Android用户和用户组的定义
Android用户和用户组的定义
在system/core/include/private/android_filesystem_config.h中可以看到如下定义。
/* This is the master Users and Groups config for the platform.
** DO NOT EVER RENUMBER.
*/
#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 /* system */
#define AID_KEYSTORE 1017 /* keystore subsystem */
#define AID_USB 1018 /* USB devices */
#define AID_DRM 1019 /* DRM server */
#define AID_MDNSR 1020 /* MulticastDNSResponder (service discovery) */
#define AID_GPS 1021 /* GPS daemon */
#define AID_UNUSED1 1022 /* deprecated, DO NOT USE */
#define AID_MEDIA_RW 1023 /* internal media storage write access */
#define AID_MTP 1024 /* MTP USB driver access */
#define AID_UNUSED2 1025 /* deprecated, DO NOT USE */
#define AID_DRMRPC 1026 /* group for drm rpc */
#define AID_NFC 1027 /* nfc subsystem */
#define AID_SDCARD_R 1028 /* external storage read access */
#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_NET_BW_STATS 3006 /* read bandwidth statistics */
#define AID_NET_BW_ACCT 3007 /* change bandwidth statistics accounting */
#define AID_NET_BT_STACK 3008 /* bluetooth: access config files */
#define AID_MISC 9998 /* access to misc storage */
#define AID_NOBODY 9999
#define AID_APP 10000 /* first app user */
#define AID_ISOLATED_START 99000 /* start of uids for fully isolated sandboxed processes */
#define AID_ISOLATED_END 99999 /* end of uids for fully isolated sandboxed processes */
#define AID_USER 100000 /* offset for uid ranges for each user */
#define AID_SHARED_GID_START 50000 /* start of gids for apps in each user to share */
#define AID_SHARED_GID_END 59999 /* start of gids for apps in each user to share */
在Android的Java层中id的定义数值和本地中的内容是相同的。这些定义在framworks/base/core/java/android/os/Process.java中
/**
* Defines the UID/GID under which system code runs.
*/
public static final int SYSTEM_UID = 1000;
/**
* Defines the UID/GID under which the telephony code runs.
*/
public static final int PHONE_UID = 1001;
/**
* Defines the UID/GID for the user shell.
* @hide
*/
public static final int SHELL_UID = 2000;
/**
* Defines the UID/GID for the log group.
* @hide
*/
public static final int LOG_UID = 1007;
/**
* Defines the UID/GID for the WIFI supplicant process.
* @hide
*/
public static final int WIFI_UID = 1010;
/**
* Defines the UID/GID for the mediaserver process.
* @hide
*/
public static final int MEDIA_UID = 1013;
/**
* Defines the UID/GID for the DRM process.
* @hide
*/
public static final int DRM_UID = 1019;
/**
* Defines the GID for the group that allows write access to the SD card.
* @hide
*/
public static final int SDCARD_RW_GID = 1015;
/**
* Defines the UID/GID for the group that controls VPN services.
* @hide
*/
public static final int VPN_UID = 1016;
/**
* Defines the UID/GID for the NFC service process.
* @hide
*/
public static final int NFC_UID = 1027;
/**
* Defines the UID/GID for the Bluetooth service process.
* @hide
*/
public static final int BLUETOOTH_UID = 1002;
/**
* Defines the GID for the group that allows write access to the internal media storage.
* @hide
*/
public static final int MEDIA_RW_GID = 1023;
/**
* Defines the start of a range of UIDs (and GIDs), going from this
* number to {@link #LAST_APPLICATION_UID} that are reserved for assigning
* to applications.
*/
public static final int FIRST_APPLICATION_UID = 10000;
/**
* Last of application-specific UIDs starting at
* {@link #FIRST_APPLICATION_UID}.
*/
public static final int LAST_APPLICATION_UID = 19999;
/**
* First uid used for fully isolated sandboxed processes (with no permissions of their own)
* @hide
*/
public static final int FIRST_ISOLATED_UID = 99000;
/**
* Last uid used for fully isolated sandboxed processes (with no permissions of their own)
* @hide
*/
public static final int LAST_ISOLATED_UID = 99999;
基于用户id的安全机制，其实使用的是标准的Linux的权限控制的机制，本用户、本组的和其他用户各自有读、写、执行3中权限。系统在这方面的控制主要有：
>文件系统的各个文件具有Uid和Gid，并指定权限。
>每个进行具有自己的Uid和Gid，并指定它属于哪些组。
>每个进程可以根据本用户规则访问其Uid可以访问的文件。
>每个进程可以根据组规则访问其所属的所有组(Groups)可以访问的文件。
>如果文件定义了其他的用户可以访问的权限，可以被任何任何程序访问。
>任何进程都不可以访问不具有权限的文件。
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