郭勇的技术博客

前一段时间，论坛里总有朋友问到pam-mysql的安装问题。比较典型的有：
vsftp1.2+mysql4.1+pam_mysql0.5在RedHat AS4(32bit)下好像是有bug
还是mysql虚拟用户和vsftpd的登陆问题?

为了解答类似的问题，我动手试验了一下vsftpd+pam-mysql的配置过程，总结如下:

系统环境：

• RedHat AS 4
• MySQL 4.1.15
• pam_mysql-0.7pre3

说明一下，MySQL我是使用其官方网站的rpm包安装的，包括下面这4个：

1. MySQL-server-standard-4.1.15-0.rhel4.i386.rpm
2. MySQL-client-standard-4.1.15-0.rhel4.i386.rpm
3. MySQL-devel-standard-4.1.15-0.rhel4.i386.rpm
4. MySQL-shared-standard-4.1.15-0.rhel4.i386.rpm

vsftpd是RedHat自带的。

建立用于存放vsftpd虚拟用户的Schema的过程：
mysql> create database vsftpd;

mysql> use vsftpd;

mysql> create table users (
-> id int AUTO_INCREMENT NOT NULL,
-> name char(16) binary NOT NULL,
-> passwd char(48) binary NOT NULL,
-> primary key(id)
-> );

mysql> describe users;
+--------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+----------+------+-----+---------+----------------+
| id | int(11) | | PRI | NULL | auto_increment |
| name | char(16) | | | | |
| passwd | char(48) | | | | |
+--------+----------+------+-----+---------+----------------+

mysql> create table logs (msg varchar(255),
-> user char(16),
-> pid int,
-> host char(32),
-> rhost char(32),
-> logtime timestamp
-> );

mysql> describe logs;
+---------+--------------+------+-----+-------------------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+--------------+------+-----+-------------------+-------+
| msg | varchar(255) | YES | | NULL | |
| user | varchar(16) | YES | | NULL | |
| pid | int(11) | YES | | NULL | |
| host | varchar(32) | YES | | NULL | |
| rhost | varchar(32) | YES | | NULL | |
| logtime | timestamp | YES | | CURRENT_TIMESTAMP | |
+---------+--------------+------+-----+-------------------+-------+

这里，用户密码这个字段的长度是48。这是根据MySQL加密函数的返回值的长度确定的。关于PASSWORD函数返回值的长度，可以参考这个：

http://dev.mysql.com/doc/refman/4.1/en/password-hashing.html

mysql> select encrypt('foo');
+----------------+
| encrypt('foo') |
+----------------+
| 4Wwn2AXFYb.So |
+----------------+

mysql> select password('foo');
+-------------------------------------------+
| password('foo') |
+-------------------------------------------+
| *F3A2A51A9B0F2BE2468926B4132313728C250DBF |
+-------------------------------------------+

mysql> select md5('foo');
+----------------------------------+
| md5('foo') |
+----------------------------------+
| acbd18db4cc2f85cedef654fccc4a4d8 |
+----------------------------------+

编译安装pam_mysql
# ./configure --with-openssl
# make
# make install
加上--with-openssl可以避免make时报有关md5.h的编译错误

建立/etc/pam.d/vsftpd.mysql（因为只是想验证pam_mysql的安装过程，所以我不想覆盖原有的vsftpd这个文件)。注意只有两行，auth是一行，account是一行。

auth required /lib/security/pam_mysql.so user=root passwd=123456 host=localhost db=vsftpd table=users usercolumn=name passwdcolumn=passwd crypt=2 sqllog=1 logtable=logs logmsgcolumn=msg logusercolumn=user logpidcolumn=pid loghostcolumn=host logrhostcolumn=rhost logtimecolumn=logtime verbose=1
account required /lib/security/pam_mysql.so user=root passwd=123456 host=localhost db=vsftpd table=users usercolumn=name passwdcolumn=passwd crypt=2 sqllog=1 logtable=logs logmsgcolumn=msg logusercolumn=user logpidcolumn=pid loghostcolumn=host logrhostcolumn=rhost logtimecolumn=logtime verbose=1

注意这里pam_mysql.so的路径是/lib/security；指定了sqllog；加密方式是2，也就是用MySQL PASSWORD()函数；verbose=1，设置这个可以帮助调试，日志信息输出在/var/log/messages里。

建立/etc/vsftpd/vsftpd.mysql.conf（同样，不影响已有的vsftpd服务，执行service vsftpd restart时会启动两个vsftpd服务，端口不一样）
主要的设置如下：

pam_service_name=vsftpd.mysql
listen=YES
tcp_wrappers=YES
local_enable=YES
guest_enable=YES
guest_username=ftp
listen_port=2121

注意pam_service_name=vsftpd.mysql指定了使用刚才设置的pam_mysql。

插入用户信息：
mysql> insert into users (name,passwd) values('tom',password('foo'));
mysql> insert into users (name,passwd) values('jerry',password('bar'));
mysql> select * from users;
+----+-------+-------------------------------------------+
| id | name | passwd |
+----+-------+-------------------------------------------+
| 1 | tom | *F3A2A51A9B0F2BE2468926B4132313728C250DBF |
| 2 | jerry | *E8D46CE25265E545D225A8A6F1BAF642FEBEE5CB |
+----+-------+-------------------------------------------+

启动vsftpd服务，测试配置：
# ftp localhost 2121

登录失败，检查/var/log/messages，发现：
# tail -f /var/log/messages
Nov 29 14:52:04 javadev vsftpd[17683]: PAM unable to dlopen(/lib/security/pam_mysql.so)
Nov 29 14:52:04 javadev vsftpd[17683]: PAM [dlerror: /lib/security/pam_mysql.so: cannot open shared object file: No such file or directory]
Nov 29 14:52:04 javadev vsftpd[17683]: PAM adding faulty module: /lib/security/pam_mysql.so

看来是没找到pam_mysql.so，怎么会呢？
用find（也可以用locate，不过得先updatedb一下，慢）找了一下，原来make install的时候默认安装在/usr/local/lib下。修改/etc/pam.d/vsftpd.mysql
auth required /usr/lib/security/pam_mysql.so user=root passwd=123456 host=localhost db=vsftpd table=users usercolumn=name passwdcolumn=passwd crypt=2 sqllog=1 logtable=logs logmsgcolumn=msg logusercolumn=user logpidcolumn=pid loghostcolumn=host logrhostcolumn=rhost logtimecolumn=logtime verbose=1
account required /usr/lib/security/pam_mysql.so user=root passwd=123456 host=localhost db=vsftpd table=users usercolumn=name passwdcolumn=passwd crypt=2 sqllog=1 logtable=logs logmsgcolumn=msg logusercolumn=user logpidcolumn=pid loghostcolumn=host logrhostcolumn=rhost logtimecolumn=logtime verbose=1

在登录，成功！换用其他加密方式，也都可以。

然后试验pam_mysql v0.7新加的config_file配置选项。这个选项用来指定一个配置文件，可以把所有pam_mysql的配置放在这个文件中。这样的话，/etc/pam.d/vsftpd.mysql的内容变成这样：

auth required /usr/lib/security/pam_mysql.so config_file=/etc/security/pam_mysql.conf
account required /usr/lib/security/pam_mysql.so config_file=/etc/security/pam_mysql.conf

清爽了许多吧，

/etc/security/pam_mysql.conf的内容：

users.host=localhost
users.database=vsftpd
users.db_user=root
users.db_passwd=123456
users.table=users
users.user_column=name
users.password_column=passwd
users.password_crypt=3
verbose=1
log.enabled=1
log.table=logs
log.message_column=msg
log.pid_column=pid
log.user_column=user
log.host_column=host
log.rhost_column=rhost
log.time_column=logtime

改好这些以后，用之前建好的虚拟用户登录，居然不行！而且这次/var/log/messages里没有任何错误消息。ls -ltr /var/log 发现secure这个文件最新，试着打开，果然发现了pam_mysql的调试信息：

Dec 26 16:18:37 javadev vsftpd[6175]: pam_mysql - option verbose is set to "1"
Dec 26 16:18:37 javadev vsftpd[6175]: pam_mysql - option log.enabled is set to "1 "
Dec 26 16:18:37 javadev vsftpd[6175]: pam_mysql - option log.table is set to "logs"
Dec 26 16:18:37 javadev vsftpd[6175]: pam_mysql - option log.message_column is set to "msg"
Dec 26 16:18:37 javadev vsftpd[6175]: pam_mysql - option log.pid_column is set to "pid"
Dec 26 16:18:37 javadev vsftpd[6175]: pam_mysql - option log.user_column is set to "user"
Dec 26 16:18:37 javadev vsftpd[6175]: pam_mysql - option log.host_column is set to "host"
Dec 26 16:18:37 javadev vsftpd[6175]: pam_mysql - option log.rhost_column is set to "rhost"
Dec 26 16:18:37 javadev vsftpd[6175]: pam_mysql - option log.time_column is set to "logtime"
Dec 26 16:18:37 javadev vsftpd[6175]: pam_mysql - pam_sm_authenticate() called.
Dec 26 16:18:37 javadev vsftpd[6175]: pam_mysql - pam_mysql_open_db() called.
Dec 26 16:18:42 javadev vsftpd[6175]: pam_mysql - MySQL error (Unknown MySQL server host 'localhost ' (3))
Dec 26 16:18:42 javadev vsftpd[6175]: pam_mysql - pam_mysql_open_db() returning 5.
Dec 26 16:18:42 javadev vsftpd[6175]: pam_mysql - pam_sm_authenticate() returning 9.
Dec 26 16:18:42 javadev vsftpd[6175]: pam_mysql - pam_mysql_release_ctx() called.
Dec 26 16:18:42 javadev vsftpd[6175]: pam_mysql - pam_mysql_destroy_ctx() called.
Dec 26 16:18:42 javadev vsftpd[6175]: pam_mysql - pam_mysql_close_db() called.

仔细检查，发现原因在这里：

pam_mysql - MySQL error (Unknown MySQL server host 'localhost ' (3))

原来配置文件里users.host=localhost 这行行尾多了一个空格！郁闷！修改以后就可以登录了。

最后，我在论坛里回复时说过不能用password这种方式，原因是

2 (or "mysql") = Use MySQL PASSWORD() function. It is possible
that the encryption function used by PAM-MySQL
is different from that of the MySQL server, as
PAM-MySQL uses the function defined in MySQL's
C-client API instead of using PASSWORD() SQL function
in the query.

事实证明我说错了。

还有，两个log可以帮助分析故障（当然可能仅在RedHat下），/var/log/messages和/var/log/secure