TIPs:
世界上有一撮人专门研究主机安全加固基线，有兴趣的读者可以到 http://benchmarks.cisecurity.org/ 获取更加详细专业的主机安全基线配置文档。或者到 https://www.open-scap.org/security-policies/choosing-policy/获取scap格式的加固模板。
CentOS 7 主机加固手册-上
CentOS 7 主机加固手册-中
CentOS 7 主机加固手册-下
0x01 Kickstart自动化安装
通过kickstart脚本安装操作系统，最小化安装，预分区并设置严格的挂载权限。
#version=RHEL7 install # System authorization information auth --enableshadow --passalgo=sha512 # Use CDROM installation media cdrom # Accept EULA eula --agreed services --enabled=NetworkManager,sshd reboot # Run the Setup Agent on first boot #firstboot --enable ignoredisk --only-use=sda # Keyboard layouts keyboard --vckeymap=us --xlayouts='us' # System language lang en_US.UTF-8 # SELinux selinux --enforcing # Network information network --bootproto=dhcp --device=eno16777736 --onboot=on --ipv6=off network --hostname=default-vm # Root password rootpw --iscrypted HASHGOESHERE # System timezone timezone Europe/London --isUtc --ntpservers=prime.transformers # System bootloader configuration bootloader --location=mbr --boot-drive=sda # Partition clearing information clearpart --all --drives=sda ignoredisk --only-use=sda # LVM # Disk partitioning information part pv.18 --fstype="lvmpv" --ondisk=sda --size=8004 part pv.11 --fstype="lvmpv" --ondisk=sda --size=8004 part /boot --fstype="ext4" --ondisk=sda --size=1000 volgroup lg_data --pesize=4096 pv.18 volgroup lg_os --pesize=4096 pv.11 logvol / --fstype="xfs" --size=4000 --name=lv_root --vgname=lg_os logvol /home --fstype="xfs" --size=2000 --name=lv_home --vgname=lg_data logvol /tmp --fstype="xfs" --size=1000 --name=lv_tmp --vgname=lg_os logvol /var --fstype="xfs" --size=2000 --name=lv_var --vgname=lg_os logvol /var/tmp --fstype="xfs" --size=1000 --name=lv_var_tmp --vgname=lg_os logvol /var/www --fstype="xfs" --size=5000 --name=lv_var_www --vgname=lg_data logvol /var/log --fstype="xfs" --size=1500 --name=lv_var_log --vgname=lg_os logvol /var/log/audit --fstype="xfs" --size=500 --name=lv_var_log_audit --vgname=lg_os logvol swap --fstype="swap" --size=1000 --name=lv_swap --vgname=lg_data %packages @core %end %post %end
0x02 安全地挂载分区
如果网站是动态网站，那么网站所在的盘不可以使用noexec挂载选项。像/tmp和/var/tmp应该使用noexec挂载选项，因为黑客通常在这两个目录里面上传并执行提权程序。
一个安全地/etc/fstab 文件配置举例：
# # /etc/fstab # Created by anaconda on Sat Oct 11 14:28:47 2014 # # Accessible filesystems, by reference, are maintained under '/dev/disk' # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info # /dev/mapper/lg_os-lv_root / xfs defaults 1 1 UUID=d73c5d22-75ed-416e-aad2-8c1bb1dfc713 /boot ext4 defaults,nosuid,noexec,nodev 1 2 /dev/mapper/lg_data-lv_home /home xfs defaults 1 2 /dev/mapper/lg_os-lv_tmp /tmp xfs defaults,nosuid,noexec,nodev 1 2 /dev/mapper/lg_os-lv_var /var xfs defaults,nosuid 1 2 /dev/mapper/lg_os-lv_var_tmp /var/tmp xfs defaults,nosuid,noexec,nodev 1 2 /dev/mapper/lg_os-lv_var_tmp /var/log xfs defaults,nosuid,noexec,nodev 1 2 /dev/mapper/lg_os-lv_var_tmp /var/log/audit xfs defaults,nosuid,noexec,nodev 1 2 /dev/mapper/lg_data-lv_var_www /var/www xfs defaults,nosuid,noexec,nodev 1 2 /dev/mapper/lg_data-lv_swap swap swap defaults 0 0
0x03 安装NTP服务
在进行一些合规性审计的时候NTP是必要的，同步时间有利于审计日志。
yum install ntp ntpdate
chkconfig ntpd on
ntpdate pool.ntp.org
/etc/init.d/ntpd start
0x04 配置完整性检查工具AIDE
Pre-linking binaries功能缩短了运行时间，然而这种方式会导致AIDE出现故障，所以配置AIDE之前需要禁止此项。打开/etc/sysconfig/prelink确保PRELINKING=no ，或者直接使用下面的脚本：
# Disable prelinking altogether
#
if grep -q ^PRELINKING /etc/sysconfig/prelink
then
sed -i 's/PRELINKING.*/PRELINKING=no/g' /etc/sysconfig/prelink
else
echo -e "\n# Set PRELINKING=no per security requirements" >> /etc/sysconfig/prelink
echo "PRELINKING=no" >> /etc/sysconfig/prelink
fi
Disable previous prelink changes to binaries:
Disable previous prelink changes to binaries
root:~# /usr/sbin/prelink -ua安装AIDE
yum install aide -y && /usr/sbin/aide --init && cp /var/lib/aide/aide.db.new.gz /var/lib/aide/aide.db.gz && /usr/sbin/aide --check
Configure periodic execution of AIDE, runs every morning at 04:30
echo "05 4 * * * root /usr/sbin/aide --check" >> /etc/crontab
0x05 阻止用户挂载USB
echo "install usb-storage /bin/false" > /etc/modprobe.d/usb-storage.conf
0x06 启用高强度的密码策略
下面这条命令将启用SHA512替代MD5
authconfig --passalgo=sha512 —update
0x07 配置密码策略pwquality.conf
vi /etc/security/pwquality.conf # Configuration for systemwide password quality limits # Defaults: # # Number of characters in the new password that must not be present in the # old password. difok = 5 # # Minimum acceptable size for the new password (plus one if # credits are not disabled which is the default). (See pam_cracklib manual.) # Cannot be set to lower value than 6. minlen = 14 # # The maximum credit for having digits in the new password. If less than 0 # it is the minimum number of digits in the new password. dcredit = 1 # # The maximum credit for having uppercase characters in the new password. # If less than 0 it is the minimum number of uppercase characters in the new # password. ucredit = 1 # # The maximum credit for having lowercase characters in the new password. # If less than 0 it is the minimum number of lowercase characters in the new # password. lcredit = 1 # # The maximum credit for having other characters in the new password. # If less than 0 it is the minimum number of other characters in the new # password. ocredit = 1 # # The minimum number of required classes of characters for the new # password (digits, uppercase, lowercase, others). minclass = 4 # # The maximum number of allowed consecutive same characters in the new password. # The check is disabled if the value is 0. maxrepeat = 3 # # The maximum number of allowed consecutive characters of the same class in the # new password. # The check is disabled if the value is 0. maxclassrepeat = 3 # # Whether to check for the words from the passwd entry GECOS string of the user. # The check is enabled if the value is not 0. gecoscheck = 1 # # Path to the cracklib dictionaries. Default is to use the cracklib default. # dictpath =
设置密码策略
Add the following to /etc/login.defs
PASS_MIN_LEN 14
PASS_MIN_DAYS 1
PASS_MAX_DAYS 60
0x08 设置提示上次登录信息
vim /etc/pam.d/system-auth
session required pam_lastlog.so showfailed
0x09 设置每个会话最大密码尝试次数
Set the amount of password reprompts per session, by editing the pam_pwquality.so statement in
vim /etc/pam.d/system-auth
auth pam_pwquality.so retry=3
0x0a 阻止错误密码尝试
编辑 /etc/pam.d/system-auth 和 /etc/pam.d/password-auth两个PAM配置文件
auth [default=die] pam_faillock.so authfail deny=3 unlock_time=604800 fail_interval=900
auth required pam_faillock.so authsucc deny=3 unlock_time=604800 fail_interval=900
0x0b 限制密码重用
使用PAM模块配置，在 /etc/pam.d/system-auth这个PAM配置文件里面，在pam_unix.so所在的行添加 remember=24 。这样服务器就会记录历史上的前24个旧密码，为啥为24？因为这是美国国防部的标准。
password sufficient pam_unix.so existing_options remember=24