I'm trying to analyze a SSLv3 connection. The certificate of the server has a "MD5 with RSA" signature. So I was setting up a local man in the middle attack by setting up a local DNS server that would return a local IP address to the client. That local server would pipe the connection to the real server. However, the client immediately drops the connection, because it verifies the certificate, this suggests the binary is using certificate pinning. I don't have write access to the calling binary, therefore I can't just patch the cert-verification.
Is it possible to forge a certificate so the MD5 signatures collide, preventing the client from dropping the connection? I already read about HashClash, that it is indeed possible to create two certificates that have a colliding MD5 signature. But is it possible to do the same with a given certificate? If yes, is it possible in a reasonable amount of time?