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841785bad1
This is a major rewrite of the description of 'crypt', 'getentropy', and 'getrandom'. A few highlights of the content changes: - Throughout the manual, public headers, and user-visible messages, I replaced the term "password" with "passphrase", the term "password database" with "user database", and the term "encrypt(ion)" with "(one-way) hashing" whenever it was applied to passphrases. I didn't bother making this change in internal code or tests. The use of the term "password" in ruserpass.c survives, because that refers to a keyword in netrc files, but it is adjusted to make this clearer. There is a note in crypt.texi explaining that they were traditionally called passwords but single words are not good enough anymore, and a note in users.texi explaining that actual passphrase hashes are found in a "shadow" database nowadays. - There is a new short introduction to the "Cryptographic Functions" section, explaining how we do not intend to be a general-purpose cryptography library, and cautioning that there _are_, or have been, legal restrictions on the use of cryptography in many countries, without getting into any kind of detail that we can't promise to keep up to date. - I added more detail about what a "one-way function" is, and why they are used to obscure passphrases for storage. I removed the paragraph saying that systems not connected to a network need no user authentication, because that's a pretty rare situation nowadays. (It still says "sometimes it is necessary" to authenticate the user, though.) - I added documentation for all of the hash functions that glibc actually supports, but not for the additional hash functions supported by libxcrypt. If we're going to keep this manual section around after the transition is more advanced, it would probably make sense to add them then. - There is much more detailed discussion of how to generate a salt, and the failure behavior for crypt is documented. (Returning an invalid hash on failure is what libxcrypt does; Solar Designer's notes say that this was done "for compatibility with old programs that assume crypt can never fail".) - As far as I can tell, the header 'crypt.h' is entirely a GNU invention, and never existed on any other Unix lineage. The function 'crypt', however, was in Issue 1 of the SVID and is now in the XSI component of POSIX. I tried to make all of the @standards annotations consistent with this, but I'm not sure I got them perfectly right. - The genpass.c example has been improved to use getentropy instead of the current time to generate the salt, and to use a SHA-256 hash instead of MD5. It uses more random bytes than is strictly necessary because I didn't want to complicate the code with proper base64 encoding. - The testpass.c example has three hardwired hashes now, to demonstrate that different one-way functions produce different hashes for the same input. It also demonstrates how DES hashing only pays attention to the first eight characters of the input. - There is new text explaining in more detail how a CSPRNG differs from a regular random number generator, and how getentropy/getrandom are not exactly a CSPRNG. I tried not to make specific falsifiable claims here. I also tried to make the blocking/cancellation/error behavior of both getentropy and getrandom clearer. |
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| argp | ||
| assert | ||
| benchtests | ||
| bits | ||
| catgets | ||
| ChangeLog.old | ||
| conform | ||
| crypt | ||
| csu | ||
| ctype | ||
| debug | ||
| dirent | ||
| dlfcn | ||
| elf | ||
| gmon | ||
| gnulib | ||
| grp | ||
| gshadow | ||
| hesiod | ||
| htl | ||
| hurd | ||
| iconv | ||
| iconvdata | ||
| include | ||
| inet | ||
| intl | ||
| io | ||
| libio | ||
| locale | ||
| localedata | ||
| login | ||
| mach | ||
| malloc | ||
| manual | ||
| math | ||
| mathvec | ||
| misc | ||
| nis | ||
| nptl | ||
| nptl_db | ||
| nscd | ||
| nss | ||
| po | ||
| posix | ||
| pwd | ||
| resolv | ||
| resource | ||
| rt | ||
| scripts | ||
| setjmp | ||
| shadow | ||
| signal | ||
| socket | ||
| soft-fp | ||
| stdio-common | ||
| stdlib | ||
| streams | ||
| string | ||
| sunrpc | ||
| support | ||
| sysdeps | ||
| sysvipc | ||
| termios | ||
| time | ||
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| wcsmbs | ||
| wctype | ||
| .gitattributes | ||
| .gitignore | ||
| abi-tags | ||
| aclocal.m4 | ||
| ChangeLog | ||
| config.h.in | ||
| config.make.in | ||
| configure | ||
| configure.ac | ||
| COPYING | ||
| COPYING.LIB | ||
| extra-lib.mk | ||
| gen-locales.mk | ||
| INSTALL | ||
| libc-abis | ||
| libof-iterator.mk | ||
| LICENSES | ||
| MAINTAINERS | ||
| Makeconfig | ||
| Makefile | ||
| Makefile.in | ||
| Makerules | ||
| NEWS | ||
| o-iterator.mk | ||
| README | ||
| Rules | ||
| shlib-versions | ||
| test-skeleton.c | ||
| version.h | ||
This directory contains the sources of the GNU C Library. See the file "version.h" for what release version you have. The GNU C Library is the standard system C library for all GNU systems, and is an important part of what makes up a GNU system. It provides the system API for all programs written in C and C-compatible languages such as C++ and Objective C; the runtime facilities of other programming languages use the C library to access the underlying operating system. In GNU/Linux systems, the C library works with the Linux kernel to implement the operating system behavior seen by user applications. In GNU/Hurd systems, it works with a microkernel and Hurd servers. The GNU C Library implements much of the POSIX.1 functionality in the GNU/Hurd system, using configurations i[4567]86-*-gnu. When working with Linux kernels, this version of the GNU C Library requires Linux kernel version 3.2 or later. Also note that the shared version of the libgcc_s library must be installed for the pthread library to work correctly. The GNU C Library supports these configurations for using Linux kernels: aarch64*-*-linux-gnu alpha*-*-linux-gnu arm-*-linux-gnueabi hppa-*-linux-gnu i[4567]86-*-linux-gnu x86_64-*-linux-gnu Can build either x86_64 or x32 ia64-*-linux-gnu m68k-*-linux-gnu microblaze*-*-linux-gnu mips-*-linux-gnu mips64-*-linux-gnu powerpc-*-linux-gnu Hardware or software floating point, BE only. powerpc64*-*-linux-gnu Big-endian and little-endian. s390-*-linux-gnu s390x-*-linux-gnu riscv64-*-linux-gnu sh[34]-*-linux-gnu sparc*-*-linux-gnu sparc64*-*-linux-gnu If you are interested in doing a port, please contact the glibc maintainers; see http://www.gnu.org/software/libc/ for more information. See the file INSTALL to find out how to configure, build, and install the GNU C Library. You might also consider reading the WWW pages for the C library at http://www.gnu.org/software/libc/. The GNU C Library is (almost) completely documented by the Texinfo manual found in the `manual/' subdirectory. The manual is still being updated and contains some known errors and omissions; we regret that we do not have the resources to work on the manual as much as we would like. For corrections to the manual, please file a bug in the `manual' component, following the bug-reporting instructions below. Please be sure to check the manual in the current development sources to see if your problem has already been corrected. Please see http://www.gnu.org/software/libc/bugs.html for bug reporting information. We are now using the Bugzilla system to track all bug reports. This web page gives detailed information on how to report bugs properly. The GNU C Library is free software. See the file COPYING.LIB for copying conditions, and LICENSES for notices about a few contributions that require these additional notices to be distributed. License copyright years may be listed using range notation, e.g., 1996-2015, indicating that every year in the range, inclusive, is a copyrightable year that would otherwise be listed individually.