Initial commit

.gitignore

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+output/
+.idea/

README.MD

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+# Diversification
+
+Writer takes 16-byte 2K3DES master key as command line argument, derives from it 
+a new key based on UID of the tag, and then writes the new key to the tag. 
+If second argument is provided, then it's used as the current key. 
+If no second argument is provided, then the default key (BREAKMEIFYOUCAN!) is used.
+
+Reader takes master key and reads the whole card with derived key.
+
+This works only for Mifare Ultralight C tags.
+
+## Dependencies
+I use my [fork](https://github.com/graynk/freefare) of [fuzxxl/freefare](https://github.com/fuzxxl/freefare) 
+that supports key diversification and has some ad-hoc fixes to work with latest
+ version of [libfreefare](https://github.com/nfc-tools/libfreefare) (as well as some minor bug fixes).
+
+Obviously this means that building and installing [libnfc](https://github.com/nfc-tools/libnfc/) and 
+[libfreefare](https://github.com/nfc-tools/libfreefare) from 
+master is needed too. I'd have provided a specific version that's required, but 
+for some reason they have decided 
+to not bump the version for the past 4 years despite continuous changes to the API, 
+so expect things to be broken.
+
+## Usage
+```
+sh build.sh
+output/writer 00112233445566778899AABBCCDDEEFF FFEEDDCCBBAA99887766554433221100
+output/reader FFEEDDCCBBAA99887766554433221100

build.sh

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+#!/usr/bin/env bash
+go build -o output/reader reader/main.go
+go build -o output/writer writer/main.go

reader/main.go

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+package main
+
+import (
+ "C"
+ "encoding/hex"
+ "fmt"
+ "github.com/fuzxxl/nfc/2.0/nfc"
+ "github.com/graynk/freefare/0.3-diversify/freefare"
+ "log"
+ "os"
+)
+
+func main() {
+ args := os.Args
+ if len(args) == 1 {
+ log.Fatal("No master key provided")
+ }
+ devices, err := nfc.ListDevices()
+ if err != nil || len(devices) == 0 {
+ log.Fatalf("No devices found, %s", err)
+ }
+ device, err := nfc.Open(devices[0])
+ if err != nil {
+ log.Fatalf("Failed to open device, %s", err)
+ }
+ tags, err := freefare.GetTags(device)
+ if err != nil {
+ log.Fatalf("Failed to get tags, %s", err)
+ }
+ for _, tag := range tags {
+ err = tag.Connect()
+ if err != nil {
+ log.Fatalf("Can't connect, %s", err)
+ }
+ fmt.Println(tag)
+ fmt.Println(tag.UID())
+ if tag.Type() != freefare.UltralightC {
+ return
+ }
+
+ ultralightC := tag.(freefare.UltralightTag)
+ masterKeySlice, err := hex.DecodeString(args[1])
+ if err != nil || len(masterKeySlice) != 16 {
+ log.Fatalf("Failed to decode hex string to 16-byte key, %s", args[1])
+ }
+ var masterKeyBytes [16]byte
+ copy(masterKeyBytes[:], masterKeySlice)
+ masterKey := freefare.NewDESFire3DESKey(masterKeyBytes)
+ newKey, err := ultralightC.Diversify(*masterKey)
+ if err != nil {
+ log.Fatalf("Failed to diversify master key, %s", err)
+ }
+ err = ultralightC.Authenticate(*newKey)
+ if err != nil {
+ log.Fatal(err)
+ }
+ for page := byte(0); page < 44; page++ {
+ readBytes, err := ultralightC.ReadPage(page)
+ if err != nil {
+ log.Fatalf("Can't read, %s", err)
+ }
+ fmt.Printf("% X\n", readBytes)
+ }
+ err = tag.Disconnect()
+ if err != nil {
+ log.Fatal(err)
+ }
+ fmt.Println("Done")
+ }
+}

writer/main.go

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+package main
+
+import (
+ "encoding/hex"
+ "fmt"
+ "github.com/fuzxxl/nfc/2.0/nfc"
+ "github.com/graynk/freefare/0.3-diversify/freefare"
+ "log"
+ "os"
+)
+
+func main() {
+ args := os.Args
+ if len(args) == 1 {
+ log.Fatal("No master key provided")
+ }
+ devices, err := nfc.ListDevices()
+ if err != nil || len(devices) == 0 {
+ log.Fatalf("No devices found, %s", err)
+ }
+ device, err := nfc.Open(devices[0])
+ if err != nil {
+ log.Fatalf("Failed to open device, %s", err)
+ }
+ tags, err := freefare.GetTags(device)
+ if err != nil {
+ log.Fatalf("Failed to get tags, %s", err)
+ }
+ masterKeySlice, err := hex.DecodeString(args[1])
+ if err != nil || len(masterKeySlice) != 16 {
+ log.Fatalf("Failed to decode hex string to 16-byte key, %s", args[1])
+ }
+ var masterKeyBytes [16]byte
+ copy(masterKeyBytes[:], masterKeySlice)
+ masterKey := freefare.NewDESFire3DESKey(masterKeyBytes)
+
+ var defaultKeyBytes [16]byte
+ if len(args) > 2 {
+ defaultKeySlice, err := hex.DecodeString(args[2])
+ if err != nil || len(masterKeySlice) != 16 {
+ log.Fatalf("Failed to decode hex string to 16-byte key, %s", args[2])
+ }
+ copy(defaultKeyBytes[:], defaultKeySlice)
+ } else {
+ // BREAKMEIFYOUCAN!
+ defaultKeyBytes = [16]byte{0x49, 0x45, 0x4D, 0x4B, 0x41, 0x45, 0x52, 0x42, 0x21, 0x4E, 0x41, 0x43, 0x55, 0x4F, 0x59, 0x46}
+ }
+ defaultKey := freefare.NewDESFire3DESKey(defaultKeyBytes)
+ for _, tag := range tags {
+ err = tag.Connect()
+ if err != nil {
+ log.Fatalf("Failed to connect, %s", err)
+ }
+ fmt.Println(tag)
+ fmt.Println(tag.UID())
+ if tag.Type() != freefare.UltralightC {
+ log.Fatal("Not Ultralight C")
+ }
+ ultralightC := tag.(freefare.UltralightTag)
+ diversifiedKey, err := ultralightC.Diversify(*masterKey)
+ if err != nil {
+ log.Fatalf("Failed to diversify master key, %s", err)
+ }
+ err = ultralightC.SwapKeys(*defaultKey, *diversifiedKey)
+ if err != nil {
+ log.Fatalf("Failed to swap, %s", err)
+ }
+ err = ultralightC.Authenticate(*diversifiedKey)
+ if err != nil {
+ log.Fatalf("Failed to auth with diversified key, %s", err)
+ }
+ err = tag.Disconnect()
+ if err != nil {
+ log.Fatalf("Failed to disconnect, %s", err)
+ }
+ fmt.Println("Done")
+ }
+}