[PATCH RFC rpcd] rc: new ubus object for handling /etc/init.d/ scripts

Rafał Miłecki zajec5 at gmail.com
Tue Jun 23 01:06:10 EDT 2020


From: Rafał Miłecki <rafal at milecki.pl>

This commit adds "rc" ubus object with "exec" method that allows calling
/etc/init.d/ scripts. It's useful for all kind of UIs (e.g. LuCI) and
custom apps.

The next step should be "list" method support listing add init scripts.

Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
---
I didn't implement custom timeout for waiting for init.d script yet. Two
reasons:
1. ubus call will eventually timeout on its own
2. it'd be nice to have some uloop_process helper for that
---
 CMakeLists.txt    |   2 +-
 include/rpcd/rc.h |   7 +++
 main.c            |   6 +-
 rc.c              | 140 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 152 insertions(+), 3 deletions(-)
 create mode 100644 include/rpcd/rc.h
 create mode 100644 rc.c

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3bfc286..26e011e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -38,7 +38,7 @@ INCLUDE_DIRECTORIES(${ubus_include_dir})
 FIND_PATH(ubox_include_dir libubox/blobmsg_json.h)
 INCLUDE_DIRECTORIES(${ubox_include_dir})
 
-ADD_EXECUTABLE(rpcd main.c exec.c session.c uci.c plugin.c)
+ADD_EXECUTABLE(rpcd main.c exec.c session.c uci.c rc.c plugin.c)
 TARGET_LINK_LIBRARIES(rpcd ${ubox} ${ubus} ${uci} ${blobmsg_json} ${json} ${crypt} dl)
 
 SET(PLUGINS "")
diff --git a/include/rpcd/rc.h b/include/rpcd/rc.h
new file mode 100644
index 0000000..ca00f56
--- /dev/null
+++ b/include/rpcd/rc.h
@@ -0,0 +1,7 @@
+// SPDX-License-Identifier: ISC OR MIT
+#ifndef __RPCD_RC_H
+#define __RPCD_RC_H
+
+int rpc_rc_api_init(struct ubus_context *ctx);
+
+#endif
diff --git a/main.c b/main.c
index 9a177cf..d77a814 100644
--- a/main.c
+++ b/main.c
@@ -25,10 +25,11 @@
 #include <signal.h>
 #include <sys/stat.h>
 
+#include <rpcd/exec.h>
+#include <rpcd/plugin.h>
+#include <rpcd/rc.h>
 #include <rpcd/session.h>
 #include <rpcd/uci.h>
-#include <rpcd/plugin.h>
-#include <rpcd/exec.h>
 
 static struct ubus_context *ctx;
 static bool respawn = false;
@@ -113,6 +114,7 @@ int main(int argc, char **argv)
 
 	rpc_session_api_init(ctx);
 	rpc_uci_api_init(ctx);
+	rpc_rc_api_init(ctx);
 	rpc_plugin_api_init(ctx);
 
 	hangup = getenv("RPC_HANGUP");
diff --git a/rc.c b/rc.c
new file mode 100644
index 0000000..a354332
--- /dev/null
+++ b/rc.c
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: ISC OR MIT
+/*
+ * rpcd - UBUS RPC server
+ *
+ * Copyright (C) 2020 Rafał Miłecki <rafal at milecki.pl>
+ */
+
+#include <fcntl.h>
+#include <linux/limits.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+
+#include <libubox/blobmsg.h>
+#include <libubox/uloop.h>
+#include <libubus.h>
+
+#include <rpcd/rc.h>
+
+enum {
+	RC_EXEC_NAME,
+	RC_EXEC_ACTION,
+	__RC_EXEC_MAX
+};
+
+static const struct blobmsg_policy rc_exec_policy[] = {
+	[RC_EXEC_NAME] = { "name", BLOBMSG_TYPE_STRING },
+	[RC_EXEC_ACTION] = { "action", BLOBMSG_TYPE_STRING },
+};
+
+struct rc_exec_context {
+	struct uloop_process process;
+	struct ubus_context *ctx;
+	struct ubus_request_data req;
+};
+
+static void rc_exec_cb(struct uloop_process *p, int stat)
+{
+	struct rc_exec_context *c = container_of(p, struct rc_exec_context, process);
+
+	ubus_complete_deferred_request(c->ctx, &c->req, UBUS_STATUS_OK);
+
+	free(c);
+}
+
+static int rc_exec(struct ubus_context *ctx, struct ubus_object *obj,
+		   struct ubus_request_data *req, const char *method,
+		   struct blob_attr *msg)
+{
+	struct blob_attr *tb[__RC_EXEC_MAX];
+	struct rc_exec_context *c;
+	struct stat s;
+	const char *action;
+	const char *name;
+	char script[PATH_MAX];
+	pid_t pid;
+	const char *chr;
+	int fd;
+
+	blobmsg_parse(rc_exec_policy, __RC_EXEC_MAX, tb, blobmsg_data(msg), blobmsg_data_len(msg));
+
+	if (!tb[RC_EXEC_NAME] || !tb[RC_EXEC_ACTION])
+		return UBUS_STATUS_INVALID_ARGUMENT;
+
+	name = blobmsg_get_string(tb[RC_EXEC_NAME]);
+
+	/* Validate script name */
+	for (chr = name; (chr = strchr(chr, '.')); chr++) {
+		if (*(chr + 1) == '.')
+			return UBUS_STATUS_INVALID_ARGUMENT;
+	}
+	if (strchr(name, '/'))
+		return UBUS_STATUS_INVALID_ARGUMENT;
+
+	/* Validate script privileges */
+	snprintf(script, sizeof(script), "/etc/init.d/%s", name);
+	if (stat(script, &s))
+		return UBUS_STATUS_NOT_FOUND;
+	if (s.st_uid != 0 || s.st_gid != 0 || !(s.st_mode & S_IXUSR) || (s.st_mode & (S_IWGRP | S_IWOTH)))
+		return UBUS_STATUS_PERMISSION_DENIED;
+
+	action = blobmsg_get_string(tb[RC_EXEC_ACTION]);
+	if (strcmp(action, "disable") &&
+	    strcmp(action, "enable") &&
+	    strcmp(action, "stop") &&
+	    strcmp(action, "start") &&
+	    strcmp(action, "restart") &&
+	    strcmp(action, "reload"))
+		return UBUS_STATUS_INVALID_ARGUMENT;
+
+	c = calloc(1, sizeof(*c));
+	if (!c)
+		return UBUS_STATUS_UNKNOWN_ERROR;
+
+	pid = fork();
+	switch (pid) {
+	case -1:
+		free(c);
+		return UBUS_STATUS_UNKNOWN_ERROR;
+	case 0:
+		/* Set stdin, stdout & stderr to /dev/null */
+		fd = open("/dev/null", O_RDWR);
+		if (fd >= 0) {
+			dup2(fd, 0);
+			dup2(fd, 1);
+			dup2(fd, 2);
+			close(fd);
+		}
+
+		execl(script, script, action, NULL);
+		exit(errno);
+	default:
+		c->ctx = ctx;
+		c->process.pid = pid;
+		c->process.cb = rc_exec_cb;
+		uloop_process_add(&c->process);
+
+		ubus_defer_request(ctx, req, &c->req);
+
+		return 0; /* Deferred */
+	}
+}
+
+int rpc_rc_api_init(struct ubus_context *ctx)
+{
+	static const struct ubus_method rc_methods[] = {
+		UBUS_METHOD("exec", rc_exec, rc_exec_policy),
+	};
+
+	static struct ubus_object_type rc_type =
+		UBUS_OBJECT_TYPE("rc", rc_methods);
+
+	static struct ubus_object obj = {
+		.name = "rc",
+		.type = &rc_type,
+		.methods = rc_methods,
+		.n_methods = ARRAY_SIZE(rc_methods),
+	};
+
+	return ubus_add_object(ctx, &obj);
+}
-- 
2.26.1


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