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selinux: only invoke capabilities and selinux for CAP_MAC_ADMIN checks

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SELinux uses CAP_MAC_ADMIN to control the ability to get or set a raw,
uninterpreted security context unknown to the currently loaded security
policy. When performing these checks, we only want to perform a base
capabilities check and a SELinux permission check.  If any other
modules that implement a capable hook are stacked with SELinux, we do
not want to require them to also have to authorize CAP_MAC_ADMIN,
since it may have different implications for their security model.
Rework the CAP_MAC_ADMIN checks within SELinux to only invoke the
capabilities module and the SELinux permission checking.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Stephen Smalley 2017-04-20 11:31:30 -04:00 committed by Paul Moore
parent 46be14d2b6
commit db59000ab7
1 changed files with 15 additions and 8 deletions
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23
security/selinux/hooks.c
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@ -3107,6 +3107,18 @@ static int selinux_inode_setotherxattr(struct dentry *dentry, const char *name)
return dentry_has_perm(cred, dentry, FILE__SETATTR);
}
static bool has_cap_mac_admin(bool audit)
{
const struct cred *cred = current_cred();
int cap_audit = audit ? SECURITY_CAP_AUDIT : SECURITY_CAP_NOAUDIT;
if (cap_capable(cred, &init_user_ns, CAP_MAC_ADMIN, cap_audit))
return false;
if (cred_has_capability(cred, CAP_MAC_ADMIN, cap_audit, true))
return false;
return true;
}
static int selinux_inode_setxattr(struct dentry *dentry, const char *name,
const void *value, size_t size, int flags)
{
@ -3138,7 +3150,7 @@ static int selinux_inode_setxattr(struct dentry *dentry, const char *name,
rc = security_context_to_sid(value, size, &newsid, GFP_KERNEL);
if (rc == -EINVAL) {
if (!capable(CAP_MAC_ADMIN)) {
if (!has_cap_mac_admin(true)) {
struct audit_buffer *ab;
size_t audit_size;
const char *str;
@ -3264,13 +3276,8 @@ static int selinux_inode_getsecurity(struct inode *inode, const char *name, void
* and lack of permission just means that we fall back to the
* in-core context value, not a denial.
*/
error = cap_capable(current_cred(), &init_user_ns, CAP_MAC_ADMIN,
SECURITY_CAP_NOAUDIT);
if (!error)
error = cred_has_capability(current_cred(), CAP_MAC_ADMIN,
SECURITY_CAP_NOAUDIT, true);
isec = inode_security(inode);
if (!error)
if (has_cap_mac_admin(false))
error = security_sid_to_context_force(isec->sid, &context,
&size);
else
@ -5919,7 +5926,7 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
}
error = security_context_to_sid(value, size, &sid, GFP_KERNEL);
if (error == -EINVAL && !strcmp(name, "fscreate")) {
if (!capable(CAP_MAC_ADMIN)) {
if (!has_cap_mac_admin(true)) {
struct audit_buffer *ab;
size_t audit_size;