Execute Terraform apply with AWS assume role

Question

I need to execute a Terraform template to provision infrastructure for an AWS account which I can access by assuming a role.

The problem I have now is I do not have an IAM user in that AWS account so I do not have an aws_access_key_id or an aws_secret_access_key to set up another named profile in my ~/.aws/credentials. When I run command terraform apply, the template creates the infrastructure for my account, not the other account.

How to run Terraform template using your account which has a role to access services of another AWS account?

Here's my Terraform file:

# Input variables
variable "aws_region" {
    type = "string"
    default = "us-east-1"
}

variable "pipeline_name" {
    type = "string"
    default = "static-website-terraform"
}

variable "github_username" {
    type = "string"
    default = "COMPANY"
}

variable "github_token" {
    type = "string"
}

variable "github_repo" {
    type = "string"
}

provider "aws" {
    region = "${var.aws_region}"
    assume_role {
        role_arn = "arn:aws:iam::<AWS-ACCOUNT-ID>:role/admin"
        profile = "default"
    }
}

# CodePipeline resources
resource "aws_s3_bucket" "build_artifact_bucket" {
    bucket = "${var.pipeline_name}-artifact-bucket"
    acl = "private"
}

data "aws_iam_policy_document" "codepipeline_assume_policy" {
    statement {
        effect = "Allow"
        actions = ["sts:AssumeRole"]

        principals {
            type = "Service"
            identifiers = ["codepipeline.amazonaws.com"]
        }
    }
}

resource "aws_iam_role" "codepipeline_role" {
    name = "${var.pipeline_name}-codepipeline-role"
    assume_role_policy = "${data.aws_iam_policy_document.codepipeline_assume_policy.json}"
}

# CodePipeline policy needed to use CodeCommit and CodeBuild
resource "aws_iam_role_policy" "attach_codepipeline_policy" {
    name = "${var.pipeline_name}-codepipeline-policy"
    role = "${aws_iam_role.codepipeline_role.id}"

    policy = <<EOF
{
    "Statement": [
        {
            "Action": [
                "s3:GetObject",
                "s3:GetObjectVersion",
                "s3:GetBucketVersioning",
                "s3:PutObject"
            ],
            "Resource": "*",
            "Effect": "Allow"
        },
        {
            "Action": [
                "cloudwatch:*",
                "sns:*",
                "sqs:*",
                "iam:PassRole"
            ],
            "Resource": "*",
            "Effect": "Allow"
        },
        {
            "Action": [
                "codebuild:BatchGetBuilds",
                "codebuild:StartBuild"
            ],
            "Resource": "*",
            "Effect": "Allow"
        }
    ],
    "Version": "2012-10-17"
}
EOF
}

# CodeBuild IAM Permissions
resource "aws_iam_role" "codebuild_assume_role" {
    name = "${var.pipeline_name}-codebuild-role"

    assume_role_policy = <<EOF
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "Service": "codebuild.amazonaws.com"
            },
            "Action": "sts:AssumeRole"
        }
    ]
}
EOF
}

resource "aws_iam_role_policy" "codebuild_policy" {
    name = "${var.pipeline_name}-codebuild-policy"
    role = "${aws_iam_role.codebuild_assume_role.id}"

    policy = <<POLICY
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "s3:PutObject",
                "s3:GetObject",
                "s3:GetObjectVersion",
                "s3:GetBucketVersioning"
            ],
            "Resource": "*",
            "Effect": "Allow"
        },
        {
            "Effect": "Allow",
            "Resource": [
                "${aws_codebuild_project.build_project.id}"
            ],
            "Action": [
                "codebuild:*"
            ]
        },
        {
            "Effect": "Allow",
            "Resource": [
                "*"
            ],
            "Action": [
                "logs:CreateLogGroup",
                "logs:CreateLogStream",
                "logs:PutLogEvents"
            ]
        }
    ]
}
POLICY
}

# CodeBuild Section for the Package stage
resource "aws_codebuild_project" "build_project" {
    name = "${var.pipeline_name}-build"
    description = "The CodeBuild project for ${var.pipeline_name}"
    service_role = "${aws_iam_role.codebuild_assume_role.arn}"
    build_timeout = "60"

    artifacts {
        type = "CODEPIPELINE"
    }

    environment {
        compute_type = "BUILD_GENERAL1_SMALL"
        image = "aws/codebuild/nodejs:6.3.1"
        type = "LINUX_CONTAINER"
    }

    source {
        type = "CODEPIPELINE"
        buildspec = "buildspec.yml"
    }
}

# Full CodePipeline
resource "aws_codepipeline" "codepipeline" {
    name = "${var.pipeline_name}-codepipeline"
    role_arn = "${aws_iam_role.codepipeline_role.arn}"

    artifact_store = {
        location = "${aws_s3_bucket.build_artifact_bucket.bucket}"
        type     = "S3"
    }

    stage {
        name = "Source"

        action {
            name = "Source"
            category = "Source"
            owner = "ThirdParty"
            provider = "GitHub"
            version = "1"
            output_artifacts = ["SourceArtifact"]

            configuration {
                Owner = "${var.github_username}"
                OAuthToken = "${var.github_token}"
                Repo = "${var.github_repo}"
                Branch = "master"
                PollForSourceChanges = "true"
            }
        }
    }

    stage {
        name = "Deploy"

        action {
            name = "DeployToS3"
            category = "Test"
            owner = "AWS"
            provider = "CodeBuild"
            input_artifacts = ["SourceArtifact"]
            output_artifacts = ["OutputArtifact"]
            version = "1"

            configuration {
                ProjectName = "${aws_codebuild_project.build_project.name}"
            }
        }
    }
}

Update:

Following Darren's answer (it makes a lot of sense) below, I added:

provider "aws" {
  region                  = "us-east-1"
  shared_credentials_file = "${pathexpand("~/.aws/credentials")}"
  profile                 = "default"

  assume_role {
    role_arn = "arn:aws:iam::<OTHER-ACCOUNT>:role/<ROLE-NAME>"
  }
}

However, I ran into this error:

• provider.aws: The role "arn:aws:iam:::role/" cannot be assumed.

  There are a number of possible causes of this - the most common are:

  • The credentials used in order to assume the role are invalid
  • The credentials do not have appropriate permission to assume the role
  • The role ARN is not valid

I've checked the role in the other account and I can switch to that role using the AWS Console from my account. I've also checked AWS guide here

So: that role ARN is valid, I do have credentials to assume the role and all the permissions I need to run the stack.

Update

I've also tried with a new role that has all access to services. However, I ran into this error:

Error: Error refreshing state: 2 error(s) occurred:

    * aws_codebuild_project.build_project: 1 error(s) occurred:

    * aws_codebuild_project.build_project: aws_codebuild_project.build_project: Error retreiving Projects:

"InvalidInputException: Invalid project ARN: account ID does not match caller's account\n\tstatus code: 400, request id: ..." * aws_s3_bucket.build_artifact_bucket: 1 error(s) occurred:

    * aws_s3_bucket.build_artifact_bucket: aws_s3_bucket.build_artifact_bucket: error getting S3 Bucket CORS

configuration: AccessDenied: Access Denied status code: 403, request id: ..., host id: ...

=====

UPDATE 29 Apr 2019:

Following @Rolando's suggestion, I've added this policy to the user of the MAIN ACCOUNT that I'm trying to use to assume the role of the OTHER ACCOUNT where I'm planning to execute terraform apply.

{
    "Version": "2012-10-17",
    "Statement": {
        "Effect": "Allow",
        "Action": "sts:AssumeRole",
        "Resource": "arn:aws:iam::<OTHER-ACCOUNT-ID>:role/admin"
    }
}

This is the Trust Relationship of the role admin belongs to the OTHER ACCOUNT:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "AWS": "arn:aws:iam::<MAIN_ACCOUNT_ID>:root"
      },
      "Action": "sts:AssumeRole",
      "Condition": {
        "Bool": {
          "aws:MultiFactorAuthPresent": "true"
        }
      }
    }
  ]
}

However, when I ran this command:

aws sts assume-role --role-arn arn:aws:iam::<OTHER-ACCOUNT-ID>:role/admin --role-session-name "RoleSession1" --profile default > assume-role-output.txt

I have this error:

An error occurred (AccessDenied) when calling the AssumeRole operation: Access denied

Solution 1

I have a bulletproof solution anytime you want to run commands as a specific role (including other accounts). I assume you have the AWS CLI tools installed. You will also have to install jq (easy tool to parse and extract data from json), although you can parse the data any way you wish.

aws_credentials=$(aws sts assume-role --role-arn arn:aws:iam::1234567890:role/nameOfMyrole --role-session-name "RoleSession1")

export AWS_ACCESS_KEY_ID=$(echo $aws_credentials|jq '.Credentials.AccessKeyId'|tr -d '"')
export AWS_SECRET_ACCESS_KEY=$(echo $aws_credentials|jq '.Credentials.SecretAccessKey'|tr -d '"')
export AWS_SESSION_TOKEN=$(echo $aws_credentials|jq '.Credentials.SessionToken'|tr -d '"')

First line assigns the response from the aws sts command and puts it in a variable. Last 3 lines will select the values from the first command and assigned them to variables that the aws cli uses.

Considerations:

If you create a bash script, add your terraform commands there as well. You can also just create a bash with the lines above, and run it with a '.' in front (ie: . ./get-creds.sh). This will create the variables on your current bash shell.

Role expires, keep in mind that roles have expiration of usually an hour.

Your shell will now have the three variables AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_SESSION_TOKEN. This means that it will override your ~/.aws/credentials. Easiest thing to do to clear this is to just start a new bash session.

I used this article as my source to figure this out: https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_temp_use-resources.html

Solution 2

You should be able to do it like this: In Terraform configure the aws provider to use your local shared_credentials_file

provider "aws" {
  region                  = "us-east-1"
  shared_credentials_file = "${pathexpand("~/.aws/credentials")}"
  profile                 = "default"

  assume_role {
    role_arn = "arn:aws:iam::1234567890:role/OrganizationAccountAccessRole"
  }
}

"profile" is a named profile in ~/.aws/credentials that has AWS Access keys. E.g.

[default]
region = us-east-1
aws_access_key_id = AKIAJXXXXXXXXXXXX
aws_secret_access_key = Aadxxxxxxxxxxxxxxxxxxxxxxxxxxxx    

This is not an IAM user in the account you want to access. It's in the "source" account (you need keys at some point to access the AWS cli).

"assume_role.role_arn" is the role in the account you want to assume. The IAM user in "profile" needs to be allowed to assume that role.

Solution 3

Looking at your policy of trust relationship in the other account, there's a condition applied multi factor authentication below highlighted. So User should 2 factor authenticated before assuming the role. Remove this condition and try to run code.

   "Condition": {
        "Bool": {
          "aws:MultiFactorAuthPresent": "true"
        }
      }