1 files changed, 269 insertions, 0 deletions
diff --git a/editasroot.c b/editasroot.c
new file mode 100644
index 0000000..0036791
--- /dev/null
+++ b/editasroot.c
@@ -0,0 +1,269 @@
+/* See LICENSE file for copyright and license details. */
+#include <sys/prctl.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <paths.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define TEMPFILEPATTERN "tmpXXXXXX"
+
+
+static const char *argv0 = "editasroot";
+static const char *unlink_this = NULL;
+
+
+static void
+usage(void)
+{
+	fprintf(stderr, "usage: %s file\n", argv0);
+	exit(1);
+}
+
+
+static void
+cleanup(void)
+{
+	if (unlink_this) {
+		unlink(unlink_this);
+		unlink_this = NULL;
+	}
+}
+
+
+static void
+graceful_exit(int signo)
+{
+	cleanup();
+	if (signal(signo, SIG_DFL) != SIG_ERR)
+		raise(signo);
+	exit(1);
+}
+
+
+static const char *
+get_editor(void)
+{
+	const char *editor = NULL;
+	int fd, isbg;
+
+	fd = open(_PATH_TTY, O_RDONLY);
+        if (fd < 0) {
+		fprintf(stderr, "%s: open %s O_RDONLY: %s", argv0, _PATH_TTY, strerror(errno));
+		exit(1);
+	}
+        isbg = getpgrp() != tcgetpgrp(fd);
+        close(fd);
+
+	if (isbg)
+		editor = getenv("VISUAL");
+	if (!editor || !*editor) {
+		editor = getenv("EDITOR");
+		if (!editor || !*editor) {
+			fprintf(stderr, "%s: warning: EDITOR not set, defaulting to 'vi'\n", argv0);
+			editor = "vi";
+		}
+	}
+
+	return editor;
+}
+
+
+static char *
+get_tmpfile_pattern(void)
+{
+	const char *tmpdir = NULL;
+	char *path, *p;
+
+	tmpdir = getenv("XDG_RUNTIME_DIR");
+	if (!tmpdir || !*tmpdir)
+		tmpdir = _PATH_TMP;
+
+	path = malloc(strlen(tmpdir) + sizeof("/"TEMPFILEPATTERN));
+	if (!path) {
+		fprintf(stderr, "%s: malloc: %s", argv0, strerror(ENOMEM));
+		exit(1);
+	}
+	p = stpcpy(path, tmpdir);
+	p -= p[-1] == '/';
+	stpcpy(p, "/"TEMPFILEPATTERN);
+
+	return path;
+}
+
+
+static void
+copy_file(int destfd, const char *destfname, int srcfd, const char *srcfname)
+{
+	char buf[BUFSIZ];
+	ssize_t r, w, p;
+
+	for (;;) {
+		r = read(srcfd, buf, sizeof(buf));
+		if (r <= 0) {
+			if (!r)
+				break;
+			fprintf(stderr, "%s: read %s: %s", argv0, srcfname, strerror(errno));
+			exit(1);
+		}
+
+		for (p = 0; p < r; p += w) {
+			w = write(destfd, buf, (size_t)(r - p));
+			if (r <= 0) {
+				fprintf(stderr, "%s: write %s: %s", argv0, destfname, strerror(errno));
+				exit(1);
+			}
+		}
+	}
+}
+
+
+static pid_t
+run_child(const char *file, int fd, int close_this)
+{
+	char fdstr[3 * sizeof(fd) + 2];
+	pid_t pid;
+
+	switch (pid = fork()) {
+	case -1:
+		fprintf(stderr, "%s: fork: %s", argv0, strerror(errno));
+		exit(1);
+
+	case 0:
+		close(STDIN_FILENO);
+		close(STDOUT_FILENO);
+		close(close_this);
+		prctl(PR_SET_PDEATHSIG, SIGKILL);
+		sprintf(fdstr, "%i", fd);
+		execlp("asroot", "asroot", LIBEXECDIR"/copier", file, fdstr, NULL);
+		fprintf(stderr, "%s: execlp asroot: %s\n", argv0, strerror(errno));
+		exit(1);
+
+	default:
+		return pid;
+	}
+}
+
+
+static void
+run_editor(const char *editor, const char *file, int close_this)
+{
+	pid_t pid;
+	int status;
+
+	switch (pid = fork()) {
+	case -1:
+		fprintf(stderr, "%s: fork: %s", argv0, strerror(errno));
+		exit(1);
+
+	case 0:
+		close(close_this);
+		execlp(editor, editor, "--", file, NULL);
+		fprintf(stderr, "%s: execlp %s: %s\n", argv0, editor, strerror(errno));
+		exit(1);
+
+	default:
+		break;
+	}
+
+	if (waitpid(pid, &status, 0) != pid) {
+		fprintf(stderr, "%s: waitpid %s 0: %s", argv0, editor, strerror(errno));
+		exit(1);
+	}
+
+	if (status)
+		exit(WIFEXITED(status) ? WEXITSTATUS(status) : 1);
+}
+
+
+int
+main(int argc, char *argv[])
+{
+	const char *editor;
+	char *path;
+	int fd, fds[2], status, i;
+	pid_t pid;
+
+	if (!argc)
+		usage();
+	argv0 = *argv++;
+	if (--argc != 1)
+		usage();
+
+	editor = get_editor();
+
+	/* Start copier, with a bidirectional channel to it for copying the file */
+	if (socketpair(PF_LOCAL, SOCK_STREAM, 0, fds)) {
+		fprintf(stderr, "%s: socketpair PF_LOCAL SOCK_STREAM 0: %s", argv0, strerror(errno));
+		exit(1);
+	}
+	pid = run_child(argv[0], fds[1], fds[0]);
+	close(fds[1]);
+
+	/* Make sure (enough) tmpfile is unlinked if killed */
+	for (i = 1; i < NSIG; i++)
+		if (i != SIGCHLD)
+			signal(i, graceful_exit);
+
+	/* Create tmpfile from file to edit */
+	path = get_tmpfile_pattern();
+	fd = mkstemp(path);
+	if (fd < 0) {
+		fprintf(stderr, "%s: mkstemp %s: %s", argv0, path, strerror(errno));
+		exit(1);
+	}
+	unlink_this = path;
+	if (atexit(cleanup)) {
+		fprintf(stderr, "%s: atexit: %s", argv0, strerror(errno));
+		exit(1);
+	}
+	copy_file(fd, path, fds[0], "<socket to child>");
+	if (close(fd)) {
+		fprintf(stderr, "%s: write %s: %s", argv0, path, strerror(errno));
+		exit(1);
+	}
+	if (shutdown(fds[0], SHUT_RD)) {
+		fprintf(stderr, "%s: shutdown <socket to parent> SHUT_RD: %s\n", argv0, strerror(errno));
+		exit(1);
+	}
+
+	/* Start file editor */
+	run_editor(editor, path, fds[0]);
+
+	/* Signal to child that editor exited as expected */
+	if (write(fds[0], &(char){1}, 1) != 1) {
+		fprintf(stderr, "%s: write <socket to child>: %s", argv0, strerror(errno));
+		exit(1);
+	}
+
+	/* Rewrite file from tmpfile and unlink tmpfile */
+	fd = open(path, O_RDONLY);
+	if (fd < 0) {
+		fprintf(stderr, "%s: open %s O_RDONLY: %s", argv0, path, strerror(errno));
+		exit(1);
+	}
+	copy_file(fds[0], "<socket to child>", fd, path);
+	if (close(fd)) {
+		fprintf(stderr, "%s: read %s: %s", argv0, path, strerror(errno));
+		exit(1);
+	}
+	if (close(fds[0])) {
+		fprintf(stderr, "%s: write <socket to child>: %s", argv0, strerror(errno));
+		exit(1);
+	}
+	unlink(unlink_this);
+	unlink_this = NULL;
+	free(path);
+
+	/* Wait for exit copier to exit */
+	if (waitpid(pid, &status, 0) != pid) {
+		fprintf(stderr, "%s: waitpid <child> 0: %s", argv0, strerror(errno));
+		exit(1);
+	}
+	return WIFEXITED(status) ? WEXITSTATUS(status) : 1;
+}