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1<?xml version="1.0" encoding="UTF-8" standalone="no"?>2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>F.40. sepgsql — SELinux-, label-based mandatory access control (MAC) security module</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="seg.html" title="F.39. seg — a datatype for line segments or floating point intervals" /><link rel="next" href="contrib-spi.html" title="F.41. spi — Server Programming Interface features/examples" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">F.40. sepgsql —3 SELinux-, label-based mandatory access control (MAC) security module</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="seg.html" title="F.39. seg — a datatype for line segments or floating point intervals">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="contrib.html" title="Appendix F. Additional Supplied Modules and Extensions">Up</a></td><th width="60%" align="center">Appendix F. Additional Supplied Modules and Extensions</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="contrib-spi.html" title="F.41. spi — Server Programming Interface features/examples">Next</a></td></tr></table><hr /></div><div class="sect1" id="SEPGSQL"><div class="titlepage"><div><div><h2 class="title" style="clear: both">F.40. sepgsql —4 SELinux-, label-based mandatory access control (MAC) security module <a href="#SEPGSQL" class="id_link">#</a></h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-OVERVIEW">F.40.1. Overview</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-INSTALLATION">F.40.2. Installation</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-REGRESSION">F.40.3. Regression Tests</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-PARAMETERS">F.40.4. GUC Parameters</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-FEATURES">F.40.5. Features</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-FUNCTIONS">F.40.6. Sepgsql Functions</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-LIMITATIONS">F.40.7. Limitations</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-RESOURCES">F.40.8. External Resources</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-AUTHOR">F.40.9. Author</a></span></dt></dl></div><a id="id-1.11.7.50.2" class="indexterm"></a><p>5 <code class="filename">sepgsql</code> is a loadable module that supports label-based6 mandatory access control (MAC) based on <span class="productname">SELinux</span> security7 policy.8 </p><div class="warning"><h3 class="title">Warning</h3><p>9 The current implementation has significant limitations, and does not10 enforce mandatory access control for all actions. See11 <a class="xref" href="sepgsql.html#SEPGSQL-LIMITATIONS" title="F.40.7. Limitations">Section F.40.7</a>.12 </p></div><div class="sect2" id="SEPGSQL-OVERVIEW"><div class="titlepage"><div><div><h3 class="title">F.40.1. Overview <a href="#SEPGSQL-OVERVIEW" class="id_link">#</a></h3></div></div></div><p>13 This module integrates with <span class="productname">SELinux</span> to provide an14 additional layer of security checking above and beyond what is normally15 provided by <span class="productname">PostgreSQL</span>. From the perspective of16 <span class="productname">SELinux</span>, this module allows17 <span class="productname">PostgreSQL</span> to function as a user-space object18 manager. Each table or function access initiated by a DML query will be19 checked against the system security policy. This check is in addition to20 the usual SQL permissions checking performed by21 <span class="productname">PostgreSQL</span>.22 </p><p>23 <span class="productname">SELinux</span> access control decisions are made using24 security labels, which are represented by strings such as25 <code class="literal">system_u:object_r:sepgsql_table_t:s0</code>. Each access control26 decision involves two labels: the label of the subject attempting to27 perform the action, and the label of the object on which the operation is28 to be performed. Since these labels can be applied to any sort of object,29 access control decisions for objects stored within the database can be30 (and, with this module, are) subjected to the same general criteria used31 for objects of any other type, such as files. This design is intended to32 allow a centralized security policy to protect information assets33 independent of the particulars of how those assets are stored.34 </p><p>35 The <a class="link" href="sql-security-label.html" title="SECURITY LABEL"><code class="command">SECURITY LABEL</code></a> statement allows assignment of36 a security label to a database object.37 </p></div><div class="sect2" id="SEPGSQL-INSTALLATION"><div class="titlepage"><div><div><h3 class="title">F.40.2. Installation <a href="#SEPGSQL-INSTALLATION" class="id_link">#</a></h3></div></div></div><p>38 <code class="filename">sepgsql</code> can only be used on <span class="productname">Linux</span>39 2.6.28 or higher with <span class="productname">SELinux</span> enabled.40 It is not available on any other platform. You will also need41 <span class="productname">libselinux</span> 2.1.10 or higher and42 <span class="productname">selinux-policy</span> 3.9.13 or higher (although some43 distributions may backport the necessary rules into older policy44 versions).45 </p><p>46 The <code class="command">sestatus</code> command allows you to check the status of47 <span class="productname">SELinux</span>. A typical display is:48</p><pre class="screen">49$ sestatus50SELinux status: enabled51SELinuxfs mount: /selinux52Current mode: enforcing53Mode from config file: enforcing54Policy version: 2455Policy from config file: targeted56</pre><p>57 If <span class="productname">SELinux</span> is disabled or not installed, you must set58 that product up first before installing this module.59 </p><p>60 To build this module, include the option <code class="literal">--with-selinux</code> in61 your PostgreSQL <code class="literal">configure</code> command. Be sure that the62 <code class="filename">libselinux-devel</code> RPM is installed at build time.63 </p><p>64 To use this module, you must include <code class="literal">sepgsql</code>65 in the <a class="xref" href="runtime-config-client.html#GUC-SHARED-PRELOAD-LIBRARIES">shared_preload_libraries</a> parameter in66 <code class="filename">postgresql.conf</code>. The module will not function correctly67 if loaded in any other manner. Once the module is loaded, you68 should execute <code class="filename">sepgsql.sql</code> in each database.69 This will install functions needed for security label management, and70 assign initial security labels.71 </p><p>72 Here is an example showing how to initialize a fresh database cluster73 with <code class="filename">sepgsql</code> functions and security labels installed.74 Adjust the paths shown as appropriate for your installation:75 </p><pre class="screen">76$ export PGDATA=/path/to/data/directory77$ initdb78$ vi $PGDATA/postgresql.conf79 change80 #shared_preload_libraries = '' # (change requires restart)81 to82 shared_preload_libraries = 'sepgsql' # (change requires restart)83$ for DBNAME in template0 template1 postgres; do84 postgres --single -F -c exit_on_error=true $DBNAME \85 </usr/local/pgsql/share/contrib/sepgsql.sql >/dev/null86 done87</pre><p>88 Please note that you may see some or all of the following notifications89 depending on the particular versions you have of90 <span class="productname">libselinux</span> and <span class="productname">selinux-policy</span>:91</p><pre class="screen">92/etc/selinux/targeted/contexts/sepgsql_contexts: line 33 has invalid object type db_blobs93/etc/selinux/targeted/contexts/sepgsql_contexts: line 36 has invalid object type db_language94/etc/selinux/targeted/contexts/sepgsql_contexts: line 37 has invalid object type db_language95/etc/selinux/targeted/contexts/sepgsql_contexts: line 38 has invalid object type db_language96/etc/selinux/targeted/contexts/sepgsql_contexts: line 39 has invalid object type db_language97/etc/selinux/targeted/contexts/sepgsql_contexts: line 40 has invalid object type db_language98</pre><p>99 These messages are harmless and should be ignored.100 </p><p>101 If the installation process completes without error, you can now start the102 server normally.103 </p></div><div class="sect2" id="SEPGSQL-REGRESSION"><div class="titlepage"><div><div><h3 class="title">F.40.3. Regression Tests <a href="#SEPGSQL-REGRESSION" class="id_link">#</a></h3></div></div></div><p>104 Due to the nature of <span class="productname">SELinux</span>, running the105 regression tests for <code class="filename">sepgsql</code> requires several extra106 configuration steps, some of which must be done as root.107 The regression tests will not be run by an ordinary108 <code class="literal">make check</code> or <code class="literal">make installcheck</code> command; you must109 set up the configuration and then invoke the test script manually.110 The tests must be run in the <code class="filename">contrib/sepgsql</code> directory111 of a configured PostgreSQL build tree. Although they require a build tree,112 the tests are designed to be executed against an installed server,113 that is they are comparable to <code class="literal">make installcheck</code> not114 <code class="literal">make check</code>.115 </p><p>116 First, set up <code class="filename">sepgsql</code> in a working database117 according to the instructions in <a class="xref" href="sepgsql.html#SEPGSQL-INSTALLATION" title="F.40.2. Installation">Section F.40.2</a>.118 Note that the current operating system user must be able to connect to the119 database as superuser without password authentication.120 </p><p>121 Second, build and install the policy package for the regression test.122 The <code class="filename">sepgsql-regtest</code> policy is a special purpose policy package123 which provides a set of rules to be allowed during the regression tests.124 It should be built from the policy source file125 <code class="filename">sepgsql-regtest.te</code>, which is done using126 <code class="command">make</code> with a Makefile supplied by SELinux.127 You will need to locate the appropriate128 Makefile on your system; the path shown below is only an example.129 (This Makefile is usually supplied by the130 <code class="filename">selinux-policy-devel</code> or131 <code class="filename">selinux-policy</code> RPM.)132 Once built, install this policy package using the133 <code class="command">semodule</code> command, which loads supplied policy packages134 into the kernel. If the package is correctly installed,135 <code class="literal"><code class="command">semodule</code> -l</code> should list <code class="literal">sepgsql-regtest</code> as an136 available policy package:137 </p><pre class="screen">138$ cd .../contrib/sepgsql139$ make -f /usr/share/selinux/devel/Makefile140$ sudo semodule -u sepgsql-regtest.pp141$ sudo semodule -l | grep sepgsql142sepgsql-regtest 1.07143</pre><p>144 Third, turn on <code class="literal">sepgsql_regression_test_mode</code>.145 For security reasons, the rules in <code class="filename">sepgsql-regtest</code>146 are not enabled by default;147 the <code class="literal">sepgsql_regression_test_mode</code> parameter enables148 the rules needed to launch the regression tests.149 It can be turned on using the <code class="command">setsebool</code> command:150 </p><pre class="screen">151$ sudo setsebool sepgsql_regression_test_mode on152$ getsebool sepgsql_regression_test_mode153sepgsql_regression_test_mode --> on154</pre><p>155 Fourth, verify your shell is operating in the <code class="literal">unconfined_t</code>156 domain:157 </p><pre class="screen">158$ id -Z159unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023160</pre><p>161 See <a class="xref" href="sepgsql.html#SEPGSQL-RESOURCES" title="F.40.8. External Resources">Section F.40.8</a> for details on adjusting your162 working domain, if necessary.163 </p><p>164 Finally, run the regression test script:165 </p><pre class="screen">166$ ./test_sepgsql167</pre><p>168 This script will attempt to verify that you have done all the configuration169 steps correctly, and then it will run the regression tests for the170 <code class="filename">sepgsql</code> module.171 </p><p>172 After completing the tests, it's recommended you disable173 the <code class="literal">sepgsql_regression_test_mode</code> parameter:174 </p><pre class="screen">175$ sudo setsebool sepgsql_regression_test_mode off176</pre><p>177 You might prefer to remove the <code class="filename">sepgsql-regtest</code> policy178 entirely:179 </p><pre class="screen">180$ sudo semodule -r sepgsql-regtest181</pre></div><div class="sect2" id="SEPGSQL-PARAMETERS"><div class="titlepage"><div><div><h3 class="title">F.40.4. GUC Parameters <a href="#SEPGSQL-PARAMETERS" class="id_link">#</a></h3></div></div></div><div class="variablelist"><dl class="variablelist"><dt id="GUC-SEPGSQL-PERMISSIVE"><span class="term">182 <code class="varname">sepgsql.permissive</code> (<code class="type">boolean</code>)183 <a id="id-1.11.7.50.8.2.1.1.3" class="indexterm"></a>184 </span> <a href="#GUC-SEPGSQL-PERMISSIVE" class="id_link">#</a></dt><dd><p>185 This parameter enables <code class="filename">sepgsql</code> to function186 in permissive mode, regardless of the system setting.187 The default is off.188 This parameter can only be set in the <code class="filename">postgresql.conf</code>189 file or on the server command line.190 </p><p>191 When this parameter is on, <code class="filename">sepgsql</code> functions192 in permissive mode, even if SELinux in general is working in enforcing193 mode. This parameter is primarily useful for testing purposes.194 </p></dd><dt id="GUC-SEPGSQL-DEBUG-AUDIT"><span class="term">195 <code class="varname">sepgsql.debug_audit</code> (<code class="type">boolean</code>)196 <a id="id-1.11.7.50.8.2.2.1.3" class="indexterm"></a>197 </span> <a href="#GUC-SEPGSQL-DEBUG-AUDIT" class="id_link">#</a></dt><dd><p>198 This parameter enables the printing of audit messages regardless of199 the system policy settings.200 The default is off, which means that messages will be printed according201 to the system settings.202 </p><p>203 The security policy of <span class="productname">SELinux</span> also has rules to204 control whether or not particular accesses are logged.205 By default, access violations are logged, but allowed206 accesses are not.207 </p><p>208 This parameter forces all possible logging to be turned on, regardless209 of the system policy.210 </p></dd></dl></div></div><div class="sect2" id="SEPGSQL-FEATURES"><div class="titlepage"><div><div><h3 class="title">F.40.5. Features <a href="#SEPGSQL-FEATURES" class="id_link">#</a></h3></div></div></div><div class="sect3" id="SEPGSQL-FEATURES-CONTROLLED-OBJ-CLASSES"><div class="titlepage"><div><div><h4 class="title">F.40.5.1. Controlled Object Classes <a href="#SEPGSQL-FEATURES-CONTROLLED-OBJ-CLASSES" class="id_link">#</a></h4></div></div></div><p>211 The security model of <span class="productname">SELinux</span> describes all the access212 control rules as relationships between a subject entity (typically,213 a client of the database) and an object entity (such as a database214 object), each of which is215 identified by a security label. If access to an unlabeled object is216 attempted, the object is treated as if it were assigned the label217 <code class="literal">unlabeled_t</code>.218 </p><p>219 Currently, <code class="filename">sepgsql</code> allows security labels to be220 assigned to schemas, tables, columns, sequences, views, and functions.221 When <code class="filename">sepgsql</code> is in use, security labels are222 automatically assigned to supported database objects at creation time.223 This label is called a default security label, and is decided according224 to the system security policy, which takes as input the creator's label,225 the label assigned to the new object's parent object and optionally name226 of the constructed object.227 </p><p>228 A new database object basically inherits the security label of the parent229 object, except when the security policy has special rules known as230 type-transition rules, in which case a different label may be applied.231 For schemas, the parent object is the current database; for tables,232 sequences, views, and functions, it is the containing schema; for columns,233 it is the containing table.234 </p></div><div class="sect3" id="SEPGSQL-FEATURES-DML-PERMISSIONS"><div class="titlepage"><div><div><h4 class="title">F.40.5.2. DML Permissions <a href="#SEPGSQL-FEATURES-DML-PERMISSIONS" class="id_link">#</a></h4></div></div></div><p>235 For tables, <code class="literal">db_table:select</code>, <code class="literal">db_table:insert</code>,236 <code class="literal">db_table:update</code> or <code class="literal">db_table:delete</code> are237 checked for all the referenced target tables depending on the kind of238 statement; in addition, <code class="literal">db_table:select</code> is also checked for239 all the tables that contain columns referenced in the240 <code class="literal">WHERE</code> or <code class="literal">RETURNING</code> clause, as a data source241 for <code class="literal">UPDATE</code>, and so on.242 </p><p>243 Column-level permissions will also be checked for each referenced column.244 <code class="literal">db_column:select</code> is checked on not only the columns being245 read using <code class="literal">SELECT</code>, but those being referenced in other DML246 statements; <code class="literal">db_column:update</code> or <code class="literal">db_column:insert</code>247 will also be checked for columns being modified by <code class="literal">UPDATE</code> or248 <code class="literal">INSERT</code>.249 </p><p>250 For example, consider:251</p><pre class="synopsis">252UPDATE t1 SET x = 2, y = func1(y) WHERE z = 100;253</pre><p>254 255 Here, <code class="literal">db_column:update</code> will be checked for256 <code class="literal">t1.x</code>, since it is being updated,257 <code class="literal">db_column:{select update}</code> will be checked for258 <code class="literal">t1.y</code>, since it is both updated and referenced, and259 <code class="literal">db_column:select</code> will be checked for <code class="literal">t1.z</code>, since260 it is only referenced.261 <code class="literal">db_table:{select update}</code> will also be checked262 at the table level.263 </p><p>264 For sequences, <code class="literal">db_sequence:get_value</code> is checked when we265 reference a sequence object using <code class="literal">SELECT</code>; however, note that we266 do not currently check permissions on execution of corresponding functions267 such as <code class="literal">lastval()</code>.268 </p><p>269 For views, <code class="literal">db_view:expand</code> will be checked, then any other270 required permissions will be checked on the objects being271 expanded from the view, individually.272 </p><p>273 For functions, <code class="literal">db_procedure:{execute}</code> will be checked when274 user tries to execute a function as a part of query, or using fast-path275 invocation. If this function is a trusted procedure, it also checks276 <code class="literal">db_procedure:{entrypoint}</code> permission to check whether it277 can perform as entry point of trusted procedure.278 </p><p>279 In order to access any schema object, <code class="literal">db_schema:search</code>280 permission is required on the containing schema. When an object is281 referenced without schema qualification, schemas on which this282 permission is not present will not be searched (just as if the user did283 not have <code class="literal">USAGE</code> privilege on the schema). If an explicit schema284 qualification is present, an error will occur if the user does not have285 the requisite permission on the named schema.286 </p><p>287 The client must be allowed to access all referenced tables and288 columns, even if they originated from views which were then expanded,289 so that we apply consistent access control rules independent of the manner290 in which the table contents are referenced.291 </p><p>292 The default database privilege system allows database superusers to293 modify system catalogs using DML commands, and reference or modify294 toast tables. These operations are prohibited when295 <code class="filename">sepgsql</code> is enabled.296 </p></div><div class="sect3" id="SEPGSQL-FEATURES-DDL-PERMISSIONS"><div class="titlepage"><div><div><h4 class="title">F.40.5.3. DDL Permissions <a href="#SEPGSQL-FEATURES-DDL-PERMISSIONS" class="id_link">#</a></h4></div></div></div><p>297 <span class="productname">SELinux</span> defines several permissions to control common298 operations for each object type; such as creation, alter, drop and299 relabel of security label. In addition, several object types have300 special permissions to control their characteristic operations; such as301 addition or deletion of name entries within a particular schema.302 </p><p>303 Creating a new database object requires <code class="literal">create</code> permission.304 <span class="productname">SELinux</span> will grant or deny this permission based on the305 client's security label and the proposed security label for the new306 object. In some cases, additional privileges are required:307 </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>308 <a class="link" href="sql-createdatabase.html" title="CREATE DATABASE"><code class="command">CREATE DATABASE</code></a> additionally requires309 <code class="literal">getattr</code> permission for the source or template database.310 </p></li><li class="listitem"><p>311 Creating a schema object additionally requires <code class="literal">add_name</code>312 permission on the parent schema.313 </p></li><li class="listitem"><p>314 Creating a table additionally requires permission to create each315 individual table column, just as if each table column were a316 separate top-level object.317 </p></li><li class="listitem"><p>318 Creating a function marked as <code class="literal">LEAKPROOF</code> additionally319 requires <code class="literal">install</code> permission. (This permission is also320 checked when <code class="literal">LEAKPROOF</code> is set for an existing function.)321 </p></li></ul></div><p>322 When <code class="literal">DROP</code> command is executed, <code class="literal">drop</code> will be323 checked on the object being removed. Permissions will be also checked for324 objects dropped indirectly via <code class="literal">CASCADE</code>. Deletion of objects325 contained within a particular schema (tables, views, sequences and326 procedures) additionally requires <code class="literal">remove_name</code> on the schema.327 </p><p>328 When <code class="literal">ALTER</code> command is executed, <code class="literal">setattr</code> will be329 checked on the object being modified for each object types, except for330 subsidiary objects such as the indexes or triggers of a table, where331 permissions are instead checked on the parent object. In some cases,332 additional permissions are required:333 </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>334 Moving an object to a new schema additionally requires335 <code class="literal">remove_name</code> permission on the old schema and336 <code class="literal">add_name</code> permission on the new one.337 </p></li><li class="listitem"><p>338 Setting the <code class="literal">LEAKPROOF</code> attribute on a function requires339 <code class="literal">install</code> permission.340 </p></li><li class="listitem"><p>341 Using <a class="link" href="sql-security-label.html" title="SECURITY LABEL"><code class="command">SECURITY LABEL</code></a> on an object additionally342 requires <code class="literal">relabelfrom</code> permission for the object in343 conjunction with its old security label and <code class="literal">relabelto</code>344 permission for the object in conjunction with its new security label.345 (In cases where multiple label providers are installed and the user346 tries to set a security label, but it is not managed by347 <span class="productname">SELinux</span>, only <code class="literal">setattr</code> should be checked here.348 This is currently not done due to implementation restrictions.)349 </p></li></ul></div></div><div class="sect3" id="SEPGSQL-FEATURES-TRUSTED-PROCEDURES"><div class="titlepage"><div><div><h4 class="title">F.40.5.4. Trusted Procedures <a href="#SEPGSQL-FEATURES-TRUSTED-PROCEDURES" class="id_link">#</a></h4></div></div></div><p>350 Trusted procedures are similar to security definer functions or setuid351 commands. <span class="productname">SELinux</span> provides a feature to allow trusted352 code to run using a security label different from that of the client,353 generally for the purpose of providing highly controlled access to354 sensitive data (e.g., rows might be omitted, or the precision of stored355 values might be reduced). Whether or not a function acts as a trusted356 procedure is controlled by its security label and the operating system357 security policy. For example:358 </p><pre class="screen">359postgres=# CREATE TABLE customer (360 cid int primary key,361 cname text,362 credit text363 );364CREATE TABLE365postgres=# SECURITY LABEL ON COLUMN customer.credit366 IS 'system_u:object_r:sepgsql_secret_table_t:s0';367SECURITY LABEL368postgres=# CREATE FUNCTION show_credit(int) RETURNS text369 AS 'SELECT regexp_replace(credit, ''-[0-9]+$'', ''-xxxx'', ''g'')370 FROM customer WHERE cid = $1'371 LANGUAGE sql;372CREATE FUNCTION373postgres=# SECURITY LABEL ON FUNCTION show_credit(int)374 IS 'system_u:object_r:sepgsql_trusted_proc_exec_t:s0';375SECURITY LABEL376</pre><p>377 The above operations should be performed by an administrative user.378 </p><pre class="screen">379postgres=# SELECT * FROM customer;380ERROR: SELinux: security policy violation381postgres=# SELECT cid, cname, show_credit(cid) FROM customer;382 cid | cname | show_credit383-----+--------+---------------------384 1 | taro | 1111-2222-3333-xxxx385 2 | hanako | 5555-6666-7777-xxxx386(2 rows)387</pre><p>388 In this case, a regular user cannot reference <code class="literal">customer.credit</code>389 directly, but a trusted procedure <code class="literal">show_credit</code> allows the user390 to print the credit card numbers of customers with some of the digits391 masked out.392 </p></div><div class="sect3" id="SEPGSQL-FEATURES-DYNAMIC-DOMAIN-TRANSITIONS"><div class="titlepage"><div><div><h4 class="title">F.40.5.5. Dynamic Domain Transitions <a href="#SEPGSQL-FEATURES-DYNAMIC-DOMAIN-TRANSITIONS" class="id_link">#</a></h4></div></div></div><p>393 It is possible to use SELinux's dynamic domain transition feature394 to switch the security label of the client process, the client domain,395 to a new context, if that is allowed by the security policy.396 The client domain needs the <code class="literal">setcurrent</code> permission and also397 <code class="literal">dyntransition</code> from the old to the new domain.398 </p><p>399 Dynamic domain transitions should be considered carefully, because they400 allow users to switch their label, and therefore their privileges,401 at their option, rather than (as in the case of a trusted procedure)402 as mandated by the system.403 Thus, the <code class="literal">dyntransition</code> permission is only considered404 safe when used to switch to a domain with a smaller set of privileges than405 the original one. For example:406 </p><pre class="screen">407regression=# select sepgsql_getcon();408 sepgsql_getcon409-------------------------------------------------------410 unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023411(1 row)412 413regression=# SELECT sepgsql_setcon('unconfined_u:unconfined_r:unconfined_t:s0-s0:c1.c4');414 sepgsql_setcon415----------------416 t417(1 row)418 419regression=# SELECT sepgsql_setcon('unconfined_u:unconfined_r:unconfined_t:s0-s0:c1.c1023');420ERROR: SELinux: security policy violation421</pre><p>422 In this example above we were allowed to switch from the larger MCS423 range <code class="literal">c1.c1023</code> to the smaller range <code class="literal">c1.c4</code>, but424 switching back was denied.425 </p><p>426 A combination of dynamic domain transition and trusted procedure427 enables an interesting use case that fits the typical process life-cycle428 of connection pooling software.429 Even if your connection pooling software is not allowed to run most430 of SQL commands, you can allow it to switch the security label431 of the client using the <code class="literal">sepgsql_setcon()</code> function432 from within a trusted procedure; that should take some433 credential to authorize the request to switch the client label.434 After that, this session will have the privileges of the target user,435 rather than the connection pooler.436 The connection pooler can later revert the security label change by437 again using <code class="literal">sepgsql_setcon()</code> with438 <code class="literal">NULL</code> argument, again invoked from within a trusted439 procedure with appropriate permissions checks.440 The point here is that only the trusted procedure actually has permission441 to change the effective security label, and only does so when given proper442 credentials. Of course, for secure operation, the credential store443 (table, procedure definition, or whatever) must be protected from444 unauthorized access.445 </p></div><div class="sect3" id="SEPGSQL-FEATURES-MISC"><div class="titlepage"><div><div><h4 class="title">F.40.5.6. Miscellaneous <a href="#SEPGSQL-FEATURES-MISC" class="id_link">#</a></h4></div></div></div><p>446 We reject the <a class="link" href="sql-load.html" title="LOAD"><code class="command">LOAD</code></a> command across the board, because447 any module loaded could easily circumvent security policy enforcement.448 </p></div></div><div class="sect2" id="SEPGSQL-FUNCTIONS"><div class="titlepage"><div><div><h3 class="title">F.40.6. Sepgsql Functions <a href="#SEPGSQL-FUNCTIONS" class="id_link">#</a></h3></div></div></div><p>449 <a class="xref" href="sepgsql.html#SEPGSQL-FUNCTIONS-TABLE" title="Table F.31. Sepgsql Functions">Table F.31</a> shows the available functions.450 </p><div class="table" id="SEPGSQL-FUNCTIONS-TABLE"><p class="title"><strong>Table F.31. Sepgsql Functions</strong></p><div class="table-contents"><table class="table" summary="Sepgsql Functions" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature">451 Function452 </p>453 <p>454 Description455 </p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">456 <code class="function">sepgsql_getcon</code> ()457 → <code class="returnvalue">text</code>458 </p>459 <p>460 Returns the client domain, the current security label of the client.461 </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">462 <code class="function">sepgsql_setcon</code> ( <code class="type">text</code> )463 → <code class="returnvalue">boolean</code>464 </p>465 <p>466 Switches the client domain of the current session to the new domain,467 if allowed by the security policy.468 It also accepts <code class="literal">NULL</code> input as a request to transition469 to the client's original domain.470 </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">471 <code class="function">sepgsql_mcstrans_in</code> ( <code class="type">text</code> )472 → <code class="returnvalue">text</code>473 </p>474 <p>475 Translates the given qualified MLS/MCS range into raw format if476 the mcstrans daemon is running.477 </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">478 <code class="function">sepgsql_mcstrans_out</code> ( <code class="type">text</code> )479 → <code class="returnvalue">text</code>480 </p>481 <p>482 Translates the given raw MLS/MCS range into qualified format if483 the mcstrans daemon is running.484 </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">485 <code class="function">sepgsql_restorecon</code> ( <code class="type">text</code> )486 → <code class="returnvalue">boolean</code>487 </p>488 <p>489 Sets up initial security labels for all objects within the490 current database. The argument may be <code class="literal">NULL</code>, or the491 name of a specfile to be used as alternative of the system default.492 </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="SEPGSQL-LIMITATIONS"><div class="titlepage"><div><div><h3 class="title">F.40.7. Limitations <a href="#SEPGSQL-LIMITATIONS" class="id_link">#</a></h3></div></div></div><div class="variablelist"><dl class="variablelist"><dt><span class="term">Data Definition Language (DDL) Permissions</span></dt><dd><p>493 Due to implementation restrictions, some DDL operations do not494 check permissions.495 </p></dd><dt><span class="term">Data Control Language (DCL) Permissions</span></dt><dd><p>496 Due to implementation restrictions, DCL operations do not check497 permissions.498 </p></dd><dt><span class="term">Row-level access control</span></dt><dd><p>499 <span class="productname">PostgreSQL</span> supports row-level access, but500 <code class="filename">sepgsql</code> does not.501 </p></dd><dt><span class="term">Covert channels</span></dt><dd><p>502 <code class="filename">sepgsql</code> does not try to hide the existence of503 a certain object, even if the user is not allowed to reference it.504 For example, we can infer the existence of an invisible object as505 a result of primary key conflicts, foreign key violations, and so on,506 even if we cannot obtain the contents of the object. The existence507 of a top secret table cannot be hidden; we only hope to conceal its508 contents.509 </p></dd></dl></div></div><div class="sect2" id="SEPGSQL-RESOURCES"><div class="titlepage"><div><div><h3 class="title">F.40.8. External Resources <a href="#SEPGSQL-RESOURCES" class="id_link">#</a></h3></div></div></div><div class="variablelist"><dl class="variablelist"><dt><span class="term"><a class="ulink" href="https://wiki.postgresql.org/wiki/SEPostgreSQL" target="_top">SE-PostgreSQL Introduction</a></span></dt><dd><p>510 This wiki page provides a brief overview, security design, architecture,511 administration and upcoming features.512 </p></dd><dt><span class="term"><a class="ulink" href="https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/selinux_users_and_administrators_guide/index" target="_top">SELinux User's and Administrator's Guide</a></span></dt><dd><p>513 This document provides a wide spectrum of knowledge to administer514 <span class="productname">SELinux</span> on your systems.515 It focuses primarily on Red Hat operating systems, but is not limited to them.516 </p></dd><dt><span class="term"><a class="ulink" href="https://fedoraproject.org/wiki/SELinux_FAQ" target="_top">Fedora SELinux FAQ</a></span></dt><dd><p>517 This document answers frequently asked questions about518 <span class="productname">SELinux</span>.519 It focuses primarily on Fedora, but is not limited to Fedora.520 </p></dd></dl></div></div><div class="sect2" id="SEPGSQL-AUTHOR"><div class="titlepage"><div><div><h3 class="title">F.40.9. Author <a href="#SEPGSQL-AUTHOR" class="id_link">#</a></h3></div></div></div><p>521 KaiGai Kohei <code class="email"><<a class="email" href="mailto:kaigai@ak.jp.nec.com">kaigai@ak.jp.nec.com</a>></code>522 </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="seg.html" title="F.39. seg — a datatype for line segments or floating point intervals">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="contrib.html" title="Appendix F. 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