MirBSD manpage: readpassphrase(3)

READPASSPHRASE(3)          BSD Programmer's 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.

     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 ig-
                   noring 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 re-
     stored if it had previously been turned off. If a signal handler was in-
     stalled 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, read-
     passphrase() 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.

MirBSD #10-current              June 28, 2002                                1