Case Study: Breaking a POS Android Application with SSL Pinning Bypass & Overly Permissive AWS Cognito Access

Client: A fintech company offering retail POS and loyalty services
Test Type: Mobile Application Penetration Testing (Android)
Assessment Style: Manual Testing + Attack Simulation
Test Environment: QA build of Android POS Application

Executive Summary

By circumventing SSL pinning and taking advantage of AWS Cognito misconfigurations, the Bluefire Redteam discovered serious vulnerabilities during a red team-style security evaluation of a production-like POS mobile application. These gave us complete access to cloud storage, including the ability to upload, download, and remove private data from several S3 buckets, as well as the ability to alter rewards and intercept authentication flows.

Key Findings at a Glance

Attack Simulation Overview

1. SSL Pinning Bypass Using Custom Injection

The app employed SSL pinning, but insecurely. We injected a custom Frida hook using Objection and bypassed certificate validation.

• Frida Hook Used: Modified checkServerTrusted() and HostnameVerifier
• Outcome: Full HTTPS traffic decryption in Burp Suite
• Impact: Cleartext access to AWS Cognito token requests, coupon redemption logic, and authentication headers

Frida Script:

Java.perform(function () {
    var X509TrustManager = Java.use("javax.net.ssl.X509TrustManager");
    X509TrustManager.checkServerTrusted.implementation = function () {
        console.log("[+] Bypassing checkServerTrusted()");
    };

    var HostnameVerifier = Java.use("javax.net.ssl.HostnameVerifier");
    HostnameVerifier.verify.implementation = function () {
        console.log("[+] Bypassing hostname verification");
        return true;
    };
});

Mapped to MITRE:

• T1471 – Application Layer Protocol (Decryption and Modification)

2. Coupon Redemption Tampering via Memory Hooking

Once decrypted, we intercepted reward redemption API traffic. By altering request parameters (e.g., coupon_quantity), we successfully redeemed 200 units instead of the intended 50.

• Technique: Modified HTTP requests via Burp after bypass
• Result: Loyalty points abuse, financial impact

3. Cognito Credential Misconfiguration & Cloud Takeover

We identified a GetCredentialsForIdentity request to Amazon Cognito. This returned temporary IAM credentials with unrestricted access across multiple S3 buckets.

Credentials Extracted:

{
"AccessKeyId": "ASIATONWR4YCGO6XKD4N",
"SecretKey": "••••••••••",
"SessionToken": "••••••••••"
}

Actions Performed with AWS CLI:

aws s3 ls
aws s3 cp s3://bucket-qa/private/data.json .
aws s3 cp exploit.txt s3://bucket/internal/
aws s3 rm s3://bucket/private/data.json

4. Sensitive AWS Configuration Files Embedded in App

We extracted the following files from the res/raw/ and asset directories:

• awsconfiguration.json: Included Cognito Pool IDs, App Client IDs, S3 bucket names
• amazon_root_cal.crt: Static pinned certificate embedded

Mapped to MITRE:

• T1602 – Data from Configuration Repository

Business Impact

Remediation Recommendations

1. Fix SSL Pinning using TrustManagerFactory with dynamic trust validation
2. Use least privilege IAM roles in Cognito Identity Pools
3. Avoid embedding sensitive AWS configurations in the app package
4. Enable CloudTrail, GuardDuty, and use Amazon S3 bucket policies with conditions

Final Thoughts

This example demonstrates how several layers of presumed security can be compromised by a single workaround (SSL pinning). Even when developed using AWS services, mobile apps can become extremely vulnerable if client trust boundaries are misaligned and configurations are too lax.

At Bluefire Redteam, we go beyond OWASP to simulate real-world, adversary-style attacks using MITRE ATT&CK and custom tooling to uncover hidden risks across the cloud and mobile layers.

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