PostgreSQL 审计 - PostgreSQL Audit by Database or Role wide parameter
背景
本文基于PostgreSQL 9.2讲解.
审计的一个普遍用途就是记录用户在数据库中都干了些什么?
如果系统级的参数设置日志全记录下来当然也可以达到审计的目的, 但是这样做的话很多不需要的日志也会输出, 造成硬盘资源浪费甚至影响数据库性能. 所以精细化的审计非常有必要.
之前写过一篇关于PostgreSQL借助pg_log_userqueries插件实现用户或数据库级审计的文章.
http://blog.163.com/digoal@126/blog/static/1638770402012019112218804/
但是实际上, 使用数据库本身的配置就可以达到此目的. 主要用到PostgreSQL的以下两项配置.
1. PostgreSQL 的配置文件中对于日志的配置项What to Log中包含了默认的记录哪些日志的配置.
这些配置默认情况下是全局生效的, 不管是哪个用户连过来, 或者连到哪个数据库. 都是取的这些配置项.
2. PostgreSQL 提供了用户级以及数据库级的参数配置.
审计举例
假设当前的postgresql.conf LOG配置项如下 :
log_destination = 'csvlog'
logging_collector = on
log_directory = 'pg_log'
log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log'
log_file_mode = 0600
log_truncate_on_rotation = on
log_rotation_age = 1d
log_rotation_size = 10MB
log_connections = on
log_error_verbosity = verbose
log_timezone = 'PRC'
log_statement = 'none'
log_min_duration_statement = -1
1. 审计用户digoal连到数据库digoal 的所有SQL.
digoal=# alter role digoal in database digoal set log_statement='all';
查看当前的数据库+role级别的配置 :
digoal=> select a.*,b.datname,c.rolname from pg_db_role_setting a,pg_database b,pg_roles c where a.setdatabase=b.oid and a.setrole=c.oid;
setdatabase | setrole | setconfig | datname | rolname
-------------+---------+---------------------+---------+---------
3425937 | 3425936 | {log_statement=all} | digoal | digoal
(1 row)
测试 :
打开一个终端观察日志的输出
tail -f -n 1 postgresql-2013-03-20_000000.csv
使用digoal用户连接到digoal数据库, 并执行SQL
digoal=> \c digoal digoal
digoal=> select current_user;
current_user
--------------
digoal
(1 row)
select current_user被记录在日志中了
2013-03-20 08:43:25.109 CST,"digoal","digoal",2743,"[local]",5149061c.ab7,7,"idle",2013-03-20 08:43:08 CST,1/169,0,LOG,00000,"statement: select current_user;",,,,,,,,"exec_simple_query, postgres.c:888","psql"
digoal用户连接到其他数据库, 或者其他用户连接到digoal数据库的SQL不会被记录.
digoal=> \c digoal postgres
You are now connected to database "digoal" as user "postgres".
digoal=# select current_user;
current_user
--------------
postgres
(1 row)
digoal=# \c postgres digoal
You are now connected to database "postgres" as user "digoal".
postgres=> select current_user;
current_user
--------------
digoal
(1 row)
以上SQL在日志中无记录.
2. 审计用户digoal 的所有SQL.
postgres=> \c digoal postgres
You are now connected to database "digoal" as user "postgres".
digoal=# alter role digoal set log_statement='all';
ALTER ROLE
digoal=# select * from pg_roles where rolname='digoal';
rolname | rolsuper | rolinherit | rolcreaterole | rolcreatedb | rolcatupdate | rolcanlogin | rolreplication | rolconnlimit | rolpas
sword | rolvaliduntil | rolconfig | oid
---------+----------+------------+---------------+-------------+--------------+-------------+----------------+--------------+-------
------+---------------+---------------------+---------
digoal | f | t | f | f | f | t | f | -1 | ******
** | | {log_statement=all} | 3425936
(1 row)
测试, digoal用户连接到postgres数据库执行SQL
digoal=# \c postgres digoal
You are now connected to database "postgres" as user "digoal".
postgres=> select 'abc';
?column?
----------
abc
(1 row)
日志输出 :
2013-03-20 08:46:11.986 CST,"digoal","postgres",2807,"[local]",514906d1.af7,3,"idle",2013-03-20 08:46:09 CST,3/40,0,LOG,00000,"statement: select 'abc';",,,,,,,,"exec_simple_query, postgres.c:888","psql"
3. 审计任何用户连接到数据库digoal 的所有SQL.
postgres=# alter database digoal set log_statement='all';
ALTER DATABASE
postgres=# select a.*,b.datname from pg_db_role_setting a,pg_database b where a.setdatabase=b.oid;
setdatabase | setrole | setconfig | datname
-------------+---------+---------------------+---------
3425937 | 0 | {log_statement=all} | digoal
3425937 | 3425936 | {log_statement=all} | digoal
(2 rows)
setrole=0 表示所有用户.
测试, postgres用户连接到digoal数据库执行SQL
postgres=# \c digoal postgres
You are now connected to database "digoal" as user "postgres".
digoal=# select now();
now
-------------------------------
2013-03-20 08:49:27.761984+08
(1 row)
日志输出 :
2013-03-20 08:49:27.762 CST,"postgres","digoal",2879,"[local]",51490792.b3f,3,"idle",2013-03-20 08:49:22 CST,3/42,0,LOG,00000,"statement: select now();",,,,,,,,"exec_simple_query, postgres.c:888","psql"
清除以上审计配置
digoal=# alter role digoal set log_statement to default;
ALTER ROLE
digoal=# alter role digoal in database digoal reset log_statement;
ALTER ROLE
digoal=# alter database digoal reset log_statement;
ALTER DATABASE
digoal=# select * from pg_db_role_setting;
setdatabase | setrole | setconfig
-------------+---------+-----------
(0 rows)
推荐的日志配置
log_destination = 'csvlog'
logging_collector = on
log_directory = '/var/log/pg_log' # 这个目录最好不要和数据文件的目录放在一起, 目录需要给启动postgres的操作系统用户写权限.
log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log'
log_file_mode = 0600
log_truncate_on_rotation = on
log_rotation_age = 1d
log_rotation_size = 10MB
log_error_verbosity = verbose
其他
1. 以上审计的粒度可能还是太大, 只到了用户和数据库的层面.
并且, 仅仅审计到用户调用的SQL, 而不能审计到变化前后的数据, 例如用户执行一条UPDATE语句, 可能变更了整张表的数据, 但是使用log_statement只能记录下这条SQL, 而不是记录被变更前后的数据.
如果要对表或者表上面的数据进行审计的话, 需要用上触发器.
例如 :
http://blog.163.com/digoal@126/blog/static/163877040201252575529358/
如果不想将这些记录写在数据库中, 而是输出到日志的话 :
1. 触发器中使用RAISE WARNING ‘….’ 打印消息.
2. postgresql.conf 配置 log_min_messages = warning
这样的话’….’的消息就会打印到日志中.
具体的例子在另一篇文章中再详细介绍一下.
3. PostgreSQL 9.3还引入了事件触发器的功能, 也可以作为审计的外围工具之一.
感兴趣的朋友可以参考
http://blog.163.com/digoal@126/blog/static/16387704020132131361949/
注意事项
1. 超级用户可以修改这些配置项, 所以被审计的用户最好是普通用户. 否则用户连上来可以修改这些审计项.
2. 程序用的数据库账号和个人用的数据库账号分开, 对于程序用的数据库账号可以只审计DDL操作, 而对于个人使用的数据库账号, 建议审计所有的SQL.
3. 变量优先级(事务>会话>database/role>启动参数>配置文件)
某些全局变量可以动态修改，例如本文提到的log_statement。修改后reload之后，所有会话都会读到最新的变量。
而database和role级别的变量是本地变量，并且我们看到它的优先级高于全局参数变量，如果已有会话已经使用了database和role级别的变量，怎么改它呢? 必须要让这些会话自己通过 set的方式改会话级别的变量覆盖database or role level的变量值。或者让这些会话断开后重新建立。
所以使用database/role 级别的变量需要特别注意。
如果你哪天要不断开会话的方式，控制已有会话的这些参数，那就不建议使用database or role级别的参数，还是老老实实使用全局变量吧。
参考
1. PostgreSQL.conf
# - What to Log -
#debug_print_parse = off
#debug_print_rewritten = off
#debug_print_plan = off
#debug_pretty_print = on
#log_checkpoints = off
log_connections = on
#log_disconnections = off
#log_duration = off
log_error_verbosity = verbose # terse, default, or verbose messages
#log_hostname = off
#log_line_prefix = '' # special values:
# %a = application name
# %u = user name
# %d = database name
# %r = remote host and port
# %h = remote host
# %p = process ID
# %t = timestamp without milliseconds
# %m = timestamp with milliseconds
# %i = command tag
# %e = SQL state
# %c = session ID
# %l = session line number
# %s = session start timestamp
# %v = virtual transaction ID
# %x = transaction ID (0 if none)
# %q = stop here in non-session
# processes
# %% = '%'
# e.g. '<%u%%%d> '
#log_lock_waits = off # log lock waits >= deadlock_timeout
#log_statement = 'none' # none, ddl, mod, all
#log_temp_files = -1 # log temporary files equal or larger
# than the specified size in kilobytes;
# -1 disables, 0 logs all temp files
log_timezone = 'PRC'
2. http://www.postgresql.org/docs/9.2/static/sql-alterrole.html
3. http://www.postgresql.org/docs/9.2/static/sql-alterdatabase.html
4. http://www.postgresql.org/docs/9.2/static/sql-set.html
5. http://www.postgresql.org/docs/9.2/static/runtime-config.html
6. http://blog.163.com/digoal@126/blog/static/163877040201252575529358/
7. http://blog.163.com/digoal@126/blog/static/1638770402012019112218804/
8. http://blog.163.com/digoal@126/blog/static/16387704020132131361949/