如何获取 aws-iam-token 以使用 IRSA 访问 S3？

Question

我在 Terraform 中创建了一个 IRSA 角色，以便 K8s 作业可以使用关联的服务帐户来访问 S3 存储桶，但我在作业中不断收到 AccessDenied 错误。

我首先在我们的 eks 模块中使用 enable_irsa = true 在我们的 EKS 集群中启用了 IRSA。

然后我创建了一个简单的 aws_iam_policy 作为：

resource "aws_iam_policy" "eks_s3_access_policy" {
  name = "eks_s3_access_policy"

  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Action = [
          "s3:*",
        ]
        Effect   = "Allow"
        Resource = "arn:aws:s3:::*"
      },
    ]
  })
}

和一个iam-assumable-role-with-oidc:

module "iam_assumable_role_with_oidc_for_s3_access" {
  source  = "terraform-aws-modules/iam/aws//modules/iam-assumable-role-with-oidc"
  version = "~> 3.0"

  create_role = true
  role_name = "eks-s3-access"
  role_description = "Role to access s3 bucket"
  tags = { Role = "eks_s3_access_policy" }
  provider_url = replace(module.eks.cluster_oidc_issuer_url, "https://", "")
  role_policy_arns = [aws_iam_policy.eks_s3_access_policy.arn]
  number_of_role_policy_arns = 1
  oidc_fully_qualified_subjects = ["system:serviceaccount:default:my-user"]
}

我使用 Helm 创建了一个 K8s 服务帐户，例如：

Name:                my-user
Namespace:           default
Labels:              app.kubernetes.io/managed-by=Helm
Annotations:         eks.amazonaws.com/role-arn: arn:aws:iam::111111:role/eks-s3-access
                     meta.helm.sh/release-name: XXXX
                     meta.helm.sh/release-namespace: default
Image pull secrets:  <none>
Mountable secrets:   my-user-token-kwwpq
Tokens:              my-user-token-kwwpq
Events:              <none>

最后，使用 K8s API 从作业模板创建作业：

apiVersion: batch/v1
kind: Job
metadata:
  name: job
  namespace: default
spec:
  template:
  spec:
    serviceAccountName: my-user
    containers:
    - name: {{ .Chart.Name }}
      env:
      - name: AWS_ROLE_ARN
        value: arn:aws:iam::746181457053:role/eks-s3-access
      - name: AWS_WEB_IDENTITY_TOKEN_FILE
        value: /var/run/secrets/eks.amazonaws.com/serviceaccount/token
      volumeMounts:
      - mountPath: /var/run/secrets/eks.amazonaws.com/serviceaccount
        name: aws-iam-token
        readOnly: true
    volumes:
    - name: aws-iam-token
      projected:
        defaultMode: 420
        sources:
        - serviceAccountToken:
          audience: sts.amazonaws.com
          expirationSeconds: 86400
          path: token

当作业尝试获取指定的凭据时，指定的令牌不存在：

2021-08-03 18:02:41  Refreshing temporary credentials failed during mandatory refresh period.
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/aiobotocore/credentials.py", line 291, in _protected_refresh
    metadata = await self._refresh_using()
  File "/usr/local/lib/python3.7/site-packages/aiobotocore/credentials.py", line 345, in fetch_credentials
    return await self._get_cached_credentials()
  File "/usr/local/lib/python3.7/site-packages/aiobotocore/credentials.py", line 355, in _get_cached_credentials
    response = await self._get_credentials()
  File "/usr/local/lib/python3.7/site-packages/aiobotocore/credentials.py", line 410, in _get_credentials
    kwargs = self._assume_role_kwargs()
  File "/usr/local/lib/python3.7/site-packages/aiobotocore/credentials.py", line 420, in _assume_role_kwargs
    identity_token = self._web_identity_token_loader()
  File "/usr/local/lib/python3.7/site-packages/botocore/utils.py", line 2365, in __call__
    with self._open(self._web_identity_token_path) as token_file:
FileNotFoundError: [Errno 2] No such file or directory: '/var/run/secrets/eks.amazonaws.com/serviceaccount/token'

根据 https://aws.amazon.com/blogs/opensource/introducing-fine-grained-iam-roles-service-accounts/ 中的描述，webhook 通常会在创建 pod 时创建这些凭据。然而，由于我们在 k8s 集群中按需创建新的 k8s 作业，我怀疑 webhook 没有创建任何此类凭据。

如何请求在 K8s 集群中创建正确的凭据？有没有办法从集群中实例化 webhook？

Answer 1

有几件事可能会导致失败。

检查 IRSA 角色的所有设置。对于信任关系设置，请检查命名空间的名称和服务帐户的名称是否正确。只有这些设置匹配角色才能承担。
当 pod 处于运行时尝试使用 shell 访问 pod。检查“AWS_*”环境变量的内容。检查 AWS_ROLE_ARN 指向正确的角色。检查 AWS_WEB_IDENTITY_TOKEN_FILE 指向的文件是否在其位置并且可读。只需尝试对文件执行 cat 以查看它是否可读。
如果您运行您的 Pod 是非根用户（出于安全原因推荐这样做），请确保运行 Pod 的用户可以访问该文件。如果不是，请调整 pod 的 securityContext。也许 fsGroup 的设置在这里可以提供帮助。 https://kubernetes.io/docs/reference/kubernetes-api/workload-resources/pod-v1/#security-context
确保您的 pos 使用的 SDK 支持 IRSA。如果您使用的是较旧的 SDK，则可能不支持 IRSA。查看 IRSA 文档以了解受支持的 SDK 版本。 https://docs.aws.amazon.com/eks/latest/userguide/iam-roles-for-service-accounts-minimum-sdk.html

如何获取 aws-iam-token 以使用 IRSA 访问 S3？

How do you obtain an aws-iam-token to access S3 using IRSA?

amazon-s3

openid-connect

kubernetes

terraform

k8s-serviceaccount