Magisk/buildSrc/src/main/java/Codegen.kt

import java.io.ByteArrayOutputStream
import java.io.File
import java.io.InputStream
import java.io.PrintStream
import java.security.SecureRandom
import java.util.*
import javax.crypto.Cipher
import javax.crypto.CipherOutputStream
import javax.crypto.spec.IvParameterSpec
import javax.crypto.spec.SecretKeySpec
import kotlin.random.asKotlinRandom

// Set non-zero value here to fix the random seed for reproducible builds
// CI builds are always reproducible
val RAND_SEED = if (System.getenv("CI") != null) 42 else 0
private lateinit var RANDOM: Random
private val kRANDOM get() = RANDOM.asKotlinRandom()

private val c1 = mutableListOf<String>()
private val c2 = mutableListOf<String>()
private val c3 = mutableListOf<String>()

fun initRandom(dict: File) {
    RANDOM = if (RAND_SEED != 0) Random(RAND_SEED.toLong()) else SecureRandom()
    c1.clear()
    c2.clear()
    c3.clear()
    for (a in chain('a'..'z', 'A'..'Z')) {
        if (a != 'a' && a != 'A') {
            c1.add("$a")
        }
        for (b in chain('a'..'z', 'A'..'Z', '0'..'9')) {
            c2.add("$a$b")
            for (c in chain('a'..'z', 'A'..'Z', '0'..'9')) {
                c3.add("$a$b$c")
            }
        }
    }
    c1.shuffle(RANDOM)
    c2.shuffle(RANDOM)
    c3.shuffle(RANDOM)
    PrintStream(dict).use {
        for (c in chain(c1, c2, c3)) {
            it.println(c)
        }
    }
}

private fun <T> chain(vararg iters: Iterable<T>) = sequence {
    iters.forEach { it.forEach { v -> yield(v) } }
}

private fun PrintStream.byteField(name: String, bytes: ByteArray) {
    println("public static byte[] $name() {")
    print("byte[] buf = {")
    print(bytes.joinToString(",") { it.toString() })
    println("};")
    println("return buf;")
    println("}")
}

fun genKeyData(keysDir: File, outSrc: File) {
    outSrc.parentFile.mkdirs()
    PrintStream(outSrc).use {
        it.println("package com.topjohnwu.magisk.signing;")
        it.println("public final class KeyData {")

        it.byteField("verityCert", File(keysDir, "verity.x509.pem").readBytes())
        it.byteField("verityKey", File(keysDir, "verity.pk8").readBytes())

        it.println("}")
    }
}

fun genStubManifest(srcDir: File, outDir: File): String {
    outDir.deleteRecursively()

    fun String.ind(level: Int) = replaceIndentByMargin("    ".repeat(level))

    val cmpList = mutableListOf<String>()

    cmpList.add(
        """
        |<provider
        |    android:name="x.COMPONENT_PLACEHOLDER_0"
        |    android:authorities="${'$'}{applicationId}.provider"
        |    android:directBootAware="true"
        |    android:exported="false"
        |    android:grantUriPermissions="true" />""".ind(2)
    )

    cmpList.add(
        """
        |<receiver
        |    android:name="x.COMPONENT_PLACEHOLDER_1"
        |    android:exported="false">
        |    <intent-filter>
        |        <action android:name="android.intent.action.LOCALE_CHANGED" />
        |        <action android:name="android.intent.action.UID_REMOVED" />
        |        <action android:name="android.intent.action.MY_PACKAGE_REPLACED" />
        |    </intent-filter>
        |    <intent-filter>
        |        <action android:name="android.intent.action.PACKAGE_REPLACED" />
        |        <action android:name="android.intent.action.PACKAGE_FULLY_REMOVED" />
        |
        |        <data android:scheme="package" />
        |    </intent-filter>
        |</receiver>""".ind(2)
    )

    cmpList.add(
        """
        |<activity
        |    android:name="x.COMPONENT_PLACEHOLDER_2"
        |    android:exported="true">
        |    <intent-filter>
        |        <action android:name="android.intent.action.MAIN" />
        |        <category android:name="android.intent.category.LAUNCHER" />
        |    </intent-filter>
        |</activity>""".ind(2)
    )

    cmpList.add(
        """
        |<activity
        |    android:name="x.COMPONENT_PLACEHOLDER_3"
        |    android:directBootAware="true"
        |    android:exported="false"
        |    android:taskAffinity=""
        |    tools:ignore="AppLinkUrlError">
        |    <intent-filter>
        |        <action android:name="android.intent.action.VIEW"/>
        |        <category android:name="android.intent.category.DEFAULT"/>
        |    </intent-filter>
        |</activity>""".ind(2)
    )

    cmpList.add(
        """
        |<service
        |    android:name="x.COMPONENT_PLACEHOLDER_4"
        |    android:exported="false" />""".ind(2)
    )

    cmpList.add(
        """
        |<service
        |    android:name="x.COMPONENT_PLACEHOLDER_5"
        |    android:exported="false"
        |    android:permission="android.permission.BIND_JOB_SERVICE" />""".ind(2)
    )

    val classNameGenerator = sequence {
        fun notJavaKeyword(name: String) = when (name) {
            "do", "if", "for", "int", "new", "try" -> false
            else -> true
        }

        fun List<String>.process() = asSequence()
            .filter(::notJavaKeyword)
            // Distinct by lower case to support case insensitive file systems
            .distinctBy { it.lowercase() }

        val names = mutableListOf<String>()
        names.addAll(c1)
        names.addAll(c2.process().take(30))
        names.addAll(c3.process().take(30))
        names.shuffle(RANDOM)

        while (true) {
            val cls = StringBuilder()
            cls.append(names.random(kRANDOM))
            cls.append('.')
            cls.append(names.random(kRANDOM))
            // Old Android does not support capitalized package names
            // Check Android 7.0.0 PackageParser#buildClassName
            yield(cls.toString().replaceFirstChar { it.lowercase() })
        }
    }.distinct().iterator()

    fun genClass(type: String): String {
        val clzName = classNameGenerator.next()
        val (pkg, name) = clzName.split('.')
        val pkgDir = File(outDir, pkg)
        pkgDir.mkdirs()
        PrintStream(File(pkgDir, "$name.java")).use {
            it.println("package $pkg;")
            it.println("public class $name extends com.topjohnwu.magisk.$type {}")
        }
        return clzName
    }

    // Generate 2 non redirect-able classes
    val factory = genClass("DelegateComponentFactory")
    val app = genClass("DelegateApplication")

    // Shuffle the order of the components
    cmpList.shuffle(RANDOM)

    val xml = File(srcDir, "AndroidManifest.xml").readText()
    return xml.format(factory, app, cmpList.joinToString("\n\n"))
}

fun genEncryptedResources(res: InputStream, outDir: File) {
    val mainPkgDir = File(outDir, "com/topjohnwu/magisk")
    mainPkgDir.mkdirs()

    // Generate iv and key
    val iv = ByteArray(16)
    val key = ByteArray(32)
    RANDOM.nextBytes(iv)
    RANDOM.nextBytes(key)

    val cipher = Cipher.getInstance("AES/CBC/PKCS5Padding")
    cipher.init(Cipher.ENCRYPT_MODE, SecretKeySpec(key, "AES"), IvParameterSpec(iv))
    val bos = ByteArrayOutputStream()

    res.use {
        CipherOutputStream(bos, cipher).use { os ->
            it.transferTo(os)
        }
    }

    PrintStream(File(mainPkgDir, "Bytes.java")).use {
        it.println("package com.topjohnwu.magisk;")
        it.println("public final class Bytes {")

        it.byteField("key", key)
        it.byteField("iv", iv)
        it.byteField("res", bos.toByteArray())

        it.println("}")
    }
}