NAME
readpassphrase - get a passphrase from the user
LIBRARY
Utility functions from BSD systems (libbsd, -lbsd)
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.
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.