Come ottenere nome utente utilizzando uid su Android

Question

ho avuto diversi fluidi come questo: 10022, 10011, 1000

In realtà io conosco i nomi utente di loro sono u0_a22, u0_a11, system.

Ma la domanda è: come posso ottenere il nome utente utilizzando i codici? Non esiste alcun file/etc/passwd.

Answer 1

Gli UID sono hardcoded per l'implementazione android di libc (bionic) e sono forniti anche in intervalli per app. android_filesystem_config.h spiega la mappatura.

Dovresti essere in grado di utilizzare gli stub bionici (C++) per getpwuid(uid_t).

Per ulteriori informazioni sugli stub, vedere this AOSP documentation.

Answer 2

Ho scritto una classe di utilità per ottenere il nome UID/GID in base ai valori di hardcoding da android_filesystem_config.h.

utilizzati:

String uid = AndroidFilesystemConfig.getNameForId(1000); 

AndroidFilesystemConfig.java

import android.os.Build; 
import android.util.SparseArray; 

import java.util.Locale; 

/** 
* <p>System Users and Groups for the Android platform as specified in 
* <a href="https://android.googlesource.com/platform/system/core/+/master/include/private/android_filesystem_config.h">android_filesystem_config.h</a>.</p> 
* 
* <p>Last updated: April 20th, 2016</p> 
* 
* <p><b>Note:</b> Some OEMs may have specific UIDs for other system users not in this class.</p> 
*/ 
public class AndroidFilesystemConfig { 

    /* first app user */ 
    private static final int AID_APP = 10000; 

    /* offset for uid ranges for each user */ 
    private static final int AID_USER = 100000; 

    /* start of gids for apps in each user to share */ 
    private static final int AID_SHARED_GID_START = 50000; 

    /* end of gids for apps in each user to share */ 
    private static final int AID_SHARED_GID_END = 59999; 

    private static final SparseArray<String> SYSTEM_IDS = new SparseArray<>(); 

    static { 
    putSystemId(0, "root"); /* traditional unix root user */ 
    putSystemId(1000, "system"); /* system server */ 
    putSystemId(1001, "radio"); /* telephony subsystem, RIL */ 
    putSystemId(1002, "bluetooth"); /* bluetooth subsystem */ 
    putSystemId(1003, "graphics"); /* graphics devices */ 
    putSystemId(1004, "input"); /* input devices */ 
    putSystemId(1005, "audio"); /* audio devices */ 
    putSystemId(1006, "camera"); /* camera devices */ 
    putSystemId(1007, "log"); /* log devices */ 
    putSystemId(1008, "compass"); /* compass device */ 
    putSystemId(1009, "mount"); /* mountd socket */ 
    putSystemId(1010, "wifi"); /* wifi subsystem */ 
    putSystemId(1011, "adb"); /* android debug bridge (adbd) */ 
    putSystemId(1012, "install"); /* group for installing packages */ 
    putSystemId(1013, "media"); /* mediaserver process */ 
    putSystemId(1014, "dhcp"); /* dhcp client */ 
    putSystemId(1015, "sdcard_rw"); /* external storage write access */ 
    putSystemId(1016, "vpn"); /* vpn system */ 
    putSystemId(1017, "keystore"); /* keystore subsystem */ 
    putSystemId(1018, "usb"); /* USB devices */ 
    putSystemId(1019, "drm"); /* DRM server */ 
    putSystemId(1020, "mdnsr"); /* MulticastDNSResponder (service discovery) */ 
    putSystemId(1021, "gps"); /* GPS daemon */ 
    // 1022 is deprecated and not used. 
    putSystemId(1023, "media_rw"); /* internal media storage write access */ 
    putSystemId(1024, "mtp"); /* MTP USB driver access */ 
    // 1025 is deprecated and not used. 
    putSystemId(1026, "drmrpc"); /* group for drm rpc */ 
    putSystemId(1027, "nfc"); /* nfc subsystem */ 
    putSystemId(1028, "sdcard_r"); /* external storage read access */ 
    putSystemId(1029, "clat"); /* clat part of nat464 */ 
    putSystemId(1030, "loop_radio"); /* loop radio devices */ 
    putSystemId(1031, "mediadrm"); /* MediaDrm plugins */ 
    putSystemId(1032, "package_info"); /* access to installed package details */ 
    putSystemId(1033, "sdcard_pics"); /* external storage photos access */ 
    putSystemId(1034, "sdcard_av"); /* external storage audio/video access */ 
    putSystemId(1035, "sdcard_all"); /* access all users external storage */ 
    putSystemId(1036, "logd"); /* log daemon */ 
    putSystemId(1037, "shared_relro"); /* creator of shared GNU RELRO files */ 
    putSystemId(1038, "dbus"); /* dbus-daemon IPC broker process */ 
    putSystemId(1039, "tlsdate"); /* tlsdate unprivileged user */ 
    putSystemId(1040, "mediaex"); /* mediaextractor process */ 
    putSystemId(1041, "audioserver"); /* audioserver process */ 
    putSystemId(1042, "metrics_coll"); /* metrics_collector process */ 
    putSystemId(1043, "metricsd"); /* metricsd process */ 
    putSystemId(1044, "webserv"); /* webservd process */ 
    putSystemId(1045, "debuggerd"); /* debuggerd unprivileged user */ 
    putSystemId(1046, "mediacodec"); /* mediacodec process */ 
    putSystemId(1047, "cameraserver"); /* cameraserver process */ 
    putSystemId(1048, "firewall"); /* firewalld process */ 
    putSystemId(1049, "trunks"); /* trunksd process (TPM daemon) */ 
    putSystemId(1050, "nvram"); /* Access-controlled NVRAM */ 
    putSystemId(1051, "dns"); /* DNS resolution daemon (system: netd) */ 
    putSystemId(1052, "dns_tether"); /* DNS resolution daemon (tether: dnsmasq) */ 
    putSystemId(1053, "webview_zygote"); /* WebView zygote process */ 
    putSystemId(1054, "vehicle_network"); /* Vehicle network service */ 
    putSystemId(1055, "media_audio"); /* GID for audio files on internal media storage */ 
    putSystemId(1056, "media_video"); /* GID for video files on internal media storage */ 
    putSystemId(1057, "media_image"); /* GID for image files on internal media storage */ 

    putSystemId(2000, "shell"); /* adb and debug shell user */ 
    putSystemId(2001, "cache"); /* cache access */ 
    putSystemId(2002, "diag"); /* access to diagnostic resources */ 

    /* The range 2900-2999 is reserved for OEMs */ 

    // The 3000 series are intended for use as supplemental group id's only. They indicate 
    // special Android capabilities that the kernel is aware of. 
    putSystemId(3001, "net_bt_admin"); /* bluetooth: get any socket */ 
    putSystemId(3002, "net_bt"); /* bluetooth: get sco, rfcomm or l2cap sockets */ 
    putSystemId(3003, "inet"); /* can get AF_INET and AF_INET6 sockets */ 
    putSystemId(3004, "net_raw"); /* can get raw INET sockets */ 
    putSystemId(3005, "net_admin"); /* can configure interfaces and routing tables. */ 
    putSystemId(3006, "net_bw_stats"); /* read bandwidth statistics */ 
    putSystemId(3007, "net_bw_acct"); /* change bandwidth statistics accounting */ 
    putSystemId(3008, "net_bt_stack"); /* bluetooth: access config files */ 
    putSystemId(3009, "readproc"); /* Allow /proc read access */ 
    putSystemId(3010, "wakelock"); /* Allow system wakelock read/write access */ 

    /* The range 5000-5999 is also reserved for OEMs. */ 

    putSystemId(9997, "everybody"); /* shared between all apps in the same profile */ 
    putSystemId(9998, "misc"); /* access to misc storage */ 
    putSystemId(9999, "nobody"); 
    } 

    private static void putSystemId(int id, String name) { 
    // Check if the uid exists before adding it so we don't add unsupported ids. 
    if (android.os.Process.getUidForName(name) != id) { 
     // Not valid on this system. Most likely due to a lower API. 
     return; 
    } 
    SYSTEM_IDS.put(id, name); 
    } 

    /** 
    * @return An array of system UIDs 
    */ 
    public static SparseArray<String> getSystemIds() { 
    return SYSTEM_IDS; 
    } 

    /** 
    * Returns the UID/GID name assigned to a particular id, or {@code null} if there is none. 
    * 
    * @param id 
    *  The UID/GID of a process or file 
    * @return the name of the UID/GID or {@code null} if the id is unrecognized. 
    */ 
    public static String getNameForId(int id) { 
    String name = SYSTEM_IDS.get(id); 
    if (name == null) { 
     if (id >= AID_SHARED_GID_START && id <= AID_SHARED_GID_END) { 
     name = String.format(Locale.ENGLISH, "all_a%d", id - AID_SHARED_GID_START); 
     } else { 
     int appId = id - AID_APP; 
     int userId = 0; 
     // loop until we get the correct user id. 
     // 100000 is the offset for each user. 
     while (appId > AID_USER) { 
      appId -= AID_USER; 
      userId++; 
     } 
     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) { 
      // u{user_id}_a{app_id} is used on API 17+ for multiple user account support. 
      name = String.format(Locale.ENGLISH, "u%d_a%d", userId, appId); 
     } else { 
      // app_{app_id} is used below API 17. 
      name = String.format(Locale.ENGLISH, "app_%d", appId); 
     } 
     } 
    } 
    return name; 
    } 

    private AndroidFilesystemConfig() { 
    throw new AssertionError("no instances"); 
    } 

} 

---

utilizzando la riflessione:

Ispirato dalla risposta di odexide, ecco alcune davvero brutto riflessione Non consiglierei usando che otterrà l'UID Nome/GID da getpwuid(uid_t):

public static String getNameForUid(int id) { 
    try { 
    Class<?> clazz = Class.forName("libcore.io.Libcore"); 
    Field field = clazz.getDeclaredField("os"); 
    if (!field.isAccessible()) { 
     field.setAccessible(true); 
    } 
    Object os = field.get(null); 
    if (os != null) { 
     Method getpwuid = os.getClass().getMethod("getpwuid", int.class); 
     if (getpwuid != null) { 
     if (!getpwuid.isAccessible()) { 
      getpwuid.setAccessible(true); 
     } 
     Object passwd = getpwuid.invoke(os, id); 
     if (passwd != null) { 
      Field pw_name = passwd.getClass().getDeclaredField("pw_name"); 
      if (!pw_name.isAccessible()) { 
      pw_name.setAccessible(true); 
      } 
      return (String) pw_name.get(passwd); 
     } 
     } 
    } 
    } catch (Exception ignored) { 
    } 
    return null; 
}