On 10/27/2015 04:48 PM, Andrew Perepechko wrote:
Make validatetrans decisions available through selinuxfs.
"/validatetrans" is added to selinuxfs for this purpose.
This functionality is needed by file system servers
implemented in userspace or kernelspace without the VFS
layer.
Writing "$oldcontext $newcontext $tclass $taskcontext"
to /validatetrans is expected to return 0 if the transition
is allowed and -EPERM otherwise.
Signed-off-by: Andrew Perepechko <anserper@xxxxx>
CC: andrew.perepechko@xxxxxxxxxxx
---
security/selinux/include/classmap.h | 2 +-
security/selinux/include/security.h | 3 +
security/selinux/selinuxfs.c | 79 +++++++++++++++++++++++++++++++++++
security/selinux/ss/services.c | 41 ++++++++++++++----
4 files changed, 114 insertions(+), 11 deletions(-)
diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index 5a4eef5..ef83c4b 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -21,7 +21,7 @@ struct security_class_mapping secclass_map[] = {
{ "compute_av", "compute_create", "compute_member",
"check_context", "load_policy", "compute_relabel",
"compute_user", "setenforce", "setbool", "setsecparam",
- "setcheckreqprot", "read_policy", NULL } },
+ "setcheckreqprot", "read_policy", "validate_trans", NULL } },
{ "process",
{ "fork", "transition", "sigchld", "sigkill",
"sigstop", "signull", "signal", "ptrace", "getsched", "setsched",
diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index 223e9fd..38feb55 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -187,6 +187,9 @@ int security_node_sid(u16 domain, void *addr, u32 addrlen,
int security_validate_transition(u32 oldsid, u32 newsid, u32 tasksid,
u16 tclass);
+int security_validate_transition_user(u32 oldsid, u32 newsid, u32 tasksid,
+ u16 tclass);
+
int security_bounded_transition(u32 oldsid, u32 newsid);
int security_sid_mls_copy(u32 sid, u32 mls_sid, u32 *new_sid);
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index c02da25..e460b4e 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -116,6 +116,7 @@ enum sel_inos {
SEL_DENY_UNKNOWN, /* export unknown deny handling to userspace */
SEL_STATUS, /* export current status using mmap() */
SEL_POLICY, /* allow userspace to read the in kernel policy */
+ SEL_VALIDATE_TRANS, /* compute validatetrans decision */
SEL_INO_NEXT, /* The next inode number to use */
};
@@ -653,6 +654,83 @@ static const struct file_operations sel_checkreqprot_ops = {
.llseek = generic_file_llseek,
};
+static ssize_t sel_write_validatetrans(struct file *file,
+ const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ char *oldcon = NULL, *newcon = NULL, *taskcon = NULL;
+ char *req = NULL;
+ u32 osid, nsid, tsid;
+ u16 tclass;
+ int rc;
+
+ rc = task_has_security(current, SECURITY__VALIDATE_TRANS);
+ if (rc)
+ goto out;
+
+ rc = -ENOMEM;
+ if (count >= PAGE_SIZE)
+ goto out;
+
+ /* No partial writes. */
+ rc = -EINVAL;
+ if (*ppos != 0)
+ goto out;
+
+ rc = -ENOMEM;
+ req = kzalloc(count + 1, GFP_KERNEL);
+ if (!req)
+ goto out;
+
+ rc = -EFAULT;
+ if (copy_from_user(req, buf, count))
+ goto out;
+
+ rc = -ENOMEM;
+ oldcon = kzalloc(count + 1, GFP_KERNEL);
+ if (!oldcon)
+ goto out;
+
+ newcon = kzalloc(count + 1, GFP_KERNEL);
+ if (!newcon)
+ goto out;
+
+ taskcon = kzalloc(count + 1, GFP_KERNEL);
+ if (!taskcon)
+ goto out;
+
+ rc = -EINVAL;
+ if (sscanf(req, "%s %s %hu %s", oldcon, newcon, &tclass, taskcon) != 4)
+ goto out;
+
+ rc = security_context_str_to_sid(oldcon, &osid, GFP_KERNEL);
+ if (rc)
+ goto out;
+
+ rc = security_context_str_to_sid(newcon, &nsid, GFP_KERNEL);
+ if (rc)
+ goto out;
+
+ rc = security_context_str_to_sid(taskcon, &tsid, GFP_KERNEL);
+ if (rc)
+ goto out;
+
+ rc = security_validate_transition_user(osid, nsid, tsid, tclass);
+ if (!rc)
+ rc = count;
+out:
+ kfree(req);
+ kfree(oldcon);
+ kfree(newcon);
+ kfree(taskcon);
+ return rc;
+}
+
+static const struct file_operations sel_validatetrans_ops = {
+ .write = sel_write_validatetrans,
+ .llseek = generic_file_llseek,
+};
+
/*
* Remaining nodes use transaction based IO methods like nfsd/nfsctl.c
*/
@@ -1759,6 +1836,8 @@ static int sel_fill_super(struct super_block *sb, void *data, int silent)
[SEL_DENY_UNKNOWN] = {"deny_unknown", &sel_handle_unknown_ops, S_IRUGO},
[SEL_STATUS] = {"status", &sel_handle_status_ops, S_IRUGO},
[SEL_POLICY] = {"policy", &sel_policy_ops, S_IRUGO},
+ [SEL_VALIDATE_TRANS] = {"validatetrans", &sel_validatetrans_ops,
+ S_IWUSR},
Why only owner-writable? The other policy query operations are S_IWUGO,
and thus only restricted by SELinux policy, so they can be used by
processes running under a variety of UIDs.
/* last one */ {""}
};
ret = simple_fill_super(sb, SELINUX_MAGIC, selinux_files);
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index ebb5eb3..527c90e 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -750,7 +750,7 @@ static void context_struct_compute_av(struct context *scontext,
tclass, avd);
}
-static int security_validtrans_handle_fail(struct context *ocontext,
+static void security_validtrans_audit_fail(struct context *ocontext,
struct context *ncontext,
struct context *tcontext,
u16 tclass)
@@ -772,14 +772,10 @@ out:
kfree(o);
kfree(n);
kfree(t);
-
- if (!selinux_enforcing)
- return 0;
- return -EPERM;
}
-int security_validate_transition(u32 oldsid, u32 newsid, u32 tasksid,
- u16 orig_tclass)
+static int security_compute_validatetrans(u32 oldsid, u32 newsid, u32 tasksid,
+ u16 orig_tclass, bool user)
{
struct context *ocontext;
struct context *ncontext;
@@ -794,7 +790,10 @@ int security_validate_transition(u32 oldsid, u32 newsid, u32 tasksid,
read_lock(&policy_rwlock);
- tclass = unmap_class(orig_tclass);
+ if (!user)
+ tclass = unmap_class(orig_tclass);
+ else
+ tclass = orig_tclass;
if (!tclass || tclass > policydb.p_classes.nprim) {
printk(KERN_ERR "SELinux: %s: unrecognized class %d\n",
I think we need to get rid of this printk, probably in general, but at
least for the user case where class could be anything without a kernel
bug. I think we already dropped the corresponding printk from
compute_av and compute_sid long ago.
@@ -832,8 +831,16 @@ int security_validate_transition(u32 oldsid, u32 newsid, u32 tasksid,
while (constraint) {
if (!constraint_expr_eval(ocontext, ncontext, tcontext,
constraint->expr)) {
- rc = security_validtrans_handle_fail(ocontext, ncontext,
- tcontext, tclass);
+ if (!user)
+ security_validtrans_audit_fail(ocontext,
+ ncontext,
+ tcontext,
+ tclass);
+ if (!selinux_enforcing)
+ rc = 0;
+ else
+ rc = -EPERM;
Wondering if you were on the right path originally here, i.e. permit
different enforcing modes for kernel vs userspace, since we do support
that for the userspace AVC via AVC_OPT_SETENFORCE option to avc_open(3).
In that case, you don't actually need to modify
security_validtrans_handle_fail; you can just do:
if (user)
rc = -EPERM;
else
rc = security_validtrans_handle_fail(ocontext, ncontext,
tcontext, tclass);
+
goto out;
}
constraint = constraint->next;
@@ -844,6 +851,20 @@ out:
return rc;
}
+int security_validate_transition_user(u32 oldsid, u32 newsid, u32 tasksid,
+ u16 tclass)
+{
+ return security_compute_validatetrans(oldsid, newsid, tasksid,
+ tclass, true);
+}
+
+int security_validate_transition(u32 oldsid, u32 newsid, u32 tasksid,
+ u16 orig_tclass)
+{
+ return security_compute_validatetrans(oldsid, newsid, tasksid,
+ orig_tclass, false);
+}
+
/*
* security_bounded_transition - check whether the given
* transition is directed to bounded, or not.
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