hacktricks/cloud-security/gcp-security/gcp-serverless-code-exec-services-enumeration.md
2022-05-01 13:41:36 +01:00

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# Cloud Functions <a href="reviewing-cloud-functions" id="reviewing-cloud-functions"></a>
Google [Cloud Functions](https://cloud.google.com/functions/) allow you to host code that is executed when an event is triggered, without the requirement to manage a host operating system. These functions can also store environment variables to be used by the code.
```bash
# List functions
gcloud functions list
# Get function config including env variables
gcloud functions describe [FUNCTION NAME]
# Get logs of previous runs
# By default, limits to 10 lines
gcloud functions logs read [FUNCTION NAME] --limit [NUMBER]
```
## Enumerate Open Cloud Functions
With the following code [taken from here](https://gitlab.com/gitlab-com/gl-security/security-operations/gl-redteam/gcp\_misc/-/blob/master/find\_open\_functions.sh) you can find Cloud Functions that permit unauthenticated invocations.
```bash
#!/bin/bash
############################
# Run this tool to find Cloud Functions that permit unauthenticated invocations
# anywhere in your GCP organization.
# Enjoy!
############################
for proj in $(gcloud projects list --format="get(projectId)"); do
echo "[*] scraping project $proj"
enabled=$(gcloud services list --project "$proj" | grep "Cloud Functions API")
if [ -z "$enabled" ]; then
continue
fi
for func_region in $(gcloud functions list --quiet --project "$proj" --format="value[separator=','](NAME,REGION)"); do
# drop substring from first occurence of "," to end of string.
func="${func_region%%,*}"
# drop substring from start of string up to last occurence of ","
region="${func_region##*,}"
ACL="$(gcloud functions get-iam-policy "$func" --project "$proj" --region "$region")"
all_users="$(echo "$ACL" | grep allUsers)"
all_auth="$(echo "$ACL" | grep allAuthenticatedUsers)"
if [ -z "$all_users" ]
then
:
else
echo "[!] Open to all users: $proj: $func"
fi
if [ -z "$all_auth" ]
then
:
else
echo "[!] Open to all authenticated users: $proj: $func"
fi
done
done
```
# App Engine Configurations <a href="reviewing-app-engine-configurations" id="reviewing-app-engine-configurations"></a>
Google [App Engine](https://cloud.google.com/appengine/) is another ["serverless"](https://about.gitlab.com/topics/serverless/) offering for hosting applications, with a focus on scalability. As with Cloud Functions, **there is a chance that the application will rely on secrets that are accessed at run-time via environment variables**. These variables are stored in an `app.yaml` file which can be accessed as follows:
```bash
# First, get a list of all available versions of all services
gcloud app versions list
# Then, get the specific details on a given app
gcloud app describe [APP]
```
# Cloud Run Configurations <a href="reviewing-cloud-run-configurations" id="reviewing-cloud-run-configurations"></a>
Google [Cloud Run](https://cloud.google.com/run) is another serverless offer where you can search for env variables also. Cloud Run creates a small web server, running on port 8080, that sits around waiting for an HTTP GET request. When the request is received, a job is executed and the job log is output via an HTTP response.
The access to this web server might be public of managed via IAM permissions:
```bash
# First get a list of services across the available platforms
gcloud run services list --platform=managed
gcloud run services list --platform=gke
# To learn more, export as JSON and investigate what the services do
gcloud run services list --platform=managed --format=json
gcloud run services list --platform=gke --format=json
# Attempt to trigger a job unauthenticated
curl [URL]
# Attempt to trigger a job with your current gcloud authorization
curl -H \
"Authorization: Bearer $(gcloud auth print-identity-token)" \
[URL]
```
## Enumerate Open CloudRun
With the following code [taken from here](https://gitlab.com/gitlab-com/gl-security/security-operations/gl-redteam/gcp\_misc/-/blob/master/find\_open\_cloudrun.sh) you can find Cloud Run services that permit unauthenticated invocations.
```bash
#!/bin/bash
############################
# Run this tool to find Cloud Run services that permit unauthenticated
# invocations anywhere in your GCP organization.
# Enjoy!
############################
for proj in $(gcloud projects list --format="get(projectId)"); do
echo "[*] scraping project $proj"
enabled=$(gcloud services list --project "$proj" | grep "Cloud Run API")
if [ -z "$enabled" ]; then
continue
fi
for run in $(gcloud run services list --platform managed --quiet --project $proj --format="get(name)"); do
ACL="$(gcloud run services get-iam-policy $run --platform managed --project $proj)"
all_users="$(echo $ACL | grep allUsers)"
all_auth="$(echo $ACL | grep allAuthenticatedUsers)"
if [ -z "$all_users" ]
then
:
else
echo "[!] Open to all users: $proj: $run"
fi
if [ -z "$all_auth" ]
then
:
else
echo "[!] Open to all authenticated users: $proj: $run"
fi
done
done
```
# References
* [https://about.gitlab.com/blog/2020/02/12/plundering-gcp-escalating-privileges-in-google-cloud-platform/#reviewing-stackdriver-logging](https://about.gitlab.com/blog/2020/02/12/plundering-gcp-escalating-privileges-in-google-cloud-platform/#reviewing-stackdriver-logging)
<details>
<summary><strong>Support HackTricks and get benefits!</strong></summary>
Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
**Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/carlospolopm)**.**
**Share your hacking tricks submitting PRs to the** [**hacktricks github repo**](https://github.com/carlospolop/hacktricks)**.**
</details>