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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 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

     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.

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 control-ling controlling
                        ling 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.

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));

SIGNALS
     The readpassphrase() function will catch the following signals:

     SIGINT
     SIGHUP
     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.

FILES
     /dev/tty

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.

BSD                            December 7, 2001                            BSD