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

NAME
     readpassphrase -- get a passphrase from the user

SYNOPSIS
     #include <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 pro-
     vided buffer buf.  Any additional characters and the terminating newline
     (or return) character are discarded.

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

HISTORY
     The readpassphrase() function first appeared in OpenBSD 2.9.  RPP_STDIN
     was introduced in OS X 10.12.

BSD                              May 31, 2007                              BSD