[MDEV-20756] Default user name for libmysqlclient is empty - Jira

Geoff Montee (Inactive) created issue - 2019-10-05 01:11

Geoff Montee (Inactive) made changes - 2019-10-05 01:11

Field	Original Value	New Value
Link		This issue relates to ~~CONC-441~~ [ ~~CONC-441~~ ]

Geoff Montee (Inactive) made changes - 2019-10-05 06:03

Description

This bug is similar to ~~CONC-441~~, but this bug applies to tools that use the built-in libmysqlclient, while the other bug applies to clients that use C/C.

For example, {{mariabackup}} seems to use libmysqlclient, according to {{gdb}} output, which shows that it calls the versions of {{mysql_real_connect()}} and {{run_plugin_auth()}} defined in {{sql-common/client.c}}:

{noformat}
(gdb) where
#0 0x00007fb1619aef70 in __read_nocancel () from /lib64/libc.so.6
#1 0x00007fb16193bb14 in __GI__IO_file_underflow () from /lib64/libc.so.6
#2 0x00007fb16193cce2 in __GI__IO_default_uflow () from /lib64/libc.so.6
#3 0x00007fb16193754e in getc () from /lib64/libc.so.6
#4 0x00007fb15e94afe0 in get_password (length=1023, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., file=0x7fb161c87640 <_IO_2_1_stdin_>) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:68
#5 get_tty_password (prompt=prompt@entry=0x7fb15e94b0d0 "", buffer=buffer@entry=0x7ffed185a030 '\377' <repeats 200 times>..., length=length@entry=1023) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:162
#6 0x00007fb15e94aeac in auth_dialog_native_prompt (mysql=<optimized out>, type=2, prompt=<optimized out>, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., buffer_len=1024)
    at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:106
#7 0x00007fb15e94ad1d in auth_dialog_open (vio=0x7ffed185a490, mysql=0x5629645279d8) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:159
#8 0x000056296166f10e in run_plugin_auth (mysql=mysql@entry=0x5629645279d8, data=<optimized out>, data@entry=0x56296452c13a "_password", data_len=<optimized out>, data_len@entry=21,
    data_plugin=data_plugin@entry=0x56296452c14f "\f_client_name\blibmysql\004_pid\004\065\067\070\065\017_client_version\a10.3.18\f_server_host\tlocalhost\t_platform\006x86_64", db=db@entry=0x0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:2767
#9 0x00005629616710db in mysql_real_connect (mysql=0x5629645279d8, host=<optimized out>, user=<optimized out>, passwd=<optimized out>, db=<optimized out>, port=<optimized out>, unix_socket=<optimized out>, client_flag=0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:3363
#10 0x0000562961656766 in xb_mysql_connect () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/backup_mysql.cc:148
#11 0x0000562961641c66 in xb_init () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:5830
#12 0x00005629616423f4 in main_low (argv=0x562964526d90) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6294
#13 0x00005629616218e5 in main (argc=9, argv=0x7ffed185bda0) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6137
{noformat}

For command-line tools, if no user name is provided, then the default behavior is supposed to be that the client will use the name of the current Unix user.

However, at the moment, the wrong user name is used by default in some cases.

From the MySQL documentation:

{quote}
On Unix, most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only.
{quote}

https://dev.mysql.com/doc/refman/5.7/en/user-names.html

And from the MariaDB documentation:

{quote}
-u, --user=name User for login, if not current user.
{quote}

https://mariadb.com/kb/en/library/mysql-command-line-client/

libmysqlclient even has a useful function called {{read_user_name()}} that is intended to handle this exact case:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/libmysqld/libmysql.c#L423

It is called in {{send_client_reply_packet()}}:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql-common/client.c#L2426

However, it appears that this function may be returning the wrong value.

We can reproduce this by executing a client and not providing a user name.

First, let's check which user account we are:

{noformat}
$ whoami
mysql
$ printenv USER
mysql
2$ printenv LOGNAME
mysql
$ printenv LOGIN
$ id
uid=997(mysql) gid=994(mysql) groups=994(mysql),1005(shadow)
{noformat}

And then let's run {{mariabackup}} without providing a user name:

{noformat}
$ mkdir /tmp/backup
$ mariabackup --backup --target-dir=/tmp/backup
[00] 2019-10-05 01:04:56 Connecting to MySQL server host: localhost, user: not set, password: not set, port: not set, socket: not set
Password:
[00] 2019-10-05 01:05:02 Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

Authentication will fail, because the user name is wrong.

The error message sent by the server references this incorrect empty user name:

{noformat}
Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

And the error log on the server shows the same thing:

{noformat}
2019-10-05 1:05:02 32 [Warning] Access denied for user ''@'localhost' (using password: NO)
{noformat}

This bug is similar to ~~CONC-441~~, but this bug applies to tools that use the built-in libmysqlclient, while the other bug applies to clients that use C/C.

For example, {{mariabackup}} seems to use libmysqlclient, according to {{gdb}} output, which shows that it calls the versions of {{mysql_real_connect()}} and {{run_plugin_auth()}} defined in {{sql-common/client.c}}:

{noformat}
(gdb) where
#0 0x00007fb1619aef70 in __read_nocancel () from /lib64/libc.so.6
#1 0x00007fb16193bb14 in __GI__IO_file_underflow () from /lib64/libc.so.6
#2 0x00007fb16193cce2 in __GI__IO_default_uflow () from /lib64/libc.so.6
#3 0x00007fb16193754e in getc () from /lib64/libc.so.6
#4 0x00007fb15e94afe0 in get_password (length=1023, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., file=0x7fb161c87640 <_IO_2_1_stdin_>) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:68
#5 get_tty_password (prompt=prompt@entry=0x7fb15e94b0d0 "", buffer=buffer@entry=0x7ffed185a030 '\377' <repeats 200 times>..., length=length@entry=1023) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:162
#6 0x00007fb15e94aeac in auth_dialog_native_prompt (mysql=<optimized out>, type=2, prompt=<optimized out>, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., buffer_len=1024)
    at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:106
#7 0x00007fb15e94ad1d in auth_dialog_open (vio=0x7ffed185a490, mysql=0x5629645279d8) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:159
#8 0x000056296166f10e in run_plugin_auth (mysql=mysql@entry=0x5629645279d8, data=<optimized out>, data@entry=0x56296452c13a "_password", data_len=<optimized out>, data_len@entry=21,
    data_plugin=data_plugin@entry=0x56296452c14f "\f_client_name\blibmysql\004_pid\004\065\067\070\065\017_client_version\a10.3.18\f_server_host\tlocalhost\t_platform\006x86_64", db=db@entry=0x0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:2767
#9 0x00005629616710db in mysql_real_connect (mysql=0x5629645279d8, host=<optimized out>, user=<optimized out>, passwd=<optimized out>, db=<optimized out>, port=<optimized out>, unix_socket=<optimized out>, client_flag=0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:3363
#10 0x0000562961656766 in xb_mysql_connect () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/backup_mysql.cc:148
#11 0x0000562961641c66 in xb_init () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:5830
#12 0x00005629616423f4 in main_low (argv=0x562964526d90) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6294
#13 0x00005629616218e5 in main (argc=9, argv=0x7ffed185bda0) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6137
{noformat}

For command-line tools, if no user name is provided, then the default behavior is supposed to be that the client will use the name of the current Unix user.

However, at the moment, the wrong user name is used by default in some cases.

From the MySQL documentation:

{quote}
On Unix, most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only.
{quote}

https://dev.mysql.com/doc/refman/5.7/en/user-names.html

And from the MariaDB documentation:

{quote}
-u, --user=name User for login, if not current user.
{quote}

https://mariadb.com/kb/en/library/mysql-command-line-client/

libmysqlclient even has a useful function called {{read_user_name()}} that is intended to handle this exact case:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/libmysqld/libmysql.c#L423

It is called in {{send_client_reply_packet()}}:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql-common/client.c#L2426

However, it appears that this function may be returning the wrong value.

We can reproduce this by executing a client and not providing a user name.

First, let's check which user account we are:

{noformat}
$ whoami
mysql
$ printenv USER
mysql
$ printenv LOGNAME
mysql
$ printenv LOGIN
$ id
uid=997(mysql) gid=994(mysql) groups=994(mysql),1005(shadow)
{noformat}

And then let's run {{mariabackup}} without providing a user name:

{noformat}
$ mkdir /tmp/backup
$ mariabackup --backup --target-dir=/tmp/backup
[00] 2019-10-05 01:04:56 Connecting to MySQL server host: localhost, user: not set, password: not set, port: not set, socket: not set
Password:
[00] 2019-10-05 01:05:02 Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

Authentication will fail, because the user name is wrong.

The error message sent by the server references this incorrect empty user name:

{noformat}
Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

And the error log on the server shows the same thing:

{noformat}
2019-10-05 1:05:02 32 [Warning] Access denied for user ''@'localhost' (using password: NO)
{noformat}

Sergei Golubchik made changes - 2019-10-06 11:25

Assignee

Sergei Golubchik [ serg ]

Alexey Botchkov [ holyfoot ]

Geoff Montee (Inactive) made changes - 2019-10-11 01:19

Description

This bug is similar to ~~CONC-441~~, but this bug applies to tools that use the built-in libmysqlclient, while the other bug applies to clients that use C/C.

For example, {{mariabackup}} seems to use libmysqlclient, according to {{gdb}} output, which shows that it calls the versions of {{mysql_real_connect()}} and {{run_plugin_auth()}} defined in {{sql-common/client.c}}:

{noformat}
(gdb) where
#0 0x00007fb1619aef70 in __read_nocancel () from /lib64/libc.so.6
#1 0x00007fb16193bb14 in __GI__IO_file_underflow () from /lib64/libc.so.6
#2 0x00007fb16193cce2 in __GI__IO_default_uflow () from /lib64/libc.so.6
#3 0x00007fb16193754e in getc () from /lib64/libc.so.6
#4 0x00007fb15e94afe0 in get_password (length=1023, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., file=0x7fb161c87640 <_IO_2_1_stdin_>) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:68
#5 get_tty_password (prompt=prompt@entry=0x7fb15e94b0d0 "", buffer=buffer@entry=0x7ffed185a030 '\377' <repeats 200 times>..., length=length@entry=1023) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:162
#6 0x00007fb15e94aeac in auth_dialog_native_prompt (mysql=<optimized out>, type=2, prompt=<optimized out>, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., buffer_len=1024)
    at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:106
#7 0x00007fb15e94ad1d in auth_dialog_open (vio=0x7ffed185a490, mysql=0x5629645279d8) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:159
#8 0x000056296166f10e in run_plugin_auth (mysql=mysql@entry=0x5629645279d8, data=<optimized out>, data@entry=0x56296452c13a "_password", data_len=<optimized out>, data_len@entry=21,
    data_plugin=data_plugin@entry=0x56296452c14f "\f_client_name\blibmysql\004_pid\004\065\067\070\065\017_client_version\a10.3.18\f_server_host\tlocalhost\t_platform\006x86_64", db=db@entry=0x0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:2767
#9 0x00005629616710db in mysql_real_connect (mysql=0x5629645279d8, host=<optimized out>, user=<optimized out>, passwd=<optimized out>, db=<optimized out>, port=<optimized out>, unix_socket=<optimized out>, client_flag=0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:3363
#10 0x0000562961656766 in xb_mysql_connect () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/backup_mysql.cc:148
#11 0x0000562961641c66 in xb_init () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:5830
#12 0x00005629616423f4 in main_low (argv=0x562964526d90) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6294
#13 0x00005629616218e5 in main (argc=9, argv=0x7ffed185bda0) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6137
{noformat}

For command-line tools, if no user name is provided, then the default behavior is supposed to be that the client will use the name of the current Unix user.

However, at the moment, the wrong user name is used by default in some cases.

From the MySQL documentation:

{quote}
On Unix, most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only.
{quote}

https://dev.mysql.com/doc/refman/5.7/en/user-names.html

And from the MariaDB documentation:

{quote}
-u, --user=name User for login, if not current user.
{quote}

https://mariadb.com/kb/en/library/mysql-command-line-client/

libmysqlclient even has a useful function called {{read_user_name()}} that is intended to handle this exact case:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/libmysqld/libmysql.c#L423

It is called in {{send_client_reply_packet()}}:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql-common/client.c#L2426

However, it appears that this function may be returning the wrong value.

We can reproduce this by executing a client and not providing a user name.

First, let's check which user account we are:

{noformat}
$ whoami
mysql
$ printenv USER
mysql
$ printenv LOGNAME
mysql
$ printenv LOGIN
$ id
uid=997(mysql) gid=994(mysql) groups=994(mysql),1005(shadow)
{noformat}

And then let's run {{mariabackup}} without providing a user name:

{noformat}
$ mkdir /tmp/backup
$ mariabackup --backup --target-dir=/tmp/backup
[00] 2019-10-05 01:04:56 Connecting to MySQL server host: localhost, user: not set, password: not set, port: not set, socket: not set
Password:
[00] 2019-10-05 01:05:02 Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

Authentication will fail, because the user name is wrong.

The error message sent by the server references this incorrect empty user name:

{noformat}
Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

And the error log on the server shows the same thing:

{noformat}
2019-10-05 1:05:02 32 [Warning] Access denied for user ''@'localhost' (using password: NO)
{noformat}

This bug is similar to ~~CONC-441~~, but this bug applies to tools that use the built-in libmysqlclient, while the other bug applies to clients that use C/C.

For example, {{mariabackup}} seems to use libmysqlclient, according to {{gdb}} output, which shows that it calls the versions of {{mysql_real_connect()}} and {{run_plugin_auth()}} defined in {{sql-common/client.c}}:

{noformat}
(gdb) where
#0 0x00007fb1619aef70 in __read_nocancel () from /lib64/libc.so.6
#1 0x00007fb16193bb14 in __GI__IO_file_underflow () from /lib64/libc.so.6
#2 0x00007fb16193cce2 in __GI__IO_default_uflow () from /lib64/libc.so.6
#3 0x00007fb16193754e in getc () from /lib64/libc.so.6
#4 0x00007fb15e94afe0 in get_password (length=1023, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., file=0x7fb161c87640 <_IO_2_1_stdin_>) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:68
#5 get_tty_password (prompt=prompt@entry=0x7fb15e94b0d0 "", buffer=buffer@entry=0x7ffed185a030 '\377' <repeats 200 times>..., length=length@entry=1023) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:162
#6 0x00007fb15e94aeac in auth_dialog_native_prompt (mysql=<optimized out>, type=2, prompt=<optimized out>, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., buffer_len=1024)
    at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:106
#7 0x00007fb15e94ad1d in auth_dialog_open (vio=0x7ffed185a490, mysql=0x5629645279d8) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:159
#8 0x000056296166f10e in run_plugin_auth (mysql=mysql@entry=0x5629645279d8, data=<optimized out>, data@entry=0x56296452c13a "_password", data_len=<optimized out>, data_len@entry=21,
    data_plugin=data_plugin@entry=0x56296452c14f "\f_client_name\blibmysql\004_pid\004\065\067\070\065\017_client_version\a10.3.18\f_server_host\tlocalhost\t_platform\006x86_64", db=db@entry=0x0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:2767
#9 0x00005629616710db in mysql_real_connect (mysql=0x5629645279d8, host=<optimized out>, user=<optimized out>, passwd=<optimized out>, db=<optimized out>, port=<optimized out>, unix_socket=<optimized out>, client_flag=0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:3363
#10 0x0000562961656766 in xb_mysql_connect () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/backup_mysql.cc:148
#11 0x0000562961641c66 in xb_init () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:5830
#12 0x00005629616423f4 in main_low (argv=0x562964526d90) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6294
#13 0x00005629616218e5 in main (argc=9, argv=0x7ffed185bda0) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6137
{noformat}

For command-line tools, if no user name is provided, then the default behavior is supposed to be that the client will use the name of the current Unix user.

From the MySQL documentation:

{quote}
On Unix, most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only.
{quote}

https://dev.mysql.com/doc/refman/5.7/en/user-names.html

And from the MariaDB documentation:

{quote}
-u, --user=name User for login, if not current user.
{quote}

https://mariadb.com/kb/en/library/mysql-command-line-client/

However, at the moment, the wrong user name is used by default if the login user is different from the effective user.

libmysqlclient calls {{read_user_name()}} to get the current user:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/libmysqld/libmysql.c#L423

It is called in {{send_client_reply_packet()}}:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql-common/client.c#L2426

The {{read_user_name()}} function gets the user name by checking the following items in the following order:

* If {{geteuid()}} returns {{0}}, then {{root}} is used.
* If {{getlogin()}} is not {{NULL}}, then its return value is used.
* If {{getpwuid(geteuid())}} is not {{NULL}}, then its return value is used.
* If the {{USER}} environment variable is set, then its assigned value is used.
* If the {{LOGNAME}} environment variable is set, then its assigned value is used.
* If the {{LOGIN}} environment variable is set, then its assigned value is used.

This order can cause unexpected results in some cases.

For example, let's say that we change users by doing something like this:

{noformat}
$ whoami
ec2-user
$ sudo -u mysql bash
$ whoami
mysql
$ printenv USER
mysql
$ printenv LOGNAME
mysql
$ printenv LOGIN
$ id
uid=997(mysql) gid=994(mysql) groups=994(mysql),1005(shadow)
$ cat /proc/self/loginuid
1000
$ id 1000
uid=1000(ec2-user) gid=1000(ec2-user) groups=1000(ec2-user),4(adm),10(wheel),190(systemd-journal)
{noformat}

In this case, our effective user is {{mysql}}, but the login user is still {{ec2-user}}.

Let's run {{mariabackup}} without providing a user name:

{noformat}
$ mkdir /tmp/backup
$ mariabackup --backup --target-dir=/tmp/backup
[00] 2019-10-05 01:04:56 Connecting to MySQL server host: localhost, user: not set, password: not set, port: not set, socket: not set
Password:
[00] 2019-10-05 01:05:02 Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

Authentication will fail, because the user name is wrong.

The error message sent by the server references an empty user name:

{noformat}
Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

And the error log on the server shows the same thing:

{noformat}
2019-10-05 1:05:02 32 [Warning] Access denied for user ''@'localhost' (using password: NO)
{noformat}

Geoff Montee (Inactive) made changes - 2019-10-11 01:22

Summary

Default user name for libmysqlclient is wrong

Default user name for libmysqlclient is wrong if login user is different from effective user

Geoff Montee (Inactive) made changes - 2019-10-11 01:49

Description

This bug is similar to ~~CONC-441~~, but this bug applies to tools that use the built-in libmysqlclient, while the other bug applies to clients that use C/C.

For example, {{mariabackup}} seems to use libmysqlclient, according to {{gdb}} output, which shows that it calls the versions of {{mysql_real_connect()}} and {{run_plugin_auth()}} defined in {{sql-common/client.c}}:

{noformat}
(gdb) where
#0 0x00007fb1619aef70 in __read_nocancel () from /lib64/libc.so.6
#1 0x00007fb16193bb14 in __GI__IO_file_underflow () from /lib64/libc.so.6
#2 0x00007fb16193cce2 in __GI__IO_default_uflow () from /lib64/libc.so.6
#3 0x00007fb16193754e in getc () from /lib64/libc.so.6
#4 0x00007fb15e94afe0 in get_password (length=1023, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., file=0x7fb161c87640 <_IO_2_1_stdin_>) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:68
#5 get_tty_password (prompt=prompt@entry=0x7fb15e94b0d0 "", buffer=buffer@entry=0x7ffed185a030 '\377' <repeats 200 times>..., length=length@entry=1023) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:162
#6 0x00007fb15e94aeac in auth_dialog_native_prompt (mysql=<optimized out>, type=2, prompt=<optimized out>, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., buffer_len=1024)
    at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:106
#7 0x00007fb15e94ad1d in auth_dialog_open (vio=0x7ffed185a490, mysql=0x5629645279d8) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:159
#8 0x000056296166f10e in run_plugin_auth (mysql=mysql@entry=0x5629645279d8, data=<optimized out>, data@entry=0x56296452c13a "_password", data_len=<optimized out>, data_len@entry=21,
    data_plugin=data_plugin@entry=0x56296452c14f "\f_client_name\blibmysql\004_pid\004\065\067\070\065\017_client_version\a10.3.18\f_server_host\tlocalhost\t_platform\006x86_64", db=db@entry=0x0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:2767
#9 0x00005629616710db in mysql_real_connect (mysql=0x5629645279d8, host=<optimized out>, user=<optimized out>, passwd=<optimized out>, db=<optimized out>, port=<optimized out>, unix_socket=<optimized out>, client_flag=0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:3363
#10 0x0000562961656766 in xb_mysql_connect () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/backup_mysql.cc:148
#11 0x0000562961641c66 in xb_init () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:5830
#12 0x00005629616423f4 in main_low (argv=0x562964526d90) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6294
#13 0x00005629616218e5 in main (argc=9, argv=0x7ffed185bda0) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6137
{noformat}

For command-line tools, if no user name is provided, then the default behavior is supposed to be that the client will use the name of the current Unix user.

From the MySQL documentation:

{quote}
On Unix, most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only.
{quote}

https://dev.mysql.com/doc/refman/5.7/en/user-names.html

And from the MariaDB documentation:

{quote}
-u, --user=name User for login, if not current user.
{quote}

https://mariadb.com/kb/en/library/mysql-command-line-client/

However, at the moment, the wrong user name is used by default if the login user is different from the effective user.

libmysqlclient calls {{read_user_name()}} to get the current user:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/libmysqld/libmysql.c#L423

It is called in {{send_client_reply_packet()}}:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql-common/client.c#L2426

The {{read_user_name()}} function gets the user name by checking the following items in the following order:

* If {{geteuid()}} returns {{0}}, then {{root}} is used.
* If {{getlogin()}} is not {{NULL}}, then its return value is used.
* If {{getpwuid(geteuid())}} is not {{NULL}}, then its return value is used.
* If the {{USER}} environment variable is set, then its assigned value is used.
* If the {{LOGNAME}} environment variable is set, then its assigned value is used.
* If the {{LOGIN}} environment variable is set, then its assigned value is used.

This order can cause unexpected results in some cases.

For example, let's say that we change users by doing something like this:

{noformat}
$ whoami
ec2-user
$ sudo -u mysql bash
$ whoami
mysql
$ printenv USER
mysql
$ printenv LOGNAME
mysql
$ printenv LOGIN
$ id
uid=997(mysql) gid=994(mysql) groups=994(mysql),1005(shadow)
$ cat /proc/self/loginuid
1000
$ id 1000
uid=1000(ec2-user) gid=1000(ec2-user) groups=1000(ec2-user),4(adm),10(wheel),190(systemd-journal)
{noformat}

In this case, our effective user is {{mysql}}, but the login user is still {{ec2-user}}.

Let's run {{mariabackup}} without providing a user name:

{noformat}
$ mkdir /tmp/backup
$ mariabackup --backup --target-dir=/tmp/backup
[00] 2019-10-05 01:04:56 Connecting to MySQL server host: localhost, user: not set, password: not set, port: not set, socket: not set
Password:
[00] 2019-10-05 01:05:02 Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

Authentication will fail, because the user name is wrong.

The error message sent by the server references an empty user name:

{noformat}
Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

And the error log on the server shows the same thing:

{noformat}
2019-10-05 1:05:02 32 [Warning] Access denied for user ''@'localhost' (using password: NO)
{noformat}

This bug is similar to ~~CONC-441~~, but this bug applies to tools that use the built-in libmysqlclient, while the other bug applies to clients that use C/C.

For command-line tools, if no user name is provided, then the default behavior is supposed to be that the client will use the name of the current Unix user.

From the MySQL documentation:

{quote}
On Unix, most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only.
{quote}

https://dev.mysql.com/doc/refman/5.7/en/user-names.html

And from the MariaDB documentation:

{quote}
-u, --user=name User for login, if not current user.
{quote}

https://mariadb.com/kb/en/library/mysql-command-line-client/

However, at the moment, the wrong user name is used by default if the login user is different from the effective user.

h2. How the Default User Name is Determined

libmysqlclient determines the default user name by calling {{read_user_name()}} to get the current user:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/libmysqld/libmysql.c#L423

It is called in {{send_client_reply_packet()}}:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql-common/client.c#L2426

The {{read_user_name()}} function gets the user name by checking the following items in the following order:

* If {{geteuid()}} returns {{0}}, then {{root}} is used.
* If {{getlogin()}} is not {{NULL}}, then its return value is used.
* If {{getpwuid(geteuid())}} is not {{NULL}}, then its return value is used.
* If the {{USER}} environment variable is set, then its assigned value is used.
* If the {{LOGNAME}} environment variable is set, then its assigned value is used.
* If the {{LOGIN}} environment variable is set, then its assigned value is used.

This order can cause unexpected results in some cases.

h2. How to Reproduce

For example, let's say that we change users by doing something like this:

{noformat}
$ whoami
ec2-user
$ sudo -u mysql bash
$ whoami
mysql
$ printenv USER
mysql
$ printenv LOGNAME
mysql
$ printenv LOGIN
$ id
uid=997(mysql) gid=994(mysql) groups=994(mysql),1005(shadow)
$ cat /proc/self/loginuid
1000
$ id 1000
uid=1000(ec2-user) gid=1000(ec2-user) groups=1000(ec2-user),4(adm),10(wheel),190(systemd-journal)
{noformat}

In this case, our effective user is {{mysql}}, but the login user is still {{ec2-user}}.

{{mariabackup}} still seems to use libmysqlclient, according to {{gdb}} output, which shows that it calls the versions of {{mysql_real_connect()}} and {{run_plugin_auth()}} defined in {{sql-common/client.c}}:

{noformat}
(gdb) where
#0 0x00007fb1619aef70 in __read_nocancel () from /lib64/libc.so.6
#1 0x00007fb16193bb14 in __GI__IO_file_underflow () from /lib64/libc.so.6
#2 0x00007fb16193cce2 in __GI__IO_default_uflow () from /lib64/libc.so.6
#3 0x00007fb16193754e in getc () from /lib64/libc.so.6
#4 0x00007fb15e94afe0 in get_password (length=1023, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., file=0x7fb161c87640 <_IO_2_1_stdin_>) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:68
#5 get_tty_password (prompt=prompt@entry=0x7fb15e94b0d0 "", buffer=buffer@entry=0x7ffed185a030 '\377' <repeats 200 times>..., length=length@entry=1023) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:162
#6 0x00007fb15e94aeac in auth_dialog_native_prompt (mysql=<optimized out>, type=2, prompt=<optimized out>, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., buffer_len=1024)
    at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:106
#7 0x00007fb15e94ad1d in auth_dialog_open (vio=0x7ffed185a490, mysql=0x5629645279d8) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:159
#8 0x000056296166f10e in run_plugin_auth (mysql=mysql@entry=0x5629645279d8, data=<optimized out>, data@entry=0x56296452c13a "_password", data_len=<optimized out>, data_len@entry=21,
    data_plugin=data_plugin@entry=0x56296452c14f "\f_client_name\blibmysql\004_pid\004\065\067\070\065\017_client_version\a10.3.18\f_server_host\tlocalhost\t_platform\006x86_64", db=db@entry=0x0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:2767
#9 0x00005629616710db in mysql_real_connect (mysql=0x5629645279d8, host=<optimized out>, user=<optimized out>, passwd=<optimized out>, db=<optimized out>, port=<optimized out>, unix_socket=<optimized out>, client_flag=0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:3363
#10 0x0000562961656766 in xb_mysql_connect () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/backup_mysql.cc:148
#11 0x0000562961641c66 in xb_init () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:5830
#12 0x00005629616423f4 in main_low (argv=0x562964526d90) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6294
#13 0x00005629616218e5 in main (argc=9, argv=0x7ffed185bda0) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6137
{noformat}

Let's run {{mariabackup}} without providing a user name:

{noformat}
$ mkdir /tmp/backup
$ mariabackup --backup --target-dir=/tmp/backup
[00] 2019-10-05 01:04:56 Connecting to MySQL server host: localhost, user: not set, password: not set, port: not set, socket: not set
Password:
[00] 2019-10-05 01:05:02 Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

Authentication will fail, because the user name is wrong.

The error message sent by the server references an empty user name:

{noformat}
Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

And the error log on the server shows the same thing:

{noformat}
2019-10-05 1:05:02 32 [Warning] Access denied for user ''@'localhost' (using password: NO)
{noformat}

It is still unclear to me why {{mariabackup}} is using an empty string for the user name, rather than using the login user.

Geoff Montee (Inactive) made changes - 2019-10-11 02:18

Description

This bug is similar to ~~CONC-441~~, but this bug applies to tools that use the built-in libmysqlclient, while the other bug applies to clients that use C/C.

For command-line tools, if no user name is provided, then the default behavior is supposed to be that the client will use the name of the current Unix user.

From the MySQL documentation:

{quote}
On Unix, most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only.
{quote}

https://dev.mysql.com/doc/refman/5.7/en/user-names.html

And from the MariaDB documentation:

{quote}
-u, --user=name User for login, if not current user.
{quote}

https://mariadb.com/kb/en/library/mysql-command-line-client/

However, at the moment, the wrong user name is used by default if the login user is different from the effective user.

h2. How the Default User Name is Determined

libmysqlclient determines the default user name by calling {{read_user_name()}} to get the current user:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/libmysqld/libmysql.c#L423

It is called in {{send_client_reply_packet()}}:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql-common/client.c#L2426

The {{read_user_name()}} function gets the user name by checking the following items in the following order:

* If {{geteuid()}} returns {{0}}, then {{root}} is used.
* If {{getlogin()}} is not {{NULL}}, then its return value is used.
* If {{getpwuid(geteuid())}} is not {{NULL}}, then its return value is used.
* If the {{USER}} environment variable is set, then its assigned value is used.
* If the {{LOGNAME}} environment variable is set, then its assigned value is used.
* If the {{LOGIN}} environment variable is set, then its assigned value is used.

This order can cause unexpected results in some cases.

h2. How to Reproduce

For example, let's say that we change users by doing something like this:

{noformat}
$ whoami
ec2-user
$ sudo -u mysql bash
$ whoami
mysql
$ printenv USER
mysql
$ printenv LOGNAME
mysql
$ printenv LOGIN
$ id
uid=997(mysql) gid=994(mysql) groups=994(mysql),1005(shadow)
$ cat /proc/self/loginuid
1000
$ id 1000
uid=1000(ec2-user) gid=1000(ec2-user) groups=1000(ec2-user),4(adm),10(wheel),190(systemd-journal)
{noformat}

In this case, our effective user is {{mysql}}, but the login user is still {{ec2-user}}.

{{mariabackup}} still seems to use libmysqlclient, according to {{gdb}} output, which shows that it calls the versions of {{mysql_real_connect()}} and {{run_plugin_auth()}} defined in {{sql-common/client.c}}:

{noformat}
(gdb) where
#0 0x00007fb1619aef70 in __read_nocancel () from /lib64/libc.so.6
#1 0x00007fb16193bb14 in __GI__IO_file_underflow () from /lib64/libc.so.6
#2 0x00007fb16193cce2 in __GI__IO_default_uflow () from /lib64/libc.so.6
#3 0x00007fb16193754e in getc () from /lib64/libc.so.6
#4 0x00007fb15e94afe0 in get_password (length=1023, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., file=0x7fb161c87640 <_IO_2_1_stdin_>) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:68
#5 get_tty_password (prompt=prompt@entry=0x7fb15e94b0d0 "", buffer=buffer@entry=0x7ffed185a030 '\377' <repeats 200 times>..., length=length@entry=1023) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:162
#6 0x00007fb15e94aeac in auth_dialog_native_prompt (mysql=<optimized out>, type=2, prompt=<optimized out>, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., buffer_len=1024)
    at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:106
#7 0x00007fb15e94ad1d in auth_dialog_open (vio=0x7ffed185a490, mysql=0x5629645279d8) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:159
#8 0x000056296166f10e in run_plugin_auth (mysql=mysql@entry=0x5629645279d8, data=<optimized out>, data@entry=0x56296452c13a "_password", data_len=<optimized out>, data_len@entry=21,
    data_plugin=data_plugin@entry=0x56296452c14f "\f_client_name\blibmysql\004_pid\004\065\067\070\065\017_client_version\a10.3.18\f_server_host\tlocalhost\t_platform\006x86_64", db=db@entry=0x0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:2767
#9 0x00005629616710db in mysql_real_connect (mysql=0x5629645279d8, host=<optimized out>, user=<optimized out>, passwd=<optimized out>, db=<optimized out>, port=<optimized out>, unix_socket=<optimized out>, client_flag=0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:3363
#10 0x0000562961656766 in xb_mysql_connect () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/backup_mysql.cc:148
#11 0x0000562961641c66 in xb_init () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:5830
#12 0x00005629616423f4 in main_low (argv=0x562964526d90) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6294
#13 0x00005629616218e5 in main (argc=9, argv=0x7ffed185bda0) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6137
{noformat}

Let's run {{mariabackup}} without providing a user name:

{noformat}
$ mkdir /tmp/backup
$ mariabackup --backup --target-dir=/tmp/backup
[00] 2019-10-05 01:04:56 Connecting to MySQL server host: localhost, user: not set, password: not set, port: not set, socket: not set
Password:
[00] 2019-10-05 01:05:02 Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

Authentication will fail, because the user name is wrong.

The error message sent by the server references an empty user name:

{noformat}
Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

And the error log on the server shows the same thing:

{noformat}
2019-10-05 1:05:02 32 [Warning] Access denied for user ''@'localhost' (using password: NO)
{noformat}

It is still unclear to me why {{mariabackup}} is using an empty string for the user name, rather than using the login user.

This bug is similar to ~~CONC-441~~, but this bug applies to tools that use the built-in libmysqlclient, while the other bug applies to clients that use C/C.

For command-line tools, if no user name is provided, then the default behavior is supposed to be that the client will use the name of the current Unix user.

From the MySQL documentation:

{quote}
On Unix, most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only.
{quote}

https://dev.mysql.com/doc/refman/5.7/en/user-names.html

And from the MariaDB documentation:

{quote}
-u, --user=name User for login, if not current user.
{quote}

https://mariadb.com/kb/en/library/mysql-command-line-client/

However, at the moment, the wrong user name is used by default if the login user is different from the effective user.

h2. How the Default User Name is Determined

libmysqlclient determines the default user name by calling {{read_user_name()}} to get the current user:

Unfortunately, libmysqlclient's version of this function just sets the user name to the empty string by default:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql/client_settings.h#L40

The embedded server has a "more correct" version of this function:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/libmysqld/libmysql.c#L423

And so does MariaDB Connector/C:

{{read_user_name()}} is called in {{send_client_reply_packet()}}:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql-common/client.c#L2426

The "more correct" version of the {{read_user_name()}} function gets the user name by checking the following items in the following order:

* If {{geteuid()}} returns {{0}}, then {{root}} is used.
* If {{getlogin()}} is not {{NULL}}, then its return value is used.
* If {{getpwuid(geteuid())}} is not {{NULL}}, then its return value is used.
* If the {{USER}} environment variable is set, then its assigned value is used.
* If the {{LOGNAME}} environment variable is set, then its assigned value is used.
* If the {{LOGIN}} environment variable is set, then its assigned value is used.

However, even this order can cause unexpected results in some cases. See ~~CONC-441~~ for more details about that.

h2. How to Reproduce

{{mariabackup}} still seems to use libmysqlclient, according to {{gdb}} output, which shows that it calls the versions of {{mysql_real_connect()}} and {{run_plugin_auth()}} defined in {{sql-common/client.c}}:

{noformat}
(gdb) where
#0 0x00007fb1619aef70 in __read_nocancel () from /lib64/libc.so.6
#1 0x00007fb16193bb14 in __GI__IO_file_underflow () from /lib64/libc.so.6
#2 0x00007fb16193cce2 in __GI__IO_default_uflow () from /lib64/libc.so.6
#3 0x00007fb16193754e in getc () from /lib64/libc.so.6
#4 0x00007fb15e94afe0 in get_password (length=1023, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., file=0x7fb161c87640 <_IO_2_1_stdin_>) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:68
#5 get_tty_password (prompt=prompt@entry=0x7fb15e94b0d0 "", buffer=buffer@entry=0x7ffed185a030 '\377' <repeats 200 times>..., length=length@entry=1023) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:162
#6 0x00007fb15e94aeac in auth_dialog_native_prompt (mysql=<optimized out>, type=2, prompt=<optimized out>, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., buffer_len=1024)
    at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:106
#7 0x00007fb15e94ad1d in auth_dialog_open (vio=0x7ffed185a490, mysql=0x5629645279d8) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:159
#8 0x000056296166f10e in run_plugin_auth (mysql=mysql@entry=0x5629645279d8, data=<optimized out>, data@entry=0x56296452c13a "_password", data_len=<optimized out>, data_len@entry=21,
    data_plugin=data_plugin@entry=0x56296452c14f "\f_client_name\blibmysql\004_pid\004\065\067\070\065\017_client_version\a10.3.18\f_server_host\tlocalhost\t_platform\006x86_64", db=db@entry=0x0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:2767
#9 0x00005629616710db in mysql_real_connect (mysql=0x5629645279d8, host=<optimized out>, user=<optimized out>, passwd=<optimized out>, db=<optimized out>, port=<optimized out>, unix_socket=<optimized out>, client_flag=0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:3363
#10 0x0000562961656766 in xb_mysql_connect () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/backup_mysql.cc:148
#11 0x0000562961641c66 in xb_init () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:5830
#12 0x00005629616423f4 in main_low (argv=0x562964526d90) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6294
#13 0x00005629616218e5 in main (argc=9, argv=0x7ffed185bda0) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6137
{noformat}

Let's run {{mariabackup}} without providing a user name:

{noformat}
$ mkdir /tmp/backup
$ mariabackup --backup --target-dir=/tmp/backup
[00] 2019-10-05 01:04:56 Connecting to MySQL server host: localhost, user: not set, password: not set, port: not set, socket: not set
Password:
[00] 2019-10-05 01:05:02 Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

Authentication will fail, because the user name is wrong.

The error message sent by the server references an empty user name:

{noformat}
Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

And the error log on the server shows the same thing:

{noformat}
2019-10-05 1:05:02 32 [Warning] Access denied for user ''@'localhost' (using password: NO)
{noformat}

Geoff Montee (Inactive) made changes - 2019-10-11 02:19

Summary

Default user name for libmysqlclient is wrong if login user is different from effective user

Default user name for libmysqlclient is empty

Geoff Montee (Inactive) made changes - 2019-10-11 02:20

Description

This bug is similar to ~~CONC-441~~, but this bug applies to tools that use the built-in libmysqlclient, while the other bug applies to clients that use C/C.

For command-line tools, if no user name is provided, then the default behavior is supposed to be that the client will use the name of the current Unix user.

From the MySQL documentation:

{quote}
On Unix, most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only.
{quote}

https://dev.mysql.com/doc/refman/5.7/en/user-names.html

And from the MariaDB documentation:

{quote}
-u, --user=name User for login, if not current user.
{quote}

https://mariadb.com/kb/en/library/mysql-command-line-client/

However, at the moment, the wrong user name is used by default if the login user is different from the effective user.

h2. How the Default User Name is Determined

libmysqlclient determines the default user name by calling {{read_user_name()}} to get the current user:

Unfortunately, libmysqlclient's version of this function just sets the user name to the empty string by default:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql/client_settings.h#L40

The embedded server has a "more correct" version of this function:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/libmysqld/libmysql.c#L423

And so does MariaDB Connector/C:

{{read_user_name()}} is called in {{send_client_reply_packet()}}:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql-common/client.c#L2426

The "more correct" version of the {{read_user_name()}} function gets the user name by checking the following items in the following order:

* If {{geteuid()}} returns {{0}}, then {{root}} is used.
* If {{getlogin()}} is not {{NULL}}, then its return value is used.
* If {{getpwuid(geteuid())}} is not {{NULL}}, then its return value is used.
* If the {{USER}} environment variable is set, then its assigned value is used.
* If the {{LOGNAME}} environment variable is set, then its assigned value is used.
* If the {{LOGIN}} environment variable is set, then its assigned value is used.

However, even this order can cause unexpected results in some cases. See ~~CONC-441~~ for more details about that.

h2. How to Reproduce

{{mariabackup}} still seems to use libmysqlclient, according to {{gdb}} output, which shows that it calls the versions of {{mysql_real_connect()}} and {{run_plugin_auth()}} defined in {{sql-common/client.c}}:

{noformat}
(gdb) where
#0 0x00007fb1619aef70 in __read_nocancel () from /lib64/libc.so.6
#1 0x00007fb16193bb14 in __GI__IO_file_underflow () from /lib64/libc.so.6
#2 0x00007fb16193cce2 in __GI__IO_default_uflow () from /lib64/libc.so.6
#3 0x00007fb16193754e in getc () from /lib64/libc.so.6
#4 0x00007fb15e94afe0 in get_password (length=1023, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., file=0x7fb161c87640 <_IO_2_1_stdin_>) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:68
#5 get_tty_password (prompt=prompt@entry=0x7fb15e94b0d0 "", buffer=buffer@entry=0x7ffed185a030 '\377' <repeats 200 times>..., length=length@entry=1023) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:162
#6 0x00007fb15e94aeac in auth_dialog_native_prompt (mysql=<optimized out>, type=2, prompt=<optimized out>, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., buffer_len=1024)
    at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:106
#7 0x00007fb15e94ad1d in auth_dialog_open (vio=0x7ffed185a490, mysql=0x5629645279d8) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:159
#8 0x000056296166f10e in run_plugin_auth (mysql=mysql@entry=0x5629645279d8, data=<optimized out>, data@entry=0x56296452c13a "_password", data_len=<optimized out>, data_len@entry=21,
    data_plugin=data_plugin@entry=0x56296452c14f "\f_client_name\blibmysql\004_pid\004\065\067\070\065\017_client_version\a10.3.18\f_server_host\tlocalhost\t_platform\006x86_64", db=db@entry=0x0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:2767
#9 0x00005629616710db in mysql_real_connect (mysql=0x5629645279d8, host=<optimized out>, user=<optimized out>, passwd=<optimized out>, db=<optimized out>, port=<optimized out>, unix_socket=<optimized out>, client_flag=0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:3363
#10 0x0000562961656766 in xb_mysql_connect () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/backup_mysql.cc:148
#11 0x0000562961641c66 in xb_init () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:5830
#12 0x00005629616423f4 in main_low (argv=0x562964526d90) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6294
#13 0x00005629616218e5 in main (argc=9, argv=0x7ffed185bda0) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6137
{noformat}

Let's run {{mariabackup}} without providing a user name:

{noformat}
$ mkdir /tmp/backup
$ mariabackup --backup --target-dir=/tmp/backup
[00] 2019-10-05 01:04:56 Connecting to MySQL server host: localhost, user: not set, password: not set, port: not set, socket: not set
Password:
[00] 2019-10-05 01:05:02 Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

Authentication will fail, because the user name is wrong.

The error message sent by the server references an empty user name:

{noformat}
Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

And the error log on the server shows the same thing:

{noformat}
2019-10-05 1:05:02 32 [Warning] Access denied for user ''@'localhost' (using password: NO)
{noformat}

This bug is similar to ~~CONC-441~~, but this bug applies to tools that use the built-in libmysqlclient, while the other bug applies to clients that use C/C.

For command-line tools, if no user name is provided, then the default behavior is supposed to be that the client will use the name of the current Unix user.

From the MySQL documentation:

{quote}
On Unix, most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only.
{quote}

https://dev.mysql.com/doc/refman/5.7/en/user-names.html

And from the MariaDB documentation:

{quote}
-u, --user=name User for login, if not current user.
{quote}

https://mariadb.com/kb/en/library/mysql-command-line-client/

However, at the moment, the wrong user name is used by default if the login user is different from the effective user.

h2. How the Default User Name is Determined

libmysqlclient determines the default user name by calling {{read_user_name()}} to get the current user:

Unfortunately, libmysqlclient's version of this function just sets the user name to the empty string by default:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql/client_settings.h#L40

The embedded server has a "more correct" version of this function:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/libmysqld/libmysql.c#L423

And so does MariaDB Connector/C:

{{read_user_name()}} is called in {{send_client_reply_packet()}}:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql-common/client.c#L2426

The "more correct" version of the {{read_user_name()}} function gets the user name by checking the following items in the following order:

* If {{geteuid()}} returns {{0}}, then {{root}} is used.
* If {{getlogin()}} is not {{NULL}}, then its return value is used.
* If {{getpwuid(geteuid())}} is not {{NULL}}, then its return value is used.
* If the {{USER}} environment variable is set, then its assigned value is used.
* If the {{LOGNAME}} environment variable is set, then its assigned value is used.
* If the {{LOGIN}} environment variable is set, then its assigned value is used.

However, even this order can cause unexpected results in some cases. See ~~CONC-441~~ for more details about that.

h2. How to Reproduce

{{mariabackup}} still seems to use libmysqlclient, according to {{gdb}} output, which shows that it calls the versions of {{mysql_real_connect()}} and {{run_plugin_auth()}} defined in {{sql-common/client.c}}:

{noformat}
(gdb) where
#0 0x00007fb1619aef70 in __read_nocancel () from /lib64/libc.so.6
#1 0x00007fb16193bb14 in __GI__IO_file_underflow () from /lib64/libc.so.6
#2 0x00007fb16193cce2 in __GI__IO_default_uflow () from /lib64/libc.so.6
#3 0x00007fb16193754e in getc () from /lib64/libc.so.6
#4 0x00007fb15e94afe0 in get_password (length=1023, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., file=0x7fb161c87640 <_IO_2_1_stdin_>) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:68
#5 get_tty_password (prompt=prompt@entry=0x7fb15e94b0d0 "", buffer=buffer@entry=0x7ffed185a030 '\377' <repeats 200 times>..., length=length@entry=1023) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:162
#6 0x00007fb15e94aeac in auth_dialog_native_prompt (mysql=<optimized out>, type=2, prompt=<optimized out>, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., buffer_len=1024)
    at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:106
#7 0x00007fb15e94ad1d in auth_dialog_open (vio=0x7ffed185a490, mysql=0x5629645279d8) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:159
#8 0x000056296166f10e in run_plugin_auth (mysql=mysql@entry=0x5629645279d8, data=<optimized out>, data@entry=0x56296452c13a "_password", data_len=<optimized out>, data_len@entry=21,
    data_plugin=data_plugin@entry=0x56296452c14f "\f_client_name\blibmysql\004_pid\004\065\067\070\065\017_client_version\a10.3.18\f_server_host\tlocalhost\t_platform\006x86_64", db=db@entry=0x0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:2767
#9 0x00005629616710db in mysql_real_connect (mysql=0x5629645279d8, host=<optimized out>, user=<optimized out>, passwd=<optimized out>, db=<optimized out>, port=<optimized out>, unix_socket=<optimized out>, client_flag=0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:3363
#10 0x0000562961656766 in xb_mysql_connect () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/backup_mysql.cc:148
#11 0x0000562961641c66 in xb_init () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:5830
#12 0x00005629616423f4 in main_low (argv=0x562964526d90) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6294
#13 0x00005629616218e5 in main (argc=9, argv=0x7ffed185bda0) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6137
{noformat}

Let's run {{mariabackup}} without providing a user name:

{noformat}
$ mkdir /tmp/backup
$ mariabackup --backup --target-dir=/tmp/backup
[00] 2019-10-05 01:04:56 Connecting to MySQL server host: localhost, user: not set, password: not set, port: not set, socket: not set
Password:
[00] 2019-10-05 01:05:02 Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

Authentication will fail, because the user name is wrong.

The error message sent by the server references an empty user name:

{noformat}
Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

And the error log on the server shows the same thing:

{noformat}
2019-10-05 1:05:02 32 [Warning] Access denied for user ''@'localhost' (using password: NO)
{noformat}

h2. Suggested Fix

libmysqlclient's version of the {{read_user_name()}} function should be fixed to use the effective user as the default user.

Geoff Montee (Inactive) made changes - 2019-10-11 02:21

Description

This bug is similar to ~~CONC-441~~, but this bug applies to tools that use the built-in libmysqlclient, while the other bug applies to clients that use C/C.

For command-line tools, if no user name is provided, then the default behavior is supposed to be that the client will use the name of the current Unix user.

From the MySQL documentation:

{quote}
On Unix, most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only.
{quote}

https://dev.mysql.com/doc/refman/5.7/en/user-names.html

And from the MariaDB documentation:

{quote}
-u, --user=name User for login, if not current user.
{quote}

https://mariadb.com/kb/en/library/mysql-command-line-client/

However, at the moment, the wrong user name is used by default if the login user is different from the effective user.

h2. How the Default User Name is Determined

libmysqlclient determines the default user name by calling {{read_user_name()}} to get the current user:

Unfortunately, libmysqlclient's version of this function just sets the user name to the empty string by default:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql/client_settings.h#L40

The embedded server has a "more correct" version of this function:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/libmysqld/libmysql.c#L423

And so does MariaDB Connector/C:

{{read_user_name()}} is called in {{send_client_reply_packet()}}:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql-common/client.c#L2426

The "more correct" version of the {{read_user_name()}} function gets the user name by checking the following items in the following order:

* If {{geteuid()}} returns {{0}}, then {{root}} is used.
* If {{getlogin()}} is not {{NULL}}, then its return value is used.
* If {{getpwuid(geteuid())}} is not {{NULL}}, then its return value is used.
* If the {{USER}} environment variable is set, then its assigned value is used.
* If the {{LOGNAME}} environment variable is set, then its assigned value is used.
* If the {{LOGIN}} environment variable is set, then its assigned value is used.

However, even this order can cause unexpected results in some cases. See ~~CONC-441~~ for more details about that.

h2. How to Reproduce

{{mariabackup}} still seems to use libmysqlclient, according to {{gdb}} output, which shows that it calls the versions of {{mysql_real_connect()}} and {{run_plugin_auth()}} defined in {{sql-common/client.c}}:

{noformat}
(gdb) where
#0 0x00007fb1619aef70 in __read_nocancel () from /lib64/libc.so.6
#1 0x00007fb16193bb14 in __GI__IO_file_underflow () from /lib64/libc.so.6
#2 0x00007fb16193cce2 in __GI__IO_default_uflow () from /lib64/libc.so.6
#3 0x00007fb16193754e in getc () from /lib64/libc.so.6
#4 0x00007fb15e94afe0 in get_password (length=1023, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., file=0x7fb161c87640 <_IO_2_1_stdin_>) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:68
#5 get_tty_password (prompt=prompt@entry=0x7fb15e94b0d0 "", buffer=buffer@entry=0x7ffed185a030 '\377' <repeats 200 times>..., length=length@entry=1023) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:162
#6 0x00007fb15e94aeac in auth_dialog_native_prompt (mysql=<optimized out>, type=2, prompt=<optimized out>, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., buffer_len=1024)
    at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:106
#7 0x00007fb15e94ad1d in auth_dialog_open (vio=0x7ffed185a490, mysql=0x5629645279d8) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:159
#8 0x000056296166f10e in run_plugin_auth (mysql=mysql@entry=0x5629645279d8, data=<optimized out>, data@entry=0x56296452c13a "_password", data_len=<optimized out>, data_len@entry=21,
    data_plugin=data_plugin@entry=0x56296452c14f "\f_client_name\blibmysql\004_pid\004\065\067\070\065\017_client_version\a10.3.18\f_server_host\tlocalhost\t_platform\006x86_64", db=db@entry=0x0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:2767
#9 0x00005629616710db in mysql_real_connect (mysql=0x5629645279d8, host=<optimized out>, user=<optimized out>, passwd=<optimized out>, db=<optimized out>, port=<optimized out>, unix_socket=<optimized out>, client_flag=0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:3363
#10 0x0000562961656766 in xb_mysql_connect () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/backup_mysql.cc:148
#11 0x0000562961641c66 in xb_init () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:5830
#12 0x00005629616423f4 in main_low (argv=0x562964526d90) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6294
#13 0x00005629616218e5 in main (argc=9, argv=0x7ffed185bda0) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6137
{noformat}

Let's run {{mariabackup}} without providing a user name:

{noformat}
$ mkdir /tmp/backup
$ mariabackup --backup --target-dir=/tmp/backup
[00] 2019-10-05 01:04:56 Connecting to MySQL server host: localhost, user: not set, password: not set, port: not set, socket: not set
Password:
[00] 2019-10-05 01:05:02 Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

Authentication will fail, because the user name is wrong.

The error message sent by the server references an empty user name:

{noformat}
Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

And the error log on the server shows the same thing:

{noformat}
2019-10-05 1:05:02 32 [Warning] Access denied for user ''@'localhost' (using password: NO)
{noformat}

h2. Suggested Fix

libmysqlclient's version of the {{read_user_name()}} function should be fixed to use the effective user as the default user.

This bug is similar to ~~CONC-441~~, but this bug applies to tools that use the built-in libmysqlclient, while the other bug applies to clients that use MariaDB Connector/C.

For command-line tools, if no user name is provided, then the default behavior is supposed to be that the client will use the name of the current Unix user.

From the MySQL documentation:

{quote}
On Unix, most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only.
{quote}

https://dev.mysql.com/doc/refman/5.7/en/user-names.html

And from the MariaDB documentation:

{quote}
-u, --user=name User for login, if not current user.
{quote}

https://mariadb.com/kb/en/library/mysql-command-line-client/

However, at the moment, the wrong user name is used by default if the login user is different from the effective user.

h2. How the Default User Name is Determined

libmysqlclient determines the default user name by calling {{read_user_name()}} to get the current user:

Unfortunately, libmysqlclient's version of this function just sets the user name to the empty string by default:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql/client_settings.h#L40

The embedded server has a "more correct" version of this function:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/libmysqld/libmysql.c#L423

And so does MariaDB Connector/C:

https://github.com/MariaDB/mariadb-connector-c/blob/v3.1.3/libmariadb/mariadb_lib.c#L498

{{read_user_name()}} is called in {{send_client_reply_packet()}}:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql-common/client.c#L2426

The "more correct" version of the {{read_user_name()}} function gets the user name by checking the following items in the following order:

* If {{geteuid()}} returns {{0}}, then {{root}} is used.
* If {{getlogin()}} is not {{NULL}}, then its return value is used.
* If {{getpwuid(geteuid())}} is not {{NULL}}, then its return value is used.
* If the {{USER}} environment variable is set, then its assigned value is used.
* If the {{LOGNAME}} environment variable is set, then its assigned value is used.
* If the {{LOGIN}} environment variable is set, then its assigned value is used.

However, even this order can cause unexpected results in some cases. See ~~CONC-441~~ for more details about that.

h2. How to Reproduce

{{mariabackup}} still seems to use libmysqlclient, according to {{gdb}} output, which shows that it calls the versions of {{mysql_real_connect()}} and {{run_plugin_auth()}} defined in {{sql-common/client.c}}:

{noformat}
(gdb) where
#0 0x00007fb1619aef70 in __read_nocancel () from /lib64/libc.so.6
#1 0x00007fb16193bb14 in __GI__IO_file_underflow () from /lib64/libc.so.6
#2 0x00007fb16193cce2 in __GI__IO_default_uflow () from /lib64/libc.so.6
#3 0x00007fb16193754e in getc () from /lib64/libc.so.6
#4 0x00007fb15e94afe0 in get_password (length=1023, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., file=0x7fb161c87640 <_IO_2_1_stdin_>) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:68
#5 get_tty_password (prompt=prompt@entry=0x7fb15e94b0d0 "", buffer=buffer@entry=0x7ffed185a030 '\377' <repeats 200 times>..., length=length@entry=1023) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:162
#6 0x00007fb15e94aeac in auth_dialog_native_prompt (mysql=<optimized out>, type=2, prompt=<optimized out>, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., buffer_len=1024)
    at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:106
#7 0x00007fb15e94ad1d in auth_dialog_open (vio=0x7ffed185a490, mysql=0x5629645279d8) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:159
#8 0x000056296166f10e in run_plugin_auth (mysql=mysql@entry=0x5629645279d8, data=<optimized out>, data@entry=0x56296452c13a "_password", data_len=<optimized out>, data_len@entry=21,
    data_plugin=data_plugin@entry=0x56296452c14f "\f_client_name\blibmysql\004_pid\004\065\067\070\065\017_client_version\a10.3.18\f_server_host\tlocalhost\t_platform\006x86_64", db=db@entry=0x0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:2767
#9 0x00005629616710db in mysql_real_connect (mysql=0x5629645279d8, host=<optimized out>, user=<optimized out>, passwd=<optimized out>, db=<optimized out>, port=<optimized out>, unix_socket=<optimized out>, client_flag=0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:3363
#10 0x0000562961656766 in xb_mysql_connect () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/backup_mysql.cc:148
#11 0x0000562961641c66 in xb_init () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:5830
#12 0x00005629616423f4 in main_low (argv=0x562964526d90) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6294
#13 0x00005629616218e5 in main (argc=9, argv=0x7ffed185bda0) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6137
{noformat}

Let's run {{mariabackup}} without providing a user name:

{noformat}
$ mkdir /tmp/backup
$ mariabackup --backup --target-dir=/tmp/backup
[00] 2019-10-05 01:04:56 Connecting to MySQL server host: localhost, user: not set, password: not set, port: not set, socket: not set
Password:
[00] 2019-10-05 01:05:02 Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

Authentication will fail, because the user name is wrong.

The error message sent by the server references an empty user name:

{noformat}
Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

And the error log on the server shows the same thing:

{noformat}
2019-10-05 1:05:02 32 [Warning] Access denied for user ''@'localhost' (using password: NO)
{noformat}

h2. Suggested Fix

libmysqlclient's version of the {{read_user_name()}} function should be fixed to use the effective user as the default user.

Geoff Montee (Inactive) made changes - 2019-10-11 19:30

Description

This bug is similar to ~~CONC-441~~, but this bug applies to tools that use the built-in libmysqlclient, while the other bug applies to clients that use MariaDB Connector/C.

For command-line tools, if no user name is provided, then the default behavior is supposed to be that the client will use the name of the current Unix user.

From the MySQL documentation:

{quote}
On Unix, most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only.
{quote}

https://dev.mysql.com/doc/refman/5.7/en/user-names.html

And from the MariaDB documentation:

{quote}
-u, --user=name User for login, if not current user.
{quote}

https://mariadb.com/kb/en/library/mysql-command-line-client/

However, at the moment, the wrong user name is used by default if the login user is different from the effective user.

h2. How the Default User Name is Determined

libmysqlclient determines the default user name by calling {{read_user_name()}} to get the current user:

Unfortunately, libmysqlclient's version of this function just sets the user name to the empty string by default:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql/client_settings.h#L40

The embedded server has a "more correct" version of this function:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/libmysqld/libmysql.c#L423

And so does MariaDB Connector/C:

https://github.com/MariaDB/mariadb-connector-c/blob/v3.1.3/libmariadb/mariadb_lib.c#L498

{{read_user_name()}} is called in {{send_client_reply_packet()}}:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql-common/client.c#L2426

The "more correct" version of the {{read_user_name()}} function gets the user name by checking the following items in the following order:

* If {{geteuid()}} returns {{0}}, then {{root}} is used.
* If {{getlogin()}} is not {{NULL}}, then its return value is used.
* If {{getpwuid(geteuid())}} is not {{NULL}}, then its return value is used.
* If the {{USER}} environment variable is set, then its assigned value is used.
* If the {{LOGNAME}} environment variable is set, then its assigned value is used.
* If the {{LOGIN}} environment variable is set, then its assigned value is used.

However, even this order can cause unexpected results in some cases. See ~~CONC-441~~ for more details about that.

h2. How to Reproduce

{{mariabackup}} still seems to use libmysqlclient, according to {{gdb}} output, which shows that it calls the versions of {{mysql_real_connect()}} and {{run_plugin_auth()}} defined in {{sql-common/client.c}}:

{noformat}
(gdb) where
#0 0x00007fb1619aef70 in __read_nocancel () from /lib64/libc.so.6
#1 0x00007fb16193bb14 in __GI__IO_file_underflow () from /lib64/libc.so.6
#2 0x00007fb16193cce2 in __GI__IO_default_uflow () from /lib64/libc.so.6
#3 0x00007fb16193754e in getc () from /lib64/libc.so.6
#4 0x00007fb15e94afe0 in get_password (length=1023, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., file=0x7fb161c87640 <_IO_2_1_stdin_>) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:68
#5 get_tty_password (prompt=prompt@entry=0x7fb15e94b0d0 "", buffer=buffer@entry=0x7ffed185a030 '\377' <repeats 200 times>..., length=length@entry=1023) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:162
#6 0x00007fb15e94aeac in auth_dialog_native_prompt (mysql=<optimized out>, type=2, prompt=<optimized out>, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., buffer_len=1024)
    at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:106
#7 0x00007fb15e94ad1d in auth_dialog_open (vio=0x7ffed185a490, mysql=0x5629645279d8) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:159
#8 0x000056296166f10e in run_plugin_auth (mysql=mysql@entry=0x5629645279d8, data=<optimized out>, data@entry=0x56296452c13a "_password", data_len=<optimized out>, data_len@entry=21,
    data_plugin=data_plugin@entry=0x56296452c14f "\f_client_name\blibmysql\004_pid\004\065\067\070\065\017_client_version\a10.3.18\f_server_host\tlocalhost\t_platform\006x86_64", db=db@entry=0x0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:2767
#9 0x00005629616710db in mysql_real_connect (mysql=0x5629645279d8, host=<optimized out>, user=<optimized out>, passwd=<optimized out>, db=<optimized out>, port=<optimized out>, unix_socket=<optimized out>, client_flag=0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:3363
#10 0x0000562961656766 in xb_mysql_connect () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/backup_mysql.cc:148
#11 0x0000562961641c66 in xb_init () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:5830
#12 0x00005629616423f4 in main_low (argv=0x562964526d90) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6294
#13 0x00005629616218e5 in main (argc=9, argv=0x7ffed185bda0) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6137
{noformat}

Let's run {{mariabackup}} without providing a user name:

{noformat}
$ mkdir /tmp/backup
$ mariabackup --backup --target-dir=/tmp/backup
[00] 2019-10-05 01:04:56 Connecting to MySQL server host: localhost, user: not set, password: not set, port: not set, socket: not set
Password:
[00] 2019-10-05 01:05:02 Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

Authentication will fail, because the user name is wrong.

The error message sent by the server references an empty user name:

{noformat}
Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

And the error log on the server shows the same thing:

{noformat}
2019-10-05 1:05:02 32 [Warning] Access denied for user ''@'localhost' (using password: NO)
{noformat}

h2. Suggested Fix

libmysqlclient's version of the {{read_user_name()}} function should be fixed to use the effective user as the default user.

This bug is similar to ~~CONC-441~~, but this bug applies to tools that use the built-in libmysqlclient, while the other bug applies to clients that use MariaDB Connector/C.

For command-line tools, if no user name is provided, then the default behavior is supposed to be that the client will use the name of the current Unix user.

From the MySQL documentation:

{quote}
On Unix, most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only.
{quote}

https://dev.mysql.com/doc/refman/5.7/en/user-names.html

And from the MariaDB documentation:

{quote}
-u, --user=name User for login, if not current user.
{quote}

https://mariadb.com/kb/en/library/mysql-command-line-client/

However, at the moment, this does not happen. Instead, an empty user name (i.e. {{''}}) is used by default.

h2. How the Default User Name is Determined

libmysqlclient determines the default user name by calling {{read_user_name()}} to get the current user. Unfortunately, libmysqlclient's version of this function just sets the user name to the empty string by default:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql/client_settings.h#L40

The embedded server (libmysqld) has a "more correct" version of this function:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/libmysqld/libmysql.c#L423

And so does MariaDB Connector/C:

https://github.com/MariaDB/mariadb-connector-c/blob/v3.1.3/libmariadb/mariadb_lib.c#L498

{{read_user_name()}} is called in {{send_client_reply_packet()}}:

https://github.com/MariaDB/server/blob/mariadb-10.2.27/sql-common/client.c#L2426

The "more correct" version of the {{read_user_name()}} function gets the user name by checking the following items in the following order:

* If {{geteuid()}} returns {{0}}, then {{root}} is used.
* If {{getlogin()}} is not {{NULL}}, then its return value is used.
* If {{getpwuid(geteuid())}} is not {{NULL}}, then its return value is used.
* If the {{USER}} environment variable is set, then its assigned value is used.
* If the {{LOGNAME}} environment variable is set, then its assigned value is used.
* If the {{LOGIN}} environment variable is set, then its assigned value is used.

However, even this order can cause unexpected results in some cases. See ~~CONC-441~~ for more details about that.

h2. How to Reproduce

{{mariabackup}} still seems to use libmysqlclient, according to {{gdb}} output, which shows that it calls the versions of {{mysql_real_connect()}} and {{run_plugin_auth()}} defined in {{sql-common/client.c}}:

{noformat}
(gdb) where
#0 0x00007fb1619aef70 in __read_nocancel () from /lib64/libc.so.6
#1 0x00007fb16193bb14 in __GI__IO_file_underflow () from /lib64/libc.so.6
#2 0x00007fb16193cce2 in __GI__IO_default_uflow () from /lib64/libc.so.6
#3 0x00007fb16193754e in getc () from /lib64/libc.so.6
#4 0x00007fb15e94afe0 in get_password (length=1023, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., file=0x7fb161c87640 <_IO_2_1_stdin_>) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:68
#5 get_tty_password (prompt=prompt@entry=0x7fb15e94b0d0 "", buffer=buffer@entry=0x7ffed185a030 '\377' <repeats 200 times>..., length=length@entry=1023) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/libmariadb/get_password.c:162
#6 0x00007fb15e94aeac in auth_dialog_native_prompt (mysql=<optimized out>, type=2, prompt=<optimized out>, buffer=0x7ffed185a030 '\377' <repeats 200 times>..., buffer_len=1024)
    at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:106
#7 0x00007fb15e94ad1d in auth_dialog_open (vio=0x7ffed185a490, mysql=0x5629645279d8) at /usr/src/debug/MariaDB-10.3.18/src_0/libmariadb/plugins/auth/dialog.c:159
#8 0x000056296166f10e in run_plugin_auth (mysql=mysql@entry=0x5629645279d8, data=<optimized out>, data@entry=0x56296452c13a "_password", data_len=<optimized out>, data_len@entry=21,
    data_plugin=data_plugin@entry=0x56296452c14f "\f_client_name\blibmysql\004_pid\004\065\067\070\065\017_client_version\a10.3.18\f_server_host\tlocalhost\t_platform\006x86_64", db=db@entry=0x0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:2767
#9 0x00005629616710db in mysql_real_connect (mysql=0x5629645279d8, host=<optimized out>, user=<optimized out>, passwd=<optimized out>, db=<optimized out>, port=<optimized out>, unix_socket=<optimized out>, client_flag=0)
    at /usr/src/debug/MariaDB-10.3.18/src_0/sql-common/client.c:3363
#10 0x0000562961656766 in xb_mysql_connect () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/backup_mysql.cc:148
#11 0x0000562961641c66 in xb_init () at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:5830
#12 0x00005629616423f4 in main_low (argv=0x562964526d90) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6294
#13 0x00005629616218e5 in main (argc=9, argv=0x7ffed185bda0) at /usr/src/debug/MariaDB-10.3.18/src_0/extra/mariabackup/xtrabackup.cc:6137
{noformat}

Let's run {{mariabackup}} without providing a user name:

{noformat}
$ mkdir /tmp/backup
$ mariabackup --backup --target-dir=/tmp/backup
[00] 2019-10-05 01:04:56 Connecting to MySQL server host: localhost, user: not set, password: not set, port: not set, socket: not set
Password:
[00] 2019-10-05 01:05:02 Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

Authentication will fail, because the user name is empty.

The error message sent by the server references the empty user name:

{noformat}
Failed to connect to MySQL server: Access denied for user ''@'localhost' (using password: NO).
{noformat}

And the error log on the server shows the same thing:

{noformat}
2019-10-05 1:05:02 32 [Warning] Access denied for user ''@'localhost' (using password: NO)
{noformat}

h2. Suggested Fix

libmysqlclient's version of the {{read_user_name()}} function should be fixed to use the effective user as the default user.

Sergei Golubchik made changes - 2021-12-06 21:34

Workflow

MariaDB v3 [ 100195 ]

MariaDB v4 [ 141579 ]

Ralf Gebhardt made changes - 2022-08-04 08:45

Fix Version/s

10.2 [ 14601 ]

Julien Fritsch made changes - 2023-04-27 14:24

Fix Version/s

10.3 [ 22126 ]

MariaDB Server

Default user name for libmysqlclient is empty

Details

Description

How the Default User Name is Determined

How to Reproduce

Suggested Fix

Attachments

Issue Links

Activity

People

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