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182 lines
4.8 KiB
Groff
182 lines
4.8 KiB
Groff
.\" $OpenBSD: readpassphrase.3,v 1.17 2007/05/31 19:19:28 jmc Exp $
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.\"
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.\" Copyright (c) 2000, 2002 Todd C. Miller <Todd.Miller@courtesan.com>
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.\"
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.\" Permission to use, copy, modify, and distribute this software for any
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.\" purpose with or without fee is hereby granted, provided that the above
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.\" copyright notice and this permission notice appear in all copies.
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.\"
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.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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.\"
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.\" Sponsored in part by the Defense Advanced Research Projects
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.\" Agency (DARPA) and Air Force Research Laboratory, Air Force
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.\" Materiel Command, USAF, under agreement number F39502-99-1-0512.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd May 31, 2007
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.Dt READPASSPHRASE 3
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.Os
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.Sh NAME
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.Nm readpassphrase
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.Nd get a passphrase from the user
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.Sh SYNOPSIS
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.In readpassphrase.h
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.Ft "char *"
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.Fn readpassphrase "const char *prompt" "char *buf" "size_t bufsiz" "int flags"
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.Sh DESCRIPTION
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The
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.Fn readpassphrase
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function displays a prompt to, and reads in a passphrase from,
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.Pa /dev/tty .
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If this file is inaccessible
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and the
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.Dv RPP_REQUIRE_TTY
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flag is not set,
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.Fn readpassphrase
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displays the prompt on the standard error output and reads from the standard
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input.
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In this case it is generally not possible to turn off echo.
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.Pp
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Up to
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.Fa bufsiz
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\- 1 characters (one is for the
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.Dv NUL )
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are read into the provided buffer
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.Fa buf .
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Any additional
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characters and the terminating newline (or return) character are discarded.
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.Pp
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The
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.Fn readpassphrase
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function
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takes the following optional
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.Fa flags :
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.Pp
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.Bl -tag -width ".Dv RPP_REQUIRE_TTY" -compact
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.It Dv RPP_ECHO_OFF
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turn off echo (default behavior)
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.It Dv RPP_ECHO_ON
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leave echo on
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.It Dv RPP_REQUIRE_TTY
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fail if there is no tty
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.It Dv RPP_FORCELOWER
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force input to lower case
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.It Dv RPP_FORCEUPPER
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force input to upper case
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.It Dv RPP_SEVENBIT
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strip the high bit from input
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.It Dv RPP_STDIN
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force read of passphrase from stdin
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.El
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.Pp
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The calling process should zero the passphrase as soon as possible to
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avoid leaving the cleartext passphrase visible in the process's address
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space.
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.Sh RETURN VALUES
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Upon successful completion,
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.Fn readpassphrase
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returns a pointer to the NUL-terminated passphrase.
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If an error is encountered, the terminal state is restored and
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a
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.Dv NULL
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pointer is returned.
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.Sh FILES
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.Bl -tag -width ".Pa /dev/tty" -compact
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.It Pa /dev/tty
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.El
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.Sh EXAMPLES
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The following code fragment will read a passphrase from
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.Pa /dev/tty
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into the buffer
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.Fa passbuf .
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.Bd -literal -offset indent
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char passbuf[1024];
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\&...
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if (readpassphrase("Response: ", passbuf, sizeof(passbuf),
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RPP_REQUIRE_TTY) == NULL)
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errx(1, "unable to read passphrase");
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if (compare(transform(passbuf), epass) != 0)
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errx(1, "bad passphrase");
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\&...
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memset(passbuf, 0, sizeof(passbuf));
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.Ed
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er EINTR
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The
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.Fn readpassphrase
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function was interrupted by a signal.
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.It Bq Er EINVAL
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The
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.Ar bufsiz
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argument was zero.
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.It Bq Er EIO
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The process is a member of a background process attempting to read
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from its controlling terminal, the process is ignoring or blocking
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the
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.Dv SIGTTIN
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signal, or the process group is orphaned.
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.It Bq Er EMFILE
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The process has already reached its limit for open file descriptors.
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.It Bq Er ENFILE
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The system file table is full.
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.It Bq Er ENOTTY
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There is no controlling terminal and the
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.Dv RPP_REQUIRE_TTY
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flag was specified.
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.El
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.Sh SIGNALS
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The
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.Fn readpassphrase
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function
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will catch the following signals:
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.Bd -literal -offset indent
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SIGALRM SIGHUP SIGINT
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SIGPIPE SIGQUIT SIGTERM
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SIGTSTP SIGTTIN SIGTTOU
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.Ed
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.Pp
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When one of the above signals is intercepted, terminal echo will
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be restored if it had previously been turned off.
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If a signal handler was installed for the signal when
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.Fn readpassphrase
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was called, that handler is then executed.
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If no handler was previously installed for the signal then the
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default action is taken as per
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.Xr sigaction 2 .
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.Pp
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The
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.Dv SIGTSTP , SIGTTIN
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and
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.Dv SIGTTOU
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signals (stop signals generated from keyboard or due to terminal I/O
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from a background process) are treated specially.
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When the process is resumed after it has been stopped,
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.Fn readpassphrase
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will reprint the prompt and the user may then enter a passphrase.
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.Sh SEE ALSO
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.Xr sigaction 2 ,
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.Xr getpass 3
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.Sh STANDARDS
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The
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.Fn readpassphrase
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function is an
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extension and should not be used if portability is desired.
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.Sh HISTORY
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The
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.Fn readpassphrase
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function first appeared in
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.Ox 2.9 .
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