IAM-Deescalate

IAM-Deescalate helps mitigate privilege escalation risk in AWS identity and access management (IAM)
aws
iam
prisma-cloud
privilege-escalation
security
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IAM-Deescalate

IAM-Deescalate helps mitigate privilege escalation risk in AWS identity and access management (IAM). It identifies the IAM users and roles with privilege escalation risk using NCC Group's PMapper and creates a set of policies to "deescalate" the risk. IAM-Deescalate was developed when we were working on the Cloud Threat Report Vol. 6. More information about the tool can be found in this blog.

IAM-Deescalate has only four commands, audit, plan, apply, and revert.

  • audit command uses PMapper to model an AWS account as a graph, and searches for principals risky for privilege escalation.

  • plan command analyzes the privilege escalation risk and creates a remediation plan for each risky principal. Users should review the plans and decide which policies to apply.

  • apply command inserts inline policies to risky principals based on the plans. Note that applying these policies may impact operations if the remediated identities require the revoked permissions.

  • revert command removes all the inserted policies previously applied.

Flow

How does it work?

PMapper models the identities in an AWS account as a directed graph, in which each node represents a principal (user or role) and each edge represents a transition from one principal to another. node A -> node B indicates that principal A can authenticate as principal B. For example, if user A can assume role B, then there is an edge directed from node A to node B. Similarly, if user C can pass role B to an EC2 instance that user C controls, then there is an edge directed from user C to role B. With this graph, one can find the possible paths between any two nodes.

A node (principal) is risky for privilege escalation if this node is NOT an admin principal but has a path to an admin principal.

IAM-Deescalate calculates all the possible edges from non-admin principals to admin principals. These are the edges that allow privilege escalation. IAM-Deescalate attempts to break these edge to eliminate the privilege escalation risk. To break an edge from node A to node B, IAM-Deescalate revokes a few permissions on principal A so that principal A can no longer authenticate as principal B. IAM-Deescalate revokes these permissions by inserting an inline policy with explicit deny.

To understand why one principal can authenticate as another principal, IAM-Deescalate analyzes the reason property in each PMapper's Edge instance. The reason property stores human-readable text explaining the relationship between the two connected principals. Note that if PMapper updates these descriptions, IAM-Deescalate will likely fail to interpret the relationship correctly.

Let's get started

To get started, you need a Python3 environment and a credential with sufficient permissions to access the targeted AWS account. The credential needs to be stored in a [credential file(https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-files.html)] on the host. By default, AWS's client tools and libraries look for the credential file at ~/.aws/credentials. However, this default path can be changed by setting the environment variable AWS_SHARED_CREDENTIALS_FILE

Required permissions

required_permissions.json lists the minimal set of AWS permission required for both IAM-Deescalate and PMapper (v1.1.5).

Installation

requirements.txt lists the three dependencies for both IAM-Deescalate and PMapper (v1.1.5).

Host installation:

mkdir iam && cd iam
git clone https://github.com/nccgroup/PMapper.git
git clone https://github.com/PaloAltoNetworks/IAM-Deescalate.git
cp IAM-Deescalate/misc/gathering.py PMapper/principalmapper/graphing/gathering.py
cp IAM-Deescalate/misc/case_insensitive_dict.py PMapper/principalmapper/util/case_insensitive_dict.py
cd IAM-Deescalate
pip3 install -r requirements.txt

Build a Docker image

git clone https://github.com/PaloAltoNetworks/IAM-Deescalate.git
cd IAM-Deescalate
docker build -t iam-deesc .

Usage

usage: iam_deesc.py [-h] [--profile PROFILE] {audit,plan,apply,revert} ...

optional arguments:
  -h, --help            show this help message and exit
  --profile PROFILE     AWS profile to use. If not provided, the default profile will be used

subcommand:
  The subcommand to use among this suite of tools

  {audit,plan,apply,revert}
                        Select a subcommand to execute
    audit               Pull the IAM information from an AWS account and serach for principals with privilege escalation risks. E.g., python3 iam_deesc.py --profile my_prof audit
    plan                Use the audit result to create a remediation plan. If --auto flag is specified, the "patch_me" fields in each plan will be set to 1
    apply               Apply the remediation plan.This command needs to be run after the plan commmand finishes. E.g., python3 iam_deesc.py --profile my_profile apply
    revert              Revert the changes made by the apply command. If --all flag is specified, IAM-Deescalate will check EVERY user and role in this account

audit

The audit command models the principals as a graph using PMapper and identifies the principals with privilege escalation risks.

python3 iam_deesc.py --profile my_prof audit

plan

The plan command creates remediation plans based on the audit result. The plans are stored under ./output/plan/. By default, all the "patch_me" fields are marked as 0, meaning that no actions will be taken when running the apply command. Users need to go through each plan and manually mark patch_me to 1. Read the Sample Remediation Plan section for more detail.

python3 iam_deesc.py --profile my_prof plan

If --auto flag is specified, the plan command will automatically select a remediation strategy for each principal.

python3 iam_deesc.py --profile my_prof plan --auto

apply

The apply command takes the policies with "patch_me" marked as 1 and attaches them to the risky principals

python3 iam_deesc.py --profile my_prof apply

revert

The revert command removes all the attached remediation policies.

python3 iam_deesc.py --profile my_prof revert

Using Docker

First build an image following the Build a Docker image instruction. Use Docker to execute every command.

docker run --rm -it -v [path to aws credential file]:/.aws/credentials -v [path to output directory]:/app/IAM-Deescalate/output iam-deesc [command]

Examples:

docker run --rm -it -v /home/ec2-user/.aws/credentials:/.aws/credentials -v /home/ec2-user/iam/IAM-Deescalate/output:/app/IAM-Deescalate/output iam-deesc --profile my_prof audit 

docker run --rm -it -v /home/ec2-user/.aws/credentials:/.aws/credentials -v /home/ec2-user/iam/IAM-Deescalate/output:/app/IAM-Deescalate/output iam-deesc --profile my_prof plan --auto

Test

BishopFox's Seth Art created a cool project called IAM Vulnerable that can quickly build 31 different AWS IAM privilege escalation scenarios. It uses Terraform to easily provision and deprovision each scenario. IAM-Deescalate used IAM Vulnerable extensively during development.

Sample Remediation Plan

Here is a sample remediation plan. In this plan, user bob is risky for privilege escalation. Two possible privilege escalation paths are identified. The first path allows bob to escalate to user it_admin, and the second path allows bob to escalate to role it_admin_role.

To remediate the first attack path, we need to prevent bob from creating an access key for it_admin. If you agree to apply this policy, set the "patch_me" field to 1.

There are two options to remediate the second attack path. Each option is represented as a policy, and applying one of these two policies can remediate the risk. The first policy prevents bob from passing the it_admin_role to EC2 instances. The second policy prevents bob from associating an instance profile to EC2 instances. If you agree with any of the policies, set its "patch_me" field to 1.

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