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.
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
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.