Password Spraying on Aws

Password spraying in AWS environments typically exploits authentication endpoints exposed through AWS services like Cognito, API Gateway, or custom Lambda functions. Unlike traditional password spraying that targets single accounts with common passwords, AWS-specific attacks often leverage federated identities and service accounts.

A common attack pattern involves targeting AWS Cognito User Pools. Attackers send authentication requests using a single password across multiple usernames, attempting to bypass account lockout mechanisms. Since Cognito implements per-user rate limiting rather than per-IP rate limiting, a sophisticated attacker can distribute attempts across multiple IP addresses using AWS services themselves.

// Vulnerable Cognito authentication pattern
const { CognitoIdentityServiceProvider } = require('aws-sdk');
const cognito = new CognitoIdentityServiceProvider();

async function authenticate(username, password) {
    try {
        const params = {
            AuthFlow: 'USER_PASSWORD_AUTH',
            ClientId: process.env.COGNITO_CLIENT_ID,
            AuthParameters: {
                USERNAME: username,
                PASSWORD: password
            }
        };
        
        const data = await cognito.initiateAuth(params).promise();
        return data.AuthenticationResult;
    } catch (err) {
        // Error may indicate invalid credentials
        // Attackers exploit predictable error messages
        return null;
    }
}

Another AWS-specific manifestation occurs through IAM role assumption. Attackers may attempt to assume roles using common passwords across multiple IAM users, exploiting the sts:AssumeRole API. The STS service provides detailed error messages that can help attackers distinguish between invalid credentials and insufficient permissions.

# AWS CLI password spraying attempt
for user in $(cat usernames.txt); do
    aws sts assume-role --role-arn arn:aws:iam::123456789012:role/target-role \
    --role-session-name $user --duration-seconds 3600 \
    --profile $user 2>/dev/null
    if [ $? -eq 0 ]; then
        echo "SUCCESS: $user"
        break
    fi
done

API Gateway endpoints protected by Lambda authorizers present another attack surface. When Lambda authorizers return generic error messages or have inconsistent response times, attackers can enumerate valid usernames before attempting password spraying.

Detecting password spraying in AWS environments requires monitoring specific AWS CloudTrail logs and CloudWatch metrics. The key is identifying unusual authentication patterns across multiple accounts or services.

CloudWatch metrics for Cognito User Pools provide built-in rate limiting indicators. Monitor SigninSuccesses and SigninFailures metrics for sudden spikes or unusual patterns. A legitimate user typically has a consistent failure rate before success, while password spraying shows many failures across different usernames.

# AWS Config rule for detecting password spraying
Resources:
  PasswordSprayDetection:
    Type: AWS::Config::ConfigRule
    Properties:
      ConfigRuleName: password-spray-detection
      Source:
        Owner: AWS
        SourceIdentifier: IAM_PASSWORD_POLICY
      Scope:
        ComplianceResourceTypes:
          - AWS::IAM::User
          - AWS::Cognito::UserPool

CloudTrail log analysis is crucial for detection. Look for patterns like multiple failed Authenticate or AssumeRole calls from the same IP or across multiple IPs within a short timeframe. The eventName field in CloudTrail logs reveals authentication attempts.

{
  "eventTime": "2024-01-15T10:30:00Z",
  "eventName": "Authenticate",
  "userIdentity": {
    "type": "IAMUser",
    "principalId": "AIDAJEXAMPLE...",
    "accountId": "123456789012"
  },
  "sourceIPAddress": "203.0.113.45",
  "awsRegion": "us-east-1",
  "errorCode": "NotAuthorizedException"
}

middleBrick's AWS-specific scanning identifies password spraying vulnerabilities by testing authentication endpoints with common password patterns. The scanner analyzes Cognito User Pool configurations, API Gateway authorizers, and IAM role assumptions to detect weak authentication implementations.

middleBrick tests for:

• Inadequate rate limiting on authentication endpoints
• Verbose error messages revealing valid usernames
• Missing account lockout mechanisms
• Insecure password policies

The scanner provides specific findings with severity levels and remediation guidance tailored to AWS services, helping teams understand their authentication surface area.

Remediating password spraying vulnerabilities in AWS requires implementing defense-in-depth strategies across authentication layers. Start with Cognito User Pool configuration to enforce strong security controls.

// Secure Cognito User Pool configuration
const userPoolConfig = {
    Policies: {
        PasswordPolicy: {
            MinimumLength: 12,
            RequireLowercase: true,
            RequireUppercase: true,
            RequireNumbers: true,
            RequireSymbols: true,
            TemporaryPasswordValidityDays: 7
        }
    },
    AdminCreateUserConfig: {
        InviteMessageTemplate: {
            EmailMessage: 'Your temporary password: {####}',
            EmailSubject: 'Your temporary password'
        }
    },
    AccountRecoverySetting: {
        RecoveryMechanisms: [
            {
                Name: 'verified_email',
                Priority: 1
            }
        ]
    }
};

Implement per-IP rate limiting using AWS WAF or API Gateway throttling. Configure API Gateway to limit requests per IP address and integrate with AWS WAF for advanced rate limiting rules.

# API Gateway with rate limiting
Resources:
  MyApi:
    Type: AWS::ApiGateway::RestApi
    Properties:
      Name: secure-api
  RateLimitedMethod:
    Type: AWS::ApiGateway::Method
    Properties:
      HttpMethod: POST
      ResourceId: !Ref MyResource
      RestApiId: !Ref MyApi
      AuthorizationType: COGNITO_USER_POOLS
      AuthorizerId: !Ref CognitoAuthorizer
      Integration:
        Type: AWS_PROXY
        IntegrationHttpMethod: POST
        Uri: !Sub
          - arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${lambdaArn}/invocations
          - lambdaArn: !GetAtt MyLambda.Arn
      MethodSettings:
        - HttpMethod: '*'
          ResourcePath: '/*'
          ThrottlingBurstLimit: 100
          ThrottlingRateLimit: 100

For IAM roles, implement conditional access policies that restrict role assumption based on source IP ranges, MFA requirements, and time-based conditions.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": "sts:AssumeRole",
      "Resource": "arn:aws:iam::123456789012:role/TargetRole",
      "Condition": {
        "Bool": {"aws:MultiFactorAuthPresent": true},
        "IpAddress": {"aws:SourceIp": ["203.0.113.0/24"]},
        "Date": {"aws:CurrentTime": ["2024-01-01T00:00:00Z", "2024-12-31T23:59:59Z"]}
      }
    }
  ]
}

Enable AWS CloudTrail and configure CloudWatch alarms to detect suspicious authentication patterns. Create alarms for unusual authentication failure rates or multiple failed attempts across different accounts.

{
  "AlarmName": "PasswordSprayDetection",
  "AlarmDescription": "Detects potential password spraying attacks",
  "MetricName": "SigninFailures",
  "Namespace": "AWS/Cognito",
  "Statistic": "Sum",
  "Period": 300,
  "EvaluationPeriods": 1,
  "Threshold": 50,
  "ComparisonOperator": "GreaterThanThreshold",
  "AlarmActions": ["arn:aws:sns:us-east-1:123456789012:SecurityAlerts"]
}

Implement AWS Config rules to continuously monitor authentication configurations and ensure compliance with security best practices. Use AWS Security Hub to aggregate findings and track remediation progress across your AWS organization.