設定ctl.start 屬性啟動init.rc 中service以及許可權問題
阿新 • • 發佈:2019-01-31
通過property_set("ctl.start", service_xx);
來啟動init.rc中的service是一個很方便方法來呼叫某個可執行程式或某個指令碼程式
service service_xx /system/bin/xx
disabled
oneshot
但在非AID_ROOT、AID_SYSTEM 使用者的程序中呼叫ctl.start ctl.stop會碰到許可權問題:
system/core/init/property_service.c
[cpp] view plain copy print?- /*
- * White list of UID that are allowed to start/stop services.
- * Currently there are no user apps that require.
- */
- struct {
- constchar *service;
- unsigned int uid;
- unsigned int gid;
- } control_perms[] = {
- { "dumpstate",AID_SHELL, AID_LOG },
- {NULL, 0, 0 }
- };
- /*
- * Checks permissions for starting/stoping system services.
- * AID_SYSTEM and AID_ROOT are always allowed.
- *
- * Returns 1 if uid allowed, 0 otherwise.
- */
- staticint check_control_perms(constchar *name, int uid, int gid) {
- int i;
- if (uid == AID_SYSTEM || uid == AID_ROOT)
- return 1;
- /* Search the ACL */
- for (i = 0; control_perms[i].service; i++) {
- if (strcmp(control_perms[i].service, name) == 0) {
- if ((uid && control_perms[i].uid == uid) ||
- (gid && control_perms[i].gid == gid)) {
- return 1;
- }
- }
- }
- return 0;
- }
只有uid == AID_SYSTEM || uid == AID_ROOT
或符合 control_perms[] = {
{ "dumpstate",AID_SHELL, AID_LOG },
{NULL, 0, 0 }
}; 的uid程序才有許可權star/stop services
因此,如果我們碰到了許可權問題,根據log提示,在/system/core/include/private/android_filesystem_config.h
中查到程序定義,新增到control_perms[]列表
比如,uid ==AID_WIFI的某個程式需要許可權啟動service_xx
control_perms[] = {
{ "dumpstate",AID_SHELL, AID_LOG },
+ { "service_xx ",AID_WIFI, AID_WIFI},
{NULL, 0, 0 }
};