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