CVE-2016-2107

La implementación de AES-NI en OpenSSL en versiones anteriores a 1.0.1t y 1.0.2 en versiones anteriores a 1.0.2h no considera la asignación de memoria durante una comprobación de relleno determinada, lo que permite a atacantes remotos obtener información de texto claro sensible a través de un ataque de padding-oracle contra una sesión AES CBC . NOTA: esta vulnerabilidad existe debido a una corrección incorrecta para CVE-2013-0169.

It was discovered that OpenSSL leaked timing information when decrypting TLS/SSL and DTLS protocol encrypted records when the connection used the AES CBC cipher suite and the server supported AES-NI. A remote attacker could possibly use this flaw to retrieve plain text from encrypted packets by using a TLS/SSL or DTLS server as a padding oracle.

The padding check in AES-NI CBC MAC was rewritten to be in constant time by making sure that always the same bytes are read and compared against either the MAC or padding bytes. But it no longer checked that there was enough data to have both the MAC and padding bytes. [CVE-2016-2107] An overflow can occur in the EVP_EncodeUpdate() function which is used for Base64 encoding of binary data. [CVE-2016-2105] An overflow can occur in the EVP_EncryptUpdate() function, however it is believed that there can be no overflows in internal code due to this problem. [CVE-2016-2106] When ASN.1 data is read from a BIO using functions such as d2i_CMS_bio() a short invalid encoding can casuse allocation of large amounts of memory potentially consuming excessive resources or exhausting memory. [CVE-2016-2109] ASN1 Strings that are over 1024 bytes can cause an overread in applications using the X509_NAME_oneline() function on EBCDIC systems. [CVE-2016-2176] FreeBSD does not run on any EBCDIC systems and therefore is not affected. A MITM attacker can use a padding oracle attack to decrypt traffic when the connection uses an AES CBC cipher and the server support AES-NI. [CVE-2016-2107] If an attacker is able to supply very large amounts of input data then a length check can overflow resulting in a heap corruption. [CVE-2016-2105] Any application parsing untrusted data through d2i BIO functions are vulnerable to memory exhaustion attack. [CVE-2016-2109] TLS applications are not affected.