get a passphrase from the user
() function displays a prompt to,
and reads in a passphrase from, /dev/tty
. If this
file is inaccessible and the
flag is not set,
() 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
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
into the buffer
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");
- The readpassphrase() function
was interrupted by a signal.
- The bufsiz argument was
- The process is a member of a background process attempting
to read from its controlling terminal, the process is ignoring or blocking
SIGTTIN signal, or the process
group is orphaned.
- The process has already reached its limit for open file
- The system file table is full.
- There is no controlling terminal and the
RPP_REQUIRE_TTY flag was
() 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
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,
() will reprint the prompt and the
user may then enter a passphrase.
() function is an
extension and should not be used if
portability is desired.
() function first appeared in