An Overview of AWS Identity and Access Management (IAM)

AWS Identity and Access Management (IAM) is a fundamental service that enables you to manage access to AWS services and resources securely. It provides fine-grained access control across all of AWS, allowing you to specify who can access which resources and under what conditions. IAM is crucial for implementing the principle of least privilege, ensuring that users and applications have only the permissions they need to perform their tasks.

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Core IAM Components

Users and Groups

IAM Users represent individual entities that need access to your AWS resources. Here's an example of creating an IAM user and group using CloudFormation:

Resources:
  DevelopersGroup:
    Type: 'AWS::IAM::Group'
    Properties:
      GroupName: Developers
      ManagedPolicyArns: 
        - arn:aws:iam::aws:policy/PowerUserAccess
      
  Developer:
    Type: 'AWS::IAM::User'
    Properties:
      UserName: john.doe
      Groups: 
        - !Ref DevelopersGroup
      LoginProfile:
        Password: !Ref 'UserPassword'
        PasswordResetRequired: true
      
  AccessKey:
    Type: 'AWS::IAM::AccessKey'
    Properties:
      UserName: !Ref Developer

Common User Types

User Type	Description	Common Permissions
Administrator	Full access to all resources	Admin policy
Developer	Access to development resources	PowerUser policy
Security Auditor	Read-only access for auditing	Security Audit policy
Application User	Limited access for specific apps	Custom scoped policy
Database Admin	Access to database services	Database admin policy

Roles and Policies

IAM Roles architecture and trust relationships:

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Example of a service role for EC2:

Resources:
  EC2ServiceRole:
    Type: 'AWS::IAM::Role'
    Properties:
      RoleName: EC2ServiceRole
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Effect: Allow
            Principal:
              Service: ec2.amazonaws.com
            Action: sts:AssumeRole
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/AmazonS3ReadOnlyAccess
        - arn:aws:iam::aws:policy/AmazonRDSReadOnlyAccess

Policy Types and Structure

Identity-Based Policies

Policy evaluation flow:

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Example of a custom policy with conditions:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "AllowEC2ManagementInRegion",
      "Effect": "Allow",
      "Action": [
        "ec2:RunInstances",
        "ec2:StartInstances",
        "ec2:StopInstances"
      ],
      "Resource": "*",
      "Condition": {
        "StringEquals": {
          "aws:RequestedRegion": ["us-east-1", "eu-west-1"]
        },
        "StringLike": {
          "ec2:InstanceType": ["t2.*", "t3.*"]
        }
      }
    }
  ]
}

Resource-Based Policies

Example S3 bucket policy with cross-account access:

Resources:
  SharedBucket:
    Type: 'AWS::S3::Bucket'
    Properties:
      BucketName: shared-resources-bucket
      
  BucketPolicy:
    Type: 'AWS::S3::BucketPolicy'
    Properties:
      Bucket: !Ref SharedBucket
      PolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Sid: AllowCrossAccountAccess
            Effect: Allow
            Principal:
              AWS: 'arn:aws:iam::ACCOUNT-ID:root'
            Action: 
              - s3:GetObject
              - s3:ListBucket
            Resource:
              - !Sub '${SharedBucket.Arn}/*'
              - !GetAtt SharedBucket.Arn

Security Best Practices

Password Policies and MFA

Password policy configuration using CloudFormation:

Resources:
  PasswordPolicy:
    Type: 'AWS::IAM::AccountPasswordPolicy'
    Properties:
      MinimumPasswordLength: 14
      RequireLowercaseCharacters: true
      RequireUppercaseCharacters: true
      RequireNumbers: true
      RequireSymbols: true
      MaxPasswordAge: 90
      PasswordReusePrevention: 24
      HardExpiry: true

MFA device lifecycle:

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Access Key Management

Access key rotation workflow:

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Monitoring and Compliance

Audit and Logging

CloudWatch dashboard for IAM monitoring:

Resources:
  IAMDashboard:
    Type: 'AWS::CloudWatch::Dashboard'
    Properties:
      DashboardName: IAMMonitoring
      DashboardBody: !Sub |
        {
          "widgets": [
            {
              "type": "metric",
              "properties": {
                "metrics": [
                  ["AWS/IAM", "AuthorizationSuccessCount"],
                  [".", "AuthorizationFailureCount"],
                  [".", "ConsoleSignInFailures"]
                ],
                "period": 300,
                "stat": "Sum",
                "region": "${AWS::Region}",
                "title": "IAM Authorization Metrics"
              }
            }
          ]
        }

Access Analyzer

Access Analyzer findings workflow:

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Common Use Cases

Cross-Account Access

Cross-account access pattern:

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Application Access Management

Example of an application IAM configuration:

Resources:
  ApplicationRole:
    Type: 'AWS::IAM::Role'
    Properties:
      RoleName: ApplicationServiceRole
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Effect: Allow
            Principal:
              Service: 
                - ecs-tasks.amazonaws.com
                - lambda.amazonaws.com
            Action: sts:AssumeRole
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole
      Policies:
        - PolicyName: ApplicationPermissions
          PolicyDocument:
            Version: '2012-10-17'
            Statement:
              - Effect: Allow
                Action:
                  - dynamodb:Query
                  - dynamodb:GetItem
                  - s3:GetObject
                Resource: '*'

Temporary Access Management

Temporary access workflow:

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