Microsoft Intune MDM and Entra ID Leveraged to Elevate your Trust in Device Identity

Enhancing Device Identity Verification with Microsoft Intune MDM

Recent findings have identified significant insights within Microsoft Intune's Mobile Device Management (MDM) certificates. These discoveries offer a more robust mechanism for verifying device and tenant identities than conventional methods, such as registry values.

Issued to enrolled devices, these certificates contain Object Identifiers (OIDs) that, once decoded, expose unique GUIDs for the MDM Device ID and Entra ID Tenant ID, thereby enhancing device authentication reliability.

This development, outlined by Ben Whitmore, demonstrates how endpoint managers can utilize cryptographic data for reliable identity confirmation in enterprise environments.

The Intune MDM certificate guarantees secure communication between devices and the Intune service, incorporating non-human-readable extensions that contain crucial identifiers.

Researchers have identified two primary OIDs: 1.2.840.113556.5.4 for the MDM Device ID and 1.2.840.113556.5.14 for the Entra ID Tenant ID. Stored as mixed little-endian and big-endian byte arrays, these require specific reordering to form readable GUIDs.

Unlike registry values, which can be easily manipulated, these certificate-bound identifiers provide a trusted chain of trust backed by Microsoft's certification authorities.

The properties of the certificate, visible in tools like certmgr.msc, display byte arrays that require rearranging to reveal their significance, offering IT administrators a tamper-resistant alternative for auditing device enrollment.

Extracting meaningful data from these OIDs involves a specific byte reordering process. For the MDM Device ID (OID 1.2.840.113556.5.4), the first four bytes are reversed, followed by reversals of the next two pairs, while the final six bytes remain unchanged. For example, bytes 12 34 56 78 9A BC DE F0 12 34 56 78 90 AB CD EF transform into the GUID 78563412-BC9A-F0DE-1234-567890ABCDEF.

Similarly, the Entra ID Tenant ID (OID 1.2.840.113556.5.14) has a variant pattern with eight unchanged final bytes, converting sample data A1 B2 C3 D4 E5 F6 12 34 56 78 9A BC DE F0 01 23 A1 into F6E5D4C3-F6E5-3412-5678-9ABCDEF00123A1.

This method ensures high-confidence verification, as the data originates from trusted issuers like the Microsoft Intune MDM Device CA, mitigating risks from modifiable system artifacts.

Automation Tools for Certificate Decoding

To facilitate this process, developers at MSEndpointMgr have released a PowerShell script , Get-TenantInformation.ps1, available on GitHub. This script automates certificate discovery and decoding across LocalMachine and user profile stores.

The script searches for certificates issued by the Microsoft Intune MDM Device CA or MS-Organization-Access, validates their chain against expected root and intermediate authorities, and checks private key exportability using certutil for Key Storage Provider details.

It processes OIDs such as 1.2.840.113556.5.4 and 1.2.840.113556.5.14, reassembling bytes into GUIDs while outputting comprehensive details, including thumbprint, issuer, and trust status.

Running as an administrator reveals whether keys are TPM-protected, indicated by "Microsoft Platform Crypto Provider" versus software-only on older devices, highlighting potential vulnerabilities.

This tool enables admins to audit Entra ID join types and tenant regions from extensions like 1.2.840.113556.1.5.284.7, supporting proactive security management.

By prioritizing certificate OIDs over less secure alternatives, organizations can enhance device identity assurance, akin to choosing premium authentication over basic checks.

This approach not only strengthens trust but also aids in threat detection by verifying legitimate tenant associations. As Intune evolves, such techniques will be crucial for maintaining endpoint integrity.

Based on reporting by Cyber Security News.