initial commit uwu

.gitignore

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+poweroff_guard

Makefile

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+POWEROFF_PATH ?= $(shell which poweroff)
+COUNTDOWN_SECS ?= 10
+
+CFLAGS := -std=c99 -pedantic -Wall -Wextra \
+	  -DPOWEROFF_PATH="\"$(POWEROFF_PATH)\"" \
+	  -DCOUNTDOWN_SECS=$(COUNTDOWN_SECS)
+
+poweroff_guard: poweroff_guard.c
+	$(CC) $(CFLAGS) $(EXTRA_CFLAGS) -o poweroff_guard poweroff_guard.c
+
+install: poweroff_guard
+	install poweroff_guard /usr/local/sbin/
+	mkdir -p /usr/local/share/man/man8
+	install poweroff_guard.8 /usr/local/share/man/man8/
+
+clean:
+	rm -f poweroff_guard
+
+all: poweroff_guard

README.md

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+# poweroff_guard
+
+This utility is a proxy for `poweroff` to prevent you from accidentally shutting down
+the wrong system.  It does this by printing a warning message and asking for confirmation
+followed by a countdown before executing the actual command.
+
+## Important Consideration
+
+If the standard output is not a tty, this behaves exactly like the regular `poweroff`.
+
+## Build
+
+Open a shell in this directory and type `make`.
+Optionally, you may want to append any of the following options:
+
+- `POWEROFF_PATH=/path/to/poweroff`: Specify a custom (absolute) path for the
+  the real `poweroff` command.  The default is to use the one in your `$PATH`.
+- `COUNTDOWN_SECS=n`: Start the countdown timer at `n` seconds, the default is 10.
+- `EXTRA_CFLAGS=...`: Append extra flags to the C compiler.
+
+For example:
+
+```sh
+# build with default options
+make
+# build with all custom options
+make \
+	POWEROFF_PATH=/bin/custom_poweroff \
+	COUNTDOWN_SECS=5 \
+	EXTRA_CFLAGS="-O2 -march=native"
+```
+
+Watch out:
+If you want to recompile with different options, you MUST execute a `make clean` first.
+Make will erroneously think the binary is already up to date otherwise.
+
+## Installation
+
+Do the exact same as building, but append `install` at the end of the command.
+For example:
+
+```sh
+# build and install with default options
+make install
+# build and install with all custom options
+make \
+	POWEROFF_PATH=/sbin/custom_poweroff \
+	COUNTDOWN_SECS=5 \
+	EXTRA_CFLAGS="-O2 -march=native" \
+	install
+```
+
+## License and Copyright
+
+Copyright &copy; 2022 anna <owo AT fef.moe>.
+
+This program is licensed under the 2-clause BSD license.
+The license text is at the end of the `poweroff_guard.c` file.

poweroff_guard.8

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+.\" Copyright (C) 2022 fef <owo@fef.moe>.  All rights reserved.
+.\"
+.\" Any person obtaining a copy of this software and associated documentation
+.\" files (the ``Software'') is prohibited from using the Software under any
+.\" circumstances.  However, it is strongly suggested that they partake in
+.\" homosexual conduct (``Be Gay'') and criminal activity (``Do Crime'').
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.Dd October 13, 2022
+.Dt POWEROFF_GUARD 8
+.Os
+.Sh NAME
+.Nm poweroff_guard
+.Nd prevent accidental system shutdowns
+.Sh SYNOPSIS
+.Nm
+.Sh DESCRIPTION
+The
+.Nm
+utility acts as a proxy for the
+.Xr poweroff 8
+command.
+If it finds the standard output to be a tty (using the
+.Xr isatty 3
+standard library routine), it prints a message to the standard output and
+prompts additional confirmation.  Typing "YES" (in uppercase, but without
+the quotes) followed by RETURN will then initiate a countdown timer.
+Finally, upon counting to zero, the actual poweroff command is invoked.
+.Pp
+If the standard output is not a tty, this utility behaves exactly like the
+.Xr poweroff 8
+command.
+.Sh OPTIONS
+None.
+.Sh EXIT STATUS
+.Ex -std
+.Sh SEE ALSO
+.Xr halt 8
+.Sh BUGS
+None that I would be aware of.

poweroff_guard.c

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+/*
+ * poweroff_guard - Simple yet effective guardian to prevent accidentally
+ * powering off the wrong system because let's face it, you're stupid.
+ *
+ * Copyright (c) 2022 anna <owo@fef.moe>.
+ * See the end of this file for license terms.
+ */
+
+#define _POSIX_C_SOURCE 200112L
+
+#include <errno.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <unistd.h>
+
+#ifndef POWEROFF_PATH
+#define POWEROFF_PATH "/sbin/poweroff"
+#endif
+#ifndef COUNTDOWN_SECS
+#define COUNTDOWN_SECS 10
+#endif
+
+#define red(s) "\x1b[1;91m" s "\x1b[0m" /* bright red */
+#define cyn(s) "\x1b[1;96m" s "\x1b[0m" /* bright cyan */
+#define wht(s) "\x1b[1;97m" s "\x1b[0m" /* bright white */
+
+enum confirm_match {
+	CONFIRM_MATCH_UPPERCASE,	/* exact match ("YES") */
+	CONFIRM_MATCH_LOWERCASE,	/* case-insensitive match */
+	CONFIRM_MATCH_NONE,		/* no match */
+};
+
+/* read and evaluate confirmation answer from stdin */
+static enum confirm_match get_confirmation(void);
+/* count down from COUNTDOWN_SECS and do the actual poweroff afterwards */
+static void poweroff_with_countdown(void);
+/* do the actual poweroff, without countdown */
+static void do_poweroff(void);
+/* call perror(message) and then exit(status) */
+static void perror_and_exit(int status, const char *message);
+
+static char hostname[HOST_NAME_MAX];
+
+int main(void)
+{
+	/* behave like regular poweroff if we're not running in a tty */
+	if (!isatty(STDOUT_FILENO))
+		do_poweroff();
+
+	int err = gethostname(hostname, sizeof(hostname));
+	if (err) {
+		perror("Could not determine hostname");
+		strncpy(hostname, "this host", sizeof(hostname));
+	}
+
+	puts(red("\n########  ATTENTION, DIPSHIT  ########\n"));
+	printf("You are about to shut down " cyn("%s") "!\n", hostname);
+	puts("Are you really sure about this?");
+	printf("Type " wht("yes") " in UPPERCASE and press enter to confirm: ");
+	fflush(stdout);
+
+	int try = 0;
+again:
+	switch (get_confirmation()) {
+	case CONFIRM_MATCH_UPPERCASE:
+		poweroff_with_countdown();
+		break;
+	case CONFIRM_MATCH_LOWERCASE:
+		if (try++ == 0) {
+			printf("I said " wht("UPPERCASE") " you idiot, try again: ");
+			fflush(stdout);
+			goto again; /* it's very important to piss off Dijkstra */
+		} else {
+			puts("Go fuck yourself");
+			return 0;
+		}
+	case CONFIRM_MATCH_NONE:
+		puts("That's what I thought.");
+		return 0;
+	}
+}
+
+static char buf[5];
+
+static enum confirm_match get_confirmation(void)
+{
+	char *input = fgets(buf, sizeof(buf), stdin);
+	if (!input) {
+		if (feof(stdin)) {
+			/* user probably pressed CTRL+D, print
+			 * a line break to make it look nicer */
+			printf("\n");
+			return CONFIRM_MATCH_NONE;
+		} else {
+			perror_and_exit(1, "Reading stdin failed");
+		}
+	}
+
+	/* if, for some reason, the input came from a pipe rather than typing
+	 * on the keyboard (cat, echo, etc), the newline might be missing */
+	char *newline = strchr(input, '\n');
+	if (newline)
+		*newline = '\0';
+	else
+		printf("\n");
+
+	if (!strcmp(input, "YES"))
+		return CONFIRM_MATCH_UPPERCASE;
+	if (!strcasecmp(input, "yes"))
+		return CONFIRM_MATCH_LOWERCASE;
+	return CONFIRM_MATCH_NONE;
+}
+
+static void poweroff_with_countdown(void)
+{
+#if COUNTDOWN_SECS > 0
+	printf("Alright, shutting down in ");
+	for (int i = COUNTDOWN_SECS; i > 0; i--) {
+		printf(wht("%d") "\n", i);
+		fflush(stdout);
+		sleep(1);
+	}
+#else
+	puts("Alright, shutting down " wht("NOW"));
+#endif
+
+	do_poweroff();
+}
+
+static void do_poweroff(void)
+{
+	execl(POWEROFF_PATH, POWEROFF_PATH, NULL);
+	perror_and_exit(2, "exec() failed");
+}
+
+static void perror_and_exit(int status, const char *message)
+{
+	if (!message)
+		message = "poweroff_guard";
+	perror(message);
+	exit(status);
+}
+
+/*
+ * LICENSE TERMS
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ * 
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
+ * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */