Google Messages and Custom ROMs: Unveiling the RCS Compatibility Mystery

As fervent Android enthusiasts, we at Magisk Modules understand the allure of custom ROMs. They offer unparalleled customization, performance tweaks, and the chance to breathe new life into older devices. However, this freedom often comes with unexpected compromises. One such compromise, frustratingly common, is the disruption of Rich Communication Services (RCS) within Google Messages. This article delves deep into the reasons behind RCS incompatibility on custom ROMs, the newly implemented diagnostic features in Google Messages designed to shed light on this issue, and potential solutions for regaining RCS functionality on your modified Android device. We also provide information on related modules available from the Magisk Module Repository.

The RCS Promise and Its Challenges in the Custom ROM World

RCS is the modern successor to SMS, promising a richer, more interactive messaging experience. Think read receipts, typing indicators, high-resolution media sharing, and group chats with enhanced features. Google has been a major proponent of RCS, pushing for its widespread adoption as the universal standard for mobile communication. However, the very nature of custom ROMs—designed to alter the core system of Android—can inadvertently interfere with the delicate RCS implementation.

Why Custom ROMs Often Break RCS

The reasons behind RCS incompatibility are multi-faceted and often complex:

• Device Attestation Issues: Google relies on device attestation to verify the authenticity and security of devices connecting to its RCS infrastructure. Custom ROMs, by their very nature, alter the system’s fingerprint, often leading to attestation failures. This is particularly true for ROMs that are not properly signed or that have been modified in ways that invalidate their secure boot status. Google may interpret these altered fingerprints as signs of a compromised or illegitimate device, preventing RCS activation.
• Modified System Properties: Custom ROMs routinely modify system properties to fine-tune performance, enable specific features, or circumvent carrier restrictions. Unfortunately, some of these modifications can inadvertently affect the RCS client within Google Messages. Incorrectly configured or missing system properties can prevent the RCS client from properly initializing or connecting to Google’s servers.
• Incompatible Vendor Blobs: Android devices rely on vendor-specific binary blobs for hardware-level functionality. These blobs are typically provided by the device manufacturer and are optimized for the stock ROM. When flashing a custom ROM, using incompatible or outdated vendor blobs can lead to a wide range of issues, including RCS malfunctions. The RCS client often depends on specific vendor libraries for proper operation, and if these libraries are missing or incompatible, RCS will likely fail.
• Missing Carrier Configuration: RCS relies on specific carrier configurations to function correctly. These configurations define how the RCS client interacts with the carrier’s network and enable features like profile discovery and message routing. Custom ROMs may not include the necessary carrier configurations, or they may contain outdated configurations that are incompatible with the current RCS standards.
• Magisk and Module Interference: While Magisk is often used to enhance custom ROMs, certain modules can inadvertently interfere with RCS functionality. Modules that modify system properties, alter SELinux policies, or inject code into system processes can potentially disrupt the RCS client’s operation.

The Frustration of Silent RCS Failure

Previously, when RCS failed on a custom ROM, Google Messages provided little to no indication of the underlying cause. Users were simply left with a “Connecting…” message that never resolved, leaving them in the dark about the reason for the failure. This lack of transparency made troubleshooting extremely difficult, as users had no way of knowing whether the issue was related to their ROM, their carrier, or some other factor.

Google Messages’ New Diagnostic Feature: A Beacon of Hope

The latest versions of Google Messages now include a diagnostic feature designed to provide users with clearer explanations when RCS fails due to custom ROM modifications. This feature aims to address the frustration of silent failures by displaying a specific error message indicating that RCS has been disabled because of the custom ROM.

Decoding the “RCS Disabled Due to Custom ROM” Message

When Google Messages detects that your device is running a custom ROM that is interfering with RCS, it will display a message similar to: “RCS chats aren’t available because this device software is not supported.” or “RCS functionality is disabled because of your custom ROM”. This message, while not providing a detailed technical explanation, at least confirms that the custom ROM is the root cause of the problem.

Benefits of the New Diagnostic Feature

• Clear Identification of the Problem: The new message definitively points to the custom ROM as the source of the RCS issue, eliminating guesswork and saving users time and effort in troubleshooting.
• Informed Decision-Making: With a clear understanding of the problem, users can make informed decisions about whether to switch to a different ROM, attempt to fix the RCS issue, or simply accept the limitation and use SMS/MMS instead.
• Reduced Frustration: By providing a reason for the RCS failure, the new feature reduces the frustration associated with silent failures and empowers users to take appropriate action.

Potential Solutions for Restoring RCS on Custom ROMs

While the new diagnostic feature is helpful in identifying the problem, it doesn’t automatically fix it. Restoring RCS functionality on a custom ROM can be challenging and may require technical expertise. However, the following solutions may be worth exploring:

1. Clean Flashing the ROM:

A clean flash involves wiping all data partitions (system, data, cache, and sometimes internal storage) before installing the ROM. This ensures that there are no residual files or configurations from previous ROMs that could be interfering with RCS.

Procedure:

1. Backup Your Data: This is crucial as a clean flash will erase all data on your device.
2. Download the ROM: Obtain the latest version of your chosen custom ROM from a trusted source.
3. Boot into Recovery Mode: The method for entering recovery mode varies depending on your device. Consult your device’s documentation or online resources for specific instructions.
4. Wipe Data/Factory Reset: In recovery mode, select the “Wipe data/factory reset” option. Confirm your selection.
5. Flash the ROM: Use the recovery’s install function to flash the ROM zip file.
6. (Optional) Flash GApps: If the ROM doesn’t include Google apps, flash a GApps package after flashing the ROM.
7. Reboot: Reboot your device. The first boot may take longer than usual.

2. Reverting to Stock ROM (Temporarily):

Flashing back to the stock ROM can sometimes reset the device’s attestation status and allow RCS to activate. Once RCS is activated on the stock ROM, you can then try flashing the custom ROM again.

Procedure:

1. Obtain the Stock ROM: Download the stock ROM for your device from the manufacturer’s website or a trusted source.
2. Flash the Stock ROM: Use a flashing tool like Odin (for Samsung devices) or Fastboot to flash the stock ROM onto your device.
3. Activate RCS: Boot into the stock ROM and activate RCS in Google Messages.
4. Flash the Custom ROM: Flash the custom ROM again, following the clean flash procedure outlined above.

3. Magisk Module Solutions:

Several Magisk modules aim to fix RCS issues on custom ROMs by addressing specific problems like device attestation or missing carrier configurations. One module, known as Universal SafetyNet Fix, attempts to restore SafetyNet attestation, which can sometimes resolve RCS issues. Additionally, modules focused on spoofing device properties or injecting necessary carrier configurations may also be helpful. Search the Magisk Module Repository for relevant modules.

Important Considerations for Magisk Modules:

• Compatibility: Ensure that the module is compatible with your device, Android version, and custom ROM.
• Reliability: Use modules from trusted developers and read user reviews before installing.
• Potential Risks: Installing Magisk modules can potentially destabilize your system. Proceed with caution and create a backup before making any changes.

4. Manually Editing System Properties (Advanced):

This method involves manually editing system properties to match those of a device with working RCS. This requires root access and a text editor capable of editing system files. This method is highly technical and can lead to system instability if not performed correctly.

Procedure (Example - Highly Device Specific):

1. Identify Correct Properties: Research the system properties of a device known to have working RCS with your carrier.
2. Root Access: Ensure you have root access via Magisk.
3. Edit build.prop: Use a root-enabled file explorer to navigate to /system/build.prop. Make a backup of this file before editing!
4. Modify Properties: Carefully edit the properties in build.prop to match the values you identified. For example:
   • ro.product.manufacturer
   • ro.product.model
   • ro.build.fingerprint
5. Save and Reboot: Save the changes and reboot your device.

Warning: Incorrectly editing build.prop can brick your device. Proceed with extreme caution and only if you are comfortable with advanced Android customization.

5. Carrier Services Updates:

Ensure that you have the latest version of Carrier Services installed from the Google Play Store. Outdated versions of Carrier Services can sometimes cause RCS issues.

6. Contacting Your Carrier:

In some cases, the issue may be related to your carrier’s RCS implementation or your account provisioning. Contacting your carrier’s technical support may be helpful in resolving the problem.

The Future of RCS on Custom ROMs

The future of RCS on custom ROMs remains uncertain. As Google continues to tighten security measures and device attestation requirements, maintaining RCS compatibility on modified devices will likely become increasingly challenging. However, the Android community is resourceful and innovative, and we can expect to see continued efforts to find workarounds and solutions for restoring RCS functionality on custom ROMs. The efforts towards projects like microG, which aims to provide a free and open-source re-implementation of Google’s proprietary Android user space apps and libraries, may also play a significant role in the future of RCS on custom ROMs, allowing users to enjoy RCS without relying on Google’s services directly. Furthermore, as more custom ROM developers become aware of the RCS compatibility issues, they may begin to incorporate fixes and optimizations into their ROMs to ensure that RCS works out of the box. We at Magisk Modules will continue to monitor the situation and provide our users with the latest information and solutions.

Conclusion: Navigating the Complexities of RCS and Custom ROMs

The incompatibility between RCS and custom ROMs is a frustrating issue for many Android enthusiasts. The new diagnostic feature in Google Messages is a welcome step forward, providing users with much-needed clarity about the root cause of the problem. While restoring RCS functionality on a custom ROM can be challenging, the solutions outlined in this article offer a starting point for troubleshooting. Remember to proceed with caution, backup your data before making any changes, and consult trusted resources for guidance. By staying informed and persistent, you may be able to enjoy the benefits of RCS on your customized Android device.