lib/libtelnet/sra.c

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      Dave Safford.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  */
  30
  31 #include <sys/cdefs.h>
  32 #ifdef notdef
  33 __FBSDID("$FreeBSD: src/contrib/telnet/libtelnet/sra.c,v 1.16 2002/05/06 09:48:02 markm Exp $");
  34 #else
  35 __RCSID("$NetBSD: sra.c,v 1.11 2012/01/09 15:25:34 christos Exp $");
  36 #endif
  37
  38 #ifdef  SRA
  39 #ifdef  ENCRYPTION
  40 #include <sys/types.h>
  41 #include <arpa/telnet.h>
  42 #include <paths.h>
  43 #include <pwd.h>
  44 #include <stdio.h>
  45 #include <stdlib.h>
  46 #include <string.h>
  47 #include <syslog.h>
  48 #include <ttyent.h>
  49
  50 #ifndef NOPAM
  51 #include <security/pam_appl.h>
  52 #else
  53 #include <unistd.h>
  54 #endif
  55
  56 #include "auth.h"
  57 #include "misc.h"
  58 #include "encrypt.h"
  59 #include "pk.h"
  60
  61 char pka[HEXKEYBYTES+1], ska[HEXKEYBYTES+1], pkb[HEXKEYBYTES+1];
  62 char *user, *pass, *xuser, *xpass;
  63 char *passprompt, *xpassprompt;
  64 DesData ck;
  65 IdeaData ik;
  66
  67 extern int auth_debug_mode;
  68 extern char *line;              /* see sys_term.c */
  69
  70 static int sra_valid = 0;
  71 static int passwd_sent = 0;
  72
  73 static unsigned char str_data[1024] = { IAC, SB, TELOPT_AUTHENTICATION, 0,
  74                                         AUTHTYPE_SRA, };
  75
  76 #define SMALL_LEN       256
  77 #define XSMALL_LEN      513
  78 #define SRA_KEY 0
  79 #define SRA_USER 1
  80 #define SRA_CONTINUE 2
  81 #define SRA_PASS 3
  82 #define SRA_ACCEPT 4
  83 #define SRA_REJECT 5
  84
  85 static int check_user(char *, const char *);
  86
  87 /* support routine to send out authentication message */
  88 static int
  89 Data(Authenticator *ap, int type, void *d, int c)
  90 {
  91         unsigned char *p = str_data + 4;
  92         unsigned char *cd = d;
  93
  94         if (c == -1)
  95                 c = strlen(d);
  96
  97         if (auth_debug_mode) {
  98                 printf("%s:%d: [%d] (%d)",
  99                     str_data[3] == TELQUAL_IS ? ">>>IS" : ">>>REPLY",
 100                     str_data[3], type, c);
 101                 printd(d, c);
 102                 printf("\r\n");
 103         }
 104         *p++ = ap->type;
 105         *p++ = ap->way;
 106         *p++ = type;
 107         while (c-- > 0) {
 108                 if ((*p++ = *cd++) == IAC)
 109                         *p++ = IAC;
 110         }
 111         *p++ = IAC;
 112         *p++ = SE;
 113         if (str_data[3] == TELQUAL_IS)
 114                 printsub('>', &str_data[2], p - (&str_data[2]));
 115         return telnet_net_write(str_data, p - str_data);
 116 }
 117
 118 int
 119 sra_init(Authenticator *ap __unused, int server)
 120 {
 121         if (server)
 122                 str_data[3] = TELQUAL_REPLY;
 123         else
 124                 str_data[3] = TELQUAL_IS;
 125
 126         user = malloc(SMALL_LEN);
 127         xuser = malloc(XSMALL_LEN);
 128         pass = malloc(SMALL_LEN);
 129         xpass = malloc(XSMALL_LEN);
 130         passprompt = malloc(SMALL_LEN);
 131         xpassprompt = malloc(XSMALL_LEN);
 132
 133         if (user == NULL || xuser == NULL || pass == NULL || xpass ==
 134             NULL || passprompt == NULL || xpassprompt == NULL)
 135                 return 0; /* malloc failed */
 136
 137         passwd_sent = 0;
 138
 139         genkeys(pka, ska);
 140         return 1;
 141 }
 142
 143 /* client received a go-ahead for sra */
 144 int
 145 sra_send(Authenticator *ap)
 146 {
 147         /* send PKA */
 148
 149         if (auth_debug_mode)
 150                 printf("Sent PKA to server.\r\n" );
 151         printf("Trying SRA secure login:\r\n");
 152         if (!Data(ap, SRA_KEY, (void *)pka, HEXKEYBYTES)) {
 153                 if (auth_debug_mode)
 154                         printf("Not enough room for authentication data\r\n");
 155                 return 0;
 156         }
 157
 158         return 1;
 159 }
 160
 161 /* server received an IS -- could be SRA KEY, USER, or PASS */
 162 void
 163 sra_is(Authenticator *ap, unsigned char *data, int cnt)
 164 {
 165         int valid;
 166         Session_Key skey;
 167
 168         if (cnt-- < 1)
 169                 goto bad;
 170         switch (*data++) {
 171
 172         case SRA_KEY:
 173                 if (cnt < HEXKEYBYTES) {
 174                         Data(ap, SRA_REJECT, (void *)0, 0);
 175                         auth_finished(ap, AUTH_USER);
 176                         if (auth_debug_mode) {
 177                                 printf("SRA user rejected for bad PKB\r\n");
 178                         }
 179                         return;
 180                 }
 181                 if (auth_debug_mode)
 182                         printf("Sent pka\r\n");
 183                 if (!Data(ap, SRA_KEY, (void *)pka, HEXKEYBYTES)) {
 184                         if (auth_debug_mode)
 185                                 printf("Not enough room\r\n");
 186                         return;
 187                 }
 188                 memcpy(pkb, data, HEXKEYBYTES);
 189                 pkb[HEXKEYBYTES] = '\0';
 190                 common_key(ska, pkb, &ik, &ck);
 191                 return;
 192
 193         case SRA_USER:
 194                 /* decode KAB(u) */
 195                 if (cnt > XSMALL_LEN - 1) /* Attempted buffer overflow */
 196                         break;
 197                 memcpy(xuser, data, cnt);
 198                 xuser[cnt] = '\0';
 199                 pk_decode(xuser, user, &ck);
 200                 auth_encrypt_user(user);
 201 #ifndef NOPAM
 202                 (void)check_user(user, "*");
 203 #endif
 204                 pk_encode(passprompt, xpassprompt, &ck);
 205                 Data(ap, SRA_CONTINUE, xpassprompt, XSMALL_LEN - 1);
 206
 207                 return;
 208
 209         case SRA_PASS:
 210                 if (cnt > XSMALL_LEN - 1) /* Attempted buffer overflow */
 211                         break;
 212                 /* decode KAB(P) */
 213                 memcpy(xpass, data, cnt);
 214                 xpass[cnt] = '\0';
 215                 pk_decode(xpass, pass, &ck);
 216
 217                 /* check user's password */
 218                 valid = check_user(user, pass);
 219
 220                 if(valid) {
 221                         /* PAM (via check_user()) may have changed 'user' */
 222                         auth_encrypt_user(user);
 223                         Data(ap, SRA_ACCEPT, (void *)0, 0);
 224                         skey.data = ck;
 225                         skey.type = SK_DES;
 226                         skey.length = 8;
 227                         encrypt_session_key(&skey, 1);
 228
 229                         sra_valid = 1;
 230                         auth_finished(ap, AUTH_VALID);
 231                         if (auth_debug_mode) {
 232                                 printf("SRA user accepted\r\n");
 233                         }
 234                 }
 235                 else {
 236                         pk_encode(passprompt, xpassprompt, &ck);
 237                         Data(ap, SRA_CONTINUE, (void *)xpassprompt,
 238                             XSMALL_LEN - 1);
 239                         if (auth_debug_mode) {
 240                                 printf("SRA user failed\r\n");
 241                         }
 242                 }
 243                 return;
 244
 245         default:
 246                 if (auth_debug_mode)
 247                         printf("Unknown SRA option %d\r\n", data[-1]);
 248         }
 249 bad:
 250         Data(ap, SRA_REJECT, 0, 0);
 251         sra_valid = 0;
 252         auth_finished(ap, AUTH_REJECT);
 253 }
 254
 255 /* client received REPLY -- could be SRA KEY, CONTINUE, ACCEPT, or REJECT */
 256 void
 257 sra_reply(Authenticator *ap, unsigned char *data, int cnt)
 258 {
 259         char uprompt[SMALL_LEN], tuser[SMALL_LEN];
 260         Session_Key skey;
 261         size_t i;
 262
 263         if (cnt-- < 1)
 264                 return;
 265         switch (*data++) {
 266
 267         case SRA_KEY:
 268                 /* calculate common key */
 269                 if (cnt < HEXKEYBYTES) {
 270                         if (auth_debug_mode) {
 271                                 printf("SRA user rejected for bad PKB\r\n");
 272                         }
 273                         return;
 274                 }
 275                 memcpy(pkb, data, HEXKEYBYTES);
 276                 pkb[HEXKEYBYTES] = '\0';
 277
 278                 common_key(ska, pkb, &ik, &ck);
 279
 280         enc_user:
 281
 282                 /* encode user */
 283                 memset(tuser, 0, sizeof(tuser));
 284                 snprintf(uprompt, sizeof(uprompt), "User (%s): ",
 285                     UserNameRequested);
 286                 if (telnet_gets(uprompt, tuser, SMALL_LEN - 1, 1) == NULL) {
 287                         printf("\n");
 288                         exit(1);
 289                 }
 290                 if (tuser[0] == '\n' || tuser[0] == '\r' )
 291                         strlcpy(user, UserNameRequested, SMALL_LEN);
 292                 else {
 293                         /* telnet_gets leaves the newline on */
 294                         for(i = 0; i < sizeof(tuser); i++) {
 295                                 if (tuser[i] == '\n') {
 296                                         tuser[i] = '\0';
 297                                         break;
 298                                 }
 299                         }
 300                         strlcpy(user, tuser, SMALL_LEN);
 301                 }
 302                 pk_encode(user, xuser, &ck);
 303
 304                 /* send it off */
 305                 if (auth_debug_mode)
 306                         printf("Sent KAB(U)\r\n");
 307                 if (!Data(ap, SRA_USER, (void *)xuser, strlen(xuser))) {
 308                         if (auth_debug_mode)
 309                                 printf("Not enough room\r\n");
 310                         return;
 311                 }
 312                 break;
 313
 314         case SRA_CONTINUE:
 315                 if (passwd_sent) {
 316                         passwd_sent = 0;
 317                         printf("[ SRA login failed ]\r\n");
 318                         goto enc_user;
 319                 }
 320                 if (cnt > XSMALL_LEN - 1) {
 321                         break;
 322                 } else if (cnt > 0) {
 323                         (void)memcpy(xpassprompt, data, cnt);
 324                         pk_decode(xpassprompt, passprompt, &ck);
 325                 } else {
 326                         (void)strlcpy(passprompt, "Password: ", SMALL_LEN);
 327                 }
 328                 /* encode password */
 329                 memset(pass, 0, SMALL_LEN);
 330                 if (telnet_gets(passprompt, pass, SMALL_LEN - 1, 0) == NULL) {
 331                         printf("\n");
 332                         exit(1);
 333                 }
 334                 pk_encode(pass, xpass, &ck);
 335                 /* send it off */
 336                 if (auth_debug_mode)
 337                         printf("Sent KAB(P)\r\n");
 338                 if (!Data(ap, SRA_PASS, (void *)xpass, strlen(xpass))) {
 339                         if (auth_debug_mode)
 340                                 printf("Not enough room\r\n");
 341                         return;
 342                 }
 343                 passwd_sent = 1;
 344                 break;
 345
 346         case SRA_REJECT:
 347                 printf("[ SRA refuses authentication ]\r\n");
 348                 printf("Trying plaintext login:\r\n");
 349                 auth_finished(0, AUTH_REJECT);
 350                 return;
 351
 352         case SRA_ACCEPT:
 353                 printf("[ SRA accepts you ]\r\n");
 354                 skey.data = ck;
 355                 skey.type = SK_DES;
 356                 skey.length = 8;
 357                 encrypt_session_key(&skey, 0);
 358
 359                 auth_finished(ap, AUTH_VALID);
 360                 return;
 361         default:
 362                 if (auth_debug_mode)
 363                         printf("Unknown SRA option %d\r\n", data[-1]);
 364                 return;
 365         }
 366 }
 367
 368 int
 369 sra_status(Authenticator *ap __unused, char *name, size_t len, int level)
 370 {
 371         if (level < AUTH_USER)
 372                 return level;
 373         if (UserNameRequested && sra_valid) {
 374                 strlcpy(name, UserNameRequested, len);
 375                 return AUTH_VALID;
 376         } else
 377                 return AUTH_USER;
 378 }
 379
 380 #define BUMP(buf, len)          while (*(buf)) { ++(buf), --(len); }
 381 #define ADDC(buf, len, c)       if ((len) > 0) { *(buf)++ = (c); --(len); }
 382
 383 void
 384 sra_printsub(unsigned char *data, int cnt, unsigned char *ubuf, int buflen)
 385 {
 386         char lbuf[32], *buf = (char *)ubuf;
 387         int i;
 388
 389         buf[buflen - 1] = '\0';                 /* make sure its NULL terminated */
 390         buflen -= 1;
 391
 392         switch(data[3]) {
 393
 394         case SRA_CONTINUE:
 395                 strncpy(buf, " CONTINUE ", buflen);
 396                 goto common;
 397
 398         case SRA_REJECT:                /* Rejected (reason might follow) */
 399                 strncpy(buf, " REJECT ", buflen);
 400                 goto common;
 401
 402         case SRA_ACCEPT:                /* Accepted (name might follow) */
 403                 strncpy(buf, " ACCEPT ", buflen);
 404
 405         common:
 406                 BUMP(buf, buflen);
 407                 if (cnt <= 4)
 408                         break;
 409                 ADDC(buf, buflen, '"');
 410                 for (i = 4; i < cnt; i++)
 411                         ADDC(buf, buflen, data[i]);
 412                 ADDC(buf, buflen, '"');
 413                 ADDC(buf, buflen, '\0');
 414                 break;
 415
 416         case SRA_KEY:                   /* Authentication data follows */
 417                 strncpy(buf, " KEY ", buflen);
 418                 goto common2;
 419
 420         case SRA_USER:
 421                 strncpy(buf, " USER ", buflen);
 422                 goto common2;
 423
 424         case SRA_PASS:
 425                 strncpy(buf, " PASS ", buflen);
 426                 goto common2;
 427
 428         default:
 429                 snprintf(lbuf, sizeof(lbuf), " %d (unknown)", data[3]);
 430                 strncpy(buf, lbuf, buflen);
 431         common2:
 432                 BUMP(buf, buflen);
 433                 for (i = 4; i < cnt; i++) {
 434                         snprintf(lbuf, sizeof(lbuf), " %d", data[i]);
 435                         strncpy(buf, lbuf, buflen);
 436                         BUMP(buf, buflen);
 437                 }
 438                 break;
 439         }
 440 }
 441
 442 #ifdef NOPAM
 443 static int
 444 isroot(const char *usr)
 445 {
 446         struct passwd pws, *pwd;
 447         char pwbuf[1024];
 448
 449         if (getpwnam_r(usr, &pws, pwbuf, sizeof(pwbuf), &pwd) != 0 ||
 450             pwd == NULL)
 451                 return 0;
 452         return (!pwd->pw_uid);
 453 }
 454
 455 static int
 456 rootterm(const char *ttyname)
 457 {
 458         struct ttyent *t;
 459         const char *ttyn;
 460
 461         ttyn = ttyname;
 462         if (strncmp(ttyn, _PATH_DEV, sizeof(_PATH_DEV) - 1) == 0)
 463                 ttyn += sizeof(_PATH_DEV) - 1;
 464
 465         return ((t = getttynam(ttyn)) && t->ty_status & TTY_SECURE);
 466 }
 467
 468 static int
 469 check_user(char *name, const char *cred)
 470 {
 471         struct passwd pws, *pw;
 472         char pwbuf[1024];
 473         char *xpasswd, *salt;
 474
 475         if (isroot(name) && !rootterm(line))
 476         {
 477                 crypt("AA", "*"); /* Waste some time to simulate success */
 478                 return 0;
 479         }
 480
 481         if (getpwnam_r(name, &pws, pwbuf, sizeof(pwbuf), &pw) == 0 &&
 482             pw != NULL) {
 483                 if (pw->pw_shell == NULL) {
 484                         return 0;
 485                 }
 486
 487                 salt = pw->pw_passwd;
 488                 xpasswd = crypt(cred, salt);
 489                 /* The strcmp does not catch null passwords! */
 490                 if (*pw->pw_passwd == '\0' || strcmp(xpasswd, pw->pw_passwd)) {
 491                         return 0;
 492                 }
 493                 return 1;
 494         }
 495         return 0;
 496 }
 497 #else   /* !NOPAM */
 498
 499 /*
 500  * The following is stolen from ftpd, which stole it from the imap-uw
 501  * PAM module and login.c. It is needed because we can't really
 502  * "converse" with the user, having already gone to the trouble of
 503  * getting their username and password through an encrypted channel.
 504  */
 505
 506 #define COPY_STRING(s) (s ? strdup(s) : NULL)
 507
 508 struct cred_t {
 509         const char *uname;
 510         const char *pass;
 511 };
 512 typedef struct cred_t cred_t;
 513
 514 static int
 515 auth_conv(int num_msg, const struct pam_message **msg,
 516     struct pam_response **resp, void *appdata)
 517 {
 518         int i;
 519         cred_t *cred = appdata;
 520         struct pam_response *reply = malloc(sizeof(*reply) * num_msg);
 521
 522         if (reply == NULL)
 523                 return PAM_BUF_ERR;
 524
 525         for (i = 0; i < num_msg; i++) {
 526                 switch (msg[i]->msg_style) {
 527                 case PAM_PROMPT_ECHO_ON:        /* assume want user name */
 528                         reply[i].resp_retcode = PAM_SUCCESS;
 529                         reply[i].resp = COPY_STRING(cred->uname);
 530                         /* PAM frees resp. */
 531                         break;
 532                 case PAM_PROMPT_ECHO_OFF:       /* assume want password */
 533                     (void)strlcpy(passprompt, msg[i]->msg, SMALL_LEN);
 534                     reply[i].resp_retcode = PAM_SUCCESS;
 535                     reply[i].resp = COPY_STRING(cred->pass);
 536                     /* PAM frees resp. */
 537                     break;
 538                 case PAM_TEXT_INFO:
 539                 case PAM_ERROR_MSG:
 540                         reply[i].resp_retcode = PAM_SUCCESS;
 541                         reply[i].resp = NULL;
 542                         break;
 543                 default:                        /* unknown message style */
 544                         free(reply);
 545                         return PAM_CONV_ERR;
 546                 }
 547         }
 548
 549         *resp = reply;
 550         return PAM_SUCCESS;
 551 }
 552
 553 /*
 554  * The PAM version as a side effect may put a new username in *name.
 555  */
 556 static int
 557 check_user(char *name, const char *cred)
 558 {
 559         pam_handle_t *pamh = NULL;
 560         const void *item;
 561         int rval;
 562         int e;
 563         cred_t auth_cred = { name, cred };
 564         struct pam_conv conv = { &auth_conv, &auth_cred };
 565
 566         e = pam_start("telnetd", name, &conv, &pamh);
 567         if (e != PAM_SUCCESS) {
 568                 syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, e));
 569                 return 0;
 570         }
 571
 572 #if 0 /* Where can we find this value? */
 573         e = pam_set_item(pamh, PAM_RHOST, remotehost);
 574         if (e != PAM_SUCCESS) {
 575                 syslog(LOG_ERR, "pam_set_item(PAM_RHOST): %s",
 576                         pam_strerror(pamh, e));
 577                 return 0;
 578         }
 579 #endif
 580
 581         e = pam_authenticate(pamh, 0);
 582         switch (e) {
 583         case PAM_SUCCESS:
 584                 /*
 585                  * With PAM we support the concept of a "template"
 586                  * user.  The user enters a login name which is
 587                  * authenticated by PAM, usually via a remote service
 588                  * such as RADIUS or TACACS+.  If authentication
 589                  * succeeds, a different but related "template" name
 590                  * is used for setting the credentials, shell, and
 591                  * home directory.  The name the user enters need only
 592                  * exist on the remote authentication server, but the
 593                  * template name must be present in the local password
 594                  * database.
 595                  *
 596                  * This is supported by two various mechanisms in the
 597                  * individual modules.  However, from the application's
 598                  * point of view, the template user is always passed
 599                  * back as a changed value of the PAM_USER item.
 600                  */
 601                 if ((e = pam_get_item(pamh, PAM_USER, &item)) ==
 602                     PAM_SUCCESS) {
 603                         strlcpy(name, item, SMALL_LEN);
 604                 } else
 605                         syslog(LOG_ERR, "Couldn't get PAM_USER: %s",
 606                         pam_strerror(pamh, e));
 607 #if 0   /* pam_securetty(8) should be used to enforce this */
 608                 if (isroot(name) && !rootterm(line))
 609                         rval = 0;
 610                 else
 611 #endif
 612                         rval = 1;
 613                 break;
 614
 615         case PAM_AUTH_ERR:
 616         case PAM_USER_UNKNOWN:
 617         case PAM_MAXTRIES:
 618                 rval = 0;
 619         break;
 620
 621         default:
 622                 syslog(LOG_ERR, "auth_pam: %s", pam_strerror(pamh, e));
 623                 rval = 0;
 624                 break;
 625         }
 626
 627         if ((e = pam_end(pamh, e)) != PAM_SUCCESS) {
 628                 syslog(LOG_ERR, "pam_end: %s", pam_strerror(pamh, e));
 629                 rval = 0;
 630         }
 631         return rval;
 632 }
 633
 634 #endif /* !NOPAM */
 635
 636 #endif /* ENCRYPTION */
 637 #endif /* SRA */