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Added: Add functions to UserUtils to get user name for user id from PackageManager and Libcore

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agnostic-apollo
2022-04-17 07:55:33 +05:00
parent bcd8f4c419
commit 69cc65c3ac
1 changed files with 143 additions and 0 deletions
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termux-shared/src/main/java/com/termux/shared/android/UserUtils.java Normal file
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package com.termux.shared.android;
import android.content.Context;
import android.content.pm.PackageManager;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import com.termux.shared.logger.Logger;
import com.termux.shared.reflection.ReflectionUtils;
import java.lang.reflect.Method;
public class UserUtils {
public static final String LOG_TAG = "UserUtils";
/**
* Get the user name for user id with a call to {@link #getNameForUidFromPackageManager(Context, int)}
* and if that fails, then a call to {@link #getNameForUidFromLibcore(int)}.
*
* @param context The {@link Context} for operations.
* @param uid The user id.
* @return Returns the user name if found, otherwise {@code null}.
*/
@Nullable
public static String getNameForUid(@NonNull Context context, int uid) {
String name = getNameForUidFromPackageManager(context, uid);
if (name == null)
name = getNameForUidFromLibcore(uid);
return name;
}
/**
* Get the user name for user id with a call to {@link PackageManager#getNameForUid(int)}.
*
* This will not return user names for non app user id like for root user 0, use {@link #getNameForUidFromLibcore(int)}
* to get those.
*
* https://cs.android.com/android/platform/superproject/+/android-12.0.0_r32:frameworks/base/core/java/android/content/pm/PackageManager.java;l=5556
* https://cs.android.com/android/platform/superproject/+/android-12.0.0_r32:frameworks/base/core/java/android/app/ApplicationPackageManager.java;l=1028
* https://cs.android.com/android/platform/superproject/+/android-12.0.0_r32:frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java;l=10293
*
* @param context The {@link Context} for operations.
* @param uid The user id.
* @return Returns the user name if found, otherwise {@code null}.
*/
@Nullable
public static String getNameForUidFromPackageManager(@NonNull Context context, int uid) {
if (uid < 0) return null;
try {
String name = context.getPackageManager().getNameForUid(uid);
if (name != null && name.endsWith(":" + uid))
name = name.replaceAll(":" + uid + "$", ""); // Remove ":<uid>" suffix
return name;
} catch (Exception e) {
Logger.logStackTraceWithMessage(LOG_TAG, "Failed to get name for uid \"" + uid + "\" from package manager", e);
return null;
}
}
/**
* Get the user name for user id with a call to `Libcore.os.getpwuid()`.
*
* This will return user names for non app user id like for root user 0 as well, but this call
* is expensive due to usage of reflection, and requires hidden API bypass, check
* {@link ReflectionUtils#bypassHiddenAPIReflectionRestrictions()} for details.
*
* `BlockGuardOs` implements the `Os` interface and its instance is stored in `Libcore` class static `os` field.
* The `getpwuid` method is implemented by `ForwardingOs`, which is the super class of `BlockGuardOs`.
* The `getpwuid` method returns `StructPasswd` object whose `pw_name` contains the user name for id.
*
* https://stackoverflow.com/a/28057167/14686958
* https://cs.android.com/android/platform/superproject/+/android-12.0.0_r32:libcore/luni/src/main/java/libcore/io/Libcore.java;l=39
* https://cs.android.com/android/platform/superproject/+/android-12.0.0_r32:libcore/luni/src/main/java/libcore/io/Os.java;l=279
* https://cs.android.com/android/platform/superproject/+/android-12.0.0_r32:libcore/luni/src/main/java/libcore/io/BlockGuardOs.java
* https://cs.android.com/android/platform/superproject/+/android-12.0.0_r32:libcore/luni/src/main/java/libcore/io/ForwardingOs.java;l=340
* https://cs.android.com/android/platform/superproject/+/android-12.0.0_r32:libcore/luni/src/main/java/android/system/StructPasswd.java
* https://cs.android.com/android/platform/superproject/+/android-12.0.0_r32:bionic/libc/bionic/grp_pwd.cpp;l=553
* https://cs.android.com/android/platform/superproject/+/android-12.0.0_r32:system/core/libcutils/include/private/android_filesystem_config.h;l=43
*
* @param uid The user id.
* @return Returns the user name if found, otherwise {@code null}.
*/
@Nullable
public static String getNameForUidFromLibcore(int uid) {
if (uid < 0) return null;
ReflectionUtils.bypassHiddenAPIReflectionRestrictions();
try {
String libcoreClassName = "libcore.io.Libcore";
Class<?> clazz = Class.forName(libcoreClassName);
Object os; // libcore.io.BlockGuardOs
try {
os = ReflectionUtils.invokeField(Class.forName(libcoreClassName), "os", null).value;
} catch (Exception e) {
// ClassCastException may be thrown
Logger.logStackTraceWithMessage(LOG_TAG, "Failed to get \"os\" field value for " + libcoreClassName + " class", e);
return null;
}
if (os == null) {
Logger.logError(LOG_TAG, "Failed to get BlockGuardOs class obj from Libcore");
return null;
}
clazz = os.getClass().getSuperclass(); // libcore.io.ForwardingOs
if (clazz == null) {
Logger.logError(LOG_TAG, "Failed to find super class ForwardingOs from object of class " + os.getClass().getName());
return null;
}
Object structPasswd; // android.system.StructPasswd
try {
Method getpwuidMethod = ReflectionUtils.getDeclaredMethod(clazz, "getpwuid", int.class);
if (getpwuidMethod == null) return null;
structPasswd = ReflectionUtils.invokeMethod(getpwuidMethod, os, uid).value;
} catch (Exception e) {
Logger.logStackTraceWithMessage(LOG_TAG, "Failed to invoke getpwuid() method of " + clazz.getName() + " class", e);
return null;
}
if (structPasswd == null) {
Logger.logError(LOG_TAG, "Failed to get StructPasswd obj from call to ForwardingOs.getpwuid()");
return null;
}
try {
clazz = structPasswd.getClass();
return (String) ReflectionUtils.invokeField(clazz, "pw_name", structPasswd).value;
} catch (Exception e) {
// ClassCastException may be thrown
Logger.logStackTraceWithMessage(LOG_TAG, "Failed to get \"pw_name\" field value for " + clazz.getName() + " class", e);
return null;
}
} catch (Exception e) {
Logger.logStackTraceWithMessage(LOG_TAG, "Failed to get name for uid \"" + uid + "\" from Libcore", e);
return null;
}
}
}