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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-04 12:15:05 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-04 12:15:05 +0000 |
| commit | 46651ce6fe013220ed397add242004d764fc0153 (patch) | |
| tree | 6e5299f990f88e60174a1d3ae6e48eedd2688b2b /doc/src/sgml/html/sepgsql.html | |
| parent | Initial commit. (diff) | |
| download | postgresql-14-upstream.tar.xz postgresql-14-upstream.zip | |
Adding upstream version 14.5.upstream/14.5upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'doc/src/sgml/html/sepgsql.html')
| -rw-r--r-- | doc/src/sgml/html/sepgsql.html | 520 |
1 files changed, 520 insertions, 0 deletions
diff --git a/doc/src/sgml/html/sepgsql.html b/doc/src/sgml/html/sepgsql.html new file mode 100644 index 0000000..a50c006 --- /dev/null +++ b/doc/src/sgml/html/sepgsql.html @@ -0,0 +1,520 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!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.37. sepgsql</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.36. seg" /><link rel="next" href="contrib-spi.html" title="F.38. spi" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">F.37. sepgsql</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="seg.html" title="F.36. seg">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="contrib.html" title="Appendix F. Additional Supplied Modules">Up</a></td><th width="60%" align="center">Appendix F. Additional Supplied Modules</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 14.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="contrib-spi.html" title="F.38. spi">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="SEPGSQL"><div class="titlepage"><div><div><h2 class="title" style="clear: both">F.37. sepgsql</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-OVERVIEW">F.37.1. Overview</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-INSTALLATION">F.37.2. Installation</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-REGRESSION">F.37.3. Regression Tests</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-PARAMETERS">F.37.4. GUC Parameters</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-FEATURES">F.37.5. Features</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-FUNCTIONS">F.37.6. Sepgsql Functions</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-LIMITATIONS">F.37.7. Limitations</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-RESOURCES">F.37.8. External Resources</a></span></dt><dt><span class="sect2"><a href="sepgsql.html#SEPGSQL-AUTHOR">F.37.9. Author</a></span></dt></dl></div><a id="id-1.11.7.46.2" class="indexterm"></a><p> + <code class="filename">sepgsql</code> 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"><h3 class="title">Warning</h3><p> + The current implementation has significant limitations, and does not + enforce mandatory access control for all actions. See + <a class="xref" href="sepgsql.html#SEPGSQL-LIMITATIONS" title="F.37.7. Limitations">Section F.37.7</a>. + </p></div><div class="sect2" id="SEPGSQL-OVERVIEW"><div class="titlepage"><div><div><h3 class="title">F.37.1. Overview</h3></div></div></div><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 + <code class="literal">system_u:object_r:sepgsql_table_t:s0</code>. 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 class="link" href="sql-security-label.html" title="SECURITY LABEL"><code class="command">SECURITY LABEL</code></a> statement allows assignment of + a security label to a database object. + </p></div><div class="sect2" id="SEPGSQL-INSTALLATION"><div class="titlepage"><div><div><h3 class="title">F.37.2. Installation</h3></div></div></div><p> + <code class="filename">sepgsql</code> 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 <code class="command">sestatus</code> 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 <code class="literal">--with-selinux</code> in + your PostgreSQL <code class="literal">configure</code> command. Be sure that the + <code class="filename">libselinux-devel</code> RPM is installed at build time. + </p><p> + To use this module, you must include <code class="literal">sepgsql</code> + in the <a class="xref" href="runtime-config-client.html#GUC-SHARED-PRELOAD-LIBRARIES">shared_preload_libraries</a> parameter in + <code class="filename">postgresql.conf</code>. The module will not function correctly + if loaded in any other manner. Once the module is loaded, you + should execute <code class="filename">sepgsql.sql</code> 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 <code class="filename">sepgsql</code> 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" id="SEPGSQL-REGRESSION"><div class="titlepage"><div><div><h3 class="title">F.37.3. Regression Tests</h3></div></div></div><p> + Due to the nature of <span class="productname">SELinux</span>, running the + regression tests for <code class="filename">sepgsql</code> requires several extra + configuration steps, some of which must be done as root. + The regression tests will not be run by an ordinary + <code class="literal">make check</code> or <code class="literal">make installcheck</code> command; you must + set up the configuration and then invoke the test script manually. + The tests must be run in the <code class="filename">contrib/sepgsql</code> 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 <code class="literal">make installcheck</code> not + <code class="literal">make check</code>. + </p><p> + First, set up <code class="filename">sepgsql</code> in a working database + according to the instructions in <a class="xref" href="sepgsql.html#SEPGSQL-INSTALLATION" title="F.37.2. Installation">Section F.37.2</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 <code class="filename">sepgsql-regtest</code> 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 + <code class="filename">sepgsql-regtest.te</code>, which is done using + <code class="command">make</code> 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. + (This Makefile is usually supplied by the + <code class="filename">selinux-policy-devel</code> or + <code class="filename">selinux-policy</code> RPM.) + Once built, install this policy package using the + <code class="command">semodule</code> command, which loads supplied policy packages + into the kernel. If the package is correctly installed, + <code class="literal"><code class="command">semodule</code> -l</code> should list <code class="literal">sepgsql-regtest</code> 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 <code class="literal">sepgsql_regression_test_mode</code>. + For security reasons, the rules in <code class="filename">sepgsql-regtest</code> + are not enabled by default; + the <code class="literal">sepgsql_regression_test_mode</code> parameter enables + the rules needed to launch the regression tests. + It can be turned on using the <code class="command">setsebool</code> 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 <code class="literal">unconfined_t</code> + domain: + </p><pre class="screen"> +$ id -Z +unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 +</pre><p> + See <a class="xref" href="sepgsql.html#SEPGSQL-RESOURCES" title="F.37.8. External Resources">Section F.37.8</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 + <code class="filename">sepgsql</code> module. + </p><p> + After completing the tests, it's recommended you disable + the <code class="literal">sepgsql_regression_test_mode</code> parameter: + </p><pre class="screen"> +$ sudo setsebool sepgsql_regression_test_mode off +</pre><p> + You might prefer to remove the <code class="filename">sepgsql-regtest</code> policy + entirely: + </p><pre class="screen"> +$ sudo semodule -r sepgsql-regtest +</pre></div><div class="sect2" id="SEPGSQL-PARAMETERS"><div class="titlepage"><div><div><h3 class="title">F.37.4. GUC Parameters</h3></div></div></div><div class="variablelist"><dl class="variablelist"><dt id="GUC-SEPGSQL-PERMISSIVE"><span class="term"> + <code class="varname">sepgsql.permissive</code> (<code class="type">boolean</code>) + <a id="id-1.11.7.46.8.2.1.1.3" class="indexterm"></a> + </span></dt><dd><p> + This parameter enables <code class="filename">sepgsql</code> to function + in permissive mode, regardless of the system setting. + The default is off. + This parameter can only be set in the <code class="filename">postgresql.conf</code> + file or on the server command line. + </p><p> + When this parameter is on, <code class="filename">sepgsql</code> 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 id="GUC-SEPGSQL-DEBUG-AUDIT"><span class="term"> + <code class="varname">sepgsql.debug_audit</code> (<code class="type">boolean</code>) + <a id="id-1.11.7.46.8.2.2.1.3" class="indexterm"></a> + </span></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" id="SEPGSQL-FEATURES"><div class="titlepage"><div><div><h3 class="title">F.37.5. Features</h3></div></div></div><div class="sect3" id="id-1.11.7.46.9.2"><div class="titlepage"><div><div><h4 class="title">F.37.5.1. Controlled Object Classes</h4></div></div></div><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 + <code class="literal">unlabeled_t</code>. + </p><p> + Currently, <code class="filename">sepgsql</code> allows security labels to be + assigned to schemas, tables, columns, sequences, views, and functions. + When <code class="filename">sepgsql</code> 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" id="id-1.11.7.46.9.3"><div class="titlepage"><div><div><h4 class="title">F.37.5.2. DML Permissions</h4></div></div></div><p> + For tables, <code class="literal">db_table:select</code>, <code class="literal">db_table:insert</code>, + <code class="literal">db_table:update</code> or <code class="literal">db_table:delete</code> are + checked for all the referenced target tables depending on the kind of + statement; in addition, <code class="literal">db_table:select</code> is also checked for + all the tables that contain columns referenced in the + <code class="literal">WHERE</code> or <code class="literal">RETURNING</code> clause, as a data source + for <code class="literal">UPDATE</code>, and so on. + </p><p> + Column-level permissions will also be checked for each referenced column. + <code class="literal">db_column:select</code> is checked on not only the columns being + read using <code class="literal">SELECT</code>, but those being referenced in other DML + statements; <code class="literal">db_column:update</code> or <code class="literal">db_column:insert</code> + will also be checked for columns being modified by <code class="literal">UPDATE</code> or + <code class="literal">INSERT</code>. + </p><p> + For example, consider: +</p><pre class="synopsis"> +UPDATE t1 SET x = 2, y = func1(y) WHERE z = 100; +</pre><p> + + Here, <code class="literal">db_column:update</code> will be checked for + <code class="literal">t1.x</code>, since it is being updated, + <code class="literal">db_column:{select update}</code> will be checked for + <code class="literal">t1.y</code>, since it is both updated and referenced, and + <code class="literal">db_column:select</code> will be checked for <code class="literal">t1.z</code>, since + it is only referenced. + <code class="literal">db_table:{select update}</code> will also be checked + at the table level. + </p><p> + For sequences, <code class="literal">db_sequence:get_value</code> is checked when we + reference a sequence object using <code class="literal">SELECT</code>; however, note that we + do not currently check permissions on execution of corresponding functions + such as <code class="literal">lastval()</code>. + </p><p> + For views, <code class="literal">db_view:expand</code> will be checked, then any other + required permissions will be checked on the objects being + expanded from the view, individually. + </p><p> + For functions, <code class="literal">db_procedure:{execute}</code> 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 + <code class="literal">db_procedure:{entrypoint}</code> permission to check whether it + can perform as entry point of trusted procedure. + </p><p> + In order to access any schema object, <code class="literal">db_schema:search</code> + 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 <code class="literal">USAGE</code> 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 + <code class="filename">sepgsql</code> is enabled. + </p></div><div class="sect3" id="id-1.11.7.46.9.4"><div class="titlepage"><div><div><h4 class="title">F.37.5.3. DDL Permissions</h4></div></div></div><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 <code class="literal">create</code> 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><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> + <a class="link" href="sql-createdatabase.html" title="CREATE DATABASE"><code class="command">CREATE DATABASE</code></a> additionally requires + <code class="literal">getattr</code> permission for the source or template database. + </p></li><li class="listitem"><p> + Creating a schema object additionally requires <code class="literal">add_name</code> + permission on the parent schema. + </p></li><li class="listitem"><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 class="listitem"><p> + Creating a function marked as <code class="literal">LEAKPROOF</code> additionally + requires <code class="literal">install</code> permission. (This permission is also + checked when <code class="literal">LEAKPROOF</code> is set for an existing function.) + </p></li></ul></div><p> + When <code class="literal">DROP</code> command is executed, <code class="literal">drop</code> will be + checked on the object being removed. Permissions will be also checked for + objects dropped indirectly via <code class="literal">CASCADE</code>. Deletion of objects + contained within a particular schema (tables, views, sequences and + procedures) additionally requires <code class="literal">remove_name</code> on the schema. + </p><p> + When <code class="literal">ALTER</code> command is executed, <code class="literal">setattr</code> 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><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> + Moving an object to a new schema additionally requires + <code class="literal">remove_name</code> permission on the old schema and + <code class="literal">add_name</code> permission on the new one. + </p></li><li class="listitem"><p> + Setting the <code class="literal">LEAKPROOF</code> attribute on a function requires + <code class="literal">install</code> permission. + </p></li><li class="listitem"><p> + Using <a class="link" href="sql-security-label.html" title="SECURITY LABEL"><code class="command">SECURITY LABEL</code></a> on an object additionally + requires <code class="literal">relabelfrom</code> permission for the object in + conjunction with its old security label and <code class="literal">relabelto</code> + 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 <code class="literal">setattr</code> should be checked here. + This is currently not done due to implementation restrictions.) + </p></li></ul></div></div><div class="sect3" id="id-1.11.7.46.9.5"><div class="titlepage"><div><div><h4 class="title">F.37.5.4. Trusted Procedures</h4></div></div></div><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 <code class="literal">customer.credit</code> + directly, but a trusted procedure <code class="literal">show_credit</code> allows the user + to print the credit card numbers of customers with some of the digits + masked out. + </p></div><div class="sect3" id="id-1.11.7.46.9.6"><div class="titlepage"><div><div><h4 class="title">F.37.5.5. Dynamic Domain Transitions</h4></div></div></div><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 <code class="literal">setcurrent</code> permission and also + <code class="literal">dyntransition</code> 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 <code class="literal">dyntransition</code> 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 <code class="literal">c1.c1023</code> to the smaller range <code class="literal">c1.c4</code>, 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 <code class="literal">sepgsql_setcon()</code> 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 <code class="literal">sepgsql_setcon()</code> with + <code class="literal">NULL</code> 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" id="id-1.11.7.46.9.7"><div class="titlepage"><div><div><h4 class="title">F.37.5.6. Miscellaneous</h4></div></div></div><p> + We reject the <a class="link" href="sql-load.html" title="LOAD"><code class="command">LOAD</code></a> command across the board, because + any module loaded could easily circumvent security policy enforcement. + </p></div></div><div class="sect2" id="SEPGSQL-FUNCTIONS"><div class="titlepage"><div><div><h3 class="title">F.37.6. Sepgsql Functions</h3></div></div></div><p> + <a class="xref" href="sepgsql.html#SEPGSQL-FUNCTIONS-TABLE" title="Table F.30. Sepgsql Functions">Table F.30</a> shows the available functions. + </p><div class="table" id="SEPGSQL-FUNCTIONS-TABLE"><p class="title"><strong>Table F.30. 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"> + Function + </p> + <p> + Description + </p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature"> + <code class="function">sepgsql_getcon</code> () + → <code class="returnvalue">text</code> + </p> + <p> + Returns the client domain, the current security label of the client. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <code class="function">sepgsql_setcon</code> ( <code class="type">text</code> ) + → <code class="returnvalue">boolean</code> + </p> + <p> + Switches the client domain of the current session to the new domain, + if allowed by the security policy. + It also accepts <code class="literal">NULL</code> input as a request to transition + to the client's original domain. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <code class="function">sepgsql_mcstrans_in</code> ( <code class="type">text</code> ) + → <code class="returnvalue">text</code> + </p> + <p> + Translates the given qualified MLS/MCS range into raw format if + the mcstrans daemon is running. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <code class="function">sepgsql_mcstrans_out</code> ( <code class="type">text</code> ) + → <code class="returnvalue">text</code> + </p> + <p> + Translates the given raw MLS/MCS range into qualified format if + the mcstrans daemon is running. + </p></td></tr><tr><td class="func_table_entry"><p class="func_signature"> + <code class="function">sepgsql_restorecon</code> ( <code class="type">text</code> ) + → <code class="returnvalue">boolean</code> + </p> + <p> + Sets up initial security labels for all objects within the + current database. The argument may be <code class="literal">NULL</code>, or the + name of a specfile to be used as alternative of the system default. + </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.37.7. Limitations</h3></div></div></div><div class="variablelist"><dl class="variablelist"><dt><span class="term">Data Definition Language (DDL) Permissions</span></dt><dd><p> + Due to implementation restrictions, some DDL operations do not + check permissions. + </p></dd><dt><span class="term">Data Control Language (DCL) Permissions</span></dt><dd><p> + Due to implementation restrictions, DCL operations do not check + permissions. + </p></dd><dt><span class="term">Row-level access control</span></dt><dd><p> + <span class="productname">PostgreSQL</span> supports row-level access, but + <code class="filename">sepgsql</code> does not. + </p></dd><dt><span class="term">Covert channels</span></dt><dd><p> + <code class="filename">sepgsql</code> 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" id="SEPGSQL-RESOURCES"><div class="titlepage"><div><div><h3 class="title">F.37.8. External Resources</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> + This wiki page provides a brief overview, security design, architecture, + administration and upcoming features. + </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> + This document provides a wide spectrum of knowledge to administer + <span class="productname">SELinux</span> on your systems. + It focuses primarily on Red Hat operating systems, but is not limited to them. + </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> + 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" id="SEPGSQL-AUTHOR"><div class="titlepage"><div><div><h3 class="title">F.37.9. Author</h3></div></div></div><p> + KaiGai Kohei <code class="email"><<a class="email" href="mailto:kaigai@ak.jp.nec.com">kaigai@ak.jp.nec.com</a>></code> + </p></div></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="seg.html" title="F.36. seg">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="contrib.html" title="Appendix F. Additional Supplied Modules">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="contrib-spi.html" title="F.38. spi">Next</a></td></tr><tr><td width="40%" align="left" valign="top">F.36. seg </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 14.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> F.38. spi</td></tr></table></div></body></html>
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