1 /* 2 * Copyright (C) 2018 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.server.connectivity; 18 19 import static android.net.ConnectivityManager.PRIVATE_DNS_DEFAULT_MODE_FALLBACK; 20 import static android.net.ConnectivityManager.PRIVATE_DNS_MODE_OFF; 21 import static android.net.ConnectivityManager.PRIVATE_DNS_MODE_PROVIDER_HOSTNAME; 22 import static android.provider.Settings.Global.DNS_RESOLVER_MAX_SAMPLES; 23 import static android.provider.Settings.Global.DNS_RESOLVER_MIN_SAMPLES; 24 import static android.provider.Settings.Global.DNS_RESOLVER_SAMPLE_VALIDITY_SECONDS; 25 import static android.provider.Settings.Global.DNS_RESOLVER_SUCCESS_THRESHOLD_PERCENT; 26 import static android.provider.Settings.Global.PRIVATE_DNS_DEFAULT_MODE; 27 import static android.provider.Settings.Global.PRIVATE_DNS_MODE; 28 import static android.provider.Settings.Global.PRIVATE_DNS_SPECIFIER; 29 30 import android.content.ContentResolver; 31 import android.content.Context; 32 import android.content.Intent; 33 import android.net.IDnsResolver; 34 import android.net.LinkProperties; 35 import android.net.Network; 36 import android.net.NetworkUtils; 37 import android.net.ResolverParamsParcel; 38 import android.net.Uri; 39 import android.net.shared.PrivateDnsConfig; 40 import android.os.Binder; 41 import android.os.RemoteException; 42 import android.os.ServiceSpecificException; 43 import android.os.UserHandle; 44 import android.provider.Settings; 45 import android.text.TextUtils; 46 import android.util.Pair; 47 import android.util.Slog; 48 49 import java.net.InetAddress; 50 import java.util.Arrays; 51 import java.util.Collection; 52 import java.util.Collections; 53 import java.util.HashMap; 54 import java.util.HashSet; 55 import java.util.Iterator; 56 import java.util.Map; 57 import java.util.Set; 58 import java.util.stream.Collectors; 59 60 61 /** 62 * Encapsulate the management of DNS settings for networks. 63 * 64 * This class it NOT designed for concurrent access. Furthermore, all non-static 65 * methods MUST be called from ConnectivityService's thread. 66 * 67 * [ Private DNS ] 68 * The code handling Private DNS is spread across several components, but this 69 * seems like the least bad place to collect all the observations. 70 * 71 * Private DNS handling and updating occurs in response to several different 72 * events. Each is described here with its corresponding intended handling. 73 * 74 * [A] Event: A new network comes up. 75 * Mechanics: 76 * [1] ConnectivityService gets notifications from NetworkAgents. 77 * [2] in updateNetworkInfo(), the first time the NetworkAgent goes into 78 * into CONNECTED state, the Private DNS configuration is retrieved, 79 * programmed, and strict mode hostname resolution (if applicable) is 80 * enqueued in NetworkAgent's NetworkMonitor, via a call to 81 * handlePerNetworkPrivateDnsConfig(). 82 * [3] Re-resolution of strict mode hostnames that fail to return any 83 * IP addresses happens inside NetworkMonitor; it sends itself a 84 * delayed CMD_EVALUATE_PRIVATE_DNS message in a simple backoff 85 * schedule. 86 * [4] Successfully resolved hostnames are sent to ConnectivityService 87 * inside an EVENT_PRIVATE_DNS_CONFIG_RESOLVED message. The resolved 88 * IP addresses are programmed into netd via: 89 * 90 * updatePrivateDns() -> updateDnses() 91 * 92 * both of which make calls into DnsManager. 93 * [5] Upon a successful hostname resolution NetworkMonitor initiates a 94 * validation attempt in the form of a lookup for a one-time hostname 95 * that uses Private DNS. 96 * 97 * [B] Event: Private DNS settings are changed. 98 * Mechanics: 99 * [1] ConnectivityService gets notifications from its SettingsObserver. 100 * [2] handlePrivateDnsSettingsChanged() is called, which calls 101 * handlePerNetworkPrivateDnsConfig() and the process proceeds 102 * as if from A.3 above. 103 * 104 * [C] Event: An application calls ConnectivityManager#reportBadNetwork(). 105 * Mechanics: 106 * [1] NetworkMonitor is notified and initiates a reevaluation, which 107 * always bypasses Private DNS. 108 * [2] Once completed, NetworkMonitor checks if strict mode is in operation 109 * and if so enqueues another evaluation of Private DNS, as if from 110 * step A.5 above. 111 * 112 * @hide 113 */ 114 public class DnsManager { 115 private static final String TAG = DnsManager.class.getSimpleName(); 116 private static final PrivateDnsConfig PRIVATE_DNS_OFF = new PrivateDnsConfig(); 117 118 /* Defaults for resolver parameters. */ 119 private static final int DNS_RESOLVER_DEFAULT_SAMPLE_VALIDITY_SECONDS = 1800; 120 private static final int DNS_RESOLVER_DEFAULT_SUCCESS_THRESHOLD_PERCENT = 25; 121 private static final int DNS_RESOLVER_DEFAULT_MIN_SAMPLES = 8; 122 private static final int DNS_RESOLVER_DEFAULT_MAX_SAMPLES = 64; 123 getPrivateDnsConfig(ContentResolver cr)124 public static PrivateDnsConfig getPrivateDnsConfig(ContentResolver cr) { 125 final String mode = getPrivateDnsMode(cr); 126 127 final boolean useTls = !TextUtils.isEmpty(mode) && !PRIVATE_DNS_MODE_OFF.equals(mode); 128 129 if (PRIVATE_DNS_MODE_PROVIDER_HOSTNAME.equals(mode)) { 130 final String specifier = getStringSetting(cr, PRIVATE_DNS_SPECIFIER); 131 return new PrivateDnsConfig(specifier, null); 132 } 133 134 return new PrivateDnsConfig(useTls); 135 } 136 getPrivateDnsSettingsUris()137 public static Uri[] getPrivateDnsSettingsUris() { 138 return new Uri[]{ 139 Settings.Global.getUriFor(PRIVATE_DNS_DEFAULT_MODE), 140 Settings.Global.getUriFor(PRIVATE_DNS_MODE), 141 Settings.Global.getUriFor(PRIVATE_DNS_SPECIFIER), 142 }; 143 } 144 145 public static class PrivateDnsValidationUpdate { 146 final public int netId; 147 final public InetAddress ipAddress; 148 final public String hostname; 149 final public boolean validated; 150 PrivateDnsValidationUpdate(int netId, InetAddress ipAddress, String hostname, boolean validated)151 public PrivateDnsValidationUpdate(int netId, InetAddress ipAddress, 152 String hostname, boolean validated) { 153 this.netId = netId; 154 this.ipAddress = ipAddress; 155 this.hostname = hostname; 156 this.validated = validated; 157 } 158 } 159 160 private static class PrivateDnsValidationStatuses { 161 enum ValidationStatus { 162 IN_PROGRESS, 163 FAILED, 164 SUCCEEDED 165 } 166 167 // Validation statuses of <hostname, ipAddress> pairs for a single netId 168 // Caution : not thread-safe. As mentioned in the top file comment, all 169 // methods of this class must only be called on ConnectivityService's thread. 170 private Map<Pair<String, InetAddress>, ValidationStatus> mValidationMap; 171 PrivateDnsValidationStatuses()172 private PrivateDnsValidationStatuses() { 173 mValidationMap = new HashMap<>(); 174 } 175 hasValidatedServer()176 private boolean hasValidatedServer() { 177 for (ValidationStatus status : mValidationMap.values()) { 178 if (status == ValidationStatus.SUCCEEDED) { 179 return true; 180 } 181 } 182 return false; 183 } 184 updateTrackedDnses(String[] ipAddresses, String hostname)185 private void updateTrackedDnses(String[] ipAddresses, String hostname) { 186 Set<Pair<String, InetAddress>> latestDnses = new HashSet<>(); 187 for (String ipAddress : ipAddresses) { 188 try { 189 latestDnses.add(new Pair(hostname, 190 InetAddress.parseNumericAddress(ipAddress))); 191 } catch (IllegalArgumentException e) {} 192 } 193 // Remove <hostname, ipAddress> pairs that should not be tracked. 194 for (Iterator<Map.Entry<Pair<String, InetAddress>, ValidationStatus>> it = 195 mValidationMap.entrySet().iterator(); it.hasNext(); ) { 196 Map.Entry<Pair<String, InetAddress>, ValidationStatus> entry = it.next(); 197 if (!latestDnses.contains(entry.getKey())) { 198 it.remove(); 199 } 200 } 201 // Add new <hostname, ipAddress> pairs that should be tracked. 202 for (Pair<String, InetAddress> p : latestDnses) { 203 if (!mValidationMap.containsKey(p)) { 204 mValidationMap.put(p, ValidationStatus.IN_PROGRESS); 205 } 206 } 207 } 208 updateStatus(PrivateDnsValidationUpdate update)209 private void updateStatus(PrivateDnsValidationUpdate update) { 210 Pair<String, InetAddress> p = new Pair(update.hostname, 211 update.ipAddress); 212 if (!mValidationMap.containsKey(p)) { 213 return; 214 } 215 if (update.validated) { 216 mValidationMap.put(p, ValidationStatus.SUCCEEDED); 217 } else { 218 mValidationMap.put(p, ValidationStatus.FAILED); 219 } 220 } 221 fillInValidatedPrivateDns(LinkProperties lp)222 private LinkProperties fillInValidatedPrivateDns(LinkProperties lp) { 223 lp.setValidatedPrivateDnsServers(Collections.EMPTY_LIST); 224 mValidationMap.forEach((key, value) -> { 225 if (value == ValidationStatus.SUCCEEDED) { 226 lp.addValidatedPrivateDnsServer(key.second); 227 } 228 }); 229 return lp; 230 } 231 } 232 233 private final Context mContext; 234 private final ContentResolver mContentResolver; 235 private final IDnsResolver mDnsResolver; 236 private final MockableSystemProperties mSystemProperties; 237 // TODO: Replace these Maps with SparseArrays. 238 private final Map<Integer, PrivateDnsConfig> mPrivateDnsMap; 239 private final Map<Integer, PrivateDnsValidationStatuses> mPrivateDnsValidationMap; 240 241 private int mNumDnsEntries; 242 private int mSampleValidity; 243 private int mSuccessThreshold; 244 private int mMinSamples; 245 private int mMaxSamples; 246 private String mPrivateDnsMode; 247 private String mPrivateDnsSpecifier; 248 DnsManager(Context ctx, IDnsResolver dnsResolver, MockableSystemProperties sp)249 public DnsManager(Context ctx, IDnsResolver dnsResolver, MockableSystemProperties sp) { 250 mContext = ctx; 251 mContentResolver = mContext.getContentResolver(); 252 mDnsResolver = dnsResolver; 253 mSystemProperties = sp; 254 mPrivateDnsMap = new HashMap<>(); 255 mPrivateDnsValidationMap = new HashMap<>(); 256 257 // TODO: Create and register ContentObservers to track every setting 258 // used herein, posting messages to respond to changes. 259 } 260 getPrivateDnsConfig()261 public PrivateDnsConfig getPrivateDnsConfig() { 262 return getPrivateDnsConfig(mContentResolver); 263 } 264 removeNetwork(Network network)265 public void removeNetwork(Network network) { 266 mPrivateDnsMap.remove(network.netId); 267 mPrivateDnsValidationMap.remove(network.netId); 268 } 269 updatePrivateDns(Network network, PrivateDnsConfig cfg)270 public PrivateDnsConfig updatePrivateDns(Network network, PrivateDnsConfig cfg) { 271 Slog.w(TAG, "updatePrivateDns(" + network + ", " + cfg + ")"); 272 return (cfg != null) 273 ? mPrivateDnsMap.put(network.netId, cfg) 274 : mPrivateDnsMap.remove(network.netId); 275 } 276 updatePrivateDnsStatus(int netId, LinkProperties lp)277 public void updatePrivateDnsStatus(int netId, LinkProperties lp) { 278 // Use the PrivateDnsConfig data pushed to this class instance 279 // from ConnectivityService. 280 final PrivateDnsConfig privateDnsCfg = mPrivateDnsMap.getOrDefault(netId, 281 PRIVATE_DNS_OFF); 282 283 final boolean useTls = privateDnsCfg.useTls; 284 final PrivateDnsValidationStatuses statuses = 285 useTls ? mPrivateDnsValidationMap.get(netId) : null; 286 final boolean validated = (null != statuses) && statuses.hasValidatedServer(); 287 final boolean strictMode = privateDnsCfg.inStrictMode(); 288 final String tlsHostname = strictMode ? privateDnsCfg.hostname : null; 289 final boolean usingPrivateDns = strictMode || validated; 290 291 lp.setUsePrivateDns(usingPrivateDns); 292 lp.setPrivateDnsServerName(tlsHostname); 293 if (usingPrivateDns && null != statuses) { 294 statuses.fillInValidatedPrivateDns(lp); 295 } else { 296 lp.setValidatedPrivateDnsServers(Collections.EMPTY_LIST); 297 } 298 } 299 updatePrivateDnsValidation(PrivateDnsValidationUpdate update)300 public void updatePrivateDnsValidation(PrivateDnsValidationUpdate update) { 301 final PrivateDnsValidationStatuses statuses = 302 mPrivateDnsValidationMap.get(update.netId); 303 if (statuses == null) return; 304 statuses.updateStatus(update); 305 } 306 setDnsConfigurationForNetwork( int netId, LinkProperties lp, boolean isDefaultNetwork)307 public void setDnsConfigurationForNetwork( 308 int netId, LinkProperties lp, boolean isDefaultNetwork) { 309 310 updateParametersSettings(); 311 final ResolverParamsParcel paramsParcel = new ResolverParamsParcel(); 312 313 // We only use the PrivateDnsConfig data pushed to this class instance 314 // from ConnectivityService because it works in coordination with 315 // NetworkMonitor to decide which networks need validation and runs the 316 // blocking calls to resolve Private DNS strict mode hostnames. 317 // 318 // At this time we do not attempt to enable Private DNS on non-Internet 319 // networks like IMS. 320 final PrivateDnsConfig privateDnsCfg = mPrivateDnsMap.getOrDefault(netId, 321 PRIVATE_DNS_OFF); 322 323 final boolean useTls = privateDnsCfg.useTls; 324 final boolean strictMode = privateDnsCfg.inStrictMode(); 325 paramsParcel.netId = netId; 326 paramsParcel.sampleValiditySeconds = mSampleValidity; 327 paramsParcel.successThreshold = mSuccessThreshold; 328 paramsParcel.minSamples = mMinSamples; 329 paramsParcel.maxSamples = mMaxSamples; 330 paramsParcel.servers = NetworkUtils.makeStrings(lp.getDnsServers()); 331 paramsParcel.domains = getDomainStrings(lp.getDomains()); 332 paramsParcel.tlsName = strictMode ? privateDnsCfg.hostname : ""; 333 paramsParcel.tlsServers = 334 strictMode ? NetworkUtils.makeStrings( 335 Arrays.stream(privateDnsCfg.ips) 336 .filter((ip) -> lp.isReachable(ip)) 337 .collect(Collectors.toList())) 338 : useTls ? paramsParcel.servers // Opportunistic 339 : new String[0]; // Off 340 paramsParcel.tlsFingerprints = new String[0]; 341 // Prepare to track the validation status of the DNS servers in the 342 // resolver config when private DNS is in opportunistic or strict mode. 343 if (useTls) { 344 if (!mPrivateDnsValidationMap.containsKey(netId)) { 345 mPrivateDnsValidationMap.put(netId, new PrivateDnsValidationStatuses()); 346 } 347 mPrivateDnsValidationMap.get(netId).updateTrackedDnses(paramsParcel.tlsServers, 348 paramsParcel.tlsName); 349 } else { 350 mPrivateDnsValidationMap.remove(netId); 351 } 352 353 Slog.d(TAG, String.format("setDnsConfigurationForNetwork(%d, %s, %s, %d, %d, %d, %d, " 354 + "%d, %d, %s, %s)", paramsParcel.netId, Arrays.toString(paramsParcel.servers), 355 Arrays.toString(paramsParcel.domains), paramsParcel.sampleValiditySeconds, 356 paramsParcel.successThreshold, paramsParcel.minSamples, 357 paramsParcel.maxSamples, paramsParcel.baseTimeoutMsec, 358 paramsParcel.retryCount, paramsParcel.tlsName, 359 Arrays.toString(paramsParcel.tlsServers))); 360 361 try { 362 mDnsResolver.setResolverConfiguration(paramsParcel); 363 } catch (RemoteException | ServiceSpecificException e) { 364 Slog.e(TAG, "Error setting DNS configuration: " + e); 365 return; 366 } 367 368 // TODO: netd should listen on [::1]:53 and proxy queries to the current 369 // default network, and we should just set net.dns1 to ::1, not least 370 // because applications attempting to use net.dns resolvers will bypass 371 // the privacy protections of things like DNS-over-TLS. 372 if (isDefaultNetwork) setDefaultDnsSystemProperties(lp.getDnsServers()); 373 flushVmDnsCache(); 374 } 375 setDefaultDnsSystemProperties(Collection<InetAddress> dnses)376 public void setDefaultDnsSystemProperties(Collection<InetAddress> dnses) { 377 int last = 0; 378 for (InetAddress dns : dnses) { 379 ++last; 380 setNetDnsProperty(last, dns.getHostAddress()); 381 } 382 for (int i = last + 1; i <= mNumDnsEntries; ++i) { 383 setNetDnsProperty(i, ""); 384 } 385 mNumDnsEntries = last; 386 } 387 flushVmDnsCache()388 private void flushVmDnsCache() { 389 /* 390 * Tell the VMs to toss their DNS caches 391 */ 392 final Intent intent = new Intent(Intent.ACTION_CLEAR_DNS_CACHE); 393 intent.addFlags(Intent.FLAG_RECEIVER_REPLACE_PENDING); 394 /* 395 * Connectivity events can happen before boot has completed ... 396 */ 397 intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT); 398 final long ident = Binder.clearCallingIdentity(); 399 try { 400 mContext.sendBroadcastAsUser(intent, UserHandle.ALL); 401 } finally { 402 Binder.restoreCallingIdentity(ident); 403 } 404 } 405 updateParametersSettings()406 private void updateParametersSettings() { 407 mSampleValidity = getIntSetting( 408 DNS_RESOLVER_SAMPLE_VALIDITY_SECONDS, 409 DNS_RESOLVER_DEFAULT_SAMPLE_VALIDITY_SECONDS); 410 if (mSampleValidity < 0 || mSampleValidity > 65535) { 411 Slog.w(TAG, "Invalid sampleValidity=" + mSampleValidity + ", using default=" + 412 DNS_RESOLVER_DEFAULT_SAMPLE_VALIDITY_SECONDS); 413 mSampleValidity = DNS_RESOLVER_DEFAULT_SAMPLE_VALIDITY_SECONDS; 414 } 415 416 mSuccessThreshold = getIntSetting( 417 DNS_RESOLVER_SUCCESS_THRESHOLD_PERCENT, 418 DNS_RESOLVER_DEFAULT_SUCCESS_THRESHOLD_PERCENT); 419 if (mSuccessThreshold < 0 || mSuccessThreshold > 100) { 420 Slog.w(TAG, "Invalid successThreshold=" + mSuccessThreshold + ", using default=" + 421 DNS_RESOLVER_DEFAULT_SUCCESS_THRESHOLD_PERCENT); 422 mSuccessThreshold = DNS_RESOLVER_DEFAULT_SUCCESS_THRESHOLD_PERCENT; 423 } 424 425 mMinSamples = getIntSetting(DNS_RESOLVER_MIN_SAMPLES, DNS_RESOLVER_DEFAULT_MIN_SAMPLES); 426 mMaxSamples = getIntSetting(DNS_RESOLVER_MAX_SAMPLES, DNS_RESOLVER_DEFAULT_MAX_SAMPLES); 427 if (mMinSamples < 0 || mMinSamples > mMaxSamples || mMaxSamples > 64) { 428 Slog.w(TAG, "Invalid sample count (min, max)=(" + mMinSamples + ", " + mMaxSamples + 429 "), using default=(" + DNS_RESOLVER_DEFAULT_MIN_SAMPLES + ", " + 430 DNS_RESOLVER_DEFAULT_MAX_SAMPLES + ")"); 431 mMinSamples = DNS_RESOLVER_DEFAULT_MIN_SAMPLES; 432 mMaxSamples = DNS_RESOLVER_DEFAULT_MAX_SAMPLES; 433 } 434 } 435 getIntSetting(String which, int dflt)436 private int getIntSetting(String which, int dflt) { 437 return Settings.Global.getInt(mContentResolver, which, dflt); 438 } 439 setNetDnsProperty(int which, String value)440 private void setNetDnsProperty(int which, String value) { 441 final String key = "net.dns" + which; 442 // Log and forget errors setting unsupported properties. 443 try { 444 mSystemProperties.set(key, value); 445 } catch (Exception e) { 446 Slog.e(TAG, "Error setting unsupported net.dns property: ", e); 447 } 448 } 449 getPrivateDnsMode(ContentResolver cr)450 private static String getPrivateDnsMode(ContentResolver cr) { 451 String mode = getStringSetting(cr, PRIVATE_DNS_MODE); 452 if (TextUtils.isEmpty(mode)) mode = getStringSetting(cr, PRIVATE_DNS_DEFAULT_MODE); 453 if (TextUtils.isEmpty(mode)) mode = PRIVATE_DNS_DEFAULT_MODE_FALLBACK; 454 return mode; 455 } 456 getStringSetting(ContentResolver cr, String which)457 private static String getStringSetting(ContentResolver cr, String which) { 458 return Settings.Global.getString(cr, which); 459 } 460 getDomainStrings(String domains)461 private static String[] getDomainStrings(String domains) { 462 return (TextUtils.isEmpty(domains)) ? new String[0] : domains.split(" "); 463 } 464 } 465