[DNS] 把Named 產生的log放到遠端伺服器 @新精讚

此例是把named的log放到logserver。

CentOS Linux release 7.4.1708 (Core) &&
Rocky Linux release 9.3 (Blue Onyx)

修改named.conf

named.conf 在options{} 後加上以下設定^[1]

logging {
.. <部分省略>
         channel lamer-log {
                 file "data/lamer-log" versions 3 size 100m;
                 severity info;
                 print-severity yes;
                 print-time yes;
                 print-category yes;
         };
         channel query-log {
                 file "data/query-log" versions 20 size 100m;
                 severity info;
                 print-severity yes;
                 print-time yes;
                 print-category yes;
         };
...
         category lame-servers { lamer-log; };
         category queries { query-log;};
};

file "data/lamer-log" versions 3 size 100m;

此範例log檔會存在 /var/named/data/ 的目錄下，檔名會是 lamer-log、 lamer-log.0、 lamer-log.1 共存 3份，每份最大100mb循環寫入

重啟named

# service named restart

修改 rsyslog.conf

修改rsyslog.conf [3]

加入模組 imfile

CentOS Linux release 7.4.1708 (Core)

$ModLoad imfile

Rocky Linux release 9.3 (Blue Onyx)

module(load="imfile")

新增檔案 /etc/rsyslog.d/named.conf

input(type="imfile" File="/var/named/data/query-log" Tag="ddnss-querylog" Facility="local3" Ruleset="nreporter")
input(type="imfile" File="/var/named/data/lamer-log" Tag="ddnss-lamerlog" Facility="local3" Ruleset="nreporter")
ruleset(name="nreporter"){ action(type="omfwd" Target="192.168.53.147" Port="514" Protocol="udp") }

重啟 rsyslog

# service rsyslog restart

如此就能把LOGS 送到遠端的機器192.168.53.147中。

我是這樣想的，結果LOG SERVER一直沒有收到資料，原來是SELINUX的問題…

SELINUX

Selinux 如果不關掉的話，在啟動rsyslog時就會出錯^[4]

python: SELinux is preventing in:imfile from read access on the file query-log.#012#012***** Plugin catchall (100. confidence) suggests **************************#012#012If you believe that in:imfile should be allowed read access on the query-log file by default.#012Then you should report this as a bug.#012You can generate a local policy module to allow this access.#012Do#012allow this access for now by executing:#012# ausearch -c 'in:imfile' --raw | audit2allow -M my-inimfile#012# semodule -i my-inimfile.pp#012

audit中的錯誤

type=AVC msg=audit(1710820132.783:14087335): avc: denied { getattr } for pid=22562 comm="in:imfile" path="/var/named/data/query-log" dev="dm-0" ino=34444606 scontext=system_u:system_r:syslogd_t:s0 tcontext=system_u:object_r:named_cache_t:s0 tclass=file

AVC stands for Access Vector Cache. [2]

依上面的指示下指令

# ausearch -c 'in:imfile' --raw | audit2allow -M my-inimfile

# semodule -i my-inimfile.pp

查看

# audit2allow -a

#============= syslogd_t ==============
#!!!! This avc is allowed in the current policy
allow syslogd_t named_cache_t:file { getattr ioctl open read };

以上就能正確的將NAMED產生的LOG傳到LOG SERVER了。

參考資料

[1] BIND Queries log to Remote Syslog Server https://www.linuxquestions.org/questions/linux-server-73/bind-queries-log-to-remote-syslog-server-4175669371/

[2] https://wiki.gentoo.org/wiki/SELinux/Tutorials/Where_to_find_SELinux_permission_denial_details

[3] https://www.npartnertech.com/upload/Download/N-Partner_Linux_BIND(DNS)_syslog-TW-004.pdf

[4] https://access.redhat.com/documentation/zh-tw/red_hat_enterprise_linux/6/html/security-enhanced_linux/sect-security-enhanced_linux-selinux_contexts_labeling_files-persistent_changes_semanage_fcontext