lib/libskey/skeyaccess.c

   1  /*
   2   * Figure out if UNIX passwords are permitted for any combination of user
   3   * name, group member, terminal port, host_name or network:
   4   *
   5   * Programmatic interface: skeyaccess(user, port, host, addr)
   6   *
   7   * All arguments are null-terminated strings. Specify a null character pointer
   8   * where information is not available.
   9   *
  10   * When no address information is given this code performs the host (internet)
  11   * address lookup itself. It rejects addresses that appear to belong to
  12   * someone else.
  13   *
  14   * When compiled with -DPERMIT_CONSOLE always permits UNIX passwords with
  15   * console logins, no matter what the configuration file says.
  16   *
  17   * To build a stand-alone test version, compile with -DTEST and run it off an
  18   * skey.access file in the current directory:
  19   *
  20   * Command-line interface: ./skeyaccess user port [host_or_ip_addr]
  21   *
  22   * Errors are reported via syslogd.
  23   *
  24   * Author: Wietse Venema, Eindhoven University of Technology.
  25   *
  26   * $FreeBSD: src/lib/libskey/skeyaccess.c,v 1.9.6.2 2002/08/12 19:42:24 iedowse Exp $
  27   * $DragonFly: src/lib/libskey/skeyaccess.c,v 1.5 2008/09/30 16:57:05 swildner Exp $
  28   */
  29
  30 #include <sys/types.h>
  31 #include <sys/socket.h>
  32 #include <netinet/in.h>
  33 #include <string.h>
  34 #include <netdb.h>
  35 #include <arpa/inet.h>
  36 #include <stdio.h>
  37 #include <grp.h>
  38 #include <pwd.h>
  39 #include <ctype.h>
  40 #include <syslog.h>
  41 #include <unistd.h>
  42 #include <stdlib.h>
  43 #include <sys/param.h>
  44
  45 #include "pathnames.h"
  46
  47  /*
  48   * Token input with one-deep pushback.
  49   */
  50 static char *prev_token = 0;            /* push-back buffer */
  51 static char *line_pointer = NULL;
  52 static char *first_token (char *, int, FILE *);
  53 static int line_number;
  54 static void unget_token (char *);
  55 static char *get_token (void);
  56 static char *need_token (void);
  57 static char *need_internet_addr (void);
  58
  59  /*
  60   * Various forms of token matching.
  61   */
  62 #define match_host_name(l)      match_token((l)->host_name)
  63 #define match_port(l)           match_token((l)->port)
  64 #define match_user(l)           match_token((l)->user)
  65 struct login_info;
  66 static int match_internet_addr (struct login_info *);
  67 static int match_group (struct login_info *);
  68 static int match_token (char *);
  69 static int is_internet_addr (char *);
  70 static struct addrinfo *convert_internet_addr (char *);
  71 static struct addrinfo *lookup_internet_addr (char *);
  72
  73 #define MAX_ADDR        32
  74 #define PERMIT          1
  75 #define DENY            0
  76
  77 #ifndef CONSOLE
  78 #define CONSOLE         "console"
  79 #endif
  80 #ifndef VTY_PREFIX
  81 #define VTY_PREFIX      "ttyv"
  82 #endif
  83
  84 struct login_info {
  85     char   *host_name;                  /* host name */
  86     struct addrinfo *internet_addr;     /* addrinfo chain */
  87     char   *user;                       /* user name */
  88     char   *port;                       /* login port */
  89 };
  90
  91 static int _skeyaccess (FILE *, struct login_info *);
  92 int skeyaccess (char *, char *, char *, char *);
  93
  94 /* skeyaccess - find out if UNIX passwords are permitted */
  95
  96 int
  97 skeyaccess(char *user, char *port, char *host, char *addr)
  98 {
  99     FILE   *fp;
 100     struct login_info login_info;
 101     int     result;
 102
 103     /*
 104      * Assume no restriction on the use of UNIX passwords when the s/key
 105      * acces table does not exist.
 106      */
 107     if ((fp = fopen(_PATH_SKEYACCESS, "r")) == 0) {
 108 #ifdef TEST
 109         fprintf(stderr, "No file %s, thus no access control\n", _PATH_SKEYACCESS);
 110 #endif
 111         return (PERMIT);
 112     }
 113
 114     /*
 115      * Bundle up the arguments in a structure so we won't have to drag around
 116      * boring long argument lists.
 117      *
 118      * Look up the host address when only the name is given. We try to reject
 119      * addresses that belong to someone else.
 120      */
 121     login_info.user = user;
 122     login_info.port = port;
 123
 124     if (host != NULL && !is_internet_addr(host)) {
 125         login_info.host_name = host;
 126     } else {
 127         login_info.host_name = NULL;
 128     }
 129
 130     if (addr != NULL && is_internet_addr(addr)) {
 131         login_info.internet_addr = convert_internet_addr(addr);
 132     } else if (host != NULL) {
 133         if (is_internet_addr(host)) {
 134             login_info.internet_addr = convert_internet_addr(host);
 135         } else {
 136             login_info.internet_addr = lookup_internet_addr(host);
 137         }
 138     } else {
 139         login_info.internet_addr = NULL;
 140     }
 141
 142     /*
 143      * Print what we think the user wants us to do.
 144      */
 145 #ifdef TEST
 146     printf("port: %s\n", login_info.port);
 147     printf("user: %s\n", login_info.user);
 148     printf("host: %s\n", login_info.host_name ? login_info.host_name : "none");
 149     printf("addr: ");
 150     if (login_info.internet_addr == NULL) {
 151         printf("none\n");
 152     } else {
 153         struct addrinfo *res;
 154         char haddr[NI_MAXHOST];
 155
 156         for (res = login_info.internet_addr; res; res = res->ai_next) {
 157             getnameinfo(res->ai_addr, res->ai_addrlen, haddr, sizeof(haddr),
 158                         NULL, 0, NI_NUMERICHOST | NI_WITHSCOPEID);
 159             printf("%s%s", haddr, res->ai_next ? " " : "\n");
 160         }
 161     }
 162 #endif
 163     result = _skeyaccess(fp, &login_info);
 164     fclose(fp);
 165     if (login_info.internet_addr)
 166         freeaddrinfo(login_info.internet_addr);
 167     return (result);
 168 }
 169
 170 /* _skeyaccess - find out if UNIX passwords are permitted */
 171
 172 static int
 173 _skeyaccess(FILE *fp, struct login_info *login_info)
 174 {
 175     char    buf[BUFSIZ];
 176     char   *tok;
 177     int     match;
 178     int     permission=DENY;
 179
 180 #ifdef PERMIT_CONSOLE
 181     if (login_info->port != 0 &&
 182         (strcmp(login_info->port, CONSOLE) == 0 ||
 183          strncmp(login_info->port, VTY_PREFIX, sizeof(VTY_PREFIX) - 1) == 0
 184         )
 185        )
 186         return (1);
 187 #endif
 188
 189     /*
 190      * Scan the s/key access table until we find an entry that matches. If no
 191      * match is found, assume that UNIX passwords are disallowed.
 192      */
 193     match = 0;
 194     while (match == 0 && (tok = first_token(buf, sizeof(buf), fp))) {
 195         if (strncasecmp(tok, "permit", 4) == 0) {
 196             permission = PERMIT;
 197         } else if (strncasecmp(tok, "deny", 4) == 0) {
 198             permission = DENY;
 199         } else {
 200             syslog(LOG_ERR, "%s: line %d: bad permission: %s",
 201                    _PATH_SKEYACCESS, line_number, tok);
 202             continue;                           /* error */
 203         }
 204
 205         /*
 206          * Process all conditions in this entry until we find one that fails.
 207          */
 208         match = 1;
 209         while (match != 0 && (tok = get_token())) {
 210             if (strcasecmp(tok, "hostname") == 0) {
 211                 match = match_host_name(login_info);
 212             } else if (strcasecmp(tok, "port") == 0) {
 213                 match = match_port(login_info);
 214             } else if (strcasecmp(tok, "user") == 0) {
 215                 match = match_user(login_info);
 216             } else if (strcasecmp(tok, "group") == 0) {
 217                 match = match_group(login_info);
 218             } else if (strcasecmp(tok, "internet") == 0) {
 219                 match = match_internet_addr(login_info);
 220             } else if (is_internet_addr(tok)) {
 221                 unget_token(tok);
 222                 match = match_internet_addr(login_info);
 223             } else {
 224                 syslog(LOG_ERR, "%s: line %d: bad condition: %s",
 225                        _PATH_SKEYACCESS, line_number, tok);
 226                 match = 0;
 227             }
 228         }
 229     }
 230     return (match ? permission : DENY);
 231 }
 232
 233 /* translate IPv4 mapped IPv6 address to IPv4 address */
 234
 235 static void
 236 ai_unmapped(struct addrinfo *ai)
 237 {
 238     struct sockaddr_in6 *sin6;
 239     struct sockaddr_in *sin4;
 240     u_int32_t addr;
 241     int port;
 242
 243     if (ai->ai_family != AF_INET6)
 244         return;
 245     sin6 = (struct sockaddr_in6 *)ai->ai_addr;
 246     if (!IN6_IS_ADDR_V4MAPPED(&sin6->sin6_addr))
 247         return;
 248     sin4 = (struct sockaddr_in *)ai->ai_addr;
 249     addr = *(u_int32_t *)&sin6->sin6_addr.s6_addr[12];
 250     port = sin6->sin6_port;
 251     memset(sin4, 0, sizeof(struct sockaddr_in));
 252     sin4->sin_addr.s_addr = addr;
 253     sin4->sin_port = port;
 254     sin4->sin_family = AF_INET;
 255     sin4->sin_len = sizeof(struct sockaddr_in);
 256     ai->ai_family = AF_INET;
 257     ai->ai_addrlen = sizeof(struct sockaddr_in);
 258 }
 259
 260 /* match_internet_addr - match internet network address */
 261
 262 static int
 263 match_internet_addr(struct login_info *login_info)
 264 {
 265     char *tok;
 266     struct addrinfo *res;
 267     struct sockaddr_storage pattern, mask;
 268     struct sockaddr_in *addr4, *pattern4, *mask4;
 269     struct sockaddr_in6 *addr6, *pattern6, *mask6;
 270     int i, match;
 271
 272     if (login_info->internet_addr == NULL)
 273         return (0);
 274     if ((tok = need_internet_addr()) == 0)
 275         return (0);
 276     if ((res = convert_internet_addr(tok)) == NULL)
 277         return (0);
 278     memcpy(&pattern, res->ai_addr, res->ai_addrlen);
 279     freeaddrinfo(res);
 280     if ((tok = need_internet_addr()) == 0)
 281         return (0);
 282     if ((res = convert_internet_addr(tok)) == NULL)
 283         return (0);
 284     memcpy(&mask, res->ai_addr, res->ai_addrlen);
 285     freeaddrinfo(res);
 286     if (pattern.ss_family != mask.ss_family)
 287         return (0);
 288     mask4 = (struct sockaddr_in *)&mask;
 289     pattern4 = (struct sockaddr_in *)&pattern;
 290     mask6 = (struct sockaddr_in6 *)&mask;
 291     pattern6 = (struct sockaddr_in6 *)&pattern;
 292
 293     /*
 294      * See if any of the addresses matches a pattern in the control file. We
 295      * have already tried to drop addresses that belong to someone else.
 296      */
 297
 298     for (res = login_info->internet_addr; res; res = res->ai_next) {
 299         ai_unmapped(res);
 300         if (res->ai_family != pattern.ss_family)
 301             continue;
 302         switch (res->ai_family) {
 303         case AF_INET:
 304             addr4 = (struct sockaddr_in *)res->ai_addr;
 305             if (addr4->sin_addr.s_addr != INADDR_NONE &&
 306                 (addr4->sin_addr.s_addr & mask4->sin_addr.s_addr) == pattern4->sin_addr.s_addr)
 307                 return (1);
 308             break;
 309         case AF_INET6:
 310             addr6 = (struct sockaddr_in6 *)res->ai_addr;
 311             if (pattern6->sin6_scope_id != 0 &&
 312                 addr6->sin6_scope_id != pattern6->sin6_scope_id)
 313                 break;
 314             match = 1;
 315             for (i = 0; i < 16; ++i) {
 316                 if ((addr6->sin6_addr.s6_addr[i] & mask6->sin6_addr.s6_addr[i]) != pattern6->sin6_addr.s6_addr[i]) {
 317                     match = 0;
 318                     break;
 319                 }
 320             }
 321             if (match)
 322                 return (1);
 323             break;
 324         }
 325     }
 326     return (0);
 327 }
 328
 329 /* match_group - match username against group */
 330
 331 static int
 332 match_group(struct login_info *login_info)
 333 {
 334     struct passwd *passwd;
 335     struct group *group;
 336     char   *tok;
 337     char  **memp;
 338
 339     if ((tok = need_token()) &&
 340         (passwd = getpwnam(login_info->user)) && (group = getgrnam(tok))) {
 341         if (passwd->pw_gid == (gid_t)group->gr_gid)
 342             return (1);
 343         for (memp = group->gr_mem; *memp; memp++)
 344             if (strcmp(login_info->user, *memp) == 0)
 345                 return (1);
 346     }
 347     return (0);                                 /* XXX endgrent() */
 348 }
 349
 350 /* match_token - get and match token */
 351
 352 static int
 353 match_token(char *str)
 354 {
 355     char   *tok;
 356
 357     return (str && (tok = need_token()) && strcasecmp(str, tok) == 0);
 358 }
 359
 360 /* first_token - read line and return first token */
 361
 362 static char *
 363 first_token(char *buf, int len, FILE *fp)
 364 {
 365     char   *cp;
 366
 367     prev_token = 0;
 368     for (;;) {
 369         if (fgets(buf, len, fp) == 0)
 370             return (0);
 371         line_number++;
 372         buf[strcspn(buf, "\r\n#")] = 0;
 373 #ifdef TEST
 374         if (buf[0])
 375             printf("rule: %s\n", buf);
 376 #endif
 377         line_pointer = buf;
 378         while ((cp = strsep(&line_pointer, " \t")) != NULL && *cp == '\0')
 379                 ;
 380         if (cp != NULL)
 381             return (cp);
 382     }
 383 }
 384
 385 /* unget_token - push back last token */
 386
 387 static void
 388 unget_token(char *cp)
 389 {
 390     prev_token = cp;
 391 }
 392
 393 /* get_token - retrieve next token from buffer */
 394
 395 static char *
 396 get_token(void)
 397 {
 398     char   *cp;
 399
 400     if ( (cp = prev_token) ) {
 401         prev_token = 0;
 402     } else {
 403         while ((cp = strsep(&line_pointer, " \t")) != NULL && *cp == '\0')
 404                 ;
 405     }
 406     return (cp);
 407 }
 408
 409 /* need_token - complain if next token is not available */
 410
 411 static char *
 412 need_token(void)
 413 {
 414     char   *cp;
 415
 416     if ((cp = get_token()) == 0)
 417         syslog(LOG_ERR, "%s: line %d: premature end of rule",
 418                _PATH_SKEYACCESS, line_number);
 419     return (cp);
 420 }
 421
 422 /* need_internet_addr - complain if next token is not an internet address */
 423
 424 static char *
 425 need_internet_addr(void)
 426 {
 427     char   *cp;
 428
 429     if ((cp = get_token()) == 0) {
 430         syslog(LOG_ERR, "%s: line %d: internet address expected",
 431                _PATH_SKEYACCESS, line_number);
 432         return (0);
 433     } else if (!is_internet_addr(cp)) {
 434         syslog(LOG_ERR, "%s: line %d: bad internet address: %s",
 435                _PATH_SKEYACCESS, line_number, cp);
 436         return (0);
 437     } else {
 438         return (cp);
 439     }
 440 }
 441
 442 /* is_internet_addr - determine if string is a dotted quad decimal address */
 443
 444 static int
 445 is_internet_addr(char *str)
 446 {
 447     struct addrinfo *res;
 448
 449     if ((res = convert_internet_addr(str)) != NULL)
 450         freeaddrinfo(res);
 451     return (res != NULL);
 452 }
 453
 454 /*
 455  * Nuke addrinfo entry from list.
 456  * XXX: Depending on the implementation of KAME's getaddrinfo(3).
 457  */
 458 static void
 459 nuke_ai(struct addrinfo **aip)
 460 {
 461     struct addrinfo *ai;
 462
 463     ai = *aip;
 464     *aip = ai->ai_next;
 465     if (ai->ai_canonname) {
 466         if (ai->ai_next && !ai->ai_next->ai_canonname)
 467             ai->ai_next->ai_canonname = ai->ai_canonname;
 468         else
 469             free(ai->ai_canonname);
 470     }
 471     free(ai);
 472 }
 473
 474 /* lookup_internet_addr - look up internet addresses with extreme prejudice */
 475
 476 static struct addrinfo *
 477 lookup_internet_addr(char *host)
 478 {
 479     struct addrinfo hints, *res0, *res, **resp;
 480     char hname[NI_MAXHOST], haddr[NI_MAXHOST];
 481     int error;
 482
 483     memset(&hints, 0, sizeof(hints));
 484     hints.ai_family = PF_UNSPEC;
 485     hints.ai_socktype = SOCK_STREAM;
 486     hints.ai_flags = AI_PASSIVE | AI_CANONNAME;
 487     if (getaddrinfo(host, NULL, &hints, &res0) != 0)
 488         return (NULL);
 489     if (res0->ai_canonname == NULL) {
 490         freeaddrinfo(res0);
 491         return (NULL);
 492     }
 493
 494     /*
 495      * Wipe addresses that appear to belong to someone else. We will get
 496      * false alarms when when the hostname comes from DNS, while its
 497      * addresses are listed under different names in local databases.
 498      */
 499 #define NEQ(x,y)        (strcasecmp((x),(y)) != 0)
 500 #define NEQ3(x,y,n)     (strncasecmp((x),(y), (n)) != 0)
 501
 502     resp = &res0;
 503     while ((res = *resp) != NULL) {
 504         if (res->ai_family != AF_INET && res->ai_family != AF_INET6) {
 505             nuke_ai(resp);
 506             continue;
 507         }
 508         error = getnameinfo(res->ai_addr, res->ai_addrlen,
 509                             hname, sizeof(hname),
 510                             NULL, 0, NI_NAMEREQD | NI_WITHSCOPEID);
 511         if (error) {
 512             getnameinfo(res->ai_addr, res->ai_addrlen, haddr, sizeof(haddr),
 513                         NULL, 0, NI_NUMERICHOST | NI_WITHSCOPEID);
 514             syslog(LOG_ERR, "address %s not registered for host %s",
 515                    haddr, res0->ai_canonname);
 516             nuke_ai(resp);
 517             continue;
 518         }
 519         if (NEQ(res0->ai_canonname, hname) &&
 520             NEQ3(res0->ai_canonname, "localhost.", 10)) {
 521             getnameinfo(res->ai_addr, res->ai_addrlen, haddr, sizeof(haddr),
 522                         NULL, 0, NI_NUMERICHOST | NI_WITHSCOPEID);
 523             syslog(LOG_ERR, "address %s registered for host %s and %s",
 524                    haddr, hname, res0->ai_canonname);
 525             nuke_ai(resp);
 526             continue;
 527         }
 528         resp = &res->ai_next;
 529     }
 530     return (res0);
 531 }
 532
 533 /* convert_internet_addr - convert string to internet address */
 534
 535 static struct addrinfo *
 536 convert_internet_addr(char *string)
 537 {
 538     struct addrinfo hints, *res;
 539
 540     memset(&hints, 0, sizeof(hints));
 541     hints.ai_family = PF_UNSPEC;
 542     hints.ai_socktype = SOCK_STREAM;
 543     hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST;
 544     if (getaddrinfo(string, NULL, &hints, &res) != 0)
 545         return (NULL);
 546     return (res);
 547 }
 548
 549 #ifdef TEST
 550
 551 int
 552 main(int argc, char **argv)
 553 {
 554     struct addrinfo hints, *res;
 555     char    host[MAXHOSTNAMELEN + 1];
 556     int     verdict;
 557     char   *user;
 558     char   *port;
 559
 560     if (argc != 3 && argc != 4) {
 561         fprintf(stderr, "usage: %s user port [host_or_ip_address]\n", argv[0]);
 562         exit(0);
 563     }
 564     if (_PATH_SKEYACCESS[0] != '/')
 565         printf("Warning: this program uses control file: %s\n", _PATH_SKEYACCESS);
 566     openlog("login", LOG_PID, LOG_AUTH);
 567
 568     user = argv[1];
 569     port = argv[2];
 570     if (argv[3]) {
 571         memset(&hints, 0, sizeof(hints));
 572         hints.ai_family = PF_UNSPEC;
 573         hints.ai_socktype = SOCK_STREAM;
 574         hints.ai_flags = AI_PASSIVE | AI_CANONNAME;
 575         if (getaddrinfo(argv[3], NULL, &hints, &res) == 0) {
 576             if (res->ai_canonname == NULL)
 577                 strncpy(host, argv[3], MAXHOSTNAMELEN);
 578             else
 579                 strncpy(host, res->ai_canonname, MAXHOSTNAMELEN);
 580             freeaddrinfo(res);
 581         } else
 582             strncpy(host, argv[3], MAXHOSTNAMELEN);
 583         host[MAXHOSTNAMELEN] = 0;
 584     }
 585     verdict = skeyaccess(user, port, argv[3] ? host : (char *) 0, (char *) 0);
 586     printf("UNIX passwords %spermitted\n", verdict ? "" : "NOT ");
 587     return (0);
 588 }
 589
 590 #endif