Modifying NfcNci.apk so that it doesn't care about Deodex. - Galaxy S 4 Developer Discussion [Developers-Only]

Just for the sake of transparency Here is a quick rundown of the process for everyone to see.
High level overview:
1. ) baksmali classes.dex from NfcNci.apk
2. ) Mod the resulting smali.
3. ) smali, and inject back into NfcNci.apk
Since this is the dev section I will focus on step 2 you can read about steps 1 and 3 elsewhere. For the sake of this example I will be working with the system dump from the original release of the gt-i9505g (S4 Google Edition) System Software.
What you are looking for is this function contained in the NfcIntegrityChecker class:
Code:
.method public checkIntegrity(Ljava/lang/String;)Z
If we track back the exception error message that comes up in the debug log ("Client module is tampered"), you will see that the text is contained in the NfcService class within the function ".method public enforceNfcIntegrity()V"
Code:
.method public enforceNfcIntegrity()V
.locals 3
.prologue
.line 470
iget-object v1, p0, Lcom/android/nfc/NfcService;->mIntegrityChecker:Lcom/android/nfc/NfcIntegrityChecker;
monitor-enter v1
.line 471
:try_start_0
iget-object v0, p0, Lcom/android/nfc/NfcService;->mIntegrityChecker:Lcom/android/nfc/NfcIntegrityChecker;
invoke-virtual {v0}, Lcom/android/nfc/NfcIntegrityChecker;->getStatus()I
move-result v0
const/4 v2, 0x3
if-ne v0, v2, :cond_0
.line 472
new-instance v0, Ljava/lang/SecurityException;
const-string v2, "NfcIntegrityChecker is not on the proper status"
invoke-direct {v0, v2}, Ljava/lang/SecurityException;-><init>(Ljava/lang/String;)V
throw v0
.line 480
:catchall_0
move-exception v0
monitor-exit v1
:try_end_0
.catchall {:try_start_0 .. :try_end_0} :catchall_0
throw v0
.line 475
:cond_0
:try_start_1
iget-object v0, p0, Lcom/android/nfc/NfcService;->mIntegrityChecker:Lcom/android/nfc/NfcIntegrityChecker;
invoke-virtual {v0}, Lcom/android/nfc/NfcIntegrityChecker;->getStatus()I
move-result v0
const/4 v2, 0x2
if-eq v0, v2, :cond_1
iget-object v0, p0, Lcom/android/nfc/NfcService;->mIntegrityChecker:Lcom/android/nfc/NfcIntegrityChecker;
const-string v2, "client"
invoke-virtual {v0, v2}, Lcom/android/nfc/NfcIntegrityChecker;->checkIntegrity(Ljava/lang/String;)Z
move-result v0
if-eqz v0, :cond_1
iget-object v0, p0, Lcom/android/nfc/NfcService;->mIntegrityChecker:Lcom/android/nfc/NfcIntegrityChecker;
const-string v2, "clientlib"
invoke-virtual {v0, v2}, Lcom/android/nfc/NfcIntegrityChecker;->checkIntegrity(Ljava/lang/String;)Z
move-result v0
if-nez v0, :cond_2
.line 478
:cond_1
new-instance v0, Ljava/lang/SecurityException;
const-string v2, "Client module is tampered"
invoke-direct {v0, v2}, Ljava/lang/SecurityException;-><init>(Ljava/lang/String;)V
throw v0
.line 480
:cond_2
monitor-exit v1
:try_end_1
.catchall {:try_start_1 .. :try_end_1} :catchall_0
.line 481
return-void
.end method
If we follow the flow of the application we see that the code for this failure is only reached if the function call to
Code:
checkIntegrity(Ljava/lang/String;)Z
returns false, or the status is not properly set. (the 'Z' at the end means it returns a boolean).
There are two ways to handle this. We can either patch out the call to checkIntegrity entirely (jump over it, or literally remove the calls), or we can modify the checkIntegrity function so that it always returns true.
So, let's look at the checkIntegrity function:
Code:
.method public checkIntegrity(Ljava/lang/String;)Z
.locals 11
.parameter "type"
.prologue
const/4 v10, 0x2
const/4 v9, 0x1
const/4 v8, 0x0
.line 293
iget-object v5, p0, Lcom/android/nfc/NfcIntegrityChecker;->mModuleMap:Ljava/util/HashMap;
invoke-virtual {v5, p1}, Ljava/util/HashMap;->get(Ljava/lang/Object;)Ljava/lang/Object;
move-result-object v2
check-cast v2, Ljava/util/ArrayList;
.line 294
.local v2, modules:Ljava/util/ArrayList;,"Ljava/util/ArrayList<[Ljava/lang/String;>;"
const/4 v1, 0x0
.line 295
.local v1, module:[Ljava/lang/String;
const/4 v3, 0x1
.line 296
.local v3, ret:Z
invoke-virtual {v2}, Ljava/util/ArrayList;->size()I
move-result v4
.line 298
.local v4, size:I
const/4 v0, 0x0
.local v0, i:I
:goto_0
if-ge v0, v4, :cond_2
.line 299
invoke-virtual {v2, v0}, Ljava/util/ArrayList;->get(I)Ljava/lang/Object;
move-result-object v1
.end local v1 #module:[Ljava/lang/String;
check-cast v1, [Ljava/lang/String;
.line 301
.restart local v1 #module:[Ljava/lang/String;
if-eqz v1, :cond_0
array-length v5, v1
if-eq v5, v10, :cond_4
.line 302
:cond_0
sget-boolean v5, Lcom/android/nfc/NfcIntegrityChecker;->DBG:Z
if-eqz v5, :cond_1
const-string v5, "NfcIntegrityChecker"
const-string v6, "checkIntegrity module format error"
invoke-static {v5, v6}, Landroid/util/Log;->e(Ljava/lang/String;Ljava/lang/String;)I
.line 303
:cond_1
const/4 v3, 0x0
.line 314
:cond_2
:goto_1
if-nez v3, :cond_3
iput v10, p0, Lcom/android/nfc/NfcIntegrityChecker;->mStatus:I
.line 316
:cond_3
return v3
.line 307
:cond_4
aget-object v5, v1, v8
aget-object v6, v1, v9
invoke-direct {p0, v5, v6}, Lcom/android/nfc/NfcIntegrityChecker;->checkModuleIntegrity(Ljava/lang/String;Ljava/lang/String;)Z
move-result v5
if-nez v5, :cond_6
.line 308
sget-boolean v5, Lcom/android/nfc/NfcIntegrityChecker;->DBG:Z
if-eqz v5, :cond_5
const-string v5, "NfcIntegrityChecker"
new-instance v6, Ljava/lang/StringBuilder;
invoke-direct {v6}, Ljava/lang/StringBuilder;-><init>()V
const-string v7, "checkModuleIntegrity "
invoke-virtual {v6, v7}, Ljava/lang/StringBuilder;->append(Ljava/lang/String;)Ljava/lang/StringBuilder;
move-result-object v6
aget-object v7, v1, v8
invoke-virtual {v6, v7}, Ljava/lang/StringBuilder;->append(Ljava/lang/String;)Ljava/lang/StringBuilder;
move-result-object v6
const-string v7, " tampered : "
invoke-virtual {v6, v7}, Ljava/lang/StringBuilder;->append(Ljava/lang/String;)Ljava/lang/StringBuilder;
move-result-object v6
aget-object v7, v1, v9
invoke-virtual {v6, v7}, Ljava/lang/StringBuilder;->append(Ljava/lang/String;)Ljava/lang/StringBuilder;
move-result-object v6
invoke-virtual {v6}, Ljava/lang/StringBuilder;->toString()Ljava/lang/String;
move-result-object v6
invoke-static {v5, v6}, Landroid/util/Log;->e(Ljava/lang/String;Ljava/lang/String;)I
.line 309
:cond_5
const/4 v3, 0x0
.line 310
goto :goto_1
.line 298
:cond_6
add-int/lit8 v0, v0, 0x1
goto :goto_0
.end method
There is only one return statement, so this should be a simple matter of setting our value, and calling return. In some cases there is code that your application needs to run in order to function, so usually a light touch is a good idea, but in this case all of the code is there to run various checks so we can skip most of it.
The easiest way would be to replace the whole function with this:
Code:
.method public checkIntegrity(Ljava/lang/String;)Z
.locals 2
.parameter "type"
.prologue
const/4 v0, 0x1
return v0
.end method
But that method never sat right with me (old school c++ cracking I guess), so I prefer something like this:
add a goto, and modify the constant here:
.line 303
:cond_1
:goto_666
const/4 v3, 0x1
then add the following line to the beginning of the function (after the .prologue)
goto :goto_666
We end up with something like this:
Code:
.method public checkIntegrity(Ljava/lang/String;)Z
.locals 11
.parameter "type"
.prologue
const/4 v10, 0x2
const/4 v9, 0x1
const/4 v8, 0x0
goto :goto_666
.line 293
iget-object v5, p0, Lcom/android/nfc/NfcIntegrityChecker;->mModuleMap:Ljava/util/HashMap;
invoke-virtual {v5, p1}, Ljava/util/HashMap;->get(Ljava/lang/Object;)Ljava/lang/Object;
move-result-object v2
check-cast v2, Ljava/util/ArrayList;
.line 294
.local v2, modules:Ljava/util/ArrayList;,"Ljava/util/ArrayList<[Ljava/lang/String;>;"
const/4 v1, 0x0
.line 295
.local v1, module:[Ljava/lang/String;
const/4 v3, 0x1
.line 296
.local v3, ret:Z
invoke-virtual {v2}, Ljava/util/ArrayList;->size()I
move-result v4
.line 298
.local v4, size:I
const/4 v0, 0x0
.local v0, i:I
:goto_0
if-ge v0, v4, :cond_2
.line 299
invoke-virtual {v2, v0}, Ljava/util/ArrayList;->get(I)Ljava/lang/Object;
move-result-object v1
.end local v1 #module:[Ljava/lang/String;
check-cast v1, [Ljava/lang/String;
.line 301
.restart local v1 #module:[Ljava/lang/String;
if-eqz v1, :cond_0
array-length v5, v1
if-eq v5, v10, :cond_4
.line 302
:cond_0
sget-boolean v5, Lcom/android/nfc/NfcIntegrityChecker;->DBG:Z
if-eqz v5, :cond_1
const-string v5, "NfcIntegrityChecker"
const-string v6, "checkIntegrity module format error"
invoke-static {v5, v6}, Landroid/util/Log;->e(Ljava/lang/String;Ljava/lang/String;)I
.line 303
:cond_1
:goto_666
const/4 v3, 0x1
.line 314
:cond_2
:goto_1
if-nez v3, :cond_3
iput v10, p0, Lcom/android/nfc/NfcIntegrityChecker;->mStatus:I
.line 316
:cond_3
return v3
.line 307
:cond_4
aget-object v5, v1, v8
aget-object v6, v1, v9
invoke-direct {p0, v5, v6}, Lcom/android/nfc/NfcIntegrityChecker;->checkModuleIntegrity(Ljava/lang/String;Ljava/lang/String;)Z
move-result v5
if-nez v5, :cond_6
.line 308
sget-boolean v5, Lcom/android/nfc/NfcIntegrityChecker;->DBG:Z
if-eqz v5, :cond_5
const-string v5, "NfcIntegrityChecker"
new-instance v6, Ljava/lang/StringBuilder;
invoke-direct {v6}, Ljava/lang/StringBuilder;-><init>()V
const-string v7, "checkModuleIntegrity "
invoke-virtual {v6, v7}, Ljava/lang/StringBuilder;->append(Ljava/lang/String;)Ljava/lang/StringBuilder;
move-result-object v6
aget-object v7, v1, v8
invoke-virtual {v6, v7}, Ljava/lang/StringBuilder;->append(Ljava/lang/String;)Ljava/lang/StringBuilder;
move-result-object v6
const-string v7, " tampered : "
invoke-virtual {v6, v7}, Ljava/lang/StringBuilder;->append(Ljava/lang/String;)Ljava/lang/StringBuilder;
move-result-object v6
aget-object v7, v1, v9
invoke-virtual {v6, v7}, Ljava/lang/StringBuilder;->append(Ljava/lang/String;)Ljava/lang/StringBuilder;
move-result-object v6
invoke-virtual {v6}, Ljava/lang/StringBuilder;->toString()Ljava/lang/String;
move-result-object v6
invoke-static {v5, v6}, Landroid/util/Log;->e(Ljava/lang/String;Ljava/lang/String;)I
.line 309
:cond_5
const/4 v3, 0x0
.line 310
goto :goto_1
.line 298
:cond_6
add-int/lit8 v0, v0, 0x1
goto :goto_0
.end method

---

confirmed working
thanks again!

---

This is great, thanks for your contribution!
So does the integrity check call only have to do with access to the secure element? Or does it also eliminate the need to spoof device model for compatibility purposes?

---

CPA Poke said:
This is great, thanks for your contribution!
So does the integrity check call only have to do with access to the secure element? Or does it also eliminate the need to spoof device model for compatibility purposes?
Click to expand...
Click to collapse
It is just for the secure element. You can modify the wallet apk to bypass things like root checking, model versions, and carrier checks as well. It looks like the xposed framework patch that has been floating around does some of this, but it doesn't seem to patch the calls to read the device properties for device ID and such.
In my testing, I was able to replace all of those calls in the wallet app with constant strings containing "valid" values. This would kind of suck to have to do for each update... Though It would be a simple enough matter to write a script to do this automagically for each update. (Baksmali, sed/awk to find and replace in the smali, and smali to classes.dex) or write an xposed module to watch for calls to read prop values originating from wallet.
Sent from my GT-I9505G

---

Fenny said:
It is just for the secure element. You can modify the wallet apk to bypass things like root checking, model versions, and carrier checks as well. It looks like the xposed framework patch that has been floating around does some of this, but it doesn't seem to patch the calls to read the device properties for device ID and such.
In my testing, I was able to replace all of those calls in the wallet app with constant strings containing "valid" values. This would kind of suck to have to do for each update... Though It would be a simple enough matter to write a script to do this automagically for each update. (Baksmali, sed/awk to find and replace in the smali, and smali to classes.dex) or write an xposed module to watch for calls to read prop values originating from wallet.
Sent from my GT-I9505G
Click to expand...
Click to collapse
I think that's what the existing Xposed Wallet hack modules do (watch for the read prop values originating from Wallet). But for whatever reason it won't intercept the calls on initial setup, which is why you have to actually change the build.prop prior to initially setting up Wallet.

---

Fenny said:
It is just for the secure element. You can modify the wallet apk to bypass things like root checking, model versions, and carrier checks as well. It looks like the xposed framework patch that has been floating around does some of this, but it doesn't seem to patch the calls to read the device properties for device ID and such.
In my testing, I was able to replace all of those calls in the wallet app with constant strings containing "valid" values. This would kind of suck to have to do for each update... Though It would be a simple enough matter to write a script to do this automagically for each update. (Baksmali, sed/awk to find and replace in the smali, and smali to classes.dex) or write an xposed module to watch for calls to read prop values originating from wallet.
Sent from my GT-I9505G
Click to expand...
Click to collapse
if you had time to add a how-to to bypass root checking, model version and carrier check, I'd update it every time. wouldn't be a problem and I'd be happy to help out.

---

mrvirginia said:
if you had time to add a how-to to bypass root checking, model version and carrier check, I'd update it every time. wouldn't be a problem and I'd be happy to help out.
Click to expand...
Click to collapse
Bypassing Root:
Look at the com.google.android.apps.wallet.security.EnvironmentProperty class in the constructor method.
We're looking for this segment containing SU_COMMAND_LOCATIONS:
Code:
.line 70
new-array v0, v4, [Ljava/lang/String;
const-string v1, "/system/bin/su"
aput-object v1, v0, v3
const-string v1, "/system/xbin/su"
aput-object v1, v0, v2
sput-object v0, Lcom/google/android/apps/wallet/security/EnvironmentProperty;->SU_COMMAND_LOCATIONS:[Ljava/lang/String;
Note: These variable names change (v3, v4, etc...), usually they will be the const/4 numbers defined at the beginning of the method. Just make sure you use the one that contains 0.
Change this line from v4 (which contains the number 2)
Code:
new-array v0, v4, [Ljava/lang/String;
to v3 (which contains the number 0)
Code:
new-array v0, v3, [Ljava/lang/String;
Then simply delete the following lines:
Code:
const-string v1, "/system/bin/su"
aput-object v1, v0, v3
const-string v1, "/system/xbin/su"
aput-object v1, v0, v2
This will Set the environment property SU_COMMAND_LOCATIONS as an empty string array which will cause the checkDevice function in Lcom/google/android/apps/wallet/security/EnvironmentProperty$1 to simply break out of it's for loop and return 0 (which is what we want).
Bypassing device/carrier restrictions:
Here is a quick script I whipped up to replace the build prop calls automagically.
Usage would be something like:
Baksmali the classes.dex in your apk:
java -jar baksmali.jar your.apk -o outdir
Run the script (below):
/path/to/pwnprop.sh outdir
Do whatever other changes to the outdir directory.
Then smali:
java -jar smali.jar outdir -o classes.dex
Finally, winzip, lol. (If you actually use winzip imma kill you.)
The script:
Save this as pwnprop.sh (or whatever you feel like) and chmod +x
Code:
#!/bin/bash
do_replace ()
{
case $3 in
# Replace these with whatever device you want to clone.
MODEL)
ours="Galaxy Nexus";;
BRAND)
ours="Google" ;;
BOARD)
ours=""tuna"
ID)
ours="JDQ39E" ;;
PRODUCT)
ours="yakju" ;;
DEVICE)
ours="yakju" ;;
FINGERPRINT)
ours="google/yakju/maguro:4.2.2/JDQ39/573038:user/release-keys" ;;
*)
echo "Replacement property not defined: "$3" in "$1
return ;;
esac
sed -i 's{sget-object '$2', Landroid/os/Build;->'$3':Ljava/lang/String;{const-string '$2', "'$ours'"{g' $1
echo sed -i 's{sget-object '$2', Landroid/os/Build;->'$3':Ljava/lang/String;{const-string '$2', "'$ours'"{g' $1
}
OIFS=$IFS; IFS=$'\n'
for line in `grep -ro "[v0-9]*, Landroid/os/Build;->[A-Z]*" $ | sed 's{, Landroid/os/Build;->{:{'`
do
IFS=':'
temparray=($line)
if [ ${#temparray[@]} -eq 3 ]
then
do_replace $line
fi
IFS=$OIFS
done

---

CPA Poke said:
I think that's what the existing Xposed Wallet hack modules do (watch for the read prop values originating from Wallet). But for whatever reason it won't intercept the calls on initial setup, which is why you have to actually change the build.prop prior to initially setting up Wallet.
Click to expand...
Click to collapse
I think it actually just replaces the function that checks, "Is this device id allowed?" But for the initial setup the strings in build prop are sent to google where they can reject them server-side.

---

when trying to run the script, i keep getting a syntax error
pwnprop.sh: line 2: $'\r': command not found
pwnprop.sh: line 3: syntax error near unexpected token `$'\r''
'wnprop.sh: line 3: `do_replace ()
i'm doing:
bash pwnprop.sh classes
classes is my "outdir"
edit: alright, i've converted dos2unix. now i'm just getting errors that the file doesn't exist. argh, oh linux.
edit: zip has been updated to no longer check for su binary. still needs a device/carrier bypass restriction removed...

---

Fenny said:
I think it actually just replaces the function that checks, "Is this device id allowed?" But for the initial setup the strings in build prop are sent to google where they can reject them server-side.
Click to expand...
Click to collapse
Gotcha, that makes perfect sense.

---

mrvirginia said:
when trying to run the script, i keep getting a syntax error
pwnprop.sh: line 2: $'\r': command not found
pwnprop.sh: line 3: syntax error near unexpected token `$'\r''
'wnprop.sh: line 3: `do_replace ()
i'm doing:
bash pwnprop.sh classes
classes is my "outdir"
edit: alright, i've converted dos2unix. now i'm just getting errors that the file doesn't exist. argh, oh linux.
edit: zip has been updated to no longer check for su binary. still needs a device/carrier bypass restriction removed...
Click to expand...
Click to collapse
Make sure you have the sed, echo, and grep utilities installed and in your path.
Sent from my GT-I9505G

---

Fenny said:
Make sure you have the sed, echo, and grep utilities installed and in your path.
Sent from my GT-I9505G
Click to expand...
Click to collapse
i finally figured out what the problem was. iirc, i was running it as root or something. had the same problem when i tried using the Kitchen again a week or two ago and got it sorted so i'll attempt to run this again [hopefully] over the weekend and give everyone a working Wallet regardless of device so they won't have to do silly tweaks anymore with build.prop etc. thank you again, sir.
oh, did you ever figure out the SIM unlock issue?

---

Causes NFC to FC on official 4.3 with full wipe. Oddly, it works with dirty flash. Ideas?
[Edit]
Never mind. It was just a bad signature.

---

@ OP: this NfcNci mod works on TW firmware MF8.

---

maanz said:
@ OP: this NfcNci mod works on TW firmware MF8.
Click to expand...
Click to collapse
Good to hear. Sounds like this is a new feature in Samsung firmware. Still makes me wonder if non-samsung devices suffer the same fate. The function call is the same no matter which implementation of NfcNci you are using, but I suppose that each vendor's implementation of the integrity checks by necessesity will differ.
Sent from my GT-I9505G

---

@Fenny looks like Superuser (unsecure) check was removed from newest Wallet release on the Google Play Store

---

mrvirginia said:
@Fenny looks like Superuser (unsecure) check was removed from newest Wallet release on the Google Play Store
Click to expand...
Click to collapse
That is great news. Much less work to be done on it then.

---

Keep up the good work! You guys are close, I can feel it! I would offer to help this weekend, but I think I would just slow you down.
Sent from my Galaxy Nexus using XDA Premium 4 mobile app