Identity and Access Management (IAM) plays a crucial role in securing an organization’s infrastructure, particularly in a cloud environment like AWS. With the growing adoption of cloud services, companies need a robust and flexible system to manage who can access what resources and under which conditions. AWS IAM is designed to do exactly that by controlling and monitoring access to AWS services and resources.
When managing IAM within AWS, administrators can define a range of permissions through policies, roles, and groups, allowing them to grant or restrict access to specific AWS services, such as S3, EC2, or CloudWatch. The ability to assign these permissions is key to ensuring that the right individuals have access to the appropriate resources while keeping malicious actors at bay. However, a critical challenge arises when assigning administrative access, especially to users responsible for managing IAM itself, as seen in the scenario with Andrew and John.
Andrew, the Cloud Architect at XYZ company, holds full administrative privileges in the company’s AWS tenant. He has the responsibility to manage the account’s structure and security. When a new IAM administrator, John, joins the security team, Andrew is tasked with providing him the necessary permissions to manage IAM users, groups, roles, and policies. John’s role requires full administrative capabilities within IAM, so Andrew assigns the IAMFullAccess policy to John’s account, allowing him to perform these administrative tasks.
At first glance, this may seem like a simple and sufficient solution. By giving John IAMFullAccess, Andrew has enabled him to manage users, groups, and roles, which is precisely what John needs to do his job. However, this approach introduces a significant security risk: privilege escalation.
Privilege escalation occurs when a user is able to gain access to more privileges than originally intended by the administrator. In this case, John, as an IAM administrator, can modify his own permissions or create new accounts for himself or others with AdministratorAccess permissions, which would grant them full administrative rights to the entire AWS environment. In essence, John could escalate his privileges by giving himself more access than what Andrew initially intended. This could lead to unauthorized access, data breaches, or misconfigurations that could compromise the entire system.
While IAMFullAccess is designed to provide full administrative rights over IAM resources, it is not inherently restrictive enough to prevent privilege escalation. IAMFullAccess allows users to modify their own permissions, potentially leading to serious security risks if the user is not carefully controlled. This situation is not unique to XYZ company; it is a common problem faced by cloud administrators in many organizations, particularly those with large or complex environments.
In this part of the discussion, we will examine the risks that arise from granting full administrative privileges to users and why additional controls, such as permission boundaries, are essential to ensuring the integrity of the IAM system. We will also discuss the essential principles of least privilege and how they apply to managing IAM access.
The Importance of the Principle of Least Privilege
One of the foundational concepts in IAM is the principle of least privilege. This principle dictates that users and applications should only be granted the minimum level of access required to perform their jobs or tasks. This approach reduces the potential for accidental or malicious misuse of privileges and helps to limit the scope of damage if a user’s credentials are compromised.
In the context of John’s IAM access, IAMFullAccess grants more permissions than he actually needs. While John does need the ability to manage IAM users, groups, and roles, he doesn’t need the ability to modify his own permissions or escalate his privileges. By assigning him IAMFullAccess, Andrew has inadvertently violated the principle of least privilege. John could potentially modify his own permissions, assign himself higher-level privileges, or create other accounts with more access than necessary, leading to an increased attack surface.
In contrast, applying the principle of least privilege would mean that John would only be granted the permissions he absolutely needs to manage IAM, without the ability to alter his own permissions or assign administrative-level permissions to others. This would significantly reduce the risk of privilege escalation, as John would be constrained to a well-defined set of actions within IAM.
However, the principle of least privilege is difficult to achieve with just the default IAM policies. While AWS offers a range of predefined policies, including IAMFullAccess, they often grant more permissions than necessary. To mitigate the risks of privilege escalation and meet the principle of least privilege, administrators can use permission boundaries to create fine-grained access control.
The Need for Permission Boundaries in IAM
A permission boundary is a policy that sets the maximum permissions a user or role can have in IAM. While IAM policies define the actions a user can take, permission boundaries act as a “fence” around those permissions, ensuring that users cannot exceed the scope of what is explicitly allowed by the boundary. Even if a user has permissions granted by their IAM policy, the permission boundary enforces a strict limitation on what they can actually do.
In the scenario with John, the permission boundary would restrict his ability to escalate his privileges or modify his account in any way that could lead to privilege escalation. The permission boundary would ensure that John could perform his job as an IAM administrator but could not alter his own account or grant himself or others higher-level permissions, such as AdministratorAccess.
By applying a permission boundary, Andrew can ensure that John’s account remains within a set of predefined, secure limits, thus preventing privilege escalation. This makes permission boundaries an essential tool for maintaining security in any IAM setup, especially when delegating administrative access to IAM resources.
What Are Permission Boundaries and How Do They Work?
To better understand how to secure IAM access and prevent privilege escalation, we must first explore the concept of permission boundaries in AWS IAM. Permission boundaries are a critical component of AWS IAM that allow administrators to restrict the scope of what an IAM user or role can do, even if the user has a wide range of permissions granted by their identity-based policies.
When a user is assigned a policy, that policy specifies the actions the user can take and the resources they can access. However, identity-based policies on their own are not enough to limit the maximum level of access a user can have. This is where permission boundaries come into play, acting as a second layer of security that sets a “fence” around the permissions that a user or role can possess, regardless of what is specified in their identity-based policy.
Defining Permission Boundaries
A permission boundary is essentially a policy document—written in JSON format—that defines the maximum permissions a user or role can have, regardless of what their identity-based policy allows. In simple terms, it is a set of rules that tells AWS IAM what actions are off-limits for the user or role, no matter how broad or generous their identity policy might be.
A permission boundary policy works alongside an identity policy (such as IAMFullAccess) to limit the maximum scope of actions a user can take. If the identity policy grants a user access to a wide range of actions, the permission boundary can limit them to only specific actions. Essentially, the user can only perform actions that are both allowed by their identity-based policy and within the boundaries set by their permission boundary. If the identity policy allows access to an action but the permission boundary denies it, the user will be restricted from performing that action.
Key Characteristics of Permission Boundaries:
- Limit Permissions: A permission boundary does not grant permissions but limits the maximum permissions a user or role can have.
- Policy as Fence: It acts as a boundary, creating a “fence” around the IAM user’s abilities to ensure that they cannot exceed the actions defined in the boundary policy.
- Implicit Deny: By default, all actions are implicitly denied unless explicitly allowed in either the identity policy or the permission boundary.
- JSON Format: Just like other AWS IAM policies, permission boundaries are defined using JSON syntax.
When applied to an IAM user or role, permission boundaries work in conjunction with the policies that the user or role has. If an identity policy allows a specific action but the permission boundary denies it, the user or role cannot perform that action.
How Permission Boundaries Prevent Privilege Escalation
Privilege escalation occurs when a user gains higher levels of access than originally intended. This is a significant risk when users are granted broad permissions, such as full administrative access, as was the case with John. Without any form of restriction, John could potentially modify his own account or create new accounts for himself or others with AdministratorAccess permissions, which would grant them full administrative rights to the entire AWS environment. In essence, John could escalate his privileges by giving himself more access than what Andrew initially intended. This could lead to unauthorized access, data breaches, or misconfigurations that could compromise the entire system.
Permission boundaries help mitigate this risk by enforcing restrictions on actions that users can take, even if their identity policies grant them full access. Specifically, permission boundaries allow administrators to:
- Restrict Self-Modifications: A permission boundary can be set up to prevent a user from modifying or deleting their own IAM user account. This ensures that users cannot escalate their own privileges or remove the restrictions placed on them.
- Limit New User Permissions: Permission boundaries can also prevent users from creating new IAM users with higher permissions than they have. For example, a user may be restricted from creating new users with AdministratorAccess even if their identity policy grants them the ability to create users.
- Control Access to Critical Resources: In cases where users need to manage sensitive AWS services or resources, permission boundaries can ensure that they can only access a predefined set of services, reducing the risk of unintended exposure or misuse.
In John’s case, while the IAMFullAccess policy grants him the ability to manage IAM users, groups, and policies, it also allows him to modify his own account or create new users with broader access, which introduces significant risks. By using a permission boundary, Andrew can ensure that John’s account is restricted to the administrative tasks needed for his role while preventing him from modifying his own account or granting others higher levels of access.
Syntax and Structure of Permission Boundaries
Permission boundaries are created in JSON format, similar to IAM policies, and consist of one or more statements that define the allowed actions for a user or role. Each statement includes the following components:
- Effect: Specifies whether the action is allowed or denied. Common values are Allow or Deny.
- Action: Lists the specific AWS actions the user is allowed or denied to perform (e.g., iam:CreateUser, iam:UpdateUser).
- Resource: Defines which resources the user can access or modify. For example, you can specify the ARN of an IAM user or resource that the policy applies to.
Here’s a simplified example of what a permission boundary policy might look like:
This example shows a permission boundary policy that allows the user to perform various actions related to IAM users, groups, and roles. However, it does not grant permissions to modify or delete policies. This type of policy could be useful in limiting what an IAM administrator can do with their permissions, preventing them from creating or attaching policies that could escalate their access.
It’s important to note that permission boundaries are not a way to grant permissions. Instead, they limit the actions that can be performed by users, even if their identity policy allows broader access. Both the identity policy and the permission boundary must be considered together to determine what actions a user is allowed to perform.
Permission Boundaries in Action: Use Case for John
Now that we have a clear understanding of what permission boundaries are and how they work, let’s return to John’s scenario at XYZ company. Andrew, the Cloud Architect, needs to ensure that John, as an IAM administrator, can perform the necessary tasks to manage IAM resources but cannot escalate his privileges or create users with higher permissions.
John has been assigned the IAMFullAccess policy, which grants him extensive administrative access within IAM. However, this policy alone could allow John to modify his own permissions or assign himself more privileges, which introduces significant risks. To mitigate these risks, Andrew will use permission boundaries to create a set of restrictions that limit John’s access to only the specific IAM actions he needs.
The permission boundary will do the following:
- Allow John to perform IAM administrative tasks like creating and managing users, groups, and roles.
- Prevent John from modifying his own account or granting himself higher permissions.
- Ensure that John cannot create new users with permissions higher than his own (e.g., AdministratorAccess).
- Restrict the resources that John can manage to only the services necessary for his job.
The permission boundary ensures that John cannot exceed the permissions defined in the boundary policy, even though his identity policy (IAMFullAccess) may grant more permissions. This combination of an identity policy and a permission boundary allows Andrew to ensure that John can do his job securely without the risk of privilege escalation.
Implementing the Administrative Boundary Policy for John
Now that we understand the concept of permission boundaries and their role in limiting access, let’s focus on how Andrew can implement a boundary policy to secure John’s IAM access. The goal is to ensure that John can effectively manage IAM resources, such as users, groups, and roles, without the risk of privilege escalation. Specifically, Andrew needs to prevent John from modifying his own account or granting higher permissions to other users, while still allowing him to perform his job responsibilities.
In this section, we’ll break down how to create a permission boundary policy that accomplishes this. This policy will establish a framework around what John can and cannot do in IAM, effectively limiting his scope of action.
Setting Up the Permission Boundary
To ensure John can manage IAM resources without opening the door for privilege escalation, Andrew needs to set clear boundaries on the actions John is allowed to take. This will involve creating a boundary policy that restricts John’s ability to modify his own IAM user account and prevents him from granting himself or others administrative-level access.
- Allow John to manage IAM resources: The first part of the boundary policy will grant John permission to perform essential IAM administrative tasks, such as creating users, managing groups, and assigning policies to roles. These are the core functions John needs to perform his job.
- Prevent John from modifying his own account: The second part of the boundary policy must prevent John from making changes to his own IAM user account, which would allow him to escalate his privileges. Specifically, John should not be able to change his permissions or delete his user account.
- Prohibit John from creating privileged users: The final piece of the boundary policy will ensure that John cannot create new IAM users with more privileges than he himself has. For example, John should not be able to create users with AdministratorAccess permissions or assign overly permissive policies to any new users he creates.
Creating the Administrative Boundary Policy
To implement these restrictions, Andrew needs to create an administrative boundary policy that will be applied to John’s IAM account. This policy will outline the specific permissions John is allowed to perform, while explicitly denying actions that could lead to privilege escalation.
The policy will contain several statements:
- Allowing essential IAM actions: The first statement will permit John to perform necessary administrative tasks, such as creating and managing IAM users, groups, and roles. However, this statement will not include permissions to modify or delete his own account.
- Denying self-modification: The next statement will specifically deny John the ability to modify his own IAM user account. This is a key part of preventing privilege escalation. John should not be able to update his own user details or delete his account.
- Restricting the creation of privileged users: The final statement will ensure that John cannot create new users with permissions greater than his own. This can be done by denying John the ability to assign high-level permissions, such as AdministratorAccess, to any new users.
With these objectives in mind, Andrew can create a permission boundary that ensures John can perform his administrative duties without the ability to escalate his own privileges or give others excessive access. The boundary policy will work alongside John’s identity policy (such as IAMFullAccess) to enforce these restrictions.
Applying the Boundary Policy to John
Once the administrative boundary policy is defined, the next step is to apply it to John’s IAM user account. This is done by assigning the boundary policy to John’s user profile within AWS IAM. The permission boundary policy will then serve as a “fence” around the permissions granted to John by his identity policy, limiting his actions to only those defined by the boundary.
In practical terms, this means that even though John’s identity policy (e.g., IAMFullAccess) might grant him broad permissions, the permission boundary will restrict him to a more specific set of actions that Andrew has deemed appropriate for his role. This significantly reduces the risk of privilege escalation and ensures that John’s access is properly controlled.
Verifying the Permissions
After applying the boundary policy to John’s account, Andrew should verify that the restrictions are working as expected. This can be done by reviewing the actions John is allowed to perform and testing whether he can modify his own account or create new privileged users.
Andrew can do this by attempting to:
- Modify John’s IAM user account and see if the permission boundary prevents these actions.
- Create a new IAM user and check if John is restricted from assigning high-level permissions like AdministratorAccess.
If John is unable to perform these restricted actions, the permission boundary has been successfully implemented. If there are any issues, Andrew can adjust the policy accordingly.
Implementing an administrative boundary policy for John is a crucial step in ensuring that he can manage IAM resources without the risk of privilege escalation. By defining clear boundaries around the actions John can take, Andrew can prevent John from modifying his own account or granting excessive permissions to other users, thereby safeguarding the integrity of the IAM environment.
Creating and Applying the ‘iamuserboundary’ Policy for New Users
Now that John’s administrative boundary has been established, ensuring that he cannot escalate his own privileges or grant excessive permissions to others, the next step is to manage the permissions for any new users he creates. In this part, we will focus on creating the iamuserboundary policy, which will restrict the services and actions available to new IAM users John creates, ensuring they only have access to the services needed for their roles.
While John needs the ability to create new IAM users, it’s crucial that those users are granted restricted access, with predefined permissions that align with the organization’s security policies. This step will prevent John from inadvertently providing excessive access to new users or creating accounts with permissions beyond what has been authorized by the organization.
The Role of the ‘iamuserboundary’ Policy
The iamuserboundary policy will be applied to any IAM user created by John. This policy ensures that these new users are limited to specific AWS services and actions, in line with the organization’s requirements. By applying this policy, Andrew can ensure that new users only have access to the services they need, reducing the risk of unauthorized access to sensitive resources.
One of the key benefits of using a user boundary policy is that it allows Andrew to predefined the permissions that new users can be granted, ensuring consistency and security across all user accounts. This also prevents John from inadvertently granting new users more access than what is necessary for their role.
John will still have the ability to create new IAM users, but he will be constrained by the iamuserboundary policy, which ensures that these users are granted access to only a predefined set of services. In this case, the boundary will limit new users to specific services like S3, EC2, CloudWatch, VPC, and CloudFront. These are services that have been authorized for administrative tasks, but John will not be able to extend beyond this scope unless the policy is explicitly modified by an authorized administrator.
Defining the Permissions in the ‘iamuserboundary’ Policy
The iamuserboundary policy is a document that defines the permissions new users will have. The permissions specified in this policy will restrict the actions that can be performed on AWS services, ensuring that users have limited access to what is deemed necessary for their tasks.
The policy needs to allow new users to perform basic functions, such as managing their own password and obtaining access keys, but it should restrict them from performing any actions that would expose sensitive or unnecessary services. The idea here is to grant users the ability to interact with specific AWS services without granting them unnecessary or potentially dangerous permissions.
For example, the iamuserboundary policy might allow new users to:
- Access selected AWS services: The policy will allow new users to access specific AWS services, such as S3, EC2, VPC, CloudWatch, and CloudFront, which are needed for their daily tasks.
- Restrict other services: The policy will prevent access to any AWS services that are not directly related to the user’s role, such as administrative tools or highly sensitive data.
- Enable user self-management: The policy will allow new users to manage their own account details, such as changing their passwords or generating access keys. This is an important consideration for user self-service, which reduces the administrative overhead of managing passwords and keys.
Here is an overview of the permissions this policy will grant to new users:
- Access to selected AWS services: The iamuserboundary policy will grant users access to a defined list of services like S3, EC2, VPC, CloudWatch, and CloudFront.
- User self-management: Users will be able to update their own passwords and access keys but will not have permissions to modify others’ accounts or create new IAM roles.
- No elevated permissions: The policy will restrict any action that could potentially escalate privileges or allow unauthorized access to sensitive data or services.
Attaching the ‘iamuserboundary’ Policy to New Users
Once the iamuserboundary policy is created, it will need to be attached to any new users that John creates. The permission boundary policy will enforce the limits on the new users’ permissions, ensuring they can only access the specific services and actions allowed by the policy.
When John creates a new IAM user, he will be required to attach the iamuserboundary policy to that user’s account. This can be done during the user creation process in the AWS Management Console or through automation tools like AWS CLI or CloudFormation. By doing so, the new user will automatically have the restricted access defined in the iamuserboundary policy, and John will not be able to grant access to services outside the predefined set.
It’s important to note that John does not have the ability to modify or remove the iamuserboundary policy from new users. Since the boundary policy is enforced as part of the administrative policy, it remains intact unless authorized personnel modify it. This ensures that John cannot grant new users more access than is necessary for their role, thus maintaining the principle of least privilege.
Updating the ‘iamuserboundary’ Policy Over Time
As business needs evolve, new services may be introduced that require user access. In such cases, the iamuserboundary policy can be modified to grant access to new AWS services. However, this modification can only be done by an authorized administrator who has the necessary permissions to alter the policy.
For example, if John’s role expands and he needs to start working with additional services such as Lambda or RDS, the iamuserboundary policy can be updated to grant access to these services. This ensures that John can keep creating new users who have access to the most up-to-date set of services, without granting unnecessary permissions or making it easier for users to gain elevated access.
By modifying the iamuserboundary policy, Andrew can maintain control over the access levels granted to users, while ensuring that new users still adhere to the principle of least privilege. Any changes made to the policy should be carefully reviewed to ensure that they align with the organization’s security policies and do not inadvertently open up new risks.
The iamuserboundary policy plays a crucial role in ensuring that new IAM users created by John only have access to the services they need, while limiting their ability to perform actions that could lead to privilege escalation or unauthorized access to sensitive resources. By attaching this policy to new users, Andrew ensures that all users are granted appropriate permissions and that no one user has excessive access.
Final Thoughts
In any cloud environment, particularly in AWS, managing identity and access effectively is essential for maintaining both security and operational efficiency. The case of Andrew and John highlights a common challenge faced by organizations: how to delegate administrative responsibilities while ensuring security is not compromised. By implementing permission boundaries, Andrew can secure John’s IAM administrative access, ensuring he can perform his job without exposing the organization to the risk of privilege escalation.
The concept of permission boundaries is a powerful tool in AWS IAM for ensuring that users and roles are restricted to specific, necessary actions. In this case, Andrew used permission boundaries to prevent John from modifying his own account or granting elevated permissions to others. This allows John to manage IAM resources effectively while maintaining the principle of least privilege, which is a cornerstone of any solid security posture. By applying these boundaries, the risk of unintended privilege escalation or unauthorized access is minimized.
The additional layer of the iamuserboundary policy further tightens security by ensuring that any new users John creates are limited to only the services and permissions necessary for their roles. This ensures that John cannot inadvertently assign excessive privileges to new users, creating an environment where access is always carefully controlled.
The use of permission boundaries and user boundary policies not only improves security but also ensures that AWS resources are governed in a way that is both scalable and manageable. As the organization grows, these policies can be updated to reflect changing needs without compromising the security principles that were put in place from the start. The ability to update the iamuserboundary policy when new services are needed allows the organization to maintain flexibility while preventing unauthorized access.
In conclusion, by using permission boundaries and policies like iamuserboundary, organizations can delegate administrative duties safely and securely. This approach helps to ensure that users only have the permissions they need to do their jobs, prevents privilege escalation, and allows for secure and efficient management of AWS resources. As businesses continue to expand their use of cloud technologies, implementing and maintaining these security mechanisms will be critical in safeguarding data and operations from potential threats.
By focusing on least privilege, security controls, and effective management of IAM, organizations can confidently delegate responsibilities without risking exposure to unnecessary threats or vulnerabilities.