AWSTemplateFormatVersion: "2010-09-09"
Description: AWS resources for building and storing a nitro enclave image file in an external S3 bucket

Parameters:
  CodeCommitRepositoryName:
    Type: String
    Description: CodeCommit repository name that contains the server application files
    MinLength: 1

  ExternalBucketName:
    Type: String
    Description: S3 bucket name to use for sharing files
    MinLength: 1

  ExternalBucketPath:
    Type: String
    Description: S3 path inside bucket where to store the nitro enclave image
    MinLength: 1
    Default: "enclave"

  ExternalBucketEncryptionKeyArn:
    Type: String
    Description: ARN for the external bucket encryption key
    MinLength: 1

  ExternalBucketAWSAccountNumber:
    Type: String
    Description: AWS account number
    MinLength: 12
    MaxLength: 12
    AllowedPattern: "[0-9]+"

Resources:
  CodeBuildRole:
    Type: AWS::IAM::Role
    Metadata:
      cfn_nag:
        rules_to_suppress:
          - id: W11
            reason: "Asterisks are required"
    Properties:
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
          - Effect: Allow
            Principal:
              Service:
                - codebuild.amazonaws.com
            Action:
              - sts:AssumeRole
      Policies:
        - PolicyName: CodeBuildPolicy
          PolicyDocument:
            Version: "2012-10-17"
            Statement:
              - Sid: CloudWatchLogsPolicy
                Effect: Allow
                Action:
                  - logs:CreateLogGroup
                  - logs:CreateLogStream
                  - logs:PutLogEvents
                Resource:
                  - "*"
              - Sid: CodeCommitPolicy
                Effect: Allow
                Action:
                  - "codecommit:GitPull"
                Resource:
                  - !Sub "arn:aws:codecommit:${AWS::Region}:${AWS::AccountId}:${CodeCommitRepositoryName}"
              - Sid: S3WritePolicy
                Effect: Allow
                Action:
                  - s3:PutObject
                  - s3:PutObjectAcl
                Resource:
                  - !Sub "arn:aws:s3:::${ExternalBucketName}/*"
              - Sid: KMSPolicy
                Effect: Allow
                Action:
                  - kms:GetKeyPolicy
                  - kms:PutKeyPolicy
                Resource:
                  - !ImportValue EnclaveKeyARN
              - Sid: KMSAccessPolicyExternalKey
                Effect: Allow
                Action:
                  - kms:Decrypt
                  - kms:GenerateDataKey
                Resource:
                  - !Ref ExternalBucketEncryptionKeyArn

  CodeBuildProject:
    Type: AWS::CodeBuild::Project
    Metadata:
      cfn_nag:
        rules_to_suppress:
          - id: W32
            reason: "No build output artifacts to encrypt"
    Properties:
      Name: nitro-image-builder
      Description: The project generates an enclave image file and uploads it to the provided target location. It also updates the KMS key resource policy to restrict decryption using the enclave's security attestation.
      ServiceRole: !GetAtt CodeBuildRole.Arn
      Artifacts:
        Type: NO_ARTIFACTS
      Environment:
        ComputeType: BUILD_GENERAL1_LARGE
        Type: ARM_CONTAINER
        Image: "aws/codebuild/amazonlinux2-aarch64-standard:2.0"
        PrivilegedMode: true
        EnvironmentVariables:
          - Name: ENCLAVE_KEY_ARN
            Value: !ImportValue EnclaveKeyARN
      Source:
        BuildSpec: !Sub |
            version: 0.2
            phases:
              install:
                commands:
                  - "echo 'Installing required packages'"
                  - "PYTHON=python2 amazon-linux-extras install -y aws-nitro-enclaves-cli"
                  - "yum install aws-nitro-enclaves-cli-devel -y"
              build:
                commands:
                  - "echo 'Building enclave base image'"
                  - "docker build -t enclavebase containers/enclave_base"
                  - "echo 'Building enclave app image (Nitro) from enclave base'"
                  - "nitro-cli build-enclave --docker-uri enclaveapp --docker-dir containers/enclave_app --output-file nitro-enclave-image.eif > nitro_output.txt"
                  - "echo 'Writing enclave image file to the S3 bucket specified'"
                  - "aws s3api put-object --bucket ${ExternalBucketName} --key ${ExternalBucketPath}/nitro-enclave-image.eif --body nitro-enclave-image.eif --expected-bucket-owner ${ExternalBucketAWSAccountNumber} --acl bucket-owner-full-control --server-side-encryption aws:kms --ssekms-key-id ${ExternalBucketEncryptionKeyArn}"
              post_build:
                commands:
                  - "echo 'Updating key policy to allow enclave to decrypt with it'"
                  - "aws kms get-key-policy --key-id $ENCLAVE_KEY_ARN --policy-name default --region ${AWS::Region} --query Policy --output text > key_policy.txt"
                  - "sed -Ei.tmp 's/\"kms:RecipientAttestation:ImageSha384\" :.*/\"kms:RecipientAttestation:ImageSha384\" : '\"$(cat nitro_output.txt | jq '.[] | .PCR0')/g\" key_policy.txt"
                  - "aws kms put-key-policy --key-id $ENCLAVE_KEY_ARN --policy-name default --region ${AWS::Region} --policy file://key_policy.txt"
        Type: CODECOMMIT
        Location: !Sub "https://git-codecommit.${AWS::Region}.amazonaws.com/v1/repos/${CodeCommitRepositoryName}"