From: Wilfred Mallawa <[email protected]> Currently, for TLS 1.3, ktls does not support record zero padding [1]. Record zero padding is used to allow the sender to hide the size of the traffic patterns from an observer. TLS is susceptible to a variety of traffic analysis attacks based on observing the length and timing of encrypted packets [2]. Upcoming Western Digital NVMe-TCP hardware controllers implement TLS 1.3. Which from a security perspective, can benefit from having record zero padding enabled to mitigate against traffic analysis attacks [2].
Thus, for TX, this series adds support to adding randomized number of zero padding bytes to end-of-record (EOR) records that are not full. This feature is disabled by default and can be enabled by the new TLS_TX_RANDOM_PAD socket option. TLS_TX_RANDOM_PAD allows users to set an upper bound for the number of bytes to be used in zero padding, and can be set back to 0 to disable zero padding altogher. The number of zero padding bytes to append is determined by the remaining record room and the user specified upper bound (minimum of the two). That is rand([0, min(record_room, upper_bound)]). Also a selftest is added to test the usage of TLS_TX_RANDOM_PAD. However, it does not test for zero padding bytes as that is stripped in the ktls RX path. Additional testing done on a linux NVMe Target with TLS by issuing an FIO workload to the target and asserting that the target kernel sees and strips the zero padding attached. [1] https://datatracker.ietf.org/doc/html/rfc8446#section-5.4l [2] https://datatracker.ietf.org/doc/html/rfc8446#appendix-E.3 Wilfred Mallawa (3): net/tls_sw: support randomized zero padding net/tls: add randomized zero padding socket option selftest: tls: add tls record zero pad test Documentation/networking/tls.rst | 21 +++++++++ include/net/tls.h | 1 + include/uapi/linux/tls.h | 2 + net/tls/tls.h | 6 ++- net/tls/tls_main.c | 72 +++++++++++++++++++++++++++++++ net/tls/tls_sw.c | 58 ++++++++++++++++++++----- tools/testing/selftests/net/tls.c | 45 +++++++++++++++++++ 7 files changed, 194 insertions(+), 11 deletions(-) -- 2.53.0
