android service 权限问题

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今天调哪个破 wifi, 老是有权限问题.....

1. 文件(夹)读写权限

init.rc 中建立test1 test2 test3 文件夹

mkdir /data/misc/test1 0770 root root

mkdir /data/misc/test2 0770 wifi wifi

mkdir /data/misc/test3 0770 system misc

其中

test1 目录的owner是root, group 也是root

test2 目录的owner是wifi , group 也是wifi

test3 目录的owner是system , group 是misc （任何用户都属于group misc）

service xxxx /system/bin/xxxx
user root
disabled
oneshot

service yyyy /system/bin/yyyy
user system
disabled
oneshot

service zzzz /system/bin/zzzz
user wifi
disabled
oneshot

结果:

xxxx 服务可以访问 test1, test2, test3

yyyy 服务可以访问 test3

zzzz 服务可以访问 test2, test3

Android 中mkdir 的定义

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int do_mkdir(int nargs, char **args)
{
mode_t mode = 0755;

/* mkdir <path> [mode] [owner] [group] */

if (nargs >= 3) {
mode = strtoul(args[2], 0, 8);
}

if (mkdir(args[1], mode)) {
return -errno;
}

if (nargs >= 4) {
uid_t uid = decode_uid(args[3]);
gid_t gid = -1;

if (nargs == 5) {
gid = decode_uid(args[4]);
}

if (chown(args[1], uid, gid)) {
return -errno;
}
}

return 0;
}
int do_mkdir(int nargs, char **args)
{
mode_t mode = 0755;

/* mkdir <path> [mode] [owner] [group] */

if (nargs >= 3) {
mode = strtoul(args[2], 0, 8);
}

if (mkdir(args[1], mode)) {
return -errno;
}

if (nargs >= 4) {
uid_t uid = decode_uid(args[3]);
gid_t gid = -1;

if (nargs == 5) {
gid = decode_uid(args[4]);
}

if (chown(args[1], uid, gid)) {
return -errno;
}
}

return 0;
}

2. Property 权限

Android Property 也是有权限的。

2.1 以前缀 ctl. 开头的控制属性，设置前，Android 代码会调用函数check_control_perms()检查调用者的 user id 和 group id

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struct {
const char *service;
unsigned int uid;
unsigned int gid;
} control_perms[] = {
{ "dumpstate",AID_SHELL, AID_LOG },
{NULL, 0, 0 }
};

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;
}
struct {
const char *service;
unsigned int uid;
unsigned int gid;
} control_perms[] = {
{ "dumpstate",AID_SHELL, AID_LOG },
{NULL, 0, 0 }
};

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;
}

2.2 其它属性，设置前，Android 代码会调用函数check_perms()检查调用者的 user id 和 group id

check_perms(msg.name, cr.uid, cr.gid)

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struct {
const char *prefix;
unsigned int uid;
unsigned int gid;
} property_perms[] = {
{ "net.rmnet0.", AID_RADIO, 0 },
{ "net.gprs.", AID_RADIO, 0 },
{ "net.ppp", AID_RADIO, 0 },
{ "ril.", AID_RADIO, 0 },
{ "gsm.", AID_RADIO, 0 },
{ "persist.radio", AID_RADIO, 0 },
{ "net.dns", AID_RADIO, 0 },
{ "net.", AID_SYSTEM, 0 },
{ "dev.", AID_SYSTEM, 0 },
{ "runtime.", AID_SYSTEM, 0 },
{ "hw.", AID_SYSTEM, 0 },
{ "sys.", AID_SYSTEM, 0 },
{ "service.", AID_SYSTEM, 0 },
{ "wlan.", AID_SYSTEM, 0 },
{ "dhcp.", AID_SYSTEM, 0 },
{ "dhcp.", AID_DHCP, 0 },
{ "vpn.", AID_SYSTEM, 0 },
{ "vpn.", AID_VPN, 0 },
{ "debug.", AID_SHELL, 0 },
{ "log.", AID_SHELL, 0 },
{ "service.adb.root", AID_SHELL, 0 },
{ "persist.sys.", AID_SYSTEM, 0 },
{ "persist.service.", AID_SYSTEM, 0 },
{ NULL, 0, 0 }
};

static int check_perms(const char *name, unsigned int uid, int gid)
{
int i;
if (uid == 0)
return 1;

if(!strncmp(name, "ro.", 3))
name +=3;

for (i = 0; property_perms[i].prefix; i++) {
int tmp;
if (strncmp(property_perms[i].prefix, name,
strlen(property_perms[i].prefix)) == 0) {
if ((uid && property_perms[i].uid == uid) ||
(gid && property_perms[i].gid == gid)) {
return 1;
}
}
}

return 0;
}
struct {
const char *prefix;
unsigned int uid;
unsigned int gid;
} property_perms[] = {
{ "net.rmnet0.", AID_RADIO, 0 },
{ "net.gprs.", AID_RADIO, 0 },
{ "net.ppp", AID_RADIO, 0 },
{ "ril.", AID_RADIO, 0 },
{ "gsm.", AID_RADIO, 0 },
{ "persist.radio", AID_RADIO, 0 },
{ "net.dns", AID_RADIO, 0 },
{ "net.", AID_SYSTEM, 0 },
{ "dev.", AID_SYSTEM, 0 },
{ "runtime.", AID_SYSTEM, 0 },
{ "hw.", AID_SYSTEM, 0 },
{ "sys.", AID_SYSTEM, 0 },
{ "service.", AID_SYSTEM, 0 },
{ "wlan.", AID_SYSTEM, 0 },
{ "dhcp.", AID_SYSTEM, 0 },
{ "dhcp.", AID_DHCP, 0 },
{ "vpn.", AID_SYSTEM, 0 },
{ "vpn.", AID_VPN, 0 },
{ "debug.", AID_SHELL, 0 },
{ "log.", AID_SHELL, 0 },
{ "service.adb.root", AID_SHELL, 0 },
{ "persist.sys.", AID_SYSTEM, 0 },
{ "persist.service.", AID_SYSTEM, 0 },
{ NULL, 0, 0 }
};

static int check_perms(const char *name, unsigned int uid, int gid)
{
int i;
if (uid == 0)
return 1;

if(!strncmp(name, "ro.", 3))
name +=3;

for (i = 0; property_perms[i].prefix; i++) {
int tmp;
if (strncmp(property_perms[i].prefix, name,
strlen(property_perms[i].prefix)) == 0) {
if ((uid && property_perms[i].uid == uid) ||
(gid && property_perms[i].gid == gid)) {
return 1;
}
}
}

return 0;
}

从代码中可以看到，任何不以property_perms[] 中定义的前缀开头的property 是

无法被除root以外的用户访问的，包括system用户。

3. 最后补充Android 的uid gid 定义

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#define AID_ROOT 0 /* traditional unix root user */

#define AID_SYSTEM 1000 /* system server */

#define AID_RADIO 1001 /* telephony subsystem, RIL */
#define AID_BLUETOOTH 1002 /* bluetooth subsystem */
#define AID_GRAPHICS 1003 /* graphics devices */
#define AID_INPUT 1004 /* input devices */
#define AID_AUDIO 1005 /* audio devices */
#define AID_CAMERA 1006 /* camera devices */
#define AID_LOG 1007 /* log devices */
#define AID_COMPASS 1008 /* compass device */
#define AID_MOUNT 1009 /* mountd socket */
#define AID_WIFI 1010 /* wifi subsystem */
#define AID_ADB 1011 /* android debug bridge (adbd) */
#define AID_INSTALL 1012 /* group for installing packages */
#define AID_MEDIA 1013 /* mediaserver process */
#define AID_DHCP 1014 /* dhcp client */
#define AID_SDCARD_RW 1015 /* external storage write access */
#define AID_VPN 1016 /* vpn system */
#define AID_KEYSTORE 1017 /* keystore subsystem */

#define AID_SHELL 2000 /* adb and debug shell user */
#define AID_CACHE 2001 /* cache access */
#define AID_DIAG 2002 /* access to diagnostic resources */

/* The 3000 series are intended for use as supplemental group id's only.
* They indicate special Android capabilities that the kernel is aware of. */
#define AID_NET_BT_ADMIN 3001 /* bluetooth: create any socket */
#define AID_NET_BT 3002 /* bluetooth: create sco, rfcomm or l2cap sockets */
#define AID_INET 3003 /* can create AF_INET and AF_INET6 sockets */
#define AID_NET_RAW 3004 /* can create raw INET sockets */
#define AID_NET_ADMIN 3005 /* can configure interfaces and routing tables. */

#define AID_MISC 9998 /* access to misc storage */
#define AID_NOBODY 9999

#define AID_APP 10000 /* first app user */
#define AID_ROOT 0 /* traditional unix root user */

#define AID_SYSTEM 1000 /* system server */

#define AID_RADIO 1001 /* telephony subsystem, RIL */
#define AID_BLUETOOTH 1002 /* bluetooth subsystem */
#define AID_GRAPHICS 1003 /* graphics devices */
#define AID_INPUT 1004 /* input devices */
#define AID_AUDIO 1005 /* audio devices */
#define AID_CAMERA 1006 /* camera devices */
#define AID_LOG 1007 /* log devices */
#define AID_COMPASS 1008 /* compass device */
#define AID_MOUNT 1009 /* mountd socket */
#define AID_WIFI 1010 /* wifi subsystem */
#define AID_ADB 1011 /* android debug bridge (adbd) */
#define AID_INSTALL 1012 /* group for installing packages */
#define AID_MEDIA 1013 /* mediaserver process */
#define AID_DHCP 1014 /* dhcp client */
#define AID_SDCARD_RW 1015 /* external storage write access */
#define AID_VPN 1016 /* vpn system */
#define AID_KEYSTORE 1017 /* keystore subsystem */

#define AID_SHELL 2000 /* adb and debug shell user */
#define AID_CACHE 2001 /* cache access */
#define AID_DIAG 2002 /* access to diagnostic resources */

/* The 3000 series are intended for use as supplemental group id's only.
* They indicate special Android capabilities that the kernel is aware of. */
#define AID_NET_BT_ADMIN 3001 /* bluetooth: create any socket */
#define AID_NET_BT 3002 /* bluetooth: create sco, rfcomm or l2cap sockets */
#define AID_INET 3003 /* can create AF_INET and AF_INET6 sockets */
#define AID_NET_RAW 3004 /* can create raw INET sockets */
#define AID_NET_ADMIN 3005 /* can configure interfaces and routing tables. */

#define AID_MISC 9998 /* access to misc storage */
#define AID_NOBODY 9999

#define AID_APP 10000 /* first app user */

可见root (AID_ROOT = 0) 的权限最高， app (AID_APP = 10000) 权限最低， misc (AID_MISC = 9998) 权限倒数第三低。

所以#1 中描述的目录test3的group 属性设置成了 misc, 则除了 app/nobody 这两个用户，

android系统中其它所有用户都有该目录的group权限！

本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/stevenliyong/archive/2010/03/03/5343085.aspx

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