Terraform无法承担启用了MFA的角色

时间：2018-09-20 20:20:38

标签： amazon-web-services terraform amazon-iam terraform-provider-aws

我要让Terraform在另一个需要MFA的帐户中担任IAM角色真是太糟糕了。这是我的设置

AWS配置

[default]
region = us-west-2
output = json

[profile GEHC-000]
region = us-west-2
output = json

....

[profile GEHC-056]
source_profile = GEHC-000
role_arn = arn:aws:iam::~069:role/hc/hc-master
mfa_serial = arn:aws:iam::~183:mfa/username
external_id = ~069

AWS凭证

[default]
aws_access_key_id = xxx
aws_secret_access_key = xxx


[GEHC-000]
aws_access_key_id = same as above
aws_secret_access_key = same as above

分配给IAM用户的策略

STS政策

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "AssumeRole",
            "Effect": "Allow",
            "Action": [
                "sts:AssumeRole"
            ],
            "Resource": [
                "arn:aws:iam::*:role/hc/hc-master"
            ]
        }
    ]
}

用户政策

{
    "Statement": [
        {
            "Action": [
                "iam:*AccessKey*",
                "iam:*MFA*",
                "iam:*SigningCertificate*",
                "iam:UpdateLoginProfile*",
                "iam:RemoveUserFromGroup*"
            ],
            "Effect": "Allow",
            "Resource": [
                "arn:aws:iam::~183:mfa/${aws:username}",
                "arn:aws:iam::~183:mfa/*/${aws:username}",
                "arn:aws:iam::~183:mfa/*/*/${aws:username}",
                "arn:aws:iam::~183:mfa/*/*/*${aws:username}",
                "arn:aws:iam::~183:user/${aws:username}",
                "arn:aws:iam::~183:user/*/${aws:username}",
                "arn:aws:iam::~183:user/*/*/${aws:username}",
                "arn:aws:iam::~183:user/*/*/*${aws:username}"
            ],
            "Sid": "Write"
        },
        {
            "Action": [
                "iam:*Get*",
                "iam:*List*"
            ],
            "Effect": "Allow",
            "Resource": [
                "*"
            ],
            "Sid": "Read"
        },
        {
            "Action": [
                "iam:CreateUser*",
                "iam:UpdateUser*",
                "iam:AddUserToGroup"
            ],
            "Effect": "Allow",
            "Resource": [
                "*"
            ],
            "Sid": "CreateUser"
        }
    ],
    "Version": "2012-10-17"
}

强制MFA政策

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "BlockAnyAccessOtherThanAboveUnlessSignedInWithMFA",
            "Effect": "Deny",
            "NotAction": "iam:*",
            "Resource": "*",
            "Condition": {
                "BoolIfExists": {
                    "aws:MultiFactorAuthPresent": "false"
                }
            }
        }
    ]
}

main.tf 

provider "aws" {
  profile                 = "GEHC-056"
  shared_credentials_file = "${pathexpand("~/.aws/config")}"
  region                  = "${var.region}"
}

data "aws_iam_policy_document" "test" {
  statement {
    sid    = "TestAssumeRole"
    effect = "Allow"

    actions = [
      "sts:AssumeRole",
    ]

    principals = {
      type = "AWS"

      identifiers = [
        "arn:aws:iam::~183:role/hc-devops",
      ]
    }

    sid    = "BuUserTrustDocument"
    effect = "Allow"

    principals = {
      type = "Federated"

      identifiers = [
        "arn:aws:iam::~875:saml-provider/ge-saml-for-aws",
      ]
    }

    condition {
      test     = "StringEquals"
      variable = "SAML:aud"
      values   = ["https://signin.aws.amazon.com/saml"]
    }
  }
}

resource "aws_iam_role" "test_role" {
  name               = "test_role"
  path               = "/"
  assume_role_policy = "${data.aws_iam_policy_document.test.json}"
}

获取来电者身份

bash-4.4$ aws --profile GEHC-056 sts get-caller-identity
Enter MFA code for arn:aws:iam::772660252183:mfa/503072343:
{
  "UserId": "AROAIWCCLC2BGRPQMJC7U:botocore-session-1537474244",
  "Account": "730993910069",
  "Arn": "arn:aws:sts::730993910069:assumed-role/hc-master/botocore-session-1537474244"
}

错误：

bash-4.4$ terraform plan
Refreshing Terraform state in-memory prior to plan...
The refreshed state will be used to calculate this plan, but will not be
persisted to local or remote state storage.


Error: Error refreshing state: 1 error(s) occurred:

* provider.aws: Error creating AWS session: AssumeRoleTokenProviderNotSetError: assume role with MFA enabled, but AssumeRoleTokenProvider session option not set.

3 个答案:

答案 0 :(得分：4)

Terraform当前不支持在运行时提示MFA令牌，因为它打算以尽可能少的交互方式运行，并且显然需要对提供者结构进行大量修改才能支持此交互式提供者配置。 this issue中对此有更多讨论。

在该期杂志中也提到，最好的选择是使用某种形式的脚本/工具，在运行Terraform之前已经承担了该角色。

我个人使用AWS-Vault，并编写了一个小垫片程序脚本，我从terraform符号链接到该脚本（以及其他一些我想使用AWS-Vault抓取的东西，例如aws）凭证）来检测被调用的内容，然后使用which -a找到“真实”二进制文件，然后使用AWS-Vault的exec以指定的凭证运行目标命令。

我的脚本如下：

#!/bin/bash

set -eo pipefail

# Provides a shim to override target executables so that it is executed through aws-vault
# See https://github.com/99designs/aws-vault/blob/ae56f73f630601fc36f0d68c9df19ac53e987369/USAGE.md#overriding-the-aws-cli-to-use-aws-vault for more information about using it for the AWS CLI.

# Work out what we're shimming and then find the non shim version so we can execute that.
# which -a returns a sorted list of the order of binaries that are on the PATH so we want the second one.
INVOKED=$(basename $0)
TARGET=$(which -a ${INVOKED} | tail -n +2 | head -n 1)

if [ -z ${AWS_VAULT} ]; then
    AWS_PROFILE="${AWS_DEFAULT_PROFILE:-read-only}"
    (>&2 echo "Using temporary credentials from ${AWS_PROFILE} profile...")

    exec aws-vault exec "${AWS_PROFILE}" --assume-role-ttl=60m -- "${TARGET}" "$@"
else
    # If AWS_VAULT is already set then we want to just use the existing session instead of nesting them
    exec "${TARGET}" "$@"
fi

它将使用您~/.aws/config文件中的配置文件，该配置文件与您设置的AWS_DEFAULT_PROFILE环境变量匹配，默认为read-only配置文件，这对您而言可能是有用的默认值。这样可以确保AWS-Vault承担IAM角色，获取凭据并将其设置为目标进程的环境变量。

这意味着就Terraform而言，它是通过环境变量获得凭据的，并且可以正常工作。

答案 1 :(得分：1)

我使用了一个非常简单的解决方案来解决此问题：

首先，让TF从环境变量中选择凭证。然后：

AWS凭证文件：

[access]
aws_access_key_id = ...
aws_secret_access_key = ...
region = ap-southeast-2
output = json

[target]
role_arn = arn:aws:iam::<target nnn>:role/admin
source_profile = access
mfa_serial = arn:aws:iam::<access nnn>:mfa/my-user

在控制台中

CREDENTIAL=$(aws --profile target sts assume-role \
  --role-arn arn:aws:iam::<target nnn>:role/admin --role-session-name TFsession \
  --output text \
  --query "Credentials.[AccessKeyId,SecretAccessKey,SessionToken,Expiration]")

<enter MFA>

#echo "CREDENTIAL: ${CREDENTIAL}"
export AWS_ACCESS_KEY_ID=$(echo ${CREDENTIAL} | cut -d ' ' -f 1)
export AWS_SECRET_ACCESS_KEY=$(echo ${CREDENTIAL} | cut -d ' ' -f 2)
export AWS_SESSION_TOKEN=$(echo ${CREDENTIAL} | cut -d ' ' -f 3)

terraform plan

更新：更好的解决方案是使用https://github.com/remind101/assume-role获得相同的结果。

答案 2 :(得分：1)

另一种方法是使用 credential_process 以通过本地脚本生成凭据并将令牌缓存在新配置文件中（我们称之为 tf_temp）

这个脚本将：

  • 检查令牌对于配置文件 tf_temp

    是否仍然有效

  • 如果令牌有效，则使用 aws configure get xxx --profile tf_temp

    从现有配置中提取令牌

  • 如果令牌无效，提示使用输入 mfa 令牌

  • 使用 aws assume-role --token-code xxxx ... --profile your_profile

    生成会话令牌

  • 使用 tf_temp

    设置临时配置文件令牌 aws configure set xxx --profile tf_temp

你会：

~/.aws/credentials

[prod]
aws_secret_access_key = redacted
aws_access_key_id = redacted

[tf_temp]

[tf]
credential_process = sh -c 'mfa.sh arn:aws:iam::{account_id}:role/{role} arn:aws:iam::{account_id}:mfa/{mfa_entry} prod 2> $(tty)'

mfa.sh

gist

在 /bin/mfa.sh 或 /usr/local/bin/mfa.sh 中移动此脚本：

#!/bin/sh
set -e

role=$1
mfa_arn=$2
profile=$3
temp_profile=tf_temp

if [ -z $role ]; then echo "no role specified"; exit 1; fi
if [ -z $mfa_arn ]; then echo "no mfa arn specified"; exit 1; fi
if [ -z $profile ]; then echo "no profile specified"; exit 1; fi

resp=$(aws sts get-caller-identity --profile $temp_profile | jq '.UserId')

if [ ! -z $resp ]; then
    echo '{
        "Version": 1,
        "AccessKeyId": "'"$(aws configure get aws_access_key_id --profile $temp_profile)"'",
        "SecretAccessKey": "'"$(aws configure get aws_secret_access_key --profile $temp_profile)"'",
        "SessionToken": "'"$(aws configure get aws_session_token --profile $temp_profile)"'",
        "Expiration": "'"$(aws configure get expiration --profile $temp_profile)"'"
    }'
    exit 0
fi
read -p "Enter MFA token: " mfa_token

if [ -z $mfa_token ]; then echo "MFA token can't be empty"; exit 1; fi

data=$(aws sts assume-role --role-arn $role \
                    --profile $profile \
                    --role-session-name "$(tr -dc A-Za-z0-9 </dev/urandom | head -c 20)" \
                    --serial-number $mfa_arn \
                    --token-code $mfa_token | jq '.Credentials')

aws_access_key_id=$(echo $data | jq -r '.AccessKeyId')
aws_secret_access_key=$(echo $data | jq -r '.SecretAccessKey')
aws_session_token=$(echo $data | jq -r '.SessionToken')
expiration=$(echo $data | jq -r '.Expiration')

aws configure set aws_access_key_id $aws_access_key_id --profile $temp_profile
aws configure set aws_secret_access_key $aws_secret_access_key --profile $temp_profile
aws configure set aws_session_token $aws_session_token --profile $temp_profile
aws configure set expiration $expiration --profile $temp_profile

echo '{
  "Version": 1,
  "AccessKeyId": "'"$aws_access_key_id"'",
  "SecretAccessKey": "'"$aws_secret_access_key"'",
  "SessionToken": "'"$aws_session_token"'",
  "Expiration": "'"$expiration"'"
}'

在提供商设置中使用 tf 配置文件。第一次会提示mfa token :

# terraform apply
Enter MFA token: 428313

此解决方案适用于 terraform 和/或 terragrunt

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