# AWS - Steal Lambda Requests {% hint style="success" %} Learn & practice AWS Hacking:[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)\ Learn & practice GCP Hacking: [**HackTricks Training GCP Red Team Expert (GRTE)**](https://training.hacktricks.xyz/courses/grte)
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{% endhint %} ## Lambda Flow

https://unit42.paloaltonetworks.com/wp-content/uploads/2019/10/lambda_poc_2_arch.png

1. **Slicer** is a process outside the container that **send** **invocations** to the **init** process. 2. The init process listens on port **9001** exposing some interesting endpoints: * **`/2018-06-01/runtime/invocation/next`** – get the next invocation event * **`/2018-06-01/runtime/invocation/{invoke-id}/response`** – return the handler response for the invoke * **`/2018-06-01/runtime/invocation/{invoke-id}/error`** – return an execution error 3. **bootstrap.py** has a loop getting invocations from the init process and calls the users code to handle them (**`/next`**). 4. Finally, **bootstrap.py** sends to init the **response** Note that bootstrap loads the user code as a module, so any code execution performed by the users code is actually happening in this process. ## Stealing Lambda Requests The goal of this attack is to make the users code execute a malicious **`bootstrap.py`** process inside the **`bootstrap.py`** process that handle the vulnerable request. This way, the **malicious bootstrap** process will start **talking with the init process** to handle the requests while the **legit** bootstrap is **trapped** running the malicious one, so it won't ask for requests to the init process. This is a simple task to achieve as the code of the user is being executed by the legit **`bootstrap.py`** process. So the attacker could: * **Send a fake result of the current invocation to the init process**, so init thinks the bootstrap process is waiting for more invocations. * A request must be sent to **`/${invoke-id}/response`** * The invoke-id can be obtained from the stack of the legit **`bootstrap.py`** process using the [**inspect**](https://docs.python.org/3/library/inspect.html) python module (as [proposed here](https://github.com/twistlock/lambda-persistency-poc/blob/master/poc/switch_runtime.py)) or just requesting it again to **`/2018-06-01/runtime/invocation/next`** (as [proposed here](https://github.com/Djkusik/serverless_persistency_poc/blob/master/gcp/exploit_files/switcher.py)). * Execute a malicious **`boostrap.py`** which will handle the next invocations * For stealthiness purposes it's possible to send the lambda invocations parameters to an attackers controlled C2 and then handle the requests as usual. * For this attack, it's enough to get the original code of **`bootstrap.py`** from the system or [**github**](https://github.com/aws/aws-lambda-python-runtime-interface-client/blob/main/awslambdaric/bootstrap.py), add the malicious code and run it from the current lambda invocation. ### Attack Steps 1. Find a **RCE** vulnerability. 2. Generate a **malicious** **bootstrap** (e.g. [https://raw.githubusercontent.com/carlospolop/lambda\_bootstrap\_switcher/main/backdoored\_bootstrap.py](https://raw.githubusercontent.com/carlospolop/lambda_bootstrap_switcher/main/backdoored_bootstrap.py)) 3. **Execute** the malicious bootstrap. You can easily perform these actions running: ```bash python3 <[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)\ Learn & practice GCP Hacking: [**HackTricks Training GCP Red Team Expert (GRTE)**](https://training.hacktricks.xyz/courses/grte)
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