build: verify aapt2 ABI before packaging in jniLibs

Author: itsaky

build-logic/ide/src/main/java/com/itsaky/androidide/plugins/tasks/SetupAapt2Task.kt

@@ -19,6 +19,7 @@ package com.itsaky.androidide.plugins.tasks
 
 import FDroidConfig
 import com.itsaky.androidide.plugins.util.DownloadUtils
+import com.itsaky.androidide.plugins.util.ELFUtils
 import isFDroidBuild
 import org.gradle.api.DefaultTask
 import org.gradle.api.file.DirectoryProperty
@@ -72,6 +73,7 @@ abstract class SetupAapt2Task : DefaultTask() {
 
       logger.info("Copying $aapt2 to $file")
       aapt2.copyTo(file, overwrite = true)
+      assertAapt2Arch(file, ELFUtils.ElfAbi.forName(arch)!!)
       return
     }
 
@@ -83,6 +85,15 @@ abstract class SetupAapt2Task : DefaultTask() {
 
       val remoteUrl = AAPT2_DOWNLOAD_URL.format(DEFAULT_VERSION, arch)
       DownloadUtils.doDownload(file, remoteUrl, checksum, logger)
+      logger.lifecycle("aapt2 arch: $arch")
+      assertAapt2Arch(file, ELFUtils.ElfAbi.forName(arch)!!)
+    }
+  }
+
+  private fun assertAapt2Arch(aapt2: File, elfAbi: ELFUtils.ElfAbi) {
+    val fileAbi = ELFUtils.getElfAbi(aapt2)
+    check(fileAbi == elfAbi) {
+      "Mismatched ABI for aapt2 binary. Required $elfAbi but found $fileAbi"
     }
   }
 }

build-logic/ide/src/main/java/com/itsaky/androidide/plugins/util/ELFUtils.kt

@@ -0,0 +1,130 @@
+/*
+ *  This file is part of AndroidIDE.
+ *
+ *  AndroidIDE is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  AndroidIDE is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *   along with AndroidIDE.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.itsaky.androidide.plugins.util
+
+import java.io.File
+import java.io.InputStream
+
+/**
+ * Utility methods for working with ELF binaries.
+ *
+ * @author Akash Yadav
+ * @see <a href="https://en.wikipedia.org/wiki/Executable_and_Linkable_Format">Executable and Linkable Format</a>
+ */
+object ELFUtils {
+
+  /**
+   * The magic number of an ELF binary.
+   */
+  const val ELF_MAGIC_NUMBER: Int = 0x7F454C46
+
+  /**
+   * 4-byte magic number of an ELF binary.
+   */
+  val ELF_MAGIC_NUMBER_ARR = byteArrayOf(0x7F, 0x45, 0x4C, 0x46)
+
+  /**
+   * `EI_OSABI` of an ELF binary. This enumeration only contains ABIs that are supported by AndroidIDE.
+   *
+   * @property abiName The name of CPU ABI.
+   * @property abi The number representing the ABI (`e_machine`).
+   */
+  enum class ElfAbi(val abiName: String, val abi: Byte) {
+    ARMV7("armeabi-v7a", 0x28),
+    AARCH64("arm64-v8a", 0xB7.toByte()),
+    X86_64("x86_64", 0x3E);
+
+    companion object {
+      fun forName(name: String) : ElfAbi? = ElfAbi.values().firstOrNull { it.abiName == name }
+      fun forAbi(abi: Byte) : ElfAbi? = ElfAbi.values().firstOrNull { it.abi == abi }
+    }
+  }
+
+  /**
+   * Check whether the data in given input stream corresponds to an ELF binary.
+   * This checks if the magic number (first 4 bytes) in the byte array is `0x7F454C46` i.e. `0x7F E L F`.
+   *
+   * @return `true` if the file is an ELF binary, `false` otherwise.
+   */
+  fun isElf(bytes: ByteArray) : Boolean {
+    if (bytes.size < 4) {
+      return false
+    }
+
+    for (i in 0..3) {
+      if (bytes[i] != ELF_MAGIC_NUMBER_ARR[i]) {
+        return false
+      }
+    }
+
+    return true
+  }
+
+  /**
+   * Check whether the data in given input stream corresponds to an ELF binary.
+   * This basically checks if the magic number in the input stream is `0x7F454C46` i.e. `0x7F E L F`.
+   *
+   * @return `true` if the file is an ELF binary, `false` otherwise.
+   */
+  fun isElf(inputStream: InputStream) : Boolean {
+    val bytes = ByteArray(4)
+    val read = inputStream.read(bytes)
+    if (read != 4) {
+      return false
+    }
+    return isElf(inputStream.readNBytes(4))
+  }
+
+  /**
+   * Check whether the given file is an ELF binary.
+   *
+   * @return `true` if the file is an ELF binary, `false` otherwise.
+   */
+  fun isElf(file: File): Boolean {
+    return file.inputStream().use { isElf(it) }
+  }
+
+  /**
+   * Get the [ElfAbi] for the given file.
+   *
+   * @return The [ElfAbi] for the file, or `null` if the file is not an ELF binary.
+   */
+  fun getElfAbi(file: File) : ElfAbi? {
+    return file.inputStream().use { getElfAbi(it) }
+  }
+
+  /**
+   * Get the [ElfAbi] from the given input stream.
+   *
+   * @return The [ElfAbi] for the input stream, or `null` if the input stream does not represent an ELF binary.
+   */
+  fun getElfAbi(inputStream: InputStream) : ElfAbi? {
+    val header = ByteArray(20)
+    if (inputStream.read(header) < 20) {
+      // incomplete data
+      return null
+    }
+
+    if (!isElf(header)) {
+      // not an elf binary
+      return null
+    }
+    
+    return ElfAbi.forAbi(header[18])
+  }
+}