src/com/android/settings/wifi/dpp/WifiQrCode.java

/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.settings.wifi.dpp;

import android.net.wifi.WifiConfiguration;
import android.text.TextUtils;

import androidx.annotation.VisibleForTesting;

import java.util.Arrays;
import java.util.List;
import java.util.regex.Pattern;

/**
 * Supports to parse 2 types of QR code
 *
 *     1. Standard Wi-Fi DPP bootstrapping information or
 *     2. ZXing reader library's Wi-Fi Network config format described in
 *     https://github.com/zxing/zxing/wiki/Barcode-Contents#wi-fi-network-config-android-ios-11
 *
 * ZXing reader library's Wi-Fi Network config format example:
 *
 *     WIFI:T:WPA;S:mynetwork;P:mypass;;
 *
 * parameter Example    Description
 * T         WPA        Authentication type; can be WEP or WPA, or 'nopass' for no password. Or,
 *                      omit for no password.
 * S         mynetwork  Network SSID. Required. Enclose in double quotes if it is an ASCII name,
 *                      but could be interpreted as hex (i.e. "ABCD")
 * P         mypass     Password, ignored if T is "nopass" (in which case it may be omitted).
 *                      Enclose in double quotes if it is an ASCII name, but could be interpreted as
 *                      hex (i.e. "ABCD")
 * H         true       Optional. True if the network SSID is hidden.
 *
 */
public class WifiQrCode {
    public static final String SCHEME_DPP = "DPP";
    public static final String SCHEME_ZXING_WIFI_NETWORK_CONFIG = "WIFI";
    public static final String PREFIX_DPP = "DPP:";
    public static final String PREFIX_ZXING_WIFI_NETWORK_CONFIG = "WIFI:";

    public static final String PREFIX_DPP_PUBLIC_KEY = "K:";
    public static final String PREFIX_DPP_INFORMATION = "I:";

    public static final String PREFIX_ZXING_SECURITY = "T:";
    public static final String PREFIX_ZXING_SSID = "S:";
    public static final String PREFIX_ZXING_PASSWORD = "P:";
    public static final String PREFIX_ZXING_HIDDEN_SSID = "H:";

    public static final String DELIMITER_QR_CODE = ";";

    // Ignores password if security is SECURITY_NO_PASSWORD or absent
    public static final String SECURITY_NO_PASSWORD = "nopass"; //open network or OWE
    public static final String SECURITY_WEP = "WEP";
    public static final String SECURITY_WPA_PSK = "WPA";
    public static final String SECURITY_SAE = "SAE";

    private String mQrCode;

    /**
     * SCHEME_DPP for standard Wi-Fi device provision protocol; SCHEME_ZXING_WIFI_NETWORK_CONFIG
     * for ZXing reader library' Wi-Fi Network config format
     */
    private String mScheme;

    // Data from parsed Wi-Fi DPP QR code
    private String mPublicKey;
    private String mInformation;

    // Data from parsed ZXing reader library's Wi-Fi Network config format
    private WifiNetworkConfig mWifiNetworkConfig;

    public WifiQrCode(String qrCode) throws IllegalArgumentException {
        if (TextUtils.isEmpty(qrCode)) {
            throw new IllegalArgumentException("Empty QR code");
        }

        mQrCode = qrCode;

        if (qrCode.startsWith(PREFIX_DPP)) {
            mScheme = SCHEME_DPP;
            parseWifiDppQrCode(qrCode);
        } else if (qrCode.startsWith(PREFIX_ZXING_WIFI_NETWORK_CONFIG)) {
            mScheme = SCHEME_ZXING_WIFI_NETWORK_CONFIG;
            parseZxingWifiQrCode(qrCode);
        } else {
            throw new IllegalArgumentException("Invalid scheme");
        }
    }

    /** Parses Wi-Fi DPP QR code string */
    private void parseWifiDppQrCode(String qrCode) throws IllegalArgumentException {
        List keyValueList = getKeyValueList(qrCode, PREFIX_DPP, DELIMITER_QR_CODE);

        String publicKey = getValueOrNull(keyValueList, PREFIX_DPP_PUBLIC_KEY);
        if (TextUtils.isEmpty(publicKey)) {
            throw new IllegalArgumentException("Invalid format");
        }
        mPublicKey = publicKey;

        mInformation = getValueOrNull(keyValueList, PREFIX_DPP_INFORMATION);
    }

    /** Parses ZXing reader library's Wi-Fi Network config format */
    private void parseZxingWifiQrCode(String qrCode) throws IllegalArgumentException {
        List keyValueList = getKeyValueList(qrCode, PREFIX_ZXING_WIFI_NETWORK_CONFIG,
                DELIMITER_QR_CODE);

        String security = getValueOrNull(keyValueList, PREFIX_ZXING_SECURITY);
        String ssid = getValueOrNull(keyValueList, PREFIX_ZXING_SSID);
        String password = getValueOrNull(keyValueList, PREFIX_ZXING_PASSWORD);
        String hiddenSsidString = getValueOrNull(keyValueList, PREFIX_ZXING_HIDDEN_SSID);

        boolean hiddenSsid = "true".equalsIgnoreCase(hiddenSsidString);

        //"\", ";", "," and ":" are escaped with a backslash "\", should remove at first
        security = removeBackSlash(security);
        ssid = removeBackSlash(ssid);
        password = removeBackSlash(password);

        mWifiNetworkConfig = WifiNetworkConfig.getValidConfigOrNull(security, ssid, password,
                hiddenSsid, WifiConfiguration.INVALID_NETWORK_ID, /* isHotspot */ false);

        if (mWifiNetworkConfig == null) {
            throw new IllegalArgumentException("Invalid format");
        }
    }

    /**
     * Splits key/value pairs from qrCode
     *
     * @param qrCode the QR code raw string
     * @param prefixQrCode the string before all key/value pairs in qrCode
     * @param delimiter the string to split key/value pairs, can't contain a backslash
     * @return a list contains string of key/value (e.g. K:key1)
     */
    private List<String> getKeyValueList(String qrCode, String prefixQrCode,
                String delimiter) {
        String keyValueString = qrCode.substring(prefixQrCode.length());

        // Should not treat \delimiter as a delimiter
        String regex = "(?<!\\\\)" + Pattern.quote(delimiter);

        List<String> result = Arrays.asList(keyValueString.split(regex));
        return result;
    }

    private String getValueOrNull(List<String> keyValueList, String prefix) {
        for (String keyValue : keyValueList) {
            if (keyValue.startsWith(prefix)) {
                return  keyValue.substring(prefix.length());
            }
        }

        return null;
    }

    @VisibleForTesting
    String removeBackSlash(String input) {
        if (input == null) {
            return null;
        }

        StringBuilder sb = new StringBuilder();
        boolean backSlash = false;
        for (char ch : input.toCharArray()) {
            if (ch != '\\') {
                sb.append(ch);
                backSlash = false;
            } else {
                if (backSlash) {
                    sb.append(ch);
                    backSlash = false;
                    continue;
                }

                backSlash = true;
            }
        }

        return sb.toString();
    }

    public String getQrCode() {
        return mQrCode;
    }

    /**
     * Uses to check type of QR code
     *
     * SCHEME_DPP for standard Wi-Fi device provision protocol; SCHEME_ZXING_WIFI_NETWORK_CONFIG
     * for ZXing reader library' Wi-Fi Network config format
     */
    public String getScheme() {
        return mScheme;
    }

    /** Available when {@code getScheme()} returns SCHEME_DPP */
    @VisibleForTesting
    String getPublicKey() {
        return mPublicKey;
    }

    /** May be available when {@code getScheme()} returns SCHEME_DPP */
    public String getInformation() {
        return mInformation;
    }

    /** Available when {@code getScheme()} returns SCHEME_ZXING_WIFI_NETWORK_CONFIG */
    public WifiNetworkConfig getWifiNetworkConfig() {
        if (mWifiNetworkConfig == null) {
            return null;
        }

        return new WifiNetworkConfig(mWifiNetworkConfig);
    }

    public static WifiQrCode getValidWifiDppQrCodeOrNull(String qrCode) {
        WifiQrCode wifiQrCode;
        try {
            wifiQrCode = new WifiQrCode(qrCode);
        } catch(IllegalArgumentException e) {
            return null;
        }

        if (SCHEME_DPP.equals(wifiQrCode.getScheme())) {
            return wifiQrCode;
        }

        return null;
    }
}