153 lines
3.9 KiB
C
153 lines
3.9 KiB
C
/*
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* Handling details related to telnet protocol.
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*/
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#include "moxerver.h"
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/* structure for holding telnet option name and value */
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struct telnet_option_t {
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const char *name;
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char value;
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};
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/* supported telnet option values */
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struct telnet_option_t telnet_options[] = {
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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 telnet option name based on the value. */
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static const char* telnet_option_name(int value) {
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int i = 0;
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while (telnet_options[i].name) {
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if (telnet_options[i].value == value) return telnet_options[i].name;
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i++;
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}
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return '\0';
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}
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/* Returns telnet option value based on the name. */
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static char telnet_option_value(const char* name) {
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int i = 0;
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while (telnet_options[i].name) {
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if (!strcmp(telnet_options[i].name, name)) return telnet_options[i].value;
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i++;
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}
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return 0;
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}
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/* Sends telnet option command. Returns 0 on success, -1 on failure. */
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static int telnet_send_command(struct client_t *client, const char* option, const char* command) {
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char data[3];
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/* pack command */
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data[0] = telnet_option_value("IAC");
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data[1] = telnet_option_value(option);
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data[2] = telnet_option_value(command);
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/* send command */
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if (client_write(client, data, 3) <= 0) {
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fprintf(stderr, "[%s:%d] failed sending %s %s\n", __func__, __LINE__, option, command);
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return -1;
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}
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fprintf(stderr, "[%s] sent %s %s\n", __func__, option, command);
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return 0;
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}
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/* Handles received telnet option command. Always returns 0.*/
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static int telnet_handle_command(char *databuf, int datalen) {
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/* currently just print received commands because 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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fprintf(stderr, "[%s] received %s %s\n", __func__,
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telnet_option_name(databuf[1]), telnet_option_name(databuf[2]));
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}
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return 0;
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}
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/* Tells client to go into "character" mode. */
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int telnet_set_character_mode(struct client_t *client) {
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int err = 0;
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/* send predefined commands and add up their return vaules */
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err += telnet_send_command(client, "WILL", "ECHO");
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err += telnet_send_command(client, "WILL", "SGA");
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err += telnet_send_command(client, "WONT", "LINEMODE"); /* this depends on telnet client */
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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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return err;
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}
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/* Handles special characters in data buffer after receiving them from client.
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* Used to filter out handshake commands of telnet protocol. */
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int telnet_handle_client_read(char *databuf, int *datalen) {
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int i;
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char newdata[DATABUF_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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/* handle and discard telnet commands */
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if (databuf[i] == telnet_option_value("IAC")) {
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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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newdata[newlen++] = databuf[i];
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}
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}
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/* overwrite data with new buffer */
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for (i = 0; i < newlen; i++) databuf[i] = newdata[i];
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*datalen = newlen;
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return 0;
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}
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/* Handles special characters in data buffer before sending to client.
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* Used for echoing characters correctly to telnet client. */
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int telnet_handle_client_write(char *databuf, int *datalen) {
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int i;
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char newdata[DATABUF_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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/* pressed ENTER */
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if (databuf[i] == 13) {
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fprintf(stderr, "[%s] handling ENTER\n", __func__);
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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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fprintf(stderr, "[%s] handling BACKSPACE\n", __func__);
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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 data with new buffer */
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for (i = 0; i < newlen; i++) databuf[i] = newdata[i];
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*datalen = newlen;
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return 0;
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}
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