1 /* telnet.c - Telnet client.
2 *
3 * Copyright 2012 Madhur Verma <mad.flexi@gmail.com>
4 * Copyright 2013 Kyungwan Han <asura321@gmail.com>
5 * Modified by Ashwini Kumar <ak.ashwini1981@gmail.com>
6 *
7 * Not in SUSv4.
8
9 USE_TELNET(NEWTOY(telnet, "<1>2", TOYFLAG_BIN))
10
11 config TELNET
12 bool "telnet"
13 default n
14 help
15 usage: telnet HOST [PORT]
16
17 Connect to telnet server
18 */
19
20 #define FOR_telnet
21 #include "toys.h"
22 #include <arpa/telnet.h>
23 #include <netinet/in.h>
24 #include <sys/poll.h>
25
26 GLOBALS(
27 int port;
28 int sfd;
29 char buff[128];
30 int pbuff;
31 char iac[256];
32 int piac;
33 char *ttype;
34 struct termios def_term;
35 struct termios raw_term;
36 uint8_t term_ok;
37 uint8_t term_mode;
38 uint8_t flags;
39 unsigned win_width;
40 unsigned win_height;
41 )
42
43 #define DATABUFSIZE 128
44 #define IACBUFSIZE 256
45 #define CM_TRY 0
46 #define CM_ON 1
47 #define CM_OFF 2
48 #define UF_ECHO 0x01
49 #define UF_SGA 0x02
50
51 // sets terminal mode: LINE or CHARACTER based om internal stat.
52 static char const es[] = "\r\nEscape character is ";
set_mode(void)53 static void set_mode(void)
54 {
55 if (TT.flags & UF_ECHO) {
56 if (TT.term_mode == CM_TRY) {
57 TT.term_mode = CM_ON;
58 printf("\r\nEntering character mode%s'^]'.\r\n", es);
59 if (TT.term_ok) tcsetattr(0, TCSADRAIN, &TT.raw_term);
60 }
61 } else {
62 if (TT.term_mode != CM_OFF) {
63 TT.term_mode = CM_OFF;
64 printf("\r\nEntering line mode%s'^C'.\r\n", es);
65 if (TT.term_ok) tcsetattr(0, TCSADRAIN, &TT.def_term);
66 }
67 }
68 }
69
70 // flushes all data in IAC buff to server.
flush_iac(void)71 static void flush_iac(void)
72 {
73 int wlen = write(TT.sfd, TT.iac, TT.piac);
74
75 if(wlen <= 0) error_msg("IAC : send failed.");
76 TT.piac = 0;
77 }
78
79 // puts DATA in iac buff of length LEN and updates iac buff pointer.
put_iac(int len,...)80 static void put_iac(int len, ...)
81 {
82 va_list va;
83
84 if(TT.piac + len >= IACBUFSIZE) flush_iac();
85 va_start(va, len);
86 for(;len > 0; TT.iac[TT.piac++] = (uint8_t)va_arg(va, int), len--);
87 va_end(va);
88 }
89
90 // puts string STR in iac buff and updates iac buff pointer.
str_iac(char * str)91 static void str_iac(char *str)
92 {
93 int len = strlen(str);
94
95 if(TT.piac + len + 1 >= IACBUFSIZE) flush_iac();
96 strcpy(&TT.iac[TT.piac], str);
97 TT.piac += len+1;
98 }
99
handle_esc(void)100 static void handle_esc(void)
101 {
102 char input;
103
104 if(toys.signal && TT.term_ok) tcsetattr(0, TCSADRAIN, &TT.raw_term);
105 xwrite(1,"\r\nConsole escape. Commands are:\r\n\n"
106 " l go to line mode\r\n"
107 " c go to character mode\r\n"
108 " z suspend telnet\r\n"
109 " e exit telnet\r\n", 114);
110
111 if (read(STDIN_FILENO, &input, 1) <= 0) {
112 if(TT.term_ok) tcsetattr(0, TCSADRAIN, &TT.def_term);
113 exit(0);
114 }
115
116 switch (input) {
117 case 'l':
118 if (!toys.signal) {
119 TT.term_mode = CM_TRY;
120 TT.flags &= ~(UF_ECHO | UF_SGA);
121 set_mode();
122 put_iac(6, IAC,DONT,TELOPT_ECHO,IAC,DONT, TELOPT_SGA);
123 flush_iac();
124 goto ret;
125 }
126 break;
127 case 'c':
128 if (toys.signal) {
129 TT.term_mode = CM_TRY;
130 TT.flags |= (UF_ECHO | UF_SGA);
131 set_mode();
132 put_iac(6, IAC,DO,TELOPT_ECHO,IAC,DO,TELOPT_SGA);
133 flush_iac();
134 goto ret;
135 }
136 break;
137 case 'z':
138 if(TT.term_ok) tcsetattr(0, TCSADRAIN, &TT.def_term);
139 kill(0, SIGTSTP);
140 if(TT.term_ok) tcsetattr(0, TCSADRAIN, &TT.raw_term);
141 break;
142 case 'e':
143 if(TT.term_ok) tcsetattr(0, TCSADRAIN, &TT.def_term);
144 exit(0);
145 default: break;
146 }
147
148 xwrite(1, "continuing...\r\n", 15);
149 if (toys.signal && TT.term_ok) tcsetattr(0, TCSADRAIN, &TT.def_term);
150
151 ret:
152 toys.signal = 0;
153 }
154
155 /*
156 * handles telnet SUB NEGOTIATIONS
157 * only terminal type is supported.
158 */
handle_negotiations(void)159 static void handle_negotiations(void)
160 {
161 char opt = TT.buff[TT.pbuff++];
162
163 switch(opt) {
164 case TELOPT_TTYPE:
165 opt = TT.buff[TT.pbuff++];
166 if(opt == TELQUAL_SEND) {
167 put_iac(4, IAC,SB,TELOPT_TTYPE,TELQUAL_IS);
168 str_iac(TT.ttype);
169 put_iac(2, IAC,SE);
170 }
171 break;
172 default: break;
173 }
174 }
175
176 /*
177 * handles server's DO DONT WILL WONT requests.
178 * supports ECHO, SGA, TTYPE, NAWS
179 */
handle_ddww(char ddww)180 static void handle_ddww(char ddww)
181 {
182 char opt = TT.buff[TT.pbuff++];
183
184 switch (opt) {
185 case TELOPT_ECHO: /* ECHO */
186 if (ddww == DO) put_iac(3, IAC,WONT,TELOPT_ECHO);
187 if(ddww == DONT) break;
188 if (TT.flags & UF_ECHO) {
189 if (ddww == WILL) return;
190 } else if (ddww == WONT) return;
191 if (TT.term_mode != CM_OFF) TT.flags ^= UF_ECHO;
192 (TT.flags & UF_ECHO)? put_iac(3, IAC,DO,TELOPT_ECHO) :
193 put_iac(3, IAC,DONT,TELOPT_ECHO);
194 set_mode();
195 printf("\r\n");
196 break;
197
198 case TELOPT_SGA: /* Supress GO Ahead */
199 if (TT.flags & UF_SGA){ if (ddww == WILL) return;
200 } else if (ddww == WONT) return;
201
202 TT.flags ^= UF_SGA;
203 (TT.flags & UF_SGA)? put_iac(3, IAC,DO,TELOPT_SGA) :
204 put_iac(3, IAC,DONT,TELOPT_SGA);
205 break;
206
207 case TELOPT_TTYPE: /* Terminal Type */
208 (TT.ttype)? put_iac(3, IAC,WILL,TELOPT_TTYPE):
209 put_iac(3, IAC,WONT,TELOPT_TTYPE);
210 break;
211
212 case TELOPT_NAWS: /* Window Size */
213 put_iac(3, IAC,WILL,TELOPT_NAWS);
214 put_iac(9, IAC,SB,TELOPT_NAWS,(TT.win_width >> 8) & 0xff,
215 TT.win_width & 0xff,(TT.win_height >> 8) & 0xff,
216 TT.win_height & 0xff,IAC,SE);
217 break;
218
219 default: /* Default behaviour is to say NO */
220 if(ddww == WILL) put_iac(3, IAC,DONT,opt);
221 if(ddww == DO) put_iac(3, IAC,WONT,opt);
222 break;
223 }
224 }
225
226 /*
227 * parses data which is read from server of length LEN.
228 * and passes it to console.
229 */
read_server(int len)230 static int read_server(int len)
231 {
232 int i = 0;
233 char curr;
234 TT.pbuff = 0;
235
236 do {
237 curr = TT.buff[TT.pbuff++];
238 if (curr == IAC) {
239 curr = TT.buff[TT.pbuff++];
240 switch (curr) {
241 case DO: /* FALLTHROUGH */
242 case DONT: /* FALLTHROUGH */
243 case WILL: /* FALLTHROUGH */
244 case WONT:
245 handle_ddww(curr);
246 break;
247 case SB:
248 handle_negotiations();
249 break;
250 case SE:
251 break;
252 default: break;
253 }
254 } else {
255 toybuf[i++] = curr;
256 if (curr == '\r') { curr = TT.buff[TT.pbuff++];
257 if (curr != '\0') TT.pbuff--;
258 }
259 }
260 } while (TT.pbuff < len);
261
262 if (i) xwrite(STDIN_FILENO, toybuf, i);
263 return 0;
264 }
265
266 /*
267 * parses data which is read from console of length LEN
268 * and passes it to server.
269 */
write_server(int len)270 static void write_server(int len)
271 {
272 char *c = (char*)TT.buff;
273 int i = 0;
274
275 for (; len > 0; len--, c++) {
276 if (*c == 0x1d) {
277 handle_esc();
278 return;
279 }
280 toybuf[i++] = *c;
281 if (*c == IAC) toybuf[i++] = *c; /* IAC -> IAC IAC */
282 else if (*c == '\r') toybuf[i++] = '\0'; /* CR -> CR NUL */
283 }
284 if(i) xwrite(TT.sfd, toybuf, i);
285 }
286
telnet_main(void)287 void telnet_main(void)
288 {
289 char *port = "23";
290 int set = 1, len;
291 struct pollfd pfds[2];
292
293 TT.win_width = 80; //columns
294 TT.win_height = 24; //rows
295
296 if (toys.optc == 2) port = toys.optargs[1];
297
298 TT.ttype = getenv("TERM");
299 if(!TT.ttype) TT.ttype = "";
300 if(strlen(TT.ttype) > IACBUFSIZE-1) TT.ttype[IACBUFSIZE - 1] = '\0';
301
302 if (!tcgetattr(0, &TT.def_term)) {
303 TT.term_ok = 1;
304 TT.raw_term = TT.def_term;
305 cfmakeraw(&TT.raw_term);
306 }
307 terminal_size(&TT.win_width, &TT.win_height);
308
309 TT.sfd = xconnect(*toys.optargs, port, 0, SOCK_STREAM, IPPROTO_TCP, 0);
310 setsockopt(TT.sfd, SOL_SOCKET, SO_REUSEADDR, &set, sizeof(set));
311 setsockopt(TT.sfd, SOL_SOCKET, SO_KEEPALIVE, &set, sizeof(set));
312
313 pfds[0].fd = STDIN_FILENO;
314 pfds[0].events = POLLIN;
315 pfds[1].fd = TT.sfd;
316 pfds[1].events = POLLIN;
317
318 signal(SIGINT, generic_signal);
319 while(1) {
320 if(TT.piac) flush_iac();
321 if(poll(pfds, 2, -1) < 0) {
322 if (toys.signal) handle_esc();
323 else sleep(1);
324
325 continue;
326 }
327 if(pfds[0].revents) {
328 len = read(STDIN_FILENO, TT.buff, DATABUFSIZE);
329 if(len > 0) write_server(len);
330 else return;
331 }
332 if(pfds[1].revents) {
333 len = read(TT.sfd, TT.buff, DATABUFSIZE);
334 if(len > 0) read_server(len);
335 else {
336 printf("Connection closed by foreign host\r\n");
337 if(TT.term_ok) tcsetattr(0, TCSADRAIN, &TT.def_term);
338 exit(1);
339 }
340 }
341 }
342 }
343