nss: signature forgery

The definite_length_decoder function in lib/util/quickder.c in Mozilla
Network Security Services (NSS) does not ensure that the DER encoding of
an ASN.1 length is properly formed, which allows remote attackers to
conduct data-smuggling attacks by using a long byte sequence for an
encoding, as demonstrated by the SEC_QuickDERDecodeItem function’s
improper handling of an arbitrary-length encoding of 0x00.

This update also adds support for the TLS Fallback Signaling Cipher
Suite Value (TLS_FALLBACK_SCSV) in NSS, which can be used to prevent
protocol downgrade attacks against applications which re-connect using a
lower SSL/TLS protocol version when the initial connection indicating
the highest supported protocol version fails. This can prevent a
forceful downgrade of the communication to SSL 3.0, mitigating
CVE-2014-3566, also known as POODLE. SSL 3.0 support has also been
disabled by default in this Firefox and Thunderbird update, further
mitigating POODLE.