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  * $FreeBSD: src/crypto/telnet/libtelnet/sra.c,v 1.1.2.7 2002/05/16 08:46:49 markm Exp $
  30  */
  31
  32 #ifdef  SRA
  33 #ifdef  ENCRYPTION
  34 #include <sys/types.h>
  35 #include <arpa/telnet.h>
  36 #include <pwd.h>
  37 #include <stdio.h>
  38 #include <stdlib.h>
  39 #include <string.h>
  40 #include <syslog.h>
  41 #include <ttyent.h>
  42
  43 #ifndef NOPAM
  44 #include <security/pam_appl.h>
  45 #else
  46 #include <unistd.h>
  47 #endif
  48
  49 #include "auth.h"
  50 #include "misc.h"
  51 #include "encrypt.h"
  52 #include "pk.h"
  53
  54 char pka[HEXKEYBYTES+1], ska[HEXKEYBYTES+1], pkb[HEXKEYBYTES+1];
  55 char *user, *pass, *xuser, *xpass;
  56 DesData ck;
  57 IdeaData ik;
  58
  59 extern int auth_debug_mode;
  60 extern char line[16];
  61
  62 static int sra_valid = 0;
  63 static int passwd_sent = 0;
  64
  65 static unsigned char str_data[1024] = {
  66         IAC, SB, TELOPT_AUTHENTICATION, 0, AUTHTYPE_SRA, };
  67
  68 #define SMALL_LEN       256
  69 #define XSMALL_LEN      513
  70
  71 #define SRA_KEY 0
  72 #define SRA_USER 1
  73 #define SRA_CONTINUE 2
  74 #define SRA_PASS 3
  75 #define SRA_ACCEPT 4
  76 #define SRA_REJECT 5
  77
  78 static int check_user(char *, const char *);
  79
  80 /* support routine to send out authentication message */
  81 static int
  82 Data(Authenticator *ap, int type, void *d, int c)
  83 {
  84         unsigned char *p = str_data + 4;
  85         unsigned char *cd = (unsigned char *)d;
  86
  87         if (c == -1)
  88                 c = strlen((char *)cd);
  89
  90         if (auth_debug_mode) {
  91                 printf("%s:%d: [%d] (%d)",
  92                         str_data[3] == TELQUAL_IS ? ">>>IS" : ">>>REPLY",
  93                         str_data[3],
  94                         type, c);
  95                 printd(d, c);
  96                 printf("\r\n");
  97         }
  98         *p++ = ap->type;
  99         *p++ = ap->way;
 100         *p++ = type;
 101         while (c-- > 0) {
 102                 if ((*p++ = *cd++) == IAC)
 103                         *p++ = IAC;
 104         }
 105         *p++ = IAC;
 106         *p++ = SE;
 107         if (str_data[3] == TELQUAL_IS)
 108                 printsub('>', &str_data[2], p - (&str_data[2]));
 109         return(net_write(str_data, p - str_data));
 110 }
 111
 112 int
 113 sra_init(Authenticator *ap __unused, int server)
 114 {
 115         if (server)
 116                 str_data[3] = TELQUAL_REPLY;
 117         else
 118                 str_data[3] = TELQUAL_IS;
 119
 120         user = malloc(SMALL_LEN);
 121         xuser = malloc(XSMALL_LEN);
 122         pass = malloc(SMALL_LEN);
 123         xpass = malloc(XSMALL_LEN);
 124
 125         if (user == NULL || xuser == NULL || pass == NULL || xpass == NULL)
 126                 return 0; /* malloc failed */
 127
 128         passwd_sent = 0;
 129
 130         genkeys(pka, ska);
 131         return(1);
 132 }
 133
 134 /* client received a go-ahead for sra */
 135 int
 136 sra_send(Authenticator *ap)
 137 {
 138         /* send PKA */
 139
 140         if (auth_debug_mode)
 141                 printf("Sent PKA to server.\r\n" );
 142         printf("Trying SRA secure login:\r\n");
 143         if (!Data(ap, SRA_KEY, (void *)pka, HEXKEYBYTES)) {
 144                 if (auth_debug_mode)
 145                         printf("Not enough room for authentication data\r\n");
 146                 return(0);
 147         }
 148
 149         return(1);
 150 }
 151
 152 /* server received an IS -- could be SRA KEY, USER, or PASS */
 153 void
 154 sra_is(Authenticator *ap, unsigned char *data, int cnt)
 155 {
 156         int valid;
 157         Session_Key skey;
 158
 159         if (cnt-- < 1)
 160                 goto bad;
 161
 162         switch (*data++) {
 163         case SRA_KEY:
 164                 if (cnt < HEXKEYBYTES) {
 165                         Data(ap, SRA_REJECT, (void *)0, 0);
 166                         auth_finished(ap, AUTH_USER);
 167                         if (auth_debug_mode)
 168                                 printf("SRA user rejected for bad PKB\r\n");
 169                         return;
 170                 }
 171                 if (auth_debug_mode)
 172                         printf("Sent pka\r\n");
 173                 if (!Data(ap, SRA_KEY, (void *)pka, HEXKEYBYTES)) {
 174                         if (auth_debug_mode)
 175                                 printf("Not enough room\r\n");
 176                         return;
 177                 }
 178                 memcpy(pkb, data, HEXKEYBYTES);
 179                 pkb[HEXKEYBYTES] = '\0';
 180                 common_key(ska, pkb, &ik, &ck);
 181                 return;
 182
 183         case SRA_USER:
 184                 /* decode KAB(u) */
 185                 if (cnt > XSMALL_LEN - 1) /* Attempted buffer overflow */
 186                         break;
 187                 memcpy(xuser, data, cnt);
 188                 xuser[cnt] = '\0';
 189                 pk_decode(xuser, user, &ck);
 190                 auth_encrypt_user(user);
 191                 Data(ap, SRA_CONTINUE, (void *)0, 0);
 192                 return;
 193
 194         case SRA_PASS:
 195                 if (cnt > XSMALL_LEN - 1) /* Attempted buffer overflow */
 196                         break;
 197                 /* decode KAB(P) */
 198                 memcpy(xpass, data, cnt);
 199                 xpass[cnt] = '\0';
 200                 pk_decode(xpass, pass, &ck);
 201
 202                 /* check user's password */
 203                 valid = check_user(user, pass);
 204
 205                 if (valid) {
 206                         Data(ap, SRA_ACCEPT, (void *)0, 0);
 207                         skey.data = ck;
 208                         skey.type = SK_DES;
 209                         skey.length = 8;
 210                         encrypt_session_key(&skey, 1);
 211
 212                         sra_valid = 1;
 213                         auth_finished(ap, AUTH_VALID);
 214                         if (auth_debug_mode)
 215                                 printf("SRA user accepted\r\n");
 216                 } else {
 217                         Data(ap, SRA_CONTINUE, (void *)0, 0);
 218 /*
 219                         Data(ap, SRA_REJECT, (void *)0, 0);
 220                         sra_valid = 0;
 221                         auth_finished(ap, AUTH_REJECT);
 222 */
 223                         if (auth_debug_mode)
 224                                 printf("SRA user failed\r\n");
 225                 }
 226                 return;
 227
 228         default:
 229                 if (auth_debug_mode)
 230                         printf("Unknown SRA option %d\r\n", data[-1]);
 231         }
 232
 233 bad:
 234         Data(ap, SRA_REJECT, 0, 0);
 235         sra_valid = 0;
 236         auth_finished(ap, AUTH_REJECT);
 237 }
 238
 239 /* client received REPLY -- could be SRA KEY, CONTINUE, ACCEPT, or REJECT */
 240 void
 241 sra_reply(Authenticator *ap, unsigned char *data, int cnt)
 242 {
 243         char uprompt[SMALL_LEN], tuser[SMALL_LEN];
 244         Session_Key skey;
 245         size_t i;
 246
 247         if (cnt-- < 1)
 248                 return;
 249
 250         switch (*data++) {
 251         case SRA_KEY:
 252                 /* calculate common key */
 253                 if (cnt < HEXKEYBYTES) {
 254                         if (auth_debug_mode)
 255                                 printf("SRA user rejected for bad PKB\r\n");
 256                         return;
 257                 }
 258                 memcpy(pkb, data, HEXKEYBYTES);
 259                 pkb[HEXKEYBYTES] = '\0';
 260                 common_key(ska, pkb, &ik, &ck);
 261
 262 enc_user:
 263                 /* encode user */
 264                 memset(tuser, 0, sizeof(tuser));
 265                 sprintf(uprompt, "User (%s): ", UserNameRequested);
 266                 if (telnet_gets(uprompt, tuser, SMALL_LEN-1, 1) == NULL) {
 267                         printf("\n");
 268                         exit(1);
 269                 }
 270                 if (tuser[0] == '\n' || tuser[0] == '\r' ) {
 271                         strlcpy(user, UserNameRequested, SMALL_LEN);
 272                 } else {
 273                         /* telnet_gets leaves the newline on */
 274                         for (i = 0; i < sizeof(tuser); i++) {
 275                                 if (tuser[i] == '\n') {
 276                                         tuser[i] = '\0';
 277                                         break;
 278                                 }
 279                         }
 280                         strlcpy(user, tuser, SMALL_LEN);
 281                 }
 282                 pk_encode(user, xuser, &ck);
 283
 284                 /* send it off */
 285                 if (auth_debug_mode)
 286                         printf("Sent KAB(U)\r\n");
 287                 if (!Data(ap, SRA_USER, xuser, strlen(xuser))) {
 288                         if (auth_debug_mode)
 289                                 printf("Not enough room\r\n");
 290                         return;
 291                 }
 292                 break;
 293
 294         case SRA_CONTINUE:
 295                 if (passwd_sent) {
 296                         passwd_sent = 0;
 297                         printf("[ SRA login failed ]\r\n");
 298                         goto enc_user;
 299                 }
 300                 /* encode password */
 301                 memset(pass, 0, SMALL_LEN);
 302                 if (telnet_gets("Password: ", pass, SMALL_LEN-1, 0) == NULL) {
 303                         printf("\n");
 304                         exit(1);
 305                 }
 306                 pk_encode(pass, xpass, &ck);
 307                 /* send it off */
 308                 if (auth_debug_mode)
 309                         printf("Sent KAB(P)\r\n");
 310                 if (!Data(ap, SRA_PASS, xpass, strlen(xpass))) {
 311                         if (auth_debug_mode)
 312                                 printf("Not enough room\r\n");
 313                         return;
 314                 }
 315                 passwd_sent = 1;
 316                 break;
 317
 318         case SRA_REJECT:
 319                 printf("[ SRA refuses authentication ]\r\n");
 320                 printf("Trying plaintext login:\r\n");
 321                 auth_finished(0, AUTH_REJECT);
 322                 return;
 323
 324         case SRA_ACCEPT:
 325                 printf("[ SRA accepts you ]\r\n");
 326                 skey.data = ck;
 327                 skey.type = SK_DES;
 328                 skey.length = 8;
 329                 encrypt_session_key(&skey, 0);
 330                 auth_finished(ap, AUTH_VALID);
 331                 return;
 332
 333         default:
 334                 if (auth_debug_mode)
 335                         printf("Unknown SRA option %d\r\n", data[-1]);
 336                 return;
 337         }
 338 }
 339
 340 int
 341 sra_status(Authenticator *ap __unused, char *name, int level)
 342 {
 343         if (level < AUTH_USER)
 344                 return(level);
 345         if (UserNameRequested && sra_valid) {
 346                 strcpy(name, UserNameRequested);
 347                 return(AUTH_VALID);
 348         } else {
 349                 return(AUTH_USER);
 350         }
 351 }
 352
 353 #define BUMP(buf, len)          while (*(buf)) { ++(buf), --(len); }
 354 #define ADDC(buf, len, c)       if ((len) > 0) { *(buf)++ = (c); --(len); }
 355
 356 void
 357 sra_printsub(unsigned char *data, int cnt, unsigned char *ubuf, int buflen)
 358 {
 359         char lbuf[32], *buf = (char *)ubuf;
 360         int i;
 361
 362         buf[buflen-1] = '\0';           /* make sure its NULL terminated */
 363         buflen -= 1;
 364
 365         switch (data[3]) {
 366         case SRA_CONTINUE:
 367                 strncpy(buf, " CONTINUE ", buflen);
 368                 goto common;
 369
 370         case SRA_REJECT:                /* Rejected (reason might follow) */
 371                 strncpy(buf, " REJECT ", buflen);
 372                 goto common;
 373
 374         case SRA_ACCEPT:                /* Accepted (name might follow) */
 375                 strncpy(buf, " ACCEPT ", buflen);
 376
 377 common:
 378                 BUMP(buf, buflen);
 379                 if (cnt <= 4)
 380                         break;
 381                 ADDC(buf, buflen, '"');
 382                 for (i = 4; i < cnt; i++)
 383                         ADDC(buf, buflen, data[i]);
 384                 ADDC(buf, buflen, '"');
 385                 ADDC(buf, buflen, '\0');
 386                 break;
 387
 388         case SRA_KEY:                   /* Authentication data follows */
 389                 strncpy(buf, " KEY ", buflen);
 390                 goto common2;
 391
 392         case SRA_USER:
 393                 strncpy(buf, " USER ", buflen);
 394                 goto common2;
 395
 396         case SRA_PASS:
 397                 strncpy(buf, " PASS ", buflen);
 398                 goto common2;
 399
 400         default:
 401                 snprintf(lbuf, sizeof(lbuf), " %d (unknown)", data[3]);
 402                 strncpy(buf, lbuf, buflen);
 403
 404 common2:
 405                 BUMP(buf, buflen);
 406                 for (i = 4; i < cnt; i++) {
 407                         snprintf(lbuf, sizeof(lbuf), " %d", data[i]);
 408                         strncpy(buf, lbuf, buflen);
 409                         BUMP(buf, buflen);
 410                 }
 411                 break;
 412         }
 413 }
 414
 415 #ifdef NOPAM
 416
 417 static int
 418 isroot(const char *usr)
 419 {
 420         struct passwd pws, *pwd;
 421         char pwbuf[1024];
 422
 423         if (getpwnam_r(usr, &pws, pwbuf, sizeof(pwbuf), &pwd) != 0 ||
 424             pwd == NULL)
 425                 return 0;
 426
 427         return (!pwd->pw_uid);
 428 }
 429
 430 static int
 431 rootterm(const char *ttyn)
 432 {
 433         struct ttyent *t;
 434
 435         return ((t = getttynam(ttyn)) && t->ty_status & TTY_SECURE);
 436 }
 437
 438 static int
 439 check_user(char *name, const char *cred)
 440 {
 441         struct passwd pws, *pw;
 442         char pwbuf[1024];
 443         char *xpasswd, *salt;
 444
 445         if (isroot(name) && !rootterm(line)) {
 446                 crypt("AA", "*"); /* Waste some time to simulate success */
 447                 return(0);
 448         }
 449
 450         if (getpwnam_r(name, &pws, pwbuf, sizeof(pwbuf), &pw) == 0 &&
 451             pw != NULL) {
 452                 if (pw->pw_shell == NULL)
 453                         return(0);
 454
 455                 salt = pw->pw_passwd;
 456                 xpasswd = crypt(cred, salt);
 457                 /* The strcmp does not catch null passwords! */
 458                 if (*pw->pw_passwd == '\0' || strcmp(xpasswd, pw->pw_passwd))
 459                         return(0);
 460
 461                 return(1);
 462         }
 463         return(0);
 464 }
 465
 466 #else /* !NOPAM */
 467
 468 /*
 469  * The following is stolen from ftpd, which stole it from the imap-uw
 470  * PAM module and login.c. It is needed because we can't really
 471  * "converse" with the user, having already gone to the trouble of
 472  * getting their username and password through an encrypted channel.
 473  */
 474
 475 #define COPY_STRING(s) (s ? strdup(s) : NULL)
 476
 477 struct cred_t {
 478         const char *uname;
 479         const char *pass;
 480 };
 481 typedef struct cred_t cred_t;
 482
 483 static int
 484 auth_conv(int num_msg, const struct pam_message **msg,
 485           struct pam_response **resp, void *appdata)
 486 {
 487         int i;
 488         cred_t *cred = appdata;
 489         struct pam_response *reply = malloc(sizeof(*reply) * num_msg);
 490
 491         if (reply == NULL)
 492                 return PAM_BUF_ERR;
 493
 494         for (i = 0; i < num_msg; i++) {
 495                 switch (msg[i]->msg_style) {
 496                 case PAM_PROMPT_ECHO_ON:        /* assume want user name */
 497                         reply[i].resp_retcode = PAM_SUCCESS;
 498                         reply[i].resp = COPY_STRING(cred->uname);
 499                         /* PAM frees resp. */
 500                         break;
 501                 case PAM_PROMPT_ECHO_OFF:       /* assume want password */
 502                         reply[i].resp_retcode = PAM_SUCCESS;
 503                         reply[i].resp = COPY_STRING(cred->pass);
 504                         /* PAM frees resp. */
 505                         break;
 506                 case PAM_TEXT_INFO:
 507                 case PAM_ERROR_MSG:
 508                         reply[i].resp_retcode = PAM_SUCCESS;
 509                         reply[i].resp = NULL;
 510                         break;
 511                 default:                        /* unknown message style */
 512                         free(reply);
 513                         return PAM_CONV_ERR;
 514                 }
 515         }
 516
 517         *resp = reply;
 518         return PAM_SUCCESS;
 519 }
 520
 521 /*
 522  * The PAM version as a side effect may put a new username in *name.
 523  */
 524 static int
 525 check_user(char *name, const char *cred)
 526 {
 527         pam_handle_t *pamh = NULL;
 528         const void *item;
 529         int rval;
 530         int e;
 531         cred_t auth_cred = { name, cred };
 532         struct pam_conv conv = { &auth_conv, &auth_cred };
 533
 534         e = pam_start("telnetd", name, &conv, &pamh);
 535         if (e != PAM_SUCCESS) {
 536                 syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, e));
 537                 return 0;
 538         }
 539
 540 #if 0 /* Where can we find this value? */
 541         e = pam_set_item(pamh, PAM_RHOST, remotehost);
 542         if (e != PAM_SUCCESS) {
 543                 syslog(LOG_ERR, "pam_set_item(PAM_RHOST): %s",
 544                         pam_strerror(pamh, e));
 545                 return 0;
 546         }
 547 #endif
 548
 549         e = pam_authenticate(pamh, 0);
 550         switch (e) {
 551         case PAM_SUCCESS:
 552                 /*
 553                  * With PAM we support the concept of a "template"
 554                  * user.  The user enters a login name which is
 555                  * authenticated by PAM, usually via a remote service
 556                  * such as RADIUS or TACACS+.  If authentication
 557                  * succeeds, a different but related "template" name
 558                  * is used for setting the credentials, shell, and
 559                  * home directory.  The name the user enters need only
 560                  * exist on the remote authentication server, but the
 561                  * template name must be present in the local password
 562                  * database.
 563                  *
 564                  * This is supported by two various mechanisms in the
 565                  * individual modules.  However, from the application's
 566                  * point of view, the template user is always passed
 567                  * back as a changed value of the PAM_USER item.
 568                  */
 569                 if ((e = pam_get_item(pamh, PAM_USER,
 570                                       &item)) == PAM_SUCCESS)
 571                         strlcpy(name, item, SMALL_LEN);
 572                 else
 573                         syslog(LOG_ERR, "Couldn't get PAM_USER: %s",
 574                                pam_strerror(pamh, e));
 575
 576                 rval = 1;
 577 #if 0   /* pam_securetty(8) should be used to enforce this */
 578                 if (isroot(name) && !rootterm(line))
 579                         rval = 0;
 580 #endif
 581                 break;
 582
 583         case PAM_AUTH_ERR:
 584         case PAM_USER_UNKNOWN:
 585         case PAM_MAXTRIES:
 586                 rval = 0;
 587                 break;
 588
 589         default:
 590                 syslog(LOG_ERR, "auth_pam: %s", pam_strerror(pamh, e));
 591                 rval = 0;
 592                 break;
 593         }
 594
 595         if ((e = pam_end(pamh, e)) != PAM_SUCCESS) {
 596                 syslog(LOG_ERR, "pam_end: %s", pam_strerror(pamh, e));
 597                 rval = 0;
 598         }
 599         return rval;
 600 }
 601
 602 #endif /* !NOPAM */
 603
 604 #endif /* ENCRYPTION */
 605 #endif /* SRA */