Shulou(Shulou.com)05/31 Report--

Today, I will talk to you about how python calls jsDES encryption. Many people may not know much about it. In order to make you understand better, the editor has summarized the following for you. I hope you can get something according to this article.

Limitations of 0x00 burpsuite

In today's infiltration work, the black box test encountered a DES encrypted login mode, encountered a lot of holes, and finally started this station through python calling js for des encryption.

This time, when I tested the login, I found that the CAPTCHA could be reused when sending the login request, because the session value was not refreshed when the login failed, which led to the reuse of the CAPTCHA. The method of testing the reusability of the verification code is that the burpsuite grabs the login request packet and sends it to the repeater continuously gogogogo. If the prompt error is an error of the verification code, it means that the loophole does not exist, but the error of the account number or password means that the verification code can be reused.

Metz can be cracked by force, but seeing that the data of post is encrypted, why do I know it is DES encryption? The reason is to look closely at the source code of his html page. Found such a piece of javascript code.

FunctionencryptByDES (message, key) {

Var keyHex = CryptoJS.enc.Utf8.parse (key)

Var encrypted = CryptoJS.DES.encrypt (message, keyHex, {

Mode: CryptoJS.mode.ECB

Padding: CryptoJS.pad.Pkcs7

});

Return encrypted.toString ()

}

And found that the developer also wrote the encryption key into html, and saw that the des encryption function encryptByDES was called when the login request was sent.

The js of the page is always full of surprises. Let's get down to business and talk about my pythondes encryption crawl record.

First of all, my first reaction was to use burpsuite for paylaod to deal with brute force cracking.

Some of the md5 encryption encountered in the past, sha1 can deal with payload here, and then simply can carry out encryption brute force cracking.

But DES, RSA, AES and other encryption methods can not be found here, which is the limitation of burpsuite. Let's see what we can do to encrypt the password.

0x02 understands "DES encryption" in js

We understand the function he originally logged in, and we can call his encryption function directly from the console in browser F12. The encrypted content of login is this {"username": "admin", "password": "12345678"}

EncryptByDES ('{"username": "admin", "password": "12345678"}', '232cb85 / cd354')

It is found that the post parameter is the same as the login request package. But brute force cracking can never be entered like this over and over again.

0x03 pythonDES encryption module-- pydes

Then think about it again, see if python has DES encryption module, yes. Pydes module, there are two potholes.

This is the official template for using the pydes module.

Importbase64

FrompyDes import *

Des_Key= "12345678" # Key

Des_IV= "" # Custom IV Vector

DefDesEncrypt (str):

K = des (Des_Key, CBC, Des_IV, pad=None, padmode=PAD_PKCS5)

EncryptStr= k.encrypt (str)

Returnbase64.b64encode (EncryptStr) # returned by transferring base64 code

In the first pit, I found that this module is only encrypted in des's ECB and CBC modes, and the filling modes are only pkcs5padding and nomalpadding. What I need is pkcs7 paddingcake cake!

The second pit, normal des encryption key is always 8-bit, 3des encryption is 16-bit or 24-bit. However, what is given to me in the page source code is 64 bit! What a fat thing! But under another idea, go to online encryption to have a look.

0x04 Design DES encryption API

When it comes to online encryption, I found three websites, and the other two sites all reported key digit errors. It really takes 8 digits to do, but only this site can. Before the page source code, you can see that the js code DES encryption is in ECB mode, and it is filled with pkcs7_padding, and after encryption is the same as the encrypted data of the original login request package.

And see that his query packet is the content that post needs to encrypt and return the encrypted password, so plan to use python to write an encrypted api http request? Then extract the password and then violently crack the login.

It is indeed possible to encrypt and break violently in this way. But when I quickly replayed the packet using burpsuite, I found that this method was not feasible.

Unless requested once every 5 seconds. I do not know the account does not know the password, but also can not guess whether the user exists, this situation is not desirable. (if an existing user returns an incorrect password. When the user does not exist, the return account does not exist. You can guess whether the user exists according to the login result.

Api idea 2

Let's take a step back to the login page and see that when we visit the login page, a total of these additional js files are loaded.

Go in and take a look at the three js that are actually used for des encryption as shown below.

We can click on it and look at the response to see the js code, all of which are saved locally, and then we can write them into our own api.

This is a html page that saved their encrypted js and then wrote it themselves (js order should be correct)

Function encryptByDES (message, key) {

Var keyHex = CryptoJS.enc.Utf8.parse (key)

Var encrypted = CryptoJS.DES.encrypt (message, keyHex, {

Mode: CryptoJS.mode.ECB

Padding: CryptoJS.pad.Pkcs7

});

Return encrypted.toString ()

}

So you can write to a page of your own website to add input and output tags, and we can directly input and output encryption results, but this is not the best solution. In that case, you still have to request your own website to log in again. Efficiency is half lower than direct python encryption and then brute force cracking!

0x05 python calls js--execjs

Finally, I used a module that python can execute js code directly, which I believe is very useful except for the purpose of login encryption.

This module is called execjs, and then three encrypted js are superimposed into a file in order.

When the first encrypted function is like this, the encrypted js is read first.

Defget_js (): # this is the function to get js

F = open ('C:\ Users\\ 3s_NwGeek\ Desktop\\ des.js','r')

Line = f.readline ()

Htmlstr =''

Whileline:

Htmlstr = htmlstr+line

Line = f.readline ()

Returnhtmlstr

This is an encrypted function. First get the js, then parse the js code, then call the function of js and pass parameters to return the encrypted password.

DefDesEncrypt (str,key): # this is the function of des encryption

Jsstr= get_js () # get js

Ctx= execjs.compile (jsstr) # parsing js code

Password=ctx.call ('encryptByDES',str,key) # calls the encryptByDES function and passes the original str and encrypted key

Password= (password.encode ("unicode_escape"). Decode ("string_escape"). Decode ('unicode-escape'). Encode (' utf-8') # decoded, which is unicode.

Returnpassword

Encrypt with the original text, and the result returned is the same as the original request packet.

{"username": "admin", "password": "12345678"}

IKUJ1KTtfI4NqIHAf7QQha71W4vil4uLWR1YQREFkJLsx1W/aKLcnt9Ni7PalkpP

Later words of 0x06

Tips: finally, we directly use the cooperative process to crack it. In fact, in advance, I added the contacts and responsible persons of the infiltration research table, as well as the name information of the whole department, to make a user dictionary. For example, if the name is Zhang Sanfeng, then there will be zhangsanfeng,zhang_sanfeng,zhang_sf,zsf. Then made 16 users plus commonly used admin and root to crack the big dictionary violently.

The pit was drained for 5 hours and burst for 5 minutes.

Finally, trembling with excitement, he called out "yes!" Was

In fact, this station will be infiltrated by many manufacturers every month, but maybe pass this way when you see the password encrypted, but when you are willing to pay more patience than others, you will be able to see more scenery and dig more loopholes than others.

After reading the above, do you have any further understanding of how python calls jsDES encryption? If you want to know more knowledge or related content, please follow the industry information channel, thank you for your support.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.