New research uncovers valuable insights hidden within Microsoft Intune’s Mobile Device Management (MDM) certificates, offering a more reliable way to verify device and tenant identities compared to traditional methods like registry values.
These certificates, issued to enrolled devices, contain Object Identifiers (OIDs) that, when properly decoded, reveal unique GUIDs for the MDM Device ID and Entra ID Tenant ID, enhancing trust in device authentication.
This discovery, detailed by Ben Whitmore, highlights how endpoint managers can leverage cryptographic data for robust identity confirmation in enterprise environments.
The Intune MDM certificate ensures secure communication between devices and the Intune service, embedding non-human-readable extensions that hold critical identifiers.
Researchers identified two key 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, both stored as mixed little-endian and big-endian byte arrays requiring specific reordering to form readable GUIDs.
Unlike registry values, which can be tampered with easily, these certificate-bound identifiers provide a chain of trust backed by Microsoft’s certification authorities.
Hidden OIDs in MDM Certificates
For instance, the certificate’s properties, visible in tools like certmgr.msc, show byte arrays that must be rearranged to unlock their meaning, offering IT admins a tamper-resistant alternative for auditing device enrollment.
Extracting meaningful data from these OIDs involves a precise byte reordering process, often discovered through trial and error.
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; using example bytes 12 34 56 78 9A BC DE F0 12 34 56 78 90 AB CD EF yields the GUID 78563412-BC9A-F0DE-1234-567890ABCDEF after transformation.
Similarly, the Entra ID Tenant ID (OID 1.2.840.113556.5.14) follows 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, reducing risks from modifiable system artifacts.
To streamline this process, developers at MSEndpointMgr released a PowerShell script, Get-TenantInformation.ps1, available on GitHub, which 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 like 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, according to Ben Whitmore.
Running as admin reveals whether keys are TPM-protected, indicated by “Microsoft Platform Crypto Provider” versus software-only on older devices, flagging potential vulnerabilities.
This tool empowers admins to audit Entra ID join types and tenant regions from extensions like 1.2.840.113556.1.5.284.7, fostering proactive security management.
By prioritizing certificate OIDs over less secure alternatives, organizations can build stronger device identity assurance, akin to choosing premium authentication over basic checks.
This approach not only elevates trust but also aids in threat detection by confirming legitimate tenant associations. As Intune evolves, such techniques will prove essential for maintaining endpoint integrity.
Follow us on Google News, LinkedIn, and X for daily cybersecurity updates. Contact us to feature your stories.
