296 lines
7.8 KiB
C
296 lines
7.8 KiB
C
// SecLink proxy — bridges an 86Box serial connection to a telnet BBS
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//
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// 86Box (DOS terminal) ←→ TCP ←→ proxy ←→ TCP ←→ BBS
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// secLink protocol plain telnet
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//
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// Usage: proxy [listen_port] [bbs_host] [bbs_port]
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// Defaults: 2323 bbs.duensing.digital 23
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <signal.h>
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#include <errno.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <netdb.h>
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#include <poll.h>
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#include <fcntl.h>
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#include "sockShim.h"
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#include "../seclink/secLink.h"
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#include "../security/security.h"
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// ========================================================================
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// Defines
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// ========================================================================
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#define DEFAULT_LISTEN_PORT 2323
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#define DEFAULT_BBS_HOST "bbs.duensing.digital"
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#define DEFAULT_BBS_PORT 23
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#define CHANNEL_TERMINAL 0
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#define POLL_TIMEOUT_MS 10
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// ========================================================================
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// Static globals
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// ========================================================================
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static volatile bool sRunning = true;
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// ========================================================================
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// Static prototypes (alphabetical)
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// ========================================================================
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static int connectToBbs(const char *host, int port);
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static int createListenSocket(int port);
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static void onRecvFromDos(void *ctx, const uint8_t *data, int len, uint8_t channel);
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static void seedRng(void);
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static void sigHandler(int sig);
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// ========================================================================
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// Static functions (alphabetical)
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// ========================================================================
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static int connectToBbs(const char *host, int port) {
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struct addrinfo hints;
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struct addrinfo *res;
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char portStr[16];
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int fd;
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memset(&hints, 0, sizeof(hints));
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hints.ai_family = AF_INET;
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hints.ai_socktype = SOCK_STREAM;
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snprintf(portStr, sizeof(portStr), "%d", port);
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if (getaddrinfo(host, portStr, &hints, &res) != 0) {
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return -1;
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}
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fd = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
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if (fd < 0) {
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freeaddrinfo(res);
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return -1;
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}
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if (connect(fd, res->ai_addr, res->ai_addrlen) < 0) {
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close(fd);
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freeaddrinfo(res);
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return -1;
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}
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freeaddrinfo(res);
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return fd;
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}
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static int createListenSocket(int port) {
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struct sockaddr_in addr;
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int fd;
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int opt = 1;
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fd = socket(AF_INET, SOCK_STREAM, 0);
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if (fd < 0) {
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return -1;
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}
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setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
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memset(&addr, 0, sizeof(addr));
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addr.sin_family = AF_INET;
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addr.sin_addr.s_addr = INADDR_ANY;
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addr.sin_port = htons(port);
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if (bind(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
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close(fd);
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return -1;
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}
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if (listen(fd, 1) < 0) {
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close(fd);
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return -1;
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}
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return fd;
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}
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static void onRecvFromDos(void *ctx, const uint8_t *data, int len, uint8_t channel) {
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int bbsFd = *(int *)ctx;
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(void)channel;
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int sent = 0;
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while (sent < len) {
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ssize_t n = write(bbsFd, data + sent, len - sent);
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if (n <= 0) {
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break;
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}
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sent += (int)n;
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}
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}
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static void seedRng(void) {
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uint8_t entropy[32];
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FILE *f;
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f = fopen("/dev/urandom", "rb");
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if (f) {
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if (fread(entropy, 1, sizeof(entropy), f) < sizeof(entropy)) {
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fprintf(stderr, "Warning: short read from /dev/urandom\n");
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}
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fclose(f);
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}
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secRngSeed(entropy, sizeof(entropy));
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}
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static void sigHandler(int sig) {
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(void)sig;
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sRunning = false;
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}
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// ========================================================================
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// Main
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// ========================================================================
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int main(int argc, char *argv[]) {
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int listenPort = DEFAULT_LISTEN_PORT;
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const char *bbsHost = DEFAULT_BBS_HOST;
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int bbsPort = DEFAULT_BBS_PORT;
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int listenFd;
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int clientFd;
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int bbsFd;
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SecLinkT *link;
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struct sockaddr_in clientAddr;
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socklen_t clientLen;
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struct pollfd fds[2];
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int rc;
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if (argc > 1 && (strcmp(argv[1], "-h") == 0 || strcmp(argv[1], "--help") == 0)) {
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printf("Usage: %s [listen_port] [bbs_host] [bbs_port]\n", argv[0]);
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printf("Defaults: %d %s %d\n", DEFAULT_LISTEN_PORT, DEFAULT_BBS_HOST, DEFAULT_BBS_PORT);
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return 0;
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}
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if (argc > 1) {
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listenPort = atoi(argv[1]);
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}
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if (argc > 2) {
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bbsHost = argv[2];
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}
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if (argc > 3) {
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bbsPort = atoi(argv[3]);
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}
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signal(SIGPIPE, SIG_IGN);
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signal(SIGINT, sigHandler);
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signal(SIGTERM, sigHandler);
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// Listen for 86Box connection
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listenFd = createListenSocket(listenPort);
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if (listenFd < 0) {
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fprintf(stderr, "Failed to listen on port %d: %s\n", listenPort, strerror(errno));
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return 1;
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}
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printf("Listening on port %d...\n", listenPort);
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// Accept connection from 86Box
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clientLen = sizeof(clientAddr);
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clientFd = accept(listenFd, (struct sockaddr *)&clientAddr, &clientLen);
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close(listenFd);
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if (clientFd < 0) {
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fprintf(stderr, "Accept failed: %s\n", strerror(errno));
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return 1;
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}
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printf("86Box connected.\n");
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// Associate socket with COM0 for the secLink stack
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sockShimSetFd(0, clientFd);
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// Connect to BBS
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printf("Connecting to %s:%d...\n", bbsHost, bbsPort);
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bbsFd = connectToBbs(bbsHost, bbsPort);
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if (bbsFd < 0) {
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fprintf(stderr, "Failed to connect to BBS: %s\n", strerror(errno));
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close(clientFd);
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return 1;
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}
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printf("BBS connected.\n");
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// Seed RNG from /dev/urandom and open secLink
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seedRng();
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link = secLinkOpen(0, 115200, 8, 'N', 1, 0, onRecvFromDos, &bbsFd);
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if (!link) {
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fprintf(stderr, "Failed to open secLink.\n");
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close(bbsFd);
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close(clientFd);
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return 1;
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}
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// DH key exchange (blocks until both sides complete)
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printf("Waiting for secLink handshake...\n");
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rc = secLinkHandshake(link);
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if (rc != SECLINK_SUCCESS) {
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fprintf(stderr, "Handshake failed: %d\n", rc);
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secLinkClose(link);
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close(bbsFd);
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return 1;
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}
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printf("Handshake complete. Proxying traffic.\n");
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// Set BBS socket non-blocking for the main loop
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int flags = fcntl(bbsFd, F_GETFL, 0);
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fcntl(bbsFd, F_SETFL, flags | O_NONBLOCK);
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// Main proxy loop
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fds[0].fd = clientFd;
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fds[0].events = POLLIN;
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fds[1].fd = bbsFd;
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fds[1].events = POLLIN;
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while (sRunning) {
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poll(fds, 2, POLL_TIMEOUT_MS);
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// Process incoming secLink packets from 86Box
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// (callback forwards decrypted data to BBS)
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secLinkPoll(link);
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// Read from BBS and send encrypted to 86Box
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if (fds[1].revents & POLLIN) {
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uint8_t buf[SECLINK_MAX_PAYLOAD];
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ssize_t n = read(bbsFd, buf, sizeof(buf));
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if (n <= 0) {
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printf("BBS disconnected.\n");
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break;
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}
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secLinkSend(link, buf, (int)n, CHANNEL_TERMINAL, true, true);
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}
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// Check for disconnects
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if (fds[0].revents & (POLLERR | POLLHUP)) {
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printf("86Box disconnected.\n");
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break;
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}
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if (fds[1].revents & (POLLERR | POLLHUP)) {
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printf("BBS disconnected.\n");
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break;
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}
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}
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printf("Shutting down.\n");
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secLinkClose(link);
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close(bbsFd);
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close(clientFd);
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return 0;
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}
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