112 lines
2.9 KiB
Groff
112 lines
2.9 KiB
Groff
.\" Copyright (c) 2023-2024 DTB <trinity@trinity.moe>
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.\" Copyright (c) 2024 Emma Tebibyte <emma@tebibyte.media>
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.\"
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.\" This work is licensed under CC BY-SA 4.0. To see a copy of this license,
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.\" visit <http://creativecommons.org/licenses/by-sa/4.0/>.
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.\"
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.TH PEEK 1 2024-08-14 "Harakit X.X.X"
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.SH NAME
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peek \(en read from the standard input, furtively
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.\"
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.SH SYNOPSIS
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peek
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.RB [ -i ]
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.\"
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.SH DESCRIPTION
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Read input from the standard input with terminal echo disabled.
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.\"
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.SH OPTIONS
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.IP \fB-i\fP
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Allows input to come from sources other than terminals (pipes).
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.\"
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.SH DIAGNOSTICS
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In the event of an error, a debug message will be printed and the program will
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exit with the appropriate
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.BR sysexits.h (3)
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error code.
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In order to ensure the user\(cqs terminal is still usable after premature
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termination, the program attempts to handle the SIGINT signal; if it cannot,
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an error message is printed and execution continues. If the program is
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interrupted, it exits unsuccessfully without an error message.
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.\"
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.SH RATIONALE
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This tool was originally written to accept passwords in shell scripts as an
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extremely simple alternative to the GNU Privacy Guard project\(cqs
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.BR pinentry (1)
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utility.
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Accepting input without showing what is being typed is useful when keying in
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secrets in public settings or in places where surveillance cameras are
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installed.
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.\"
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.SH CAVEATS
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This program does nothing to prevent others from seeing the key presses input to
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a keyboard. It also does not protect against the sound of typing being analyzed
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to determine what was input without needing to see screen or keyboard.
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Accepting secrets in shell scripts is probably not advisable.
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On systems that support it, the
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.BR ioctl (2)
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command TIOCSTI can be used to insert characters into the standard input. This
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doesn't allow snooping but can be used for general mischief.
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.\"
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.SH EXAMPLES
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This is an
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.BR sh (1p)
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command line that hashes a given password. It uses
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.BR head (1p)
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to only accept one line of input,
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.BR xargs (1p)
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and
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.BR printf (1p)
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to strip the trailing newline,
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.BR htpasswd (1)
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from Apache\(cqs utilities to hash the input with the bcrypt algorithm, and
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.BR cut (1p)
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to print only the resulting hash:
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.RS
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$ peek | head -n 1 | xargs printf '%s' | htpasswd -nBi _ | cut -d : -f 2
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.RE
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This is an
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.BR sh (1p)
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command line that allows a user to write blindly into a text file but displaying
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only written lines. Some writers have the habit of prematurely revising their
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work and use tools with functionality similar to this to prevent it.
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It uses
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.BR mm (1)
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to pipe the output of the program to both the standard error and the regular
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file writing.txt:
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.RS
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$ echo Input ^D to quit. && peek | mm -eo - >writing.txt
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.RE
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.\"
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.SH AUTHOR
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Written by DTB
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.MT trinity@trinity.moe
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.ME .
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.\"
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.SH COPYRIGHT
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Copyright \(co 2023-2024 DTB. License AGPLv3+: GNU AGPL version 3 or later
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<https://gnu.org/licenses/gpl.html>.
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.\"
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.SH SEE ALSO
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.BR ioctl (2),
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.BR ioctl_tty (2),
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.BR read (1p),
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.BR sh (1p),
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.BR stty (1p)
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