153 lines
3.3 KiB
C
153 lines
3.3 KiB
C
#include <telnet.h>
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/* structure for holding telnet option name and value */
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typedef struct
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{
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const char *name;
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char value;
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} telnet_option_t;
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/* supported telnet option values */
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telnet_option_t telnet_options[] =
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{
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{"WILL", 251},
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{"WONT", 252},
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{"DO", 253},
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{"DONT", 254},
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{"IAC", 255},
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{"ECHO", 1},
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{"SGA", 3},
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{"LINEMODE", 34},
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{NULL, 0}
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/* this list must end with {NULL, 0} */
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};
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/* Returns the name of a telnet option based on the value. */
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static const char* telnet_option_name(int value)
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{
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int i;
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for (i = 0; telnet_options[i].name != NULL; i++)
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{
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if (telnet_options[i].value == value)
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{
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return telnet_options[i].name;
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}
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}
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/* default value */
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return '\0';
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}
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/* Returns the value of a telnet option based on the name. */
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static char telnet_option_value(const char* name)
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{
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int i;
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for (i = 0; telnet_options[i].name != NULL; i++)
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{
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if (strcmp(telnet_options[i].name, name) == 0)
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{
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return telnet_options[i].value;
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}
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}
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/* default value */
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return 0;
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}
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/* Handles a received telnet option command. */
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static void telnet_handle_command(char *databuf, int datalen)
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{
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/* just print received commands:
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* we set the client, we don't adapt to client commands */
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if (databuf[0] == telnet_option_value("IAC"))
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{
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LOG("received %s %s",
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telnet_option_name(databuf[1]),
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telnet_option_name(databuf[2]));
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}
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}
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void telnet_message_set_character_mode(char *databuf)
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{
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/* send a predefined set of commands proven to work */
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databuf[0] = telnet_option_value("IAC");
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databuf[1] = telnet_option_value("WILL");
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databuf[2] = telnet_option_value("ECHO");
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databuf[3] = telnet_option_value("IAC");
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databuf[4] = telnet_option_value("WILL");
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databuf[5] = telnet_option_value("SGA");
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/* this one really depends on telnet client */
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databuf[6] = telnet_option_value("IAC");
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databuf[7] = telnet_option_value("WONT");
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databuf[8] = telnet_option_value("LINEMODE");
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//TODO Do we verify client response? What do we do if the response is not how we expected?
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}
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void telnet_filter_client_read(char *databuf, int *datalen)
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{
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int i;
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char newdata[BUFFER_LEN];
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int newlen = 0;
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/* process data using a new buffer */
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for (i = 0; i < *datalen; i++)
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{
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/* handle and discard telnet commands */
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if (databuf[i] == telnet_option_value("IAC"))
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{
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telnet_handle_command((databuf+i), 3);
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i += 2;
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}
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/* let other data pass through */
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else
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{
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newdata[newlen++] = databuf[i];
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}
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}
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/* overwrite the data with the new buffer */
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for (i = 0; i < newlen; i++)
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{
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databuf[i] = newdata[i];
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}
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/* update data length */
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*datalen = newlen;
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}
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void telnet_filter_client_write(char *databuf, int *datalen)
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{
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int i;
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char newdata[BUFFER_LEN]; // TODO: maybe use realloc, this is risky
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int newlen = 0;
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/* process data using a new buffer */
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for (i = 0; i < *datalen; i++)
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{
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/* pressed ENTER */
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if (databuf[i] == 13)
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{
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LOG("handling ENTER");
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newdata[newlen++] = '\r';
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newdata[newlen++] = '\n';
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}
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/* pressed BACKSPACE */
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if (databuf[i] == 127)
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{
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LOG("handling BACKSPACE");
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newdata[newlen++] = 8;
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newdata[newlen++] = ' ';
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newdata[newlen++] = 8;
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}
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else {
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newdata[newlen++] = databuf[i];
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}
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}
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/* overwrite the data with the new buffer */
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for (i = 0; i < newlen; i++)
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{
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databuf[i] = newdata[i];
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}
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/* update data length */
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*datalen = newlen;
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}
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