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