Before this commit, the save-entropy script rotates entropy files
like logs. This involves creating a new file that holds the entropy
and renaming of all existing entropy files. However, the entropy
data do not really need to be kept in a particular order, and
replacing the oldest file is sufficient.
This commit replaces the rotation with a scan in the
[1..entropy_save_num] space that finds the first empty slot, or
the slot of the oldest file, and writes entropy into that slot.
This also fixes an issue that prevents save-entropy from saving
any entropy when there is one non-regular file in any slot as a
side effect.
Based on an earlier patch from peterj@.
PR: 134225
Reported by: peterj
Reviewed by: csprng (cem, markm)
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D22612
Tag saved entropy files as "nodump," to signal that the files should not be
backed up by dump(8) or other automated backup software that honors the file
flag.
Do not produce an error if the target file resides on a filesystem that does
not support file flags (e.g., msdos /boot).
Reviewed by: delphij
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D20358
The goal of saving entropy in Fortuna is two-fold: (1) to provide early
availability of the random device (unblocking) on next boot; and (2), to
have known, high-quality entropy available for that initial seed. We know
it is high quality because it's output taken from Fortuna.
The FS&K paper makes it clear that Fortuna unblocks when enough bits have
been input that the output //may// be safely seeded. But they emphasize
that the quality of various entropy sources is unknown, and a saved entropy
file is essential for both availability and ensuring initial
unpredictability.
In FreeBSD we persist entropy using two mechanisms:
1. The /etc/rc.d/random shutdown() function, which is used for ordinary
shutdowns and reboots; and,
2. A cron job that runs every dozen minutes or so to persist new entropy, in
case the system suffers from power loss or a crash (bypassing the
ordinary shutdown path).
Filesystems are free to cache dirty data indefinitely, with arbitrary flush
policy. Fsync must be used to ensure the data is persisted, especially for
the cron job save-entropy, whose entire goal is power loss and crash safe
entropy persistence.
Ordinary shutdown may not need the fsync because unmount should flush out
the dirty entropy file shortly afterwards. But it is always possible power
loss or crash occurs during the short window after rc.d/random shutdown runs
and before the filesystem is unmounted, so the additional fsync there seems
harmless.
PR: 230876
Reviewed by: delphij, markj, markm
Approved by: secteam (delphij)
Differential Revision: https://reviews.freebsd.org/D19742
Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.
The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
No functional change intended.
Off by default, build behaves normally.
WITH_META_MODE we get auto objdir creation, the ability to
start build from anywhere in the tree.
Still need to add real targets under targets/ to build packages.
Differential Revision: D2796
Reviewed by: brooks imp
This code has had an extensive rewrite and a good series of reviews, both by the author and other parties. This means a lot of code has been simplified. Pluggable structures for high-rate entropy generators are available, and it is most definitely not the case that /dev/random can be driven by only a hardware souce any more. This has been designed out of the device. Hardware sources are stirred into the CSPRNG (Yarrow, Fortuna) like any other entropy source. Pluggable modules may be written by third parties for additional sources.
The harvesting structures and consequently the locking have been simplified. Entropy harvesting is done in a more general way (the documentation for this will follow). There is some GREAT entropy to be had in the UMA allocator, but it is disabled for now as messing with that is likely to annoy many people.
The venerable (but effective) Yarrow algorithm, which is no longer supported by its authors now has an alternative, Fortuna. For now, Yarrow is retained as the default algorithm, but this may be changed using a kernel option. It is intended to make Fortuna the default algorithm for 11.0. Interested parties are encouraged to read ISBN 978-0-470-47424-2 "Cryptography Engineering" By Ferguson, Schneier and Kohno for Fortuna's gory details. Heck, read it anyway.
Many thanks to Arthur Mesh who did early grunt work, and who got caught in the crossfire rather more than he deserved to.
My thanks also to folks who helped me thresh this out on whiteboards and in the odd "Hallway track", or otherwise.
My Nomex pants are on. Let the feedback commence!
Reviewed by: trasz,des(partial),imp(partial?),rwatson(partial?)
Approved by: so(des)
As of r126744, we no longer feed the entropy device in jails upon
start, and collecting them is no longer useful.
PR: conf/126744
Submitted by: Eugene Grosbein <eugen grosbein net> (with minor changes)
MFC after: 1 week
Approved by: so (des)
all in one command, with no permissions race.
2. Simplify the rotation logic by cd'ing into the directory, with a test
to make sure that it succeeds.
3. Remove any files numbered higher than entropy_save_num. This helps when
the user reduces the number, and may be useful for other purposes down
the road.
4. Simplify the rotation logic by first testing the common case (it's a
regular file) then testing if something else exists with the same name
using elif. Also switch from using jot to simpler countdown format.
5. Fix logger lines and error messages to be more consistent, and wrap the
code more consistently in the 80 column range. The "not a regular file"
error message was mistakenly wrapped entirely in "quotes" which caused
logger to include line-wrapping whitespace. Change that to wrap only
the variables in quotes, which is both consistent and works better.
6. Update copyright to reflect the fact that changes were made this year.
Parts of 2-4 were taken from etc/periodic/daily/310.accounting
ignoring errors when sourcing rc.conf* files. The most common error
occurs when users put a command of some sort into those files.
(ifconfig is a popular choice)
2. Make the file rotation logic simpler by starting one down from
the "top" of the list, rather than at the top.
3. Try to make file rotation more secure by calling unlink(1) on all
new file names before rotating an old file to the new name, rather than
merely calling 'rm -f' on any files that exceed the number of files
to save.
rc.conf[.local]. Fix this, and leave the default as 2048.
Update the copyright year to include the present.
Update the assignment of the copyright to be me personally,
instead of "The FreeBSD Project" which is not a legal entity,
and therefore not a proper assignee. My intention remains the
same however, that this code continue to be BSD licensed, and
freely available to anyone that wants it under those terms.
PR: conf/75722
Submitted by: Nicolas Rachinsky <list@rachinsky.de>
it at boot time closer to the way we want it to be in the final version.
* Move the default directory to /var/db/entropy
* Run the entropy saving cron job every 11 minutes. This seems
to be a better default, although still bikeshed material.
* Feed /dev/random some cheesy "entropy" from various commands
and files before the disks are mounted. This gives /dev/random
a better chance of running without blocking early.
* Move the reseeding with previously stored entropy to the point
immediately after the disks are mounted.
* Make the harvesting script a little safer in regards to the
possibility of accidentally overwriting something other
than a regular file.
it can be used to reseed at boot time. This will greatly increase
the chances that there will be sufficient entropy available at
boot time to prevent long delays.
For /etc/rc, remove the vmstat and iostat runs from the attempt
to provide some cheesy randomness if the files fail, since
those programs are dynamically linked, and ldd seems to want
some randomness to do its magic.
Guidance and parameters for this project were provided by
Mark Murray, based on the requirements of the Yarrow
algorithm. Some helpful suggestions for implementation
(including the tip about iostat and vmstat) were provided
by Sheldon Hearn. All blame for problems or mistakes is
mine of course.
