背景

Github ActionsからSAMを実行するためにIAMを作成しようと思ったが、
最小限のポリシーにするうえで、情報がググってもなかなか出てこなかったので記事化。
（LambdaへのIAMロール付与の記事ばかりが出てくる。。。。）

最小限ポリシー

公式の記事があった。
（"Permission" でググるのが正解だったかも。）
https://docs.aws.amazon.com/ja_jp/serverless-application-model/latest/developerguide/sam-permissions.html

そちらに運用上＋αして以下に。

AutoPublishAlias に必要だったもの
- "lambda:ListVersionsByFunction"
- "lambda:PublishVersion"
- "lambda:UpdateAlias"
Layerの更新に必要だったもの
- "lambda:PublishLayerVersion"

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "CloudFormationTemplate",
            "Effect": "Allow",
            "Action": [
                "cloudformation:CreateChangeSet"
            ],
            "Resource": [
                "arn:aws:cloudformation:*:aws:transform/Serverless-2016-10-31"
            ]
        },
        {
            "Sid": "CloudFormationStack",
            "Effect": "Allow",
            "Action": [
                "cloudformation:CreateChangeSet",
                "cloudformation:DeleteStack",
                "cloudformation:DescribeChangeSet",
                "cloudformation:DescribeStackEvents",
                "cloudformation:DescribeStacks",
                "cloudformation:ExecuteChangeSet",
                "cloudformation:GetTemplateSummary"
            ],
            "Resource": [
                "arn:aws:cloudformation:*:111122223333:stack/*"
            ]
        },
        {
            "Sid": "S3",
            "Effect": "Allow",
            "Action": [
                "s3:CreateBucket",
                "s3:GetObject",
                "s3:PutObject"
            ],
            "Resource": [
                "arn:aws:s3:::*/*"
            ]
        },
        {
            "Sid": "ECRRepository",
            "Effect": "Allow",
            "Action": [
                "ecr:BatchCheckLayerAvailability",
                "ecr:BatchGetImage",
                "ecr:CompleteLayerUpload",
                "ecr:DescribeImages",
                "ecr:DescribeRepositories",
                "ecr:GetDownloadUrlForLayer",
                "ecr:GetRepositoryPolicy",
                "ecr:InitiateLayerUpload",
                "ecr:ListImages",
                "ecr:PutImage",
                "ecr:SetRepositoryPolicy",
                "ecr:UploadLayerPart"
            ],
            "Resource": [
                "arn:aws:ecr:*:111122223333:repository/*"
            ]
        },
        {
            "Sid": "ECRAuthToken",
            "Effect": "Allow",
            "Action": [
                "ecr:GetAuthorizationToken"
            ],
            "Resource": [
                "*"
            ]
        },
        {
            "Sid": "Lambda",
            "Effect": "Allow",
            "Action": [
                "lambda:AddPermission",
                "lambda:CreateFunction",
                "lambda:DeleteFunction",
                "lambda:GetFunction",
                "lambda:GetFunctionConfiguration",
                "lambda:ListTags",
                "lambda:RemovePermission",
                "lambda:TagResource",
                "lambda:UntagResource",
                "lambda:UpdateFunctionCode",
                "lambda:UpdateFunctionConfiguration",
                "lambda:ListVersionsByFunction",
                "lambda:PublishVersion",
                "lambda:UpdateAlias"
            ],
            "Resource": [
                "arn:aws:lambda:*:111122223333:function:*"
            ]
        },
        {
            "Sid": "LambdaLayer",
            "Effect": "Allow",
            "Action": [
                "lambda:GetLayerVersion",
                "lambda:PublishLayerVersion"
            ],
            "Resource": [
                "arn:aws:lambda:*:111122223333:layer:*"
            ]
        },
        {
            "Sid": "IAM",
            "Effect": "Allow",
            "Action": [
                "iam:AttachRolePolicy",
                "iam:DeleteRole",
                "iam:DetachRolePolicy",
                "iam:GetRole",
                "iam:PassRole",
                "iam:TagRole"
            ],
            "Resource": [
                "arn:aws:iam::111122223333:role/*"
            ]
        },
        {
            "Sid": "APIGateway",
            "Effect": "Allow",
            "Action": [
                "apigateway:DELETE",
                "apigateway:GET",
                "apigateway:PATCH",
                "apigateway:POST",
                "apigateway:PUT"
            ],
            "Resource": [
                "arn:aws:apigateway:*::*"
            ]
        }
    ]
}

Usage

111122223333 → 自身のAWSアカウントIDに
- Serverless-2016-10-31 はテンプレートバージョンなので、そのままでOK