Ubuntu Manpage: selabel_x - userspace SELinux labeling interface and configuration file format for the X Window System

Provided by: selinux-utils_3.7-3ubuntu3_amd64

NAME

       selabel_x  -  userspace  SELinux labeling interface and configuration file format for the X Window System
       contexts backend. This backend is also used to  determine  the  default  context  for  labeling  remotely
       connected X clients

SYNOPSIS

       #include <selinux/label.h>

       int selabel_lookup(struct selabel_handle *hnd,
                          char **context,
                          const char *object_name, int object_type);

       int selabel_lookup_raw(struct selabel_handle *hnd,
                          char **context,
                          const char *object_name, int object_type);

DESCRIPTION

The X contexts backend maps from X Window System object names into security contexts. It is used to find
the appropriate context for X Window System objects whose significance and/or usage semantics are
determined primarily by name. The returned context must be freed using freecon(3).
selabel_lookup(3) describes the function with its return and error codes.

This backend is also used to determine the default context for labeling remotely connected X clients.

The object_type argument should be set to one of the following values:

SELABEL_X_PROP
The object_name argument specifies the name of a window property, such as "WM_NAME".

SELABEL_X_SELN
The object_name argument specifies the name of a selection, such as "PRIMARY".

SELABEL_X_EXT
The object_name argument specifies the name of a protocol extension, such as "RENDER".

SELABEL_X_EVENT
The object_name argument specifies the name of an event type, such as "X11:ButtonPress".

SELABEL_X_CLIENT
The object_name argument is ignored, however it should be set to either * (an asterisk or
'wildcard' that will select the default entry) or a specific entry such as "remote" in the
X contexts file as shown in the EXAMPLE section. The default context for labeling remote X
clients is then returned.

SELABEL_X_POLYPROP
Like SELABEL_X_PROP, but checks if the property was marked as being polyinstantiated. See
NOTES below.

SELABEL_X_POLYSELN
Like SELABEL_X_SELN, but checks if the selection was marked as being polyinstantiated. See
NOTES below.

Any messages generated by selabel_lookup(3) are sent to stderr by default, although this can be changed
by selinux_set_callback(3).

selabel_lookup_raw behaves identically to selabel_lookup but does not perform context translation.

The FILES section details the configuration files used to determine the X object context.

OPTIONS

       In  addition  to  the  global options described in selabel_open(3), this backend recognizes the following
       options:

              SELABEL_OPT_PATH
                     A non-null value for this option specifies a path to a file that will be opened in lieu  of
                     the standard X contexts file (see the FILES section for details).

FILES

       The X context file used to retrieve a default context depends on the SELABEL_OPT_PATH parameter passed to
       selabel_open(3).  If  NULL,  then the SELABEL_OPT_PATH value will default to the active policy X contexts
       location  (as  returned  by  selinux_x_context_path(3)),  otherwise  the  actual  SELABEL_OPT_PATH  value
       specified is used.

       The default X object contexts file is:
              /etc/selinux/{SELINUXTYPE}/contexts/x_contexts

       Where {SELINUXTYPE} is the entry from the selinux configuration file config (see selinux_config(5)).

       The  entries  within  the  X  contexts  file  are  shown in the Object Name String Values and FILE FORMAT
       sections.

Object Name String Values

       The string name assigned to each object_type argument that can be present in the X contexts file are:
                                       ┌────────────────────┬────────────────┐
                                       │ object_type        │ Text Name      │
                                       ├────────────────────┼────────────────┤
                                       │ SELABEL_X_PROP     │ property       │
                                       ├────────────────────┼────────────────┤
                                       │ SELABEL_X_SELN     │ selection      │
                                       ├────────────────────┼────────────────┤
                                       │ SELABEL_X_EXT      │ extension      │
                                       ├────────────────────┼────────────────┤
                                       │ SELABEL_X_EVENT    │ event          │
                                       ├────────────────────┼────────────────┤
                                       │ SELABEL_X_CLIENT   │ client         │
                                       ├────────────────────┼────────────────┤
                                       │ SELABEL_X_POLYPROP │ poly_property  │
                                       ├────────────────────┼────────────────┤
                                       │ SELABEL_X_POLYSELN │ poly_selection │
                                       └────────────────────┴────────────────┘

FILE FORMAT

       Each line within the X contexts file is as follows:
              object_type object_name context

       Where:
              object_type
                     This is the string representation of the object type shown in the Object Name String Values
                     section.  There can be multiple lines with the same object_type string  that  will  form  a
                     block of entries (each with a different object_name entry).
              object_name
                     These  are  the object names of the specific X-server resource such as PRIMARY, CUT_BUFFER0
                     etc. They are generally defined in the X-server source code (protocol.txt and  BuiltInAtoms
                     in  the  dix  directory  of the xorg-server source package).  The entry can contain '*' for
                     wildcard matching or '?' for substitution.  Note that if the '*' is  used,  then  be  aware
                     that  the order of entries in the file is important. The '*' on its own is used to ensure a
                     default fallback context is assigned and should be the last entry in the object_type block.
              context
                     The security context that will be applied to the object.

       Example 1:

       # object_type  object_name  context
       selection      PRIMARY      system_u:object_r:clipboard_xselection_t:s0
       selection      *            system_u:object_r:xselection_t:s0

       Example 2 - This example shows how a client entry can be configured to ensure an entry is always found:

       # object_type  object_name  context
       client         *            system_u:object_r:remote_t:s0

NOTES

       1.  Properties and selections are marked as either polyinstantiated or not. For  these  name  types,  the
           "POLY"  option  searches  only  the  names  marked  as being polyinstantiated, while the other option
           searches only the names marked as not being polyinstantiated. Users of  the  interface  should  check
           both mappings, optionally taking action based on the result (e.g. polyinstantiating the object).

       2.  If  contexts  are  to  be  validated,  then the global option SELABEL_OPT_VALIDATE must be set before
           calling selabel_open(3). If this is not set, then it  is  possible  for  an  invalid  context  to  be
           returned.