Erlang/OTP 19.3.6.4

Note! The ssl-8.1.3.1 application can *not* be applied independently of other applications on an arbitrary OTP 19 installation. On a full OTP 19 installation, also the following runtime dependency has to be satisfied: -- stdlib-3.2 (first satisfied in OTP 19.2)

OTP-14748

Application(s):

ssl

An erlang TLS server configured with cipher suites using rsa key exchange, may be vulnerable to an Adaptive Chosen Ciphertext attack (AKA Bleichenbacher attack) against RSA, which when exploited, may result in plaintext recovery of encrypted messages and/or a Man-in-the-middle (MiTM) attack, despite the attacker not having gained access to the server’s private key itself. CVE-2017-1000385

Exploiting this vulnerability to perform plaintext recovery of encrypted messages will, in most practical cases, allow an attacker to read the plaintext only after the session has completed. Only TLS sessions established using RSA key exchange are vulnerable to this attack.

Exploiting this vulnerability to conduct a MiTM attack requires the attacker to complete the initial attack, which may require thousands of server requests, during the handshake phase of the targeted session within the window of the configured handshake timeout. This attack may be conducted against any TLS session using RSA signatures, but only if cipher suites using RSA key exchange are also enabled on the server. The limited window of opportunity, limitations in bandwidth, and latency make this attack significantly more difficult to execute.

RSA key exchange is enabled by default although least prioritized if server order is honored. For such a cipher suite to be chosen it must also be supported by the client and probably the only shared cipher suite.

Captured TLS sessions encrypted with ephemeral cipher suites (DHE or ECDHE) are not at risk for subsequent decryption due to this vulnerability.

As a workaround if default cipher suite configuration was used you can configure the server to not use vulnerable suites with the ciphers option like this:

{ciphers, [Suite || Suite <- ssl:cipher_suites(), element(1,Suite) =/= rsa]}

that is your code will look somethingh like this:

ssl:listen(Port, [{ciphers, [Suite || Suite <- ssl:cipher_suites(), element(1,S) =/= rsa]} | Options]).

Thanks to Hanno Böck, Juraj Somorovsky and Craig Young for reporting this vulnerability.

Full runtime dependencies of ssl-8.1.3.1: crypto-3.3, erts-7.0, inets-5.10.7, kernel-3.0, public_key-1.2, stdlib-3.2