On Wed, Jun 15, 2022 at 5:33 AM James Ralston <ralston@xxxxxxxxx> wrote: > On Mon, Jun 13, 2022 at 4:34 AM Jochen Bern <Jochen.Bern@xxxxxxxxx> wrote: > > > On 10.06.22 16:50, Dmitry Belyavskiy wrote: > > > > > There is a need to increase RSA key requirements to make the > > > installations more secure. Just updating the default compiled-in > > > value isn't an option because it may significantly break legacy > > > systems compatibility. This PR [1] introduces a new configuration > > > option MinRSABits to be managed for security's sake. > > > > > > If this approach is OK for upstream, please let me know and I will > > > improve this PR according to the feedback. > > > > I realize that with the *current* selection of algorithms available > > in OpenSSH, fine-grained control of minimum key size almost(!) is an > > RSA-only topic, but nonetheless I wonder whether newly-defined > > config syntax thereto should be aimed at extensibility to other > > cryptalgorithms ... > > That ship sailed long ago: > > $ grep SSH_RSA_MINIMUM_MODULUS_SIZE sshkey.h > #define SSH_RSA_MINIMUM_MODULUS_SIZE 1024 > > It’s not worth it to attempt to refactor this approach, as with both > the ecdsa family and ed25519, the cipher name specifies the security > strength. > > Dmitry’s merge request both defaults MinRSABits to > SSH_RSA_MINIMUM_MODULUS_SIZE, and prohibits setting MinRSABits to > anything less than SSH_RSA_MINIMUM_MODULUS_SIZE. So unless the > administrator specifically sets MinRSABits to something greater than > 1024, it will not change the behavior of OpenSSH. It also documents > MinRSABits in the man pages, and includes MinRSABits in “ssh -G” > output. All of this seems perfectly reasonable. > I also need to adjust tests. > NIST Special Publication 800-131A (1) prohibits the use of RSA keys > with len(n) < 2048 for all uses but legacy digital signature > verification, and an increasing number of sites (including ours) must > comply with NIST SP 800-131A. Having the MinRSABits option would make > our lives easier with respect to compliance. > > (1) https://doi.org/10.6028/NIST.SP.800-131Ar2 Yes, and this was a part of my (unwritten) rationale :) -- Dmitry Belyavskiy _______________________________________________ openssh-unix-dev mailing list openssh-unix-dev@xxxxxxxxxxx https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev
