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><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="SEPGSQL"
>F.33. sepgsql</A
></H1
><P
> <TT
CLASS="FILENAME"
>sepgsql</TT
> is a loadable module that supports label-based
mandatory access control (MAC) based on <SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
> security
policy.
</P
><DIV
CLASS="WARNING"
><P
></P
><TABLE
CLASS="WARNING"
BORDER="1"
WIDTH="100%"
><TR
><TD
ALIGN="CENTER"
><B
>Warning</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
><P
> The current implementation has significant limitations, and does not
enforce mandatory access control for all actions. See
<A
HREF="sepgsql.html#SEPGSQL-LIMITATIONS"
>Section F.33.7</A
>.
</P
></TD
></TR
></TABLE
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SEPGSQL-OVERVIEW"
>F.33.1. Overview</A
></H2
><P
> This module integrates with <SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
> to provide an
additional layer of security checking above and beyond what is normally
provided by <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>. From the perspective of
<SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
>, this module allows
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> to function as a user-space object
manager. Each table or function access initiated by a DML query will be
checked against the system security policy. This check is in addition to
the usual SQL permissions checking performed by
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>.
</P
><P
> <SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
> access control decisions are made using
security labels, which are represented by strings such as
<TT
CLASS="LITERAL"
>system_u:object_r:sepgsql_table_t:s0</TT
>. Each access control
decision involves two labels: the label of the subject attempting to
perform the action, and the label of the object on which the operation is
to be performed. Since these labels can be applied to any sort of object,
access control decisions for objects stored within the database can be
(and, with this module, are) subjected to the same general criteria used
for objects of any other type, such as files. This design is intended to
allow a centralized security policy to protect information assets
independent of the particulars of how those assets are stored.
</P
><P
> The <A
HREF="sql-security-label.html"
>SECURITY LABEL</A
> statement allows assignment of
a security label to a database object.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SEPGSQL-INSTALLATION"
>F.33.2. Installation</A
></H2
><P
> <TT
CLASS="FILENAME"
>sepgsql</TT
> can only be used on <SPAN
CLASS="PRODUCTNAME"
>Linux</SPAN
>
2.6.28 or higher with <SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
> enabled.
It is not available on any other platform. You will also need
<SPAN
CLASS="PRODUCTNAME"
>libselinux</SPAN
> 2.1.10 or higher and
<SPAN
CLASS="PRODUCTNAME"
>selinux-policy</SPAN
> 3.9.13 or higher (although some
distributions may backport the necessary rules into older policy
versions).
</P
><P
> The <TT
CLASS="COMMAND"
>sestatus</TT
> command allows you to check the status of
<SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
>. A typical display is:
</P><PRE
CLASS="SCREEN"
>$ sestatus
SELinux status: enabled
SELinuxfs mount: /selinux
Current mode: enforcing
Mode from config file: enforcing
Policy version: 24
Policy from config file: targeted</PRE
><P>
If <SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
> is disabled or not installed, you must set
that product up first before installing this module.
</P
><P
> To build this module, include the option <TT
CLASS="LITERAL"
>--with-selinux</TT
> in
your PostgreSQL <TT
CLASS="LITERAL"
>configure</TT
> command. Be sure that the
<TT
CLASS="FILENAME"
>libselinux-devel</TT
> RPM is installed at build time.
</P
><P
> To use this module, you must include <TT
CLASS="LITERAL"
>sepgsql</TT
>
in the <A
HREF="runtime-config-resource.html#GUC-SHARED-PRELOAD-LIBRARIES"
>shared_preload_libraries</A
> parameter in
<TT
CLASS="FILENAME"
>postgresql.conf</TT
>. The module will not function correctly
if loaded in any other manner. Once the module is loaded, you
should execute <TT
CLASS="FILENAME"
>sepgsql.sql</TT
> in each database.
This will install functions needed for security label management, and
assign initial security labels.
</P
><P
> Here is an example showing how to initialize a fresh database cluster
with <TT
CLASS="FILENAME"
>sepgsql</TT
> functions and security labels installed.
Adjust the paths shown as appropriate for your installation:
</P
><PRE
CLASS="SCREEN"
>$ export PGDATA=/path/to/data/directory
$ initdb
$ vi $PGDATA/postgresql.conf
change
#shared_preload_libraries = '' # (change requires restart)
to
shared_preload_libraries = 'sepgsql' # (change requires restart)
$ for DBNAME in template0 template1 postgres; do
postgres --single -F -c exit_on_error=true $DBNAME \
</usr/local/pgsql/share/contrib/sepgsql.sql >/dev/null
done</PRE
><P
> Please note that you may see some or all of the following notifications
depending on the particular versions you have of
<SPAN
CLASS="PRODUCTNAME"
>libselinux</SPAN
> and <SPAN
CLASS="PRODUCTNAME"
>selinux-policy</SPAN
>:
</P><PRE
CLASS="SCREEN"
>/etc/selinux/targeted/contexts/sepgsql_contexts: line 33 has invalid object type db_blobs
/etc/selinux/targeted/contexts/sepgsql_contexts: line 36 has invalid object type db_language
/etc/selinux/targeted/contexts/sepgsql_contexts: line 37 has invalid object type db_language
/etc/selinux/targeted/contexts/sepgsql_contexts: line 38 has invalid object type db_language
/etc/selinux/targeted/contexts/sepgsql_contexts: line 39 has invalid object type db_language
/etc/selinux/targeted/contexts/sepgsql_contexts: line 40 has invalid object type db_language</PRE
><P>
These messages are harmless and should be ignored.
</P
><P
> If the installation process completes without error, you can now start the
server normally.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SEPGSQL-REGRESSION"
>F.33.3. Regression Tests</A
></H2
><P
> Due to the nature of <SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
>, running the
regression tests for <TT
CLASS="FILENAME"
>sepgsql</TT
> requires several extra
configuration steps, some of which must be done as root.
The regression tests will not be run by an ordinary
<TT
CLASS="LITERAL"
>make check</TT
> or <TT
CLASS="LITERAL"
>make installcheck</TT
> command; you must
set up the configuration and then invoke the test script manually.
The tests must be run in the <TT
CLASS="FILENAME"
>contrib/sepgsql</TT
> directory
of a configured PostgreSQL build tree. Although they require a build tree,
the tests are designed to be executed against an installed server,
that is they are comparable to <TT
CLASS="LITERAL"
>make installcheck</TT
> not
<TT
CLASS="LITERAL"
>make check</TT
>.
</P
><P
> First, set up <TT
CLASS="FILENAME"
>sepgsql</TT
> in a working database
according to the instructions in <A
HREF="sepgsql.html#SEPGSQL-INSTALLATION"
>Section F.33.2</A
>.
Note that the current operating system user must be able to connect to the
database as superuser without password authentication.
</P
><P
> Second, build and install the policy package for the regression test.
The <TT
CLASS="FILENAME"
>sepgsql-regtest</TT
> policy is a special purpose policy package
which provides a set of rules to be allowed during the regression tests.
It should be built from the policy source file
<TT
CLASS="FILENAME"
>sepgsql-regtest.te</TT
>, which is done using
<TT
CLASS="COMMAND"
>make</TT
> with a Makefile supplied by SELinux.
You will need to locate the appropriate
Makefile on your system; the path shown below is only an example.
Once built, install this policy package using the
<TT
CLASS="COMMAND"
>semodule</TT
> command, which loads supplied policy packages
into the kernel. If the package is correctly installed,
<TT
CLASS="LITERAL"
><TT
CLASS="COMMAND"
>semodule</TT
> -l</TT
> should list <TT
CLASS="LITERAL"
>sepgsql-regtest</TT
> as an
available policy package:
</P
><PRE
CLASS="SCREEN"
>$ cd .../contrib/sepgsql
$ make -f /usr/share/selinux/devel/Makefile
$ sudo semodule -u sepgsql-regtest.pp
$ sudo semodule -l | grep sepgsql
sepgsql-regtest 1.07</PRE
><P
> Third, turn on <TT
CLASS="LITERAL"
>sepgsql_regression_test_mode</TT
>.
For security reasons, the rules in <TT
CLASS="FILENAME"
>sepgsql-regtest</TT
>
are not enabled by default;
the <TT
CLASS="LITERAL"
>sepgsql_regression_test_mode</TT
> parameter enables
the rules needed to launch the regression tests.
It can be turned on using the <TT
CLASS="COMMAND"
>setsebool</TT
> command:
</P
><PRE
CLASS="SCREEN"
>$ sudo setsebool sepgsql_regression_test_mode on
$ getsebool sepgsql_regression_test_mode
sepgsql_regression_test_mode --> on</PRE
><P
> Fourth, verify your shell is operating in the <TT
CLASS="LITERAL"
>unconfined_t</TT
>
domain:
</P
><PRE
CLASS="SCREEN"
>$ id -Z
unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023</PRE
><P
> See <A
HREF="sepgsql.html#SEPGSQL-RESOURCES"
>Section F.33.8</A
> for details on adjusting your
working domain, if necessary.
</P
><P
> Finally, run the regression test script:
</P
><PRE
CLASS="SCREEN"
>$ ./test_sepgsql</PRE
><P
> This script will attempt to verify that you have done all the configuration
steps correctly, and then it will run the regression tests for the
<TT
CLASS="FILENAME"
>sepgsql</TT
> module.
</P
><P
> After completing the tests, it's recommended you disable
the <TT
CLASS="LITERAL"
>sepgsql_regression_test_mode</TT
> parameter:
</P
><PRE
CLASS="SCREEN"
>$ sudo setsebool sepgsql_regression_test_mode off</PRE
><P
> You might prefer to remove the <TT
CLASS="FILENAME"
>sepgsql-regtest</TT
> policy
entirely:
</P
><PRE
CLASS="SCREEN"
>$ sudo semodule -r sepgsql-regtest</PRE
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SEPGSQL-PARAMETERS"
>F.33.4. GUC Parameters</A
></H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><A
NAME="GUC-SEPGSQL-PERMISSIVE"
></A
><TT
CLASS="VARNAME"
>sepgsql.permissive</TT
> (<TT
CLASS="TYPE"
>boolean</TT
>)</DT
><DD
><P
> This parameter enables <TT
CLASS="FILENAME"
>sepgsql</TT
> to function
in permissive mode, regardless of the system setting.
The default is off.
This parameter can only be set in the <TT
CLASS="FILENAME"
>postgresql.conf</TT
>
file or on the server command line.
</P
><P
> When this parameter is on, <TT
CLASS="FILENAME"
>sepgsql</TT
> functions
in permissive mode, even if SELinux in general is working in enforcing
mode. This parameter is primarily useful for testing purposes.
</P
></DD
><DT
><A
NAME="GUC-SEPGSQL-DEBUG-AUDIT"
></A
><TT
CLASS="VARNAME"
>sepgsql.debug_audit</TT
> (<TT
CLASS="TYPE"
>boolean</TT
>)</DT
><DD
><P
> This parameter enables the printing of audit messages regardless of
the system policy settings.
The default is off, which means that messages will be printed according
to the system settings.
</P
><P
> The security policy of <SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
> also has rules to
control whether or not particular accesses are logged.
By default, access violations are logged, but allowed
accesses are not.
</P
><P
> This parameter forces all possible logging to be turned on, regardless
of the system policy.
</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SEPGSQL-FEATURES"
>F.33.5. Features</A
></H2
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN156147"
>F.33.5.1. Controlled Object Classes</A
></H3
><P
> The security model of <SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
> describes all the access
control rules as relationships between a subject entity (typically,
a client of the database) and an object entity (such as a database
object), each of which is
identified by a security label. If access to an unlabeled object is
attempted, the object is treated as if it were assigned the label
<TT
CLASS="LITERAL"
>unlabeled_t</TT
>.
</P
><P
> Currently, <TT
CLASS="FILENAME"
>sepgsql</TT
> allows security labels to be
assigned to schemas, tables, columns, sequences, views, and functions.
When <TT
CLASS="FILENAME"
>sepgsql</TT
> is in use, security labels are
automatically assigned to supported database objects at creation time.
This label is called a default security label, and is decided according
to the system security policy, which takes as input the creator's label,
the label assigned to the new object's parent object and optionally name
of the constructed object.
</P
><P
> A new database object basically inherits the security label of the parent
object, except when the security policy has special rules known as
type-transition rules, in which case a different label may be applied.
For schemas, the parent object is the current database; for tables,
sequences, views, and functions, it is the containing schema; for columns,
it is the containing table.
</P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN156156"
>F.33.5.2. DML Permissions</A
></H3
><P
> For tables, <TT
CLASS="LITERAL"
>db_table:select</TT
>, <TT
CLASS="LITERAL"
>db_table:insert</TT
>,
<TT
CLASS="LITERAL"
>db_table:update</TT
> or <TT
CLASS="LITERAL"
>db_table:delete</TT
> are
checked for all the referenced target tables depending on the kind of
statement; in addition, <TT
CLASS="LITERAL"
>db_table:select</TT
> is also checked for
all the tables that contain columns referenced in the
<TT
CLASS="LITERAL"
>WHERE</TT
> or <TT
CLASS="LITERAL"
>RETURNING</TT
> clause, as a data source
for <TT
CLASS="LITERAL"
>UPDATE</TT
>, and so on.
</P
><P
> Column-level permissions will also be checked for each referenced column.
<TT
CLASS="LITERAL"
>db_column:select</TT
> is checked on not only the columns being
read using <TT
CLASS="LITERAL"
>SELECT</TT
>, but those being referenced in other DML
statements; <TT
CLASS="LITERAL"
>db_column:update</TT
> or <TT
CLASS="LITERAL"
>db_column:insert</TT
>
will also be checked for columns being modified by <TT
CLASS="LITERAL"
>UPDATE</TT
> or
<TT
CLASS="LITERAL"
>INSERT</TT
>.
</P
><P
> For example, consider:
</P><PRE
CLASS="SYNOPSIS"
>UPDATE t1 SET x = 2, y = md5sum(y) WHERE z = 100;</PRE
><P>
Here, <TT
CLASS="LITERAL"
>db_column:update</TT
> will be checked for
<TT
CLASS="LITERAL"
>t1.x</TT
>, since it is being updated,
<TT
CLASS="LITERAL"
>db_column:{select update}</TT
> will be checked for
<TT
CLASS="LITERAL"
>t1.y</TT
>, since it is both updated and referenced, and
<TT
CLASS="LITERAL"
>db_column:select</TT
> will be checked for <TT
CLASS="LITERAL"
>t1.z</TT
>, since
it is only referenced.
<TT
CLASS="LITERAL"
>db_table:{select update}</TT
> will also be checked
at the table level.
</P
><P
> For sequences, <TT
CLASS="LITERAL"
>db_sequence:get_value</TT
> is checked when we
reference a sequence object using <TT
CLASS="LITERAL"
>SELECT</TT
>; however, note that we
do not currently check permissions on execution of corresponding functions
such as <TT
CLASS="LITERAL"
>lastval()</TT
>.
</P
><P
> For views, <TT
CLASS="LITERAL"
>db_view:expand</TT
> will be checked, then any other
required permissions will be checked on the objects being
expanded from the view, individually.
</P
><P
> For functions, <TT
CLASS="LITERAL"
>db_procedure:{execute}</TT
> will be checked when
user tries to execute a function as a part of query, or using fast-path
invocation. If this function is a trusted procedure, it also checks
<TT
CLASS="LITERAL"
>db_procedure:{entrypoint}</TT
> permission to check whether it
can perform as entry point of trusted procedure.
</P
><P
> In order to access any schema object, <TT
CLASS="LITERAL"
>db_schema:search</TT
>
permission is required on the containing schema. When an object is
referenced without schema qualification, schemas on which this
permission is not present will not be searched (just as if the user did
not have <TT
CLASS="LITERAL"
>USAGE</TT
> privilege on the schema). If an explicit schema
qualification is present, an error will occur if the user does not have
the requisite permission on the named schema.
</P
><P
> The client must be allowed to access all referenced tables and
columns, even if they originated from views which were then expanded,
so that we apply consistent access control rules independent of the manner
in which the table contents are referenced.
</P
><P
> The default database privilege system allows database superusers to
modify system catalogs using DML commands, and reference or modify
toast tables. These operations are prohibited when
<TT
CLASS="FILENAME"
>sepgsql</TT
> is enabled.
</P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN156198"
>F.33.5.3. DDL Permissions</A
></H3
><P
> <SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
> defines several permissions to control common
operations for each object type; such as creation, alter, drop and
relabel of security label. In addition, several object types have
special permissions to control their characteristic operations; such as
addition or deletion of name entries within a particular schema.
</P
><P
> Creating a new database object requires <TT
CLASS="LITERAL"
>create</TT
> permission.
<SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
> will grant or deny this permission based on the
client's security label and the proposed security label for the new
object. In some cases, additional privileges are required:
</P
><P
></P
><UL
><LI
><P
> <A
HREF="sql-createdatabase.html"
>CREATE DATABASE</A
> additionally requires
<TT
CLASS="LITERAL"
>getattr</TT
> permission for the source or template database.
</P
></LI
><LI
><P
> Creating a schema object additionally requires <TT
CLASS="LITERAL"
>add_name</TT
>
permission on the parent schema.
</P
></LI
><LI
><P
> Creating a table additionally requires permission to create each
individual table column, just as if each table column were a
separate top-level object.
</P
></LI
><LI
><P
> Creating a function marked as <TT
CLASS="LITERAL"
>LEAKPROOF</TT
> additionally
requires <TT
CLASS="LITERAL"
>install</TT
> permission. (This permission is also
checked when <TT
CLASS="LITERAL"
>LEAKPROOF</TT
> is set for an existing function.)
</P
></LI
></UL
><P
> When <TT
CLASS="LITERAL"
>DROP</TT
> command is executed, <TT
CLASS="LITERAL"
>drop</TT
> will be
checked on the object being removed. Permissions will be also checked for
objects dropped indirectly via <TT
CLASS="LITERAL"
>CASCADE</TT
>. Deletion of objects
contained within a particular schema (tables, views, sequences and
procedures) additionally requires <TT
CLASS="LITERAL"
>remove_name</TT
> on the schema.
</P
><P
> When <TT
CLASS="LITERAL"
>ALTER</TT
> command is executed, <TT
CLASS="LITERAL"
>setattr</TT
> will be
checked on the object being modified for each object types, except for
subsidiary objects such as the indexes or triggers of a table, where
permissions are instead checked on the parent object. In some cases,
additional permissions are required:
</P
><P
></P
><UL
><LI
><P
> Moving an object to a new schema additionally requires
<TT
CLASS="LITERAL"
>remove_name</TT
> permission on the old schema and
<TT
CLASS="LITERAL"
>add_name</TT
> permission on the new one.
</P
></LI
><LI
><P
> Setting the <TT
CLASS="LITERAL"
>LEAKPROOF</TT
> attribute on a function requires
<TT
CLASS="LITERAL"
>install</TT
> permission.
</P
></LI
><LI
><P
> Using <A
HREF="sql-security-label.html"
>SECURITY LABEL</A
> on an object additionally
requires <TT
CLASS="LITERAL"
>relabelfrom</TT
> permission for the object in
conjunction with its old security label and <TT
CLASS="LITERAL"
>relabelto</TT
>
permission for the object in conjunction with its new security label.
(In cases where multiple label providers are installed and the user
tries to set a security label, but it is not managed by
<SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
>, only <TT
CLASS="LITERAL"
>setattr</TT
> should be checked here.
This is currently not done due to implementation restrictions.)
</P
></LI
></UL
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN156244"
>F.33.5.4. Trusted Procedures</A
></H3
><P
> Trusted procedures are similar to security definer functions or setuid
commands. <SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
> provides a feature to allow trusted
code to run using a security label different from that of the client,
generally for the purpose of providing highly controlled access to
sensitive data (e.g. rows might be omitted, or the precision of stored
values might be reduced). Whether or not a function acts as a trusted
procedure is controlled by its security label and the operating system
security policy. For example:
</P
><PRE
CLASS="SCREEN"
>postgres=# CREATE TABLE customer (
cid int primary key,
cname text,
credit text
);
CREATE TABLE
postgres=# SECURITY LABEL ON COLUMN customer.credit
IS 'system_u:object_r:sepgsql_secret_table_t:s0';
SECURITY LABEL
postgres=# CREATE FUNCTION show_credit(int) RETURNS text
AS 'SELECT regexp_replace(credit, ''-[0-9]+$'', ''-xxxx'', ''g'')
FROM customer WHERE cid = $1'
LANGUAGE sql;
CREATE FUNCTION
postgres=# SECURITY LABEL ON FUNCTION show_credit(int)
IS 'system_u:object_r:sepgsql_trusted_proc_exec_t:s0';
SECURITY LABEL</PRE
><P
> The above operations should be performed by an administrative user.
</P
><PRE
CLASS="SCREEN"
>postgres=# SELECT * FROM customer;
ERROR: SELinux: security policy violation
postgres=# SELECT cid, cname, show_credit(cid) FROM customer;
cid | cname | show_credit
-----+--------+---------------------
1 | taro | 1111-2222-3333-xxxx
2 | hanako | 5555-6666-7777-xxxx
(2 rows)</PRE
><P
> In this case, a regular user cannot reference <TT
CLASS="LITERAL"
>customer.credit</TT
>
directly, but a trusted procedure <TT
CLASS="LITERAL"
>show_credit</TT
> allows him
to print the credit card numbers of customers with some of the digits
masked out.
</P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN156254"
>F.33.5.5. Dynamic Domain Transitions</A
></H3
><P
> It is possible to use SELinux's dynamic domain transition feature
to switch the security label of the client process, the client domain,
to a new context, if that is allowed by the security policy.
The client domain needs the <TT
CLASS="LITERAL"
>setcurrent</TT
> permission and also
<TT
CLASS="LITERAL"
>dyntransition</TT
> from the old to the new domain.
</P
><P
> Dynamic domain transitions should be considered carefully, because they
allow users to switch their label, and therefore their privileges,
at their option, rather than (as in the case of a trusted procedure)
as mandated by the system.
Thus, the <TT
CLASS="LITERAL"
>dyntransition</TT
> permission is only considered
safe when used to switch to a domain with a smaller set of privileges than
the original one. For example:
</P
><PRE
CLASS="SCREEN"
>regression=# select sepgsql_getcon();
sepgsql_getcon
-------------------------------------------------------
unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
(1 row)
regression=# SELECT sepgsql_setcon('unconfined_u:unconfined_r:unconfined_t:s0-s0:c1.c4');
sepgsql_setcon
----------------
t
(1 row)
regression=# SELECT sepgsql_setcon('unconfined_u:unconfined_r:unconfined_t:s0-s0:c1.c1023');
ERROR: SELinux: security policy violation</PRE
><P
> In this example above we were allowed to switch from the larger MCS
range <TT
CLASS="LITERAL"
>c1.c1023</TT
> to the smaller range <TT
CLASS="LITERAL"
>c1.c4</TT
>, but
switching back was denied.
</P
><P
> A combination of dynamic domain transition and trusted procedure
enables an interesting use case that fits the typical process life-cycle
of connection pooling software.
Even if your connection pooling software is not allowed to run most
of SQL commands, you can allow it to switch the security label
of the client using the <TT
CLASS="LITERAL"
>sepgsql_setcon()</TT
> function
from within a trusted procedure; that should take some
credential to authorize the request to switch the client label.
After that, this session will have the privileges of the target user,
rather than the connection pooler.
The connection pooler can later revert the security label change by
again using <TT
CLASS="LITERAL"
>sepgsql_setcon()</TT
> with
<TT
CLASS="LITERAL"
>NULL</TT
> argument, again invoked from within a trusted
procedure with appropriate permissions checks.
The point here is that only the trusted procedure actually has permission
to change the effective security label, and only does so when given proper
credentials. Of course, for secure operation, the credential store
(table, procedure definition, or whatever) must be protected from
unauthorized access.
</P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN156269"
>F.33.5.6. Miscellaneous</A
></H3
><P
> We reject the <A
HREF="sql-load.html"
>LOAD</A
> command across the board, because
any module loaded could easily circumvent security policy enforcement.
</P
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SEPGSQL-FUNCTIONS"
>F.33.6. Sepgsql Functions</A
></H2
><P
> <A
HREF="sepgsql.html#SEPGSQL-FUNCTIONS-TABLE"
>Table F-27</A
> shows the available functions.
</P
><DIV
CLASS="TABLE"
><A
NAME="SEPGSQL-FUNCTIONS-TABLE"
></A
><P
><B
>Table F-27. Sepgsql Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><TBODY
><TR
><TD
><TT
CLASS="LITERAL"
>sepgsql_getcon() returns text</TT
></TD
><TD
> Returns the client domain, the current security label of the client.
</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
>sepgsql_setcon(text) returns bool</TT
></TD
><TD
> Switches the client domain of the current session to the new domain,
if allowed by the security policy.
It also accepts <TT
CLASS="LITERAL"
>NULL</TT
> input as a request to transition
to the client's original domain.
</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
>sepgsql_mcstrans_in(text) returns text</TT
></TD
><TD
>Translates the given qualifies MLS/MCS range into raw format if
the mcstrans daemon is running.
</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
>sepgsql_mcstrans_out(text) returns text</TT
></TD
><TD
>Translates the given raw MCS/MCS range into qualified format if
the mcstrans daemon is running.
</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
>sepgsql_restorecon(text) returns bool</TT
></TD
><TD
> Sets up initial security labels for all objects within the
current database. The argument may be NULL, or the name of a specfile
to be used as alternative of the system default.
</TD
></TR
></TBODY
></TABLE
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SEPGSQL-LIMITATIONS"
>F.33.7. Limitations</A
></H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>Data Definition Language (DDL) Permissions</DT
><DD
><P
> Due to implementation restrictions, some DDL operations do not
check permissions.
</P
></DD
><DT
>Data Control Language (DCL) Permissions</DT
><DD
><P
> Due to implementation restrictions, DCL operations do not check
permissions.
</P
></DD
><DT
>Row-level access control</DT
><DD
><P
> <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> does not support row-level access; therefore,
<TT
CLASS="FILENAME"
>sepgsql</TT
> does not support it either.
</P
></DD
><DT
>Covert channels</DT
><DD
><P
> <TT
CLASS="FILENAME"
>sepgsql</TT
> does not try to hide the existence of
a certain object, even if the user is not allowed to reference it.
For example, we can infer the existence of an invisible object as
a result of primary key conflicts, foreign key violations, and so on,
even if we cannot obtain the contents of the object. The existence
of a top secret table cannot be hidden; we only hope to conceal its
contents.
</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SEPGSQL-RESOURCES"
>F.33.8. External Resources</A
></H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><A
HREF="http://wiki.postgresql.org/wiki/SEPostgreSQL"
TARGET="_top"
>SE-PostgreSQL Introduction</A
></DT
><DD
><P
> This wiki page provides a brief overview, security design, architecture,
administration and upcoming features.
</P
></DD
><DT
><A
HREF="http://docs.fedoraproject.org/selinux-user-guide/"
TARGET="_top"
>Fedora SELinux User Guide</A
></DT
><DD
><P
> This document provides a wide spectrum of knowledge to administer
<SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
> on your systems.
It focuses primarily on Fedora, but is not limited to Fedora.
</P
></DD
><DT
><A
HREF="http://docs.fedoraproject.org/selinux-faq"
TARGET="_top"
>Fedora SELinux FAQ</A
></DT
><DD
><P
> This document answers frequently asked questions about
<SPAN
CLASS="PRODUCTNAME"
>SELinux</SPAN
>.
It focuses primarily on Fedora, but is not limited to Fedora.
</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SEPGSQL-AUTHOR"
>F.33.9. Author</A
></H2
><P
> KaiGai Kohei <CODE
CLASS="EMAIL"
><<A
HREF="mailto:kaigai@ak.jp.nec.com"
>kaigai@ak.jp.nec.com</A
>></CODE
>
</P
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