readpassphrase (3)
Leading comments
$OpenBSD: readpassphrase.3,v 1.16 2005/07/22 03:16:58 jaredy Exp $ Copyright (c) 2000, 2002 Todd C. Miller <Todd.Miller@courtesan.com> Permission to use, copy, modify, and distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies. THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHA...
NAME
readpassphrase - get a passphrase from the userLIBRARY
Lb libbsdSYNOPSIS
In readpassphrase.h (See libbsd(7) for include usage.) Ft char * Fn readpassphrase const char *prompt char *buf size_t bufsiz int flagsDESCRIPTION
The Fn 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, Fn 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 Fa bufsiz - 1 characters (one is for the NUL) are read into the provided buffer Fa buf . Any additional characters and the terminating newline (or return) character are discarded.
Fn readpassphrase takes the following optional Fa 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, Fn 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 Fa 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
- Bq Er EINTR
- The Fn readpassphrase function was interrupted by a signal.
- Bq Er EINVAL
- The bufsiz argument was zero.
- Bq Er 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.
- Bq Er EMFILE
- The process has already reached its limit for open file descriptors.
- Bq Er ENFILE
- The system file table is full.
- Bq Er ENOTTY
- There is no controlling terminal and the RPP_REQUIRE_TTY flag was specified.
SIGNALS
Fn 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 Fn 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, Fn readpassphrase will reprint the prompt and the user may then enter a passphrase.