clientname.c

   1 /*
   2  * Functions for looking up the remote name or addr of a socket.
   3  *
   4  * Copyright (C) 1992-2001 Andrew Tridgell <tridge@samba.org>
   5  * Copyright (C) 2001, 2002 Martin Pool <mbp@samba.org>
   6  * Copyright (C) 2002-2020 Wayne Davison
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 3 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, visit the http://fsf.org website.
  20  */
  21
  22 /*
  23  * This file is now converted to use the new-style getaddrinfo()
  24  * interface, which supports IPv6 but is also supported on recent
  25  * IPv4-only machines.  On systems that don't have that interface, we
  26  * emulate it using the KAME implementation.
  27  */
  28
  29 #include "rsync.h"
  30 #include "itypes.h"
  31
  32 extern int am_daemon;
  33
  34 static const char default_name[] = "UNKNOWN";
  35 static const char proxyv2sig[] = "\r\n\r\n\0\r\nQUIT\n";
  36
  37 static char ipaddr_buf[100];
  38
  39 #define PROXY_V2_SIG_SIZE ((int)sizeof proxyv2sig - 1)
  40 #define PROXY_V2_HEADER_SIZE (PROXY_V2_SIG_SIZE + 1 + 1 + 2)
  41
  42 #define CMD_LOCAL 0
  43 #define CMD_PROXY 1
  44
  45 #define PROXY_FAM_TCPv4 0x11
  46 #define PROXY_FAM_TCPv6 0x21
  47
  48 #define GET_SOCKADDR_FAMILY(ss) ((struct sockaddr*)ss)->sa_family
  49
  50 static void client_sockaddr(int fd, struct sockaddr_storage *ss, socklen_t *ss_len);
  51 static int check_name(const char *ipaddr, const struct sockaddr_storage *ss, char *name_buf, size_t name_buf_size);
  52 static int valid_ipaddr(const char *s);
  53
  54 /* Return the IP addr of the client as a string. */
  55 char *client_addr(int fd)
  56 {
  57         struct sockaddr_storage ss;
  58         socklen_t length = sizeof ss;
  59
  60         if (*ipaddr_buf)
  61                 return ipaddr_buf;
  62
  63         if (am_daemon < 0) {    /* daemon over --rsh mode */
  64                 char *env_str;
  65                 strlcpy(ipaddr_buf, "0.0.0.0", sizeof ipaddr_buf);
  66                 if ((env_str = getenv("REMOTE_HOST")) != NULL
  67                  || (env_str = getenv("SSH_CONNECTION")) != NULL
  68                  || (env_str = getenv("SSH_CLIENT")) != NULL
  69                  || (env_str = getenv("SSH2_CLIENT")) != NULL) {
  70                         char *p;
  71                         strlcpy(ipaddr_buf, env_str, sizeof ipaddr_buf);
  72                         /* Truncate the value to just the IP address. */
  73                         if ((p = strchr(ipaddr_buf, ' ')) != NULL)
  74                                 *p = '\0';
  75                 }
  76                 if (valid_ipaddr(ipaddr_buf))
  77                         return ipaddr_buf;
  78         }
  79
  80         client_sockaddr(fd, &ss, &length);
  81         getnameinfo((struct sockaddr *)&ss, length, ipaddr_buf, sizeof ipaddr_buf, NULL, 0, NI_NUMERICHOST);
  82
  83         return ipaddr_buf;
  84 }
  85
  86
  87 /**
  88  * Return the DNS name of the client.
  89  *
  90  * The name is statically cached so that repeated lookups are quick,
  91  * so there is a limit of one lookup per customer.
  92  *
  93  * If anything goes wrong, including the name->addr->name check, then
  94  * we just use "UNKNOWN", so you can use that value in hosts allow
  95  * lines.
  96  *
  97  * After translation from sockaddr to name we do a forward lookup to
  98  * make sure nobody is spoofing PTR records.
  99  **/
 100 char *client_name(const char *ipaddr)
 101 {
 102         static char name_buf[100];
 103         char port_buf[100];
 104         struct sockaddr_storage ss;
 105         socklen_t ss_len;
 106         struct addrinfo hint, *answer;
 107         int err;
 108
 109         if (*name_buf)
 110                 return name_buf;
 111
 112         strlcpy(name_buf, default_name, sizeof name_buf);
 113
 114         if (strcmp(ipaddr, "0.0.0.0") == 0)
 115                 return name_buf;
 116
 117         memset(&ss, 0, sizeof ss);
 118         memset(&hint, 0, sizeof hint);
 119
 120 #ifdef AI_NUMERICHOST
 121         hint.ai_flags = AI_NUMERICHOST;
 122 #endif
 123         hint.ai_socktype = SOCK_STREAM;
 124
 125         if ((err = getaddrinfo(ipaddr, NULL, &hint, &answer)) != 0) {
 126                 rprintf(FLOG, "malformed address %s: %s\n", ipaddr, gai_strerror(err));
 127                 return name_buf;
 128         }
 129
 130         switch (answer->ai_family) {
 131         case AF_INET:
 132                 ss_len = sizeof (struct sockaddr_in);
 133                 memcpy(&ss, answer->ai_addr, ss_len);
 134                 break;
 135 #ifdef INET6
 136         case AF_INET6:
 137                 ss_len = sizeof (struct sockaddr_in6);
 138                 memcpy(&ss, answer->ai_addr, ss_len);
 139                 break;
 140 #endif
 141         default:
 142                 assert(0);
 143         }
 144         freeaddrinfo(answer);
 145
 146         /* reverse lookup */
 147         err = getnameinfo((struct sockaddr*)&ss, ss_len, name_buf, sizeof name_buf,
 148                           port_buf, sizeof port_buf, NI_NAMEREQD | NI_NUMERICSERV);
 149         if (err) {
 150                 strlcpy(name_buf, default_name, sizeof name_buf);
 151                 rprintf(FLOG, "name lookup failed for %s: %s\n", ipaddr, gai_strerror(err));
 152         } else
 153                 check_name(ipaddr, &ss, name_buf, sizeof name_buf);
 154
 155         return name_buf;
 156 }
 157
 158
 159 /* Try to read an proxy protocol header (V1 or V2). Returns 1 on success or 0 on failure. */
 160 int read_proxy_protocol_header(int fd)
 161 {
 162         union {
 163                 struct {
 164                         char line[108];
 165                 } v1;
 166                 struct {
 167                         char sig[PROXY_V2_SIG_SIZE];
 168                         char ver_cmd;
 169                         char fam;
 170                         char len[2];
 171                         union {
 172                                 struct {
 173                                         char src_addr[4];
 174                                         char dst_addr[4];
 175                                         char src_port[2];
 176                                         char dst_port[2];
 177                                 } ip4;
 178                                 struct {
 179                                         char src_addr[16];
 180                                         char dst_addr[16];
 181                                         char src_port[2];
 182                                         char dst_port[2];
 183                                 } ip6;
 184                                 struct {
 185                                         char src_addr[108];
 186                                         char dst_addr[108];
 187                                 } unx;
 188                         } addr;
 189                 } v2;
 190         } hdr;
 191
 192         read_buf(fd, (char*)&hdr, PROXY_V2_SIG_SIZE);
 193
 194         if (memcmp(hdr.v2.sig, proxyv2sig, PROXY_V2_SIG_SIZE) == 0) { /* Proxy V2 */
 195                 int ver, cmd, size;
 196
 197                 read_buf(fd, (char*)&hdr + PROXY_V2_SIG_SIZE, PROXY_V2_HEADER_SIZE - PROXY_V2_SIG_SIZE);
 198
 199                 ver = (hdr.v2.ver_cmd & 0xf0) >> 4;
 200                 cmd = (hdr.v2.ver_cmd & 0x0f);
 201                 size = (hdr.v2.len[0] << 8) + hdr.v2.len[1];
 202
 203                 if (ver != 2 || size + PROXY_V2_HEADER_SIZE > (int)sizeof hdr)
 204                         return 0;
 205
 206                 /* Grab all the remaining data in the binary request. */
 207                 read_buf(fd, (char*)&hdr + PROXY_V2_HEADER_SIZE, size);
 208
 209                 switch (cmd) {
 210                 case CMD_PROXY:
 211                         switch (hdr.v2.fam) {
 212                         case PROXY_FAM_TCPv4:
 213                                 if (size != sizeof hdr.v2.addr.ip4)
 214                                         return 0;
 215                                 inet_ntop(AF_INET, hdr.v2.addr.ip4.src_addr, ipaddr_buf, sizeof ipaddr_buf);
 216                                 return valid_ipaddr(ipaddr_buf);
 217                         case PROXY_FAM_TCPv6:
 218                                 if (size != sizeof hdr.v2.addr.ip6)
 219                                         return 0;
 220                                 inet_ntop(AF_INET6, hdr.v2.addr.ip6.src_addr, ipaddr_buf, sizeof ipaddr_buf);
 221                                 return valid_ipaddr(ipaddr_buf);
 222                         default:
 223                                 break;
 224                         }
 225                         /* For an unsupported protocol we'll ignore the proxy data (leaving ipaddr_buf unset)
 226                          * and accept the connection, which will get handled as a normal socket addr. */
 227                         return 1;
 228                 case CMD_LOCAL:
 229                         return 1;
 230                 default:
 231                         break;
 232                 }
 233
 234                 return 0;
 235         }
 236
 237         if (memcmp(hdr.v1.line, "PROXY", 5) == 0) { /* Proxy V1 */
 238                 char *endc, *sp, *p = hdr.v1.line + PROXY_V2_SIG_SIZE;
 239                 int port_chk;
 240
 241                 *p = '\0';
 242                 if (!strchr(hdr.v1.line, '\n')) {
 243                         while (1) {
 244                                 read_buf(fd, p, 1);
 245                                 if (*p++ == '\n')
 246                                         break;
 247                                 if (p - hdr.v1.line >= (int)sizeof hdr.v1.line - 1)
 248                                         return 0;
 249                         }
 250                         *p = '\0';
 251                 }
 252
 253                 endc = strchr(hdr.v1.line, '\r');
 254                 if (!endc || endc[1] != '\n' || endc[2])
 255                         return 0;
 256                 *endc = '\0';
 257
 258                 p = hdr.v1.line + 5;
 259
 260                 if (!isSpace(p++))
 261                         return 0;
 262                 if (strncmp(p, "TCP4", 4) == 0)
 263                         p += 4;
 264                 else if (strncmp(p, "TCP6", 4) == 0)
 265                         p += 4;
 266                 else if (strncmp(p, "UNKNOWN", 7) == 0)
 267                         return 1;
 268                 else
 269                         return 0;
 270
 271                 if (!isSpace(p++))
 272                         return 0;
 273
 274                 if ((sp = strchr(p, ' ')) == NULL)
 275                         return 0;
 276                 *sp = '\0';
 277                 if (!valid_ipaddr(p))
 278                         return 0;
 279                 strlcpy(ipaddr_buf, p, sizeof ipaddr_buf); /* It will always fit when valid. */
 280
 281                 p = sp + 1;
 282                 if ((sp = strchr(p, ' ')) == NULL)
 283                         return 0;
 284                 *sp = '\0';
 285                 if (!valid_ipaddr(p))
 286                         return 0;
 287                 /* Ignore destination address. */
 288
 289                 p = sp + 1;
 290                 if ((sp = strchr(p, ' ')) == NULL)
 291                         return 0;
 292                 *sp = '\0';
 293                 port_chk = strtol(p, &endc, 10);
 294                 if (*endc || port_chk == 0)
 295                         return 0;
 296                 /* Ignore source port. */
 297
 298                 p = sp + 1;
 299                 port_chk = strtol(p, &endc, 10);
 300                 if (*endc || port_chk == 0)
 301                         return 0;
 302                 /* Ignore destination port. */
 303
 304                 return 1;
 305         }
 306
 307         return 0;
 308 }
 309
 310
 311 /**
 312  * Get the sockaddr for the client.
 313  *
 314  * If it comes in as an ipv4 address mapped into IPv6 format then we
 315  * convert it back to a regular IPv4.
 316  **/
 317 static void client_sockaddr(int fd, struct sockaddr_storage *ss, socklen_t *ss_len)
 318 {
 319         memset(ss, 0, sizeof *ss);
 320
 321         if (getpeername(fd, (struct sockaddr *) ss, ss_len)) {
 322                 /* FIXME: Can we really not continue? */
 323                 rsyserr(FLOG, errno, "getpeername on fd%d failed", fd);
 324                 exit_cleanup(RERR_SOCKETIO);
 325         }
 326
 327 #ifdef INET6
 328         if (GET_SOCKADDR_FAMILY(ss) == AF_INET6
 329          && IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)ss)->sin6_addr)) {
 330                 /* OK, so ss is in the IPv6 family, but it is really
 331                  * an IPv4 address: something like
 332                  * "::ffff:10.130.1.2".  If we use it as-is, then the
 333                  * reverse lookup might fail or perhaps something else
 334                  * bad might happen.  So instead we convert it to an
 335                  * equivalent address in the IPv4 address family.  */
 336                 struct sockaddr_in6 sin6;
 337                 struct sockaddr_in *sin;
 338
 339                 memcpy(&sin6, ss, sizeof sin6);
 340                 sin = (struct sockaddr_in *)ss;
 341                 memset(sin, 0, sizeof *sin);
 342                 sin->sin_family = AF_INET;
 343                 *ss_len = sizeof (struct sockaddr_in);
 344 #ifdef HAVE_SOCKADDR_IN_LEN
 345                 sin->sin_len = *ss_len;
 346 #endif
 347                 sin->sin_port = sin6.sin6_port;
 348
 349                 /* There is a macro to extract the mapped part
 350                  * (IN6_V4MAPPED_TO_SINADDR ?), but it does not seem
 351                  * to be present in the Linux headers. */
 352                 memcpy(&sin->sin_addr, &sin6.sin6_addr.s6_addr[12], sizeof sin->sin_addr);
 353         }
 354 #endif
 355 }
 356
 357
 358 /**
 359  * Compare an addrinfo from the resolver to a sockinfo.
 360  *
 361  * Like strcmp, returns 0 for identical.
 362  **/
 363 static int compare_addrinfo_sockaddr(const struct addrinfo *ai, const struct sockaddr_storage *ss)
 364 {
 365         int ss_family = GET_SOCKADDR_FAMILY(ss);
 366         const char fn[] = "compare_addrinfo_sockaddr";
 367
 368         if (ai->ai_family != ss_family) {
 369                 rprintf(FLOG, "%s: response family %d != %d\n",
 370                         fn, ai->ai_family, ss_family);
 371                 return 1;
 372         }
 373
 374         /* The comparison method depends on the particular AF. */
 375         if (ss_family == AF_INET) {
 376                 const struct sockaddr_in *sin1, *sin2;
 377
 378                 sin1 = (const struct sockaddr_in *) ss;
 379                 sin2 = (const struct sockaddr_in *) ai->ai_addr;
 380
 381                 return memcmp(&sin1->sin_addr, &sin2->sin_addr, sizeof sin1->sin_addr);
 382         }
 383
 384 #ifdef INET6
 385         if (ss_family == AF_INET6) {
 386                 const struct sockaddr_in6 *sin1, *sin2;
 387
 388                 sin1 = (const struct sockaddr_in6 *) ss;
 389                 sin2 = (const struct sockaddr_in6 *) ai->ai_addr;
 390
 391                 if (ai->ai_addrlen < (int)sizeof (struct sockaddr_in6)) {
 392                         rprintf(FLOG, "%s: too short sockaddr_in6; length=%d\n",
 393                                 fn, (int)ai->ai_addrlen);
 394                         return 1;
 395                 }
 396
 397                 if (memcmp(&sin1->sin6_addr, &sin2->sin6_addr, sizeof sin1->sin6_addr))
 398                         return 1;
 399
 400 #ifdef HAVE_SOCKADDR_IN6_SCOPE_ID
 401                 if (sin1->sin6_scope_id != sin2->sin6_scope_id)
 402                         return 1;
 403 #endif
 404                 return 0;
 405         }
 406 #endif /* INET6 */
 407
 408         /* don't know */
 409         return 1;
 410 }
 411
 412
 413 /**
 414  * Do a forward lookup on @p name_buf and make sure it corresponds to
 415  * @p ss -- otherwise we may be being spoofed.  If we suspect we are,
 416  * then we don't abort the connection but just emit a warning, and
 417  * change @p name_buf to be "UNKNOWN".
 418  *
 419  * We don't do anything with the service when checking the name,
 420  * because it doesn't seem that it could be spoofed in any way, and
 421  * getaddrinfo on random service names seems to cause problems on AIX.
 422  **/
 423 static int check_name(const char *ipaddr, const struct sockaddr_storage *ss, char *name_buf, size_t name_buf_size)
 424 {
 425         struct addrinfo hints, *res, *res0;
 426         int error;
 427         int ss_family = GET_SOCKADDR_FAMILY(ss);
 428
 429         memset(&hints, 0, sizeof hints);
 430         hints.ai_family = ss_family;
 431         hints.ai_flags = AI_CANONNAME;
 432         hints.ai_socktype = SOCK_STREAM;
 433         error = getaddrinfo(name_buf, NULL, &hints, &res0);
 434         if (error) {
 435                 rprintf(FLOG, "forward name lookup for %s failed: %s\n",
 436                         name_buf, gai_strerror(error));
 437                 strlcpy(name_buf, default_name, name_buf_size);
 438                 return error;
 439         }
 440
 441         /* Given all these results, we expect that one of them will be
 442          * the same as ss.  The comparison is a bit complicated. */
 443         for (res = res0; res; res = res->ai_next) {
 444                 if (!compare_addrinfo_sockaddr(res, ss))
 445                         break;  /* OK, identical */
 446         }
 447
 448         if (!res0) {
 449                 /* We hit the end of the list without finding an
 450                  * address that was the same as ss. */
 451                 rprintf(FLOG, "no known address for \"%s\": "
 452                         "spoofed address?\n", name_buf);
 453                 strlcpy(name_buf, default_name, name_buf_size);
 454         } else if (res == NULL) {
 455                 /* We hit the end of the list without finding an
 456                  * address that was the same as ss. */
 457                 rprintf(FLOG, "%s is not a known address for \"%s\": "
 458                         "spoofed address?\n", ipaddr, name_buf);
 459                 strlcpy(name_buf, default_name, name_buf_size);
 460         }
 461
 462         freeaddrinfo(res0);
 463         return 0;
 464 }
 465
 466 /* Returns 1 for a valid IPv4 or IPv6 addr, or 0 for a bad one. */
 467 static int valid_ipaddr(const char *s)
 468 {
 469         int i;
 470
 471         if (strchr(s, ':') != NULL) { /* Only IPv6 has a colon. */
 472                 int count, saw_double_colon = 0;
 473                 int ipv4_at_end = 0;
 474
 475                 if (*s == ':') { /* A colon at the start must be a :: */
 476                         if (*++s != ':')
 477                                 return 0;
 478                         saw_double_colon = 1;
 479                         s++;
 480                 }
 481
 482                 for (count = 0; count < 8; count++) {
 483                         if (!*s)
 484                                 return saw_double_colon;
 485
 486                         if (strchr(s, ':') == NULL && strchr(s, '.') != NULL) {
 487                                 if ((!saw_double_colon && count != 6) || (saw_double_colon && count > 6))
 488                                         return 0;
 489                                 ipv4_at_end = 1;
 490                                 break;
 491                         }
 492
 493                         if (!isHexDigit(s++)) /* Need 1-4 hex digits */
 494                                 return 0;
 495                         if (isHexDigit(s) && isHexDigit(++s) && isHexDigit(++s) && isHexDigit(++s))
 496                                 return 0;
 497
 498                         if (*s == ':') {
 499                                 if (!*++s)
 500                                         return 0;
 501                                 if (*s == ':') {
 502                                         if (saw_double_colon)
 503                                                 return 0;
 504                                         saw_double_colon = 1;
 505                                         s++;
 506                                 }
 507                         }
 508                 }
 509
 510                 if (!ipv4_at_end)
 511                         return !*s;
 512         }
 513
 514         /* IPv4 */
 515         for (i = 0; i < 4; i++) {
 516                 long n;
 517                 char *end;
 518
 519                 if (i && *s++ != '.')
 520                         return 0;
 521                 n = strtol(s, &end, 10);
 522                 if (n > 255 || n < 0 || end <= s || end > s+3)
 523                         return 0;
 524                 s = end;
 525         }
 526
 527         return !*s;
 528 }