READPASSPHRASE(3)					   BSD Library Functions Manual 					 READPASSPHRASE(3)

NAME

     readpassphrase -- get a passphrase from the user

LIBRARY

     Utility functions from BSD systems (libbsd, -lbsd)

SYNOPSIS

     #include <bsd/readpassphrase.h>

     char *
     readpassphrase(const char *prompt, char *buf, size_t bufsiz, int flags);

DESCRIPTION

     The readpassphrase() function displays a prompt to, and reads in a passphrase from, /dev/tty.  If this file is inaccessible and the
     RPP_REQUIRE_TTY flag is not set, 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.

     Up to bufsiz - 1 characters (one is for the NUL) are read into the provided buffer buf.  Any additional characters and the terminating new-
     line (or return) character are discarded.

     readpassphrase() takes the following optional flags:

	   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		   force read of passphrase from stdin

     The calling process should zero the passphrase as soon as possible to avoid leaving the cleartext passphrase visible in the process's address
     space.

RETURN VALUES

     Upon successful completion, 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.

FILES

     /dev/tty

EXAMPLES

     The following code fragment will read a passphrase from /dev/tty into the buffer passbuf.

	   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");

	   ...

	   memset(passbuf, 0, sizeof(passbuf));

ERRORS

     [EINTR]		The readpassphrase() function was interrupted by a signal.

     [EINVAL]		The bufsiz argument was zero.

     [EIO]		The process is a member of a background process attempting to read from its controlling terminal, the process is ignoring
			or blocking the SIGTTIN signal, or the process group is orphaned.

     [EMFILE]		The process has already reached its limit for open file descriptors.

     [ENFILE]		The system file table is full.

     [ENOTTY]		There is no controlling terminal and the RPP_REQUIRE_TTY flag was specified.

SIGNALS

     readpassphrase() will catch the following signals:

	   SIGALRM	   SIGHUP	   SIGINT
	   SIGPIPE	   SIGQUIT	   SIGTERM
	   SIGTSTP	   SIGTTIN	   SIGTTOU

     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 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 sigaction(2).

     The SIGTSTP, SIGTTIN, and 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, readpassphrase() will reprint the prompt and the user may then enter a
     passphrase.

SEE ALSO

     sigaction(2), getpass(3)

STANDARDS

     The readpassphrase() function is an OpenBSD extension and should not be used if portability is desired.

HISTORY

     The readpassphrase() function first appeared in OpenBSD 2.9.

BSD
								   May 31, 2007 							       BSD