poc repackaging

apk_frauder/.gitignore

@@ -1,2 +1,4 @@
 *.apk
 *.zip
+*.dex
+*.idsig

apk_frauder/src/main.rs

@@ -1,76 +1,78 @@
-use apk_frauder::external_file_attributes;
-use apk_frauder::file_header::FileHeader;
 use apk_frauder::ZipFileReader;
 use apk_frauder::ZipFileWriter;
 use std::fs::File;
-use std::io::Cursor;
+
+use std::process::Command;
 
 fn main() {
-    //let file = File::open("app-release.apk").expect("failed to open file");
+    // Remove previous generation
-    //let file = File::open("tst_64.zip").expect("failed to open file");
+    println!("Remove files from previous run");
-    //let zip_file = ZipFileReader::new(file);
+    Command::new("rm").arg("app-striped.apk").status().unwrap();
-    /*
+    Command::new("rm")
-    //println!("{}", zip_file.get_file_names().join("\n"));
+        .arg("app-instrumented.apk")
-    for file in &zip_file.files {
+        .status()
-        println!("{}", file.get_name());
+        .unwrap();
-        println!("local:       {:?}", file.local_header.malformed_extra_field);
+    Command::new("rm")
-        println!("central dir: {:?}", file.header.malformed_extra_field);
+        .arg("app-instrumented-signed.apk")
-        println!();
+        .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!(
+    println!("Insert the dex file to the stripped apk with the header of the original dex file");
-        "uncompressed size: {}",
+    let file = File::open("app-striped.apk").expect("failed to open file");
-        zip_file.files[0].get_uncompressed_size()
+    let mut bytecodes = File::open("classes.dex").expect("failed to open file");
-    );
+    let mut apk = ZipFileReader::new(file);
-    println!(
+    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());
-        zip_file
+    for f in apk.files.clone() {
-            .get_jar_sig_files()
+        apk_out.insert_file_from_zip(f, &mut apk);
-            .iter()
-            .map(|f| f.get_name())
-            .collect::<Vec<_>>()
-            .join("\n")
-    );
-    if zip_file.is_signed_v2() {
-        println!("Signed >= v2");
-    } else {
-        println!("Not signed whith scheme >= v2");
     }
-    zip_file.check_holes();
+    file_info_ref.set_name("classes.dex");
-    */
+    apk_out.insert_file(
-    //println!("{:#?}", zip_file.get_file_info("classes.dex"));
+        &mut bytecodes,
-
+        file_info_ref.header,
-    /*
+        Some(file_info_ref.local_header),
-    let file = File::open("tst_64.zip").expect("failed to open file");
-    let out_file = File::create("tst_64.out.zip").expect("failed to create file");
-    let mut zip_file = ZipFileReader::new(file);
-    let mut out_file =
-        ZipFileWriter::new(out_file, zip_file.zip64_end_of_central_directory.clone());
-    for f in zip_file.files.clone() {
-        out_file.insert_file_from_zip(f, &mut zip_file);
-    }
-    out_file.write_central_directory();
-    */
-    //println!("{:#?}", zip_file.zip64_end_of_central_directory);
-    let out_file = File::create("test_write.zip").expect("failed to create file");
-    let mut out_file = ZipFileWriter::new(out_file, None);
-    out_file.insert_file(
-        &mut Cursor::new(b"plop\n"),
-        FileHeader::new_default("plop.txt"),
-        None,
-    );
-    out_file.insert_file(
-        &mut Cursor::new(b"Hello World !!!\n"),
-        FileHeader::new_default("plip.txt"),
-        None,
     );
+    apk_out.write_central_directory();
 
-    //let mut header_dir = FileHeader::new_default("dir");
+    println!("Align the apk");
-    //header_dir.set_file_type(external_file_attributes::DIR_FILE);
+    // This could probably be performed by ourself
-    //out_file.insert_file(&mut Cursor::new(b""), header_dir, None);
+    Command::new("/home/histausse/Android/Sdk/build-tools/34.0.0/zipalign")
-    let mut header_link = FileHeader::new_default("dir/link");
+        .arg("-v")
-    header_link.set_file_type(external_file_attributes::SYMBOLIC_LINK_FILE);
+        .arg("-p")
-    out_file.insert_file(&mut Cursor::new(b"../plop.txt"), header_link, None);
+        .arg("4")
+        .arg("app-instrumented.apk")
+        .arg("app-instrumented-aligned.apk")
+        .status()
+        .unwrap();
 
-    out_file.write_central_directory();
+    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();
 }

apk_frauder/src/zip_reader.rs

@@ -207,15 +207,7 @@ impl<T: Read + Seek> ZipFileReader<T> {
     pub fn get_jar_sig_files(&self) -> Vec<&FileInfo> {
         self.files
             .iter()
-            .filter(|file| {
+            .filter(|file| match_v1_signature_file(&file.get_name()))
-                let name = file.get_name();
-                let l = name.len();
-                (name == "META-INF/MANIFEST.MF")
-                    || (l >= 13 && &name[..9] == "META-INF/" && &name[l - 3..] == ".SF")
-                    || (l >= 14 && &name[..9] == "META-INF/" && &name[l - 4..] == ".DSA")
-                    || (l >= 14 && &name[..9] == "META-INF/" && &name[l - 4..] == ".RSA")
-                    || (l >= 14 && &name[..13] == "META-INF/SIG-")
-            })
             .collect()
     }
 
@@ -237,6 +229,24 @@ impl<T: Read + Seek> ZipFileReader<T> {
         self.apk_sign_block.is_some()
     }
 
+    /// Remove v1 signature files from the file index.
+    ///
+    /// This function does no modify the original file, only the index store
+    /// in the struct.
+    pub fn unlink_signature_files(&mut self) {
+        self.files
+            .retain(|file| !match_v1_signature_file(&file.get_name()));
+    }
+
+    /// Unlink bytecode files.
+    ///
+    /// This function does no modify the original file, only the index store
+    /// in the struct.
+    pub fn unlink_bytecode_files(&mut self) {
+        self.files
+            .retain(|file| !match_dexfile_name(&file.get_name()));
+    }
+
     pub fn check_holes(&self) {
         let mut files: Vec<&FileInfo> = self.files.iter().collect();
         files.sort_by_key(|f| f.get_offset_local_header());
@@ -262,7 +272,7 @@ impl<T: Read + Seek> ZipFileReader<T> {
                 );
             }
 
-            lst_offset += apk_sign_block.size() as u64;
+            lst_offset = self.get_cd_offset();
         }
         if self.get_cd_offset() != lst_offset {
             println!(
@@ -285,4 +295,37 @@ impl<T: Read + Seek> ZipFileReader<T> {
     pub fn get_file_info(&self, name: &str) -> Option<&FileInfo> {
         self.files.iter().find(|&file| file.get_name() == name)
     }
+
+    pub fn get_classes_file_info(&self) -> Vec<&FileInfo> {
+        self.files
+            .iter()
+            .filter(|&file| match_dexfile_name(&file.get_name()))
+            .collect()
+    }
+}
+
+// Not worth a regex
+/// Check if a file is a bytecode file (from its name)
+fn match_dexfile_name(name: &str) -> bool {
+    if name.len() < 11 {
+        return false;
+    }
+    if &name[0..7] != "classes" {
+        return false;
+    }
+    if &name[name.len() - 4..name.len()] != ".dex" {
+        return false;
+    }
+
+    name.len() == 11 || name[7..name.len() - 4].parse::<u32>().is_ok()
+}
+
+/// Check if a file is used to sign the APK with signature scheme v1.
+fn match_v1_signature_file(name: &str) -> bool {
+    let l = name.len();
+    (name == "META-INF/MANIFEST.MF")
+        || (l >= 13 && &name[..9] == "META-INF/" && &name[l - 3..] == ".SF")
+        || (l >= 14 && &name[..9] == "META-INF/" && &name[l - 4..] == ".DSA")
+        || (l >= 14 && &name[..9] == "META-INF/" && &name[l - 4..] == ".RSA")
+        || (l >= 14 && &name[..13] == "META-INF/SIG-")
 }