CVE-2015-0205

La función ssl3_get_cert_verify en s3_srvr.c en OpenSSL 1.0.0 anterior a 1.0.0p y 1.0.1 anterior a 1.0.1k acepta la autenticación de clientes con un certificado Diffie-Hellman (DH) sin necesidad de un mensaje CertificateVerify, lo que permite a atacantes remotos obtener el acceso sin conocimiento de una clave privada a través de trafico TLS Handshake Protocol manipulado a un servidor que reconoce una autoridad de certificación con soporte DH.

It was found that an OpenSSL server would, under certain conditions, accept Diffie-Hellman client certificates without the use of a private key. An attacker could use a user's client certificate to authenticate as that user, without needing the private key.

A carefully crafted DTLS message can cause a segmentation fault in OpenSSL due to a NULL pointer dereference. A memory leak can occur in the dtls1_buffer_record function under certain conditions. When OpenSSL is built with the no-ssl3 option and a SSL v3 ClientHello is received the ssl method would be set to NULL which could later result in a NULL pointer dereference. An OpenSSL client will accept a handshake using an ephemeral ECDH ciphersuite using an ECDSA certificate if the server key exchange message is omitted. An OpenSSL client will accept the use of an RSA temporary key in a non-export RSA key exchange ciphersuite. An OpenSSL server will accept a DH certificate for client authentication without the certificate verify message. OpenSSL accepts several non-DER-variations of certificate signature algorithm and signature encodings. OpenSSL also does not enforce a match between the signature algorithm between the signed and unsigned portions of the certificate. Bignum squaring (BN_sqr) may produce incorrect results on some platforms, including x86_64.