mirror of https://github.com/M66B/FairEmail.git
M66B
4 years ago
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package eu.faircode.email;
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/*
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This file is part of FairEmail.
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FairEmail is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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FairEmail is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FairEmail. If not, see <http://www.gnu.org/licenses/>.
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Copyright 2018-2021 by Marcel Bokhorst (M66B)
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*/
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import android.text.TextUtils;
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import java.net.Inet4Address;
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import java.net.Inet6Address;
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import java.net.InetAddress;
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import java.net.UnknownHostException;
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import java.util.Date;
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import java.util.Hashtable;
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import java.util.Map;
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public class DnsBlockList {
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// https://www.spamhaus.org/zen/
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static String[] DEFAULT_BLOCKLISTS = new String[]{"zen.spamhaus.org"};
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private static final long CACHE_EXPIRY_AFTER = 3600 * 1000L; // milliseconds
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private static final Map<InetAddress, CacheEntry> cache = new Hashtable<>();
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static boolean isJunk(String email) {
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return isJunk(email, DEFAULT_BLOCKLISTS);
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}
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static boolean isJunk(String email, String[] blocklists) {
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if (TextUtils.isEmpty(email))
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return false;
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int at = email.indexOf('@');
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if (at < 0)
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return false;
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String domain = email.substring(at + 1);
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for (String blocklist : blocklists)
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if (isJunk(domain, blocklist))
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return true;
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return false;
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}
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private static boolean isJunk(String domain, String blocklist) {
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boolean blocked = false;
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try {
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for (InetAddress addr : InetAddress.getAllByName(domain))
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try {
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synchronized (cache) {
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CacheEntry cached = cache.get(addr);
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if (cached != null && !cached.isExpired())
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return cached.isJunk();
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}
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StringBuilder lookup = new StringBuilder();
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if (addr instanceof Inet4Address) {
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byte[] a = addr.getAddress();
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for (int i = 3; i >= 0; i--)
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lookup.append(a[i] & 0xff).append('.');
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} else if (addr instanceof Inet6Address) {
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byte[] a = addr.getAddress();
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for (int i = 15; i >= 0; i--) {
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int b = a[i] & 0xff;
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lookup.append(String.format("%01x", b & 0xf)).append('.');
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lookup.append(String.format("%01x", b >> 4)).append('.');
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}
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}
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lookup.append(blocklist);
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InetAddress result;
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try {
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result = InetAddress.getByName(lookup.toString());
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if (result instanceof Inet4Address) {
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/*
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https://www.spamhaus.org/faq/section/DNSBL%20Usage#200
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127.0.0.2 SBL Spamhaus SBL Data
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127.0.0.3 SBL Spamhaus SBL CSS Data
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127.0.0.4 XBL CBL Data
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127.0.0.9 SBL Spamhaus DROP/EDROP Data (in addition to 127.0.0.2, since 01-Jun-2016)
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127.0.0.10 PBL ISP Maintained
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127.0.0.11 PBL Spamhaus Maintained
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*/
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byte[] a = result.getAddress();
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int statusClass = a[1] & 0xFF;
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int statusCode = a[3] & 0xFF;
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if (statusClass != 0 ||
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(statusCode != 2 &&
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statusCode != 3 &&
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statusCode != 4 &&
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statusCode != 9)) {
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Log.w("isJunk" +
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" addr=" + addr +
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" lookup=" + lookup +
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" result=" + result +
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" status=" + statusClass + "/" + statusCode);
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result = null;
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}
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} else {
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Log.w("isJunk result=" + result);
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result = null;
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}
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} catch (UnknownHostException ignored) {
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// Not blocked
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result = null;
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}
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Log.i("isJunk " + addr + " " + lookup + "=" + (result == null ? "false" : result));
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synchronized (cache) {
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cache.put(addr, new CacheEntry(result));
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}
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if (result != null)
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blocked = true;
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} catch (Throwable ex) {
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Log.w(ex);
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}
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} catch (Throwable ex) {
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Log.w(ex);
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}
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return blocked;
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}
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private static class CacheEntry {
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private final long time;
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private final InetAddress result;
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CacheEntry(InetAddress result) {
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this.time = new Date().getTime();
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this.result = result;
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}
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boolean isExpired() {
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return (new Date().getTime() - this.time) > CACHE_EXPIRY_AFTER;
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}
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boolean isJunk() {
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return (this.result != null);
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}
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}
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}
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