src/libs/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 __FBSDID("$FreeBSD: src/contrib/telnet/libtelnet/sra.c,v 1.16 2002/05/06 09:48:02 markm Exp $");
  34
  35 #ifdef  SRA
  36 #ifdef  ENCRYPTION
  37 #include <sys/types.h>
  38 #include <arpa/telnet.h>
  39 #include <pwd.h>
  40 #include <stdio.h>
  41 #include <stdlib.h>
  42 #include <string.h>
  43 #include <syslog.h>
  44 #include <ttyent.h>
  45
  46 #ifndef NOPAM
  47 #include <security/pam_appl.h>
  48 #else
  49 #include <unistd.h>
  50 #endif
  51
  52 #include "auth.h"
  53 #include "misc.h"
  54 #include "encrypt.h"
  55 #include "pk.h"
  56
  57 char pka[HEXKEYBYTES+1], ska[HEXKEYBYTES+1], pkb[HEXKEYBYTES+1];
  58 char *user, *pass, *xuser, *xpass;
  59 DesData ck;
  60 IdeaData ik;
  61
  62 extern int auth_debug_mode;
  63 extern char line[];
  64
  65 static int sra_valid = 0;
  66 static int passwd_sent = 0;
  67
  68 static unsigned char str_data[1024] = { IAC, SB, TELOPT_AUTHENTICATION, 0,
  69                                         AUTHTYPE_SRA, };
  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 *, 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 = (char *)malloc(256);
 121         xuser = (char *)malloc(513);
 122         pass = (char *)malloc(256);
 123         xpass = (char *)malloc(513);
 124
 125         if (user == NULL || xuser == NULL || pass == NULL || xpass ==
 126         NULL)
 127                 return 0; /* malloc failed */
 128
 129         passwd_sent = 0;
 130
 131         genkeys(pka,ska);
 132         return(1);
 133 }
 134
 135 /* client received a go-ahead for sra */
 136 int
 137 sra_send(Authenticator *ap)
 138 {
 139         /* send PKA */
 140
 141         if (auth_debug_mode)
 142                 printf("Sent PKA to server.\r\n" );
 143         printf("Trying SRA secure login:\r\n");
 144         if (!Data(ap, SRA_KEY, (void *)pka, HEXKEYBYTES)) {
 145                 if (auth_debug_mode)
 146                         printf("Not enough room for authentication data\r\n");
 147                 return(0);
 148         }
 149
 150         return(1);
 151 }
 152
 153 /* server received an IS -- could be SRA KEY, USER, or PASS */
 154 void
 155 sra_is(Authenticator *ap, unsigned char *data, int cnt)
 156 {
 157         int valid;
 158         Session_Key skey;
 159
 160         if (cnt-- < 1)
 161                 goto bad;
 162         switch (*data++) {
 163
 164         case SRA_KEY:
 165                 if (cnt < HEXKEYBYTES) {
 166                         Data(ap, SRA_REJECT, (void *)0, 0);
 167                         auth_finished(ap, AUTH_USER);
 168                         if (auth_debug_mode) {
 169                                 printf("SRA user rejected for bad PKB\r\n");
 170                         }
 171                         return;
 172                 }
 173                 if (auth_debug_mode)
 174                         printf("Sent pka\r\n");
 175                 if (!Data(ap, SRA_KEY, (void *)pka, HEXKEYBYTES)) {
 176                         if (auth_debug_mode)
 177                                 printf("Not enough room\r\n");
 178                         return;
 179                 }
 180                 memcpy(pkb,data,HEXKEYBYTES);
 181                 pkb[HEXKEYBYTES] = '\0';
 182                 common_key(ska,pkb,&ik,&ck);
 183                 return;
 184
 185         case SRA_USER:
 186                 /* decode KAB(u) */
 187                 if (cnt > 512) /* Attempted buffer overflow */
 188                         break;
 189                 memcpy(xuser,data,cnt);
 190                 xuser[cnt] = '\0';
 191                 pk_decode(xuser,user,&ck);
 192                 auth_encrypt_user(user);
 193                 Data(ap, SRA_CONTINUE, (void *)0, 0);
 194
 195                 return;
 196
 197         case SRA_PASS:
 198                 if (cnt > 512) /* Attempted buffer overflow */
 199                         break;
 200                 /* decode KAB(P) */
 201                 memcpy(xpass,data,cnt);
 202                 xpass[cnt] = '\0';
 203                 pk_decode(xpass,pass,&ck);
 204
 205                 /* check user's password */
 206                 valid = check_user(user,pass);
 207
 208                 if(valid) {
 209                         Data(ap, SRA_ACCEPT, (void *)0, 0);
 210                         skey.data = ck;
 211                         skey.type = SK_DES;
 212                         skey.length = 8;
 213                         encrypt_session_key(&skey, 1);
 214
 215                         sra_valid = 1;
 216                         auth_finished(ap, AUTH_VALID);
 217                         if (auth_debug_mode) {
 218                                 printf("SRA user accepted\r\n");
 219                         }
 220                 }
 221                 else {
 222                         Data(ap, SRA_CONTINUE, (void *)0, 0);
 223 /*
 224                         Data(ap, SRA_REJECT, (void *)0, 0);
 225                         sra_valid = 0;
 226                         auth_finished(ap, AUTH_REJECT);
 227 */
 228                         if (auth_debug_mode) {
 229                                 printf("SRA user failed\r\n");
 230                         }
 231                 }
 232                 return;
 233
 234         default:
 235                 if (auth_debug_mode)
 236                         printf("Unknown SRA option %d\r\n", data[-1]);
 237         }
 238 bad:
 239         Data(ap, SRA_REJECT, 0, 0);
 240         sra_valid = 0;
 241         auth_finished(ap, AUTH_REJECT);
 242 }
 243
 244 /* client received REPLY -- could be SRA KEY, CONTINUE, ACCEPT, or REJECT */
 245 void
 246 sra_reply(Authenticator *ap, unsigned char *data, int cnt)
 247 {
 248         char uprompt[256],tuser[256];
 249         Session_Key skey;
 250         size_t i;
 251
 252         if (cnt-- < 1)
 253                 return;
 254         switch (*data++) {
 255
 256         case SRA_KEY:
 257                 /* calculate common key */
 258                 if (cnt < HEXKEYBYTES) {
 259                         if (auth_debug_mode) {
 260                                 printf("SRA user rejected for bad PKB\r\n");
 261                         }
 262                         return;
 263                 }
 264                 memcpy(pkb,data,HEXKEYBYTES);
 265                 pkb[HEXKEYBYTES] = '\0';
 266
 267                 common_key(ska,pkb,&ik,&ck);
 268
 269         enc_user:
 270
 271                 /* encode user */
 272                 memset(tuser,0,sizeof(tuser));
 273                 sprintf(uprompt,"User (%s): ",UserNameRequested);
 274                 telnet_gets(uprompt,tuser,255,1);
 275                 if (tuser[0] == '\n' || tuser[0] == '\r' )
 276                         strcpy(user,UserNameRequested);
 277                 else {
 278                         /* telnet_gets leaves the newline on */
 279                         for(i=0;i<sizeof(tuser);i++) {
 280                                 if (tuser[i] == '\n') {
 281                                         tuser[i] = '\0';
 282                                         break;
 283                                 }
 284                         }
 285                         strcpy(user,tuser);
 286                 }
 287                 pk_encode(user,xuser,&ck);
 288
 289                 /* send it off */
 290                 if (auth_debug_mode)
 291                         printf("Sent KAB(U)\r\n");
 292                 if (!Data(ap, SRA_USER, (void *)xuser, strlen(xuser))) {
 293                         if (auth_debug_mode)
 294                                 printf("Not enough room\r\n");
 295                         return;
 296                 }
 297                 break;
 298
 299         case SRA_CONTINUE:
 300                 if (passwd_sent) {
 301                         passwd_sent = 0;
 302                         printf("[ SRA login failed ]\r\n");
 303                         goto enc_user;
 304                 }
 305                 /* encode password */
 306                 memset(pass,0,sizeof(pass));
 307                 telnet_gets("Password: ",pass,255,0);
 308                 pk_encode(pass,xpass,&ck);
 309                 /* send it off */
 310                 if (auth_debug_mode)
 311                         printf("Sent KAB(P)\r\n");
 312                 if (!Data(ap, SRA_PASS, (void *)xpass, strlen(xpass))) {
 313                         if (auth_debug_mode)
 314                                 printf("Not enough room\r\n");
 315                         return;
 316                 }
 317                 passwd_sent = 1;
 318                 break;
 319
 320         case SRA_REJECT:
 321                 printf("[ SRA refuses authentication ]\r\n");
 322                 printf("Trying plaintext login:\r\n");
 323                 auth_finished(0,AUTH_REJECT);
 324                 return;
 325
 326         case SRA_ACCEPT:
 327                 printf("[ SRA accepts you ]\r\n");
 328                 skey.data = ck;
 329                 skey.type = SK_DES;
 330                 skey.length = 8;
 331                 encrypt_session_key(&skey, 0);
 332
 333                 auth_finished(ap, AUTH_VALID);
 334                 return;
 335         default:
 336                 if (auth_debug_mode)
 337                         printf("Unknown SRA option %d\r\n", data[-1]);
 338                 return;
 339         }
 340 }
 341
 342 int
 343 sra_status(Authenticator *ap __unused, char *name, int level)
 344 {
 345         if (level < AUTH_USER)
 346                 return(level);
 347         if (UserNameRequested && sra_valid) {
 348                 strcpy(name, UserNameRequested);
 349                 return(AUTH_VALID);
 350         } else
 351                 return(AUTH_USER);
 352 }
 353
 354 #define BUMP(buf, len)          while (*(buf)) {++(buf), --(len);}
 355 #define ADDC(buf, len, c)       if ((len) > 0) {*(buf)++ = (c); --(len);}
 356
 357 void
 358 sra_printsub(unsigned char *data, int cnt, unsigned char *buf, int buflen)
 359 {
 360         char lbuf[32];
 361         int i;
 362
 363         buf[buflen-1] = '\0';           /* make sure its NULL terminated */
 364         buflen -= 1;
 365
 366         switch(data[3]) {
 367
 368         case SRA_CONTINUE:
 369                 strncpy((char *)buf, " CONTINUE ", buflen);
 370                 goto common;
 371
 372         case SRA_REJECT:                /* Rejected (reason might follow) */
 373                 strncpy((char *)buf, " REJECT ", buflen);
 374                 goto common;
 375
 376         case SRA_ACCEPT:                /* Accepted (name might follow) */
 377                 strncpy((char *)buf, " ACCEPT ", buflen);
 378
 379         common:
 380                 BUMP(buf, buflen);
 381                 if (cnt <= 4)
 382                         break;
 383                 ADDC(buf, buflen, '"');
 384                 for (i = 4; i < cnt; i++)
 385                         ADDC(buf, buflen, data[i]);
 386                 ADDC(buf, buflen, '"');
 387                 ADDC(buf, buflen, '\0');
 388                 break;
 389
 390         case SRA_KEY:                   /* Authentication data follows */
 391                 strncpy((char *)buf, " KEY ", buflen);
 392                 goto common2;
 393
 394         case SRA_USER:
 395                 strncpy((char *)buf, " USER ", buflen);
 396                 goto common2;
 397
 398         case SRA_PASS:
 399                 strncpy((char *)buf, " PASS ", buflen);
 400                 goto common2;
 401
 402         default:
 403                 sprintf(lbuf, " %d (unknown)", data[3]);
 404                 strncpy((char *)buf, lbuf, buflen);
 405         common2:
 406                 BUMP(buf, buflen);
 407                 for (i = 4; i < cnt; i++) {
 408                         sprintf(lbuf, " %d", data[i]);
 409                         strncpy((char *)buf, lbuf, buflen);
 410                         BUMP(buf, buflen);
 411                 }
 412                 break;
 413         }
 414 }
 415
 416 static int
 417 isroot(const char *usr)
 418 {
 419         struct passwd *pwd;
 420
 421         if ((pwd=getpwnam(usr))==NULL)
 422                 return 0;
 423         return (!pwd->pw_uid);
 424 }
 425
 426 static int
 427 rootterm(char *ttyn)
 428 {
 429         struct ttyent *t;
 430
 431         return ((t = getttynam(ttyn)) && t->ty_status & TTY_SECURE);
 432 }
 433
 434 #ifdef NOPAM
 435 static int
 436 check_user(char *name, char *cred)
 437 {
 438         char *cp;
 439         char *xpasswd, *salt;
 440
 441         if (isroot(name) && !rootterm(line))
 442         {
 443                 crypt("AA","*"); /* Waste some time to simulate success */
 444                 return(0);
 445         }
 446
 447         if (pw = sgetpwnam(name)) {
 448                 if (pw->pw_shell == NULL) {
 449                         pw = (struct passwd *) NULL;
 450                         return(0);
 451                 }
 452
 453                 salt = pw->pw_passwd;
 454                 xpasswd = crypt(cred, salt);
 455                 /* The strcmp does not catch null passwords! */
 456                 if (pw == NULL || *pw->pw_passwd == '\0' ||
 457                         strcmp(xpasswd, pw->pw_passwd)) {
 458                         pw = (struct passwd *) NULL;
 459                         return(0);
 460                 }
 461                 return(1);
 462         }
 463         return(0);
 464 }
 465 #else
 466
 467 /*
 468  * The following is stolen from ftpd, which stole it from the imap-uw
 469  * PAM module and login.c. It is needed because we can't really
 470  * "converse" with the user, having already gone to the trouble of
 471  * getting their username and password through an encrypted channel.
 472  */
 473
 474 #define COPY_STRING(s) (s ? strdup(s):NULL)
 475
 476 struct cred_t {
 477         const char *uname;
 478         const char *pass;
 479 };
 480 typedef struct cred_t cred_t;
 481
 482 static int
 483 auth_conv(int num_msg, const struct pam_message **msg, struct pam_response **resp, void *appdata)
 484 {
 485         int i;
 486         cred_t *cred = (cred_t *) appdata;
 487         struct pam_response *reply =
 488                 malloc(sizeof(struct pam_response) * num_msg);
 489
 490         if (reply == NULL)
 491                 return PAM_BUF_ERR;
 492
 493         for (i = 0; i < num_msg; i++) {
 494                 switch (msg[i]->msg_style) {
 495                 case PAM_PROMPT_ECHO_ON:        /* assume want user name */
 496                         reply[i].resp_retcode = PAM_SUCCESS;
 497                         reply[i].resp = COPY_STRING(cred->uname);
 498                         /* PAM frees resp. */
 499                         break;
 500                 case PAM_PROMPT_ECHO_OFF:       /* assume want password */
 501                         reply[i].resp_retcode = PAM_SUCCESS;
 502                         reply[i].resp = COPY_STRING(cred->pass);
 503                         /* PAM frees resp. */
 504                         break;
 505                 case PAM_TEXT_INFO:
 506                 case PAM_ERROR_MSG:
 507                         reply[i].resp_retcode = PAM_SUCCESS;
 508                         reply[i].resp = NULL;
 509                         break;
 510                 default:                        /* unknown message style */
 511                         free(reply);
 512                         return PAM_CONV_ERR;
 513                 }
 514         }
 515
 516         *resp = reply;
 517         return PAM_SUCCESS;
 518 }
 519
 520 /*
 521  * The PAM version as a side effect may put a new username in *name.
 522  */
 523 static int
 524 check_user(char *name, char *cred)
 525 {
 526         pam_handle_t *pamh = NULL;
 527         const void *item;
 528         int rval;
 529         int e;
 530         cred_t auth_cred = { name, cred };
 531         struct pam_conv conv = { &auth_conv, &auth_cred };
 532
 533         e = pam_start("telnetd", name, &conv, &pamh);
 534         if (e != PAM_SUCCESS) {
 535                 syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, e));
 536                 return 0;
 537         }
 538
 539 #if 0 /* Where can we find this value? */
 540         e = pam_set_item(pamh, PAM_RHOST, remotehost);
 541         if (e != PAM_SUCCESS) {
 542                 syslog(LOG_ERR, "pam_set_item(PAM_RHOST): %s",
 543                         pam_strerror(pamh, e));
 544                 return 0;
 545         }
 546 #endif
 547
 548         e = pam_authenticate(pamh, 0);
 549         switch (e) {
 550         case PAM_SUCCESS:
 551                 /*
 552                  * With PAM we support the concept of a "template"
 553                  * user.  The user enters a login name which is
 554                  * authenticated by PAM, usually via a remote service
 555                  * such as RADIUS or TACACS+.  If authentication
 556                  * succeeds, a different but related "template" name
 557                  * is used for setting the credentials, shell, and
 558                  * home directory.  The name the user enters need only
 559                  * exist on the remote authentication server, but the
 560                  * template name must be present in the local password
 561                  * database.
 562                  *
 563                  * This is supported by two various mechanisms in the
 564                  * individual modules.  However, from the application's
 565                  * point of view, the template user is always passed
 566                  * back as a changed value of the PAM_USER item.
 567                  */
 568                 if ((e = pam_get_item(pamh, PAM_USER, &item)) ==
 569                     PAM_SUCCESS) {
 570                         strcpy(name, item);
 571                 } else
 572                         syslog(LOG_ERR, "Couldn't get PAM_USER: %s",
 573                         pam_strerror(pamh, e));
 574                 if (isroot(name) && !rootterm(line))
 575                         rval = 0;
 576                 else
 577                         rval = 1;
 578                 break;
 579
 580         case PAM_AUTH_ERR:
 581         case PAM_USER_UNKNOWN:
 582         case PAM_MAXTRIES:
 583                 rval = 0;
 584         break;
 585
 586         default:
 587                 syslog(LOG_ERR, "auth_pam: %s", pam_strerror(pamh, e));
 588                 rval = 0;
 589                 break;
 590         }
 591
 592         if ((e = pam_end(pamh, e)) != PAM_SUCCESS) {
 593                 syslog(LOG_ERR, "pam_end: %s", pam_strerror(pamh, e));
 594                 rval = 0;
 595         }
 596         return rval;
 597 }
 598
 599 #endif
 600
 601 #endif /* ENCRYPTION */
 602 #endif /* SRA */