mirror of
https://github.com/carlospolop/hacktricks
synced 2024-12-22 02:53:28 +00:00
68 lines
3.9 KiB
Markdown
68 lines
3.9 KiB
Markdown
|
|
|
|
{% hint style="success" %}
|
|
Learn & practice AWS Hacking:<img src="/.gitbook/assets/arte.png" alt="" data-size="line">[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)<img src="/.gitbook/assets/arte.png" alt="" data-size="line">\
|
|
Learn & practice GCP Hacking: <img src="/.gitbook/assets/grte.png" alt="" data-size="line">[**HackTricks Training GCP Red Team Expert (GRTE)**<img src="/.gitbook/assets/grte.png" alt="" data-size="line">](https://training.hacktricks.xyz/courses/grte)
|
|
|
|
<details>
|
|
|
|
<summary>Support HackTricks</summary>
|
|
|
|
* Check the [**subscription plans**](https://github.com/sponsors/carlospolop)!
|
|
* **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 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>
|
|
{% endhint %}
|
|
|
|
|
|
# Summary of the attack
|
|
|
|
Imagine a server which is **signing** some **data** by **appending** a **secret** to some known clear text data and then hashing that data. If you know:
|
|
|
|
* **The length of the secret** (this can be also bruteforced from a given length range)
|
|
* **The clear text data**
|
|
* **The algorithm (and it's vulnerable to this attack)**
|
|
* **The padding is known**
|
|
* Usually a default one is used, so if the other 3 requirements are met, this also is
|
|
* The padding vary depending on the length of the secret+data, that's why the length of the secret is needed
|
|
|
|
Then, it's possible for an **attacker** to **append** **data** and **generate** a valid **signature** for the **previous data + appended data**.
|
|
|
|
## How?
|
|
|
|
Basically the vulnerable algorithms generate the hashes by firstly **hashing a block of data**, and then, **from** the **previously** created **hash** (state), they **add the next block of data** and **hash it**.
|
|
|
|
Then, imagine that the secret is "secret" and the data is "data", the MD5 of "secretdata" is 6036708eba0d11f6ef52ad44e8b74d5b.\
|
|
If an attacker wants to append the string "append" he can:
|
|
|
|
* Generate a MD5 of 64 "A"s
|
|
* Change the state of the previously initialized hash to 6036708eba0d11f6ef52ad44e8b74d5b
|
|
* Append the string "append"
|
|
* Finish the hash and the resulting hash will be a **valid one for "secret" + "data" + "padding" + "append"**
|
|
|
|
## **Tool**
|
|
|
|
{% embed url="https://github.com/iagox86/hash_extender" %}
|
|
|
|
## References
|
|
|
|
You can find this attack good explained in [https://blog.skullsecurity.org/2012/everything-you-need-to-know-about-hash-length-extension-attacks](https://blog.skullsecurity.org/2012/everything-you-need-to-know-about-hash-length-extension-attacks)
|
|
|
|
|
|
{% hint style="success" %}
|
|
Learn & practice AWS Hacking:<img src="/.gitbook/assets/arte.png" alt="" data-size="line">[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)<img src="/.gitbook/assets/arte.png" alt="" data-size="line">\
|
|
Learn & practice GCP Hacking: <img src="/.gitbook/assets/grte.png" alt="" data-size="line">[**HackTricks Training GCP Red Team Expert (GRTE)**<img src="/.gitbook/assets/grte.png" alt="" data-size="line">](https://training.hacktricks.xyz/courses/grte)
|
|
|
|
<details>
|
|
|
|
<summary>Support HackTricks</summary>
|
|
|
|
* Check the [**subscription plans**](https://github.com/sponsors/carlospolop)!
|
|
* **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 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>
|
|
{% endhint %}
|
|
|
|
|