ima_appraise.c
> b/security/integrity/ima/ima_appraise.c
> index 809ba70..914cf5f 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -71,7 +71,7 @@ static int ima_fix_xattr(struct dentry *dentry,
> ? iint->ima_hash->xattr.ng.algo = algo;
> ? }
> ? rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
> - ???&iint->ima_hash-
> >xattr.data[offset],
> + ???NULL, &iint->ima_hash-
> >xattr.data[offset],
> ? ???(sizeof(iint->ima_hash->xattr) -
> offset) +
> ? ???iint->ima_hash->length, 0);
> ? return rc;
> diff --git a/security/security.c b/security/security.c
> index 4bf0f57..7fce259 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -856,6 +856,12 @@ int security_inode_copy_up_xattr(const char
> *name)
> ?}
> ?EXPORT_SYMBOL(security_inode_copy_up_xattr);
> ?
> +int security_inode_translate_xattr_to_ns(const char *name, char
> **tr)
> +{
> + return call_int_hook(inode_translate_xattr_to_ns, 0, name,
> tr);
> +}
> +EXPORT_SYMBOL(security_inode_translate_xattr_to_ns);
> +
> ?int security_file_permission(struct file *file, int mask)
> ?{
> ? int ret;
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 3daad14..6b29d70 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -646,6 +646,22 @@ static int selinux_is_sblabel_mnt(struct
> super_block *sb)
> ? ??!strcmp(sb->s_type->name, "cgroup2")));
> ?}
> ?
> +static char *current_xattr_suffix(void)
> +{
> + if (current_selinux_ns != init_selinux_ns)
> + return current_selinux_ns->xattr_name +
> XATTR_SECURITY_PREFIX_LEN;
> + else
> + return XATTR_SELINUX_SUFFIX;
> +}
> +
> +static char *current_xattr_name(void)
> +{
> + if (current_selinux_ns != init_selinux_ns)
> + return current_selinux_ns->xattr_name;
> + else
> + return XATTR_NAME_SELINUX;
> +}
Is there a reason we can't just set up init_selinux_ns->xattr_name to
XATTR_NAME_SELINUX during init and avoid special-casing it here?
> +
> ?static int sb_finish_set_opts(struct super_block *sb)
> ?{
> ? struct superblock_security_struct *sbsec =
> superblock_security(sb);
> @@ -654,6 +670,8 @@ static int sb_finish_set_opts(struct super_block
> *sb)
> ? int rc = 0;
> ?
> ? if (sbsec->behavior == SECURITY_FS_USE_XATTR) {
> + char *name;
> +
> ? /* Make sure that the xattr handler exists and that
> no
> ? ???error other than -ENODATA is returned by getxattr
> on
> ? ???the root directory.??-ENODATA is ok, as this may
> be
> @@ -666,7 +684,9 @@ static int sb_finish_set_opts(struct super_block
> *sb)
> ? goto out;
> ? }
> ?
> - rc = __vfs_getxattr(root, root_inode,
> XATTR_NAME_SELINUX, NULL, 0);
> + name = current_xattr_name();
> +
> + rc = __vfs_getxattr(root, root_inode, name, NULL,
> 0);
> ? if (rc < 0 && rc != -ENODATA) {
> ? if (rc == -EOPNOTSUPP)
> ? printk(KERN_WARNING "SELinux: (dev
> %s, type "
> @@ -1660,6 +1680,7 @@ static int inode_doinit_with_dentry(struct
> inode *inode,
> ? char *context = NULL;
> ? unsigned len = 0;
> ? int rc = 0;
> + char *name;
> ?
> ? if (isec->initialized == LABEL_INITIALIZED)
> ? return 0;
> @@ -1729,12 +1750,14 @@ static int inode_doinit_with_dentry(struct
> inode *inode,
> ? goto out;
> ? }
> ? context[len] = '\0';
> - rc = __vfs_getxattr(dentry, inode,
> XATTR_NAME_SELINUX, context, len);
> +
> + name = current_xattr_name();
> + rc = __vfs_getxattr(dentry, inode, name, context,
> len);
> ? if (rc == -ERANGE) {
> ? kfree(context);
> ?
> ? /* Need a larger buffer.??Query for the
> right size. */
> - rc = __vfs_getxattr(dentry, inode,
> XATTR_NAME_SELINUX, NULL, 0);
> + rc = __vfs_getxattr(dentry, inode, name,
> NULL, 0);
> ? if (rc < 0) {
> ? dput(dentry);
> ? goto out;
> @@ -1747,7 +1770,7 @@ static int inode_doinit_with_dentry(struct
> inode *inode,
> ? goto out;
> ? }
> ? context[len] = '\0';
> - rc = __vfs_getxattr(dentry, inode,
> XATTR_NAME_SELINUX, context, len);
> + rc = __vfs_getxattr(dentry, inode, name,
> context, len);
> ? }
> ? dput(dentry);
> ? if (rc < 0) {
> @@ -3167,7 +3190,7 @@ static int selinux_inode_init_security(struct
> inode *inode, struct inode *dir,
> ? return -EOPNOTSUPP;
> ?
> ? if (name)
> - *name = XATTR_SELINUX_SUFFIX;
> + *name = current_xattr_suffix();
> ?
> ? if (value && len) {
> ? rc =
> security_sid_to_context_force(current_selinux_ns, newsid,
> @@ -3382,6 +3405,10 @@ static bool has_cap_mac_admin(bool audit)
> ? return true;
> ?}
> ?
> +/* TODO:
> + * - audit
> + * - handle raw namespaced xattrs
> + */
> ?static int selinux_inode_setxattr(struct dentry *dentry, const char
> *name,
> ? ??const void *value, size_t size,
> int flags)
> ?{
> @@ -3392,8 +3419,12 @@ static int selinux_inode_setxattr(struct
> dentry *dentry, const char *name,
> ? u32 newsid, sid = current_sid();
> ? int rc = 0;
> ?
> - if (strcmp(name, XATTR_NAME_SELINUX))
> + if (strcmp(name, XATTR_NAME_SELINUX)) {
> + /* No raw namespaced xattrs, yet */
> + if (!strncmp(name, XATTR_NAME_SELINUX_NS,
> XATTR_NAME_SELINUX_NS_LEN))
> + return -EPERM;
> ? return selinux_inode_setotherxattr(dentry, name);
> + }
> ?
> ? sbsec = superblock_security(inode->i_sb);
> ? if (!(sbsec->flags & SBLABEL_MNT))
> @@ -3640,6 +3671,13 @@ static int selinux_inode_copy_up_xattr(const
> char *name)
> ? return -EOPNOTSUPP;
> ?}
> ?
> +static int selinux_inode_translate_xattr_to_ns(const char *name,
> char **tr)
> +{
> + if(!strcmp(name, XATTR_NAME_SELINUX))
> + *tr = current_xattr_name();
> + return 0;
> +}
> +
> ?/* file security operations */
> ?
> ?static int selinux_revalidate_file_permission(struct file *file, int
> mask)
> @@ -6430,10 +6468,11 @@ static int selinux_inode_notifysecctx(struct
> inode *inode, void *ctx, u32 ctxlen
> ?
> ?/*
> ? * called with inode->i_mutex locked
> + * TODO: namespace translation
> ? */
> ?static int selinux_inode_setsecctx(struct dentry *dentry, void *ctx,
> u32 ctxlen)
> ?{
> - return __vfs_setxattr_noperm(dentry, XATTR_NAME_SELINUX,
> ctx, ctxlen, 0);
> + return __vfs_setxattr_noperm(dentry, XATTR_NAME_SELINUX,
> NULL, ctx, ctxlen, 0);
> ?}
> ?
> ?static int selinux_inode_getsecctx(struct inode *inode, void **ctx,
> u32 *ctxlen)
> @@ -6647,6 +6686,7 @@ static void selinux_ib_free_security(void
> *ib_sec)
> ? LSM_HOOK_INIT(inode_getsecid, selinux_inode_getsecid),
> ? LSM_HOOK_INIT(inode_copy_up, selinux_inode_copy_up),
> ? LSM_HOOK_INIT(inode_copy_up_xattr,
> selinux_inode_copy_up_xattr),
> + LSM_HOOK_INIT(inode_translate_xattr_to_ns,
> selinux_inode_translate_xattr_to_ns),
> ?
> ? LSM_HOOK_INIT(file_permission, selinux_file_permission),
> ? LSM_HOOK_INIT(file_alloc_security,
> selinux_file_alloc_security),
> @@ -6805,7 +6845,7 @@ static void selinux_ib_free_security(void
> *ib_sec)
> ?
> ?static void selinux_ns_free(struct work_struct *work);
> ?
> -int selinux_ns_create(struct selinux_ns *parent, struct selinux_ns
> **ns)
> +int selinux_ns_create(struct selinux_ns *parent, struct selinux_ns
> **ns, const char *name)
> ?{
> ? struct selinux_ns *newns;
> ? int rc;
> @@ -6825,14 +6865,29 @@ int selinux_ns_create(struct selinux_ns
> *parent, struct selinux_ns **ns)
> ? if (rc)
> ? goto err;
> ?
> + newns->name = kstrdup(name, GFP_KERNEL);
> + if (!newns->name) {
> + rc = -ENOMEM;
> + goto err_avc;
> +????????}
> +
> + newns->xattr_name = kasprintf(GFP_KERNEL, "%s.ns.%s",
> XATTR_NAME_SELINUX, name);
> + if (!newns->xattr_name) {
> + rc = -ENOMEM;
> + goto err_avc;
> + }
> +
> ? if (parent)
> ? newns->parent = get_selinux_ns(parent);
> ?
> ? *ns = newns;
> ? return 0;
> +err_avc:
> + selinux_avc_free(newns->avc);
> ?err:
> ? selinux_ss_free(newns->ss);
> ? kfree(newns);
> + kfree(newns->name);
> ? return rc;
> ?}
> ?
> @@ -6845,6 +6900,8 @@ static void selinux_ns_free(struct work_struct
> *work)
> ? parent = ns->parent;
> ? selinux_ss_free(ns->ss);
> ? selinux_avc_free(ns->avc);
> + kfree(ns->name);
> + kfree(ns->xattr_name);
> ? kfree(ns);
> ? ns = parent;
> ? } while (ns && refcount_dec_and_test(&ns->count));
> @@ -6869,7 +6926,7 @@ static __init int selinux_init(void)
> ?
> ? printk(KERN_INFO "SELinux:??Initializing.\n");
> ?
> - if (selinux_ns_create(NULL, &init_selinux_ns))
> + if (selinux_ns_create(NULL, &init_selinux_ns,
> SELINUX_NS_INIT_NAME))
> ? panic("SELinux: Could not create initial
> namespace\n");
> ?
> ? set_ns_enforcing(init_selinux_ns, selinux_enforcing_boot);
> diff --git a/security/selinux/include/security.h
> b/security/selinux/include/security.h
> index b80f9bd..f5f5a31 100644
> --- a/security/selinux/include/security.h
> +++ b/security/selinux/include/security.h
> @@ -92,6 +92,9 @@ enum {
> ?/* limitation of boundary depth??*/
> ?#define POLICYDB_BOUNDS_MAXDEPTH 4
> ?
> +/* Name of SELinux initial namespace */
> +#define SELINUX_NS_INIT_NAME "init"
> +
> ?struct selinux_avc;
> ?struct selinux_ss;
> ?
> @@ -108,9 +111,11 @@ struct selinux_ns {
> ? struct selinux_avc *avc;
> ? struct selinux_ss *ss;
> ? struct selinux_ns *parent;
> + char *name;
> + char *xattr_name;
> ?};
> ?
> -int selinux_ns_create(struct selinux_ns *parent, struct selinux_ns
> **ns);
> +int selinux_ns_create(struct selinux_ns *parent, struct selinux_ns
> **ns, const char *name);
> ?void __put_selinux_ns(struct selinux_ns *ns);
> ?
> ?int selinux_ss_create(struct selinux_ss **ss);
> diff --git a/security/selinux/selinuxfs.c
> b/security/selinux/selinuxfs.c
> index 6c52d24..d190213 100644
> --- a/security/selinux/selinuxfs.c
> +++ b/security/selinux/selinuxfs.c
> @@ -334,9 +334,10 @@ static ssize_t sel_write_unshare(struct file
> *file, const char __user *buf,
> ?{
> ? struct selinux_fs_info *fsi = file_inode(file)->i_sb-
> >s_fs_info;
> ? struct selinux_ns *ns = fsi->ns;
> + struct cred *cred;
> + struct task_security_struct *tsec;
> ? char *page;
> ? ssize_t length;
> - bool set;
> ? int rc;
> ?
> ? if (ns != current_selinux_ns)
> @@ -359,30 +360,32 @@ static ssize_t sel_write_unshare(struct file
> *file, const char __user *buf,
> ? if (IS_ERR(page))
> ? return PTR_ERR(page);
> ?
> - length = -EINVAL;
> - if (kstrtobool(page, &set))
> - goto out;
> + /* strip any trailing newline */
> + if (page[strlen(page) - 1] == '\n')
> + page[strlen(page) - 1] = 0;
> ?
> - if (set) {
> - struct cred *cred = prepare_creds();
> - struct task_security_struct *tsec;
> + /* TODO: check for uniqueness! */
> + if (!strcmp(SELINUX_NS_INIT_NAME, page)) {
> + length = -EINVAL;
> + goto out;
> + }
> ?
> - if (!cred) {
> - length = -ENOMEM;
> - goto out;
> - }
> - tsec = cred->security;
> - if (selinux_ns_create(ns, &tsec->ns)) {
> - abort_creds(cred);
> - length = -ENOMEM;
> - goto out;
> - }
> - tsec->osid = tsec->sid = SECINITSID_KERNEL;
> - tsec->exec_sid = tsec->create_sid = tsec-
> >keycreate_sid =
> - tsec->sockcreate_sid = SECSID_NULL;
> - tsec->parent_cred = get_current_cred();
> - commit_creds(cred);
> + cred = prepare_creds();
> + if (!cred) {
> + length = -ENOMEM;
> + goto out;
> + }
> + tsec = cred->security;
> + if (selinux_ns_create(ns, &tsec->ns, page)) {
> + abort_creds(cred);
> + length = -ENOMEM;
> + goto out;
> ? }
> + tsec->osid = tsec->sid = SECINITSID_KERNEL;
> + tsec->exec_sid = tsec->create_sid = tsec->keycreate_sid =
> + tsec->sockcreate_sid = SECSID_NULL;
> + tsec->parent_cred = get_current_cred();
> + commit_creds(cred);
> ?
> ? length = count;
> ?out:
> @@ -390,8 +393,22 @@ static ssize_t sel_write_unshare(struct file
> *file, const char __user *buf,
> ? return length;
> ?}
> ?
> +static ssize_t sel_read_unshare(struct file *file, char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + struct selinux_fs_info *fsi = file_inode(file)->i_sb-
> >s_fs_info;
> + struct selinux_ns *ns = fsi->ns;
> + char *name = ns->name;
> +
> + if (ns != current_selinux_ns)
> + return -EPERM;
> +
> + return simple_read_from_buffer(buf, count, ppos, name,
> strlen(name));
> +}
> +
> ?static const struct file_operations sel_unshare_ops = {
> ? .write = sel_write_unshare,
> + .read = sel_read_unshare,
> ? .llseek = generic_file_llseek,
> ?};
> ?
> @@ -2021,7 +2038,7 @@ static int sel_fill_super(struct super_block
> *sb, void *data, int silent)
> ? [SEL_POLICY] = {"policy", &sel_policy_ops, S_IRUGO},
> ? [SEL_VALIDATE_TRANS] = {"validatetrans",
> &sel_transition_ops,
> ? S_IWUGO},
> - [SEL_UNSHARE] = {"unshare", &sel_unshare_ops, 0222},
> + [SEL_UNSHARE] = {"unshare", &sel_unshare_ops, 0666},
> ? /* last one */ {""}
> ? };
> ?
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 319add3..5ea841f 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -4591,7 +4591,7 @@ static int smack_inode_notifysecctx(struct
> inode *inode, void *ctx, u32 ctxlen)
> ?
> ?static int smack_inode_setsecctx(struct dentry *dentry, void *ctx,
> u32 ctxlen)
> ?{
> - return __vfs_setxattr_noperm(dentry, XATTR_NAME_SMACK, ctx,
> ctxlen, 0);
> + return __vfs_setxattr_noperm(dentry, XATTR_NAME_SMACK, NULL,
> ctx, ctxlen, 0);
> ?}
> ?
> ?static int smack_inode_getsecctx(struct inode *inode, void **ctx,
> u32 *ctxlen)
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^ permalink raw reply [flat|nested] 11+ messages in thread
* [RFC v0.1][PATCH] selinuxns: extend namespace support to security.selinux xattrs
2017-10-30 19:16 ` Stephen Smalley
@ 2017-10-31 3:11 ` James Morris
2017-10-31 13:00 ` Stephen Smalley
0 siblings, 1 reply; 11+ messages in thread
From: James Morris @ 2017-10-31 3:11 UTC (permalink / raw)
To: linux-security-module
On Mon, 30 Oct 2017, Stephen Smalley wrote:
> Thanks, interesting approach. One drawback is that it doesn't presently
> support any form of inheritance of labels from the parent namespace, so
> files that are shared read-only from the init namespace will show up as
> unlabeled in the child namespace until they are assigned the namespaced
> attributes. This for example breaks running the selinux-testsuite with
> this patch applied (unless perhaps you run restorecon -R / after
> unsharing); otherwise just trying to invoke /usr/bin/runcon will fail
> since it is unlabeled in the child. It seems like we should provide
> some form of inheritance from the parent when there is no xattr for the
> namespace itself.
I was assuming that practical use of this would involve doing a filesystem
relabel under the newly loaded policy, on first instantiation at least.
We could try adding an selinuxfs node to specify default handling of
unlabeled files in a child namespace, and write to that after mounting
selinuxfs in that namespace.
e.g. echo inherit > /sys/fs/selinux/parent_ns_labels
or something.
>
> Another potential concern is that files created in a non-init namespace
> are left completely unlabeled in the init namespace (or in any parent).
> As long as access to unlabeled is tightly controlled, this might
> not be a problem, but I'm not sure that's guaranteed by the refpolicy
> or Fedora/RHEL policies. We might want to initialize an xattr at every
> level of the namespace hierarchy when a new file is created based on
> the process and parent directory labels and policy at that level.
> Otherwise, we lose all provenance information for the file outside of
> the namespace.
Ok.
> For example, suppose I want to leak information out of
> my category set; I unshare and create files with the information, and
> they appear in the init namespace with no categories.
Nice :)
--
James Morris
<james.l.morris@oracle.com>
--
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^ permalink raw reply [flat|nested] 11+ messages in thread
* [RFC v0.1][PATCH] selinuxns: extend namespace support to security.selinux xattrs
2017-10-31 3:11 ` James Morris
@ 2017-10-31 13:00 ` Stephen Smalley
2017-10-31 14:04 ` Stephen Smalley
0 siblings, 1 reply; 11+ messages in thread
From: Stephen Smalley @ 2017-10-31 13:00 UTC (permalink / raw)
To: linux-security-module
On Tue, 2017-10-31 at 14:11 +1100, James Morris wrote:
> On Mon, 30 Oct 2017, Stephen Smalley wrote:
>
> > Thanks, interesting approach. One drawback is that it doesn't
> > presently
> > support any form of inheritance of labels from the parent
> > namespace, so
> > files that are shared read-only from the init namespace will show
> > up as
> > unlabeled in the child namespace until they are assigned the
> > namespaced
> > attributes.??This for example breaks running the selinux-testsuite
> > with
> > this patch applied (unless perhaps you run restorecon -R / after
> > unsharing); otherwise just trying to invoke /usr/bin/runcon will
> > fail
> > since it is unlabeled in the child.??It seems like we should
> > provide
> > some form of inheritance from the parent when there is no xattr for
> > the
> > namespace itself.
>
> I was assuming that practical use of this would involve doing a
> filesystem?
> relabel under the newly loaded policy, on first instantiation at
> least.
I think that would be problematic, e.g. if you want to share /usr read-
only to all of the containers or similar, then they cannot relabel it
themselves and even if you provided a way to set the xattrs from the
init namespace, in the case where you are using the same or very
similar policies, it seems wasteful to set the same xattr values for N
xattr names for N containers. So I think inheritance support will be
necessary. This will be easier if we make the xattr names themselves
hierarchical (e.g. if vm8 writes vm1 to /sys/fs/selinux/unshare, then
the child xattr name would be security.selinux.ns.vm8.vm1, and we would
inherit from either security.selinux.ns.vm8 or security.selinux if
security.selinux.ns.vm8.vm1 is not set.)
>
> We could try adding an selinuxfs node to specify default handling of?
> unlabeled files in a child namespace, and write to that after
> mounting?
> selinuxfs in that namespace.
>
> e.g. echo inherit > /sys/fs/selinux/parent_ns_labels
>
> or something.
>
>
> >
> > Another potential concern is that files created in a non-init
> > namespace
> > are left completely unlabeled in the init namespace (or in any
> > parent).
> > ????As long as access to unlabeled is tightly controlled, this
> > might
> > not be a problem, but I'm not sure that's guaranteed by the
> > refpolicy
> > or Fedora/RHEL policies.??We might want to initialize an xattr at
> > every
> > level of the namespace hierarchy when a new file is created based
> > on
> > the process and parent directory labels and policy at that level.?
> > Otherwise, we lose all provenance information for the file outside
> > of
> > the namespace.?
>
> Ok.
>
>
> > For example, suppose I want to leak information out of
> > my category set; I unshare and create files with the information,
> > and
> > they appear in the init namespace with no categories.
>
> Nice :)
>
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^ permalink raw reply [flat|nested] 11+ messages in thread
* [RFC v0.1][PATCH] selinuxns: extend namespace support to security.selinux xattrs
2017-10-31 13:00 ` Stephen Smalley
@ 2017-10-31 14:04 ` Stephen Smalley
2017-11-01 6:40 ` James Morris
2017-11-13 6:45 ` James Morris
0 siblings, 2 replies; 11+ messages in thread
From: Stephen Smalley @ 2017-10-31 14:04 UTC (permalink / raw)
To: linux-security-module
On Tue, 2017-10-31 at 09:00 -0400, Stephen Smalley wrote:
> On Tue, 2017-10-31 at 14:11 +1100, James Morris wrote:
> > On Mon, 30 Oct 2017, Stephen Smalley wrote:
> >
> > > Thanks, interesting approach. One drawback is that it doesn't
> > > presently
> > > support any form of inheritance of labels from the parent
> > > namespace, so
> > > files that are shared read-only from the init namespace will show
> > > up as
> > > unlabeled in the child namespace until they are assigned the
> > > namespaced
> > > attributes.??This for example breaks running the selinux-
> > > testsuite
> > > with
> > > this patch applied (unless perhaps you run restorecon -R / after
> > > unsharing); otherwise just trying to invoke /usr/bin/runcon will
> > > fail
> > > since it is unlabeled in the child.??It seems like we should
> > > provide
> > > some form of inheritance from the parent when there is no xattr
> > > for
> > > the
> > > namespace itself.
> >
> > I was assuming that practical use of this would involve doing a
> > filesystem?
> > relabel under the newly loaded policy, on first instantiation at
> > least.
>
> I think that would be problematic, e.g. if you want to share /usr
> read-
> only to all of the containers or similar, then they cannot relabel it
> themselves and even if you provided a way to set the xattrs from the
> init namespace, in the case where you are using the same or very
> similar policies, it seems wasteful to set the same xattr values for
> N
> xattr names for N containers.??So I think inheritance support will be
> necessary.??This will be easier if we make the xattr names themselves
> hierarchical (e.g. if vm8 writes vm1 to /sys/fs/selinux/unshare, then
> the child xattr name would be security.selinux.ns.vm8.vm1, and we
> would
> inherit from either security.selinux.ns.vm8 or security.selinux if
> security.selinux.ns.vm8.vm1 is not set.)
This btw would be a bit cleaner if we dropped the .ns. portion of the
name, such that we would have:
security.selinux # xattr name in the init namespace
security.selinux.vmN # xattr name in the vmN namespace
security.selinux.vmN.vmM # xattr name in the vmN.vmM namespace
...
>
> >
> > We could try adding an selinuxfs node to specify default handling
> > of?
> > unlabeled files in a child namespace, and write to that after
> > mounting?
> > selinuxfs in that namespace.
> >
> > e.g. echo inherit > /sys/fs/selinux/parent_ns_labels
> >
> > or something.
> >
> >
> > >
> > > Another potential concern is that files created in a non-init
> > > namespace
> > > are left completely unlabeled in the init namespace (or in any
> > > parent).
> > > ????As long as access to unlabeled is tightly controlled, this
> > > might
> > > not be a problem, but I'm not sure that's guaranteed by the
> > > refpolicy
> > > or Fedora/RHEL policies.??We might want to initialize an xattr at
> > > every
> > > level of the namespace hierarchy when a new file is created based
> > > on
> > > the process and parent directory labels and policy at that
> > > level.?
> > > Otherwise, we lose all provenance information for the file
> > > outside
> > > of
> > > the namespace.?
> >
> > Ok.
> >
> >
> > > For example, suppose I want to leak information out of
> > > my category set; I unshare and create files with the information,
> > > and
> > > they appear in the init namespace with no categories.
> >
> > Nice :)
> >
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^ permalink raw reply [flat|nested] 11+ messages in thread
* [RFC v0.1][PATCH] selinuxns: extend namespace support to security.selinux xattrs
2017-10-31 14:04 ` Stephen Smalley
@ 2017-11-01 6:40 ` James Morris
2017-11-01 15:22 ` Stephen Smalley
2017-11-13 6:45 ` James Morris
1 sibling, 1 reply; 11+ messages in thread
From: James Morris @ 2017-11-01 6:40 UTC (permalink / raw)
To: linux-security-module
On Tue, 31 Oct 2017, Stephen Smalley wrote:
> This btw would be a bit cleaner if we dropped the .ns. portion of the
> name, such that we would have:
> security.selinux # xattr name in the init namespace
> security.selinux.vmN # xattr name in the vmN namespace
> security.selinux.vmN.vmM # xattr name in the vmN.vmM namespace
I used 'ns' to diffetentiate against other potential extensions of the
xattr name. If that's not a concern, then yes it will be cleaner.
Do we limit the number of nestings?
--
James Morris
<james.l.morris@oracle.com>
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^ permalink raw reply [flat|nested] 11+ messages in thread
* [RFC v0.1][PATCH] selinuxns: extend namespace support to security.selinux xattrs
2017-11-01 6:40 ` James Morris
@ 2017-11-01 15:22 ` Stephen Smalley
0 siblings, 0 replies; 11+ messages in thread
From: Stephen Smalley @ 2017-11-01 15:22 UTC (permalink / raw)
To: linux-security-module
On Wed, 2017-11-01 at 17:40 +1100, James Morris wrote:
> On Tue, 31 Oct 2017, Stephen Smalley wrote:
>
> > This btw would be a bit cleaner if we dropped the .ns. portion of
> > the
> > name, such that we would have:
> > security.selinux # xattr name in the init namespace
> > security.selinux.vmN # xattr name in the vmN namespace
> > security.selinux.vmN.vmM # xattr name in the vmN.vmM namespace
>
> I used 'ns' to diffetentiate against other potential extensions of
> the?
> xattr name.??If that's not a concern, then yes it will be cleaner.
>
> Do we limit the number of nestings?
Not in the current code, but I think we will need to do so. That's
mentioned in the list of known issues in the next-to-last commit:
????* There is no way currently to restrict or bound nesting of
????namespaces; if you allow it to a domain in the init namespace,
????then that domain can in turn unshare to arbitrary depths and can
????grant the same to any domain in its own policy.??Related to this
????is the fact that there is no way to control resource usage due to
????selinux namespaces and they can be substantial (per-namespace
????policydb, sidtab, AVC, etc).
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^ permalink raw reply [flat|nested] 11+ messages in thread
* [RFC v0.1][PATCH] selinuxns: extend namespace support to security.selinux xattrs
2017-10-31 14:04 ` Stephen Smalley
2017-11-01 6:40 ` James Morris
@ 2017-11-13 6:45 ` James Morris
2017-11-13 14:18 ` Stephen Smalley
1 sibling, 1 reply; 11+ messages in thread
From: James Morris @ 2017-11-13 6:45 UTC (permalink / raw)
To: linux-security-module
On Tue, 31 Oct 2017, Stephen Smalley wrote:
> This btw would be a bit cleaner if we dropped the .ns. portion of the
> name, such that we would have:
> security.selinux # xattr name in the init namespace
> security.selinux.vmN # xattr name in the vmN namespace
> security.selinux.vmN.vmM # xattr name in the vmN.vmM namespace
Ok, just to clarify, the namespace name in the last example is "vmN.vmM",
not "vmM" ?
i.e. the namespaces are always hierarchical, and the security labels are
identified by that hierarchy. If you enter vmM from the init namespace,
for example, the security labels for it are distinct from the labels under
vmN. On disk, you would have both:
security.selinux.vmM
security.selinux.vmN.vmM
which are independent.
Each of these instances would potentially inherit different labels, and
have different provenance characteristics, so this seems necessary in any
case.
--
James Morris
<james.l.morris@oracle.com>
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^ permalink raw reply [flat|nested] 11+ messages in thread
* [RFC v0.1][PATCH] selinuxns: extend namespace support to security.selinux xattrs
2017-11-13 6:45 ` James Morris
@ 2017-11-13 14:18 ` Stephen Smalley
2017-11-15 7:48 ` James Morris
0 siblings, 1 reply; 11+ messages in thread
From: Stephen Smalley @ 2017-11-13 14:18 UTC (permalink / raw)
To: linux-security-module
On Mon, 2017-11-13 at 17:45 +1100, James Morris wrote:
> On Tue, 31 Oct 2017, Stephen Smalley wrote:
>
> > This btw would be a bit cleaner if we dropped the .ns. portion of
> > the
> > name, such that we would have:
> > security.selinux # xattr name in the init namespace
> > security.selinux.vmN # xattr name in the vmN namespace
> > security.selinux.vmN.vmM # xattr name in the vmN.vmM namespace
>
> Ok, just to clarify, the namespace name in the last example is
> "vmN.vmM",?
> not "vmM" ?
>
> i.e. the namespaces are always hierarchical, and the security labels
> are?
> identified by that hierarchy.??If you enter vmM from the init
> namespace,?
> for example, the security labels for it are distinct from the labels
> under?
> vmN.??On disk, you would have both:
>
> security.selinux.vmM
> security.selinux.vmN.vmM
>
> which are independent.
>
> Each of these instances would potentially inherit different labels,
> and?
> have different provenance characteristics, so this seems necessary in
> any?
> case.
Yes, at least with respect to the absolute namespace name maintained
within the kernel and used for xattr names. Not clear what should
happen with respect to the names written to or read from
/sys/fs/selinux/unshare; conceptually it seems cleaner if those are
relative to the namespace of the caller, such that if a process that is
already in "vmN" writes "vmM" to /sys/fs/selinux/unshare, then it ends
up in "vmN.vmM" automatically. But if we applied the same principle to
reading, then a subsequent read from /sys/fs/selinux/unshare would give
back the empty string since the process is already in that namespace.
Was also wondering if the name read for the init namespace ought to
just be the empty string instead of the magic "init" value to make it
consistent with the fact that there is no xattr suffix.
Then there is the question of what to do upon a collision, e.g. if a
second process in "vmN" writes "vmM" to /sys/fs/selinux/unshare. We
could either fail with EEXIST and require the caller to use a unique
name relative to its current namespace or use this as a way to enter an
already existing namespace ala setns(2) for other namespaces, i.e. look
up the namespace named "vmN.vmM" and switch to it.
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^ permalink raw reply [flat|nested] 11+ messages in thread
* [RFC v0.1][PATCH] selinuxns: extend namespace support to security.selinux xattrs
2017-11-13 14:18 ` Stephen Smalley
@ 2017-11-15 7:48 ` James Morris
0 siblings, 0 replies; 11+ messages in thread
From: James Morris @ 2017-11-15 7:48 UTC (permalink / raw)
To: linux-security-module
On Mon, 13 Nov 2017, Stephen Smalley wrote:
> Was also wondering if the name read for the init namespace ought to
> just be the empty string instead of the magic "init" value to make it
> consistent with the fact that there is no xattr suffix.
Makes sense. It could also be "security.selinux", and always exactly
match the xattr name.
--
James Morris
<james.l.morris@oracle.com>
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^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2017-11-15 7:48 UTC | newest]
Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
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2017-10-30 10:04 [RFC v0.1][PATCH] selinuxns: extend namespace support to security.selinux xattrs James Morris
2017-10-30 15:55 ` Casey Schaufler
2017-10-30 19:16 ` Stephen Smalley
2017-10-31 3:11 ` James Morris
2017-10-31 13:00 ` Stephen Smalley
2017-10-31 14:04 ` Stephen Smalley
2017-11-01 6:40 ` James Morris
2017-11-01 15:22 ` Stephen Smalley
2017-11-13 6:45 ` James Morris
2017-11-13 14:18 ` Stephen Smalley
2017-11-15 7:48 ` James Morris
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