| /* |
| * Sean Middleditch |
| * sean@sourcemud.org |
| * |
| * The author or authors of this code dedicate any and all copyright interest |
| * in this code to the public domain. We make this dedication for the benefit |
| * of the public at large and to the detriment of our heirs and successors. We |
| * intend this dedication to be an overt act of relinquishment in perpetuity of |
| * all present and future rights to this code under copyright law. |
| */ |
| |
| #include <sys/socket.h> |
| #include <netinet/in.h> |
| #include <arpa/inet.h> |
| #include <netdb.h> |
| #include <poll.h> |
| #include <errno.h> |
| #include <stdio.h> |
| #include <string.h> |
| #include <stdlib.h> |
| #include <ctype.h> |
| #include <unistd.h> |
| |
| #ifdef HAVE_ZLIB |
| #include "zlib.h" |
| #endif |
| |
| #include "libtelnet.h" |
| |
| #ifdef ENABLE_COLOR |
| # define COLOR_SERVER "\e[35m" |
| # define COLOR_CLIENT "\e[34m" |
| # define COLOR_BOLD "\e[1m" |
| # define COLOR_UNBOLD "\e[22m" |
| # define COLOR_NORMAL "\e[0m" |
| #else |
| # define COLOR_SERVER "" |
| # define COLOR_CLIENT "" |
| # define COLOR_BOLD "" |
| # define COLOR_UNBOLD "" |
| # define COLOR_NORMAL "" |
| #endif |
| |
| 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("<" COLOR_BOLD "0x%02X" COLOR_UNBOLD ">\n", |
| (int)buffer[i]); |
| else |
| printf("<" COLOR_BOLD "0x%02X" COLOR_UNBOLD ">", (int)buffer[i]); |
| } |
| } |
| |
| static void _send(int sock, unsigned char *buffer, unsigned int size) { |
| int rs; |
| |
| /* send data */ |
| while (size > 0) { |
| if ((rs = send(sock, buffer, size, 0)) == -1) { |
| fprintf(stderr, "send() failed: %s\n", strerror(errno)); |
| exit(1); |
| } else if (rs == 0) { |
| fprintf(stderr, "send() unexpectedly returned 0\n"); |
| exit(1); |
| } |
| |
| /* update pointer and size to see if we've got more to send */ |
| buffer += rs; |
| size -= rs; |
| } |
| } |
| |
| static void _event_handler(struct libtelnet_t *telnet, |
| struct libtelnet_event_t *ev, void *user_data) { |
| struct conn_t *conn = (struct conn_t*)user_data; |
| |
| switch (ev->type) { |
| /* data received */ |
| case LIBTELNET_EV_DATA: |
| printf("%s DATA: ", conn->name); |
| print_buffer(ev->buffer, ev->size); |
| printf(COLOR_NORMAL "\n"); |
| |
| libtelnet_send_data(&conn->remote->telnet, ev->buffer, ev->size); |
| break; |
| /* data must be sent */ |
| case LIBTELNET_EV_SEND: |
| /* DONT SPAM |
| printf("%s SEND: ", conn->name); |
| print_buffer(ev->buffer, ev->size); |
| printf(COLOR_BOLD "\n"); |
| */ |
| |
| _send(conn->sock, ev->buffer, ev->size); |
| break; |
| /* IAC command */ |
| case LIBTELNET_EV_IAC: |
| printf("%s IAC %s" COLOR_NORMAL "\n", conn->name, |
| get_cmd(ev->command)); |
| |
| libtelnet_send_command(&conn->remote->telnet, ev->command); |
| break; |
| /* negotiation, WILL */ |
| case LIBTELNET_EV_WILL: |
| printf("%s IAC WILL %d (%s)" COLOR_NORMAL "\n", conn->name, |
| (int)ev->telopt, get_opt(ev->telopt)); |
| libtelnet_send_negotiate(&conn->remote->telnet, LIBTELNET_WILL, |
| ev->telopt); |
| break; |
| /* negotiation, WONT */ |
| case LIBTELNET_EV_WONT: |
| printf("%s IAC WONT %d (%s)" COLOR_NORMAL "\n", conn->name, |
| (int)ev->telopt, get_opt(ev->telopt)); |
| libtelnet_send_negotiate(&conn->remote->telnet, LIBTELNET_WONT, |
| ev->telopt); |
| break; |
| /* negotiation, DO */ |
| case LIBTELNET_EV_DO: |
| printf("%s IAC DO %d (%s)" COLOR_NORMAL "\n", conn->name, |
| (int)ev->telopt, get_opt(ev->telopt)); |
| libtelnet_send_negotiate(&conn->remote->telnet, LIBTELNET_DO, |
| ev->telopt); |
| break; |
| case LIBTELNET_EV_DONT: |
| printf("%s IAC DONT %d (%s)" COLOR_NORMAL "\n", conn->name, |
| (int)ev->telopt, get_opt(ev->telopt)); |
| libtelnet_send_negotiate(&conn->remote->telnet, LIBTELNET_DONT, |
| ev->telopt); |
| break; |
| /* subnegotiation */ |
| case LIBTELNET_EV_SUBNEGOTIATION: |
| printf("%s SUB %d (%s)", conn->name, (int)ev->telopt, |
| get_opt(ev->telopt)); |
| if (ev->size > 0) { |
| printf(" [%u]: ", ev->size); |
| print_buffer(ev->buffer, ev->size); |
| } |
| printf(COLOR_NORMAL "\n"); |
| |
| libtelnet_send_subnegotiation(&conn->remote->telnet, ev->telopt, |
| ev->buffer, ev->size); |
| break; |
| /* compression notification */ |
| case LIBTELNET_EV_COMPRESS: |
| printf("%s COMPRESSION %s" COLOR_NORMAL "\n", conn->name, |
| ev->command ? "ON" : "OFF"); |
| break; |
| /* warning */ |
| case LIBTELNET_EV_WARNING: |
| printf("%s WARNING: %.*s" COLOR_NORMAL "\n", conn->name, ev->size, |
| ev->buffer); |
| break; |
| /* error */ |
| case LIBTELNET_EV_ERROR: |
| printf("%s ERROR: %.*s" COLOR_NORMAL "\n", conn->name, ev->size, |
| ev->buffer); |
| exit(1); |
| } |
| } |
| |
| int main(int argc, char **argv) { |
| unsigned char buffer[512]; |
| short listen_port; |
| int listen_sock; |
| int rs; |
| struct sockaddr_in addr; |
| socklen_t addrlen; |
| struct pollfd pfd[2]; |
| struct conn_t server; |
| struct conn_t client; |
| struct addrinfo *ai; |
| struct addrinfo hints; |
| |
| /* check usage */ |
| if (argc != 4) { |
| fprintf(stderr, "Usage:\n ./telnet-proxy <remote ip> <remote port> " |
| "<local port>\n"); |
| return 1; |
| } |
| |
| /* parse listening port */ |
| listen_port = strtol(argv[3], 0, 10); |
| |
| /* loop forever, until user kills process */ |
| for (;;) { |
| /* create listening socket */ |
| if ((listen_sock = socket(AF_INET, SOCK_STREAM, 0)) == -1) { |
| fprintf(stderr, "socket() failed: %s\n", strerror(errno)); |
| return 1; |
| } |
| |
| /* reuse address option */ |
| rs = 1; |
| setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, &rs, sizeof(rs)); |
| |
| /* bind to listening addr/port */ |
| memset(&addr, 0, sizeof(addr)); |
| addr.sin_family = AF_INET; |
| addr.sin_addr.s_addr = INADDR_ANY; |
| addr.sin_port = htons(listen_port); |
| if (bind(listen_sock, (struct sockaddr *)&addr, sizeof(addr)) == -1) { |
| fprintf(stderr, "bind() failed: %s\n", strerror(errno)); |
| return 1; |
| } |
| |
| printf("LISTENING ON PORT %d\n", listen_port); |
| |
| /* wait for client */ |
| if (listen(listen_sock, 1) == -1) { |
| fprintf(stderr, "listen() failed: %s\n", strerror(errno)); |
| return 1; |
| } |
| addrlen = sizeof(addr); |
| if ((client.sock = accept(listen_sock, (struct sockaddr *)&addr, |
| &addrlen)) == -1) { |
| fprintf(stderr, "accept() failed: %s\n", strerror(errno)); |
| return 1; |
| } |
| |
| printf("CLIENT CONNECTION RECEIVED\n"); |
| |
| /* stop listening now that we have a client */ |
| close(listen_sock); |
| |
| /* look up server host */ |
| memset(&hints, 0, sizeof(hints)); |
| hints.ai_family = AF_UNSPEC; |
| hints.ai_socktype = SOCK_STREAM; |
| if ((rs = getaddrinfo(argv[1], argv[2], &hints, &ai)) != 0) { |
| fprintf(stderr, "getaddrinfo() failed for %s: %s\n", argv[1], |
| gai_strerror(rs)); |
| 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 server socket */ |
| 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 */ |
| if (connect(server.sock, ai->ai_addr, ai->ai_addrlen) == -1) { |
| fprintf(stderr, "server() failed: %s\n", strerror(errno)); |
| return 1; |
| } |
| |
| /* free address lookup info */ |
| freeaddrinfo(ai); |
| |
| printf("SERVER CONNECTION ESTABLISHED\n"); |
| |
| /* initialize connection structs */ |
| server.name = COLOR_SERVER "SERVER"; |
| server.remote = &client; |
| client.name = COLOR_CLIENT "CLIENT"; |
| client.remote = &server; |
| |
| /* initialize telnet boxes */ |
| libtelnet_init(&server.telnet, _event_handler, LIBTELNET_MODE_PROXY, |
| &server); |
| libtelnet_init(&client.telnet, _event_handler, LIBTELNET_MODE_PROXY, |
| &client); |
| |
| /* initialize poll descriptors */ |
| memset(pfd, 0, sizeof(pfd)); |
| pfd[0].fd = server.sock; |
| pfd[0].events = POLLIN; |
| pfd[1].fd = client.sock; |
| pfd[1].events = POLLIN; |
| |
| /* loop while both connections are open */ |
| while (poll(pfd, 2, -1) != -1) { |
| /* read from server */ |
| if (pfd[0].revents & POLLIN) { |
| if ((rs = recv(server.sock, buffer, sizeof(buffer), 0)) > 0) { |
| libtelnet_push(&server.telnet, buffer, rs); |
| } else if (rs == 0) { |
| printf("%s DISCONNECTED" COLOR_NORMAL "\n", server.name); |
| break; |
| } else { |
| fprintf(stderr, "recv(server) failed: %s\n", |
| strerror(errno)); |
| exit(1); |
| } |
| } |
| |
| /* read from client */ |
| if (pfd[1].revents & POLLIN) { |
| if ((rs = recv(client.sock, buffer, sizeof(buffer), 0)) > 0) { |
| libtelnet_push(&client.telnet, buffer, rs); |
| } else if (rs == 0) { |
| printf("%s DISCONNECTED" COLOR_NORMAL "\n", client.name); |
| break; |
| } else { |
| fprintf(stderr, "recv(client) failed: %s\n", |
| strerror(errno)); |
| exit(1); |
| } |
| } |
| } |
| |
| /* clean up */ |
| libtelnet_free(&server.telnet); |
| libtelnet_free(&client.telnet); |
| close(server.sock); |
| close(client.sock); |
| |
| /* all done */ |
| printf("BOTH CONNECTIONS CLOSED\n"); |
| } |
| |
| /* not that we can reach this, but GCC will cry if it's not here */ |
| return 0; |
| } |