Add helper program for running services

We no longer need to keep entire scripts in init program (i.e. saving space)
and reduce the code and complexity of the init program.

The runsvc tool can later be extended to do more complex child setup, such
as configuring namespaces or seccomp without adding complexity or memory
footprint to init.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>

3 files changed, 304 insertions, 0 deletions

diff --git a/cmd/runsvc/env.c b/cmd/runsvc/env.c
new file mode 100644
index 0000000..4fe2368
--- /dev/null
+++ b/cmd/runsvc/env.c
@@ -0,0 +1,130 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#include "runsvc.h"
+
+struct entry {
+	struct entry *next;
+	char data[];
+};
+
+extern char **environ;
+
+static void free_list(struct entry *list)
+{
+	struct entry *e;
+
+	while (list != NULL) {
+		e = list;
+		list = list->next;
+		free(e);
+	}
+}
+
+static struct entry *parse_list(rdline_t *rd)
+{
+	struct entry *e, *list = NULL;
+	char *ptr;
+
+	while (rdline(rd) == 0) {
+		ptr = rd->buffer;
+
+		while (*ptr != '\0' && *ptr != ' ' && *ptr != '=')
+			++ptr;
+
+		if (*ptr == ' ')
+			memmove(ptr, ptr + 1, strlen(ptr + 1) + 1);
+
+		if (*(ptr++) != '=') {
+			fprintf(stderr, "%s: %zu: line is not of the shape "
+					"'key = value', skipping\n",
+				rd->filename, rd->lineno);
+			continue;
+		}
+
+		if (*ptr == ' ')
+			memmove(ptr, ptr + 1, strlen(ptr + 1) + 1);
+
+		if (unescape(ptr)) {
+			fprintf(stderr, "%s: %zu: malformed string constant, "
+					"skipping\n",
+				rd->filename, rd->lineno);
+			continue;
+		}
+
+		e = calloc(1, sizeof(*e) + strlen(rd->buffer) + 1);
+		if (e == NULL)
+			goto fail_oom;
+
+		strcpy(e->data, rd->buffer);
+		e->next = list;
+		list = e;
+	}
+
+	return list;
+fail_oom:
+	fputs("out of memory\n", stderr);
+	free_list(list);
+	return NULL;
+}
+
+static struct entry *list_from_file(void)
+{
+	struct entry *list;
+	rdline_t rd;
+	int fd;
+
+	fd = open(ENVFILE, O_RDONLY);
+	if (fd < 0) {
+		perror(ENVFILE);
+		return NULL;
+	}
+
+	rdline_init(&rd, fd, ENVFILE, 0, NULL);
+	list = parse_list(&rd);
+	close(fd);
+	return list;
+}
+
+int initenv(void)
+{
+	struct entry *list, *e;
+	int i, count;
+	char **envp;
+
+	list = list_from_file();
+	if (list == NULL)
+		return -1;
+
+	for (count = 0, e = list; e != NULL; e = e->next)
+		++count;
+
+	envp = malloc((count + 1) * sizeof(char *));
+	if (envp == NULL) {
+		fputs("out of memory\n", stderr);
+		free_list(list);
+		return -1;
+	}
+
+	for (i = 0, e = list; e != NULL; e = e->next)
+		envp[i] = e->data;
+
+	envp[i] = NULL;
+
+	environ = envp;
+	return 0;
+}
diff --git a/cmd/runsvc/runsvc.c b/cmd/runsvc/runsvc.c
new file mode 100644
index 0000000..a8e5bb2
--- /dev/null
+++ b/cmd/runsvc/runsvc.c
@@ -0,0 +1,138 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#include "runsvc.h"
+
+static int setup_tty(const char *ctty)
+{
+	int fd;
+
+	if (ctty != NULL) {
+		fd = open(ctty, O_RDWR);
+		if (fd < 0) {
+			perror(ctty);
+			return -1;
+		}
+
+		close(STDIN_FILENO);
+		close(STDOUT_FILENO);
+		close(STDERR_FILENO);
+
+		setsid();
+
+		dup2(fd, STDIN_FILENO);
+		dup2(fd, STDOUT_FILENO);
+		dup2(fd, STDERR_FILENO);
+		close(fd);
+	}
+
+	return 0;
+}
+
+/*****************************************************************************/
+
+static NORETURN void argv_exec(exec_t *e)
+{
+	char **argv = alloca(e->argc + 1), *ptr;
+	int i;
+
+	for (ptr = e->args, i = 0; i < e->argc; ++i, ptr += strlen(ptr) + 1)
+		argv[i] = ptr;
+
+	argv[i] = NULL;
+	execvp(argv[0], argv);
+	perror(argv[0]);
+	exit(EXIT_FAILURE);
+}
+
+static int runlst_wait(exec_t *list)
+{
+	pid_t ret, pid;
+	int status;
+
+	for (; list != NULL; list = list->next) {
+		pid = fork();
+
+		if (pid == 0)
+			argv_exec(list);
+
+		if (pid == -1) {
+			perror("fork");
+			return EXIT_FAILURE;
+		}
+
+		do {
+			ret = waitpid(pid, &status, 0);
+		} while (ret != pid);
+
+		if (!WIFEXITED(status))
+			return EXIT_FAILURE;
+
+		if (WEXITSTATUS(status) != EXIT_SUCCESS)
+			return WEXITSTATUS(status);
+	}
+
+	return EXIT_SUCCESS;
+}
+
+/*****************************************************************************/
+
+int main(int argc, char **argv)
+{
+	int dirfd, ret = EXIT_FAILURE;
+	service_t *svc = NULL;
+
+	if (argc != 3) {
+		fputs("usage: runsvc <directory> <filename>\n", stderr);
+		goto out;
+	}
+
+	if (getppid() != 1) {
+		fputs("must be run by init!\n", stderr);
+		goto out;
+	}
+
+	dirfd = open(argv[1], O_RDONLY | O_DIRECTORY);
+	if (dirfd < 0) {
+		perror(argv[1]);
+		goto out;
+	}
+
+	svc = rdsvc(dirfd, argv[2], RDSVC_NO_FNAME | RDSVC_NO_DEPS);
+	close(dirfd);
+	if (svc == NULL)
+		goto out;
+
+	if (svc->exec == NULL) {
+		ret = EXIT_SUCCESS;
+		goto out;
+	}
+
+	if (initenv())
+		goto out;
+
+	if (setup_tty(svc->ctty))
+		goto out;
+
+	if (svc->exec->next == NULL)
+		argv_exec(svc->exec);
+
+	ret = runlst_wait(svc->exec);
+out:
+	delsvc(svc);
+	return ret;
+}
diff --git a/cmd/runsvc/runsvc.h b/cmd/runsvc/runsvc.h
new file mode 100644
index 0000000..15785d3
--- /dev/null
+++ b/cmd/runsvc/runsvc.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#ifndef RUNSVC_H
+#define RUNSVC_H
+
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <fcntl.h>
+
+#include "service.h"
+#include "util.h"
+
+#define ENVFILE ETCPATH "/initd.env"
+
+int initenv(void);
+
+#endif /* RUNSVC_H */