cdda67de03
Commit05cd988dce("wrapper: add a helper to generate numbers from a CSPRNG", 2022-01-17) added a csprng_bytes() function which used one of several interfaces to provide a source of cryptographically secure pseudorandom numbers. The CSPRNG_METHOD make variable was provided to determine the choice of available 'backends' for the source of random bytes. Commit05cd988dcedid not set CSPRNG_METHOD in the Linux section of the config.mak.uname file, so it defaults to using '/dev/urandom' as the source of random bytes. The 'backend' values which could be used on Linux are 'arc4random', 'getrandom' or 'getentropy' ('openssl' is an option, but seems to be discouraged). The arc4random routines (arc4random_buf() is the one actually used) were added to glibc in version 2.36, while both getrandom() and getentropy() were included in 2.25. So, some of the more up-to-date distributions of Linux (eg Debian 12, Ubuntu 24.04) would be able to use the 'arc4random' setting. All currently supported distributions have glibc 2.25 or later (RHEL 8 has v2.28) and, therefore, have support for the 'getrandom' and 'getentropy' settings. The arc4random routines on the *BSDs (along with cygwin) implement the ChaCha20 stream cipher algorithm (see RFC8439) in userspace, rather than as a system call, and are thus somewhat faster (having avoided a context switch to the kernel). In contrast, on Linux all three functions are simple wrappers around the same kernel CSPRNG syscall. If the meson build system is used on a newer platform, then they will be configured to use 'arc4random', whereas the make build will currently default to using '/dev/urandom' on Linux. Since there is no advantage, in terms of performance, to the 'arc4random' setting, the 'getrandom' setting should be preferred from an availability perspective. (Also, the current uses of csprng_bytes() are not in any hot path). In order to set an appropriate default, set the CSPRNG_METHOD build variable to 'getrandom' in the Linux section of the 'config.mak.uname' file. Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
Git is a fast, scalable, distributed revision control system with an unusually rich command set that provides both high-level operations and full access to internals.
Git is an Open Source project covered by the GNU General Public License version 2 (some parts of it are under different licenses, compatible with the GPLv2). It was originally written by Linus Torvalds with help of a group of hackers around the net.
Please read the file INSTALL for installation instructions.
Many Git online resources are accessible from https://git-scm.com/ including full documentation and Git related tools.
See Documentation/gittutorial.adoc to get started, then see
Documentation/giteveryday.adoc for a useful minimum set of commands, and
Documentation/git-<commandname>.adoc for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with man gittutorial or git help tutorial, and the
documentation of each command with man git-<commandname> or git help <commandname>.
CVS users may also want to read Documentation/gitcvs-migration.adoc
(man gitcvs-migration or git help cvs-migration if git is
installed).
The user discussion and development of Git take place on the Git mailing list -- everyone is welcome to post bug reports, feature requests, comments and patches to git@vger.kernel.org (read Documentation/SubmittingPatches for instructions on patch submission and Documentation/CodingGuidelines).
Those wishing to help with error message, usage and informational message
string translations (localization l10) should see po/README.md
(a po file is a Portable Object file that holds the translations).
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Issues which are security relevant should be disclosed privately to the Git Security mailing list git-security@googlegroups.com.
The maintainer frequently sends the "What's cooking" reports that list the current status of various development topics to the mailing list. The discussion following them give a good reference for project status, development direction and remaining tasks.
The name "git" was given by Linus Torvalds when he wrote the very first version. He described the tool as "the stupid content tracker" and the name as (depending on your mood):
- random three-letter combination that is pronounceable, and not actually used by any common UNIX command. The fact that it is a mispronunciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the dictionary of slang.
- "global information tracker": you're in a good mood, and it actually works for you. Angels sing, and a light suddenly fills the room.
- "goddamn idiotic truckload of sh*t": when it breaks