A policy can be attached to a user or group. This controls what the users are able to do in AWS.
Policy can be attached to an AWS service? What is the relation between policy and AWS service?
And where does the concept of Role fit in all this?
In Amazon Web Services (AWS), a user is a person or system that interacts with the AWS platform. Users can have different levels of access to AWS services and resources, depending on their permissions.
A group is a collection of users that share the same permissions. Groups can be used to manage the permissions of multiple users at once, making it easier to manage and control access to AWS services and resources.
A role is a set of permissions that can be assumed by a user or system. Roles are used to grant users and systems access to AWS services and resources, without having to share or manage long-term credentials. Roles can be temporary or permanent, and can be assumed by users, applications, or services.
A policy is a document that defines the permissions for a user, group, or role. Policies are written in the AWS Identity and Access Management (IAM) policy language, and specify the actions and resources that a user, group, or role is allowed to access.
AWS services are the core components of the AWS platform, and include a wide range of cloud-based services for computing, storage, networking, analytics, machine learning, and more. AWS services can be accessed by users, groups, and roles, depending on the permissions granted by policies.
In summary, the relation between user, group, role, policy, and AWS services is as follows:
A user is a person or system that interacts with AWS services.
A group is a collection of users that share the same permissions.
A role is a set of permissions that can be assumed by a user or system.
A policy is a document that defines the permissions for a user, group, or role.
AWS services are the core components of the AWS platform, and can be accessed by users, groups, and roles with the appropriate permissions.
Think of role like a container holder for permissions which can be used to delegate access to users, applications, or services that don't normally have access to your AWS resources.
From docs
An IAM role is an IAM identity that you can create in your account that has specific permissions. An IAM role is similar to an IAM user, in that it is an AWS identity with permission policies that determine what the identity can and cannot do in AWS. However, instead of being uniquely associated with one person, a role is intended to be assumable by anyone who needs it.
A policy is an object in AWS that, when associated with an identity or resource, defines their permissions. AWS evaluates these policies when an IAM principal (user or role) makes a request. Permissions in the policies determine whether the request is allowed or denied
On-premise administration of Linux VM's, we create identity like user, group and assign policies to the group identity. We do not think about role identity.
In AWS cloud, in addition to creating user & group identity,
we also create role identity, with permission policies that determine what the identity can and cannot do in AWS.
Role can be for example, service role(EC2->S3) or a simple role.
In AWS, What does role identity achieve that user & group identity doesn't?
Overview
As organizations across the world create new security policies that aim to minimize the risk and company exposure. System administrators have to opt-in for more complex administrative tasks related to credential management. AWS IAM Roles is a new tool that administrators can use to reduce administrative overhead related to password/key management. Roles could be looked at as extension of user/group permissions.
AWS IAM Roles
Roles allow resources (like EC2) to assume permissions and access resources without storing access keys in your source code. Also Roles automatically rotate keys, to limit exposure in case of key was compromised.
On Premise
Many organizations moving toward credential management solutions. Enterprise credential management software usually allows to force users to check-in/out passwords/keys, change passwords/keys on check-in preventing users from holding on to the passwords. Administrators also able to create custom policies to manage all aspect of key/password management. One example is LastPass having those features.
I understand the difference between roles and policies but the question
is why these two exists?
I mean why not use AWS Services with Policies?
thanks
IAM roles are similar to IAM users. We create roles to execute operations on required AWS Service.
For example: We can create a role that can perform a write operation
on DynamoDB table and assign that role to a lambda function. Then the
lambda function can use this role's privilege to write something on
DynamoDB.
Policies are simply JSON documents in which we can specify permissions: operations can be allowed or denied. Policies are attached to IAM identities such as users, groups and roles.
So the question is why both exists, why not use AWS service with Policies. The simple answer is we actually are using the AWS services with policies but in the name of IAM user or roles.
Policies get assigned to Roles. Roles do nothing on their own. You should use roles for services for simplicity and security. When assigning roles to a service you don't need to provide AWS access keys directly to these services anymore since they will be provided to the environment by the role. This is much more secure and simple then needing to pass these items to a service or application running on AWS and needing to secure them both on the service and in code.
I can't seem to find support for a surprisingly relevant issue. There are 10's of AWS services, so I want an AWS policy that restricts our users to only EC2, RDS and API Gateway. How do I do this? Can I 'deny all' and only endorse these specific services?
When you create a new IAM user, the default is all permissions denied.
If you want all users to have the same permissions, create a group. Assign each user to the group. You can also create multiple groups for different types of users.
Amazon has predefined policies that grant varying levels of permissions for each type of service. Select the policies that apply to your goals to the group(s).
Very easy to implement.
You can also create custom policies that define basically anything that you want. IAM policies range from the simple to the very complex.
You'll need to create Managed IAM policies for all users.
Tutorial
Creating IAM Policies
Example Access policies
You can also create Explicit Deny rules
Test IAM policies
What is the difference between an IAM role and an IAM user? The IAM FAQ has an entry explaining it, but it was vague and not very clear:
An IAM user has permanent long-term credentials and is used to directly interact with AWS services. An IAM role does not have any credentials and cannot make direct requests to AWS services. IAM roles are meant to be assumed by authorized entities, such as IAM users, applications, or an AWS service such as EC2.
I think an IAM role is used for federated logins (using an IdP with SAML tokens for example), and they don't have permanent access keys that you can download like regular IAM users have (the "an IAM role doesn't have any credentials" part).
What do they mean when they say an IAM role can't make direct requests to AWS services? I can login to AWS Console (the web console) and create stacks etc, so it can't be that.
To understand the difference, let us go through IAM basic knowledge
IAM controls: Who (authentication) can do What (authorization) in your AWS account.
Authentication(who) with IAM is done with users/groups and roles whereas authorization(what) is done by policies.
Here the term
User - End user think about people
Groups- a set of users under one set of permission(policies)
Roles - are used to grant specific permission to specific actors for a set of duration of time. These actors can be authenticated by AWS or some trusted external system.
User and roles use policies for authorization. Keep in mind that user and role can't do anything until you allow certain actions with a policy.
Answer the following questions and you will differentiate between a user and a role:
Can have a password? Yes-> user, No-> role
Can have an access key? Yes-> user, No-> role
Can belong to a group? Yes-> user, No -> role
Can be associated with AWS resources (for example EC2 instances)? No-> user, Yes->role
AWS supports 3 Role Types for different scenarios
AWS service roles (for example: EC2, Lambda, Redshift,...)
Cross-Account Access: granting permissions to users from other AWS account, whether you control those account or not.
Identity Provider Access: granting permissions to users authenticated by a trusted external system. AWS supports two kinds of identity federation:
- Web-based identity such as Facebook, Goolge- IAM support ingeration via OpenID Connect
- SAML 2.0 identity such as Active Directory, LDAP.
To understand what role is, you need to read its use case, I don't want to reinvent the wheel so please read the following AWS documents:
https://aws.amazon.com/blogs/security/how-to-use-a-single-iam-user-to-easily-access-all-your-accounts-by-using-the-aws-cli/
https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_providers_saml.html
Hope it helps.
Main actors in IAM are users, groups, roles and policies. And what you need to understand about AWS and never forget is that
Everything in AWS is an API
And to execute any API or any of its methods, first we have to authenticate and then authorize that particular user/group/role.
Ex: An operator wants to put an object to a S3 bucket. This process happens through a set of API calls within AWS. Basically we call the S3 API and a method of it to put the object into the particular bucket (say method put_object_in_s3). For that we may want to provide the name of the bucket, the object, and most importantly we need to provide set of credentials (username with password or secret key or etc) in order to tell the AWS API Engine who this user/group/role is.
The first thing API Engine does is, look at those credentials sent with the API. Then it validate those (whether they are correct, active) credentials indicating that this request is coming from a actual valid user, group or role. Then what the API Engine does is (as it now knows who sent this API request) it takes the policy documents associated with the particular operator (user or role) and evaluate them as a single view. That is we check whether the action called in the API is authorized for that operator.
IAM user - In the context of IAM, a user is a “permanent” named operator (human or machine). What’s important to note is that it’s credentials (credentials maybe username password or access key or a secret key) are permanent and stays with that named user. So by that AWS knows that what are the authentication methods (username password authentication method or secret key method or etc) for this user (as its permanent and stays with the user).
IAM group - As in the above image, a group is a collection of users. And note that a user can be in many groups as well.
IAM roles - Roles are not Permissions !!!. A role is also an authentication method just as IAM users and groups. As a user, a role is also a operator (could be a human, could be a machine). Difference is that credentials with roles are temporary.
Policy Documents - As stated earlier, roles are not Permissions. Permissions in AWS are completely handled by objects called Policy Documents. Policy Documents are JSON documents. Policy Documents can directly be attached to Users, Groups or Roles. When a policy document gets attached to any of above operator, then only they get permissions do stuff.
A policy document lists things like: Specific API or wildcard group of APIs that gets whitelisted against which resources, and Conditions for those API executions (like allow only if this user, group or role in the home network or allow from any location, allow only at certain times of day and etc)
Last but not least, Authentication in AWS is done via (IAM users,
groups and roles) whereas Authorization is done by Policies.
What do they mean when they say an IAM role can't make direct requests to AWS services? I can login to AWS Console (the web console) and create stacks etc, so it can't be that.
You are an IAM User (with some attached IAM Roles).
Think of IAM Roles as capabilities.
You give an IAM User capabilities (e.g. "can create Lambda function", "can upload to S3").
Note on Federated Users:
From http://docs.aws.amazon.com/IAM/latest/UserGuide/id.html:
A role can be assigned to a federated user who signs in by using an external identity provider instead of IAM. AWS uses details passed by the identity provider to determine which role is mapped to the federated user.
So, a federated user is similar to an IAM user which you can attach IAM Roles to. Except that you have an external identity provider.
Technically, you are NOT using a role as your identity when you login to AWS console. You are using your federated user account (with its own attached roles) as your identity.
An IAM user is an account which can be used by a person or an application. A user has credentials to log in and perform actions with the privileges assigned to that account.
An IAM role is something virtual that a resource can assume. For example, an EC2 instance can assume a role and execute AWS command with that assigned privileges. The same goes for other services like API gateway, Lambda, Kinesis, RDS and so on.
What do they mean when they say an IAM role can't make direct requests to AWS services?
The role itself is not able to perform any tasks since it has to be assumed by somebody or something. Somebody can also be someone logged in through identity federation and then assume a role.
I am practically new to AWS but I have implemented similar concepts in backend applications. Therefore, I would make an attempt to simplify this more from a newbie perspective.
IAM User - This is an actual account registered into the AWS IAM platform. This means that this is a person/application that is an actual entity. Note that this entity can do nothing, just an existence. Like when I signup for an application, my user entity is created and I can log in with provided credentials and have a profile.
IAM Group - This is a collection of specific users. Although this can also give identity, the focus is on the specific individuals that make the group. For example, how we group employees into departments in organizations based on their specific specialities and skillsets.
IAM Policies - This part seems easiest to understand. This is a specific rule/permission/access to a resource spelt out in clear dos and don'ts in a JSON format. Each policy is about a particular resource. A resource can be anything from an EBS volume, a Lamda Function, or even IAM itself.
IAM Role - This is like a title with specific responsibilities, i.e. a group of policies(permissions/access) that anyone with this title will have. For example, if we have a title of "Note-Taker", anyone from different departments can be assigned this title temporarily for a meeting, a period etc. And only those with this permission will be able to access the note-taking app. However, we can have some roles that will fit well with a group, e.g. all members of the accounting department can have the title of an accountant, which gives access to the books of account. But we can have another title of director, which has access to delete books of account, and this will cut across all departments.
Federated Users - These are entities also, but with no profile in the company(IAM). They are like contractors who can be assigned certain roles or titles through an acquired trust from the Federating platform as well as the access due to those titles. The good thing is that if the Federating platforms replace a user, there would be no reason to deactivate the old user and give access to the new one because the platform is the one with the access and not the "user".
IAM User - An user/application accessing AWS Resources
IAM Roles - Set of permissions/policy that can be applicable to an user or resource.
You can apply Roles to IAM user and to an AWS Resource too.
E.g., Apply IAM Role to Lambda Function. Function can only with that IAM Role.
IAM role is an entity which has specific access defined by the policy. And that access is. It doe snot have the permanent creds (Access keys and Secrets Access Keys)- it works on the "AssumeRole" method where token is granted for accessing the different AWs resources.
IAM User has the permanent access keys and secret access keys, we can define the permissions on the resources , IAM ROLE can be assumed by the IAM USER , as it has the keys - it can have access to the resources all the time...
IAM Policy (permissions- read,write etc.) apply to User,Group and Roles.
User- when a user want to access anything in AWS cloud, it must have IAM policy assigned.
Group - when a group of users is assigned with common IAM policy.
Roles - It needs when a service want to access another service. Service must be assigned with role that have policy assigned to perform certain actions in the AWS cloud. In other words, We can't directly assign policies on Service, first we need to create Role and then assign policy on that role.
Note: Roles are intended to be not used by physical people, instead use by AWS services only.