mirror of https://github.com/mkerrisk/man-pages
133 lines
3.8 KiB
Plaintext
133 lines
3.8 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "CRYPT" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" crypt
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.SH NAME
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crypt \- string encoding function (\fBCRYPT\fP)
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.SH SYNOPSIS
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.LP
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\fB#include <unistd.h>
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.br
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.sp
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char *crypt(const char *\fP\fIkey\fP\fB, const char *\fP\fIsalt\fP\fB);
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\fP
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\fB
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fIcrypt\fP() function is a string encoding function. The algorithm
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is implementation-defined.
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.LP
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The \fIkey\fP argument points to a string to be encoded. The \fIsalt\fP
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argument is a string chosen from the set:
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.sp
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.RS
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.nf
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\fBa b c d e f g h i j k l m n o p q r s t u v w x y z
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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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0 1 2 3 4 5 6 7 8 9 . /
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\fP
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.fi
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.RE
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.LP
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The first two characters of this string may be used to perturb the
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encoding algorithm.
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.LP
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The return value of \fIcrypt\fP() points to static data that is overwritten
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by each call.
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.LP
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The \fIcrypt\fP() function need not be reentrant. A function that
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is not required to be reentrant is not required to be
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thread-safe.
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.SH RETURN VALUE
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.LP
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Upon successful completion, \fIcrypt\fP() shall return a pointer to
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the encoded string. The first two characters of the
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returned value shall be those of the \fIsalt\fP argument. Otherwise,
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it shall return a null pointer and set \fIerrno\fP to
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indicate the error.
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.SH ERRORS
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.LP
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The \fIcrypt\fP() function shall fail if:
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.TP 7
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.B ENOSYS
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The functionality is not supported on this implementation.
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.sp
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.SS Encoding Passwords
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.LP
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The following example finds a user database entry matching a particular
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user name and changes the current password to a new
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password. The \fIcrypt\fP() function generates an encoded version
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of each password. The first call to \fIcrypt\fP() produces an
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encoded version of the old password; that encoded password is then
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compared to the password stored in the user database. The second
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call to \fIcrypt\fP() encodes the new password before it is stored.
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.LP
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The \fIputpwent\fP() function, used in the following example, is not
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part of IEEE\ Std\ 1003.1-2001.
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.sp
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.RS
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.nf
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\fB#include <unistd.h>
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#include <pwd.h>
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#include <string.h>
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#include <stdio.h>
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\&...
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int valid_change;
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int pfd; /* Integer for file descriptor returned by open(). */
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FILE *fpfd; /* File pointer for use in putpwent(). */
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struct passwd *p;
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char user[100];
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char oldpasswd[100];
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char newpasswd[100];
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char savepasswd[100];
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\&...
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valid_change = 0;
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while ((p = getpwent()) != NULL) {
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/* Change entry if found. */
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if (strcmp(p->pw_name, user) == 0) {
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if (strcmp(p->pw_passwd, crypt(oldpasswd, p->pw_passwd)) == 0) {
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strcpy(savepasswd, crypt(newpasswd, user));
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p->pw_passwd = savepasswd;
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valid_change = 1;
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}
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else {
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fprintf(stderr, "Old password is not valid\\n");
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}
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}
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/* Put passwd entry into ptmp. */
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putpwent(p, fpfd);
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}
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\fP
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.fi
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.RE
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.SH APPLICATION USAGE
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.LP
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The values returned by this function need not be portable among XSI-conformant
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systems.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIencrypt\fP() , \fIsetkey\fP() , the Base Definitions volume of
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IEEE\ Std\ 1003.1-2001, \fI<unistd.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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