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READPASSPHRASE(3)     DragonFly Library Functions Manual     READPASSPHRASE(3)


NAME

     readpassphrase -- get a passphrase from the user


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <sys/types.h>
     #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
     provided 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
     null-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 signal 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.

DragonFly 4.5                   August 21, 2016                  DragonFly 4.5

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