READPASSPHRASE(3) | Library Functions Manual | READPASSPHRASE(3)

# 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.

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.

# 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");

    ...

    explicit_bzero(passbuf, 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.

January 25, 2019 | Debian