apk-medit

Apk-medit is a memory search and patch tool for debuggable apk without root & ndk. It was created for mobile game security testing.

Motivation

Memory modification is the easiest way to cheat in games, it is one of the items to be checked in the security test. There are also cheat tools that can be used casually like GameGuardian. However, there were no tools available for non-root device and CUI. So I made it as a security testing tool.

Demo

This is a demo that uses apk-medit to clear a game that requires one million taps to clear.

Installation

Download the binary from GitHub Releases, please push the binary in /data/local/tmp/ on an android device.

$ adb push medit /data/local/tmp/medit
medit: 1 file pushed. 29.0 MB/s (3135769 bytes in 0.103s)

How to Build

You can build with make command. It requires a go compiler. After the build is complete, if adb is connected, it pushes the built binary in /data/local/tmp/ on an android device.

$ make
GOOS=linux GOARCH=arm64 GOARM=7 go build -o medit
/bin/sh -c "adb push medit /data/local/tmp/medit"
medit: 1 file pushed. 23.7 MB/s (3131205 bytes in 0.126s)

Usage

Use the run-as command to read files used by the target app, so apk-medit can only be used with apps that have the debuggable attribute enabled. To enable the debuggable attribute, open AndroidManifest.xml, add the following xml attribute in application xml node:

android:debuggable="true"

You can also use aktsk/apkutil to easily enable the debuggable attribute without editing AndroidManifest.xml, it is useful.

$ apkutil debuggable <target-apk-name>.apk

After running the run-as command, directory is automatically changed. So copy medit from /data/local/tmp/. Running medit launches an interactive prompt.

$ adb shell
$ pm list packages # to check <target-package-name>
$ run-as <target-package-name>
$ cp /data/local/tmp/medit ./medit
$ ./medit

You can also choose not to use ptrace when writing to memory. This avoids debugger detection by ptrace, but don't work on Android 10 or later due to SELinux.

$ ./medit -without-ptrace

Commands

Here are the commands available in an interactive prompt.

find

Search the specified integer on memory.

> find 999982
Search UTF-8 String...
Target Value: 999982([57 57 57 57 56 50])
Found: 0!
------------------------
Search Word...
parsing 999982: value out of range
------------------------
Search Double Word...
Target Value: 999982([46 66 15 0])
Found: 1!
Address: 0xe7021f70

You can also specify datatype such as string, word, dword, qword.

> find dword 999996
Search Double Word...
Target Value: 999996([60 66 15 0])
Found: 1!
Address: 0xe7021f70

filter

Filter previous search results that match the current search results.

> filter 993881
Check previous results of searching dword...
Target Value: 993881([89 42 15 0])
Found: 1!
Address: 0xe7021f70

patch

Write the specified value on the address found by search.

> patch 10
...
Successfully patched!

ps

Find the target process and if there is only one, specify it as the target. ps runs automatically on startup.

> ps
Package: jp.aktsk.tap1000000, PID: 4398
Target PID has been set to 4398.

attach

If target pid set by ps, attach to the target process, stop all processes in the app by ptrace.

> attach
Target PID: 4398
Attached TID: 4398
Attached TID: 4405
Attached TID: 4407
Attached TID: 4408
Attached TID: 4410
Attached TID: 4411
Attached TID: 4412
Attached TID: 4413
Attached TID: 4414
Attached TID: 4415
Attached TID: 4418
Attached TID: 4420
Attached TID: 4424
Attached TID: 4429
Attached TID: 4430
Attached TID: 4436
Attached TID: 4437
Attached TID: 4438
Attached TID: 4439
Attached TID: 4440
Attached TID: 4441
Attached TID: 4442

If target pid is not set, it can be specified on the command line.

> attach <pid>

detach

Detach from the attached process.

> detach
Detached TID: 4398
Detached TID: 4405
Detached TID: 4407
Detached TID: 4408
Detached TID: 4410
Detached TID: 4411
Detached TID: 4412
Detached TID: 4413
Detached TID: 4414
Detached TID: 4415
Detached TID: 4418
Detached TID: 4420
Detached TID: 4424
Detached TID: 4429
Detached TID: 4430
Detached TID: 4436
Detached TID: 4437
Detached TID: 4438
Detached TID: 4439
Detached TID: 4440
Detached TID: 4441
Detached TID: 4442

dump

Display memory dump like hexdump.

> dump 0xf0aee000 0xf0aee300
Address range: 0xf0aee000 - 0xf0aee300
----------------------------------------------
00000000  34 32 20 61 6e 73 77 65  72 20 28 74 6f 20 6c 69  |42 answer (to li|
00000010  66 65 20 74 68 65 20 75  6e 69 76 65 72 73 65 20  |fe the universe |
00000020  65 74 63 7c 33 29 0a 33  31 34 20 70 69 0a 31 30  |etc|3).314 pi.10|
00000030  30 33 20 61 75 64 69 74  64 20 28 61 76 63 7c 33  |03 auditd (avc|3|
00000040  29 0a 31 30 30 34 20 63  68 61 74 74 79 20 28 64  |).1004 chatty (d|
00000050  72 6f 70 70 65 64 7c 33  29 0a 31 30 30 35 20 74  |ropped|3).1005 t|
00000060  61 67 5f 64 65 66 20 28  74 61 67 7c 31 29 2c 28  |ag_def (tag|1),(|
00000070  6e 61 6d 65 7c 33 29 2c  28 66 6f 72 6d 61 74 7c  |name|3),(format||
00000080  33 29 0a 31 30 30 36 20  6c 69 62 6c 6f 67 20 28  |3).1006 liblog (|
00000090  64 72 6f 70 70 65 64 7c  31 29 0a 32 37 31 38 20  |dropped|1).2718 |
000000a0  65 0a 32 37 31 39 20 63  6f 6e 66 69 67 75 72 61  |e.2719 configura|
000000b0  74 69 6f 6e 5f 63 68 61  6e 67 65 64 20 28 63 6f  |tion_changed (co|
000000c0  6e 66 69 67 20 6d 61 73  6b 7c 31 7c 35 29 0a 32  |nfig mask|1|5).2|
000000d0  37 32 30 20 73 79 6e 63  20 28 69 64 7c 33 29 2c  |720 sync (id|3),|
000000e0  28 65 76 65 6e 74 7c 31  7c 35 29 2c 28 73 6f 75  |(event|1|5),(sou|
000000f0  72 63 65 7c 31 7c 35 29  2c 28 61 63 63 6f 75 6e  |rce|1|5),(accoun|

exit

To exit medit, use the exit command or Ctrl-D.

> exit
Bye!

Test

You can run test codes with make command.

$ make test

License

MIT License