47efda967c
The current way we generate random file names is by taking the seconds and microseconds, plus the PID, and mixing them together, then encoding them. If this fails, we increment the value by 7777, and try again up to TMP_MAX times. Unfortunately, this is not the best idea from a security perspective. If we're writing into TMPDIR, an attacker can guess these values easily and prevent us from creating any temporary files at all by creating them all first. Even though we set TMP_MAX to 16384, this may be achievable in some contexts, even if unlikely to occur in practice. Fortunately, we can simply solve this by using the system cryptographically secure pseudorandom number generator (CSPRNG) to generate a random 64-bit value, and use that as before. Note that there is still a small bias here, but because a six-character sequence chosen out of 62 characters provides about 36 bits of entropy, the bias here is less than 2^-28, which is acceptable, especially considering we'll retry several times. Note that the use of a CSPRNG in generating temporary file names is also used in many libcs. glibc recently changed from an approach similar to ours to using a CSPRNG, and FreeBSD and OpenBSD also use a CSPRNG in this case. Even if the likelihood of an attack is low, we should still be at least as responsible in creating temporary files as libc is. Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> 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.txt to get started, then see
Documentation/giteveryday.txt for a useful minimum set of commands, and
Documentation/git-<commandname>.txt 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.txt
(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). To subscribe to the list, send an email with just "subscribe git" in the body to majordomo@vger.kernel.org. The mailing list archives are available at https://lore.kernel.org/git/, http://marc.info/?l=git and other archival sites.
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