Microsoft recently released a patch for a critical vulnerability in Microsoft Secure Channel (aka Schannel). This vulnerability is being referred to as MS14-066.
A description of how to trigger the MS14-066 ECDSA Heap Buffer Overflow vulnerability was posted by BeyondTrust, which also explained the research method used in narrowing down where this vulnerability presented itself. Their article mentions leveraging the OpenSSL s_client to authenticate to an IIS server, and by patching the s3_cInt.c file to fuzz the particular code path they were able to trigger a crash in memcpy. (BeyondTrust’s research team is to be thanked for saving others in our community a lot of work and time!)
Our researchers were able to write a demonstration program by patching the OpenSSL 1.0.1 source code to trigger this specific vulnerability and show how this could be used for exploitation.
The diff output is provided below: Continue reading "Code to Trigger MS14-066 ECDSA Server BOF Vulnerability"
