get a passphrase from the
char *prompt, char
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 flags argument is the bitwise OR of zero or more of the following values:
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 read passphrase from stdin; ignore prompt
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; ... 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"); ... explicit_bzero(passbuf, sizeof(passbuf));
readpassphrase() function was interrupted by a signal.
- The bufsiz argument was zero.
- The process is a member of a background process attempting to read from
its controlling terminal, the process is ignoring or blocking the
SIGTTINsignal, or the process group is orphaned.
- The process has already reached its limit for open file descriptors.
- The system file table is full.
- There is no controlling terminal and the
RPP_REQUIRE_TTYflag was specified.
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
was called, that handler is then executed. If no handler was previously
installed for the signal then the default action is taken as per
(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,
will reprint the prompt and the user may then enter a passphrase.
readpassphrase() function is an
OpenBSD extension and should not be used if
portability is desired.
readpassphrase() function first
appeared in OpenBSD 2.9.