tsig.h 19.1 KB
 JINMEI Tatuya committed Apr 26, 2011 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 ``````// Copyright (C) 2011 Internet Systems Consortium, Inc. ("ISC") // // Permission to use, copy, modify, and/or distribute this software for any // purpose with or without fee is hereby granted, provided that the above // copyright notice and this permission notice appear in all copies. // // THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH // REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY // AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, // INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM // LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE // OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR // PERFORMANCE OF THIS SOFTWARE. #ifndef __TSIG_H #define __TSIG_H 1 #include `````` JINMEI Tatuya committed May 05, 2011 20 21 ``````#include `````` JINMEI Tatuya committed Apr 26, 2011 22 23 ``````#include #include `````` JINMEI Tatuya committed Apr 27, 2011 24 ``````#include `````` JINMEI Tatuya committed Apr 26, 2011 25 26 27 `````` namespace isc { namespace dns { `````` JINMEI Tatuya committed May 05, 2011 28 29 30 31 32 33 34 35 36 37 38 39 40 `````` /// An exception that is thrown for logic errors identified in TSIG /// sign/verify operations. /// /// Note that this exception is not thrown for TSIG protocol errors such as /// verification failures. In general, this exception indicates an internal /// program bug. class TSIGContextError : public isc::Exception { public: TSIGContextError(const char* file, size_t line, const char* what) : isc::Exception(file, line, what) {} }; `````` JINMEI Tatuya committed Apr 26, 2011 41 42 43 44 45 46 47 48 49 50 51 52 53 ``````/// TSIG session context. /// /// The \c TSIGContext class maintains a context of a signed session of /// DNS transactions by TSIG. In many cases a TSIG signed session consists /// of a single set of request (e.g. normal query) and reply (e.g. normal /// response), where the request is initially signed by the client, and the /// reply is signed by the server using the initial signature. As mentioned /// in RFC2845, a session can consist of multiple exchanges in a TCP /// connection. As also mentioned in the RFC, an AXFR response often contains /// multiple DNS messages, which can belong to the same TSIG session. /// This class supports all these cases. /// /// A \c TSIGContext object is generally constructed with a TSIG key to be `````` JINMEI Tatuya committed Apr 26, 2011 54 ``````/// used for the session, and keeps track of various kinds of session specific `````` JINMEI Tatuya committed Apr 26, 2011 55 56 57 58 59 60 ``````/// information, such as the original digest while waiting for a response or /// verification error information that is to be used for a subsequent /// response. /// /// This class has two main methods, \c sign() and \c verify(). /// The \c sign() method signs given data (which is supposed to be a complete `````` JINMEI Tatuya committed Apr 26, 2011 61 62 ``````/// DNS message without the TSIG itself) using the TSIG key and other /// related information associated with the \c TSIGContext object. `````` JINMEI Tatuya committed Apr 26, 2011 63 64 65 66 67 ``````/// The \c verify() method verifies a given DNS message that contains a TSIG /// RR using the key and other internal information. /// /// In general, a DNS client that wants to send a signed query will construct /// a \c TSIGContext object with the TSIG key that the client is intending to `````` JINMEI Tatuya committed Apr 26, 2011 68 69 ``````/// use, and sign the query with the context. The client will keeps the /// context, and verify the response with it. `````` JINMEI Tatuya committed Apr 26, 2011 70 71 72 73 74 75 76 ``````/// /// On the other hand, a DNS server will construct a \c TSIGContext object /// with the information of the TSIG RR included in a query with a set of /// possible keys (in the form of a \c TSIGKeyRing object). The constructor /// in this mode will identify the appropriate TSIG key (or internally record /// an error if it doesn't find a key). The server will then verify the /// query with the context, and generate a signed response using the same `````` JINMEI Tatuya committed May 06, 2011 77 ``````/// same context. `````` JINMEI Tatuya committed Apr 26, 2011 78 79 80 ``````/// /// When multiple messages belong to the same TSIG session, either side /// (signer or verifier) will keep using the same context. It records `````` JINMEI Tatuya committed Apr 26, 2011 81 ``````/// the latest session state (such as the previous digest) so that repeated `````` JINMEI Tatuya committed Apr 26, 2011 82 83 84 ``````/// calls to \c sign() or \c verify() work correctly in terms of the TSIG /// protocol. /// `````` JINMEI Tatuya committed May 06, 2011 85 86 87 88 89 90 91 ``````/// \b Examples /// /// This is a typical client application that sends a TSIG signed query /// and verifies the response. /// /// \code /// // "renderer" is of MessageRenderer to render the message. `````` JINMEI Tatuya committed May 09, 2011 92 93 ``````/// // (TSIGKey would be configured from config or command line in real app) /// TSIGContext ctx(TSIGKey("key.example:MSG6Ng==")); `````` JINMEI Tatuya committed May 06, 2011 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 ``````/// Message message(Message::RENDER); /// message.addQuestion(Question(Name("www.example.com"), RRClass::IN(), /// RRType::A())); /// message.toWire(renderer, ctx); /// /// // sendto, then recvfrom. received result in (data, data_len) /// /// message.clear(Message::PARSE); /// InputBuffer buffer(data, data_len); /// message.fromWire(buffer); /// TSIGError tsig_error = ctx.verify(message.getTSIGRecord(), /// data, data_len); /// if (tsig_error == TSIGError::NOERROR()) { /// // okay. ctx can be continuously used if it's receiving subsequent /// // signed responses from a TCP stream. /// } else if (message.getRcode() == Rcode::NOTAUTH()) { /// // hard error. give up this transaction per RFC2845 4.6. /// } else { `````` JINMEI Tatuya committed May 09, 2011 112 113 ``````/// // Other error: discard response keep waiting with the same ctx /// // for another (again, RFC2845 4.6). `````` JINMEI Tatuya committed May 06, 2011 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 ``````/// } \endcode /// /// And this is a typical server application that authenticates a signed /// query and returns a response according to the result. /// /// \code /// // Assume "message" is of type Message for query handling and /// // "renderer" is of MessageRenderer to render responses. /// Message message(Message::RENDER); /// /// TSIGKeyRing keyring; // this must be configured with keys somewhere /// /// // Receive a query and store it in (data, data_len) /// InputBuffer buffer(data, data_len); /// message.clear(Message::PARSE); /// message.fromWire(buffer); /// /// const TSIGRecord* tsig = message.getTSIGRecord(); /// if (tsig != NULL) { /// TSIGContext ctx(tsig->getName(), tsig->getRdata().getAlgorithm(), /// keyring); /// ctx.verify(tsig, data, data_len); /// /// // prepare response /// message.makeResponse(); /// //... /// message.toWire(renderer, ctx); /// /// // send the response data back to the client. /// // If this is a beginning of a signed session over a TCP and /// // server has more data to send to the client, this ctx /// // will be used to sign subsequent messages. /// } \endcode `````` JINMEI Tatuya committed Apr 26, 2011 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 ``````/// /// TCP Consideration /// /// RFC2845 describes the case where a single TSIG session is used for /// multiple DNS messages (Section 4.4). This class supports signing and /// verifying the messages in this scenario, but does not care if the messages /// were delivered over a TCP connection or not. If, for example, the /// same \c TSIGContext object is used to sign two independent DNS queries /// sent over UDP, they will be considered to belong to the same TSIG /// session, and, as a result, verification will be likely to fail. /// /// \b Copyability /// /// This class is currently non copyable based on the observation of the /// typical usage as described above. But there is no strong technical /// reason why this class cannot be copyable. If we see the need for it /// in future we may change the implementation on this point. /// /// Note to developers: /// One basic design choice is to make the \c TSIGContext class is as /// independent from the \c Message class. This is because the latter is /// much more complicated, depending on many other classes, while TSIG is /// a very specific part of the entire DNS protocol set. If the \c TSIGContext /// class depends on \c \c Message, it will be more vulnerable to changes /// to other classes, and will be more difficult to test due to the /// direct or indirect dependencies. The interface of \c sign() that takes /// opaque data (instead of, e.g., a \c Message or \c MessageRenderer object) /// is therefore a deliberate design decision. class TSIGContext : boost::noncopyable { public: /// Internal state of context /// /// The constants of this enum type define a specific state of /// \c TSIGContext to adjust the behavior. The definition is public /// and the state can be seen via the \c getState() method, but this is /// mostly private information. It's publicly visible mainly for testing /// purposes; there is no API for the application to change the state /// directly. enum State { INIT, ///< Initial state `````` JINMEI Tatuya committed May 06, 2011 187 188 189 190 `````` SENT_REQUEST, ///< Client sent a signed request, waiting response RECEIVED_REQUEST, ///< Server received a signed request SENT_RESPONSE, ///< Server sent a signed response VERIFIED_RESPONSE ///< Client successfully verified a response `````` JINMEI Tatuya committed Apr 26, 2011 191 192 193 194 195 196 197 198 199 200 201 202 `````` }; /// \name Constructors and destructor /// //@{ /// Constructor from a TSIG key. /// /// \exception std::bad_alloc Resource allocation for internal data fails /// /// \param key The TSIG key to be used for TSIG sessions with this context. explicit TSIGContext(const TSIGKey& key); `````` 203 204 205 206 `````` /// Constructor from key parameters and key ring. TSIGContext(const Name& key_name, const Name& algorithm_name, const TSIGKeyRing& keyring); `````` JINMEI Tatuya committed Apr 26, 2011 207 208 209 210 211 212 213 214 215 216 `````` /// The destructor. ~TSIGContext(); //@} /// Sign a DNS message. /// /// This method computes the TSIG MAC for the given data, which is /// generally expected to be a complete, wire-format DNS message /// that doesn't contain a TSIG RR, based on the TSIG key and /// other context information of \c TSIGContext, and returns a `````` JINMEI Tatuya committed Apr 26, 2011 217 218 `````` /// result in the form of a (pointer object pointing to) /// \c TSIGRecord object. `````` JINMEI Tatuya committed Apr 26, 2011 219 220 221 222 223 `````` /// /// The caller of this method will use the returned value to render a /// complete TSIG RR into the message that has been signed so that it /// will become a complete TSIG-signed message. /// `````` JINMEI Tatuya committed May 06, 2011 224 225 226 227 228 229 230 `````` /// In general, this method is called once by a client to send a /// signed request or one more times by a server to sign /// response(s) to a signed request. To avoid allowing accidental /// misuse, if this method is called after a "client" validates a /// response, an exception of class \c TSIGContextError will be /// thrown. /// `````` JINMEI Tatuya committed Apr 26, 2011 231 232 233 234 235 236 237 238 239 240 `````` /// \note Normal applications are not expected to call this method /// directly; they will usually use the \c Message::toWire() method /// with a \c TSIGContext object being a parameter and have the /// \c Message class create a complete signed message. /// /// This method treats the given data as opaque, even though it's generally /// expected to represent a wire-format DNS message (see also the class /// description), and doesn't inspect it in any way. For example, it /// doesn't check whether the data length is sane for a valid DNS message. /// This is also the reason why this method takes the \c qid parameter, `````` JINMEI Tatuya committed Apr 26, 2011 241 242 243 `````` /// which will be used as the original ID of the resulting /// \c TSIGRecordx object, even though this value should be stored in the /// first two octets (in wire format) of the given data. `````` JINMEI Tatuya committed Apr 26, 2011 244 `````` /// `````` JINMEI Tatuya committed Apr 26, 2011 245 246 247 248 249 250 `````` /// \note This method still checks and rejects empty data (\c NULL pointer /// data or the specified data length is 0) in order to avoid catastrophic /// effect such as program crash. Empty data is not necessarily invalid /// for HMAC computation, but obviously it doesn't make sense for a DNS /// message. /// `````` JINMEI Tatuya committed Apr 26, 2011 251 252 253 `````` /// This method provides the strong exception guarantee; unless the method /// returns (without an exception being thrown), the internal state of /// the \c TSIGContext won't be modified. `````` JINMEI Tatuya committed Apr 26, 2011 254 `````` /// `````` JINMEI Tatuya committed May 05, 2011 255 `````` /// \exception TSIGContextError Context already verified a response. `````` JINMEI Tatuya committed Apr 26, 2011 256 `````` /// \exception InvalidParameter \c data is NULL or \c data_len is 0 `````` JINMEI Tatuya committed Apr 26, 2011 257 258 259 260 261 `````` /// \exception cryptolink::LibraryError Some unexpected error in the /// underlying crypto operation /// \exception std::bad_alloc Temporary resource allocation failure /// /// \param qid The QID to be as the value of the original ID field of `````` JINMEI Tatuya committed Apr 26, 2011 262 `````` /// the resulting TSIG record `````` JINMEI Tatuya committed Apr 26, 2011 263 264 265 266 267 268 269 `````` /// \param data Points to the wire-format data to be signed /// \param data_len The length of \c data in bytes /// /// \return A TSIG record for the given data along with the context. ConstTSIGRecordPtr sign(const uint16_t qid, const void* const data, const size_t data_len); `````` JINMEI Tatuya committed May 06, 2011 270 271 272 273 274 275 276 277 278 279 `````` /// Verify a DNS message. /// /// This method verifies given data along with the context and a given /// TSIG in the form of a \c TSIGRecord object. The data to be verified /// is generally expected to be a complete, wire-format DNS message, /// exactly as received by the host, and ending with a TSIG RR. /// After verification process this method updates its internal state, /// and returns the result in the form of a \c TSIGError object. /// Possible return values are (see the \c TSIGError class description /// for the mnemonics): `````` JINMEI Tatuya committed May 05, 2011 280 `````` /// `````` JINMEI Tatuya committed May 06, 2011 281 282 283 284 285 286 287 288 289 `````` /// - \c NOERROR: The data has been verified correctly. /// - \c FORMERR: \c TSIGRecord is not given (see below). /// - \c BAD_KEY: Appropriate key is not found or specified key doesn't /// match for the data. /// - \c BAD_TIME: The current time doesn't fall in the range specified /// in the TSIG. /// - \c BAD_SIG: The signature given in the TSIG doesn't match against /// the locally computed digest or is the signature is /// invalid in other way. `````` JINMEI Tatuya committed May 05, 2011 290 `````` /// `````` JINMEI Tatuya committed May 06, 2011 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 `````` /// If this method is called by a DNS client waiting for a signed /// response and the result is not \c NOERROR, the context can be used /// to try validating another signed message as described in RFC2845 /// Section 4.6. /// /// If this method is called by a DNS server that tries to authenticate /// a signed request, and if the result is not \c NOERROR, the /// corresponding error condition is recorded in the context so that /// the server can return a response indicating what was wrong by calling /// \c sign() with the updated context. /// /// In general, this method is called once by a server for /// authenticating a signed request or one more times by a client to /// validate signed response(s) to a signed request. To avoid allowing /// accidental misuse, if this method is called after a "server" signs /// a response, an exception of class \c TSIGContextError will be thrown. /// /// The \c record parameter can be NULL; in that case this method simply /// returns \c FORMERR as the case described in Section 4.6 of RFC2845, /// i.e., receiving an unsigned response to a signed request. This way /// a client can transparently pass the result of /// \c Message::getTSIGRecord() without checking whether it's non NULL /// and take an appropriate action based on the result of this method. /// /// This method handles the given data mostly as opaque. It digests /// the data assuming it begins with a DNS header and ends with a TSIG /// RR whose length is given by calling \c TSIGRecord::getLength() on /// \c record, but otherwise it doesn't parse the data to confirm the /// assumption. It's caller's responsibility to ensure the data is /// valid and consistent with \c record. To avoid disruption, this /// method performs minimal validation on the given \c data and \c record: /// \c data must not be NULL; \c data_len must not be smaller than the /// sum of the DNS header length (fixed, 12 octets) and the length of /// the TSIG RR. If this check fails it throws an \c InvalidParameter /// exception. /// /// One unexpected case that is not covered by this method is that a /// client receives a signed response to an unsigned request. RFC2845 is /// silent about such cases; BIND 9 explicitly identifies the case and `````` JINMEI Tatuya committed May 09, 2011 330 `````` /// rejects it. With this implementation, the client can know that the `````` JINMEI Tatuya committed May 06, 2011 331 332 333 334 335 336 337 338 339 340 341 342 343 `````` /// response contains a TSIG via the result of /// \c Message::getTSIGRecord() and that it is an unexpected TSIG due to /// the fact that it doesn't have a corresponding \c TSIGContext. /// It's up to the client implementation whether to react to such a case /// explicitly (for example, it could either ignore the TSIG and accept /// the response or drop it). /// /// This method provides the strong exception guarantee; unless the method /// returns (without an exception being thrown), the internal state of /// the \c TSIGContext won't be modified. /// /// \todo Support intermediate TCP DNS messages without TSIG (RFC2845 4.4) /// \todo Signature truncation support based on RFC4635 `````` JINMEI Tatuya committed May 05, 2011 344 345 `````` /// /// \exception TSIGContextError Context already signed a response. `````` JINMEI Tatuya committed May 06, 2011 346 347 348 349 350 351 352 `````` /// \exception InvalidParameter \c data is NULL or \c data_len is too small. /// /// \param record The \c TSIGRecord to be verified with \c data /// \param data Points to the wire-format data (exactly as received) to /// be verified /// \param data_len The length of \c data in bytes /// \return The \c TSIGError that indicates verification result `````` JINMEI Tatuya committed May 05, 2011 353 354 355 `````` TSIGError verify(const TSIGRecord* const record, const void* const data, const size_t data_len); `````` JINMEI Tatuya committed Jul 14, 2011 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 `````` /// Return the expected length of TSIG RR after \c sign() /// /// This method returns the length of the TSIG RR based that would be /// produced as a result of \c sign() with the state of the context /// at the time of the call. The expected length can be decided /// from the key and the algorithm (which determines the MAC size if /// included) and the recorded TSIG error. Specifically, if a key /// related error has been identified, the MAC will be excluded; if /// a time error has occurred, the TSIG will include "other data". /// /// This method is provided mainly for the convenient of the Message class, /// which needs to know the expected TSIG length in rendering a signed /// DNS message so that it can handle truncated messages with TSIG /// correctly. Normal applications wouldn't need this method. The Python /// binding for this method won't be provided for the same reason. /// /// \exception None /// /// \return The expected TISG RR length in bytes `````` JINMEI Tatuya committed Jul 08, 2011 375 376 `````` size_t getTSIGLength() const; `````` JINMEI Tatuya committed Apr 26, 2011 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 `````` /// Return the current state of the context /// /// \note /// The states are visible in public mainly for testing purposes. /// Normal applications won't have to deal with them. /// /// \exception None State getState() const; /// Return the TSIG error as a result of the latest verification /// /// This method can be called even before verifying anything, but the /// returned value is meaningless in that case. /// /// \exception None TSIGError getError() const; /// \name Protocol constants and defaults /// //@{ /// The recommended fudge value (in seconds) by RFC2845. /// /// Right now fudge is not tunable, and all TSIGs generated by this API /// will have this value of fudge. static const uint16_t DEFAULT_FUDGE = 300; //@} private: struct TSIGContextImpl; TSIGContextImpl* impl_; }; } } #endif // __TSIG_H // Local Variables: // mode: c++ // End:``````