mirror of
https://github.com/carlospolop/hacktricks
synced 2024-11-30 00:20:59 +00:00
104 lines
6.7 KiB
Markdown
104 lines
6.7 KiB
Markdown
|
|
|
|
<details>
|
|
|
|
<summary><strong>Learn AWS hacking from zero to hero with</strong> <a href="https://training.hacktricks.xyz/courses/arte"><strong>htARTE (HackTricks AWS Red Team Expert)</strong></a><strong>!</strong></summary>
|
|
|
|
Other ways to support HackTricks:
|
|
|
|
* If you want to see your **company advertised in HackTricks** or **download HackTricks in PDF** Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
|
|
* Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
|
|
* Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
|
|
* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@hacktricks_live**](https://twitter.com/hacktricks_live)**.**
|
|
* **Share your hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.
|
|
|
|
</details>
|
|
|
|
|
|
# ECB
|
|
|
|
(ECB) Electronic Code Book - symmetric encryption scheme which **replaces each block of the clear text** by the **block of ciphertext**. It is the **simplest** encryption scheme. The main idea is to **split** the clear text into **blocks of N bits** (depends on the size of the block of input data, encryption algorithm) and then to encrypt (decrypt) each block of clear text using the only key.
|
|
|
|
|
|
|
|
Using ECB has multiple security implications:
|
|
|
|
* **Blocks from encrypted message can be removed**
|
|
* **Blocks from encrypted message can be moved around**
|
|
|
|
# Detection of the vulnerability
|
|
|
|
Imagine you login into an application several times and you **always get the same cookie**. This is because the cookie of the application is **`<username>|<password>`**.\
|
|
Then, you generate to new users, both of them with the **same long password** and **almost** the **same** **username**.\
|
|
You find out that the **blocks of 8B** where the **info of both users** is the same are **equals**. Then, you imagine that this might be because **ECB is being used**.
|
|
|
|
Like in the following example. Observe how these** 2 decoded cookies** has several times the block **`\x23U\xE45K\xCB\x21\xC8`**
|
|
|
|
```
|
|
\x23U\xE45K\xCB\x21\xC8\x23U\xE45K\xCB\x21\xC8\x04\xB6\xE1H\xD1\x1E \xB6\x23U\xE45K\xCB\x21\xC8\x23U\xE45K\xCB\x21\xC8+=\xD4F\xF7\x99\xD9\xA9
|
|
|
|
\x23U\xE45K\xCB\x21\xC8\x23U\xE45K\xCB\x21\xC8\x04\xB6\xE1H\xD1\x1E \xB6\x23U\xE45K\xCB\x21\xC8\x23U\xE45K\xCB\x21\xC8+=\xD4F\xF7\x99\xD9\xA9
|
|
```
|
|
|
|
This is because the **username and password of those cookies contained several times the letter "a"** (for example). The **blocks** that are **different** are blocks that contained **at least 1 different character** (maybe the delimiter "|" or some necessary difference in the username).
|
|
|
|
Now, the attacker just need to discover if the format is `<username><delimiter><password>` or `<password><delimiter><username>`. For doing that, he can just **generate several usernames **with s**imilar and long usernames and passwords until he find the format and the length of the delimiter:**
|
|
|
|
| Username length: | Password length: | Username+Password length: | Cookie's length (after decoding): |
|
|
| ---------------- | ---------------- | ------------------------- | --------------------------------- |
|
|
| 2 | 2 | 4 | 8 |
|
|
| 3 | 3 | 6 | 8 |
|
|
| 3 | 4 | 7 | 8 |
|
|
| 4 | 4 | 8 | 16 |
|
|
| 7 | 7 | 14 | 16 |
|
|
|
|
# Exploitation of the vulnerability
|
|
|
|
## Removing entire blocks
|
|
|
|
Knowing the format of the cookie (`<username>|<password>`), in order to impersonate the username `admin` create a new user called `aaaaaaaaadmin` and get the cookie and decode it:
|
|
|
|
```
|
|
\x23U\xE45K\xCB\x21\xC8\xE0Vd8oE\x123\aO\x43T\x32\xD5U\xD4
|
|
```
|
|
|
|
We can see the pattern `\x23U\xE45K\xCB\x21\xC8` created previously with the username that contained only `a`.\
|
|
Then, you can remove the first block of 8B and you will et a valid cookie for the username `admin`:
|
|
|
|
```
|
|
\xE0Vd8oE\x123\aO\x43T\x32\xD5U\xD4
|
|
```
|
|
|
|
## Moving blocks
|
|
|
|
In many databases it is the same to search for `WHERE username='admin';` or for `WHERE username='admin ';` _(Note the extra spaces)_
|
|
|
|
So, another way to impersonate the user `admin` would be to:
|
|
|
|
* Generate a username that: `len(<username>) + len(<delimiter) % len(block)`. With a block size of `8B` you can generate username called: `username `, with the delimiter `|` the chunk `<username><delimiter>` will generate 2 blocks of 8Bs.
|
|
* Then, generate a password that will fill an exact number of blocks containing the username we want to impersonate and spaces, like: `admin `
|
|
|
|
The cookie of this user is going to be composed by 3 blocks: the first 2 is the blocks of the username + delimiter and the third one of the password (which is faking the username): `username |admin `
|
|
|
|
**Then, just replace the first block with the last time and will be impersonating the user `admin`: `admin |username`**
|
|
|
|
## References
|
|
|
|
* [http://cryptowiki.net/index.php?title=Electronic_Code_Book\_(ECB)](http://cryptowiki.net/index.php?title=Electronic_Code_Book_\(ECB\))
|
|
|
|
|
|
<details>
|
|
|
|
<summary><strong>Learn AWS hacking from zero to hero with</strong> <a href="https://training.hacktricks.xyz/courses/arte"><strong>htARTE (HackTricks AWS Red Team Expert)</strong></a><strong>!</strong></summary>
|
|
|
|
Other ways to support HackTricks:
|
|
|
|
* If you want to see your **company advertised in HackTricks** or **download HackTricks in PDF** Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
|
|
* Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
|
|
* Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
|
|
* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@hacktricks_live**](https://twitter.com/hacktricks_live)**.**
|
|
* **Share your hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.
|
|
|
|
</details>
|
|
|
|
|