.\" $OpenBSD: readpassphrase.3,v 1.21 2019/01/25 00:19:25 millert Exp $ .\" .\" Copyright (c) 2000, 2002 Todd C. Miller <millert@openbsd.org> .\" .\" Permission to use, copy, modify, and distribute this software for any .\" purpose with or without fee is hereby granted, provided that the above .\" copyright notice and this permission notice appear in all copies. .\" .\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR .\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. .\" .\" Sponsored in part by the Defense Advanced Research Projects .\" Agency (DARPA) and Air Force Research Laboratory, Air Force .\" Materiel Command, USAF, under agreement number F39502-99-1-0512. .\" .Dd $Mdocdate: January 25 2019 $ .Dt READPASSPHRASE 3 .Os .Sh NAME .Nm readpassphrase .Nd get a passphrase from the user .Sh SYNOPSIS .In readpassphrase.h .Ft char * .Fn readpassphrase "const char *prompt" "char *buf" "size_t bufsiz" "int flags" .Sh DESCRIPTION The .Fn readpassphrase function displays a prompt to, and reads in a passphrase from, .Pa /dev/tty . If this file is inaccessible and the .Dv RPP_REQUIRE_TTY flag is not set, .Fn readpassphrase displays the prompt on the standard error output and reads from the standard input. In this case it is generally not possible to turn off echo. .Pp Up to .Fa bufsiz - 1 characters (one is for the NUL) are read into the provided buffer .Fa buf . Any additional characters and the terminating newline (or return) character are discarded. .Pp The .Fa flags argument is the bitwise .Tn OR of zero or more of the following values: .Bd -literal -offset indent RPP_ECHO_OFF turn off echo (default behavior) RPP_ECHO_ON leave echo on RPP_REQUIRE_TTY fail if there is no tty RPP_FORCELOWER force input to lower case RPP_FORCEUPPER force input to upper case RPP_SEVENBIT strip the high bit from input RPP_STDIN read passphrase from stdin; ignore prompt .Ed .Pp The calling process should zero the passphrase as soon as possible to avoid leaving the cleartext passphrase visible in the process's address space. .Sh RETURN VALUES Upon successful completion, .Fn readpassphrase returns a pointer to the NUL-terminated passphrase. If an error is encountered, the terminal state is restored and a null pointer is returned. .Sh FILES .Bl -tag -width /dev/tty -compact .It Pa /dev/tty .El .Sh EXAMPLES The following code fragment will read a passphrase from .Pa /dev/tty into the buffer .Fa passbuf . .Bd -literal -offset indent char passbuf[1024]; \&... if (readpassphrase("Response: ", passbuf, sizeof(passbuf), RPP_REQUIRE_TTY) == NULL) errx(1, "unable to read passphrase"); if (compare(transform(passbuf), epass) != 0) errx(1, "bad passphrase"); \&... explicit_bzero(passbuf, sizeof(passbuf)); .Ed .Sh ERRORS .Bl -tag -width Er .It Bq Er EINTR The .Fn readpassphrase function was interrupted by a signal. .It Bq Er EINVAL The .Ar bufsiz argument was zero. .It Bq Er EIO The process is a member of a background process attempting to read from its controlling terminal, the process is ignoring or blocking the .Dv SIGTTIN signal, or the process group is orphaned. .It Bq Er EMFILE The process has already reached its limit for open file descriptors. .It Bq Er ENFILE The system file table is full. .It Bq Er ENOTTY There is no controlling terminal and the .Dv RPP_REQUIRE_TTY flag was specified. .El .Sh SIGNALS .Fn readpassphrase will catch the following signals: .Bd -literal -offset indent SIGALRM SIGHUP SIGINT SIGPIPE SIGQUIT SIGTERM SIGTSTP SIGTTIN SIGTTOU .Ed .Pp When one of the above signals is intercepted, terminal echo will be restored if it had previously been turned off. If a signal handler was installed for the signal when .Fn readpassphrase was called, that handler is then executed. If no handler was previously installed for the signal then the default action is taken as per .Xr sigaction 2 . .Pp The .Dv SIGTSTP , .Dv SIGTTIN , and .Dv SIGTTOU signals (stop signals generated from keyboard or due to terminal I/O from a background process) are treated specially. When the process is resumed after it has been stopped, .Fn readpassphrase will reprint the prompt and the user may then enter a passphrase. .Sh SEE ALSO .Xr sigaction 2 , .Xr getpass 3 .Sh STANDARDS The .Fn readpassphrase function is an .Ox extension and should not be used if portability is desired. .Sh HISTORY The .Fn readpassphrase function first appeared in .Ox 2.9 .