Faking a Certificate Check: Is it Possible?
Recently, I came across a question about faking a certificate check flow between two applications. The question raised concerns about the security of executable A, which verifies a certificate in assembly B. This article aims to shed light on this topic and address the potential risks involved.
Understanding the Scenario
The question posed was whether it is possible to modify executable A and skip the certificate check of assembly B. The assumption here is that assembly B is signed with a root CA trusted certificate.
The Importance of Write Access Control
The answer to this question lies in the control of write access to application binary modules. Standard users should not have write access to these modules. They should only be able to execute them, but not modify them. By restricting write access, the integrity of the certificate check process can be maintained.
Application Whitelisting for Added Security
In addition to controlling write access, application whitelisting can be implemented as an extra layer of security. Application whitelisting platforms allow for the control of which executables are allowed to run. Even if an attacker signs the modified executable A with a malicious self-signed certificate, the application whitelisting software will not recognize it as trusted, preventing its execution.
Conclusion
While it may be technically possible to modify executable A and skip the certificate check of assembly B, proper security measures can effectively mitigate this risk. By controlling write access to application binary modules and implementing application whitelisting, the integrity and security of the certificate check process can be maintained.