From 98a15fa859157fb6fd6540329a204f3cf0629d64 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=89rico=20Rolim?= <erico.erc@gmail.com>
Date: Sat, 25 Jul 2020 01:34:36 -0300
Subject: [PATCH] sourcecode: create enter-chroot.

Written in C, is a setid program and does the job of launch-chroot,
which is being retired.
---
 linux-utils/.local/bin/launch-chroot   |  14 ---
 sourcecode/.gitignore                  |   2 +
 sourcecode/enter-chroot/enter-chroot.c | 113 +++++++++++++++++++++++++
 sourcecode/enter-chroot/install.sh     |   8 ++
 sourcecode/sshfs-map/.gitignore        |   1 -
 5 files changed, 123 insertions(+), 15 deletions(-)
 delete mode 100755 linux-utils/.local/bin/launch-chroot
 create mode 100644 sourcecode/.gitignore
 create mode 100644 sourcecode/enter-chroot/enter-chroot.c
 create mode 100755 sourcecode/enter-chroot/install.sh
 delete mode 100644 sourcecode/sshfs-map/.gitignore

diff --git a/linux-utils/.local/bin/launch-chroot b/linux-utils/.local/bin/launch-chroot
deleted file mode 100755
index bc004b7..0000000
--- a/linux-utils/.local/bin/launch-chroot
+++ /dev/null
@@ -1,14 +0,0 @@
-#!/bin/sh
-
-# use with sudo -E
-
-ROOTDIR="${1:-/mnt}"
-USERNAME="${SUDO_USER:-ericonr}"
-
-chroot "$ROOTDIR" /bin/sudo -u $USERNAME \
-	env CHROOTED=1 \
-	XDG_RUNTIME_DIR=$XDG_RUNTIME_DIR \
-	WAYLAND_DISPLAY=$WAYLAND_DISPLAY \
-	DISPLAY=$DISPLAY \
-	DBUS_SESSION_BUS_ADDRESS=$DBUS_SESSION_BUS_ADDRESS \
-	/bin/fish -C "cd"
diff --git a/sourcecode/.gitignore b/sourcecode/.gitignore
new file mode 100644
index 0000000..312b172
--- /dev/null
+++ b/sourcecode/.gitignore
@@ -0,0 +1,2 @@
+sshfs-map/sshfs-map
+enter-chroot/enter-chroot
diff --git a/sourcecode/enter-chroot/enter-chroot.c b/sourcecode/enter-chroot/enter-chroot.c
new file mode 100644
index 0000000..4675c07
--- /dev/null
+++ b/sourcecode/enter-chroot/enter-chroot.c
@@ -0,0 +1,113 @@
+#define _XOPEN_SOURCE
+#define _BSD_SOURCE
+#include <stdbool.h>
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <limits.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+int main(int argc, char * const argv[])
+{
+	char *mntpoint = "/mnt", *shell = "/bin/fish";
+	bool check_chrooted = true;
+	int c, rv;
+
+	while ((c = getopt(argc, argv, "m:s:c")) != -1) {
+		switch (c) {
+			case 'm':
+				mntpoint = optarg;
+				break;
+			case 's':
+				shell = optarg;
+				break;
+			case 'c':
+				check_chrooted = false;
+				break;
+			default:
+				puts("wrong usage");
+				exit(EXIT_FAILURE);
+		}
+	}
+
+	uid_t
+		uid = getuid(),
+		euid = geteuid();
+	gid_t
+		gid = getgid(),
+		egid = getegid();
+
+	char cwd[PATH_MAX];
+	getcwd(cwd, PATH_MAX);
+
+	if (uid == 0 && gid == 0) {
+		fputs("running as root", stderr);
+	} else {
+		fprintf(stderr, "running as %d:%d\n", uid, gid);
+	}
+	fprintf(stderr, "effective perms %d:%d\n", euid, egid);
+
+	// check if <mntpoint> exists and/or can be accessed
+	{
+		int mntpoint_rv = 0;
+		struct stat mntpoint_stat = {0};
+		mntpoint_rv = stat(mntpoint, &mntpoint_stat);
+		if (mntpoint_rv == -1) {
+			fprintf(stderr, "couldn't stat '%s': %m\n", mntpoint);
+			exit(EXIT_FAILURE);
+		}
+	}
+
+	// check for the presense of <mntpoint>/chrooted
+	if (check_chrooted) {
+		char chrooted[PATH_MAX] = {0};
+		int chrooted_rv = 0;
+		struct stat chrooted_stat = {0};
+		strncpy(chrooted, mntpoint, PATH_MAX);
+		strncat(chrooted, "/chrooted", PATH_MAX - 1);
+		fprintf(stderr, "checking file in '%s'\n", chrooted);
+
+		chrooted_rv = stat(chrooted, &chrooted_stat);
+		if (chrooted_rv == -1 && errno == ENOENT) {
+			fprintf(stderr, "'%s' doesn't exist, aborting...\n", chrooted);
+			exit(EXIT_FAILURE);
+		}
+	}
+
+	rv = chroot(mntpoint);
+	if (rv == -1) {
+		fprintf(stderr, "chroot failed: %m\n");
+		exit(EXIT_FAILURE);
+	}
+
+	rv = setenv("CHROOTED", "1", 1);
+	if (rv == -1) {
+		fprintf(stderr, "CHROOTED not set in env: %m\n");
+		// non-fatal
+	}
+
+	rv = setgid(gid);
+	if (rv == -1) {
+		fprintf(stderr, "setgid failed: %m\n");
+		exit(EXIT_FAILURE);
+	}
+	rv = setuid(uid);
+	if(rv == -1) {
+		fprintf(stderr, "setuid failed: %m\n");
+		exit(EXIT_FAILURE);
+	}
+
+	rv = chdir(cwd);
+	if (rv == -1) {
+		fprintf(stderr, "chdir failed: %m\n");
+		// non-fatal
+	}
+
+	char *shellv[] = {shell, NULL};
+	rv = execv(shell, shellv);
+	fprintf(stderr, "execv %s failed: %m\n", shell);
+	return EXIT_FAILURE;
+}
diff --git a/sourcecode/enter-chroot/install.sh b/sourcecode/enter-chroot/install.sh
new file mode 100755
index 0000000..f0b94a5
--- /dev/null
+++ b/sourcecode/enter-chroot/install.sh
@@ -0,0 +1,8 @@
+#!/bin/sh
+
+set -e
+
+rm -f enter-chroot
+make enter-chroot
+
+install -m4755 enter-chroot /usr/local/bin/
diff --git a/sourcecode/sshfs-map/.gitignore b/sourcecode/sshfs-map/.gitignore
deleted file mode 100644
index f5d8282..0000000
--- a/sourcecode/sshfs-map/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-sshfs-map