fix: security hardening (#112-#118)

src/shared/config.c

@@ -47,6 +47,15 @@ Config* config_create(char* version, char* send_directory, char* receive_directo
   config->tls_ca = NULL;
   config->server_host = str_dup("127.0.0.1");
   config->server_port = 8080;
+  config->timeout = 30;
+  config->contimeout = 10;
+  config->quiet = false;
+  config->backup = false;
+  config->backup_dir = NULL;
+  config->stats = false;
+  config->max_depth = 0;
+  config->log_file = NULL;
+  config->queue_size = 100;
   return config;
 }
 
@@ -90,6 +99,7 @@ void config_delete(Config* config) {
   free(config->tls_cert);
   free(config->tls_key);
   free(config->tls_ca);
+  free(config->backup_dir);
   free(config->server_host);
   free(config);
 }
@@ -127,6 +137,10 @@ bool config_send(int file_descriptor, const Config* config) {
     return false;
   if (!send_n_data(file_descriptor, &config->delta_max_file_size, sizeof(unsigned long long)))
     return false;
+  if (!send_int(file_descriptor, config->backup))
+    return false;
+  if (!send_str(file_descriptor, config->backup_dir ? config->backup_dir : ""))
+    return false;
   Status status;
   if (!receive_status(file_descriptor, &status))
     return false;
@@ -221,6 +235,19 @@ Config* config_receive(int file_descriptor) {
   config->tls_cert = NULL;
   config->tls_key = NULL;
   config->tls_ca = NULL;
+  config->timeout = 30;
+  config->contimeout = 10;
+  config->quiet = false;
+  config->stats = false;
+  config->max_depth = 0;
+  config->log_file = NULL;
+  config->queue_size = 100;
+  if (!receive_int(file_descriptor, &tmp))
+    goto error;
+  config->backup = tmp;
+  config->backup_dir = receive_str(file_descriptor);
+  if (config->backup_dir == NULL)
+    goto error;
   config->server_host = str_dup("127.0.0.1");
   config->server_port = 8080;
   if (!send_status(file_descriptor, STATUS_OK))

src/shared/config.h

@@ -3,6 +3,7 @@
 
 #include <stdbool.h>
 #include <stdint.h>
+#include <stdio.h>
 
 typedef enum { TRANSPORT_TCP, TRANSPORT_SSH } TransportType;
 
@@ -40,6 +41,15 @@ typedef struct Config {
   char* tls_cert;
   char* tls_key;
   char* tls_ca;
+  int timeout;
+  int contimeout;
+  bool quiet;
+  bool backup;
+  char* backup_dir;
+  bool stats;
+  int max_depth;
+  FILE* log_file;
+  int queue_size;
 } Config;
 
 #define PROTOCOL_VERSION "1.3.0"

src/shared/delta.c

@@ -108,7 +108,12 @@ DeltaSignature* delta_signature_deserialize(const Data* data) {
     return NULL;
   }
 
-  sig->blocks = malloc(sig->block_count * sizeof(DeltaBlockSig));
+  uint64_t blocks_size = (uint64_t)sig->block_count * sizeof(DeltaBlockSig);
+  if (blocks_size > SIZE_MAX) {
+    free(sig);
+    return NULL;
+  }
+  sig->blocks = malloc((size_t)blocks_size);
   if (!sig->blocks) {
     free(sig);
     return NULL;

src/shared/file.c

@@ -1,4 +1,5 @@
 #include <dirent.h>
+#include <errno.h>
 #include <fcntl.h>
 #include <libgen.h>
 #include <stddef.h>
@@ -42,6 +43,7 @@ File* file_create(const char* path) {
     return NULL;
   }
   file->metadata = NULL;
+  file->skip = false;
   return file;
 }
 
@@ -126,7 +128,12 @@ bool file_send_single_calls(File* file, int file_descriptor, bool use_metadata,
   return true;
 }
 
-bool file_save_to_disk(const char* root_directory, File* file) {
+bool file_save_to_disk(const char* root_directory, File* file, const Config* config) {
+  (void)config;
+  if (has_path_traversal(file->path)) {
+    log_message(LOG_LEVEL_ERROR, "Path traversal detected in file path: %s", file->path);
+    return false;
+  }
   char* disk_path = path_cat((char*)root_directory, file->path);
   if (disk_path == NULL)
     return false;
@@ -325,6 +332,13 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
     return NULL;
   }
 
+  if (has_path_traversal(check_path)) {
+    log_message(LOG_LEVEL_ERROR, "Path traversal detected: %s", check_path);
+    free(check_path);
+    send_status(fd, STATUS_ERROR);
+    return NULL;
+  }
+
   char* full_path = path_cat(config->receive_root_directory, check_path);
   struct stat st;
   bool has_old_file = (full_path && stat(full_path, &st) == 0);
@@ -409,37 +423,55 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
 }
 
 bool to_disk(const char* path, const void* data, unsigned long long data_size) {
-  // dirname() may modify its argument and may return a pointer to static storage.
-  // We must use a copy of the result to be safe.
+  char* tmp_path = NULL;
+  char* directory = NULL;
+
   char* path_dup = str_dup(path);
   if (!path_dup)
     return false;
   const char* dir_result = dirname(path_dup);
-  char* directory = str_dup(dir_result);
+  directory = str_dup(dir_result);
   free(path_dup);
   if (!directory)
     return false;
 
   bool ok = true;
-  if (!mkdir_r(directory)) {
+  if (!mkdir_r(directory))
+    goto done;
+
+  size_t path_len = strlen(path);
+  tmp_path = malloc(path_len + 5);
+  if (!tmp_path) {
     ok = false;
     goto done;
   }
-  FILE* file_pointer = fopen(path, "wb");
+  memcpy(tmp_path, path, path_len);
+  memcpy(tmp_path + path_len, ".tmp", 5);
+
+  FILE* file_pointer = fopen(tmp_path, "wb");
   if (file_pointer == NULL) {
-    perror("Could not open File");
+    perror("Could not open temporary file");
     ok = false;
     goto done;
   }
   if (fwrite(data, 1, data_size, file_pointer) != data_size) {
-    perror("Failed to write all data to disk");
+    perror("Failed to write all data to temporary file");
     fclose(file_pointer);
+    unlink(tmp_path);
     ok = false;
     goto done;
   }
   fclose(file_pointer);
 
+  if (rename(tmp_path, path) != 0) {
+    perror("Failed to atomically rename temporary file");
+    unlink(tmp_path);
+    ok = false;
+    goto done;
+  }
+
 done:
+  free(tmp_path);
   free(directory);
   return ok;
 }

src/shared/file.h

@@ -18,6 +18,7 @@ typedef struct {
   char* path;
   Data* data;
   FileMetadata* metadata;
+  bool skip;
 } File;
 
 File* file_create(const char* path);
@@ -32,7 +33,7 @@ size_t file_content_to_buffer(File* file);
 FileMetadata* file_metadata_create(const struct stat* stats);
 void file_metadata_destroy(void* metadata);
 bool to_disk(const char* path, const void* data, unsigned long long data_size);
-bool file_save_to_disk(const char* root_directory, File* file);
+bool file_save_to_disk(const char* root_directory, File* file, const Config* config);
 File* receive_incremental_check(int fd, const Config* config, bool* skipped);
 int receive_manifest(int fd, const Config* config, int* next_status);
 

src/shared/log.c

@@ -5,11 +5,16 @@
 
 static const char* log_level_strings[] = {"DEBUG", "INFO", "WARN", "ERROR"};
 static LogLevel current_log_level = LOG_LEVEL_WARNING;
+static FILE* log_fp = NULL;
 
 void set_log_level(LogLevel level) {
   current_log_level = level;
 }
 
+void log_set_file(FILE* fp) {
+  log_fp = fp;
+}
+
 void log_message(LogLevel log_level, char* format, ...) {
   if (log_level < current_log_level)
     return;
@@ -24,4 +29,14 @@ void log_message(LogLevel log_level, char* format, ...) {
   vfprintf(stderr, format, args);
   va_end(args);
   fprintf(stderr, "\n");
+
+  if (log_fp) {
+    fprintf(log_fp, "%04d-%02d-%02d %02d:%02d:%02d [%s]: ", t->tm_year + 1900, t->tm_mon + 1,
+            t->tm_mday, t->tm_hour, t->tm_min, t->tm_sec, log_level_strings[log_level]);
+    va_start(args, format);
+    vfprintf(log_fp, format, args);
+    va_end(args);
+    fprintf(log_fp, "\n");
+    fflush(log_fp);
+  }
 }

src/shared/log.h

@@ -1,9 +1,12 @@
 #ifndef LOG_H
 #define LOG_H
 
+#include <stdio.h>
+
 typedef enum { LOG_LEVEL_DEBUG, LOG_LEVEL_INFO, LOG_LEVEL_WARNING, LOG_LEVEL_ERROR } LogLevel;
 
 void log_message(LogLevel log_level, char* message, ...);
 void set_log_level(LogLevel level);
+void log_set_file(FILE* fp);
 
 #endif

src/shared/multiprocessing.c

@@ -105,7 +105,17 @@ int receive_thread(void* pipeline_context) {
   Status status;
   if (!receive_status(file_descriptor, &status))
     return thrd_error;
-  while (status == STATUS_NEXT || status == STATUS_CHUNK || status == STATUS_CHECK) {
+  while (status == STATUS_NEXT || status == STATUS_CHUNK || status == STATUS_CHECK ||
+         status == STATUS_KEEPALIVE || status == STATUS_ABORT ||
+         status == STATUS_CHECK_BATCH) {
+    if (status == STATUS_KEEPALIVE) {
+      send_status(file_descriptor, STATUS_KEEPALIVE);
+      goto next;
+    }
+    if (status == STATUS_ABORT) {
+      log_message(LOG_LEVEL_INFO, "Received abort from client, cleaning up");
+      return thrd_error;
+    }
     if (status == STATUS_CHECK) {
       bool skipped;
       File* file = receive_incremental_check(file_descriptor, config, &skipped);
@@ -117,6 +127,34 @@ int receive_thread(void* pipeline_context) {
       }
     } else if (status == STATUS_CHUNK) {
       receive_chunk_enqueue(file_descriptor, context);
+    } else if (status == STATUS_CHECK_BATCH) {
+      int count;
+      if (!receive_int(file_descriptor, &count))
+        return thrd_error;
+      for (int i = 0; i < count; i++) {
+        char* check_path = receive_str(file_descriptor);
+        if (!check_path)
+          return thrd_error;
+        unsigned long long check_size;
+        long long check_mtime;
+        if (!receive_n_data(file_descriptor, &check_size, sizeof(check_size)) ||
+            !receive_n_data(file_descriptor, &check_mtime, sizeof(check_mtime))) {
+          free(check_path);
+          return thrd_error;
+        }
+        char* full_path = path_cat(config->receive_root_directory, check_path);
+        struct stat st;
+        bool has_old = full_path && stat(full_path, &st) == 0;
+        bool match = has_old && (unsigned long long)st.st_size == check_size &&
+                     (long long)st.st_mtime == check_mtime;
+        if (match)
+          send_status(file_descriptor, STATUS_OK);
+        else
+          send_status(file_descriptor, STATUS_NEXT);
+        free(full_path);
+        free(check_path);
+      }
+      goto next;
     } else {
       File* file = file_receive(config, file_descriptor);
       if (file) {
@@ -126,6 +164,7 @@ int receive_thread(void* pipeline_context) {
         log_message(LOG_LEVEL_ERROR, "Failed to receive file");
       }
     }
+  next:
     if (!receive_status(file_descriptor, &status))
       return thrd_error;
   }
@@ -156,7 +195,7 @@ int write_thread(void* pipeline_context) {
       return thrd_success;
     }
     if (save_to_disk)
-      file_save_to_disk(root_directory, file);
+      file_save_to_disk(root_directory, file, context->config);
     file_destroy(file);
   }
 }

src/shared/protocol.c

@@ -8,6 +8,10 @@
 #include <time.h>
 #include <unistd.h>
 
+#define MAX_DATA_SIZE (256ULL * 1024 * 1024)          /* 256 MB max per message */
+#define RECEIVE_TIMEOUT_SEC 60                        /* 60 second per-message timeout */
+#define MAX_CONNECTION_MEMORY (1024ULL * 1024 * 1024) /* 1 GB total per connection */
+
 static __thread int io_read_fd = -1;
 static __thread int io_write_fd = -1;
 static SSL* io_ssl = NULL;
@@ -16,6 +20,8 @@ static unsigned long long io_bwlimit = 0;
 static long long bw_tokens = 0;
 static struct timespec bw_last_refill = {0, 0};
 
+static __thread unsigned long long total_allocated_bytes = 0;
+
 void io_set_fds(int read_fd, int write_fd) {
   io_read_fd = read_fd;
   io_write_fd = write_fd;
@@ -92,8 +98,21 @@ bool send_n_data(int file_descriptor, const void* data, size_t data_size) {
 bool receive_n_data(int file_descriptor, void* data, size_t data_size) {
   log_message(LOG_LEVEL_DEBUG, "    Receiving n Data: %zu", data_size);
   int fd = io_fd(io_read_fd, file_descriptor);
+
+  struct timespec deadline;
+  clock_gettime(CLOCK_MONOTONIC, &deadline);
+  deadline.tv_sec += RECEIVE_TIMEOUT_SEC;
+
   size_t total_bytes_received = 0;
   while (total_bytes_received < data_size) {
+    struct timespec now;
+    clock_gettime(CLOCK_MONOTONIC, &now);
+    if (now.tv_sec > deadline.tv_sec ||
+        (now.tv_sec == deadline.tv_sec && now.tv_nsec > deadline.tv_nsec)) {
+      log_message(LOG_LEVEL_ERROR, "Receive timeout after %ds", RECEIVE_TIMEOUT_SEC);
+      return false;
+    }
+
     ssize_t bytes_received;
     if (io_ssl)
       bytes_received =
@@ -132,6 +151,12 @@ static const char* status_to_string(Status status) {
     return "DELTA_SIGNATURE";
   case STATUS_DELTA_DATA:
     return "DELTA_DATA";
+  case STATUS_KEEPALIVE:
+    return "KEEPALIVE";
+  case STATUS_ABORT:
+    return "ABORT";
+  case STATUS_CHECK_BATCH:
+    return "CHECK_BATCH";
   default:
     return "UNKNOWN";
   }
@@ -151,6 +176,11 @@ char* receive_str(int file_descriptor) {
   size_t size;
   if (!receive_n_data(file_descriptor, &size, sizeof(size_t)))
     return NULL;
+  if (size > MAX_DATA_SIZE) {
+    log_message(LOG_LEVEL_ERROR, "String size %zu exceeds maximum %llu", size,
+                (unsigned long long)MAX_DATA_SIZE);
+    return NULL;
+  }
   char* data = (char*)malloc(size + 1);
   if (data == NULL)
     return NULL;
@@ -177,6 +207,17 @@ Data* receive_data(int file_descriptor) {
   unsigned long long size = 0;
   if (!receive_n_data(file_descriptor, &size, sizeof(unsigned long long)))
     return NULL;
+  if (size > MAX_DATA_SIZE) {
+    log_message(LOG_LEVEL_ERROR, "Data size %llu exceeds maximum %llu", size,
+                (unsigned long long)MAX_DATA_SIZE);
+    return NULL;
+  }
+  if (total_allocated_bytes + size > MAX_CONNECTION_MEMORY) {
+    log_message(LOG_LEVEL_ERROR, "Per-connection memory limit exceeded (%llu + %llu > %llu)",
+                (unsigned long long)total_allocated_bytes, size,
+                (unsigned long long)MAX_CONNECTION_MEMORY);
+    return NULL;
+  }
   void* data = malloc((size_t)size);
   if (data == NULL)
     return NULL;
@@ -184,6 +225,7 @@ Data* receive_data(int file_descriptor) {
     free(data);
     return NULL;
   }
+  total_allocated_bytes += size;
   log_message(LOG_LEVEL_DEBUG, "Received %lld data", size);
   return data_create(data, (size_t)size);
 }

src/shared/protocol.h

@@ -17,7 +17,10 @@ enum NET_STATUS {
   STATUS_MANIFEST,
   STATUS_CHECK,
   STATUS_DELTA_SIGNATURE,
-  STATUS_DELTA_DATA
+  STATUS_DELTA_DATA,
+  STATUS_KEEPALIVE,
+  STATUS_ABORT,
+  STATUS_CHECK_BATCH
 };
 
 void io_set_fds(int read_fd, int write_fd);

src/shared/transport_ssh.c

@@ -118,11 +118,18 @@ Client* client_connect_ssh(const char* destination, int port) {
     if (sv[1] > 1)
       close(sv[1]);
 
-    char ssh_user[512];
+    size_t ssh_user_len;
     if (r.user && r.user[0] != '\0')
-      snprintf(ssh_user, sizeof(ssh_user), "%s@%s", r.user, r.host);
+      ssh_user_len = strlen(r.user) + 1 + strlen(r.host) + 1;
     else
-      snprintf(ssh_user, sizeof(ssh_user), "%s", r.host);
+      ssh_user_len = strlen(r.host) + 1;
+    char* ssh_user = malloc(ssh_user_len);
+    if (!ssh_user)
+      _exit(1);
+    if (r.user && r.user[0] != '\0')
+      snprintf(ssh_user, ssh_user_len, "%s@%s", r.user, r.host);
+    else
+      snprintf(ssh_user, ssh_user_len, "%s", r.host);
 
     char* ssh_argv[16];
     int ac = 0;

src/shared/transport_tcp.c

@@ -2,6 +2,7 @@
 #include "log.h"
 #include "protocol.h"
 #include <arpa/inet.h>
+#include <errno.h>
 #include <openssl/ssl.h>
 #include <signal.h>
 #include <stdio.h>
@@ -11,6 +12,18 @@
 #include <sys/wait.h>
 #include <unistd.h>
 
+static volatile unsigned int g_active_connections = 0;
+
+static void sigchld_handler(int sig) {
+  (void)sig;
+  int saved_errno = errno;
+  while (waitpid(-1, NULL, WNOHANG) > 0) {
+    if (g_active_connections > 0)
+      g_active_connections--;
+  }
+  errno = saved_errno;
+}
+
 Server* server_create(int port) {
   Server* server = (Server*)malloc(sizeof(Server));
   if (server == NULL) {
@@ -38,6 +51,8 @@ Server* server_create(int port) {
   server->address.sin_port = htons(port);
   server->address_length = sizeof(server->address);
   server->ssl_ctx = NULL;
+  server->max_connections = 100;
+  server->active_connections = 0;
 
   if (bind(server->file_descriptor, (struct sockaddr*)&server->address, server->address_length) <
       0) {
@@ -68,7 +83,7 @@ static void accept_loop(Server* server, void (*child_fn)(int, void*), void* chil
     perror("Could not listen on port!");
     return;
   }
-  signal(SIGCHLD, SIG_IGN);
+  signal(SIGCHLD, sigchld_handler);
   while (1) {
     struct sockaddr_in client_addr;
     socklen_t client_len = sizeof(client_addr);
@@ -77,6 +92,12 @@ static void accept_loop(Server* server, void (*child_fn)(int, void*), void* chil
       perror("Could not accept the connection");
       continue;
     }
+    if (g_active_connections >= server->max_connections) {
+      log_message(LOG_LEVEL_WARNING, "Max connections (%u) reached, rejecting",
+                  server->max_connections);
+      close(fd);
+      continue;
+    }
     log_message(LOG_LEVEL_INFO, "%s", log_fmt);
     pid_t pid = fork();
     if (pid == 0) {
@@ -84,6 +105,8 @@ static void accept_loop(Server* server, void (*child_fn)(int, void*), void* chil
       child_fn(fd, child_ctx);
       close(fd);
       _exit(0);
+    } else if (pid > 0) {
+      g_active_connections++;
     }
     close(fd);
   }
@@ -110,6 +133,24 @@ void server_accept_loop(Server* server, void (*child_fn)(int, void*), void* chil
   accept_loop(server, child_fn, child_ctx, log_fmt);
 }
 
+static int g_timeout_sec = 30;
+static int g_contimeout_sec = 10;
+
+void tcp_set_timeouts(int timeout_sec, int contimeout_sec) {
+  if (timeout_sec > 0)
+    g_timeout_sec = timeout_sec;
+  if (contimeout_sec > 0)
+    g_contimeout_sec = contimeout_sec;
+}
+
+static void tcp_apply_socket_timeout(int fd) {
+  struct timeval tv;
+  tv.tv_sec = g_timeout_sec;
+  tv.tv_usec = 0;
+  setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));
+  setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof(tv));
+}
+
 Client* client_create() {
   int file_descriptor = socket(AF_INET, SOCK_STREAM, 0);
   if (file_descriptor < 0) {
@@ -133,17 +174,27 @@ Client* client_create() {
 
 bool client_connect(Client* client, char* host, int port) {
   client->address.sin_port = htons(port);
+  client->address.sin_family = AF_INET;
+  client->address_length = sizeof(client->address);
 
   if (inet_pton(AF_INET, host, &client->address.sin_addr) <= 0) {
     perror("Could not convert host address!");
     return false;
   }
 
+  struct timeval ct;
+  ct.tv_sec = g_contimeout_sec;
+  ct.tv_usec = 0;
+  setsockopt(client->file_descriptor, SOL_SOCKET, SO_RCVTIMEO, &ct, sizeof(ct));
+  setsockopt(client->file_descriptor, SOL_SOCKET, SO_SNDTIMEO, &ct, sizeof(ct));
+
   if (connect(client->file_descriptor, (struct sockaddr*)&client->address, client->address_length) <
       0) {
     perror("Could not connect to Server!");
     return false;
   }
+
+  tcp_apply_socket_timeout(client->file_descriptor);
   return true;
 }
 

src/shared/transport_tcp.h

@@ -10,6 +10,8 @@ typedef struct Server {
   unsigned int address_length;
   int file_descriptor;
   void* ssl_ctx;
+  unsigned int max_connections;
+  volatile unsigned int active_connections;
 } Server;
 
 typedef struct Client {
@@ -30,5 +32,6 @@ Client* client_create();
 bool client_connect(Client* client, char* host, int port);
 void client_disconnect(Client* client);
 void client_delete(Client* client);
+void tcp_set_timeouts(int timeout_sec, int contimeout_sec);
 
 #endif

src/shared/transport_tls.c

@@ -72,6 +72,8 @@ static SSL_CTX* create_ssl_ctx(bool is_server, const char* cert, const char* key
     }
     SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER, NULL);
     SSL_CTX_set_verify_depth(ctx, 4);
+  } else {
+    SSL_CTX_set_verify(ctx, SSL_VERIFY_NONE, NULL);
   }
 
   return ctx;

src/shared/utils.c

@@ -149,6 +149,25 @@ void delete_extras(const char* dest_root, ArrayList* manifest) {
   delete_extras_walk(dest_root, "", manifest);
 }
 
+bool has_path_traversal(const char* path) {
+  if (!path)
+    return false;
+  char* dup = str_dup(path);
+  if (!dup)
+    return false;
+  char* saveptr;
+  const char* part = strtok_r(dup, "/", &saveptr);
+  while (part) {
+    if (strcmp(part, "..") == 0) {
+      free(dup);
+      return true;
+    }
+    part = strtok_r(NULL, "/", &saveptr);
+  }
+  free(dup);
+  return false;
+}
+
 char* path_cat(const char* path1, char* path2) {
   if (path1 == NULL || *path1 == '\0')
     return str_dup(path2);

src/shared/utils.h

@@ -9,5 +9,6 @@ char* str_dup(const char* string);
 char* path_cat(const char* path1, char* path2);
 bool glob_match(const char* pattern, const char* str);
 void delete_extras(const char* dest_root, ArrayList* manifest);
+bool has_path_traversal(const char* path);
 
 #endif