Am 26.03.21 um 00:15 schrieb Antonio Quartulli: > Hi, > > On 25/03/2021 18:44, Arne Schwabe wrote: >> These have been troublesome in the past and also today's CVE-2021-3449 >> DOS is only exploitable if renegotiation is enabled. >> >> Signed-off-by: Arne Schwabe <a...@rfc2549.org> > > What is the practical effect of this change? > With the current code (before this patch) when would OpenSSL/mbedTLS > start a renegotiation on its own? >
Documentation from OpenSSL: SSL_OP_NO_RENEGOTIATION Disable all renegotiation in TLSv1.2 and earlier. Do not send HelloRequest messages, and ignore renegotiation requests via ClientHello. >From mbed TLS: Enable / Disable renegotiation support for connection when initiated by peer (Default: MBEDTLS_SSL_RENEGOTIATION_DISABLED) Warning It is recommended to always disable renegotation unless you know you need it and you know what you're doing. In the past, there have been several issues associated with renegotiation or a poor understanding of its properties. Note Server-side, enabling renegotiation also makes the server susceptible to a resource DoS by a malicious client. So for mbed TLS it was off by default anyway, this patch just doesn't trust the default for mbed TLS. Renegotiation is also dropped from TLS 1.3. Furthermore in TLS 1.2 you would use it to restart a session with diffferent parameter (now with client certs). So the is no real use case in OpenVPN to have it enabled. Arne _______________________________________________ Openvpn-devel mailing list Openvpn-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/openvpn-devel
