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Simple Certificate Enrollment Protocol (SCEP) does not strongly authenticate certificate requests

Vulnerability Note VU#971035

Original Release Date: 2012-06-27 | Last Revised: 2018-12-14

Overview

Simple Certificate Enrollment Protocol (SCEP) does not strongly authenticate certificate requests made by users or devices. (Link updated 12/14/2018)

Description

IETF Internet-Draft draft-nourse-scep-23 "...defines a protocol, Simple Certificate Enrollment Protocol (SCEP), for certificate management and certificate and CRL queries in a closed environment." Mobile Device Management (MDM) is defined as "...software that secures, monitors, manages and supports mobile devices deployed across mobile operators, service providers and enterprises. MDM functionality typically includes over-the-air distribution of applications, data and configuration settings for all types of mobile devices, including mobile phones, smartphones, tablet computers, ruggedized mobile computers, mobile printers, mobile POS devices, etc." Multiple MDM software packages use SCEP as a method to handle certificate management and certificate CRL queries within an organization.

When a user or a device requests a certificate, the SCEP implementation may require a challenge password. It may be possible for a user or device to take their legitimately acquired SCEP challenge password and use it to obtain a certificate that represents a different user with a higher level of access such as a network administrator, or to obtain a different type of certificate than what was intended. It is also possible for SCEP implementations or system administrators to not require the challenge password, or to share a static password across many users.

Additional Notes:

  • SCEP was designed for use "...in a closed environment" and is not well suited for MDM and "bring your own device" (BYOD) applications where untrusted users and devices are in use.
  • Applications that use SCEP take different measures to authenticate users and devices.
  • draft-nourse-scep-23 discourages further use of SCEP:

    The IETF protocol suite currently includes two certificate management protocols with more comprehensive functionality: Certificate Management Protocol (CMP) [RFC4210] and Certificate Management over CMS (CMC) [RFC5272]. Environments that do not require interoperability with SCEP implementations SHOULD use the above-mentioned, PKIX-standard certificate management protocols. In light of the functionality gap between this specification [SCEP] and the two IETF standards track protocols, this specification is being published as Historic. Even when interoperability with the installed base of SCEP implementations is needed, implementers are encouraged to support one of these comprehensive standards track certificate management protocols in addition to the protocol defined in this specification.

Additional information can be found in Certified Security Solutions, Inc's The Use of the Simple Certificate Enrollment Protocol (SCEP) and Untrusted Devices whitepaper.

Impact

An attacker could elevate their permissions by requesting a certificate of a different, possibly higher privileged user that would allow them to access resources that they would not otherwise be able to access.

Solution

We are currently unaware of a practical solution to this problem.

Possible Workarounds

  • Use Certificate Management Protocol (CMP) or Certificate Management over CMS as a replacement for Simple Certificate Enrollment Protocol (SCEP)
  • Manually approve for certificates from unknown sources
  • Avoid reusing challenge passwords
  • Limit the number of individuals who can request certificates

Vendor Information

971035
 
Affected   Unknown   Unaffected

Apple Inc.

Notified:  April 12, 2012 Updated:  June 29, 2012

Status

  Not Affected

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

Vendor References

    Asavie Technologies Ltd

    Updated:  September 21, 2012

    Status

      Not Affected

    Vendor Statement

    We provide a product called iSimplyConnect, which uses leverages Apple's SCEP client. We are not impacted by this vulnerability.

    Vendor Information

    We are not aware of further vendor information regarding this vulnerability.

    Cisco Systems, Inc.

    Notified:  April 12, 2012 Updated:  June 29, 2012

    Status

      Not Affected

    Vendor Statement

    No statement is currently available from the vendor regarding this vulnerability.

    Vendor Information

    We are not aware of further vendor information regarding this vulnerability.

    Vendor References

      GlobalSign

      Updated:  March 29, 2013

      Status

        Not Affected

      Vendor Statement

      GlobalSign www.globalsign.com utilizes SCEP for certificate delivery to iOS devices. However we have mitigated the vulnerabilities outlined in 971035 by:


        1)implementing unique and strong one time PINs to authenticate certificate invitation
        2)Utilize unique 1-time SCEP URLs that optionally can be tied to Device ID
        3)only allow authorized Enteprise PKI local RAs to register end user identity information using client authentication to access the ePKI portal
        4)only issue identity information entered in the ePKI portal regardless of what is included in the CSR.

        Therefore, GlobalSign believes we are not affected by the vulnerabilities outlined in 971035.

      Vendor Information

      We are not aware of further vendor information regarding this vulnerability.

      Microsoft Corporation

      Notified:  April 05, 2012 Updated:  June 29, 2012

      Status

        Not Affected

      Vendor Statement

      No statement is currently available from the vendor regarding this vulnerability.

      Vendor Information

      We are not aware of further vendor information regarding this vulnerability.

      Vendor References

        MobileIron

        Updated:  August 20, 2012

        Status

          Not Affected

        Vendor Statement

        No statement is currently available from the vendor regarding this vulnerability.

        Vendor Information

        We are not aware of further vendor information regarding this vulnerability.

        SilverbackMDM

        Updated:  July 04, 2012

        Status

          Not Affected

        Vendor Statement

        No statement is currently available from the vendor regarding this vulnerability.

        Vendor Information

        We are not aware of further vendor information regarding this vulnerability.

        Vendor References

        Zenprise

        Notified:  April 12, 2012 Updated:  June 29, 2012

        Status

          Not Affected

        Vendor Statement

        No statement is currently available from the vendor regarding this vulnerability.

        Vendor Information

        We are not aware of further vendor information regarding this vulnerability.

        Vendor References

          McAfee

          Notified:  April 12, 2012 Updated:  April 12, 2012

          Status

            Unknown

          Vendor Statement

          No statement is currently available from the vendor regarding this vulnerability.

          Vendor Information

          We are not aware of further vendor information regarding this vulnerability.


          CVSS Metrics

          Group Score Vector
          Base 1.4 AV:A/AC:H/Au:S/C:P/I:N/A:N
          Temporal 1 E:U/RL:W/RC:UC
          Environmental 0.5 CDP:L/TD:L/CR:ND/IR:ND/AR:ND

          References

          Acknowledgements

          Thanks to Ted Shorter of Certified Security Solutions for reporting this vulnerability.

          This document was written by Michael Orlando and Art Manion.

          Other Information

          CVE IDs: None
          Date Public: 2012-06-27
          Date First Published: 2012-06-27
          Date Last Updated: 2018-12-14 17:19 UTC
          Document Revision: 61

          Sponsored by the Department of Homeland Security Office of Cybersecurity and Communications.