Merge pull request 'TLS transport: OpenSSL-based encrypted TCP' (#13) from tls-transport into main

.gitea/workflows/ci.yaml

@@ -5,7 +5,7 @@ on: [push, pull_request]
 jobs:
   build-and-test:
     runs-on: ubuntu-latest
-    container: gitea.tap-tap.win/taptap/fastsync-ci:v4
+    container: gitea.tap-tap.win/taptap/fastsync-ci:v5
     steps:
       - name: Checkout
         uses: actions/checkout@v4

CMakeLists.txt

@@ -19,6 +19,8 @@ if(NOT ZSTD_LIBRARY)
 	message(FATAL_ERROR "zstd library not found. Ensure it is in your nix-shell!")
 endif()
 
+find_package(OpenSSL REQUIRED)
+
 file(GLOB SHARED_SRCS "src/shared/*.c")
 file(GLOB SERVER_SRCS "src/server/*.c")
 file(GLOB CLIENT_SRCS "src/client/*.c")
@@ -26,13 +28,13 @@ file(GLOB TEST_SRCS "tests/*.c")
 
 add_executable(server ${SERVER_SRCS} ${SHARED_SRCS})
 target_include_directories(server PRIVATE src/shared src/server src/client)
-target_link_libraries(server PRIVATE Threads::Threads ${ZSTD_LIBRARY})
+target_link_libraries(server PRIVATE Threads::Threads ${ZSTD_LIBRARY} OpenSSL::SSL OpenSSL::Crypto)
 
 add_executable(client ${CLIENT_SRCS} ${SHARED_SRCS})
 target_include_directories(client PRIVATE src/shared src/server src/client)
-target_link_libraries(client PRIVATE Threads::Threads ${ZSTD_LIBRARY})
+target_link_libraries(client PRIVATE Threads::Threads ${ZSTD_LIBRARY} OpenSSL::SSL OpenSSL::Crypto)
 
 add_executable(tests ${TEST_SRCS} ${SHARED_SRCS} src/client/scanner.c)
 target_include_directories(tests PRIVATE tests src/shared src/server src/client)
-target_link_libraries(tests PRIVATE Threads::Threads ${ZSTD_LIBRARY})
+target_link_libraries(tests PRIVATE Threads::Threads ${ZSTD_LIBRARY} OpenSSL::SSL OpenSSL::Crypto)
 

Dockerfile

@@ -1,6 +1,6 @@
 FROM ubuntu:24.04
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    gcc g++ make libc6-dev cmake libzstd-dev git ca-certificates curl && \
+    gcc g++ make libc6-dev cmake libzstd-dev libssl-dev git ca-certificates curl && \
     curl -fsSL https://deb.nodesource.com/setup_20.x | bash - && \
     apt-get install -y --no-install-recommends nodejs && \
     rm -rf /var/lib/apt/lists/*

shell.nix

@@ -14,6 +14,7 @@ pkgs.mkShell {
 
   buildInputs = with pkgs; [
     zstd
+    openssl
   ];
 
   NIX_ENFORCE_PURITY = 0;

src/client/client_cli.c

@@ -2,6 +2,7 @@
 #include "config.h"
 #include "log.h"
 #include "protocol.h"
+#include "transport_tls.h"
 #include "utils.h"
 #include <errno.h>
 #include <limits.h>
@@ -47,6 +48,10 @@ static void print_usage(void) {
   printf("  --server-host <ip>  Server IP address (default: 127.0.0.1)\n");
   printf("  --server-port <n>   Server port (default: 8080)\n");
   printf("  --bwlimit <KB/s>    Bandwidth limit in kilobytes per second\n");
+  printf("  --tls               Enable TLS encryption\n");
+  printf("  --cert <path>       TLS certificate file (PEM)\n");
+  printf("  --key <path>        TLS private key file (PEM)\n");
+  printf("  --ca <path>         TLS CA certificate file (PEM)\n");
   printf("  --help              Show this help\n");
 }
 
@@ -154,6 +159,17 @@ int main(int argc, char *argv[]) {
       unsigned long long val = strtoull(argv[++i], NULL, 10);
       if (val > 0)
         config->chunk_size = val;
+    } else if (strcmp(argv[i], "--tls") == 0) {
+      config->use_tls = true;
+    } else if (strcmp(argv[i], "--cert") == 0 && i + 1 < argc) {
+      free(config->tls_cert);
+      config->tls_cert = str_dup(argv[++i]);
+    } else if (strcmp(argv[i], "--key") == 0 && i + 1 < argc) {
+      free(config->tls_key);
+      config->tls_key = str_dup(argv[++i]);
+    } else if (strcmp(argv[i], "--ca") == 0 && i + 1 < argc) {
+      free(config->tls_ca);
+      config->tls_ca = str_dup(argv[++i]);
     } else if (strcmp(argv[i], "-v") == 0 || strcmp(argv[i], "--verbose") == 0) {
       set_log_level(LOG_LEVEL_DEBUG);
     } else if (argv[i][0] == '-') {
@@ -215,6 +231,14 @@ int main(int argc, char *argv[]) {
     config->use_metadata = true;
   }
 
+  if (config->use_tls) {
+    if (!config->tls_cert || !config->tls_key) {
+      fprintf(stderr, "Error: --tls requires --cert and --key\n");
+      return 1;
+    }
+    tls_global_init();
+  }
+
   if (config->use_multithreading)
     return send_files_multithreaded(config);
   return send_files(config);

src/client/client_send.c

@@ -11,6 +11,7 @@
 #include "scanner.h"
 #include "transport_tcp.h"
 #include "transport_ssh.h"
+#include "transport_tls.h"
 #include "utils.h"
 #include <stdio.h>
 #include <stdlib.h>
@@ -98,6 +99,16 @@ static int send_chunks_multithreaded(void *pipeline_context) {
       return 1;
     }
     client = client_connect_ssh(context->config->ssh_destination, context->config->ssh_port);
+  } else if (context->config->use_tls) {
+    client = client_create();
+    if (!client || !client_connect_tls(client, server_host, server_port,
+                                        context->config->tls_cert,
+                                        context->config->tls_key,
+                                        context->config->tls_ca)) {
+      if (client) client_delete(client);
+      fprintf(stderr, "Error: could not connect to server via TLS\n");
+      return thrd_error;
+    }
   } else {
     client = client_create();
     if (!client || !client_connect(client, server_host, server_port)) {
@@ -242,6 +253,15 @@ int send_files(Config *config) {
     }
     client = client_connect_ssh(config->ssh_destination, config->ssh_port);
     if (!client) return 1;
+  } else if (config->use_tls) {
+    client = client_create();
+    if (!client || !client_connect_tls(client, server_host, server_port,
+                                        config->tls_cert, config->tls_key,
+                                        config->tls_ca)) {
+      if (client) client_delete(client);
+      fprintf(stderr, "Error: could not connect to server via TLS\n");
+      return 1;
+    }
   } else {
     client = client_create();
     if (!client || !client_connect(client, server_host, server_port)) {

src/server/server.c

@@ -8,6 +8,7 @@
 #include "protocol.h"
 #include "queue.h"
 #include "transport_tcp.h"
+#include "transport_tls.h"
 #include "unistd.h"
 #include "utils.h"
 #include <signal.h>
@@ -118,24 +119,88 @@ static void cleanup(int sig) {
   _exit(0);
 }
 
+static void print_server_usage(void) {
+  printf("FastSync Server\n");
+  printf("Usage: fastsync-server [options]\n");
+  printf("\n");
+  printf("Options:\n");
+  printf("  --stdio             Run in stdio mode (SSH transport)\n");
+  printf("  -p <port>           TCP port (default: 8080, range: 1-65535)\n");
+  printf("  --tls               Enable TLS encryption\n");
+  printf("  --cert <path>       TLS certificate file (PEM)\n");
+  printf("  --key <path>        TLS private key file (PEM)\n");
+  printf("  --ca <path>         TLS CA certificate file (PEM)\n");
+  printf("  -v, --verbose       Enable debug logging\n");
+  printf("  --help              Show this help\n");
+}
+
 int main(int argc, char *argv[]) {
+  bool use_tls = false;
+  char *tls_cert = NULL;
+  char *tls_key = NULL;
+  char *tls_ca = NULL;
+  int port = 8080;
+
   signal(SIGPIPE, SIG_IGN);
   for (int i = 1; i < argc; i++) {
-    if (strcmp(argv[i], "--stdio") == 0) {
+    if (strcmp(argv[i], "--help") == 0) {
+      print_server_usage();
+      return 0;
+    } else if (strcmp(argv[i], "--stdio") == 0) {
       io_set_fds(STDIN_FILENO, STDOUT_FILENO);
       handler(STDIN_FILENO);
       return 0;
     } else if (strcmp(argv[i], "-v") == 0 || strcmp(argv[i], "--verbose") == 0) {
       set_log_level(LOG_LEVEL_DEBUG);
+    } else if (strcmp(argv[i], "--tls") == 0) {
+      use_tls = true;
+    } else if (strcmp(argv[i], "--cert") == 0 && i + 1 < argc) {
+      tls_cert = argv[++i];
+    } else if (strcmp(argv[i], "--key") == 0 && i + 1 < argc) {
+      tls_key = argv[++i];
+    } else if (strcmp(argv[i], "--ca") == 0 && i + 1 < argc) {
+      tls_ca = argv[++i];
+    } else if (strcmp(argv[i], "-p") == 0 && i + 1 < argc) {
+      char *end;
+      long p = strtol(argv[++i], &end, 10);
+      if (*end || p <= 0 || p > 65535) {
+        fprintf(stderr, "Error: invalid port '%s' (must be 1-65535)\n", argv[i]);
+        return 1;
+      }
+      port = (int)p;
+    } else if (argv[i][0] == '-') {
+      fprintf(stderr, "Unknown option: %s\n", argv[i]);
+      print_server_usage();
+      return 1;
     }
   }
+
+  if (tls_ca && !use_tls) {
+    log_message(LOG_LEVEL_WARNING, "--ca has no effect without --tls");
+  }
+
   signal(SIGINT, cleanup);
   signal(SIGTERM, cleanup);
-  g_server = server_create(8080);
+  g_server = server_create(port);
   if (g_server == NULL) {
     log_message(LOG_LEVEL_ERROR, "Failed to create server");
     return 1;
   }
-  server_listen(g_server, handler);
+  if (use_tls) {
+    if (!tls_cert || !tls_key) {
+      fprintf(stderr, "Error: --tls requires --cert and --key\n");
+      server_delete(&g_server);
+      return 1;
+    }
+    tls_global_init();
+    if (!server_create_tls(g_server, tls_cert, tls_key, tls_ca)) {
+      log_message(LOG_LEVEL_ERROR, "Failed to set up TLS");
+      server_delete(&g_server);
+      return 1;
+    }
+    server_listen_tls(g_server, handler);
+  } else {
+    server_listen(g_server, handler);
+  }
   return 0;
 }

src/shared/config.c

@@ -39,6 +39,10 @@ Config *config_create(char *version, char *send_directory,
   config->max_size = 0;
   config->min_size = 0;
   config->use_incremental = false;
+  config->use_tls = false;
+  config->tls_cert = NULL;
+  config->tls_key = NULL;
+  config->tls_ca = NULL;
   return config;
 }
 
@@ -74,6 +78,9 @@ void config_delete(Config *config) {
   for (int i = 0; i < config->include_count; i++)
     free(config->include_patterns[i]);
   free(config->include_patterns);
+  free(config->tls_cert);
+  free(config->tls_key);
+  free(config->tls_ca);
   free(config);
 }
 
@@ -149,6 +156,10 @@ Config *config_receive(int file_descriptor) {
   config->include_count = 0;
   config->max_size = 0;
   config->min_size = 0;
+  config->use_tls = false;
+  config->tls_cert = NULL;
+  config->tls_key = NULL;
+  config->tls_ca = NULL;
   if (!send_status(file_descriptor, STATUS_OK)) goto error;
   return config;
 

src/shared/config.h

@@ -33,6 +33,10 @@ typedef struct Config {
   unsigned long long max_size;
   unsigned long long min_size;
   bool use_incremental;
+  bool use_tls;
+  char *tls_cert;
+  char *tls_key;
+  char *tls_ca;
 } Config;
 
 #define PROTOCOL_VERSION "1.1.0"

src/shared/protocol.c

@@ -1,6 +1,7 @@
 #include "protocol.h"
 #include "log.h"
 #include <errno.h>
+#include <openssl/ssl.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -9,6 +10,7 @@
 
 static __thread int io_read_fd = -1;
 static __thread int io_write_fd = -1;
+static SSL *io_ssl = NULL;
 
 static unsigned long long io_bwlimit = 0;
 static long long bw_tokens = 0;
@@ -54,6 +56,10 @@ static void bw_throttle(size_t bytes_written) {
   }
 }
 
+void io_set_ssl(SSL *ssl) {
+  io_ssl = ssl;
+}
+
 static int io_fd(int dir_fd, int file_descriptor) {
   return (dir_fd != -1) ? dir_fd : file_descriptor;
 }
@@ -66,8 +72,11 @@ bool send_n_data(int file_descriptor, void *data, size_t data_size) {
     size_t chunk = data_size - total_bytes_send;
     if (io_bwlimit > 0 && chunk > 65536)
       chunk = 65536;
-    ssize_t bytes_send =
-        write(fd, (char *)data + total_bytes_send, chunk);
+    ssize_t bytes_send;
+    if (io_ssl)
+      bytes_send = SSL_write(io_ssl, (char *)data + total_bytes_send, chunk);
+    else
+      bytes_send = write(fd, (char *)data + total_bytes_send, chunk);
     if (bytes_send <= 0) {
       log_message(LOG_LEVEL_ERROR, "Could not send data");
       return false;
@@ -84,8 +93,13 @@ bool receive_n_data(int file_descriptor, void *data, size_t data_size) {
   int fd = io_fd(io_read_fd, file_descriptor);
   size_t total_bytes_received = 0;
   while (total_bytes_received < data_size) {
-    ssize_t bytes_received =
-        read(fd, (char *)data + total_bytes_received, data_size - total_bytes_received);
+    ssize_t bytes_received;
+    if (io_ssl)
+      bytes_received = SSL_read(io_ssl, (char *)data + total_bytes_received,
+                                data_size - total_bytes_received);
+    else
+      bytes_received = read(fd, (char *)data + total_bytes_received,
+                             data_size - total_bytes_received);
     if (bytes_received <= 0) {
       if (bytes_received == 0)
         log_message(LOG_LEVEL_ERROR, "Connection closed while receiving data");

src/shared/protocol.h

@@ -5,11 +5,15 @@
 #include <stdbool.h>
 #include <stddef.h>
 
+typedef struct ssl_st SSL;
+
 typedef int Status;
 enum NET_STATUS { STATUS_OK, STATUS_ERROR, STATUS_FINISHED, STATUS_NEXT, STATUS_CHUNK, STATUS_MANIFEST, STATUS_CHECK };
 
 void io_set_fds(int read_fd, int write_fd);
 void io_set_bwlimit(unsigned long long bytes_per_sec);
+typedef struct ssl_st SSL;
+void io_set_ssl(SSL *ssl);
 bool send_n_data(int file_descriptor, void *data, size_t data_size);
 bool receive_n_data(int file_descriptor, void *data, size_t data_size);
 

src/shared/transport_ssh.c

@@ -143,5 +143,7 @@ Client *client_connect_ssh(char *destination, int port) {
   client->address.sin_family = AF_UNIX;
   client->address_length = 0;
   client->ssh_child_pid = pid;
+  client->ssl = NULL;
+  client->ssl_ctx = NULL;
   return client;
 }

src/shared/transport_tcp.c

@@ -1,6 +1,8 @@
 #include "transport_tcp.h"
 #include "log.h"
+#include "protocol.h"
 #include <arpa/inet.h>
+#include <openssl/ssl.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -36,6 +38,7 @@ Server *server_create(int port) {
   server->address.sin_addr.s_addr = INADDR_ANY;
   server->address.sin_port = htons(port);
   server->address_length = sizeof(server->address);
+  server->ssl_ctx = NULL;
 
   if (bind(server->file_descriptor, (struct sockaddr *)&server->address,
            server->address_length) < 0) {
@@ -51,43 +54,63 @@ Server *server_create(int port) {
 void server_delete(Server **server) {
   if (server == NULL || *server == NULL) return;
   close((*server)->file_descriptor);
+  if ((*server)->ssl_ctx) {
+    SSL_CTX_free((*server)->ssl_ctx);
+    (*server)->ssl_ctx = NULL;
+  }
   free(*server);
   *server = NULL;
 }
 
-bool server_listen(Server *server, void (*handler)(int file_descriptor)) {
-  log_message(LOG_LEVEL_INFO, "Start Listening on Port: %d",
-              server->address.sin_port);
+static void accept_loop(Server *server, void (*child_fn)(int, void *),
+                        void *child_ctx, const char *log_fmt) {
   if (listen(server->file_descriptor, SOMAXCONN) < 0) {
     perror("Could not listen on port!");
-    return false;
+    return;
   }
-
   signal(SIGCHLD, SIG_IGN);
-
   while (1) {
     struct sockaddr_in client_addr;
     socklen_t client_len = sizeof(client_addr);
-    int file_descriptor =
-        accept(server->file_descriptor, (struct sockaddr *)&client_addr,
-               &client_len);
-    if (file_descriptor < 0) {
+    int fd = accept(server->file_descriptor, (struct sockaddr *)&client_addr,
+                    &client_len);
+    if (fd < 0) {
       perror("Could not accept the connection");
       continue;
     }
-    log_message(LOG_LEVEL_INFO, "Received Connection");
+    log_message(LOG_LEVEL_INFO, "%s", log_fmt);
     pid_t pid = fork();
     if (pid == 0) {
       close(server->file_descriptor);
-      handler(file_descriptor);
-      close(file_descriptor);
+      child_fn(fd, child_ctx);
+      close(fd);
       _exit(0);
     }
-    close(file_descriptor);
+    close(fd);
   }
+}
+
+struct plain_ctx { void (*handler)(int); };
+
+static void plain_child_fn(int fd, void *ctx) {
+  ((struct plain_ctx *)ctx)->handler(fd);
+}
+
+bool server_listen(Server *server, void (*handler)(int file_descriptor)) {
+  log_message(LOG_LEVEL_INFO, "Start Listening on Port: %d",
+              ntohs(server->address.sin_port));
+  struct plain_ctx ctx = {handler};
+  accept_loop(server, plain_child_fn, &ctx, "Received Connection");
   return true;
 }
 
+void server_accept_loop(Server *server, void (*child_fn)(int, void *),
+                        void *child_ctx, const char *log_fmt) {
+  log_message(LOG_LEVEL_INFO, "Start TLS Listening on Port: %d",
+              ntohs(server->address.sin_port));
+  accept_loop(server, child_fn, child_ctx, log_fmt);
+}
+
 Client *client_create() {
   int file_descriptor = socket(AF_INET, SOCK_STREAM, 0);
   if (file_descriptor < 0) {
@@ -104,6 +127,8 @@ Client *client_create() {
   client->address.sin_family = AF_INET;
   client->address_length = sizeof(client->address);
   client->ssh_child_pid = -1;
+  client->ssl = NULL;
+  client->ssl_ctx = NULL;
   return client;
 }
 
@@ -124,6 +149,12 @@ bool client_connect(Client *client, char *host, int port) {
 }
 
 void client_disconnect(Client *client) {
+  if (client->ssl) {
+    SSL_shutdown(client->ssl);
+    SSL_free(client->ssl);
+    client->ssl = NULL;
+    io_set_ssl(NULL);
+  }
   close(client->file_descriptor);
   if (client->ssh_child_pid > 0) {
     int status;
@@ -133,7 +164,10 @@ void client_disconnect(Client *client) {
 }
 
 void client_delete(Client *client) {
-  if (client == NULL)
-    return;
+  if (client == NULL) return;
+  if (client->ssl_ctx) {
+    SSL_CTX_free(client->ssl_ctx);
+    client->ssl_ctx = NULL;
+  }
   free(client);
 }

src/shared/transport_tcp.h

@@ -9,6 +9,7 @@ typedef struct Server {
   struct sockaddr_in address;
   unsigned int address_length;
   int file_descriptor;
+  void *ssl_ctx;
 } Server;
 
 typedef struct Client {
@@ -16,10 +17,14 @@ typedef struct Client {
   unsigned int address_length;
   int file_descriptor;
   pid_t ssh_child_pid;
+  void *ssl;
+  void *ssl_ctx;
 } Client;
 
 Server *server_create(int port);
 bool server_listen(Server *server, void (*handler)(int file_descriptor));
+void server_accept_loop(Server *server, void (*child_fn)(int, void *),
+                        void *child_ctx, const char *log_fmt);
 void server_delete(Server **server);
 Client *client_create();
 bool client_connect(Client *client, char *host, int port);

src/shared/transport_tls.c

@@ -0,0 +1,162 @@
+#include "transport_tls.h"
+#include "log.h"
+#include "protocol.h"
+#include "transport_tcp.h"
+#include <arpa/inet.h>
+#include <openssl/err.h>
+#include <openssl/ssl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+bool tls_global_init(void) {
+#if OPENSSL_VERSION_NUMBER < 0x10100000L
+  SSL_library_init();
+  OpenSSL_add_all_algorithms();
+  SSL_load_error_strings();
+#endif
+  return true;
+}
+
+static void log_ssl_errors(void) {
+  unsigned long err;
+  char buf[256];
+  while ((err = ERR_get_error()) != 0) {
+    ERR_error_string_n(err, buf, sizeof(buf));
+    log_message(LOG_LEVEL_ERROR, "SSL error: %s", buf);
+  }
+}
+
+static SSL_CTX *create_ssl_ctx(bool is_server, const char *cert,
+                                const char *key, const char *ca_path) {
+  const SSL_METHOD *method =
+      is_server ? TLS_server_method() : TLS_client_method();
+  SSL_CTX *ctx = SSL_CTX_new(method);
+  if (!ctx) {
+    log_message(LOG_LEVEL_ERROR, "Unable to create SSL context");
+    log_ssl_errors();
+    return NULL;
+  }
+
+  SSL_CTX_set_min_proto_version(ctx, TLS1_2_VERSION);
+
+  if (cert && key) {
+    if (SSL_CTX_use_certificate_file(ctx, cert, SSL_FILETYPE_PEM) <= 0) {
+      log_message(LOG_LEVEL_ERROR, "Failed to load certificate: %s", cert);
+      log_ssl_errors();
+      SSL_CTX_free(ctx);
+      return NULL;
+    }
+    if (SSL_CTX_use_PrivateKey_file(ctx, key, SSL_FILETYPE_PEM) <= 0) {
+      log_message(LOG_LEVEL_ERROR, "Failed to load private key: %s", key);
+      log_ssl_errors();
+      SSL_CTX_free(ctx);
+      return NULL;
+    }
+    if (!SSL_CTX_check_private_key(ctx)) {
+      log_message(LOG_LEVEL_ERROR,
+                  "Private key does not match certificate");
+      SSL_CTX_free(ctx);
+      return NULL;
+    }
+  }
+
+  if (ca_path) {
+    if (!SSL_CTX_load_verify_locations(ctx, ca_path, NULL)) {
+      log_message(LOG_LEVEL_ERROR, "Failed to load CA: %s", ca_path);
+      log_ssl_errors();
+      SSL_CTX_free(ctx);
+      return NULL;
+    }
+    SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER, NULL);
+    SSL_CTX_set_verify_depth(ctx, 4);
+  }
+
+  return ctx;
+}
+
+static SSL *wrap_fd_with_ssl(int fd, SSL_CTX *ctx, bool is_server) {
+  SSL *ssl = SSL_new(ctx);
+  if (!ssl) {
+    log_message(LOG_LEVEL_ERROR, "Failed to create SSL object");
+    return NULL;
+  }
+  SSL_set_fd(ssl, fd);
+  int ret;
+  if (is_server)
+    ret = SSL_accept(ssl);
+  else
+    ret = SSL_connect(ssl);
+
+  if (ret <= 0) {
+    log_message(LOG_LEVEL_ERROR, "SSL %s failed",
+                is_server ? "accept" : "connect");
+    log_ssl_errors();
+    SSL_free(ssl);
+    return NULL;
+  }
+  return ssl;
+}
+
+bool server_create_tls(Server *server, const char *cert_path,
+                        const char *key_path, const char *ca_path) {
+  SSL_CTX *ctx = create_ssl_ctx(true, cert_path, key_path, ca_path);
+  if (!ctx) return false;
+  server->ssl_ctx = ctx;
+  return true;
+}
+
+struct tls_child_ctx {
+  void (*handler)(int);
+  SSL_CTX *ssl_ctx;
+};
+
+static void tls_child_fn(int fd, void *arg) {
+  struct tls_child_ctx *ctx = (struct tls_child_ctx *)arg;
+  SSL *ssl = wrap_fd_with_ssl(fd, ctx->ssl_ctx, true);
+  if (!ssl) return;
+  io_set_ssl(ssl);
+  ctx->handler(fd);
+  SSL_shutdown(ssl);
+  SSL_free(ssl);
+  io_set_ssl(NULL);
+}
+
+bool server_listen_tls(Server *server, void (*handler)(int file_descriptor)) {
+  struct tls_child_ctx ctx = {handler, (SSL_CTX *)server->ssl_ctx};
+  server_accept_loop(server, tls_child_fn, &ctx, "Received TLS Connection");
+  return true;
+}
+
+bool client_connect_tls(Client *client, char *host, int port,
+                         const char *cert_path, const char *key_path,
+                         const char *ca_path) {
+  client->address.sin_port = htons(port);
+  if (inet_pton(AF_INET, host, &client->address.sin_addr) <= 0) {
+    perror("Could not convert host address!");
+    return false;
+  }
+  if (connect(client->file_descriptor, (struct sockaddr *)&client->address,
+               client->address_length) < 0) {
+    perror("Could not connect to Server!");
+    return false;
+  }
+
+  SSL_CTX *ctx = create_ssl_ctx(false, cert_path, key_path, ca_path);
+  if (!ctx) return false;
+  client->ssl_ctx = ctx;
+
+  SSL *ssl = wrap_fd_with_ssl(client->file_descriptor, ctx, false);
+  if (!ssl) {
+    SSL_CTX_free(ctx);
+    client->ssl_ctx = NULL;
+    return false;
+  }
+  client->ssl = ssl;
+  io_set_ssl(ssl);
+  return true;
+}

src/shared/transport_tls.h

@@ -0,0 +1,16 @@
+#ifndef TRANSPORT_TLS_H
+#define TRANSPORT_TLS_H
+
+#include "transport_tcp.h"
+#include <stdbool.h>
+
+bool tls_global_init(void);
+
+bool server_create_tls(Server *server, const char *cert_path,
+                        const char *key_path, const char *ca_path);
+bool server_listen_tls(Server *server, void (*handler)(int file_descriptor));
+bool client_connect_tls(Client *client, char *host, int port,
+                         const char *cert_path, const char *key_path,
+                         const char *ca_path);
+
+#endif