Android: 启动init.rc 中service的权限问题

通过property_set("ctl.start", service_xx);

来启动init.rc中的service是一个很方便方法来调用某个可执行程序或某个脚本程序

service service_xx/system/bin/xx

disabled
oneshot

但在非AID_ROOT、AID_SYSTEM 用户的进程中调用ctl.start ctl.stop会碰到权限问题:

system/core/init/property_service.c

/* * White list of UID that are allowed to start/stop services. * Currently there are no user apps that require. */struct { const char *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. */static int check_control_perms(const char *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进程才有权限star/stop services

因此，如果我们碰到了权限问题，根据log提示，在/system/core/include/private/android_filesystem_config.h

中查到进程定义，添加到control_perms[]列表

比如，uid ==AID_WIFI的某个程序需要权限启动service_xx

control_perms[] = {
{ "dumpstate",AID_SHELL, AID_LOG },

+ { "service_xx",AID_WIFI, AID_WIFI},
{NULL, 0, 0 }
};

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