| #include <sys/socket.h> |
| #include <netinet/in.h> |
| #include <arpa/inet.h> |
| #include <poll.h> |
| #include <errno.h> |
| #include <stdio.h> |
| #include <string.h> |
| #include <stdlib.h> |
| #include <ctype.h> |
| #include <unistd.h> |
| |
| #include "libtelnet.h" |
| |
| struct conn_t { |
| const char *name; |
| int sock; |
| struct libtelnet_t telnet; |
| struct conn_t *remote; |
| }; |
| |
| static const char *get_cmd(unsigned char cmd) { |
| static char buffer[4]; |
| |
| switch (cmd) { |
| case 255: return "IAC"; |
| case 254: return "DONT"; |
| case 253: return "DO"; |
| case 252: return "WONT"; |
| case 251: return "WILL"; |
| case 250: return "SB"; |
| case 249: return "GA"; |
| case 248: return "EL"; |
| case 247: return "EC"; |
| case 246: return "AYT"; |
| case 245: return "AO"; |
| case 244: return "IP"; |
| case 243: return "BREAK"; |
| case 242: return "DM"; |
| case 241: return "NOP"; |
| case 240: return "SE"; |
| case 239: return "EOR"; |
| case 238: return "ABORT"; |
| case 237: return "SUSP"; |
| case 236: return "xEOF"; |
| default: |
| snprintf(buffer, sizeof(buffer), "%d", (int)cmd); |
| return buffer; |
| } |
| } |
| |
| static const char *get_opt(unsigned char opt) { |
| switch (opt) { |
| case 0: return "BINARY"; |
| case 1: return "ECHO"; |
| case 2: return "RCP"; |
| case 3: return "SGA"; |
| case 4: return "NAMS"; |
| case 5: return "STATUS"; |
| case 6: return "TM"; |
| case 7: return "RCTE"; |
| case 8: return "NAOL"; |
| case 9: return "NAOP"; |
| case 10: return "NAOCRD"; |
| case 11: return "NAOHTS"; |
| case 12: return "NAOHTD"; |
| case 13: return "NAOFFD"; |
| case 14: return "NAOVTS"; |
| case 15: return "NAOVTD"; |
| case 16: return "NAOLFD"; |
| case 17: return "XASCII"; |
| case 18: return "LOGOUT"; |
| case 19: return "BM"; |
| case 20: return "DET"; |
| case 21: return "SUPDUP"; |
| case 22: return "SUPDUPOUTPUT"; |
| case 23: return "SNDLOC"; |
| case 24: return "TTYPE"; |
| case 25: return "EOR"; |
| case 26: return "TUID"; |
| case 27: return "OUTMRK"; |
| case 28: return "TTYLOC"; |
| case 29: return "3270REGIME"; |
| case 30: return "X3PAD"; |
| case 31: return "NAWS"; |
| case 32: return "TSPEED"; |
| case 33: return "LFLOW"; |
| case 34: return "LINEMODE"; |
| case 35: return "XDISPLOC"; |
| case 36: return "ENVIRON"; |
| case 37: return "AUTHENTICATION"; |
| case 38: return "ENCRYPT"; |
| case 39: return "NEW-ENVIRON"; |
| case 70: return "MSSP"; |
| case 85: return "COMPRESS"; |
| case 86: return "COMPRESS2"; |
| case 93: return "ZMP"; |
| case 255: return "EXOPL"; |
| default: return "unknown"; |
| } |
| } |
| |
| static void print_buffer(unsigned char *buffer, unsigned int size) { |
| unsigned int i; |
| for (i = 0; i != size; ++i) { |
| if (buffer[i] == ' ' || (isprint(buffer[i]) && !isspace(buffer[i]))) |
| printf("%c", (char)buffer[i]); |
| else if (buffer[i] == '\n') |
| printf("<%02X>\n", (int)buffer[i]); |
| else |
| printf("<%02X>", (int)buffer[i]); |
| } |
| } |
| |
| void libtelnet_data_cb(struct libtelnet_t *telnet, unsigned char *buffer, |
| unsigned int size, void *user_data) { |
| struct conn_t *conn = (struct conn_t*)user_data; |
| |
| printf("%s DATA: ", conn->name); |
| print_buffer(buffer, size); |
| printf("\e[0m\n"); |
| |
| libtelnet_send_data(&conn->remote->telnet, buffer, size, |
| conn->remote); |
| } |
| |
| void libtelnet_send_cb(struct libtelnet_t *telnet, unsigned char *buffer, |
| unsigned int size, void *user_data) { |
| struct conn_t *conn = (struct conn_t*)user_data; |
| |
| /* DONT SPAM |
| printf("%s SEND: ", conn->name); |
| print_buffer(buffer, size); |
| printf("\e[0m\n"); |
| */ |
| |
| /* send data */ |
| send(conn->sock, buffer, size, 0); |
| } |
| |
| void libtelnet_command_cb(struct libtelnet_t *telnet, unsigned char cmd, |
| void *user_data) { |
| struct conn_t *conn = (struct conn_t*)user_data; |
| |
| printf("%s IAC %s\e[0m\n", conn->name, get_cmd(cmd)); |
| |
| libtelnet_send_command(&conn->remote->telnet, cmd, conn->remote); |
| } |
| |
| void libtelnet_negotiate_cb(struct libtelnet_t *telnet, unsigned char cmd, |
| unsigned char opt, void *user_data) { |
| struct conn_t *conn = (struct conn_t*)user_data; |
| |
| printf("%s IAC %s %d (%s)\e[0m\n", conn->name, get_cmd(cmd), |
| (int)opt, get_opt(opt)); |
| |
| libtelnet_send_negotiate(&conn->remote->telnet, cmd, opt, |
| conn->remote); |
| } |
| |
| void libtelnet_subrequest_cb(struct libtelnet_t *telnet, unsigned char type, |
| unsigned char *buffer, unsigned int size, void *user_data) { |
| struct conn_t *conn = (struct conn_t*)user_data; |
| |
| printf("%s SUB %d (%s)", conn->name, (int)type, get_opt(type)); |
| if (size > 0) { |
| printf(": "); |
| print_buffer(buffer, size); |
| } |
| printf("\e[0m\n"); |
| |
| libtelnet_send_subrequest(&conn->remote->telnet, type, buffer, size, |
| conn->remote); |
| } |
| |
| void libtelnet_error_cb(struct libtelnet_t *telnet, |
| enum libtelnet_error_t error, void *user_data) { |
| struct conn_t *conn = (struct conn_t*)user_data; |
| |
| printf("%s ERROR: %d\e[0m\n", conn->name, (int)error); |
| } |
| |
| int main(int argc, char **argv) { |
| unsigned char buffer[512]; |
| int listen_sock; |
| int rs; |
| struct sockaddr_in addr; |
| socklen_t addrlen; |
| struct pollfd pfd[2]; |
| struct conn_t server; |
| struct conn_t client; |
| |
| /* check usage */ |
| if (argc != 4) { |
| fprintf(stderr, "Usage:\n ./telnet-proxy <remote ip> <remote port> " |
| "<local port>\n"); |
| return 1; |
| } |
| |
| /* create listening socket */ |
| if ((listen_sock = socket(AF_INET, SOCK_STREAM, 0)) == -1) { |
| fprintf(stderr, "socket() failed: %s\n", strerror(errno)); |
| return 1; |
| } |
| |
| /* re-use addr */ |
| rs = 1; |
| setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, &rs, sizeof(rs)); |
| |
| /* bind */ |
| memset(&addr, 0, sizeof(addr)); |
| addr.sin_family = AF_INET; |
| addr.sin_addr.s_addr = INADDR_ANY; |
| addr.sin_port = htons(strtol(argv[3], 0, 10)); |
| if (bind(listen_sock, (struct sockaddr *)&addr, sizeof(addr)) == -1) { |
| fprintf(stderr, "bind() failed: %s\n", strerror(errno)); |
| return 1; |
| } |
| |
| /* listen */ |
| if (listen(listen_sock, 5) == -1) { |
| fprintf(stderr, "listen() failed: %s\n", strerror(errno)); |
| return 1; |
| } |
| |
| /* wait for client connection */ |
| if ((client.sock = accept(listen_sock, (struct sockaddr *)&addr, &addrlen)) == -1) { |
| fprintf(stderr, "accept() failed: %s\n", strerror(errno)); |
| return 1; |
| } |
| |
| /* create server socket */ |
| if ((server.sock = socket(AF_INET, SOCK_STREAM, 0)) == -1) { |
| fprintf(stderr, "socket() failed: %s\n", strerror(errno)); |
| return 1; |
| } |
| |
| /* bind */ |
| memset(&addr, 0, sizeof(addr)); |
| addr.sin_family = AF_INET; |
| if (bind(server.sock, (struct sockaddr *)&addr, sizeof(addr)) == -1) { |
| fprintf(stderr, "bind() failed: %s\n", strerror(errno)); |
| return 1; |
| } |
| |
| /* connect */ |
| memset(&addr, 0, sizeof(addr)); |
| if (inet_pton(AF_INET, argv[1], &addr.sin_addr) != 1) { |
| fprintf(stderr, "inet_pton() failed: %s\n", strerror(errno)); |
| return 1; |
| } |
| addr.sin_family = AF_INET; |
| addr.sin_port = htons(strtol(argv[2], 0, 10)); |
| if (connect(server.sock, (struct sockaddr *)&addr, sizeof(addr)) == -1) { |
| fprintf(stderr, "server() failed: %s\n", strerror(errno)); |
| return 1; |
| } |
| |
| /* initialize connection structs */ |
| server.name = "\e[31mSERVER"; |
| server.remote = &client; |
| client.name = "\e[34mCLIENT"; |
| client.remote = &server; |
| |
| /* initialize telnet boxes */ |
| libtelnet_init(&server.telnet); |
| libtelnet_init(&client.telnet); |
| |
| /* initialize poll descriptors */ |
| memset(pfd, 0, sizeof(pfd)); |
| pfd[0].fd = server.sock; |
| pfd[0].events = POLLIN | POLLHUP; |
| pfd[1].fd = client.sock; |
| pfd[1].events = POLLIN | POLLHUP; |
| |
| /* loop while both connections are open */ |
| while (poll(pfd, 2, -1) != -1) { |
| /* read from server */ |
| if (pfd[0].revents & POLLIN) { |
| if ((rs = recv(pfd[0].fd, buffer, sizeof(buffer), 0)) > 0) |
| libtelnet_push(&server.telnet, buffer, rs, (void*)&server); |
| } |
| if (pfd[0].revents & POLLHUP) |
| break; |
| |
| /* read from client */ |
| if (pfd[1].revents & POLLIN) { |
| if ((rs = recv(pfd[1].fd, buffer, sizeof(buffer), 0)) > 0) |
| libtelnet_push(&client.telnet, buffer, rs, (void*)&client); |
| } |
| if (pfd[1].revents & POLLHUP) |
| break; |
| } |
| |
| /* clean up */ |
| libtelnet_free(&server.telnet); |
| libtelnet_free(&client.telnet); |
| close(server.sock); |
| close(client.sock); |
| close(listen_sock); |
| |
| return 0; |
| } |