# GCP - IAM Privesc {% 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 %} ## IAM Find more information about IAM in: {% content-ref url="../gcp-services/gcp-iam-and-org-policies-enum.md" %} [gcp-iam-and-org-policies-enum.md](../gcp-services/gcp-iam-and-org-policies-enum.md) {% endcontent-ref %} ### `iam.roles.update` (`iam.roles.get`) An attacker with the mentioned permissions will be able to update a role assigned to you and give you extra permissions to other resources like: ```bash gcloud iam roles update --project --add-permissions ``` You can find a script to automate the **creation, exploit and cleaning of a vuln environment here** and a python script to abuse this privilege [**here**](https://github.com/RhinoSecurityLabs/GCP-IAM-Privilege-Escalation/blob/master/ExploitScripts/iam.roles.update.py). For more information check the [**original research**](https://rhinosecuritylabs.com/gcp/privilege-escalation-google-cloud-platform-part-1/). ### `iam.serviceAccounts.getAccessToken` (`iam.serviceAccounts.get`) An attacker with the mentioned permissions will be able to **request an access token that belongs to a Service Account**, so it's possible to request an access token of a Service Account with more privileges than ours. ```bash gcloud --impersonate-service-account="${victim}@${PROJECT_ID}.iam.gserviceaccount.com" \ auth print-access-token ``` You can find a script to automate the [**creation, exploit and cleaning of a vuln environment here**](https://github.com/carlospolop/gcp_privesc_scripts/blob/main/tests/4-iam.serviceAccounts.getAccessToken.sh) and a python script to abuse this privilege [**here**](https://github.com/RhinoSecurityLabs/GCP-IAM-Privilege-Escalation/blob/master/ExploitScripts/iam.serviceAccounts.getAccessToken.py). For more information check the [**original research**](https://rhinosecuritylabs.com/gcp/privilege-escalation-google-cloud-platform-part-1/). ### `iam.serviceAccountKeys.create` An attacker with the mentioned permissions will be able to **create a user-managed key for a Service Account**, which will allow us to access GCP as that Service Account. ```bash gcloud iam service-accounts keys create --iam-account /tmp/key.json gcloud auth activate-service-account --key-file=sa_cred.json ``` You can find a script to automate the [**creation, exploit and cleaning of a vuln environment here**](https://github.com/carlospolop/gcp_privesc_scripts/blob/main/tests/3-iam.serviceAccountKeys.create.sh) and a python script to abuse this privilege [**here**](https://github.com/RhinoSecurityLabs/GCP-IAM-Privilege-Escalation/blob/master/ExploitScripts/iam.serviceAccountKeys.create.py). For more information check the [**original research**](https://rhinosecuritylabs.com/gcp/privilege-escalation-google-cloud-platform-part-1/). Note that **`iam.serviceAccountKeys.update` won't work to modify the key** of a SA because to do that the permissions `iam.serviceAccountKeys.create` is also needed. ### `iam.serviceAccounts.implicitDelegation` If you have the **`iam.serviceAccounts.implicitDelegation`** permission on a Service Account that has the **`iam.serviceAccounts.getAccessToken`** permission on a third Service Account, then you can use implicitDelegation to **create a token for that third Service Account**. Here is a diagram to help explain. ![](https://rhinosecuritylabs.com/wp-content/uploads/2020/04/image2-500x493.png) Note that according to the [**documentation**](https://cloud.google.com/iam/docs/understanding-service-accounts), the delegation of `gcloud` only works to generate a token using the [**generateAccessToken()**](https://cloud.google.com/iam/credentials/reference/rest/v1/projects.serviceAccounts/generateAccessToken) method. So here you have how to get a token using the API directly: ```bash curl -X POST \ 'https://iamcredentials.googleapis.com/v1/projects/-/serviceAccounts/'"${TARGET_SERVICE_ACCOUNT}"':generateAccessToken' \ -H 'Content-Type: application/json' \ -H 'Authorization: Bearer '"$(gcloud auth print-access-token)" \ -d '{ "delegates": ["projects/-/serviceAccounts/'"${DELEGATED_SERVICE_ACCOUNT}"'"], "scope": ["https://www.googleapis.com/auth/cloud-platform"] }' ``` You can find a script to automate the [**creation, exploit and cleaning of a vuln environment here**](https://github.com/carlospolop/gcp_privesc_scripts/blob/main/tests/5-iam.serviceAccounts.implicitDelegation.sh) and a python script to abuse this privilege [**here**](https://github.com/RhinoSecurityLabs/GCP-IAM-Privilege-Escalation/blob/master/ExploitScripts/iam.serviceAccounts.implicitDelegation.py). For more information check the [**original research**](https://rhinosecuritylabs.com/gcp/privilege-escalation-google-cloud-platform-part-1/). ### `iam.serviceAccounts.signBlob` An attacker with the mentioned permissions will be able to **sign of arbitrary payloads in GCP**. So it'll be possible to **create an unsigned JWT of the SA and then send it as a blob to get the JWT signed** by the SA we are targeting. For more information [**read this**](https://medium.com/google-cloud/using-serviceaccountactor-iam-role-for-account-impersonation-on-google-cloud-platform-a9e7118480ed). You can find a script to automate the [**creation, exploit and cleaning of a vuln environment here**](https://github.com/carlospolop/gcp_privesc_scripts/blob/main/tests/6-iam.serviceAccounts.signBlob.sh) and a python script to abuse this privilege [**here**](https://github.com/RhinoSecurityLabs/GCP-IAM-Privilege-Escalation/blob/master/ExploitScripts/iam.serviceAccounts.signBlob-accessToken.py) and [**here**](https://github.com/RhinoSecurityLabs/GCP-IAM-Privilege-Escalation/blob/master/ExploitScripts/iam.serviceAccounts.signBlob-gcsSignedUrl.py). For more information check the [**original research**](https://rhinosecuritylabs.com/gcp/privilege-escalation-google-cloud-platform-part-1/). ### `iam.serviceAccounts.signJwt` An attacker with the mentioned permissions will be able to **sign well-formed JSON web tokens (JWTs)**. The difference with the previous method is that **instead of making google sign a blob containing a JWT, we use the signJWT method that already expects a JWT**. This makes it easier to use but you can only sign JWT instead of any bytes. You can find a script to automate the [**creation, exploit and cleaning of a vuln environment here**](https://github.com/carlospolop/gcp_privesc_scripts/blob/main/tests/7-iam.serviceAccounts.signJWT.sh) and a python script to abuse this privilege [**here**](https://github.com/RhinoSecurityLabs/GCP-IAM-Privilege-Escalation/blob/master/ExploitScripts/iam.serviceAccounts.signJWT.py). For more information check the [**original research**](https://rhinosecuritylabs.com/gcp/privilege-escalation-google-cloud-platform-part-1/). ### `iam.serviceAccounts.setIamPolicy` An attacker with the mentioned permissions will be able to **add IAM policies to service accounts**. You can abuse it to **grant yourself** the permissions you need to impersonate the service account. In the following example we are granting ourselves the `roles/iam.serviceAccountTokenCreator` role over the interesting SA: ```bash gcloud iam service-accounts add-iam-policy-binding "${VICTIM_SA}@${PROJECT_ID}.iam.gserviceaccount.com" \ --member="user:username@domain.com" \ --role="roles/iam.serviceAccountTokenCreator" # If you still have prblem grant yourself also this permission gcloud iam service-accounts add-iam-policy-binding "${VICTIM_SA}@${PROJECT_ID}.iam.gserviceaccount.com" \ \ --member="user:username@domain.com" \ --role="roles/iam.serviceAccountUser" ``` You can find a script to automate the [**creation, exploit and cleaning of a vuln environment here**](https://github.com/carlospolop/gcp_privesc_scripts/blob/main/tests/d-iam.serviceAccounts.setIamPolicy.sh)**.** ### `iam.serviceAccounts.actAs` The **iam.serviceAccounts.actAs permission** is like the **iam:PassRole permission from AWS**. It's essential for executing tasks, like initiating a Compute Engine instance, as it grants the ability to "actAs" a Service Account, ensuring secure permission management. Without this, users might gain undue access. Additionally, exploiting the **iam.serviceAccounts.actAs** involves various methods, each requiring a set of permissions, contrasting with other methods that need just one. #### Service account impersonation Impersonating a service account can be very useful to **obtain new and better privileges**. There are three ways in which you can [impersonate another service account](https://cloud.google.com/iam/docs/understanding-service-accounts#impersonating_a_service_account): * Authentication **using RSA private keys** (covered above) * Authorization **using Cloud IAM policies** (covered here) * **Deploying jobs on GCP services** (more applicable to the compromise of a user account) ### `iam.serviceAccounts.getOpenIdToken` An attacker with the mentioned permissions will be able to generate an OpenID JWT. These are used to assert identity and do not necessarily carry any implicit authorization against a resource. According to this [**interesting post**](https://medium.com/google-cloud/authenticating-using-google-openid-connect-tokens-e7675051213b), it's necessary to indicate the audience (service where you want to use the token to authenticate to) and you will receive a JWT signed by google indicating the service account and the audience of the JWT. You can generate an OpenIDToken (if you have the access) with: ```bash # First activate the SA with iam.serviceAccounts.getOpenIdToken over the other SA gcloud auth activate-service-account --key-file=/path/to/svc_account.json # Then, generate token gcloud auth print-identity-token "${ATTACK_SA}@${PROJECT_ID}.iam.gserviceaccount.com" --audiences=https://example.com ``` Then you can just use it to access the service with: ```bash curl -v -H "Authorization: Bearer id_token" https://some-cloud-run-uc.a.run.app ``` Some services that support authentication via this kind of tokens are: * [Google Cloud Run](https://cloud.google.com/run/) * [Google Cloud Functions](https://cloud.google.com/functions/docs/) * [Google Identity Aware Proxy](https://cloud.google.com/iap/docs/authentication-howto) * [Google Cloud Endpoints](https://cloud.google.com/endpoints/docs/openapi/authenticating-users-google-id) (if using Google OIDC) You can find an example on how to create and OpenID token behalf a service account [**here**](https://github.com/carlospolop-forks/GCP-IAM-Privilege-Escalation/blob/master/ExploitScripts/iam.serviceAccounts.getOpenIdToken.py). ## References * [https://rhinosecuritylabs.com/gcp/privilege-escalation-google-cloud-platform-part-1/](https://rhinosecuritylabs.com/gcp/privilege-escalation-google-cloud-platform-part-1/) {% 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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