1 /* -*- mode: c; tab-width: 8; c-basic-indent: 4; -*- */ 2 3 /*- 4 * Copyright (c) 2001 Charles Mott <cm@linktel.net> 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #include <sys/cdefs.h> 30 __FBSDID("$FreeBSD$"); 31 32 /* 33 Alias.c provides supervisory control for the functions of the 34 packet aliasing software. It consists of routines to monitor 35 TCP connection state, protocol-specific aliasing routines, 36 fragment handling and the following outside world functional 37 interfaces: SaveFragmentPtr, GetFragmentPtr, FragmentAliasIn, 38 PacketAliasIn and PacketAliasOut. 39 40 The other C program files are briefly described. The data 41 structure framework which holds information needed to translate 42 packets is encapsulated in alias_db.c. Data is accessed by 43 function calls, so other segments of the program need not know 44 about the underlying data structures. Alias_ftp.c contains 45 special code for modifying the ftp PORT command used to establish 46 data connections, while alias_irc.c does the same for IRC 47 DCC. Alias_util.c contains a few utility routines. 48 49 Version 1.0 August, 1996 (cjm) 50 51 Version 1.1 August 20, 1996 (cjm) 52 PPP host accepts incoming connections for ports 0 to 1023. 53 (Gary Roberts pointed out the need to handle incoming 54 connections.) 55 56 Version 1.2 September 7, 1996 (cjm) 57 Fragment handling error in alias_db.c corrected. 58 (Tom Torrance helped fix this problem.) 59 60 Version 1.4 September 16, 1996 (cjm) 61 - A more generalized method for handling incoming 62 connections, without the 0-1023 restriction, is 63 implemented in alias_db.c 64 - Improved ICMP support in alias.c. Traceroute 65 packet streams can now be correctly aliased. 66 - TCP connection closing logic simplified in 67 alias.c and now allows for additional 1 minute 68 "grace period" after FIN or RST is observed. 69 70 Version 1.5 September 17, 1996 (cjm) 71 Corrected error in handling incoming UDP packets with 0 checksum. 72 (Tom Torrance helped fix this problem.) 73 74 Version 1.6 September 18, 1996 (cjm) 75 Simplified ICMP aliasing scheme. Should now support 76 traceroute from Win95 as well as FreeBSD. 77 78 Version 1.7 January 9, 1997 (cjm) 79 - Out-of-order fragment handling. 80 - IP checksum error fixed for ftp transfers 81 from aliasing host. 82 - Integer return codes added to all 83 aliasing/de-aliasing functions. 84 - Some obsolete comments cleaned up. 85 - Differential checksum computations for 86 IP header (TCP, UDP and ICMP were already 87 differential). 88 89 Version 2.1 May 1997 (cjm) 90 - Added support for outgoing ICMP error 91 messages. 92 - Added two functions PacketAliasIn2() 93 and PacketAliasOut2() for dynamic address 94 control (e.g. round-robin allocation of 95 incoming packets). 96 97 Version 2.2 July 1997 (cjm) 98 - Rationalized API function names to begin 99 with "PacketAlias..." 100 - Eliminated PacketAliasIn2() and 101 PacketAliasOut2() as poorly conceived. 102 103 Version 2.3 Dec 1998 (dillon) 104 - Major bounds checking additions, see FreeBSD/CVS 105 106 Version 3.1 May, 2000 (salander) 107 - Added hooks to handle PPTP. 108 109 Version 3.2 July, 2000 (salander and satoh) 110 - Added PacketUnaliasOut routine. 111 - Added hooks to handle RTSP/RTP. 112 113 See HISTORY file for additional revisions. 114 */ 115 116 #include <sys/types.h> 117 118 #include <netinet/in_systm.h> 119 #include <netinet/in.h> 120 #include <netinet/ip.h> 121 #include <netinet/ip_icmp.h> 122 #include <netinet/tcp.h> 123 #include <netinet/udp.h> 124 125 #include <stdio.h> 126 127 #include "alias_local.h" 128 #include "alias.h" 129 130 #define NETBIOS_NS_PORT_NUMBER 137 131 #define NETBIOS_DGM_PORT_NUMBER 138 132 #define FTP_CONTROL_PORT_NUMBER 21 133 #define IRC_CONTROL_PORT_NUMBER_1 6667 134 #define IRC_CONTROL_PORT_NUMBER_2 6668 135 #define CUSEEME_PORT_NUMBER 7648 136 #define RTSP_CONTROL_PORT_NUMBER_1 554 137 #define RTSP_CONTROL_PORT_NUMBER_2 7070 138 #define TFTP_PORT_NUMBER 69 139 #define PPTP_CONTROL_PORT_NUMBER 1723 140 141 142 143 144 /* TCP Handling Routines 145 146 TcpMonitorIn() -- These routines monitor TCP connections, and 147 TcpMonitorOut() delete a link when a connection is closed. 148 149 These routines look for SYN, FIN and RST flags to determine when TCP 150 connections open and close. When a TCP connection closes, the data 151 structure containing packet aliasing information is deleted after 152 a timeout period. 153 */ 154 155 /* Local prototypes */ 156 static void TcpMonitorIn(struct ip *, struct alias_link *); 157 158 static void TcpMonitorOut(struct ip *, struct alias_link *); 159 160 161 static void 162 TcpMonitorIn(struct ip *pip, struct alias_link *link) 163 { 164 struct tcphdr *tc; 165 166 tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2)); 167 168 switch (GetStateIn(link)) 169 { 170 case ALIAS_TCP_STATE_NOT_CONNECTED: 171 if (tc->th_flags & TH_RST) 172 SetStateIn(link, ALIAS_TCP_STATE_DISCONNECTED); 173 else if (tc->th_flags & TH_SYN) 174 SetStateIn(link, ALIAS_TCP_STATE_CONNECTED); 175 break; 176 case ALIAS_TCP_STATE_CONNECTED: 177 if (tc->th_flags & (TH_FIN | TH_RST)) 178 SetStateIn(link, ALIAS_TCP_STATE_DISCONNECTED); 179 break; 180 } 181 } 182 183 static void 184 TcpMonitorOut(struct ip *pip, struct alias_link *link) 185 { 186 struct tcphdr *tc; 187 188 tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2)); 189 190 switch (GetStateOut(link)) 191 { 192 case ALIAS_TCP_STATE_NOT_CONNECTED: 193 if (tc->th_flags & TH_RST) 194 SetStateOut(link, ALIAS_TCP_STATE_DISCONNECTED); 195 else if (tc->th_flags & TH_SYN) 196 SetStateOut(link, ALIAS_TCP_STATE_CONNECTED); 197 break; 198 case ALIAS_TCP_STATE_CONNECTED: 199 if (tc->th_flags & (TH_FIN | TH_RST)) 200 SetStateOut(link, ALIAS_TCP_STATE_DISCONNECTED); 201 break; 202 } 203 } 204 205 206 207 208 209 /* Protocol Specific Packet Aliasing Routines 210 211 IcmpAliasIn(), IcmpAliasIn1(), IcmpAliasIn2() 212 IcmpAliasOut(), IcmpAliasOut1(), IcmpAliasOut2() 213 ProtoAliasIn(), ProtoAliasOut() 214 UdpAliasIn(), UdpAliasOut() 215 TcpAliasIn(), TcpAliasOut() 216 217 These routines handle protocol specific details of packet aliasing. 218 One may observe a certain amount of repetitive arithmetic in these 219 functions, the purpose of which is to compute a revised checksum 220 without actually summing over the entire data packet, which could be 221 unnecessarily time consuming. 222 223 The purpose of the packet aliasing routines is to replace the source 224 address of the outgoing packet and then correctly put it back for 225 any incoming packets. For TCP and UDP, ports are also re-mapped. 226 227 For ICMP echo/timestamp requests and replies, the following scheme 228 is used: the ID number is replaced by an alias for the outgoing 229 packet. 230 231 ICMP error messages are handled by looking at the IP fragment 232 in the data section of the message. 233 234 For TCP and UDP protocols, a port number is chosen for an outgoing 235 packet, and then incoming packets are identified by IP address and 236 port numbers. For TCP packets, there is additional logic in the event 237 that sequence and ACK numbers have been altered (as in the case for 238 FTP data port commands). 239 240 The port numbers used by the packet aliasing module are not true 241 ports in the Unix sense. No sockets are actually bound to ports. 242 They are more correctly thought of as placeholders. 243 244 All packets go through the aliasing mechanism, whether they come from 245 the gateway machine or other machines on a local area network. 246 */ 247 248 249 /* Local prototypes */ 250 static int IcmpAliasIn1(struct ip *); 251 static int IcmpAliasIn2(struct ip *); 252 static int IcmpAliasIn (struct ip *); 253 254 static int IcmpAliasOut1(struct ip *); 255 static int IcmpAliasOut2(struct ip *); 256 static int IcmpAliasOut (struct ip *); 257 258 static int ProtoAliasIn(struct ip *); 259 static int ProtoAliasOut(struct ip *); 260 261 static int UdpAliasOut(struct ip *); 262 static int UdpAliasIn (struct ip *); 263 264 static int TcpAliasOut(struct ip *, int); 265 static int TcpAliasIn (struct ip *); 266 267 268 static int 269 IcmpAliasIn1(struct ip *pip) 270 { 271 /* 272 De-alias incoming echo and timestamp replies. 273 Alias incoming echo and timestamp requests. 274 */ 275 struct alias_link *link; 276 struct icmp *ic; 277 278 ic = (struct icmp *) ((char *) pip + (pip->ip_hl << 2)); 279 280 /* Get source address from ICMP data field and restore original data */ 281 link = FindIcmpIn(pip->ip_src, pip->ip_dst, ic->icmp_id, 1); 282 if (link != NULL) 283 { 284 u_short original_id; 285 int accumulate; 286 287 original_id = GetOriginalPort(link); 288 289 /* Adjust ICMP checksum */ 290 accumulate = ic->icmp_id; 291 accumulate -= original_id; 292 ADJUST_CHECKSUM(accumulate, ic->icmp_cksum); 293 294 /* Put original sequence number back in */ 295 ic->icmp_id = original_id; 296 297 /* Put original address back into IP header */ 298 { 299 struct in_addr original_address; 300 301 original_address = GetOriginalAddress(link); 302 DifferentialChecksum(&pip->ip_sum, 303 (u_short *) &original_address, 304 (u_short *) &pip->ip_dst, 305 2); 306 pip->ip_dst = original_address; 307 } 308 309 return(PKT_ALIAS_OK); 310 } 311 return(PKT_ALIAS_IGNORED); 312 } 313 314 static int 315 IcmpAliasIn2(struct ip *pip) 316 { 317 /* 318 Alias incoming ICMP error messages containing 319 IP header and first 64 bits of datagram. 320 */ 321 struct ip *ip; 322 struct icmp *ic, *ic2; 323 struct udphdr *ud; 324 struct tcphdr *tc; 325 struct alias_link *link; 326 327 ic = (struct icmp *) ((char *) pip + (pip->ip_hl << 2)); 328 ip = &ic->icmp_ip; 329 330 ud = (struct udphdr *) ((char *) ip + (ip->ip_hl <<2)); 331 tc = (struct tcphdr *) ud; 332 ic2 = (struct icmp *) ud; 333 334 if (ip->ip_p == IPPROTO_UDP) 335 link = FindUdpTcpIn(ip->ip_dst, ip->ip_src, 336 ud->uh_dport, ud->uh_sport, 337 IPPROTO_UDP, 0); 338 else if (ip->ip_p == IPPROTO_TCP) 339 link = FindUdpTcpIn(ip->ip_dst, ip->ip_src, 340 tc->th_dport, tc->th_sport, 341 IPPROTO_TCP, 0); 342 else if (ip->ip_p == IPPROTO_ICMP) { 343 if (ic2->icmp_type == ICMP_ECHO || ic2->icmp_type == ICMP_TSTAMP) 344 link = FindIcmpIn(ip->ip_dst, ip->ip_src, ic2->icmp_id, 0); 345 else 346 link = NULL; 347 } else 348 link = NULL; 349 350 if (link != NULL) 351 { 352 if (ip->ip_p == IPPROTO_UDP || ip->ip_p == IPPROTO_TCP) 353 { 354 u_short *sptr; 355 int accumulate, accumulate2; 356 struct in_addr original_address; 357 u_short original_port; 358 359 original_address = GetOriginalAddress(link); 360 original_port = GetOriginalPort(link); 361 362 /* Adjust ICMP checksum */ 363 sptr = (u_short *) &(ip->ip_src); 364 accumulate = *sptr++; 365 accumulate += *sptr; 366 sptr = (u_short *) &original_address; 367 accumulate -= *sptr++; 368 accumulate -= *sptr; 369 accumulate += ud->uh_sport; 370 accumulate -= original_port; 371 accumulate2 = accumulate; 372 accumulate2 += ip->ip_sum; 373 ADJUST_CHECKSUM(accumulate, ip->ip_sum); 374 accumulate2 -= ip->ip_sum; 375 ADJUST_CHECKSUM(accumulate2, ic->icmp_cksum); 376 377 /* Un-alias address in IP header */ 378 DifferentialChecksum(&pip->ip_sum, 379 (u_short *) &original_address, 380 (u_short *) &pip->ip_dst, 381 2); 382 pip->ip_dst = original_address; 383 384 /* Un-alias address and port number of original IP packet 385 fragment contained in ICMP data section */ 386 ip->ip_src = original_address; 387 ud->uh_sport = original_port; 388 } 389 else if (ip->ip_p == IPPROTO_ICMP) 390 { 391 u_short *sptr; 392 int accumulate, accumulate2; 393 struct in_addr original_address; 394 u_short original_id; 395 396 original_address = GetOriginalAddress(link); 397 original_id = GetOriginalPort(link); 398 399 /* Adjust ICMP checksum */ 400 sptr = (u_short *) &(ip->ip_src); 401 accumulate = *sptr++; 402 accumulate += *sptr; 403 sptr = (u_short *) &original_address; 404 accumulate -= *sptr++; 405 accumulate -= *sptr; 406 accumulate += ic2->icmp_id; 407 accumulate -= original_id; 408 accumulate2 = accumulate; 409 accumulate2 += ip->ip_sum; 410 ADJUST_CHECKSUM(accumulate, ip->ip_sum); 411 accumulate2 -= ip->ip_sum; 412 ADJUST_CHECKSUM(accumulate2, ic->icmp_cksum); 413 414 /* Un-alias address in IP header */ 415 DifferentialChecksum(&pip->ip_sum, 416 (u_short *) &original_address, 417 (u_short *) &pip->ip_dst, 418 2); 419 pip->ip_dst = original_address; 420 421 /* Un-alias address of original IP packet and sequence number of 422 embedded ICMP datagram */ 423 ip->ip_src = original_address; 424 ic2->icmp_id = original_id; 425 } 426 return(PKT_ALIAS_OK); 427 } 428 return(PKT_ALIAS_IGNORED); 429 } 430 431 432 static int 433 IcmpAliasIn(struct ip *pip) 434 { 435 int iresult; 436 struct icmp *ic; 437 438 /* Return if proxy-only mode is enabled */ 439 if (packetAliasMode & PKT_ALIAS_PROXY_ONLY) 440 return PKT_ALIAS_OK; 441 442 ic = (struct icmp *) ((char *) pip + (pip->ip_hl << 2)); 443 444 iresult = PKT_ALIAS_IGNORED; 445 switch (ic->icmp_type) 446 { 447 case ICMP_ECHOREPLY: 448 case ICMP_TSTAMPREPLY: 449 if (ic->icmp_code == 0) 450 { 451 iresult = IcmpAliasIn1(pip); 452 } 453 break; 454 case ICMP_UNREACH: 455 case ICMP_SOURCEQUENCH: 456 case ICMP_TIMXCEED: 457 case ICMP_PARAMPROB: 458 iresult = IcmpAliasIn2(pip); 459 break; 460 case ICMP_ECHO: 461 case ICMP_TSTAMP: 462 iresult = IcmpAliasIn1(pip); 463 break; 464 } 465 return(iresult); 466 } 467 468 469 static int 470 IcmpAliasOut1(struct ip *pip) 471 { 472 /* 473 Alias outgoing echo and timestamp requests. 474 De-alias outgoing echo and timestamp replies. 475 */ 476 struct alias_link *link; 477 struct icmp *ic; 478 479 ic = (struct icmp *) ((char *) pip + (pip->ip_hl << 2)); 480 481 /* Save overwritten data for when echo packet returns */ 482 link = FindIcmpOut(pip->ip_src, pip->ip_dst, ic->icmp_id, 1); 483 if (link != NULL) 484 { 485 u_short alias_id; 486 int accumulate; 487 488 alias_id = GetAliasPort(link); 489 490 /* Since data field is being modified, adjust ICMP checksum */ 491 accumulate = ic->icmp_id; 492 accumulate -= alias_id; 493 ADJUST_CHECKSUM(accumulate, ic->icmp_cksum); 494 495 /* Alias sequence number */ 496 ic->icmp_id = alias_id; 497 498 /* Change source address */ 499 { 500 struct in_addr alias_address; 501 502 alias_address = GetAliasAddress(link); 503 DifferentialChecksum(&pip->ip_sum, 504 (u_short *) &alias_address, 505 (u_short *) &pip->ip_src, 506 2); 507 pip->ip_src = alias_address; 508 } 509 510 return(PKT_ALIAS_OK); 511 } 512 return(PKT_ALIAS_IGNORED); 513 } 514 515 516 static int 517 IcmpAliasOut2(struct ip *pip) 518 { 519 /* 520 Alias outgoing ICMP error messages containing 521 IP header and first 64 bits of datagram. 522 */ 523 struct ip *ip; 524 struct icmp *ic, *ic2; 525 struct udphdr *ud; 526 struct tcphdr *tc; 527 struct alias_link *link; 528 529 ic = (struct icmp *) ((char *) pip + (pip->ip_hl << 2)); 530 ip = &ic->icmp_ip; 531 532 ud = (struct udphdr *) ((char *) ip + (ip->ip_hl <<2)); 533 tc = (struct tcphdr *) ud; 534 ic2 = (struct icmp *) ud; 535 536 if (ip->ip_p == IPPROTO_UDP) 537 link = FindUdpTcpOut(ip->ip_dst, ip->ip_src, 538 ud->uh_dport, ud->uh_sport, 539 IPPROTO_UDP, 0); 540 else if (ip->ip_p == IPPROTO_TCP) 541 link = FindUdpTcpOut(ip->ip_dst, ip->ip_src, 542 tc->th_dport, tc->th_sport, 543 IPPROTO_TCP, 0); 544 else if (ip->ip_p == IPPROTO_ICMP) { 545 if (ic2->icmp_type == ICMP_ECHO || ic2->icmp_type == ICMP_TSTAMP) 546 link = FindIcmpOut(ip->ip_dst, ip->ip_src, ic2->icmp_id, 0); 547 else 548 link = NULL; 549 } else 550 link = NULL; 551 552 if (link != NULL) 553 { 554 if (ip->ip_p == IPPROTO_UDP || ip->ip_p == IPPROTO_TCP) 555 { 556 u_short *sptr; 557 int accumulate; 558 struct in_addr alias_address; 559 u_short alias_port; 560 561 alias_address = GetAliasAddress(link); 562 alias_port = GetAliasPort(link); 563 564 /* Adjust ICMP checksum */ 565 sptr = (u_short *) &(ip->ip_dst); 566 accumulate = *sptr++; 567 accumulate += *sptr; 568 sptr = (u_short *) &alias_address; 569 accumulate -= *sptr++; 570 accumulate -= *sptr; 571 accumulate += ud->uh_dport; 572 accumulate -= alias_port; 573 ADJUST_CHECKSUM(accumulate, ic->icmp_cksum); 574 575 /* 576 * Alias address in IP header if it comes from the host 577 * the original TCP/UDP packet was destined for. 578 */ 579 if (pip->ip_src.s_addr == ip->ip_dst.s_addr) { 580 DifferentialChecksum(&pip->ip_sum, 581 (u_short *) &alias_address, 582 (u_short *) &pip->ip_src, 583 2); 584 pip->ip_src = alias_address; 585 } 586 587 /* Alias address and port number of original IP packet 588 fragment contained in ICMP data section */ 589 ip->ip_dst = alias_address; 590 ud->uh_dport = alias_port; 591 } 592 else if (ip->ip_p == IPPROTO_ICMP) 593 { 594 u_short *sptr; 595 int accumulate; 596 struct in_addr alias_address; 597 u_short alias_id; 598 599 alias_address = GetAliasAddress(link); 600 alias_id = GetAliasPort(link); 601 602 /* Adjust ICMP checksum */ 603 sptr = (u_short *) &(ip->ip_dst); 604 accumulate = *sptr++; 605 accumulate += *sptr; 606 sptr = (u_short *) &alias_address; 607 accumulate -= *sptr++; 608 accumulate -= *sptr; 609 accumulate += ic2->icmp_id; 610 accumulate -= alias_id; 611 ADJUST_CHECKSUM(accumulate, ic->icmp_cksum); 612 613 /* 614 * Alias address in IP header if it comes from the host 615 * the original ICMP message was destined for. 616 */ 617 if (pip->ip_src.s_addr == ip->ip_dst.s_addr) { 618 DifferentialChecksum(&pip->ip_sum, 619 (u_short *) &alias_address, 620 (u_short *) &pip->ip_src, 621 2); 622 pip->ip_src = alias_address; 623 } 624 625 /* Alias address of original IP packet and sequence number of 626 embedded ICMP datagram */ 627 ip->ip_dst = alias_address; 628 ic2->icmp_id = alias_id; 629 } 630 return(PKT_ALIAS_OK); 631 } 632 return(PKT_ALIAS_IGNORED); 633 } 634 635 636 static int 637 IcmpAliasOut(struct ip *pip) 638 { 639 int iresult; 640 struct icmp *ic; 641 642 /* Return if proxy-only mode is enabled */ 643 if (packetAliasMode & PKT_ALIAS_PROXY_ONLY) 644 return PKT_ALIAS_OK; 645 646 ic = (struct icmp *) ((char *) pip + (pip->ip_hl << 2)); 647 648 iresult = PKT_ALIAS_IGNORED; 649 switch (ic->icmp_type) 650 { 651 case ICMP_ECHO: 652 case ICMP_TSTAMP: 653 if (ic->icmp_code == 0) 654 { 655 iresult = IcmpAliasOut1(pip); 656 } 657 break; 658 case ICMP_UNREACH: 659 case ICMP_SOURCEQUENCH: 660 case ICMP_TIMXCEED: 661 case ICMP_PARAMPROB: 662 iresult = IcmpAliasOut2(pip); 663 break; 664 case ICMP_ECHOREPLY: 665 case ICMP_TSTAMPREPLY: 666 iresult = IcmpAliasOut1(pip); 667 } 668 return(iresult); 669 } 670 671 672 673 static int 674 ProtoAliasIn(struct ip *pip) 675 { 676 /* 677 Handle incoming IP packets. The 678 only thing which is done in this case is to alias 679 the dest IP address of the packet to our inside 680 machine. 681 */ 682 struct alias_link *link; 683 684 /* Return if proxy-only mode is enabled */ 685 if (packetAliasMode & PKT_ALIAS_PROXY_ONLY) 686 return PKT_ALIAS_OK; 687 688 link = FindProtoIn(pip->ip_src, pip->ip_dst, pip->ip_p); 689 if (link != NULL) 690 { 691 struct in_addr original_address; 692 693 original_address = GetOriginalAddress(link); 694 695 /* Restore original IP address */ 696 DifferentialChecksum(&pip->ip_sum, 697 (u_short *) &original_address, 698 (u_short *) &pip->ip_dst, 699 2); 700 pip->ip_dst = original_address; 701 702 return(PKT_ALIAS_OK); 703 } 704 return(PKT_ALIAS_IGNORED); 705 } 706 707 708 static int 709 ProtoAliasOut(struct ip *pip) 710 { 711 /* 712 Handle outgoing IP packets. The 713 only thing which is done in this case is to alias 714 the source IP address of the packet. 715 */ 716 struct alias_link *link; 717 718 /* Return if proxy-only mode is enabled */ 719 if (packetAliasMode & PKT_ALIAS_PROXY_ONLY) 720 return PKT_ALIAS_OK; 721 722 link = FindProtoOut(pip->ip_src, pip->ip_dst, pip->ip_p); 723 if (link != NULL) 724 { 725 struct in_addr alias_address; 726 727 alias_address = GetAliasAddress(link); 728 729 /* Change source address */ 730 DifferentialChecksum(&pip->ip_sum, 731 (u_short *) &alias_address, 732 (u_short *) &pip->ip_src, 733 2); 734 pip->ip_src = alias_address; 735 736 return(PKT_ALIAS_OK); 737 } 738 return(PKT_ALIAS_IGNORED); 739 } 740 741 742 static int 743 UdpAliasIn(struct ip *pip) 744 { 745 struct udphdr *ud; 746 struct alias_link *link; 747 748 /* Return if proxy-only mode is enabled */ 749 if (packetAliasMode & PKT_ALIAS_PROXY_ONLY) 750 return PKT_ALIAS_OK; 751 752 ud = (struct udphdr *) ((char *) pip + (pip->ip_hl << 2)); 753 754 link = FindUdpTcpIn(pip->ip_src, pip->ip_dst, 755 ud->uh_sport, ud->uh_dport, 756 IPPROTO_UDP, 1); 757 if (link != NULL) 758 { 759 struct in_addr alias_address; 760 struct in_addr original_address; 761 u_short alias_port; 762 int accumulate; 763 u_short *sptr; 764 int r = 0; 765 766 alias_address = GetAliasAddress(link); 767 original_address = GetOriginalAddress(link); 768 alias_port = ud->uh_dport; 769 ud->uh_dport = GetOriginalPort(link); 770 771 /* Special processing for IP encoding protocols */ 772 if (ntohs(ud->uh_dport) == CUSEEME_PORT_NUMBER) 773 AliasHandleCUSeeMeIn(pip, original_address); 774 /* If NETBIOS Datagram, It should be alias address in UDP Data, too */ 775 else if (ntohs(ud->uh_dport) == NETBIOS_DGM_PORT_NUMBER 776 || ntohs(ud->uh_sport) == NETBIOS_DGM_PORT_NUMBER) 777 r = AliasHandleUdpNbt(pip, link, &original_address, ud->uh_dport); 778 else if (ntohs(ud->uh_dport) == NETBIOS_NS_PORT_NUMBER 779 || ntohs(ud->uh_sport) == NETBIOS_NS_PORT_NUMBER) 780 r = AliasHandleUdpNbtNS(pip, link, &alias_address, &alias_port, 781 &original_address, &ud->uh_dport); 782 783 /* If UDP checksum is not zero, then adjust since destination port */ 784 /* is being unaliased and destination address is being altered. */ 785 if (ud->uh_sum != 0) 786 { 787 accumulate = alias_port; 788 accumulate -= ud->uh_dport; 789 sptr = (u_short *) &alias_address; 790 accumulate += *sptr++; 791 accumulate += *sptr; 792 sptr = (u_short *) &original_address; 793 accumulate -= *sptr++; 794 accumulate -= *sptr; 795 ADJUST_CHECKSUM(accumulate, ud->uh_sum); 796 } 797 798 /* Restore original IP address */ 799 DifferentialChecksum(&pip->ip_sum, 800 (u_short *) &original_address, 801 (u_short *) &pip->ip_dst, 802 2); 803 pip->ip_dst = original_address; 804 805 /* 806 * If we cannot figure out the packet, ignore it. 807 */ 808 if (r < 0) 809 return(PKT_ALIAS_IGNORED); 810 else 811 return(PKT_ALIAS_OK); 812 } 813 return(PKT_ALIAS_IGNORED); 814 } 815 816 static int 817 UdpAliasOut(struct ip *pip) 818 { 819 struct udphdr *ud; 820 struct alias_link *link; 821 822 /* Return if proxy-only mode is enabled */ 823 if (packetAliasMode & PKT_ALIAS_PROXY_ONLY) 824 return PKT_ALIAS_OK; 825 826 ud = (struct udphdr *) ((char *) pip + (pip->ip_hl << 2)); 827 828 link = FindUdpTcpOut(pip->ip_src, pip->ip_dst, 829 ud->uh_sport, ud->uh_dport, 830 IPPROTO_UDP, 1); 831 if (link != NULL) 832 { 833 u_short alias_port; 834 struct in_addr alias_address; 835 836 alias_address = GetAliasAddress(link); 837 alias_port = GetAliasPort(link); 838 839 /* Special processing for IP encoding protocols */ 840 if (ntohs(ud->uh_dport) == CUSEEME_PORT_NUMBER) 841 AliasHandleCUSeeMeOut(pip, link); 842 /* If NETBIOS Datagram, It should be alias address in UDP Data, too */ 843 else if (ntohs(ud->uh_dport) == NETBIOS_DGM_PORT_NUMBER 844 || ntohs(ud->uh_sport) == NETBIOS_DGM_PORT_NUMBER) 845 AliasHandleUdpNbt(pip, link, &alias_address, alias_port); 846 else if (ntohs(ud->uh_dport) == NETBIOS_NS_PORT_NUMBER 847 || ntohs(ud->uh_sport) == NETBIOS_NS_PORT_NUMBER) 848 AliasHandleUdpNbtNS(pip, link, &pip->ip_src, &ud->uh_sport, 849 &alias_address, &alias_port); 850 /* 851 * We don't know in advance what TID the TFTP server will choose, 852 * so we create a wilcard link (destination port is unspecified) 853 * that will match any TID from a given destination. 854 */ 855 else if (ntohs(ud->uh_dport) == TFTP_PORT_NUMBER) 856 FindRtspOut(pip->ip_src, pip->ip_dst, 857 ud->uh_sport, alias_port, IPPROTO_UDP); 858 859 /* If UDP checksum is not zero, adjust since source port is */ 860 /* being aliased and source address is being altered */ 861 if (ud->uh_sum != 0) 862 { 863 int accumulate; 864 u_short *sptr; 865 866 accumulate = ud->uh_sport; 867 accumulate -= alias_port; 868 sptr = (u_short *) &(pip->ip_src); 869 accumulate += *sptr++; 870 accumulate += *sptr; 871 sptr = (u_short *) &alias_address; 872 accumulate -= *sptr++; 873 accumulate -= *sptr; 874 ADJUST_CHECKSUM(accumulate, ud->uh_sum); 875 } 876 877 /* Put alias port in UDP header */ 878 ud->uh_sport = alias_port; 879 880 /* Change source address */ 881 DifferentialChecksum(&pip->ip_sum, 882 (u_short *) &alias_address, 883 (u_short *) &pip->ip_src, 884 2); 885 pip->ip_src = alias_address; 886 887 return(PKT_ALIAS_OK); 888 } 889 return(PKT_ALIAS_IGNORED); 890 } 891 892 893 894 static int 895 TcpAliasIn(struct ip *pip) 896 { 897 struct tcphdr *tc; 898 struct alias_link *link; 899 900 tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2)); 901 902 link = FindUdpTcpIn(pip->ip_src, pip->ip_dst, 903 tc->th_sport, tc->th_dport, 904 IPPROTO_TCP, 905 !(packetAliasMode & PKT_ALIAS_PROXY_ONLY)); 906 if (link != NULL) 907 { 908 struct in_addr alias_address; 909 struct in_addr original_address; 910 struct in_addr proxy_address; 911 u_short alias_port; 912 u_short proxy_port; 913 int accumulate; 914 u_short *sptr; 915 916 /* Special processing for IP encoding protocols */ 917 if (ntohs(tc->th_dport) == PPTP_CONTROL_PORT_NUMBER 918 || ntohs(tc->th_sport) == PPTP_CONTROL_PORT_NUMBER) 919 AliasHandlePptpIn(pip, link); 920 else if (skinnyPort != 0 && (ntohs(tc->th_dport) == skinnyPort 921 || ntohs(tc->th_sport) == skinnyPort)) 922 AliasHandleSkinny(pip, link); 923 924 alias_address = GetAliasAddress(link); 925 original_address = GetOriginalAddress(link); 926 proxy_address = GetProxyAddress(link); 927 alias_port = tc->th_dport; 928 tc->th_dport = GetOriginalPort(link); 929 proxy_port = GetProxyPort(link); 930 931 /* Adjust TCP checksum since destination port is being unaliased */ 932 /* and destination port is being altered. */ 933 accumulate = alias_port; 934 accumulate -= tc->th_dport; 935 sptr = (u_short *) &alias_address; 936 accumulate += *sptr++; 937 accumulate += *sptr; 938 sptr = (u_short *) &original_address; 939 accumulate -= *sptr++; 940 accumulate -= *sptr; 941 942 /* If this is a proxy, then modify the TCP source port and 943 checksum accumulation */ 944 if (proxy_port != 0) 945 { 946 accumulate += tc->th_sport; 947 tc->th_sport = proxy_port; 948 accumulate -= tc->th_sport; 949 950 sptr = (u_short *) &pip->ip_src; 951 accumulate += *sptr++; 952 accumulate += *sptr; 953 sptr = (u_short *) &proxy_address; 954 accumulate -= *sptr++; 955 accumulate -= *sptr; 956 } 957 958 /* See if ACK number needs to be modified */ 959 if (GetAckModified(link) == 1) 960 { 961 int delta; 962 963 delta = GetDeltaAckIn(pip, link); 964 if (delta != 0) 965 { 966 sptr = (u_short *) &tc->th_ack; 967 accumulate += *sptr++; 968 accumulate += *sptr; 969 tc->th_ack = htonl(ntohl(tc->th_ack) - delta); 970 sptr = (u_short *) &tc->th_ack; 971 accumulate -= *sptr++; 972 accumulate -= *sptr; 973 } 974 } 975 976 ADJUST_CHECKSUM(accumulate, tc->th_sum); 977 978 /* Restore original IP address */ 979 sptr = (u_short *) &pip->ip_dst; 980 accumulate = *sptr++; 981 accumulate += *sptr; 982 pip->ip_dst = original_address; 983 sptr = (u_short *) &pip->ip_dst; 984 accumulate -= *sptr++; 985 accumulate -= *sptr; 986 987 /* If this is a transparent proxy packet, then modify the source 988 address */ 989 if (proxy_address.s_addr != 0) 990 { 991 sptr = (u_short *) &pip->ip_src; 992 accumulate += *sptr++; 993 accumulate += *sptr; 994 pip->ip_src = proxy_address; 995 sptr = (u_short *) &pip->ip_src; 996 accumulate -= *sptr++; 997 accumulate -= *sptr; 998 } 999 1000 ADJUST_CHECKSUM(accumulate, pip->ip_sum); 1001 1002 /* Monitor TCP connection state */ 1003 TcpMonitorIn(pip, link); 1004 1005 return(PKT_ALIAS_OK); 1006 } 1007 return(PKT_ALIAS_IGNORED); 1008 } 1009 1010 static int 1011 TcpAliasOut(struct ip *pip, int maxpacketsize) 1012 { 1013 int proxy_type; 1014 u_short dest_port; 1015 u_short proxy_server_port; 1016 struct in_addr dest_address; 1017 struct in_addr proxy_server_address; 1018 struct tcphdr *tc; 1019 struct alias_link *link; 1020 1021 tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2)); 1022 1023 proxy_type = ProxyCheck(pip, &proxy_server_address, &proxy_server_port); 1024 1025 if (proxy_type == 0 && (packetAliasMode & PKT_ALIAS_PROXY_ONLY)) 1026 return PKT_ALIAS_OK; 1027 1028 /* If this is a transparent proxy, save original destination, 1029 then alter the destination and adjust checksums */ 1030 dest_port = tc->th_dport; 1031 dest_address = pip->ip_dst; 1032 if (proxy_type != 0) 1033 { 1034 int accumulate; 1035 u_short *sptr; 1036 1037 accumulate = tc->th_dport; 1038 tc->th_dport = proxy_server_port; 1039 accumulate -= tc->th_dport; 1040 1041 sptr = (u_short *) &(pip->ip_dst); 1042 accumulate += *sptr++; 1043 accumulate += *sptr; 1044 sptr = (u_short *) &proxy_server_address; 1045 accumulate -= *sptr++; 1046 accumulate -= *sptr; 1047 1048 ADJUST_CHECKSUM(accumulate, tc->th_sum); 1049 1050 sptr = (u_short *) &(pip->ip_dst); 1051 accumulate = *sptr++; 1052 accumulate += *sptr; 1053 pip->ip_dst = proxy_server_address; 1054 sptr = (u_short *) &(pip->ip_dst); 1055 accumulate -= *sptr++; 1056 accumulate -= *sptr; 1057 1058 ADJUST_CHECKSUM(accumulate, pip->ip_sum); 1059 } 1060 1061 link = FindUdpTcpOut(pip->ip_src, pip->ip_dst, 1062 tc->th_sport, tc->th_dport, 1063 IPPROTO_TCP, 1); 1064 if (link !=NULL) 1065 { 1066 u_short alias_port; 1067 struct in_addr alias_address; 1068 int accumulate; 1069 u_short *sptr; 1070 1071 /* Save original destination address, if this is a proxy packet. 1072 Also modify packet to include destination encoding. This may 1073 change the size of IP header. */ 1074 if (proxy_type != 0) 1075 { 1076 SetProxyPort(link, dest_port); 1077 SetProxyAddress(link, dest_address); 1078 ProxyModify(link, pip, maxpacketsize, proxy_type); 1079 tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2)); 1080 } 1081 1082 /* Get alias address and port */ 1083 alias_port = GetAliasPort(link); 1084 alias_address = GetAliasAddress(link); 1085 1086 /* Monitor TCP connection state */ 1087 TcpMonitorOut(pip, link); 1088 1089 /* Special processing for IP encoding protocols */ 1090 if (ntohs(tc->th_dport) == FTP_CONTROL_PORT_NUMBER 1091 || ntohs(tc->th_sport) == FTP_CONTROL_PORT_NUMBER) 1092 AliasHandleFtpOut(pip, link, maxpacketsize); 1093 else if (ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_1 1094 || ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_2) 1095 AliasHandleIrcOut(pip, link, maxpacketsize); 1096 else if (ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_1 1097 || ntohs(tc->th_sport) == RTSP_CONTROL_PORT_NUMBER_1 1098 || ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_2 1099 || ntohs(tc->th_sport) == RTSP_CONTROL_PORT_NUMBER_2) 1100 AliasHandleRtspOut(pip, link, maxpacketsize); 1101 else if (ntohs(tc->th_dport) == PPTP_CONTROL_PORT_NUMBER 1102 || ntohs(tc->th_sport) == PPTP_CONTROL_PORT_NUMBER) 1103 AliasHandlePptpOut(pip, link); 1104 else if (skinnyPort != 0 && (ntohs(tc->th_sport) == skinnyPort 1105 || ntohs(tc->th_dport) == skinnyPort)) 1106 AliasHandleSkinny(pip, link); 1107 1108 /* Adjust TCP checksum since source port is being aliased */ 1109 /* and source address is being altered */ 1110 accumulate = tc->th_sport; 1111 tc->th_sport = alias_port; 1112 accumulate -= tc->th_sport; 1113 1114 sptr = (u_short *) &(pip->ip_src); 1115 accumulate += *sptr++; 1116 accumulate += *sptr; 1117 sptr = (u_short *) &alias_address; 1118 accumulate -= *sptr++; 1119 accumulate -= *sptr; 1120 1121 /* Modify sequence number if necessary */ 1122 if (GetAckModified(link) == 1) 1123 { 1124 int delta; 1125 1126 delta = GetDeltaSeqOut(pip, link); 1127 if (delta != 0) 1128 { 1129 sptr = (u_short *) &tc->th_seq; 1130 accumulate += *sptr++; 1131 accumulate += *sptr; 1132 tc->th_seq = htonl(ntohl(tc->th_seq) + delta); 1133 sptr = (u_short *) &tc->th_seq; 1134 accumulate -= *sptr++; 1135 accumulate -= *sptr; 1136 } 1137 } 1138 1139 ADJUST_CHECKSUM(accumulate, tc->th_sum); 1140 1141 /* Change source address */ 1142 sptr = (u_short *) &(pip->ip_src); 1143 accumulate = *sptr++; 1144 accumulate += *sptr; 1145 pip->ip_src = alias_address; 1146 sptr = (u_short *) &(pip->ip_src); 1147 accumulate -= *sptr++; 1148 accumulate -= *sptr; 1149 1150 ADJUST_CHECKSUM(accumulate, pip->ip_sum); 1151 1152 return(PKT_ALIAS_OK); 1153 } 1154 return(PKT_ALIAS_IGNORED); 1155 } 1156 1157 1158 1159 1160 /* Fragment Handling 1161 1162 FragmentIn() 1163 FragmentOut() 1164 1165 The packet aliasing module has a limited ability for handling IP 1166 fragments. If the ICMP, TCP or UDP header is in the first fragment 1167 received, then the ID number of the IP packet is saved, and other 1168 fragments are identified according to their ID number and IP address 1169 they were sent from. Pointers to unresolved fragments can also be 1170 saved and recalled when a header fragment is seen. 1171 */ 1172 1173 /* Local prototypes */ 1174 static int FragmentIn(struct ip *); 1175 static int FragmentOut(struct ip *); 1176 1177 1178 static int 1179 FragmentIn(struct ip *pip) 1180 { 1181 struct alias_link *link; 1182 1183 link = FindFragmentIn2(pip->ip_src, pip->ip_dst, pip->ip_id); 1184 if (link != NULL) 1185 { 1186 struct in_addr original_address; 1187 1188 GetFragmentAddr(link, &original_address); 1189 DifferentialChecksum(&pip->ip_sum, 1190 (u_short *) &original_address, 1191 (u_short *) &pip->ip_dst, 1192 2); 1193 pip->ip_dst = original_address; 1194 1195 return(PKT_ALIAS_OK); 1196 } 1197 return(PKT_ALIAS_UNRESOLVED_FRAGMENT); 1198 } 1199 1200 1201 static int 1202 FragmentOut(struct ip *pip) 1203 { 1204 struct in_addr alias_address; 1205 1206 alias_address = FindAliasAddress(pip->ip_src); 1207 DifferentialChecksum(&pip->ip_sum, 1208 (u_short *) &alias_address, 1209 (u_short *) &pip->ip_src, 1210 2); 1211 pip->ip_src = alias_address; 1212 1213 return(PKT_ALIAS_OK); 1214 } 1215 1216 1217 1218 1219 1220 1221 /* Outside World Access 1222 1223 PacketAliasSaveFragment() 1224 PacketAliasGetFragment() 1225 PacketAliasFragmentIn() 1226 PacketAliasIn() 1227 PacketAliasOut() 1228 PacketUnaliasOut() 1229 1230 (prototypes in alias.h) 1231 */ 1232 1233 1234 int 1235 PacketAliasSaveFragment(char *ptr) 1236 { 1237 int iresult; 1238 struct alias_link *link; 1239 struct ip *pip; 1240 1241 pip = (struct ip *) ptr; 1242 link = AddFragmentPtrLink(pip->ip_src, pip->ip_id); 1243 iresult = PKT_ALIAS_ERROR; 1244 if (link != NULL) 1245 { 1246 SetFragmentPtr(link, ptr); 1247 iresult = PKT_ALIAS_OK; 1248 } 1249 return(iresult); 1250 } 1251 1252 1253 char * 1254 PacketAliasGetFragment(char *ptr) 1255 { 1256 struct alias_link *link; 1257 char *fptr; 1258 struct ip *pip; 1259 1260 pip = (struct ip *) ptr; 1261 link = FindFragmentPtr(pip->ip_src, pip->ip_id); 1262 if (link != NULL) 1263 { 1264 GetFragmentPtr(link, &fptr); 1265 SetFragmentPtr(link, NULL); 1266 SetExpire(link, 0); /* Deletes link */ 1267 1268 return(fptr); 1269 } 1270 else 1271 { 1272 return(NULL); 1273 } 1274 } 1275 1276 1277 void 1278 PacketAliasFragmentIn(char *ptr, /* Points to correctly de-aliased 1279 header fragment */ 1280 char *ptr_fragment /* Points to fragment which must 1281 be de-aliased */ 1282 ) 1283 { 1284 struct ip *pip; 1285 struct ip *fpip; 1286 1287 pip = (struct ip *) ptr; 1288 fpip = (struct ip *) ptr_fragment; 1289 1290 DifferentialChecksum(&fpip->ip_sum, 1291 (u_short *) &pip->ip_dst, 1292 (u_short *) &fpip->ip_dst, 1293 2); 1294 fpip->ip_dst = pip->ip_dst; 1295 } 1296 1297 1298 int 1299 PacketAliasIn(char *ptr, int maxpacketsize) 1300 { 1301 struct in_addr alias_addr; 1302 struct ip *pip; 1303 int iresult; 1304 1305 if (packetAliasMode & PKT_ALIAS_REVERSE) { 1306 packetAliasMode &= ~PKT_ALIAS_REVERSE; 1307 iresult = PacketAliasOut(ptr, maxpacketsize); 1308 packetAliasMode |= PKT_ALIAS_REVERSE; 1309 return iresult; 1310 } 1311 1312 HouseKeeping(); 1313 ClearCheckNewLink(); 1314 pip = (struct ip *) ptr; 1315 alias_addr = pip->ip_dst; 1316 1317 /* Defense against mangled packets */ 1318 if (ntohs(pip->ip_len) > maxpacketsize 1319 || (pip->ip_hl<<2) > maxpacketsize) 1320 return PKT_ALIAS_IGNORED; 1321 1322 iresult = PKT_ALIAS_IGNORED; 1323 if ( (ntohs(pip->ip_off) & IP_OFFMASK) == 0 ) 1324 { 1325 switch (pip->ip_p) 1326 { 1327 case IPPROTO_ICMP: 1328 iresult = IcmpAliasIn(pip); 1329 break; 1330 case IPPROTO_UDP: 1331 iresult = UdpAliasIn(pip); 1332 break; 1333 case IPPROTO_TCP: 1334 iresult = TcpAliasIn(pip); 1335 break; 1336 case IPPROTO_GRE: 1337 if (packetAliasMode & PKT_ALIAS_PROXY_ONLY || 1338 AliasHandlePptpGreIn(pip) == 0) 1339 iresult = PKT_ALIAS_OK; 1340 else 1341 iresult = ProtoAliasIn(pip); 1342 break; 1343 default: 1344 iresult = ProtoAliasIn(pip); 1345 break; 1346 } 1347 1348 if (ntohs(pip->ip_off) & IP_MF) 1349 { 1350 struct alias_link *link; 1351 1352 link = FindFragmentIn1(pip->ip_src, alias_addr, pip->ip_id); 1353 if (link != NULL) 1354 { 1355 iresult = PKT_ALIAS_FOUND_HEADER_FRAGMENT; 1356 SetFragmentAddr(link, pip->ip_dst); 1357 } 1358 else 1359 { 1360 iresult = PKT_ALIAS_ERROR; 1361 } 1362 } 1363 } 1364 else 1365 { 1366 iresult = FragmentIn(pip); 1367 } 1368 1369 return(iresult); 1370 } 1371 1372 1373 1374 /* Unregistered address ranges */ 1375 1376 /* 10.0.0.0 -> 10.255.255.255 */ 1377 #define UNREG_ADDR_A_LOWER 0x0a000000 1378 #define UNREG_ADDR_A_UPPER 0x0affffff 1379 1380 /* 172.16.0.0 -> 172.31.255.255 */ 1381 #define UNREG_ADDR_B_LOWER 0xac100000 1382 #define UNREG_ADDR_B_UPPER 0xac1fffff 1383 1384 /* 192.168.0.0 -> 192.168.255.255 */ 1385 #define UNREG_ADDR_C_LOWER 0xc0a80000 1386 #define UNREG_ADDR_C_UPPER 0xc0a8ffff 1387 1388 int 1389 PacketAliasOut(char *ptr, /* valid IP packet */ 1390 int maxpacketsize /* How much the packet data may grow 1391 (FTP and IRC inline changes) */ 1392 ) 1393 { 1394 int iresult; 1395 struct in_addr addr_save; 1396 struct ip *pip; 1397 1398 if (packetAliasMode & PKT_ALIAS_REVERSE) { 1399 packetAliasMode &= ~PKT_ALIAS_REVERSE; 1400 iresult = PacketAliasIn(ptr, maxpacketsize); 1401 packetAliasMode |= PKT_ALIAS_REVERSE; 1402 return iresult; 1403 } 1404 1405 HouseKeeping(); 1406 ClearCheckNewLink(); 1407 pip = (struct ip *) ptr; 1408 1409 /* Defense against mangled packets */ 1410 if (ntohs(pip->ip_len) > maxpacketsize 1411 || (pip->ip_hl<<2) > maxpacketsize) 1412 return PKT_ALIAS_IGNORED; 1413 1414 addr_save = GetDefaultAliasAddress(); 1415 if (packetAliasMode & PKT_ALIAS_UNREGISTERED_ONLY) 1416 { 1417 u_long addr; 1418 int iclass; 1419 1420 iclass = 0; 1421 addr = ntohl(pip->ip_src.s_addr); 1422 if (addr >= UNREG_ADDR_C_LOWER && addr <= UNREG_ADDR_C_UPPER) 1423 iclass = 3; 1424 else if (addr >= UNREG_ADDR_B_LOWER && addr <= UNREG_ADDR_B_UPPER) 1425 iclass = 2; 1426 else if (addr >= UNREG_ADDR_A_LOWER && addr <= UNREG_ADDR_A_UPPER) 1427 iclass = 1; 1428 1429 if (iclass == 0) 1430 { 1431 SetDefaultAliasAddress(pip->ip_src); 1432 } 1433 } 1434 else if (packetAliasMode & PKT_ALIAS_PROXY_ONLY) 1435 { 1436 SetDefaultAliasAddress(pip->ip_src); 1437 } 1438 1439 iresult = PKT_ALIAS_IGNORED; 1440 if ((ntohs(pip->ip_off) & IP_OFFMASK) == 0) 1441 { 1442 switch (pip->ip_p) 1443 { 1444 case IPPROTO_ICMP: 1445 iresult = IcmpAliasOut(pip); 1446 break; 1447 case IPPROTO_UDP: 1448 iresult = UdpAliasOut(pip); 1449 break; 1450 case IPPROTO_TCP: 1451 iresult = TcpAliasOut(pip, maxpacketsize); 1452 break; 1453 case IPPROTO_GRE: 1454 if (AliasHandlePptpGreOut(pip) == 0) 1455 iresult = PKT_ALIAS_OK; 1456 else 1457 iresult = ProtoAliasOut(pip); 1458 break; 1459 default: 1460 iresult = ProtoAliasOut(pip); 1461 break; 1462 } 1463 } 1464 else 1465 { 1466 iresult = FragmentOut(pip); 1467 } 1468 1469 SetDefaultAliasAddress(addr_save); 1470 return(iresult); 1471 } 1472 1473 int 1474 PacketUnaliasOut(char *ptr, /* valid IP packet */ 1475 int maxpacketsize /* for error checking */ 1476 ) 1477 { 1478 struct ip *pip; 1479 struct icmp *ic; 1480 struct udphdr *ud; 1481 struct tcphdr *tc; 1482 struct alias_link *link; 1483 int iresult = PKT_ALIAS_IGNORED; 1484 1485 pip = (struct ip *) ptr; 1486 1487 /* Defense against mangled packets */ 1488 if (ntohs(pip->ip_len) > maxpacketsize 1489 || (pip->ip_hl<<2) > maxpacketsize) 1490 return(iresult); 1491 1492 ud = (struct udphdr *) ((char *) pip + (pip->ip_hl << 2)); 1493 tc = (struct tcphdr *) ud; 1494 ic = (struct icmp *) ud; 1495 1496 /* Find a link */ 1497 if (pip->ip_p == IPPROTO_UDP) 1498 link = FindUdpTcpIn(pip->ip_dst, pip->ip_src, 1499 ud->uh_dport, ud->uh_sport, 1500 IPPROTO_UDP, 0); 1501 else if (pip->ip_p == IPPROTO_TCP) 1502 link = FindUdpTcpIn(pip->ip_dst, pip->ip_src, 1503 tc->th_dport, tc->th_sport, 1504 IPPROTO_TCP, 0); 1505 else if (pip->ip_p == IPPROTO_ICMP) 1506 link = FindIcmpIn(pip->ip_dst, pip->ip_src, ic->icmp_id, 0); 1507 else 1508 link = NULL; 1509 1510 /* Change it from an aliased packet to an unaliased packet */ 1511 if (link != NULL) 1512 { 1513 if (pip->ip_p == IPPROTO_UDP || pip->ip_p == IPPROTO_TCP) 1514 { 1515 u_short *sptr; 1516 int accumulate; 1517 struct in_addr original_address; 1518 u_short original_port; 1519 1520 original_address = GetOriginalAddress(link); 1521 original_port = GetOriginalPort(link); 1522 1523 /* Adjust TCP/UDP checksum */ 1524 sptr = (u_short *) &(pip->ip_src); 1525 accumulate = *sptr++; 1526 accumulate += *sptr; 1527 sptr = (u_short *) &original_address; 1528 accumulate -= *sptr++; 1529 accumulate -= *sptr; 1530 1531 if (pip->ip_p == IPPROTO_UDP) { 1532 accumulate += ud->uh_sport; 1533 accumulate -= original_port; 1534 ADJUST_CHECKSUM(accumulate, ud->uh_sum); 1535 } else { 1536 accumulate += tc->th_sport; 1537 accumulate -= original_port; 1538 ADJUST_CHECKSUM(accumulate, tc->th_sum); 1539 } 1540 1541 /* Adjust IP checksum */ 1542 DifferentialChecksum(&pip->ip_sum, 1543 (u_short *) &original_address, 1544 (u_short *) &pip->ip_src, 1545 2); 1546 1547 /* Un-alias source address and port number */ 1548 pip->ip_src = original_address; 1549 if (pip->ip_p == IPPROTO_UDP) 1550 ud->uh_sport = original_port; 1551 else 1552 tc->th_sport = original_port; 1553 1554 iresult = PKT_ALIAS_OK; 1555 1556 } else if (pip->ip_p == IPPROTO_ICMP) { 1557 1558 u_short *sptr; 1559 int accumulate; 1560 struct in_addr original_address; 1561 u_short original_id; 1562 1563 original_address = GetOriginalAddress(link); 1564 original_id = GetOriginalPort(link); 1565 1566 /* Adjust ICMP checksum */ 1567 sptr = (u_short *) &(pip->ip_src); 1568 accumulate = *sptr++; 1569 accumulate += *sptr; 1570 sptr = (u_short *) &original_address; 1571 accumulate -= *sptr++; 1572 accumulate -= *sptr; 1573 accumulate += ic->icmp_id; 1574 accumulate -= original_id; 1575 ADJUST_CHECKSUM(accumulate, ic->icmp_cksum); 1576 1577 /* Adjust IP checksum */ 1578 DifferentialChecksum(&pip->ip_sum, 1579 (u_short *) &original_address, 1580 (u_short *) &pip->ip_src, 1581 2); 1582 1583 /* Un-alias source address and port number */ 1584 pip->ip_src = original_address; 1585 ic->icmp_id = original_id; 1586 1587 iresult = PKT_ALIAS_OK; 1588 } 1589 } 1590 return(iresult); 1591 1592 } 1593