boinc-client: Does not check the RSA_public_decrypt() return value.

The decrypt_public function in lib/crypt.cpp in the client in Berkeley Open Infrastructure for Network Computing (BOINC) 6.2.14 and 6.4.5 does not check the return value from the OpenSSL RSA_public_decrypt function, which allows remote attackers to bypass validation of the certificate chain via a malformed SSL/TLS signature, a similar vulnerability to CVE-2008-5077.