[APT-10658] Better EncryptedSharedPreferences Resilience #52
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,85 @@ | ||
| package com.scribd.armadillo.extensions | ||
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| import android.content.Context | ||
| import android.content.SharedPreferences | ||
| import android.security.keystore.KeyGenParameterSpec | ||
| import android.security.keystore.KeyProperties.BLOCK_MODE_GCM | ||
| import android.security.keystore.KeyProperties.ENCRYPTION_PADDING_NONE | ||
| import android.security.keystore.KeyProperties.PURPOSE_DECRYPT | ||
| import android.security.keystore.KeyProperties.PURPOSE_ENCRYPT | ||
| import android.util.Log | ||
| import androidx.security.crypto.EncryptedSharedPreferences | ||
| import androidx.security.crypto.MasterKeys | ||
| import com.scribd.armadillo.Constants.Keys.ANDROID_KEYSTORE_NAME | ||
| import java.io.File | ||
| import java.security.KeyStore | ||
|
|
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| fun SharedPreferences.deleteEncryptedSharedPreference(context: Context, filename: String, keystoreAlias: String) { | ||
| val tag = "DeletingSharedPrefs" | ||
| try { | ||
| //maybe deletes the shared preference file, this is not guaranteed to work. | ||
| val sharedPrefsFile = File( | ||
| (context.filesDir.getParent()?.plus("/shared_prefs/")) + filename + ".xml" | ||
|
There was a problem hiding this comment. I think it's worth adding a comment that this file is only a guess at the filepath, and may not actually exist depending on SDK version and OEM, and what happens if we do/don't delete it. |
||
| ) | ||
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| edit().clear().commit() | ||
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| if (sharedPrefsFile.exists()) { | ||
| val deleted = sharedPrefsFile.delete() | ||
| Log.d(tag, "resetStorage() Shared prefs file deleted: $deleted; path: ${sharedPrefsFile.absolutePath}") | ||
| } else { | ||
| Log.d(tag,"resetStorage() Shared prefs file non-existent; path: ${sharedPrefsFile.absolutePath}") | ||
| } | ||
|
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| val keyStore = KeyStore.getInstance(ANDROID_KEYSTORE_NAME) | ||
| keyStore.load(null) | ||
| keyStore.deleteEntry(keystoreAlias) | ||
| } catch (e: Exception) { | ||
| Log.e(tag, "Error occurred while trying to reset shared prefs", e) | ||
| } | ||
| } | ||
|
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| fun createEncryptedSharedPrefKeyStoreWithRetry(context: Context, fileName: String, keystoreAlias: String): SharedPreferences? { | ||
| val firstAttempt = createEncryptedSharedPrefsKeyStore(context = context, fileName = fileName, keystoreAlias = keystoreAlias) | ||
| return if(firstAttempt != null) { | ||
| firstAttempt | ||
| } else { | ||
| context.getSharedPreferences(fileName, Context.MODE_PRIVATE).deleteEncryptedSharedPreference( | ||
| context = context, | ||
| filename = fileName, | ||
| keystoreAlias = keystoreAlias | ||
| ) | ||
| createEncryptedSharedPrefsKeyStore(context = context, fileName = fileName, keystoreAlias = keystoreAlias) | ||
| } | ||
| } | ||
|
|
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| fun createEncryptedSharedPrefsKeyStore(context: Context, fileName: String, keystoreAlias: String) | ||
| : SharedPreferences? { | ||
| val keySpec = KeyGenParameterSpec.Builder(keystoreAlias, PURPOSE_ENCRYPT or PURPOSE_DECRYPT) | ||
| .setKeySize(256) | ||
| .setBlockModes(BLOCK_MODE_GCM) | ||
| .setEncryptionPaddings(ENCRYPTION_PADDING_NONE) | ||
| .build() | ||
|
|
||
| val keys = try { | ||
| MasterKeys.getOrCreate(keySpec) | ||
| } catch (ex: Exception) { | ||
| //clear corrupted store, contents will be lost | ||
| context.getSharedPreferences(fileName, Context.MODE_PRIVATE).deleteEncryptedSharedPreference( | ||
| context = context, | ||
| filename = fileName, | ||
| keystoreAlias = keystoreAlias ) | ||
| MasterKeys.getOrCreate(keySpec) | ||
| } | ||
| return try { | ||
| EncryptedSharedPreferences.create( | ||
| fileName, | ||
| keys, | ||
| context, | ||
| EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV, | ||
| EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM | ||
| ) | ||
| } catch(ex: Exception) { | ||
| null | ||
| } | ||
| } | ||
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Should we try to put it in legacy if secure doesn't exist?
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That would be failing insecure.