READPASSPHRASE(3) | Library Functions Manual | READPASSPHRASE(3) |
readpassphrase
—
get a passphrase from the user
#include
<readpassphrase.h>
char *
readpassphrase
(const
char *prompt, char
*buf, size_t
bufsiz, int
flags);
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
RPP_ECHO_ON
RPP_REQUIRE_TTY
RPP_FORCELOWER
RPP_FORCEUPPER
RPP_SEVENBIT
RPP_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.
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.
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));
EINTR
]readpassphrase
() function was interrupted by a
signal.EINVAL
]EIO
]SIGTTIN
signal, or the process group is
orphaned.EMFILE
]ENFILE
]ENOTTY
]RPP_REQUIRE_TTY
flag was specified.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 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.
The readpassphrase
() function is an
extension and should not be used if portability is desired.
The readpassphrase
() function first
appeared in OpenBSD 2.9.
RPP_STDIN
was introduced in OS X 10.12.
May 31, 2007 | macOS 14.6 |