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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >sepgsql</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 9.2.24 Documentation" HREF="index.html"><LINK REL="UP" TITLE="Additional Supplied Modules" HREF="contrib.html"><LINK REL="PREVIOUS" TITLE="seg" HREF="seg.html"><LINK REL="NEXT" TITLE="spi" HREF="contrib-spi.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2017-11-06T22:43:11"></HEAD ><BODY CLASS="SECT1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="5" ALIGN="center" VALIGN="bottom" ><A HREF="index.html" >PostgreSQL 9.2.24 Documentation</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A TITLE="seg" HREF="seg.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="contrib.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Appendix F. Additional Supplied Modules</TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="spi" HREF="contrib-spi.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="SEPGSQL" >F.32. 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.32.7</A >. </P ></TD ></TR ></TABLE ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="SEPGSQL-OVERVIEW" >F.32.1. 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.32.2. 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 > 2.0.99 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.32.3. 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.32.2</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 1.04</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.32.8</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.32.4. 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.32.5. Features</A ></H2 ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN151925" >F.32.5.1. 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 unlabelled 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 and the label assigned to the new object's parent 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="AEN151934" >F.32.5.2. 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 > is defined, but is not checked in this version. </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="AEN151972" >F.32.5.3. 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 > When a <TT CLASS="LITERAL" >CREATE</TT > command is executed, <TT CLASS="LITERAL" >create</TT > will be checked on the object being constructed for each object types. A default security label will be assigned to the new database object, and the <TT CLASS="LITERAL" >create</TT > permission will be checked on the pair of security label of the client and the new object itself. We consider <A HREF="sql-createtable.html" >CREATE TABLE</A > to construct a table and underlying columns at the same time, so it requires the users to have permission to create both the table and its columns. </P ><P > A few additional checks are applied depending on object types. On <A HREF="sql-createdatabase.html" >CREATE DATABASE</A >, <TT CLASS="LITERAL" >getattr</TT > permission will be checked on the source or template database of the new database, not only <TT CLASS="LITERAL" >create</TT > on the new database. On creation of objects within a particular schema (tables, views, sequences and procedures), <TT CLASS="LITERAL" >add_name</TT > will be also checked on the schema, not only <TT CLASS="LITERAL" >create</TT > on the new object itself. </P ><P > When <TT CLASS="LITERAL" >DROP</TT > command is executed, <TT CLASS="LITERAL" >drop</TT > will be checked on the object being removed for each object types. 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 <A HREF="sql-security-label.html" >SECURITY LABEL</A > is executed, <TT CLASS="LITERAL" >setattr</TT > and <TT CLASS="LITERAL" >relabelfrom</TT > will be checked on the object being relabeled with its old security label, then <TT CLASS="LITERAL" >relabelto</TT > with the supplied new security label. </P ><P > In the case 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 ></DIV ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN152000" >F.32.5.4. 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="AEN152010" >F.32.5.5. 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="AEN152025" >F.32.5.6. 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.32.6. Sepgsql Functions</A ></H2 ><P > <A HREF="sepgsql.html#SEPGSQL-FUNCTIONS-TABLE" >Table F-29</A > shows the available functions. </P ><DIV CLASS="TABLE" ><A NAME="SEPGSQL-FUNCTIONS-TABLE" ></A ><P ><B >Table F-29. 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 qualified 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 MLS/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.32.7. 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.32.8. External Resources</A ></H2 ><P ></P ><DIV CLASS="VARIABLELIST" ><DL ><DT ><A HREF="https://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.32.9. 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 ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="seg.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="contrib-spi.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >seg</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="contrib.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >spi</TD ></TR ></TABLE ></DIV ></BODY ></HTML >