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diff --git a/man3/crypt.3 b/man3/crypt.3 deleted file mode 100644 index d3531f0..0000000 --- a/man3/crypt.3 +++ /dev/null @@ -1,319 +0,0 @@ -'\" t -.\" Michael Haardt (michael@cantor.informatik.rwth.aachen.de) -.\" Sat Sep 3 22:00:30 MET DST 1994 -.\" -.\" SPDX-License-Identifier: GPL-2.0-or-later -.\" -.\" Sun Feb 19 21:32:25 1995, faith@cs.unc.edu edited details away -.\" -.\" TO DO: This manual page should go more into detail how DES is perturbed, -.\" which string will be encrypted, and what determines the repetition factor. -.\" Is a simple repetition using ECB used, or something more advanced? I hope -.\" the presented explanations are at least better than nothing, but by no -.\" means enough. -.\" -.\" added _XOPEN_SOURCE, aeb, 970705 -.\" added GNU MD5 stuff, aeb, 011223 -.\" -.TH crypt 3 2023-10-31 "Linux man-pages 6.7" -.SH NAME -crypt, crypt_r \- password hashing -.SH LIBRARY -Password hashing library -.RI ( libcrypt ", " \-lcrypt ) -.SH SYNOPSIS -.nf -.B #include <unistd.h> -.P -.BI "char *crypt(const char *" key ", const char *" salt ); -.P -.B #include <crypt.h> -.P -.BI "char *crypt_r(const char *" key ", const char *" salt , -.BI " struct crypt_data *restrict " data ); -.fi -.P -.RS -4 -Feature Test Macro Requirements for glibc (see -.BR feature_test_macros (7)): -.RE -.P -.BR crypt (): -.nf - Since glibc 2.28: - _DEFAULT_SOURCE - glibc 2.27 and earlier: - _XOPEN_SOURCE -.fi -.P -.BR crypt_r (): -.nf - _GNU_SOURCE -.fi -.SH DESCRIPTION -.BR crypt () -is the password hashing function. -It is based on the Data Encryption -Standard algorithm with variations intended (among other things) to -discourage use of hardware implementations of a key search. -.P -.I key -is a user's typed password. -.P -.I salt -is a two-character string chosen from the set -[\fBa\-zA\-Z0\-9./\fP]. -This string is used to -perturb the algorithm in one of 4096 different ways. -.P -By taking the lowest 7 bits of each of the first eight characters of the -.IR key , -a 56-bit key is obtained. -This 56-bit key is used to encrypt repeatedly a -constant string (usually a string consisting of all zeros). -The returned -value points to the hashed password, a series of 13 printable ASCII -characters (the first two characters represent the salt itself). -The return value points to static data whose content is -overwritten by each call. -.P -Warning: the key space consists of -.if t 2\s-2\u56\s0\d -.if n 2**56 -equal 7.2e16 possible values. -Exhaustive searches of this key space are -possible using massively parallel computers. -Software, such as -.BR crack (1), -is available which will search the portion of this key space that is -generally used by humans for passwords. -Hence, password selection should, -at minimum, avoid common words and names. -The use of a -.BR passwd (1) -program that checks for crackable passwords during the selection process is -recommended. -.P -The DES algorithm itself has a few quirks which make the use of the -.BR crypt () -interface a very poor choice for anything other than password -authentication. -If you are planning on using the -.BR crypt () -interface for a cryptography project, don't do it: get a good book on -encryption and one of the widely available DES libraries. -.P -.BR crypt_r () -is a reentrant version of -.BR crypt (). -The structure pointed to by -.I data -is used to store result data and bookkeeping information. -Other than allocating it, -the only thing that the caller should do with this structure is to set -.I data\->initialized -to zero before the first call to -.BR crypt_r (). -.SH RETURN VALUE -On success, a pointer to the hashed password is returned. -On error, NULL is returned. -.SH ERRORS -.TP -.B EINVAL -.I salt -has the wrong format. -.TP -.B ENOSYS -The -.BR crypt () -function was not implemented, probably because of U.S.A. export restrictions. -.\" This level of detail is not necessary in this man page. . . -.\" .P -.\" When encrypting a plain text P using DES with the key K results in the -.\" encrypted text C, then the complementary plain text P' being encrypted -.\" using the complementary key K' will result in the complementary encrypted -.\" text C'. -.\" .P -.\" Weak keys are keys which stay invariant under the DES key transformation. -.\" The four known weak keys 0101010101010101, fefefefefefefefe, -.\" 1f1f1f1f0e0e0e0e and e0e0e0e0f1f1f1f1 must be avoided. -.\" .P -.\" There are six known half weak key pairs, which keys lead to the same -.\" encrypted data. Keys which are part of such key clusters should be -.\" avoided. -.\" Sorry, I could not find out what they are. -.\"" -.\" .P -.\" Heavily redundant data causes trouble with DES encryption, when used in the -.\" .I codebook -.\" mode that -.\" .BR crypt () -.\" implements. The -.\" .BR crypt () -.\" interface should be used only for its intended purpose of password -.\" verification, and should not be used as part of a data encryption tool. -.\" .P -.\" The first and last three output bits of the fourth S-box can be -.\" represented as function of their input bits. Empiric studies have -.\" shown that S-boxes partially compute the same output for similar input. -.\" It is suspected that this may contain a back door which could allow the -.\" NSA to decrypt DES encrypted data. -.\" .P -.\" Making encrypted data computed using crypt() publicly available has -.\" to be considered insecure for the given reasons. -.TP -.B EPERM -.I /proc/sys/crypto/fips_enabled -has a nonzero value, -and an attempt was made to use a weak hashing type, such as DES. -.SH ATTRIBUTES -For an explanation of the terms used in this section, see -.BR attributes (7). -.TS -allbox; -lbx lb lb -l l l. -Interface Attribute Value -T{ -.na -.nh -.BR crypt () -T} Thread safety MT-Unsafe race:crypt -T{ -.na -.nh -.BR crypt_r () -T} Thread safety MT-Safe -.TE -.SH STANDARDS -.TP -.BR crypt () -POSIX.1-2008. -.TP -.BR crypt_r () -GNU. -.SH HISTORY -.TP -.BR crypt () -POSIX.1-2001, SVr4, 4.3BSD. -.SS Availability in glibc -The -.BR crypt (), -.BR encrypt (3), -and -.BR setkey (3) -functions are part of the POSIX.1-2008 XSI Options Group for Encryption -and are optional. -If the interfaces are not available, then the symbolic constant -.B _XOPEN_CRYPT -is either not defined, -or it is defined to \-1 and availability can be checked at run time with -.BR sysconf (3). -This may be the case if the downstream distribution has switched from glibc -crypt to -.IR libxcrypt . -When recompiling applications in such distributions, -the programmer must detect if -.B _XOPEN_CRYPT -is not available and include -.I <crypt.h> -for the function prototypes; -otherwise -.I libxcrypt -is an ABI-compatible drop-in replacement. -.SH NOTES -.SS Features in glibc -The glibc version of this function supports additional -hashing algorithms. -.P -If -.I salt -is a character string starting with the characters "$\fIid\fP$" -followed by a string optionally terminated by "$", -then the result has the form: -.RS -.P -$\fIid\fP$\fIsalt\fP$\fIhashed\fP -.RE -.P -.I id -identifies the hashing method used instead of DES and this -then determines how the rest of the password string is interpreted. -The following values of -.I id -are supported: -.RS -.TS -lb lb -l lx. -ID Method -_ -1 MD5 -2a T{ -Blowfish (not in mainline glibc; added in some -Linux distributions) -T} -.\" openSUSE has Blowfish, but AFAICS, this option is not supported -.\" natively by glibc -- mtk, Jul 08 -.\" -.\" md5 | Sun MD5 -.\" glibc doesn't appear to natively support Sun MD5; I don't know -.\" if any distros add the support. -5 SHA-256 (since glibc 2.7) -6 SHA-512 (since glibc 2.7) -.TE -.RE -.P -Thus, $5$\fIsalt\fP$\fIhashed\fP and $6$\fIsalt\fP$\fIhashed\fP -contain the password hashed with, respectively, functions -based on SHA-256 and SHA-512. -.P -"\fIsalt\fP" stands for the up to 16 characters -following "$\fIid\fP$" in the salt. -The "\fIhashed\fP" -part of the password string is the actual computed password. -The size of this string is fixed: -.RS -.TS -lb l. -MD5 22 characters -SHA-256 43 characters -SHA-512 86 characters -.TE -.RE -.P -The characters in "\fIsalt\fP" and "\fIhashed\fP" are drawn from the set -[\fBa\-zA\-Z0\-9./\fP]. -In the MD5 and SHA implementations the entire -.I key -is significant (instead of only the first -8 bytes in DES). -.P -Since glibc 2.7, -.\" glibc commit 9425cb9eea6a62fc21d99aafe8a60f752b934b05 -the SHA-256 and SHA-512 implementations support a user-supplied number of -hashing rounds, defaulting to 5000. -If the "$\fIid\fP$" characters in the salt are -followed by "rounds=\fIxxx\fP$", where \fIxxx\fP is an integer, then the -result has the form -.RS -.P -$\fIid\fP$\fIrounds=yyy\fP$\fIsalt\fP$\fIhashed\fP -.RE -.P -where \fIyyy\fP is the number of hashing rounds actually used. -The number of rounds actually used is 1000 if -.I xxx -is less than -1000, 999999999 if -.I xxx -is greater than 999999999, and -is equal to -.I xxx -otherwise. -.SH SEE ALSO -.BR login (1), -.BR passwd (1), -.BR encrypt (3), -.BR getpass (3), -.BR passwd (5) |