SafetyNet: package name always return null

问题

I am implementing SafetyNet API based on Google SafetyNet sample and SafetyNet Helper

Here is my working code. First part is processing code I used at SafetyNetSampleFragment:

import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.FragmentActivity;
import android.util.Base64;
import android.util.Log;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.common.api.ResultCallback;
import com.google.android.gms.common.api.Status;
import com.google.android.gms.safetynet.SafetyNet;
import com.google.android.gms.safetynet.SafetyNetApi;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.security.SecureRandom;
import java.util.Random;


public class SafetyNetVerifier implements GoogleApiClient.OnConnectionFailedListener {

    private final Random mRandom = new SecureRandom();
    private String mResult;
    private GoogleApiClient mGoogleApiClient;

    private FragmentActivity activity;

    public SafetyNetVerifier(FragmentActivity activity) {
        this.activity = activity;
        buildGoogleApiClient();
        sendSafetyNetRequest();
    }

    private byte[] getRequestNonce(String data) {
        ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
        byte[] bytes = new byte[24];
        mRandom.nextBytes(bytes);
        try {
            byteStream.write(bytes);
            byteStream.write(data.getBytes());
        } catch (IOException e) {
            return null;
        }

        return byteStream.toByteArray();
    }

    protected synchronized void buildGoogleApiClient() {
        mGoogleApiClient = new GoogleApiClient.Builder(activity)
                .addApi(SafetyNet.API)
                .enableAutoManage(activity, this)
                .build();
    }

    private void sendSafetyNetRequest() {
        Log.e("hqthao", "Sending SafetyNet API request.");

        String nonceData = "Safety Net Sample: " + System.currentTimeMillis();
        byte[] nonce = getRequestNonce(nonceData);

        SafetyNet.SafetyNetApi.attest(mGoogleApiClient, nonce)
                .setResultCallback(new ResultCallback<SafetyNetApi.AttestationResult>() {

                    @Override
                    public void onResult(SafetyNetApi.AttestationResult result) {
                        Status status = result.getStatus();
                        if (status.isSuccess()) {
                            mResult = result.getJwsResult();
                            Log.e("hqthao", "Success! SafetyNet result:\n" + mResult + "\n");
                            SafetyNetResponse response = parseJsonWebSignature(mResult);
                            Log.e("hqthao", response.toString());
                        }
                    }
                });
    }

    @Nullable
    private SafetyNetResponse parseJsonWebSignature(String jwsResult) {
        if (jwsResult == null) {
            return null;
        }
        //the JWT (JSON WEB TOKEN) is just a 3 base64 encoded parts concatenated by a . character
        final String[] jwtParts = jwsResult.split("\\.");

        if (jwtParts.length == 3) {
            //we're only really interested in the body/payload
            String decodedPayload = new String(Base64.decode(jwtParts[1], Base64.DEFAULT));

            return SafetyNetResponse.parse(decodedPayload);
        } else {
            return null;
        }
    }

    @Override
    public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
        Log.e("hqthao", "Error connecting to Google Play Services." + connectionResult.getErrorMessage());
    }

}

Here is the model SafetyNetResponse I copied from SafetyNetResponse:

import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.util.Log;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.Arrays;

public class SafetyNetResponse {

    private static final String TAG = SafetyNetResponse.class.getSimpleName();
    private String nonce;
    private long timestampMs;
    private String apkPackageName;
    private String[] apkCertificateDigestSha256;
    private String apkDigestSha256;
    private boolean ctsProfileMatch;
    private boolean basicIntegrity;

    //forces the parse()
    private SafetyNetResponse() {
    }

    /**
     * @return BASE64 encoded
     */
    public String getNonce() {
        return nonce;
    }

    public long getTimestampMs() {
        return timestampMs;
    }

    /**
     * @return com.package.name.of.requesting.app
     */
    public String getApkPackageName() {
        return apkPackageName;
    }

    /**
     * SHA-256 hash of the certificate used to sign requesting app
     *
     * @return BASE64 encoded
     */
    public String[] getApkCertificateDigestSha256() {
        return apkCertificateDigestSha256;
    }

    /**
     * SHA-256 hash of the app's APK
     *
     * @return BASE64 encoded
     */
    public String getApkDigestSha256() {
        return apkDigestSha256;
    }


    /**
     * If the value of "ctsProfileMatch" is true, then the profile of the device running your app matches the profile of a device that has passed Android compatibility testing.
     *
     * @return
     */
    public boolean isCtsProfileMatch() {
        return ctsProfileMatch;
    }

    /**
     * If the value of "basicIntegrity" is true, then the device running your app likely wasn't tampered with, but the device has not necessarily passed Android compatibility testing.
     *
     * @return
     */
    public boolean isBasicIntegrity() {
        return basicIntegrity;
    }

    /**
     * Parse the JSON string into populated SafetyNetResponse object
     *
     * @param decodedJWTPayload JSON String (always a json string according to JWT spec)
     * @return populated SafetyNetResponse
     */
    @Nullable
    public static SafetyNetResponse parse(@NonNull String decodedJWTPayload) {

        Log.d(TAG, "decodedJWTPayload json:" + decodedJWTPayload);

        SafetyNetResponse response = new SafetyNetResponse();
        try {
            JSONObject root = new JSONObject(decodedJWTPayload);
            if (root.has("nonce")) {
                response.nonce = root.getString("nonce");
            }

            if (root.has("apkCertificateDigestSha256")) {
                JSONArray jsonArray = root.getJSONArray("apkCertificateDigestSha256");
                if (jsonArray != null) {
                    String[] certDigests = new String[jsonArray.length()];
                    for (int i = 0; i < jsonArray.length(); i++) {
                        certDigests[i] = jsonArray.getString(i);
                    }
                    response.apkCertificateDigestSha256 = certDigests;
                }
            }

            if (root.has("apkDigestSha256")) {
                response.apkDigestSha256 = root.getString("apkDigestSha256");
            }

            if (root.has("apkPackageName")) {
                response.apkPackageName = root.getString("apkPackageName");
            }

            if (root.has("basicIntegrity")) {
                response.basicIntegrity = root.getBoolean("basicIntegrity");
            }

            if (root.has("ctsProfileMatch")) {
                response.ctsProfileMatch = root.getBoolean("ctsProfileMatch");
            }

            if (root.has("timestampMs")) {
                response.timestampMs = root.getLong("timestampMs");
            }

            return response;
        } catch (JSONException e) {
            Log.e(TAG, "problem parsing decodedJWTPayload:" + e.getMessage(), e);
        }
        return null;
    }


    @Override
    public String toString() {
        return "SafetyNetResponse{" +
                "nonce='" + nonce + '\'' +
                ", timestampMs=" + timestampMs +
                ", apkPackageName='" + apkPackageName + '\'' +
                ", apkCertificateDigestSha256=" + Arrays.toString(apkCertificateDigestSha256) +
                ", apkDigestSha256='" + apkDigestSha256 + '\'' +
                ", ctsProfileMatch=" + ctsProfileMatch +
                ", basicIntegrity=" + basicIntegrity +
                '}';
    }
}

We can easily call above workable code by calling this line of code inside activity:

    new SafetyNetVerifier(this);

The result is:

SafetyNetResponse{
 nonce='Xc4dSnAjAqf9KWDZokwK2TdBw9Td+ZILU2FmZXR5IE5ldCBTYW1wbGU6IDE0ODcxODQyMjYwNjc=', 
timestampMs=1487184225994, 
apkPackageName='null', 
apkCertificateDigestSha256=[], 
apkDigestSha256='null', 
ctsProfileMatch=false, 
basicIntegrity=false
}

As timestamp parsed correctly. I think I have get successfully safetynet response. But I don't know why apkPackageName always null and other fields as I have shown are empty. Please help me.

回答1:

In your SafetyNetResponse object, you'll notice that basicIntegrity is false. This suggests some sort of system tampering other modification has been detected (rooting is one example of this).

This gives a clue as to why the APK information fields are absent. As described in the documentation:

The apkPackageName, apkCertificateDigestSha256, and apkDigestSha256 fields provide information about the APK that you can use to verify the identity of the calling app. These fields are absent if the API cannot reliably determine the APK information.

Your code appears to be working correctly. You can verify this by testing on an unmodified device running an approved Android build - the missing info should then be included.

来源：https://stackoverflow.com/questions/42258489/safetynet-package-name-always-return-null

标签

android

google-play-services

safetynet