Add secure key storage

File uploads

.idea/deploymentTargetDropDown.xml

@@ -1,17 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="deploymentTargetDropDown">
-    <targetSelectedWithDropDown>
-      <Target>
-        <type value="QUICK_BOOT_TARGET" />
-        <deviceKey>
-          <Key>
-            <type value="VIRTUAL_DEVICE_PATH" />
-            <value value="$USER_HOME$/.android/avd/Pixel_3a_API_34_extension_level_7_arm64-v8a.avd" />
-          </Key>
-        </deviceKey>
-      </Target>
-    </targetSelectedWithDropDown>
-    <timeTargetWasSelectedWithDropDown value="2023-07-17T10:10:40.050367Z" />
-  </component>
-</project>

.idea/kotlinc.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="KotlinJpsPluginSettings">
-    <option name="version" value="1.7.20" />
+    <option name="version" value="1.9.10" />
   </component>
 </project>

app/build.gradle

@@ -1,6 +1,7 @@
 plugins {
     id 'com.android.application'
     id 'org.jetbrains.kotlin.android'
+    id 'org.jetbrains.kotlin.plugin.serialization'
 }
 
 android {
@@ -9,10 +10,10 @@ android {
 
     defaultConfig {
         applicationId "social.snort.app"
-        minSdk 24
+        minSdk 26
         targetSdk 33
-        versionCode 1
-        versionName "1.0.11"
+        versionCode 3
+        versionName "1.0.12"
 
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
         vectorDrawables {
@@ -50,6 +51,12 @@ dependencies {
     implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.3.1'
     implementation 'androidx.activity:activity-compose:1.5.1'
     implementation 'androidx.webkit:webkit:1.4.0'
+    implementation 'androidx.security:security-crypto-ktx:1.1.0-alpha03'
+    implementation 'org.jetbrains.kotlinx:kotlinx-serialization-json:1.5.1'
+
+    // Bitcoin secp256k1 bindings to Android
+    api 'fr.acinq.secp256k1:secp256k1-kmp-jni-android:0.10.1'
+
     testImplementation 'junit:junit:4.13.2'
     androidTestImplementation 'androidx.test.ext:junit:1.1.3'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'

app/src/main/AndroidManifest.xml

@@ -3,7 +3,8 @@
     xmlns:tools="http://schemas.android.com/tools">
 
     <application
-        android:allowBackup="true"
+        android:allowBackup="false"
+        android:name=".Snort"
         android:dataExtractionRules="@xml/data_extraction_rules"
         android:fullBackupContent="@xml/backup_rules"
         android:icon="@mipmap/ic_launcher"
@@ -11,6 +12,8 @@
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/AppTheme"
+        android:hardwareAccelerated="true"
+        android:usesCleartextTraffic="true"
         tools:targetApi="31">
         <activity
             android:name=".MainActivity"
@@ -24,4 +27,7 @@
     </application>
 
     <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.READ_CLIPBOARD" />
+    <uses-permission android:name="android.permission.WRITE_CLIPBOARD" />
+    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
 </manifest>

app/src/main/java/social/snort/app/EncryptedStorage.kt

@@ -0,0 +1,29 @@
+package social.snort.app
+
+import androidx.security.crypto.EncryptedSharedPreferences
+import androidx.security.crypto.MasterKey
+
+object EncryptedStorage {
+    private const val PREFERENCES_NAME = "secret_keeper"
+
+    fun prefsFileName(npub: String? = null): String {
+        return if (npub == null) PREFERENCES_NAME else "${PREFERENCES_NAME}_$npub"
+    }
+
+    fun preferences(npub: String? = null): EncryptedSharedPreferences {
+        val context = Snort.instance
+        val masterKey: MasterKey = MasterKey.Builder(context, MasterKey.DEFAULT_MASTER_KEY_ALIAS)
+            .setKeyScheme(MasterKey.KeyScheme.AES256_GCM)
+            .build()
+
+        val preferencesName = prefsFileName(npub)
+
+        return EncryptedSharedPreferences.create(
+            context,
+            preferencesName,
+            masterKey,
+            EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
+            EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
+        ) as EncryptedSharedPreferences
+    }
+}

app/src/main/java/social/snort/app/Event.kt

@@ -0,0 +1,19 @@
+package social.snort.app
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.JsonNames
+
+@Serializable
+data class Event(
+    val id: HexKey,
+    @SerialName("pubkey")
+    val pubKey: HexKey,
+    @SerialName("created_at")
+    val createdAt: Long,
+    val kind: Int,
+    val tags: List<List<String>>,
+    val content: String,
+
+    val sig: HexKey? = null
+)

app/src/main/java/social/snort/app/HexUtils.kt

@@ -0,0 +1,70 @@
+package social.snort.app
+
+/** Makes the distinction between String and Hex **/
+typealias HexKey = String
+
+fun ByteArray.toHexKey(): HexKey {
+    return Hex.encode(this)
+}
+
+fun HexKey.hexToByteArray(): ByteArray {
+    return Hex.decode(this)
+}
+
+object HexValidator {
+    private fun isHex2(c: Char): Boolean {
+        return when (c) {
+            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f', 'A', 'B', 'C', 'D', 'E', 'F', ' ' -> true
+            else -> false
+        }
+    }
+
+    fun isHex(hex: String?): Boolean {
+        if (hex == null) return false
+        var isHex = true
+        for (c in hex.toCharArray()) {
+            if (!isHex2(c)) {
+                isHex = false
+                break
+            }
+        }
+        return isHex
+    }
+}
+
+object Hex {
+    private val hexCode = arrayOf('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f')
+
+    // Faster if no calculations are needed.
+    private fun hexToBin(ch: Char): Int = when (ch) {
+        in '0'..'9' -> ch - '0'
+        in 'a'..'f' -> ch - 'a' + 10
+        in 'A'..'F' -> ch - 'A' + 10
+        else -> throw IllegalArgumentException("illegal hex character: $ch")
+    }
+
+    @JvmStatic
+    fun decode(hex: String): ByteArray {
+        // faster version of hex decoder
+        require(hex.length % 2 == 0)
+        val outSize = hex.length / 2
+        val out = ByteArray(outSize)
+
+        for (i in 0 until outSize) {
+            out[i] = (hexToBin(hex[2 * i]) * 16 + hexToBin(hex[2 * i + 1])).toByte()
+        }
+
+        return out
+    }
+
+    @JvmStatic
+    fun encode(input: ByteArray): String {
+        val len = input.size
+        val out = CharArray(len * 2)
+        for (i in 0 until len) {
+            out[i*2] = hexCode[(input[i].toInt() shr 4) and 0xF]
+            out[i*2+1] = hexCode[input[i].toInt() and 0xF]
+        }
+        return String(out)
+    }
+}

app/src/main/java/social/snort/app/MainActivity.kt

@@ -3,16 +3,22 @@ package social.snort.app
 import android.content.Intent
 import android.net.Uri
 import android.os.Bundle
+import android.webkit.PermissionRequest
+import android.webkit.ValueCallback
+import android.webkit.WebChromeClient
 import android.webkit.WebResourceRequest
 import android.webkit.WebResourceResponse
 import android.webkit.WebView
 import androidx.activity.ComponentActivity
+import androidx.activity.result.contract.ActivityResultContracts
 import androidx.annotation.RequiresApi
 import androidx.webkit.WebViewAssetLoader
 import androidx.webkit.WebViewClientCompat
 
 
 class MainActivity : ComponentActivity() {
+    private var getContentCallback: ValueCallback<Array<Uri>>? = null
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
 
@@ -22,11 +28,35 @@ class MainActivity : ComponentActivity() {
         webView.settings.domStorageEnabled = true
         webView.settings.javaScriptEnabled = true
         webView.settings.databaseEnabled = true;
+        val getContent =
+            registerForActivityResult(ActivityResultContracts.GetContent()) { uri: Uri? ->
+                if (uri != null) {
+                    getContentCallback!!.onReceiveValue(arrayOf(uri))
+                } else {
+                    getContentCallback!!.onReceiveValue(emptyArray())
+                }
+                getContentCallback = null
+            }
 
         val assetLoader = WebViewAssetLoader.Builder()
-            .addPathHandler("/", WebViewAssetLoader.AssetsPathHandler(this))
-            .build()
+            .addPathHandler("/", WebViewAssetLoader.AssetsPathHandler(this)).build()
         webView.webViewClient = LocalContentWebViewClient(assetLoader)
+        webView.addJavascriptInterface(Nip7Extension(), "nostr_os");
+        webView.webChromeClient = object : WebChromeClient() {
+            override fun onPermissionRequest(request: PermissionRequest) {
+                request.grant(request.resources)
+            }
+
+            override fun onShowFileChooser(
+                vw: WebView,
+                filePathCallback: ValueCallback<Array<Uri>>,
+                fileChooserParams: FileChooserParams
+            ): Boolean {
+                getContentCallback = filePathCallback
+                getContent.launch("*/*")
+                return true
+            }
+        }
         webView.loadUrl("https://appassets.androidplatform.net/")
     }
 }
@@ -35,8 +65,7 @@ private class LocalContentWebViewClient(private val assetLoader: WebViewAssetLoa
     WebViewClientCompat() {
     @RequiresApi(21)
     override fun shouldInterceptRequest(
-        view: WebView,
-        request: WebResourceRequest
+        view: WebView, request: WebResourceRequest
     ): WebResourceResponse? {
         // rewrite root url to index.html
         if (request.url.path.equals("/") && request.url.host.equals("appassets.androidplatform.net")) {
@@ -49,8 +78,12 @@ private class LocalContentWebViewClient(private val assetLoader: WebViewAssetLoa
         if (request.url.host.equals("appassets.androidplatform.net")) {
             return false
         }
-        val intent = Intent(Intent.ACTION_VIEW, request.url)
-        view.context.startActivity(intent)
+        try {
+            val intent = Intent(Intent.ACTION_VIEW, request.url)
+            view.context.startActivity(intent)
+        } catch (ex: Exception) {
+            // ignored
+        }
         return true
     }
 }

app/src/main/java/social/snort/app/Nip7Extension.kt

@@ -0,0 +1,117 @@
+package social.snort.app
+
+import android.webkit.JavascriptInterface
+import fr.acinq.secp256k1.Secp256k1
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.add
+import kotlinx.serialization.json.buildJsonArray
+import java.security.MessageDigest
+import java.security.SecureRandom
+import java.util.Base64
+import javax.crypto.Cipher
+import javax.crypto.spec.IvParameterSpec
+import javax.crypto.spec.SecretKeySpec
+
+class Nip7Extension {
+    private val secp256k1 = Secp256k1.get()
+    private val h02 = ByteArray(1) { 0x02 }
+    private val random = SecureRandom()
+
+    object PrefKeys {
+        const val PrivateKey = "private_key"
+    }
+
+    @JavascriptInterface
+    fun getPublicKey(): String {
+        val key = EncryptedStorage.preferences().getString(PrefKeys.PrivateKey, null)
+        if (key != null) {
+            return Hex.encode(
+                secp256k1.pubKeyCompress(secp256k1.pubkeyCreate(Hex.decode(key))).copyOfRange(1, 33)
+            )
+        }
+        throw error("Missing private key")
+    }
+
+    @JavascriptInterface
+    fun signEvent(ev: String): String {
+        val key = EncryptedStorage.preferences().getString(PrefKeys.PrivateKey, null)
+            ?: throw error("Missing private key")
+
+        val json = Json { ignoreUnknownKeys = true }
+        println(ev)
+        val evParsed = json.decodeFromString<Event>(ev)
+
+        val idArray = buildJsonArray {
+            add(0)
+            add(evParsed.pubKey)
+            add(evParsed.createdAt)
+            add(evParsed.kind)
+            add(buildJsonArray {
+                evParsed.tags.forEach { x -> add(buildJsonArray { x.forEach { y -> add(y) } }) }
+            })
+            add(evParsed.content)
+        }.toString()
+
+        println(idArray)
+        val evId = MessageDigest.getInstance("SHA-256").digest(idArray.encodeToByteArray())
+        var sig = Hex.encode(secp256k1.signSchnorr(evId, Hex.decode(key), null))
+
+        return json.encodeToString(
+            Event(
+                Hex.encode(evId),
+                evParsed.pubKey,
+                evParsed.createdAt,
+                evParsed.kind,
+                evParsed.tags,
+                evParsed.content,
+                sig
+            )
+        )
+    }
+
+    @JavascriptInterface
+    fun nip04_encrypt(msg: String, toKey: String): String {
+        val key = EncryptedStorage.preferences().getString(PrefKeys.PrivateKey, null)
+            ?: throw error("Missing private key")
+        val sharedSecret = getSharedSecretNIP04(Hex.decode(key), Hex.decode(toKey))
+        val iv = ByteArray(16)
+        random.nextBytes(iv)
+        val cipher = Cipher.getInstance("AES/CBC/PKCS5Padding")
+        cipher.init(Cipher.ENCRYPT_MODE, SecretKeySpec(sharedSecret, "AES"), IvParameterSpec(iv))
+        val ivBase64 = Base64.getEncoder().encodeToString(iv)
+        val encryptedMsg = cipher.doFinal(msg.toByteArray())
+        val encryptedMsgBase64 = Base64.getEncoder().encodeToString(encryptedMsg)
+        return "$encryptedMsgBase64?iv=$ivBase64"
+    }
+
+    @JavascriptInterface
+    fun nip04_decrypt(msg: String, fromKey: String): String {
+        val key = EncryptedStorage.preferences().getString(PrefKeys.PrivateKey, null)
+            ?: throw error("Missing private key")
+        val sharedSecret = getSharedSecretNIP04(Hex.decode(key), Hex.decode(fromKey))
+
+        val msgSplit = msg.split("?iv=")
+        val cipherText = Base64.getDecoder().decode(msgSplit[0])
+        val iv = Base64.getDecoder().decode(msgSplit[1])
+
+        val cipher = Cipher.getInstance("AES/CBC/PKCS5Padding")
+        cipher.init(Cipher.DECRYPT_MODE, SecretKeySpec(sharedSecret, "AES"), IvParameterSpec(iv))
+        return String(cipher.doFinal(cipherText))
+    }
+
+    @JavascriptInterface
+    fun saveKey(key: String) {
+        EncryptedStorage.preferences().edit().apply {
+            putString(PrefKeys.PrivateKey, key)
+        }.commit()
+    }
+
+    /**
+     * @return 32B shared secret
+     */
+    private fun getSharedSecretNIP04(privateKey: ByteArray, pubKey: ByteArray): ByteArray {
+        return secp256k1.pubKeyTweakMul(h02 + pubKey, privateKey)
+            .copyOfRange(1, 33)
+    }
+}

app/src/main/java/social/snort/app/Snort.kt

@@ -0,0 +1,15 @@
+package social.snort.app
+
+import android.app.Application
+
+class Snort : Application() {
+    override fun onCreate() {
+        super.onCreate()
+        instance = this
+    }
+
+    companion object {
+        lateinit var instance: Snort
+            private set
+    }
+}

build.gradle

@@ -3,4 +3,5 @@ plugins {
     id 'com.android.application' version '8.0.2' apply false
     id 'com.android.library' version '8.0.2' apply false
     id 'org.jetbrains.kotlin.android' version '1.7.20' apply false
+    id 'org.jetbrains.kotlin.plugin.serialization' version '1.9.10'
 }