put all the dex swapping & resigning shenanigans in a function

apk_frauder/.gitignore

@@ -2,3 +2,4 @@
 *.zip
 *.dex
 *.idsig
+*.jks

apk_frauder/Cargo.toml

@@ -8,3 +8,4 @@ edition = "2021"
 [dependencies]
 androscalpel_serializer = { version = "0.1.0", path = "../androscalpel_serializer" }
 flate2 = { version = "1.0.28", features = ["rust_backend"] }
+rand = "0.8.5"

apk_frauder/src/lib.rs

@@ -1,4 +1,10 @@
 use androscalpel_serializer::Serializable;
+use std::env;
+use std::fs;
+use std::fs::File;
+use std::io::{Read, Seek};
+use std::path::Path;
+use std::process::Command;
 
 pub mod apk_signing_block;
 pub mod compression;
@@ -132,3 +138,87 @@ impl FileInfo {
         }
     }
 }
+
+/// Replace the dex files a an apk an resigned the apk.
+///
+/// # Warning
+///
+/// For now, only jks keystore are allowed.
+///
+/// The `zipalign` and `apksigner` args allow to use a specific version of the
+/// tools instead of the one in the PATH (if it even exist)
+pub fn replace_dex(
+    apk: impl AsRef<Path>,
+    dst: impl AsRef<Path>,
+    dexfiles: &mut [impl Read + Seek],
+    keystore: impl AsRef<Path>, // TODO enum for handling p11 and generating a random cert
+    // `keytool -genkey -v -keystore KEYSTORE.jks -keyalg RSA -keysize
+    // 2048 -validity 10000 -alias ALIAS`
+    zipalign: Option<impl AsRef<Path>>,
+    apksigner: Option<impl AsRef<Path>>,
+) {
+    let zipalign = if let Some(path) = &zipalign {
+        path.as_ref().as_os_str()
+    } else {
+        "zipalign".as_ref()
+    };
+    let apksigner = if let Some(path) = &apksigner {
+        path.as_ref().as_os_str()
+    } else {
+        "apksigner".as_ref()
+    };
+    let tmp_dir = env::temp_dir().join(format!("apk_frauder_{:x}", rand::random::<u128>()));
+    let unaligned_path = tmp_dir.join("stripped.apk");
+    let aligned_path = tmp_dir.join("aligned.apk");
+    fs::create_dir_all(&tmp_dir).expect("Failed to create temporary directory");
+
+    let file = File::open(apk).expect("failed to open file");
+    let mut apk = ZipFileReader::new(file);
+    let file = File::create(&unaligned_path).expect("failed to create file");
+    let mut apk_out = ZipFileWriter::new(file, apk.zip64_end_of_central_directory.clone());
+
+    let mut file_info_ref = (*apk
+        .get_classes_file_info()
+        .first()
+        .expect("No dex file found in apk"))
+    .clone();
+
+    apk.unlink_signature_files();
+    apk.unlink_bytecode_files();
+    for f in apk.files.clone() {
+        apk_out.insert_file_from_zip(f, &mut apk);
+    }
+    for (i, mut dex) in dexfiles.iter_mut().enumerate() {
+        if i == 0 {
+            file_info_ref.set_name("classes.dex");
+        } else {
+            file_info_ref.set_name(&format!("classes{}.dex", i + 1));
+        }
+        apk_out.insert_file(
+            &mut dex,
+            file_info_ref.header.clone(),
+            Some(file_info_ref.local_header.clone()),
+        );
+    }
+    apk_out.write_central_directory();
+    // TODO: we can probably do that ourself an spare ourself the trouble of finding zipalign
+    Command::new(zipalign)
+        .arg("-v")
+        .arg("-p")
+        .arg("4")
+        .arg(unaligned_path.as_os_str())
+        .arg(aligned_path.as_os_str())
+        .status()
+        .unwrap();
+
+    Command::new(apksigner)
+        .arg("sign")
+        .arg("--ks")
+        .arg(keystore.as_ref().as_os_str())
+        .arg("--out")
+        .arg(dst.as_ref().as_os_str())
+        .arg(aligned_path.as_os_str())
+        .status()
+        .unwrap();
+    fs::remove_dir_all(tmp_dir).expect("Failled to remove tmp dir");
+}

apk_frauder/src/main.rs

@@ -1,78 +1,19 @@
-use apk_frauder::ZipFileReader;
-use apk_frauder::ZipFileWriter;
+use std::env;
 use std::fs::File;
 
-use std::process::Command;
-
 fn main() {
-    // Remove previous generation
-    println!("Remove files from previous run");
-    Command::new("rm").arg("app-striped.apk").status().unwrap();
-    Command::new("rm")
-        .arg("app-instrumented.apk")
-        .status()
-        .unwrap();
-    Command::new("rm")
-        .arg("app-instrumented-signed.apk")
-        .status()
-        .unwrap();
-    Command::new("rm")
-        .arg("app-instrumented-aligned.apk")
-        .status()
-        .unwrap();
-
-    println!("Read the headers of the existing dex file and strip the apk signature and dex files");
-    let file = File::open("app-release.apk").expect("failed to open file");
-    let mut apk = ZipFileReader::new(file);
-
-    let mut file_info_ref = (*apk.get_classes_file_info().first().unwrap()).clone();
-
-    apk.unlink_signature_files();
-    apk.unlink_bytecode_files();
-
-    let out_file = File::create("app-striped.apk").expect("failed to create file");
-    let mut apk_out = ZipFileWriter::new(out_file, apk.zip64_end_of_central_directory.clone());
-    for f in apk.files.clone() {
-        apk_out.insert_file_from_zip(f, &mut apk);
-    }
-    apk_out.write_central_directory();
-
-    println!("Insert the dex file to the stripped apk with the header of the original dex file");
-    let file = File::open("app-striped.apk").expect("failed to open file");
-    let mut bytecodes = File::open("classes.dex").expect("failed to open file");
-    let mut apk = ZipFileReader::new(file);
-    let out_file = File::create("app-instrumented.apk").expect("failed to create file");
-    let mut apk_out = ZipFileWriter::new(out_file, apk.zip64_end_of_central_directory.clone());
-    for f in apk.files.clone() {
-        apk_out.insert_file_from_zip(f, &mut apk);
-    }
-    file_info_ref.set_name("classes.dex");
-    apk_out.insert_file(
-        &mut bytecodes,
-        file_info_ref.header,
-        Some(file_info_ref.local_header),
+    apk_frauder::replace_dex(
+        "app-release.apk",
+        "app-instrumented.apk",
+        &mut [File::open("classes.dex").expect("failed to open file")],
+        "my-release-key.jks",
+        Some(&format!(
+            "{}/Android/Sdk/build-tools/34.0.0/zipalign",
+            env::var("HOME").expect("$HOME not set")
+        )),
+        Some(&format!(
+            "{}/Android/Sdk/build-tools/34.0.0/apksigner",
+            env::var("HOME").expect("$HOME not set")
+        )),
     );
-    apk_out.write_central_directory();
-
-    println!("Align the apk");
-    // This could probably be performed by ourself
-    Command::new("/home/histausse/Android/Sdk/build-tools/34.0.0/zipalign")
-        .arg("-v")
-        .arg("-p")
-        .arg("4")
-        .arg("app-instrumented.apk")
-        .arg("app-instrumented-aligned.apk")
-        .status()
-        .unwrap();
-
-    println!("Sign the apk");
-    Command::new("/home/histausse/Android/Sdk/build-tools/34.0.0/apksigner")
-        .arg("sign")
-        .arg("--ks")
-        .arg("/home/histausse/AndroidStudioProjects/TestApplication/my-release-key.jks")
-        .arg("--out")
-        .arg("app-instrumented-signed.apk")
-        .arg("app-instrumented-aligned.apk")
-        .status()
-        .unwrap();
 }