Role with privilege escalation by actions 'iam:PutGroupPolicy'

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Metadata

Id: d6047119-a0b2-4b59-a4f2-127a36fb685b

Cloud Provider: AWS

Platform: Terraform

Severity: Medium

Category: Access Control

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Description

Granting the iam:PutGroupPolicy action with the Resource value set to "*" in an IAM policy, as shown below, allows the role to attach arbitrary permissions to any IAM group in the account:

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

This powerful permission can be abused for privilege escalation, as a malicious user assuming this role could grant themselves or others elevated privileges by attaching highly permissive group policies. To mitigate this risk, limit the scope of the Resource attribute to only the intended groups and restrict allowed actions to only those necessary for the role’s function.

Compliant Code Examples

resource "aws_iam_user" "cosmic2" {
  name = "cosmic2"
}

resource "aws_iam_user_policy" "inline_policy_run_instances2" {
  name = "inline_policy_run_instances"
  user = aws_iam_user.cosmic2.name

  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Action = [
          "ec2:Describe*",
        ]
        Effect   = "Allow"
        Resource = "*"
      },
    ]
  })
}

Non-Compliant Code Examples

resource "aws_iam_role" "cosmic" {
  name = "cosmic"
}

resource "aws_iam_role_policy" "test_inline_policy" {
  name = "test_inline_policy"
  role = aws_iam_role.cosmic.name

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