Derek (freebsd lists) wrote: [...]
On 03/07/2014 07:36 PM, Xin Li wrote:On 03/07/14 14:50, A.J. Kehoe IV (Nanoman) wrote:Xin Li wrote:On 2014-03-07 11:13, A.J. Kehoe IV (Nanoman) wrote:Allan Jude wrote: [...]Honestly, my use case is just silently upgrading the strength of the hashing algorithm (when combined with my other feature request). Updating my bcrypt hashes from $2a$04$ to $2b$12$ or something. Same applies for the default sha512, maybe I want to update to rounds=15000Like this? http://www.freebsd.org/cgi/query-pr.cgi?pr=182518 Request for comments: http://docs.freebsd.org/cgi/mid.cgi?20140106205156.GD4903
[...]
My reasons for this were first to see if there was any interest from a committer to take this further. Much more likely to have a 15 or so line patch looked at, than one that touches stuff all over the place - I think. We are now at least having a conversation about it. It seemed to be a lot of work to specify rounds via login_setcryptfmt, with a bunch of changes also required in libcrypt. I don't have the resources to test for regressions in libcrypt, beyond the scope of whether login.conf works as expected (specifically, the ports tree, yp, ldap, or any other areas that I don't know about). If other developers were willing to work together on the api/abi changes, I would feel a lot better about spending my time there and doing it right. Without support from other, more knowledgeable people (as far as what will break if we do XYZ), who will eventually merge productive changes, I would be wasting my time. I don't want to be the libcrypt api changing pixie, scattering patches into /dev/null. :)
So far, I've seen five people say that they want this functionality: 2005-01-08: Steven Alexander Jr. 2012-12-05: Derek 2013-07-07: me 2013-10-29: jmg@ 2014-02-27: Allan Jude There will surely be more, and I think it's fair to say that none of us are sufficiently familiar with the many things that depend on libcrypt and libutil. To avoid breaking something, we need feedback from the people who would ultimately be committing these changes. Is this the correct mailing list to discuss this proposed feature?
My suggestion is that we either have: a) passwd_format and passwd_round (so that they don't conflict), orI recommend against this. By example, based on current scrypt modular crypt RFCs, there are multiple tunable parameters. It's conceivable that other future algorithms will have different functional and named parameters. Additionally, I think having all the parsing code for this scattered about actually makes things less clear. For example, $2a$08$ means a lot more to people (across different *nix backgrounds) than blf, is concise, and is/already should be well documented in crypt(3). Likewise with sha512. Looking at login.conf, you can't tell exactly what it means. Modular crypt is something that developers are working to stay compatible with (e.g. $5$, $6$, $2y$, etc), is understood outside of the context of FreeBSD system administration, and would be understood by people who are knowledgeable enough to seek to change this aspect of their system.
This is exactly what I meant. I completely agree.
b) extend passwd_format in a compatible manner to allow specifying a round, or,c) make passwd_format and passwd_modular conflict so we don't silently accept it and instead bail out when doing pwd_mkdb.As jmg suggested, by supplying the modular format for passwd_format, we eliminate this conflict, and make it obvious. I definitely support this notion.
Option C gets my vote too. Modular crypt is pretty standard across all implementations, whereas options A and B would require additional proprietary parsing, which I feel would be an unnecessarily more complex change.
That means touching login_setcryptfmt and friends, I think.What do you think of the idea of putting this into libcrypt instead of pam_unix.c, and then patching pam_unix.c and pw_user.c to reference libcrypt?Which part of the idea? I think it's a bad idea to make libcrypt to depend on libutil (for login_cap(3)) but we should probably provide new wrappers in login_cap(3) to do the common things when requested for various password manipulating tools to reduce duplicated code.Specifically: The makesalt aspect can/should be put into libcrypt, refined appropriately, and exposed publicly. It is a terrible little piece of code as it is now, twice (or more!), and it could be cleaned up considerably. This could be a nice little api. Secondly, since the digests are used externally, I think it would be good to push the custom base64 code out to a library somewhere, so there is the standard way to do it, documented. Maybe libcrypt is the right place for this function too, since that is the context in which I have seen it. I forget for sure now, but I think each algorithm is also responsible for base64 encoding their output. Not that I'm saying we should just rip it out, but it might be worthwhile to look case by case, if it's appropriate.
This is how I envision it too. The idea is not to have libcrypt depend on libutil, but rather the opposite. Currently, there are at least two places where this code is being used, and in my opinion, libcrypt would be a better place for it.
As far as autotuning the work-factor, I think that just being able to set it at all is a huge improvement, and autotuning is Just Details. We can see that this will be fraught with problems establishing consensus, and could stall making progress with the other good work. Even if every couple of years, the default in login.conf gets bumped to whatever. When people run mergemaster, it'll show, and the admin can decide then. As it is right now, rounds are fixed, that's not appropriate for any use-case, small or large. Finally, I agree the ability to auto-update existing digests is desirable. That and the other policy stuff can happen totally separate from the discussion around exposing the tunables.
I agree that these would be nice to have, and I agree that these should be discussed after we get the basic functionality. Like Derek said, we currently lack the ability to set this at all, or at least not without patching our systems first. Let's start with manual tuning. -- A.J. Kehoe IV (Nanoman) | /"\ ASCII Ribbon Campaign Nanoman's Company | \ / - No HTML/RTF in E-mail E-mail: nano...@nanoman.ca | X - No proprietary attachments WWW: http://www.nanoman.ca/ | / \ - Respect for open standards
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