contrib/cygtermd/telnet.c

   1 /*
   2  * Simple Telnet server code, adapted from PuTTY's own Telnet
   3  * client code for use as a Cygwin local pty proxy.
   4  */
   5
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <string.h>
   9
  10 #include "sel.h"
  11 #include "telnet.h"
  12 #include "malloc.h"
  13 #include "pty.h"
  14
  15 #ifndef FALSE
  16 #define FALSE 0
  17 #endif
  18 #ifndef TRUE
  19 #define TRUE 1
  20 #endif
  21
  22 #define IAC     255                    /* interpret as command: */
  23 #define DONT    254                    /* you are not to use option */
  24 #define DO      253                    /* please, you use option */
  25 #define WONT    252                    /* I won't use option */
  26 #define WILL    251                    /* I will use option */
  27 #define SB      250                    /* interpret as subnegotiation */
  28 #define SE      240                    /* end sub negotiation */
  29
  30 #define GA      249                    /* you may reverse the line */
  31 #define EL      248                    /* erase the current line */
  32 #define EC      247                    /* erase the current character */
  33 #define AYT     246                    /* are you there */
  34 #define AO      245                    /* abort output--but let prog finish */
  35 #define IP      244                    /* interrupt process--permanently */
  36 #define BREAK   243                    /* break */
  37 #define DM      242                    /* data mark--for connect. cleaning */
  38 #define NOP     241                    /* nop */
  39 #define EOR     239                    /* end of record (transparent mode) */
  40 #define ABORT   238                    /* Abort process */
  41 #define SUSP    237                    /* Suspend process */
  42 #define xEOF    236                    /* End of file: EOF is already used... */
  43
  44 #define TELOPTS(X) \
  45     X(BINARY, 0)                       /* 8-bit data path */ \
  46     X(ECHO, 1)                         /* echo */ \
  47     X(RCP, 2)                          /* prepare to reconnect */ \
  48     X(SGA, 3)                          /* suppress go ahead */ \
  49     X(NAMS, 4)                         /* approximate message size */ \
  50     X(STATUS, 5)                       /* give status */ \
  51     X(TM, 6)                           /* timing mark */ \
  52     X(RCTE, 7)                         /* remote controlled transmission and echo */ \
  53     X(NAOL, 8)                         /* negotiate about output line width */ \
  54     X(NAOP, 9)                         /* negotiate about output page size */ \
  55     X(NAOCRD, 10)                      /* negotiate about CR disposition */ \
  56     X(NAOHTS, 11)                      /* negotiate about horizontal tabstops */ \
  57     X(NAOHTD, 12)                      /* negotiate about horizontal tab disposition */ \
  58     X(NAOFFD, 13)                      /* negotiate about formfeed disposition */ \
  59     X(NAOVTS, 14)                      /* negotiate about vertical tab stops */ \
  60     X(NAOVTD, 15)                      /* negotiate about vertical tab disposition */ \
  61     X(NAOLFD, 16)                      /* negotiate about output LF disposition */ \
  62     X(XASCII, 17)                      /* extended ascic character set */ \
  63     X(LOGOUT, 18)                      /* force logout */ \
  64     X(BM, 19)                          /* byte macro */ \
  65     X(DET, 20)                         /* data entry terminal */ \
  66     X(SUPDUP, 21)                      /* supdup protocol */ \
  67     X(SUPDUPOUTPUT, 22)                /* supdup output */ \
  68     X(SNDLOC, 23)                      /* send location */ \
  69     X(TTYPE, 24)                       /* terminal type */ \
  70     X(EOR, 25)                         /* end or record */ \
  71     X(TUID, 26)                        /* TACACS user identification */ \
  72     X(OUTMRK, 27)                      /* output marking */ \
  73     X(TTYLOC, 28)                      /* terminal location number */ \
  74     X(3270REGIME, 29)                  /* 3270 regime */ \
  75     X(X3PAD, 30)                       /* X.3 PAD */ \
  76     X(NAWS, 31)                        /* window size */ \
  77     X(TSPEED, 32)                      /* terminal speed */ \
  78     X(LFLOW, 33)                       /* remote flow control */ \
  79     X(LINEMODE, 34)                    /* Linemode option */ \
  80     X(XDISPLOC, 35)                    /* X Display Location */ \
  81     X(OLD_ENVIRON, 36)                 /* Old - Environment variables */ \
  82     X(AUTHENTICATION, 37)              /* Authenticate */ \
  83     X(ENCRYPT, 38)                     /* Encryption option */ \
  84     X(NEW_ENVIRON, 39)                 /* New - Environment variables */ \
  85     X(TN3270E, 40)                     /* TN3270 enhancements */ \
  86     X(XAUTH, 41)                       \
  87     X(CHARSET, 42)                     /* Character set */ \
  88     X(RSP, 43)                         /* Remote serial port */ \
  89     X(COM_PORT_OPTION, 44)             /* Com port control */ \
  90     X(SLE, 45)                         /* Suppress local echo */ \
  91     X(STARTTLS, 46)                    /* Start TLS */ \
  92     X(KERMIT, 47)                      /* Automatic Kermit file transfer */ \
  93     X(SEND_URL, 48)                    \
  94     X(FORWARD_X, 49)                   \
  95     X(PRAGMA_LOGON, 138)               \
  96     X(SSPI_LOGON, 139)                 \
  97     X(PRAGMA_HEARTBEAT, 140)           \
  98     X(EXOPL, 255)                      /* extended-options-list */
  99
 100 #define telnet_enum(x,y) TELOPT_##x = y,
 101 enum { TELOPTS(telnet_enum) dummy=0 };
 102 #undef telnet_enum
 103
 104 #define TELQUAL_IS      0              /* option is... */
 105 #define TELQUAL_SEND    1              /* send option */
 106 #define TELQUAL_INFO    2              /* ENVIRON: informational version of IS */
 107 #define BSD_VAR 1
 108 #define BSD_VALUE 0
 109 #define RFC_VAR 0
 110 #define RFC_VALUE 1
 111
 112 #define CR 13
 113 #define LF 10
 114 #define NUL 0
 115
 116 #define iswritable(x) ( (x) != IAC && (x) != CR )
 117
 118 static char *telopt(int opt)
 119 {
 120 #define telnet_str(x,y) case TELOPT_##x: return #x;
 121     switch (opt) {
 122         TELOPTS(telnet_str)
 123       default:
 124         return "<unknown>";
 125     }
 126 #undef telnet_str
 127 }
 128
 129 static void telnet_size(void *handle, int width, int height);
 130
 131 struct Opt {
 132     int send;                          /* what we initially send */
 133     int nsend;                         /* -ve send if requested to stop it */
 134     int ack, nak;                      /* +ve and -ve acknowledgements */
 135     int option;                        /* the option code */
 136     int index;                         /* index into telnet->opt_states[] */
 137     enum {
 138         REQUESTED, ACTIVE, INACTIVE, REALLY_INACTIVE
 139     } initial_state;
 140 };
 141
 142 enum {
 143     OPTINDEX_NAWS,
 144     OPTINDEX_TSPEED,
 145     OPTINDEX_TTYPE,
 146     OPTINDEX_OENV,
 147     OPTINDEX_NENV,
 148     OPTINDEX_ECHO,
 149     OPTINDEX_WE_SGA,
 150     OPTINDEX_THEY_SGA,
 151     OPTINDEX_WE_BIN,
 152     OPTINDEX_THEY_BIN,
 153     NUM_OPTS
 154 };
 155
 156 static const struct Opt o_naws =
 157     { DO, DONT, WILL, WONT, TELOPT_NAWS, OPTINDEX_NAWS, REQUESTED };
 158 static const struct Opt o_ttype =
 159     { DO, DONT, WILL, WONT, TELOPT_TTYPE, OPTINDEX_TTYPE, REQUESTED };
 160 static const struct Opt o_oenv =
 161     { DO, DONT, WILL, WONT, TELOPT_OLD_ENVIRON, OPTINDEX_OENV, INACTIVE };
 162 static const struct Opt o_nenv =
 163     { DO, DONT, WILL, WONT, TELOPT_NEW_ENVIRON, OPTINDEX_NENV, REQUESTED };
 164 static const struct Opt o_echo =
 165     { WILL, WONT, DO, DONT, TELOPT_ECHO, OPTINDEX_ECHO, REQUESTED };
 166 static const struct Opt o_they_sga =
 167     { DO, DONT, WILL, WONT, TELOPT_SGA, OPTINDEX_WE_SGA, REQUESTED };
 168 static const struct Opt o_we_sga =
 169     { WILL, WONT, DO, DONT, TELOPT_SGA, OPTINDEX_THEY_SGA, REQUESTED };
 170
 171 static const struct Opt *const opts[] = {
 172     &o_echo, &o_we_sga, &o_they_sga, &o_naws, &o_ttype, &o_oenv, &o_nenv, NULL
 173 };
 174
 175 struct telnet_tag {
 176     int opt_states[NUM_OPTS];
 177
 178     int sb_opt, sb_len;
 179     unsigned char *sb_buf;
 180     int sb_size;
 181
 182     enum {
 183         TOP_LEVEL, SEENIAC, SEENWILL, SEENWONT, SEENDO, SEENDONT,
 184             SEENSB, SUBNEGOT, SUBNEG_IAC, SEENCR
 185     } state;
 186
 187     sel_wfd *net, *pty;
 188
 189     /*
 190      * Options we must finish processing before launching the shell
 191      */
 192     int old_environ_done, new_environ_done, ttype_done;
 193
 194     /*
 195      * Ready to start shell?
 196      */
 197     int shell_ok;
 198     int envvarsize;
 199     struct shell_data shdata;
 200 };
 201
 202 #define TELNET_MAX_BACKLOG 4096
 203
 204 #define SB_DELTA 1024
 205
 206 static void send_opt(Telnet telnet, int cmd, int option)
 207 {
 208     unsigned char b[3];
 209
 210     b[0] = IAC;
 211     b[1] = cmd;
 212     b[2] = option;
 213     sel_write(telnet->net, (char *)b, 3);
 214 }
 215
 216 static void deactivate_option(Telnet telnet, const struct Opt *o)
 217 {
 218     if (telnet->opt_states[o->index] == REQUESTED ||
 219         telnet->opt_states[o->index] == ACTIVE)
 220         send_opt(telnet, o->nsend, o->option);
 221     telnet->opt_states[o->index] = REALLY_INACTIVE;
 222 }
 223
 224 /*
 225  * Generate side effects of enabling or disabling an option.
 226  */
 227 static void option_side_effects(Telnet telnet, const struct Opt *o, int enabled)
 228 {
 229 }
 230
 231 static void activate_option(Telnet telnet, const struct Opt *o)
 232 {
 233     if (o->option == TELOPT_NEW_ENVIRON ||
 234         o->option == TELOPT_OLD_ENVIRON ||
 235         o->option == TELOPT_TTYPE) {
 236         char buf[6];
 237         buf[0] = IAC;
 238         buf[1] = SB;
 239         buf[2] = o->option;
 240         buf[3] = TELQUAL_SEND;
 241         buf[4] = IAC;
 242         buf[5] = SE;
 243         sel_write(telnet->net, buf, 6);
 244     }
 245     option_side_effects(telnet, o, 1);
 246 }
 247
 248 static void done_option(Telnet telnet, int option)
 249 {
 250     if (option == TELOPT_OLD_ENVIRON)
 251         telnet->old_environ_done = 1;
 252     else if (option == TELOPT_NEW_ENVIRON)
 253         telnet->new_environ_done = 1;
 254     else if (option == TELOPT_TTYPE)
 255         telnet->ttype_done = 1;
 256
 257     if (telnet->old_environ_done && telnet->new_environ_done &&
 258         telnet->ttype_done) {
 259         telnet->shell_ok = 1;
 260     }
 261 }
 262
 263 static void refused_option(Telnet telnet, const struct Opt *o)
 264 {
 265     done_option(telnet, o->option);
 266     if (o->send == WILL && o->option == TELOPT_NEW_ENVIRON &&
 267         telnet->opt_states[o_oenv.index] == INACTIVE) {
 268         send_opt(telnet, WILL, TELOPT_OLD_ENVIRON);
 269         telnet->opt_states[o_oenv.index] = REQUESTED;
 270         telnet->old_environ_done = 0;
 271     }
 272     option_side_effects(telnet, o, 0);
 273 }
 274
 275 static void proc_rec_opt(Telnet telnet, int cmd, int option)
 276 {
 277     const struct Opt *const *o;
 278
 279     for (o = opts; *o; o++) {
 280         if ((*o)->option == option && (*o)->ack == cmd) {
 281             switch (telnet->opt_states[(*o)->index]) {
 282               case REQUESTED:
 283                 telnet->opt_states[(*o)->index] = ACTIVE;
 284                 activate_option(telnet, *o);
 285                 break;
 286               case ACTIVE:
 287                 break;
 288               case INACTIVE:
 289                 telnet->opt_states[(*o)->index] = ACTIVE;
 290                 send_opt(telnet, (*o)->send, option);
 291                 activate_option(telnet, *o);
 292                 break;
 293               case REALLY_INACTIVE:
 294                 send_opt(telnet, (*o)->nsend, option);
 295                 break;
 296             }
 297             return;
 298         } else if ((*o)->option == option && (*o)->nak == cmd) {
 299             switch (telnet->opt_states[(*o)->index]) {
 300               case REQUESTED:
 301                 telnet->opt_states[(*o)->index] = INACTIVE;
 302                 refused_option(telnet, *o);
 303                 break;
 304               case ACTIVE:
 305                 telnet->opt_states[(*o)->index] = INACTIVE;
 306                 send_opt(telnet, (*o)->nsend, option);
 307                 option_side_effects(telnet, *o, 0);
 308                 break;
 309               case INACTIVE:
 310               case REALLY_INACTIVE:
 311                 break;
 312             }
 313             return;
 314         }
 315     }
 316     /*
 317      * If we reach here, the option was one we weren't prepared to
 318      * cope with. If the request was positive (WILL or DO), we send
 319      * a negative ack to indicate refusal. If the request was
 320      * negative (WONT / DONT), we must do nothing.
 321      */
 322     if (cmd == WILL || cmd == DO)
 323         send_opt(telnet, (cmd == WILL ? DONT : WONT), option);
 324 }
 325
 326 static void process_subneg(Telnet telnet)
 327 {
 328     unsigned char b[2048], *p, *q;
 329     int var, value, n;
 330     char *e;
 331
 332     switch (telnet->sb_opt) {
 333       case TELOPT_OLD_ENVIRON:
 334       case TELOPT_NEW_ENVIRON:
 335         if (telnet->sb_buf[0] == TELQUAL_IS) {
 336             if (telnet->sb_opt == TELOPT_NEW_ENVIRON) {
 337                 var = RFC_VAR;
 338                 value = RFC_VALUE;
 339             } else {
 340                 if (telnet->sb_len > 1 && !(telnet->sb_buf[0] &~ 1)) {
 341                     var = telnet->sb_buf[0];
 342                     value = BSD_VAR ^ BSD_VALUE ^ var;
 343                 } else {
 344                     var = BSD_VAR;
 345                     value = BSD_VALUE;
 346                 }
 347             }
 348         }
 349         n = 1;
 350         while (n < telnet->sb_len && telnet->sb_buf[n] == var) {
 351             int varpos, varlen, valpos, vallen;
 352             char *result;
 353
 354             varpos = ++n;
 355             while (n < telnet->sb_len && telnet->sb_buf[n] != value)
 356                 n++;
 357             if (n == telnet->sb_len)
 358                 break;
 359             varlen = n - varpos;
 360             valpos = ++n;
 361             while (n < telnet->sb_len && telnet->sb_buf[n] != var)
 362                 n++;
 363             vallen = n - valpos;
 364
 365             result = snewn(varlen + vallen + 2, char);
 366             sprintf(result, "%.*s=%.*s",
 367                     varlen, telnet->sb_buf+varpos,
 368                     vallen, telnet->sb_buf+valpos);
 369             if (telnet->shdata.nenvvars >= telnet->envvarsize) {
 370                 telnet->envvarsize = telnet->shdata.nenvvars * 3 / 2 + 16;
 371                 telnet->shdata.envvars = sresize(telnet->shdata.envvars,
 372                                                  telnet->envvarsize, char *);
 373             }
 374             telnet->shdata.envvars[telnet->shdata.nenvvars++] = result;
 375         }
 376         done_option(telnet, telnet->sb_opt);
 377         break;
 378       case TELOPT_TTYPE:
 379         if (telnet->sb_len >= 1 && telnet->sb_buf[0] == TELQUAL_IS) {
 380             telnet->shdata.termtype = snewn(5 + telnet->sb_len, char);
 381             strcpy(telnet->shdata.termtype, "TERM=");
 382             for (n = 0; n < telnet->sb_len-1; n++) {
 383                 char c = telnet->sb_buf[n+1];
 384                 if (c >= 'A' && c <= 'Z')
 385                     c = c + 'a' - 'A';
 386                 telnet->shdata.termtype[n+5] = c;
 387             }
 388             telnet->shdata.termtype[telnet->sb_len+5-1] = '\0';
 389         }
 390         done_option(telnet, telnet->sb_opt);
 391         break;
 392       case TELOPT_NAWS:
 393         if (telnet->sb_len == 4) {
 394             int w, h;
 395             w = (unsigned char)telnet->sb_buf[0];
 396             w = (w << 8) | (unsigned char)telnet->sb_buf[1];
 397             h = (unsigned char)telnet->sb_buf[2];
 398             h = (h << 8) | (unsigned char)telnet->sb_buf[3];
 399             pty_resize(w, h);
 400         }
 401         break;
 402     }
 403 }
 404
 405 void telnet_from_net(Telnet telnet, char *buf, int len)
 406 {
 407     while (len--) {
 408         int c = (unsigned char) *buf++;
 409
 410         switch (telnet->state) {
 411           case TOP_LEVEL:
 412           case SEENCR:
 413             /*
 414              * PuTTY sends Telnet's new line sequence (CR LF on
 415              * the wire) in response to the return key. We must
 416              * therefore treat that as equivalent to CR NUL, and
 417              * send CR to the pty.
 418              */
 419             if ((c == NUL || c == '\n') && telnet->state == SEENCR)
 420                 telnet->state = TOP_LEVEL;
 421             else if (c == IAC)
 422                 telnet->state = SEENIAC;
 423             else {
 424                 char cc = c;
 425                 sel_write(telnet->pty, &cc, 1);
 426
 427                 telnet->state = SEENCR;
 428             }
 429             break;
 430           case SEENIAC:
 431             if (c == DO)
 432                 telnet->state = SEENDO;
 433             else if (c == DONT)
 434                 telnet->state = SEENDONT;
 435             else if (c == WILL)
 436                 telnet->state = SEENWILL;
 437             else if (c == WONT)
 438                 telnet->state = SEENWONT;
 439             else if (c == SB)
 440                 telnet->state = SEENSB;
 441             else if (c == DM)
 442                 telnet->state = TOP_LEVEL;
 443             else {
 444                 /* ignore everything else; print it if it's IAC */
 445                 if (c == IAC) {
 446                     char cc = c;
 447                     sel_write(telnet->pty, &cc, 1);
 448                 }
 449                 telnet->state = TOP_LEVEL;
 450             }
 451             break;
 452           case SEENWILL:
 453             proc_rec_opt(telnet, WILL, c);
 454             telnet->state = TOP_LEVEL;
 455             break;
 456           case SEENWONT:
 457             proc_rec_opt(telnet, WONT, c);
 458             telnet->state = TOP_LEVEL;
 459             break;
 460           case SEENDO:
 461             proc_rec_opt(telnet, DO, c);
 462             telnet->state = TOP_LEVEL;
 463             break;
 464           case SEENDONT:
 465             proc_rec_opt(telnet, DONT, c);
 466             telnet->state = TOP_LEVEL;
 467             break;
 468           case SEENSB:
 469             telnet->sb_opt = c;
 470             telnet->sb_len = 0;
 471             telnet->state = SUBNEGOT;
 472             break;
 473           case SUBNEGOT:
 474             if (c == IAC)
 475                 telnet->state = SUBNEG_IAC;
 476             else {
 477               subneg_addchar:
 478                 if (telnet->sb_len >= telnet->sb_size) {
 479                     telnet->sb_size += SB_DELTA;
 480                     telnet->sb_buf = sresize(telnet->sb_buf, telnet->sb_size,
 481                                              unsigned char);
 482                 }
 483                 telnet->sb_buf[telnet->sb_len++] = c;
 484                 telnet->state = SUBNEGOT;       /* in case we came here by goto */
 485             }
 486             break;
 487           case SUBNEG_IAC:
 488             if (c != SE)
 489                 goto subneg_addchar;   /* yes, it's a hack, I know, but... */
 490             else {
 491                 process_subneg(telnet);
 492                 telnet->state = TOP_LEVEL;
 493             }
 494             break;
 495         }
 496     }
 497 }
 498
 499 Telnet telnet_new(sel_wfd *net, sel_wfd *pty)
 500 {
 501     Telnet telnet;
 502
 503     telnet = snew(struct telnet_tag);
 504     telnet->sb_buf = NULL;
 505     telnet->sb_size = 0;
 506     telnet->state = TOP_LEVEL;
 507     telnet->net = net;
 508     telnet->pty = pty;
 509     telnet->shdata.envvars = NULL;
 510     telnet->shdata.nenvvars = telnet->envvarsize = 0;
 511     telnet->shdata.termtype = NULL;
 512
 513     /*
 514      * Initialise option states.
 515      */
 516     {
 517         const struct Opt *const *o;
 518
 519         for (o = opts; *o; o++) {
 520             telnet->opt_states[(*o)->index] = (*o)->initial_state;
 521             if (telnet->opt_states[(*o)->index] == REQUESTED)
 522                 send_opt(telnet, (*o)->send, (*o)->option);
 523         }
 524     }
 525
 526     telnet->old_environ_done = 1;      /* initially don't want to bother */
 527     telnet->new_environ_done = 0;
 528     telnet->ttype_done = 0;
 529     telnet->shell_ok = 0;
 530
 531     return telnet;
 532 }
 533
 534 void telnet_free(Telnet telnet)
 535 {
 536     sfree(telnet->sb_buf);
 537     sfree(telnet);
 538 }
 539
 540 void telnet_from_pty(Telnet telnet, char *buf, int len)
 541 {
 542     unsigned char *p, *end;
 543     static const unsigned char iac[2] = { IAC, IAC };
 544     static const unsigned char cr[2] = { CR, NUL };
 545 #if 0
 546     static const unsigned char nl[2] = { CR, LF };
 547 #endif
 548
 549     p = (unsigned char *)buf;
 550     end = (unsigned char *)(buf + len);
 551     while (p < end) {
 552         unsigned char *q = p;
 553
 554         while (p < end && iswritable(*p))
 555             p++;
 556         sel_write(telnet->net, (char *)q, p - q);
 557
 558         while (p < end && !iswritable(*p)) {
 559             sel_write(telnet->net, (char *)(*p == IAC ? iac : cr), 2);
 560             p++;
 561         }
 562     }
 563 }
 564
 565 int telnet_shell_ok(Telnet telnet, struct shell_data *shdata)
 566 {
 567     if (telnet->shell_ok)
 568         *shdata = telnet->shdata;      /* structure copy */
 569     return telnet->shell_ok;
 570 }