fix: close remaining PR review gaps

2026-08-16 09:35:26 +02:00
parent 78876b110e
commit d102622e28
27 changed files with 609 additions and 538 deletions
@@ -459,7 +459,6 @@ int main(int argc, char* argv[]) {
  parse_environment(&env_source, &env_dest, &save_to_disk);

  int exit_code = 0;
-  bool config_owned_by_pipeline = false;
  Config* config = config_create();
  if (!config) {
    fprintf(stderr, "Error: failed to allocate config\n");
@@ -542,17 +541,13 @@ int main(int argc, char* argv[]) {

  /* Execute transfer */
  if (config->use_multithreading) {
-    config_owned_by_pipeline = true;
-    exit_code = send_files_multithreaded(config);
+    exit_code = send_files_multithreaded(&config);
  } else {
    exit_code = send_files(config);
  }

 cleanup:
  if (config) {
-    if (config->log_file)
-      fclose(config->log_file);
-    if (!config_owned_by_pipeline)
    config_delete(config);
  }
  return exit_code;
@@ -70,6 +70,8 @@ static int send_dry_run_manifest(Config* config) {

 /* Send the delete manifest (list of files) to the server. Returns 0 on success, -1 on failure. */
 static int send_delete_manifest(int fd, ArrayList* manifest) {
+  if (!manifest)
+    return -1;
  if (!send_status(fd, STATUS_MANIFEST))
    return -1;
  if (!send_int(fd, manifest->size))
@@ -111,17 +113,22 @@ static int incremental_check(Client* client, File* file, const Config* config,
    return 1;
  if (s == STATUS_DELTA_SIGNATURE) {
    Data* sig_data = receive_data(client->file_descriptor);
-    if (!sig_data)
+    if (!sig_data) {
+      send_status(client->file_descriptor, STATUS_ERROR);
      return -1;
+    }
    DeltaSignature* sig = delta_signature_deserialize(sig_data);
    data_destroy(sig_data);
-    if (!sig)
+    if (!sig) {
+      send_status(client->file_descriptor, STATUS_ERROR);
      return -1;
+    }
    *out_sig = sig;
    return 2;
  }
  if (s != STATUS_NEXT) {
    log_message(LOG_LEVEL_ERROR, "Unexpected server status");
+    send_status(client->file_descriptor, STATUS_ERROR);
    return -1;
  }
  return 0;
@@ -129,8 +136,10 @@ static int incremental_check(Client* client, File* file, const Config* config,

 static int send_delta(Client* client, File* file, DeltaSignature* sig, Config* config) {
  Delta* delta = delta_compute(file->data->data, file->data->size, sig, config->delta_block_size);
+  /* The receiver is blocked after sending the signature.  Every local
+     fallback therefore needs the explicit NEXT response before full data. */
  if (!delta)
-    return 1;
+    return send_status(client->file_descriptor, STATUS_NEXT) ? 1 : -1;

  if (!delta_is_worthwhile(delta, file->data->size)) {
    delta_destroy(delta);
@@ -142,14 +151,14 @@ static int send_delta(Client* client, File* file, DeltaSignature* sig, Config* c
  Data* delta_data = delta_serialize(delta);
  delta_destroy(delta);
  if (!delta_data)
-    return -1;
+    return send_status(client->file_descriptor, STATUS_NEXT) ? 1 : -1;

  Data* to_send = delta_data;
  if (config->use_compression) {
    to_send = data_compress(delta_data, config->compression_level);
    data_destroy(delta_data);
    if (!to_send)
-      return -1;
+      return send_status(client->file_descriptor, STATUS_NEXT) ? 1 : -1;
  }

  bool ok = send_status(client->file_descriptor, STATUS_DELTA_DATA) &&
@@ -279,7 +288,8 @@ int send_chunk(Client* client, Chunk* chunk, Config* config) {
    if (f == NULL)
      continue;
    bool stream = f->data->data == NULL && f->data->size > 0;
-    bool use_sendfile = (config->use_sendfile && !config->use_compression) || stream;
+    bool use_sendfile =
+        (config->use_sendfile && !config->use_compression) || (stream && !config->use_compression);
    int rc = send_single_file(client, f, config, config->use_incremental, use_sendfile);
    if (rc == 1)
      continue;
@@ -478,7 +488,7 @@ static int load_files_multithreaded(void* pipeline_context) {
    if (!context->config->use_sendfile) {
      for (int i = 0; i < chunk->element_count; i++) {
        File* f = chunk->items[i];
-        if (f->data->size > STREAM_THRESHOLD)
+        if (f->data->size > STREAM_THRESHOLD && !context->config->use_compression)
          continue;
        if (!file_load_data(f)) {
          log_message(LOG_LEVEL_ERROR, "Failed to load file data, skipping");
@@ -630,7 +640,7 @@ int send_files(Config* config) {
    if (!config->use_sendfile) {
      for (int i = 0; i < current_chunk->element_count; i++) {
        File* f = current_chunk->items[i];
-        if (f->data->size > STREAM_THRESHOLD)
+        if (f->data->size > STREAM_THRESHOLD && !config->use_compression)
          continue;
        if (!file_load_data(f)) {
          log_message(LOG_LEVEL_ERROR, "Failed to load file data");
@@ -697,7 +707,10 @@ send_fail:
  return 1;
 }

-int send_files_multithreaded(Config* config) {
+int send_files_multithreaded(Config** config_ptr) {
+  if (!config_ptr || !*config_ptr)
+    return 1;
+  Config* config = *config_ptr;
  if (config->dry_run)
    return send_dry_run_manifest(config);

@@ -728,8 +741,13 @@ int send_files_multithreaded(Config* config) {
    queue_destroy(q2);
    return 1;
  }
+  *config_ptr = NULL; /* context now owns config through all remaining paths */
  if (config->use_delete)
    context->manifest = array_list_create(free);
+  if (config->use_delete && !context->manifest) {
+    pipeline_context_sender_destroy(context);
+    return 1;
+  }

  thrd_t scanner, loader, sender;
  bool scanner_created = false;
@@ -7,6 +7,7 @@

 int send_chunk(Client* client, Chunk* chunk, Config* config);
 int send_files(Config* config);
-int send_files_multithreaded(Config* config);
+/* Takes ownership only when *config is set to NULL on return. */
+int send_files_multithreaded(Config** config);

 #endif
@@ -465,8 +465,10 @@ ParallelScanner* parallel_scanner_create(char* root_directory, bool use_metadata
    if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
      continue;
    char* cur_path = path_cat(root_directory, entry->d_name);
-    if (!cur_path)
+    if (!cur_path) {
+      ps->failed = true;
      continue;
+    }
    struct stat lstats;
    if (lstat(cur_path, &lstats) != 0) {
      free(cur_path);
@@ -36,8 +36,10 @@ static bool tls_client_identity_allowed(SSL* ssl) {
  char common_name[256];
  int length = X509_NAME_get_text_by_NID(X509_get_subject_name(certificate), NID_commonName,
                                         common_name, sizeof(common_name));
-  bool allowed = length >= 0 && (size_t)length < sizeof(common_name) &&
-                 strcmp(common_name, required_client_cn) == 0;
+  size_t required_length = strlen(required_client_cn);
+  bool allowed = length >= 0 && (size_t)length == required_length &&
+                 required_length < sizeof(common_name) &&
+                 memcmp(common_name, required_client_cn, required_length) == 0;
  X509_free(certificate);
  return allowed;
 }
@@ -54,19 +56,44 @@ static bool valid_batch_path(const char* path) {

 static bool __attribute__((unused)) configure_authorization(const char* root) {
  char resolved[PATH_MAX];
-  if (!root || !realpath(root, resolved))
+  if (!root) {
+    file_set_authorized_root(-1, NULL);
+    utils_set_authorized_root(-1, NULL);
    return false;
+  }
+  int root_fd = open(root, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
+  if (root_fd < 0) {
+    file_set_authorized_root(-1, NULL);
+    utils_set_authorized_root(-1, NULL);
+    return false;
+  }
+  char fd_path[64];
+  int fd_path_length = snprintf(fd_path, sizeof(fd_path), "/proc/self/fd/%d", root_fd);
+  if (fd_path_length < 0 || (size_t)fd_path_length >= sizeof(fd_path) ||
+      !realpath(fd_path, resolved)) {
+    close(root_fd);
+    file_set_authorized_root(-1, NULL);
+    utils_set_authorized_root(-1, NULL);
+    return false;
+  }
  authorized_root = str_dup(resolved);
-  if (!authorized_root)
+  if (!authorized_root) {
+    close(root_fd);
+    file_set_authorized_root(-1, NULL);
+    utils_set_authorized_root(-1, NULL);
    return false;
-  authorized_root_fd = open(resolved, O_RDONLY | O_DIRECTORY | O_CLOEXEC);
-  if (authorized_root_fd < 0) {
+  }
+  authorized_root_fd = root_fd;
+  if (!file_set_authorized_root(authorized_root_fd, authorized_root) ||
+      !utils_set_authorized_root(authorized_root_fd, authorized_root)) {
+    file_set_authorized_root(-1, NULL);
+    utils_set_authorized_root(-1, NULL);
+    close(authorized_root_fd);
+    authorized_root_fd = -1;
    free(authorized_root);
    authorized_root = NULL;
    return false;
  }
-  file_set_authorized_root(authorized_root_fd, authorized_root);
-  utils_set_authorized_root(authorized_root_fd, authorized_root);
  return true;
 }

@@ -138,6 +165,11 @@ int receive_files(Config* config, int fd) {
        }
        struct stat st;
        char* full_path = path_cat(config->receive_root_directory, check_path);
+        if (!full_path) {
+          free(check_path);
+          send_status(fd, STATUS_ERROR);
+          return -1;
+        }
        bool has_old = full_path && file_stat_secure(full_path, &st);
        bool match = has_old && (unsigned long long)st.st_size == check_size &&
                     (long long)st.st_mtime == check_mtime;
@@ -171,9 +203,10 @@ int receive_files(Config* config, int fd) {
  }

  if (status == STATUS_MANIFEST) {
-    if (receive_manifest(fd, config, &status) != 0)
+    if (receive_manifest(fd, config, &status) != 0) {
      return -1;
    }
+  }
  if (status != STATUS_FINISHED) {
    log_message(LOG_LEVEL_ERROR, "Did not receive FINISHED Status");
    send_status(fd, STATUS_ERROR);
@@ -209,24 +242,24 @@ void handler(int file_descriptor) {
    close(file_descriptor);
    return;
  }
-  char resolved_destination[PATH_MAX];
-  char* canonical_destination = realpath(config->receive_root_directory, NULL);
-  const char* destination =
-      canonical_destination ? canonical_destination : config->receive_root_directory;
-  if (has_path_traversal(destination) || !path_is_within(authorized_root, destination)) {
+  char* destination = config->receive_root_directory;
+  char* joined_destination = NULL;
+  if (destination && destination[0] != '/')
+    joined_destination = path_cat(authorized_root, destination);
+  if (joined_destination)
+    destination = joined_destination;
+  if (!destination || has_path_traversal(destination) ||
+      !path_is_within(authorized_root, destination)) {
    log_message(LOG_LEVEL_ERROR, "Rejected destination outside authorized root");
-    free(canonical_destination);
+    free(joined_destination);
    config_delete(config);
    close(file_descriptor);
    return;
  }
-  if (canonical_destination)
-    snprintf(resolved_destination, sizeof(resolved_destination), "%s", canonical_destination);
-  else
-    snprintf(resolved_destination, sizeof(resolved_destination), "%s", destination);
-  free(canonical_destination);
+  if (joined_destination) {
    free(config->receive_root_directory);
-  config->receive_root_directory = str_dup(resolved_destination);
+    config->receive_root_directory = joined_destination;
+  }
  if (!config->receive_root_directory) {
    config_delete(config);
    close(file_descriptor);
@@ -13,6 +13,7 @@
 #include "log.h"
 #include "metadata.h"
 #include "protocol.h"
+#include "utils.h"

 /* Maximum individual file data size within a chunk (64 MB) */
 #define MAX_FILE_DATA_SIZE (64ULL * 1024 * 1024)
@@ -82,8 +83,14 @@ static unsigned long long per_file_serialize_size(File* file, bool use_metadata)
 }

 Data* chunk_serialize(Chunk* chunk, bool use_metadata) {
+  if (!chunk || chunk->element_count < 0 || (chunk->element_count > 0 && chunk->items == NULL))
+    return NULL;
  unsigned long long data_size = 0;
  for (int i = 0; i < chunk->element_count; i++) {
+    if (!chunk->items[i] || !chunk->items[i]->path || !chunk->items[i]->data ||
+        (chunk->items[i]->data->size > 0 && !chunk->items[i]->data->data) ||
+        chunk->items[i]->path[0] == '\0' || has_path_traversal(chunk->items[i]->path))
+      return NULL;
    unsigned long long file_size = per_file_serialize_size(chunk->items[i], use_metadata);
    if (file_size == 0 || file_size > ULLONG_MAX - data_size || data_size + file_size > SIZE_MAX)
      return NULL;
@@ -116,6 +123,8 @@ Data* chunk_serialize(Chunk* chunk, bool use_metadata) {
 }

 Chunk* chunk_deserialize(Data* data, bool use_metadata) {
+  if (!data || (!data->data && data->size != 0))
+    return NULL;
  ArrayList* files = array_list_create(file_destroy);
  if (files == NULL)
    return NULL;
@@ -165,6 +174,12 @@ Chunk* chunk_deserialize(Data* data, bool use_metadata) {
    data_pointer += path_len;
    remaining_size -= path_len;

+    if (path_len == 0 || has_path_traversal(path)) {
+      free(path);
+      array_list_delete(files);
+      return NULL;
+    }
+
    File* file = file_create(path);
    free(path);
    if (file == NULL) {
@@ -285,14 +300,14 @@ Data* chunk_compress(Chunk* chunk, int compression_level, bool use_metadata) {
 }

 Chunk* receive_chunk_data(int fd, const Config* config) {
-  Data* chunk_data = receive_data(fd);
+  Data* chunk_data = receive_data_limited(fd, MAX_CHUNK_SIZE);
  if (chunk_data == NULL) {
    log_message(LOG_LEVEL_ERROR, "Failed to receive chunk data");
    return NULL;
  }
  Data* data_to_process = chunk_data;
  if (config->use_compression) {
-    data_to_process = data_decompress(chunk_data);
+    data_to_process = data_decompress_limited(chunk_data, MAX_CHUNK_SIZE);
    data_destroy(chunk_data);
    if (data_to_process == NULL) {
      log_message(LOG_LEVEL_ERROR, "Failed to decompress chunk");
@@ -2,6 +2,8 @@
 #include "data.h"
 #include "log.h"
 #include <stdlib.h>
+#include <limits.h>
+#include <stdint.h>
 #include <string.h>
 #include <strings.h>
 #include <zstd.h>
@@ -69,7 +71,10 @@ Data* data_compress(Data* data_to_compress, int compression_level) {
  return compressed_data;
 }

-Data* data_decompress(Data* compressed_data) {
+Data* data_decompress_limited(Data* compressed_data, size_t maximum_size) {
+  if (!compressed_data || (!compressed_data->data && compressed_data->size != 0) ||
+      maximum_size == 0)
+    return NULL;
  log_message(LOG_LEVEL_DEBUG, "Start to decompress data");
  unsigned long long dst_size =
      ZSTD_getFrameContentSize(compressed_data->data, compressed_data->size);
@@ -82,15 +87,16 @@ Data* data_decompress(Data* compressed_data) {
  // ZSTD_CONTENTSIZE_UNKNOWN (~2^64) can cause massive allocation;
  // fall back to a conservative estimate (3x compressed size) when unknown.
  if (dst_size == ZSTD_CONTENTSIZE_UNKNOWN) {
+    if (compressed_data->size > ULLONG_MAX / 3)
+      return NULL;
    dst_size = compressed_data->size * 3;
    if (dst_size < INITIAL_DECOMPRESS_BUF_SIZE)
      dst_size = INITIAL_DECOMPRESS_BUF_SIZE;
-    if (dst_size > MAX_DECOMPRESSED_SIZE)
-      dst_size = MAX_DECOMPRESSED_SIZE;
  }
-  if (dst_size > MAX_DECOMPRESSED_SIZE) {
-    log_message(LOG_LEVEL_ERROR, "Declared decompressed size exceeds %llu bytes",
-                (unsigned long long)MAX_DECOMPRESSED_SIZE);
+  unsigned long long hard_limit =
+      maximum_size < MAX_DECOMPRESSED_SIZE ? maximum_size : MAX_DECOMPRESSED_SIZE;
+  if (dst_size > hard_limit) {
+    log_message(LOG_LEVEL_ERROR, "Declared decompressed size exceeds %llu bytes", hard_limit);
    return NULL;
  }

@@ -101,6 +107,8 @@ Data* data_decompress(Data* compressed_data) {
  }

  size_t buf_size = (dst_size > 0) ? (size_t)dst_size : INITIAL_DECOMPRESS_BUF_SIZE;
+  if (buf_size > maximum_size)
+    buf_size = maximum_size;
  Data* uncompressed_data = data_create_empty(buf_size);
  if (!uncompressed_data) {
    log_message(LOG_LEVEL_ERROR, "Failed to allocate decompression buffer");
@@ -121,7 +129,7 @@ Data* data_decompress(Data* compressed_data) {
      return NULL;
    }
    if (ret > 0 && output.pos == output.size) {
-      if (buf_size >= MAX_DECOMPRESSED_SIZE) {
+      if (buf_size >= hard_limit || buf_size > SIZE_MAX / 2) {
        log_message(LOG_LEVEL_ERROR, "Decompressed data exceeds %llu bytes",
                    (unsigned long long)MAX_DECOMPRESSED_SIZE);
        ZSTD_freeDCtx(dctx);
@@ -129,8 +137,8 @@ Data* data_decompress(Data* compressed_data) {
        return NULL;
      }
      buf_size *= 2;
-      if (buf_size > MAX_DECOMPRESSED_SIZE)
-        buf_size = MAX_DECOMPRESSED_SIZE;
+      if (buf_size > hard_limit)
+        buf_size = (size_t)hard_limit;
      void* new_data = realloc(uncompressed_data->data, buf_size);
      if (!new_data) {
        log_message(LOG_LEVEL_ERROR, "Failed to grow decompression buffer");
@@ -150,3 +158,7 @@ Data* data_decompress(Data* compressed_data) {
  log_message(LOG_LEVEL_DEBUG, "Decompressed data successfully");
  return uncompressed_data;
 }
+
+Data* data_decompress(Data* compressed_data) {
+  return data_decompress_limited(compressed_data, MAX_DECOMPRESSED_SIZE);
+}
@@ -6,6 +6,7 @@

 Data* data_compress(Data* data_to_compress, int compression_level);
 Data* data_decompress(Data* compressed_data);
+Data* data_decompress_limited(Data* compressed_data, size_t maximum_size);
 bool compression_should_skip(const char* path);

 #endif
@@ -104,6 +104,14 @@ static bool valid_wire_bool(int value) {
  return value == 0 || value == 1;
 }

+static bool receive_wire_bool(int fd, bool* value) {
+  int wire_value;
+  if (!receive_int(fd, &wire_value) || !valid_wire_bool(wire_value))
+    return false;
+  *value = wire_value != 0;
+  return true;
+}
+
 static bool validate_received_config(const Config* config) {
  return valid_wire_bool(config->save_to_disk) && valid_wire_bool(config->use_multithreading) &&
         valid_wire_bool(config->use_chunk_serialization) &&
@@ -166,6 +174,10 @@ void config_parse_ssh_dest(Config* config) {
 void config_delete(Config* config) {
  if (config == NULL)
    return;
+  if (config->log_file) {
+    fclose(config->log_file);
+    config->log_file = NULL;
+  }
  free(config->version);
  free(config->send_directory);
  free(config->receive_root_directory);
@@ -347,135 +359,66 @@ Config* config_receive(int file_descriptor) {
    return NULL;
  }
  int tmp;
-  if (!receive_int(file_descriptor, &tmp))
+  if (!receive_wire_bool(file_descriptor, &config->save_to_disk) ||
+      !receive_wire_bool(file_descriptor, &config->use_multithreading) ||
+      !receive_wire_bool(file_descriptor, &config->use_chunk_serialization) ||
+      !receive_wire_bool(file_descriptor, &config->use_compression) ||
+      !receive_wire_bool(file_descriptor, &config->use_metadata))
    goto error;
-  if (!valid_wire_bool(tmp))
-    goto error;
-  config->save_to_disk = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  if (!valid_wire_bool(tmp))
-    goto error;
-  config->use_multithreading = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->use_chunk_serialization = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  if (!valid_wire_bool(tmp))
-    goto error;
-  config->use_compression = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  if (!valid_wire_bool(tmp))
-    goto error;
-  config->use_metadata = tmp;
  if (!receive_int(file_descriptor, &tmp))
    goto error;
  config->compression_level = tmp;
  if (!receive_n_data(file_descriptor, &config->chunk_size, sizeof(config->chunk_size)))
    goto error;
-  if (!receive_int(file_descriptor, &tmp))
+  if (!receive_wire_bool(file_descriptor, &config->use_sendfile) ||
+      !receive_wire_bool(file_descriptor, &config->use_delete) ||
+      !receive_wire_bool(file_descriptor, &config->use_incremental) ||
+      !receive_wire_bool(file_descriptor, &config->use_delta))
    goto error;
-  if (!valid_wire_bool(tmp))
-    goto error;
-  config->use_sendfile = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  if (!valid_wire_bool(tmp))
-    goto error;
-  config->use_delete = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  if (!valid_wire_bool(tmp))
-    goto error;
-  config->use_incremental = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  if (!valid_wire_bool(tmp))
-    goto error;
-  config->use_delta = tmp;
  if (!receive_n_data(file_descriptor, &config->delta_block_size, sizeof(config->delta_block_size)))
    goto error;
  if (!receive_n_data(file_descriptor, &config->delta_max_file_size, sizeof(unsigned long long)))
    goto error;
-  if (!receive_int(file_descriptor, &tmp))
+  if (!receive_wire_bool(file_descriptor, &config->backup))
    goto error;
-  config->backup = tmp;
  config->backup_dir = receive_str(file_descriptor);
  if (config->backup_dir == NULL)
    goto error;
-  if (!receive_int(file_descriptor, &tmp))
+  if (!receive_wire_bool(file_descriptor, &config->follow_symlinks) ||
+      !receive_wire_bool(file_descriptor, &config->copy_links) ||
+      !receive_wire_bool(file_descriptor, &config->safe_links) ||
+      !receive_wire_bool(file_descriptor, &config->copy_unsafe_links) ||
+      !receive_wire_bool(file_descriptor, &config->preserve_hard_links) ||
+      !receive_wire_bool(file_descriptor, &config->preserve_acls) ||
+      !receive_wire_bool(file_descriptor, &config->preserve_xattrs) ||
+      !receive_wire_bool(file_descriptor, &config->preserve_devices) ||
+      !receive_wire_bool(file_descriptor, &config->preserve_sparse) ||
+      !receive_wire_bool(file_descriptor, &config->update) ||
+      !receive_wire_bool(file_descriptor, &config->inplace) ||
+      !receive_wire_bool(file_descriptor, &config->append) ||
+      !receive_wire_bool(file_descriptor, &config->append_verify) ||
+      !receive_wire_bool(file_descriptor, &config->delete_excluded) ||
+      !receive_wire_bool(file_descriptor, &config->delete_after))
    goto error;
-  config->follow_symlinks = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->copy_links = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->safe_links = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->copy_unsafe_links = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->preserve_hard_links = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->preserve_acls = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->preserve_xattrs = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->preserve_devices = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->preserve_sparse = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->update = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->inplace = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->append = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->append_verify = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->delete_excluded = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->delete_after = tmp;
  if (!receive_n_data(file_descriptor, &config->max_delete, sizeof(config->max_delete)))
    goto error;
-  if (!receive_int(file_descriptor, &tmp))
+  if (!receive_wire_bool(file_descriptor, &config->relative) ||
+      !receive_wire_bool(file_descriptor, &config->prune_empty_dirs))
    goto error;
-  config->relative = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->prune_empty_dirs = tmp;
  config->temp_dir = receive_str(file_descriptor);
  if (config->temp_dir == NULL)
    goto error;
-  if (!receive_int(file_descriptor, &tmp))
+  if (!receive_wire_bool(file_descriptor, &config->partial))
    goto error;
-  config->partial = tmp;
  config->partial_dir = receive_str(file_descriptor);
  if (config->partial_dir == NULL)
    goto error;
  config->suffix = receive_str(file_descriptor);
  if (config->suffix == NULL)
    goto error;
-  if (!receive_int(file_descriptor, &tmp))
+  if (!receive_wire_bool(file_descriptor, &config->delete_before) ||
+      !receive_wire_bool(file_descriptor, &config->checksum))
    goto error;
-  config->delete_before = tmp;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  config->checksum = tmp;
  config->compress_choice = receive_str(file_descriptor);
  if (config->compress_choice == NULL)
    goto error;
@@ -21,6 +21,7 @@ Data* data_create_reserve(size_t size) {
  }
  d->data = NULL;
  d->size = size;
+  d->protocol_charge = 0;
  return d;
 }

@@ -33,12 +34,15 @@ Data* data_create(void* data, size_t data_size) {
  }
  new_data->data = data;
  new_data->size = data_size;
+  new_data->protocol_charge = 0;
  return new_data;
 }

 void data_destroy(Data* data) {
  if (data == NULL)
    return;
+  if (data->protocol_charge != 0)
+    protocol_release_memory(data->protocol_charge);
  free(data->data);
  free(data);
 }
@@ -6,11 +6,14 @@
 typedef struct {
  void* data;
  size_t size;
+  /* Non-zero only for a buffer charged to the protocol connection budget. */
+  size_t protocol_charge;
 } Data;

 Data* data_create_empty(size_t data_size);
 Data* data_create_reserve(size_t size);
 Data* data_create(void* data, size_t data_size);
 void data_destroy(Data* data);
+void protocol_release_memory(size_t charge);

 #endif
@@ -1,6 +1,7 @@
 #include "delta.h"
 #include "log.h"
 #include <stdint.h>
+#include <limits.h>
 #include <stdlib.h>
 #include <string.h>

@@ -36,7 +37,8 @@ DeltaSignature* delta_signature_create(const void* old_file_data, uint64_t old_f
  if (old_file_data == NULL || old_file_size == 0 || block_size == 0)
    return NULL;

-  if (old_file_size > DELTA_MAX_FILE_SIZE || old_file_size > UINT32_MAX * (uint64_t)block_size)
+  if (old_file_size > DELTA_MAX_FILE_SIZE || block_size > DELTA_BLOCK_SIZE_MAX ||
+      old_file_size > UINT32_MAX * (uint64_t)block_size)
    return NULL;

  uint32_t block_count = (uint32_t)((old_file_size + block_size - 1) / block_size);
@@ -48,7 +50,11 @@ DeltaSignature* delta_signature_create(const void* old_file_data, uint64_t old_f
  sig->file_size = old_file_size;
  sig->block_size = block_size;
  sig->block_count = block_count;
-  sig->blocks = malloc(block_count * sizeof(DeltaBlockSig));
+  if (block_count == 0) {
+    free(sig);
+    return NULL;
+  }
+  sig->blocks = malloc((size_t)block_count * sizeof(DeltaBlockSig));
  if (!sig->blocks) {
    free(sig);
    return NULL;
@@ -70,8 +76,11 @@ Data* delta_signature_serialize(const DeltaSignature* sig) {
  if (!sig)
    return NULL;

-  uint64_t total = sizeof(uint64_t) + sizeof(uint32_t) + sizeof(uint32_t) +
-                   (uint64_t)sig->block_count * (sizeof(uint32_t) + sizeof(uint32_t));
+  uint64_t block_bytes = (uint64_t)sig->block_count * (sizeof(uint32_t) + sizeof(uint32_t));
+  uint64_t total = sizeof(uint64_t) + sizeof(uint32_t) + sizeof(uint32_t) + block_bytes;
+  if (block_bytes > UINT64_MAX - (sizeof(uint64_t) + sizeof(uint32_t) + sizeof(uint32_t)) ||
+      total > SIZE_MAX)
+    return NULL;

  uint8_t* buf = malloc((size_t)total);
  if (!buf)
@@ -166,8 +175,10 @@ void delta_signature_destroy(DeltaSignature* sig) {
 static bool ensure_capacity(DeltaInstruction** instrs, uint32_t* capacity, uint32_t count) {
  if (count < *capacity)
    return true;
+  if (*capacity > MAX_DELTA_INSTRUCTIONS / 2)
+    return false;
  uint32_t new_cap = *capacity * 2;
-  DeltaInstruction* tmp = realloc(*instrs, new_cap * sizeof(DeltaInstruction));
+  DeltaInstruction* tmp = realloc(*instrs, (size_t)new_cap * sizeof(DeltaInstruction));
  if (!tmp)
    return false;
  *instrs = tmp;
@@ -179,6 +190,8 @@ static bool flush_literal(DeltaInstruction** instrs, uint32_t* capacity, uint32_
                          const uint8_t* data, uint64_t start, uint64_t end) {
  if (start >= end)
    return true;
+  if (end - start > UINT32_MAX || *count >= MAX_DELTA_INSTRUCTIONS)
+    return false;
  uint32_t lit_len = (uint32_t)(end - start);
  if (!ensure_capacity(instrs, capacity, *count))
    return false;
@@ -193,16 +206,26 @@ static bool flush_literal(DeltaInstruction** instrs, uint32_t* capacity, uint32_
  return true;
 }

+static void free_instructions(DeltaInstruction* instrs, uint32_t count) {
+  if (!instrs)
+    return;
+  for (uint32_t i = 0; i < count; i++)
+    if (instrs[i].type == DELTA_INSTR_LITERAL)
+      free(instrs[i].literal.data);
+  free(instrs);
+}
+
 Delta* delta_compute(const void* new_file_data, uint64_t new_file_size, const DeltaSignature* sig,
                     uint32_t block_size) {
-  if (!new_file_data || !sig || new_file_size == 0 || block_size == 0)
+  if (!new_file_data || !sig || !sig->blocks || new_file_size == 0 || block_size == 0 ||
+      block_size > DELTA_BLOCK_SIZE_MAX || sig->block_size != block_size)
    return NULL;

  const uint8_t* new_data = (const uint8_t*)new_file_data;

  uint32_t capacity = 64;
  uint32_t count = 0;
-  DeltaInstruction* instrs = malloc(capacity * sizeof(DeltaInstruction));
+  DeltaInstruction* instrs = malloc((size_t)capacity * sizeof(DeltaInstruction));
  if (!instrs)
    return NULL;

@@ -246,14 +269,14 @@ Delta* delta_compute(const void* new_file_data, uint64_t new_file_size, const De
        if (xxh == sig->blocks[j].xxhash) {
          if (has_literal) {
            if (!flush_literal(&instrs, &capacity, &count, new_data, literal_start, i)) {
-              free(instrs);
+              free_instructions(instrs, count);
              return NULL;
            }
            has_literal = false;
          }

          if (!ensure_capacity(&instrs, &capacity, count)) {
-            free(instrs);
+            free_instructions(instrs, count);
            return NULL;
          }
          instrs[count].type = DELTA_INSTR_BLOCK_MATCH;
@@ -281,18 +304,14 @@ Delta* delta_compute(const void* new_file_data, uint64_t new_file_size, const De

  if (has_literal) {
    if (!flush_literal(&instrs, &capacity, &count, new_data, literal_start, new_file_size)) {
-      free(instrs);
+      free_instructions(instrs, count);
      return NULL;
    }
  }

  Delta* delta = malloc(sizeof(Delta));
  if (!delta) {
-    for (uint32_t k = 0; k < count; k++) {
-      if (instrs[k].type == DELTA_INSTR_LITERAL)
-        free(instrs[k].literal.data);
-    }
-    free(instrs);
+    free_instructions(instrs, count);
    return NULL;
  }

@@ -302,11 +321,24 @@ Delta* delta_compute(const void* new_file_data, uint64_t new_file_size, const De
  delta->delta_size = 0;

  for (uint32_t k = 0; k < count; k++) {
+    if (delta->delta_size == UINT64_MAX) {
+      delta_destroy(delta);
+      return NULL;
+    }
    delta->delta_size += 1;
    if (instrs[k].type == DELTA_INSTR_BLOCK_MATCH) {
+      if (delta->delta_size > UINT64_MAX - sizeof(uint32_t) * 3) {
+        delta_destroy(delta);
+        return NULL;
+      }
      delta->delta_size += sizeof(uint32_t) * 3;
    } else {
-      delta->delta_size += sizeof(uint32_t) + instrs[k].literal.length;
+      uint64_t extra = sizeof(uint32_t) + instrs[k].literal.length;
+      if (delta->delta_size > UINT64_MAX - extra) {
+        delta_destroy(delta);
+        return NULL;
+      }
+      delta->delta_size += extra;
    }
  }

@@ -317,7 +349,12 @@ Data* delta_serialize(const Delta* delta) {
  if (!delta)
    return NULL;

-  uint64_t total = sizeof(uint64_t) + sizeof(uint32_t) + delta->delta_size;
+  if (delta->instruction_count > 0 && !delta->instructions)
+    return NULL;
+  uint64_t header_size = sizeof(uint64_t) + sizeof(uint32_t);
+  if (delta->delta_size > UINT64_MAX - header_size || header_size + delta->delta_size > SIZE_MAX)
+    return NULL;
+  uint64_t total = header_size + delta->delta_size;
  uint8_t* buf = malloc((size_t)total);
  if (!buf)
    return NULL;
@@ -375,8 +412,10 @@ Delta* delta_deserialize(const Data* data) {
    return NULL;
  }

-  delta->instructions = malloc(delta->instruction_count * sizeof(DeltaInstruction));
-  if (!delta->instructions) {
+  delta->instructions = delta->instruction_count == 0
+                            ? NULL
+                            : malloc((size_t)delta->instruction_count * sizeof(DeltaInstruction));
+  if (delta->instruction_count > 0 && !delta->instructions) {
    free(delta);
    return NULL;
  }
@@ -385,11 +424,7 @@ Delta* delta_deserialize(const Data* data) {

  for (uint32_t i = 0; i < delta->instruction_count; i++) {
    if (pos >= data->size) {
-      for (uint32_t k = 0; k < i; k++) {
-        if (delta->instructions[k].type == DELTA_INSTR_LITERAL)
-          free(delta->instructions[k].literal.data);
-      }
-      free(delta->instructions);
+      free_instructions(delta->instructions, i);
      free(delta);
      return NULL;
    }
@@ -401,12 +436,8 @@ Delta* delta_deserialize(const Data* data) {
    delta->delta_size += 1;

    if (type == DELTA_OP_BLOCK_MATCH) {
-      if (pos + sizeof(uint32_t) * 3 > data->size) {
-        for (uint32_t k = 0; k < i; k++) {
-          if (delta->instructions[k].type == DELTA_INSTR_LITERAL)
-            free(delta->instructions[k].literal.data);
-        }
-        free(delta->instructions);
+      if (data->size - pos < sizeof(uint32_t) * 3) {
+        free_instructions(delta->instructions, i);
        free(delta);
        return NULL;
      }
@@ -419,12 +450,8 @@ Delta* delta_deserialize(const Data* data) {
      pos += sizeof(uint32_t);
      delta->delta_size += sizeof(uint32_t) * 3;
    } else if (type == DELTA_OP_LITERAL) {
-      if (pos + sizeof(uint32_t) > data->size) {
-        for (uint32_t k = 0; k < i; k++) {
-          if (delta->instructions[k].type == DELTA_INSTR_LITERAL)
-            free(delta->instructions[k].literal.data);
-        }
-        free(delta->instructions);
+      if (data->size - pos < sizeof(uint32_t)) {
+        free_instructions(delta->instructions, i);
        free(delta);
        return NULL;
      }
@@ -433,23 +460,15 @@ Delta* delta_deserialize(const Data* data) {
      pos += sizeof(uint32_t);

      uint32_t lit_len = delta->instructions[i].literal.length;
-      if (pos + lit_len > data->size) {
-        for (uint32_t k = 0; k < i; k++) {
-          if (delta->instructions[k].type == DELTA_INSTR_LITERAL)
-            free(delta->instructions[k].literal.data);
-        }
-        free(delta->instructions);
+      if (lit_len > data->size - pos) {
+        free_instructions(delta->instructions, i);
        free(delta);
        return NULL;
      }
-      delta->instructions[i].literal.data = malloc(lit_len);
+      delta->instructions[i].literal.data = malloc(lit_len ? lit_len : 1);
      if (!delta->instructions[i].literal.data) {
        log_message(LOG_LEVEL_ERROR, "Failed to allocate %u bytes for literal data", lit_len);
-        for (uint32_t k = 0; k < i; k++) {
-          if (delta->instructions[k].type == DELTA_INSTR_LITERAL)
-            free(delta->instructions[k].literal.data);
-        }
-        free(delta->instructions);
+        free_instructions(delta->instructions, i);
        free(delta);
        return NULL;
      }
@@ -457,11 +476,7 @@ Delta* delta_deserialize(const Data* data) {
      pos += lit_len;
      delta->delta_size += sizeof(uint32_t) + lit_len;
    } else {
-      for (uint32_t k = 0; k < i; k++) {
-        if (delta->instructions[k].type == DELTA_INSTR_LITERAL)
-          free(delta->instructions[k].literal.data);
-      }
-      free(delta->instructions);
+      free_instructions(delta->instructions, i);
      free(delta);
      return NULL;
    }
@@ -477,7 +492,7 @@ void* delta_apply(const void* old_data, uint64_t old_size, const Delta* delta,
      delta->new_file_size > DELTA_MAX_FILE_SIZE || delta->new_file_size > SIZE_MAX)
    return NULL;

-  void* output = malloc((size_t)delta->new_file_size);
+  void* output = malloc(delta->new_file_size ? (size_t)delta->new_file_size : 1);
  if (!output)
    return NULL;

@@ -502,7 +517,7 @@ void* delta_apply(const void* old_data, uint64_t old_size, const Delta* delta,
      }
      memcpy(out + out_pos, old + src_offset, len);
      out_pos += len;
-    } else {
+    } else if (delta->instructions[i].type == DELTA_INSTR_LITERAL) {
      uint32_t len = delta->instructions[i].literal.length;
      if (out_pos > delta->new_file_size || (uint64_t)len > delta->new_file_size - out_pos) {
        free(output);
@@ -510,6 +525,9 @@ void* delta_apply(const void* old_data, uint64_t old_size, const Delta* delta,
      }
      memcpy(out + out_pos, delta->instructions[i].literal.data, len);
      out_pos += len;
+    } else {
+      free(output);
+      return NULL;
    }
  }

@@ -545,7 +563,7 @@ bool delta_should_attempt(uint64_t old_size, uint64_t new_size, uint64_t max_fil
 }

 bool delta_is_worthwhile(const Delta* delta, uint64_t new_file_size) {
-  if (!delta || delta->instruction_count == 0)
+  if (!delta || delta->instruction_count == 0 || new_file_size == 0)
    return false;

  bool has_match = false;
@@ -24,7 +24,7 @@
 #include "utils.h"

 #define MAX_SERVER_DELETE_COUNT 100000U
-#define MAX_FILE_DATA_SIZE (64ULL * 1024 * 1024)
+#define MAX_FILE_DATA_SIZE MAX_RECEIVE_FILE_SIZE

 bool file_checksum(File* file, uint64_t* checksum) {
  if (!file || !checksum || !file->data)
@@ -48,7 +48,7 @@ File* file_create(const char* path) {
    return NULL;
  }

-  int path_len = strlen(path);
+  size_t path_len = strlen(path);
  file->path = (char*)malloc(path_len + 1);
  if (file->path == NULL) {
    free(file);
@@ -104,7 +104,7 @@ void file_metadata_destroy(void* metadata) {
 }

 bool file_load_data(File* file) {
-  if (file == NULL)
+  if (file == NULL || !file->data)
    return false;
  if (file->data->data == NULL) {
    if (file->data->size == 0)
@@ -128,7 +128,7 @@ bool file_load_data(File* file) {

 bool file_send_single_calls(File* file, int file_descriptor, bool use_metadata,
                            int compression_level, bool send_path) {
-  if (!file || !file->path || !file->data)
+  if (!file || !file->path || !file->data || (file->data->size != 0 && !file->data->data))
    return false;
  const Data* data_to_send = file->data;
  Data* compressed_data = NULL;
@@ -159,6 +159,7 @@ bool file_send_single_calls(File* file, int file_descriptor, bool use_metadata,
 static bool to_disk_secure(const char* path, const void* data, unsigned long long data_size,
                           bool inplace, bool sparse, const FileMetadata* metadata);
 static int open_secure_parent(const char* path, char** leaf_out, bool create_dirs);
+static bool ensure_directory_secure(const char* path);

 bool file_path_exists_secure(const char* path) {
  struct stat st;
@@ -184,15 +185,23 @@ static bool rename_secure(const char* old_path, const char* new_path);
 static int authorized_root_fd = -1;
 static char* authorized_root_path;

-void file_set_authorized_root(int fd, const char* canonical_path) {
-  authorized_root_fd = fd;
-  free(authorized_root_path);
-  authorized_root_path = canonical_path ? str_dup(canonical_path) : NULL;
+static bool path_is_within_root(const char* root, const char* path) {
+  size_t root_len = strlen(root);
+  return strncmp(root, path, root_len) == 0 && (path[root_len] == '\0' || path[root_len] == '/');
 }

-static bool path_is_within_root(const char* root, const char* path) {
-  size_t n = strlen(root);
-  return strncmp(root, path, n) == 0 && (path[n] == '\0' || path[n] == '/');
+bool file_set_authorized_root(int fd, const char* canonical_path) {
+  char* path_copy = canonical_path ? str_dup(canonical_path) : NULL;
+  if (canonical_path && !path_copy) {
+    authorized_root_fd = -1;
+    free(authorized_root_path);
+    authorized_root_path = NULL;
+    return false;
+  }
+  authorized_root_fd = fd;
+  free(authorized_root_path);
+  authorized_root_path = path_copy;
+  return true;
 }

 bool file_save_to_disk(const char* root_directory, const File* file, const Config* config) {
@@ -202,9 +211,11 @@ bool file_save_to_disk(const char* root_directory, const File* file, const Confi
  const char* backup_suffix = (config && config->suffix) ? config->suffix : "~";
  const char* backup_dir = (config && config->backup_dir) ? config->backup_dir : NULL;
  const char* partial_dir = (config && config->partial_dir) ? config->partial_dir : NULL;
-  char *confined_backup = NULL, *confined_partial = NULL;
+  char *confined_backup = NULL, *confined_partial = NULL, *disk_path = NULL;
+  char *backup_path = NULL, *parent_copy = NULL;

-  if (!file || !file->path || !file->data || has_path_traversal(file->path) ||
+  if (!file || !file->path || !file->data || (file->data->size != 0 && !file->data->data) ||
+      has_path_traversal(file->path) ||
      (backup_enabled &&
       (!backup_suffix || backup_suffix[0] == '\0' || strchr(backup_suffix, '/') != NULL ||
        strcmp(backup_suffix, ".") == 0 || strcmp(backup_suffix, "..") == 0))) {
@@ -224,45 +235,20 @@ bool file_save_to_disk(const char* root_directory, const File* file, const Confi
    return false;
  }

-  char* resolved_root = NULL;
  const char* actual_root =
      (partial_dir && config && config->partial) ? confined_partial : root_directory;
-  resolved_root = realpath(actual_root, NULL);
-  if (resolved_root == NULL) {
-    if (mkdir_r(actual_root)) {
-      resolved_root = realpath(actual_root, NULL);
-    }
-  }
-  if (resolved_root == NULL) {
-    log_message(LOG_LEVEL_ERROR, "Failed to resolve destination root: %s", actual_root);
-    free(confined_backup);
-    free(confined_partial);
-    return false;
-  }
-  char* resolved_base = realpath(root_directory, NULL);
-  if (resolved_base == NULL || !path_is_within_root(resolved_base, resolved_root)) {
-    free(resolved_base);
-    free(confined_backup);
-    free(confined_partial);
-    free(resolved_root);
-    return false;
-  }
-  free(resolved_base);
-
-  char* disk_path = path_cat(resolved_root, file->path);
+  disk_path = path_cat(actual_root, file->path);
  if (disk_path == NULL) {
    free(confined_backup);
    free(confined_partial);
-    free(resolved_root);
    return false;
  }

  /* --update is receiver-side policy: never replace a newer destination. */
  if (config && config->update) {
    struct stat destination_stat;
-    if (stat(disk_path, &destination_stat) == 0 && file->metadata &&
+    if (file_stat_secure(disk_path, &destination_stat) && file->metadata &&
        destination_stat.st_mtime > file->metadata->mtime_sec) {
-      free(resolved_root);
      free(confined_backup);
      free(confined_partial);
      free(disk_path);
@@ -272,99 +258,50 @@ bool file_save_to_disk(const char* root_directory, const File* file, const Confi

  if (backup_enabled) {
    struct stat backup_stat;
-    if (stat(disk_path, &backup_stat) == 0) {
-      char* backup_path = NULL;
+    if (file_stat_secure(disk_path, &backup_stat)) {
      if (backup_dir) {
-        char* resolved_backup_dir = realpath(confined_backup, NULL);
-        if (!resolved_backup_dir) {
-          mkdir_r(confined_backup);
-          resolved_backup_dir = realpath(confined_backup, NULL);
-        }
-        if (resolved_backup_dir) {
-          char* backup_base = realpath(root_directory, NULL);
-          if (backup_base && path_is_within_root(backup_base, resolved_backup_dir))
-            backup_path = path_cat(resolved_backup_dir, file->path);
-          free(backup_base);
-          free(resolved_backup_dir);
-        }
-      }
-      if (!backup_path) {
+        backup_path = path_cat(confined_backup, file->path);
+      } else {
        size_t path_len = strlen(disk_path);
        size_t suffix_len = strlen(backup_suffix);
+        if (path_len > SIZE_MAX - suffix_len - 1)
+          goto fail;
        backup_path = malloc(path_len + suffix_len + 1);
        if (backup_path) {
          memcpy(backup_path, disk_path, path_len);
          memcpy(backup_path + path_len, backup_suffix, suffix_len + 1);
        }
      }
-      if (backup_path) {
-        char* backup_dir_path = str_dup(backup_path);
-        if (backup_dir_path) {
-          const char* bdir = dirname(backup_dir_path);
-          mkdir_r(bdir);
-          free(backup_dir_path);
-        }
-        if (!rename_secure(disk_path, backup_path)) {
-          free(backup_path);
-          free(resolved_root);
-          free(confined_backup);
-          free(confined_partial);
-          free(disk_path);
-          return false;
-        }
+      if (!backup_path)
+        goto fail;
+      parent_copy = str_dup(backup_path);
+      if (!parent_copy || !ensure_directory_secure(dirname(parent_copy)))
+        goto fail;
+      free(parent_copy);
+      parent_copy = NULL;
+      if (!rename_secure(disk_path, backup_path))
+        goto fail;
      free(backup_path);
+      backup_path = NULL;
    }
  }
-  }
-
-  char* dir_dup = str_dup(disk_path);
-  if (!dir_dup) {
-    free(confined_backup);
-    free(confined_partial);
-    free(resolved_root);
-    free(disk_path);
-    return false;
-  }
-  char* dir_str = dirname(dir_dup);
-  if (!mkdir_r(dir_str)) {
-    free(dir_dup);
-    free(confined_backup);
-    free(confined_partial);
-    free(resolved_root);
-    free(disk_path);
-    return false;
-  }
-  char* resolved_dir = realpath(dir_str, NULL);
-  free(dir_dup);
-  if (resolved_dir == NULL) {
-    log_message(LOG_LEVEL_ERROR, "Failed to resolve directory for: %s", disk_path);
-    free(confined_backup);
-    free(confined_partial);
-    free(resolved_root);
-    free(disk_path);
-    return false;
-  }
-
-  size_t root_len = strlen(resolved_root);
-  if (strncmp(resolved_dir, resolved_root, root_len) != 0 ||
-      (resolved_dir[root_len] != '\0' && resolved_dir[root_len] != '/')) {
-    log_message(LOG_LEVEL_ERROR, "Path escape detected: %s is outside %s", disk_path, actual_root);
-    free(resolved_dir);
-    free(confined_backup);
-    free(confined_partial);
-    free(resolved_root);
-    free(disk_path);
-    return false;
-  }
-  free(resolved_dir);
-  free(resolved_root);

  bool ok = to_disk_secure(disk_path, file->data->data, file->data->size, inplace, sparse,
                           file->metadata);
+  free(parent_copy);
+  free(backup_path);
  free(confined_backup);
  free(confined_partial);
  free(disk_path);
  return ok;
+
+fail:
+  free(parent_copy);
+  free(backup_path);
+  free(confined_backup);
+  free(confined_partial);
+  free(disk_path);
+  return false;
 }

 static File* receive_delta_file(int fd, const Config* config, const char* check_path,
@@ -402,7 +339,7 @@ static File* receive_delta_file(int fd, const Config* config, const char* check_
  }

  if (resp == STATUS_DELTA_DATA) {
-    Data* delta_data = receive_data(fd);
+    Data* delta_data = receive_data_limited(fd, MAX_RECEIVE_FILE_SIZE);
    if (!delta_data) {
      delta_signature_destroy(sig);
      free(old_data);
@@ -412,7 +349,7 @@ static File* receive_delta_file(int fd, const Config* config, const char* check_

    Data* raw_delta = delta_data;
    if (config->use_compression) {
-      raw_delta = data_decompress(delta_data);
+      raw_delta = data_decompress_limited(delta_data, MAX_RECEIVE_FILE_SIZE);
      data_destroy(delta_data);
      if (!raw_delta) {
        free(old_data);
@@ -431,8 +368,15 @@ static File* receive_delta_file(int fd, const Config* config, const char* check_
      return NULL;
    }

-    void* new_data = delta_apply(old_data, old_size, delta, config->delta_block_size);
    uint64_t new_size = delta->new_file_size;
+    if (new_size > MAX_RECEIVE_FILE_SIZE || new_size > SIZE_MAX) {
+      delta_destroy(delta);
+      free(old_data);
+      delta_signature_destroy(sig);
+      send_status(fd, STATUS_ERROR);
+      return NULL;
+    }
+    void* new_data = delta_apply(old_data, old_size, delta, config->delta_block_size);
    delta_destroy(delta);

    if (!new_data) {
@@ -500,7 +444,7 @@ static File* receive_delta_file(int fd, const Config* config, const char* check_
      }
    }

-    Data* file_data = receive_data(fd);
+    Data* file_data = receive_data_limited(fd, MAX_RECEIVE_FILE_SIZE);
    if (file_data == NULL) {
      file_destroy(file);
      send_status(fd, STATUS_ERROR);
@@ -508,7 +452,7 @@ static File* receive_delta_file(int fd, const Config* config, const char* check_
    }

    if (config->use_compression) {
-      Data* uncompressed = data_decompress(file_data);
+      Data* uncompressed = data_decompress_limited(file_data, MAX_RECEIVE_FILE_SIZE);
      data_destroy(file_data);
      if (uncompressed == NULL) {
        file_destroy(file);
@@ -536,6 +480,10 @@ static File* receive_delta_file(int fd, const Config* config, const char* check_
 }

 File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
+  if (!config || !skipped) {
+    send_status(fd, STATUS_ERROR);
+    return NULL;
+  }
  *skipped = false;
  char* check_path = receive_str(fd);
  if (check_path == NULL) {
@@ -558,6 +506,12 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
    return NULL;
  }

+  if (check_size > MAX_RECEIVE_FILE_SIZE) {
+    free(check_path);
+    send_status(fd, STATUS_ERROR);
+    return NULL;
+  }
+
  if (has_path_traversal(check_path)) {
    log_message(LOG_LEVEL_ERROR, "Path traversal detected: %s", check_path);
    free(check_path);
@@ -566,10 +520,14 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
  }

  char* full_path = path_cat(config->receive_root_directory, check_path);
+  if (!full_path) {
+    free(check_path);
+    send_status(fd, STATUS_ERROR);
+    return NULL;
+  }
  struct stat st;
  bool has_old_file = false;
  int old_fd = -1;
-  if (full_path) {
  char* leaf = NULL;
  int parent_fd = open_secure_parent(full_path, &leaf, false);
  if (parent_fd >= 0) {
@@ -578,10 +536,9 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
    close(parent_fd);
    has_old_file = old_fd >= 0 && fstat(old_fd, &st) == 0 && S_ISREG(st.st_mode);
  }
-  }
  unsigned long long old_size = has_old_file ? (unsigned long long)st.st_size : 0;
  void* old_data = NULL;
-  if (has_old_file && old_size > 0 && old_size <= DELTA_MAX_FILE_SIZE && old_size <= SIZE_MAX) {
+  if (has_old_file && old_size > 0 && old_size <= MAX_RECEIVE_FILE_SIZE && old_size <= SIZE_MAX) {
    old_data = malloc((size_t)old_size);
    if (old_data) {
      size_t got = 0;
@@ -625,7 +582,7 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
    return NULL;
  }

-  bool try_delta = config->use_delta && has_old_file &&
+  bool try_delta = config->use_delta && has_old_file && old_data != NULL &&
                   delta_should_attempt(old_size, check_size, config->delta_max_file_size);

  if (try_delta) {
@@ -667,7 +624,7 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
    }
  }

-  Data* file_data = receive_data(fd);
+  Data* file_data = receive_data_limited(fd, MAX_RECEIVE_FILE_SIZE);
  if (file_data == NULL) {
    file_destroy(file);
    send_status(fd, STATUS_ERROR);
@@ -675,7 +632,7 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
  }

  if (config->use_compression) {
-    Data* uncompressed = data_decompress(file_data);
+    Data* uncompressed = data_decompress_limited(file_data, MAX_RECEIVE_FILE_SIZE);
    data_destroy(file_data);
    if (uncompressed == NULL) {
      file_destroy(file);
@@ -708,9 +665,19 @@ static int open_secure_parent(const char* path, char** leaf_out, bool create_dir
    return -1;
  }
  int fd;
-  if (authorized_root_fd >= 0 && authorized_root_path && path[0] == '/' &&
-      path_is_within_root(authorized_root_path, path)) {
+  if (authorized_root_fd >= 0) {
+    if (!authorized_root_path || path[0] != '/' ||
+        !path_is_within_root(authorized_root_path, path)) {
+      free(copy);
+      free(leaf);
+      return -1;
+    }
    fd = dup(authorized_root_fd);
+    if (fd < 0) {
+      free(copy);
+      free(leaf);
+      return -1;
+    }
    size_t root_len = strlen(authorized_root_path);
    char* relative = str_dup(path + root_len);
    if (!relative) {
@@ -734,10 +701,18 @@ static int open_secure_parent(const char* path, char** leaf_out, bool create_dir
  char* save = NULL;
  char* component = strtok_r(parent, "/", &save);
  while (component) {
-    if (strcmp(component, ".") != 0 && strcmp(component, "..") != 0) {
+    if (strcmp(component, "..") == 0) {
+      close(fd);
+      free(copy);
+      free(leaf);
+      return -1;
+    }
+    if (strcmp(component, ".") != 0) {
      int next = openat(fd, component, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
-      if (create_dirs && next < 0 && errno == ENOENT && mkdirat(fd, component, 0755) == 0)
+      if (create_dirs && next < 0 && errno == ENOENT) {
+        if (mkdirat(fd, component, 0755) == 0 || errno == EEXIST)
          next = openat(fd, component, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
+      }
      if (next < 0) {
        close(fd);
        free(copy);
@@ -754,9 +729,28 @@ static int open_secure_parent(const char* path, char** leaf_out, bool create_dir
  return fd;
 }

+static bool ensure_directory_secure(const char* path) {
+  char* leaf = NULL;
+  int parent_fd = open_secure_parent(path, &leaf, true);
+  if (parent_fd < 0)
+    return false;
+
+  int dir_fd = openat(parent_fd, leaf, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
+  if (dir_fd < 0 && errno == ENOENT) {
+    if (mkdirat(parent_fd, leaf, 0755) == 0 || errno == EEXIST)
+      dir_fd = openat(parent_fd, leaf, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
+  }
+  bool ok = dir_fd >= 0;
+  if (dir_fd >= 0)
+    close(dir_fd);
+  close(parent_fd);
+  free(leaf);
+  return ok;
+}
+
 static bool rename_secure(const char* old_path, const char* new_path) {
  char *old_leaf = NULL, *new_leaf = NULL;
-  int old_parent = open_secure_parent(old_path, &old_leaf, true);
+  int old_parent = open_secure_parent(old_path, &old_leaf, false);
  int new_parent = open_secure_parent(new_path, &new_leaf, true);
  bool ok = old_parent >= 0 && new_parent >= 0 &&
            renameat(old_parent, old_leaf, new_parent, new_leaf) == 0;
@@ -833,106 +827,6 @@ bool to_disk(const char* path, const void* data, unsigned long long data_size, b
  if (!path || (!data && data_size != 0) || has_path_traversal(path))
    return false;
  return to_disk_secure(path, data, data_size, inplace, sparse, NULL);
-  /* Kept below only as historical context; all writes use descriptor-relative operations. */
-  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);
-  directory = str_dup(dir_result);
-  free(path_dup);
-  if (!directory)
-    return false;
-
-  bool ok = true;
-  if (!mkdir_r(directory))
-    goto done;
-
-  if (inplace) {
-    FILE* file_pointer = fopen(path, "wb");
-    if (file_pointer == NULL) {
-      perror("Could not open file for inplace write");
-      ok = false;
-      goto done;
-    }
-    if (sparse && data_size > 0) {
-      if (fseek(file_pointer, data_size - 1, SEEK_SET) != 0) {
-        perror("Failed to seek for sparse file");
-        fclose(file_pointer);
-        ok = false;
-        goto done;
-      }
-      if (fwrite("", 1, 1, file_pointer) != 1) {
-        perror("Failed to write sparse file");
-        fclose(file_pointer);
-        ok = false;
-        goto done;
-      }
-      rewind(file_pointer);
-    }
-    if (data_size > 0 && fwrite(data, 1, data_size, file_pointer) != data_size) {
-      perror("Failed to write all data to file");
-      fclose(file_pointer);
-      ok = false;
-      goto done;
-    }
-    fclose(file_pointer);
-    free(directory);
-    return true;
-  }
-
-  size_t path_len = strlen(path);
-  tmp_path = malloc(path_len + 5);
-  if (!tmp_path) {
-    ok = false;
-    goto done;
-  }
-  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 temporary file");
-    ok = false;
-    goto done;
-  }
-  if (sparse && data_size > 0) {
-    if (fseek(file_pointer, data_size - 1, SEEK_SET) != 0) {
-      perror("Failed to seek for sparse file");
-      fclose(file_pointer);
-      ok = false;
-      goto done;
-    }
-    if (fwrite("", 1, 1, file_pointer) != 1) {
-      perror("Failed to write sparse file");
-      fclose(file_pointer);
-      ok = false;
-      goto done;
-    }
-    rewind(file_pointer);
-  }
-  if (fwrite(data, 1, data_size, file_pointer) != data_size) {
-    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;
 }

 bool file_send_sendfile(File* file, int file_descriptor, bool use_metadata, int compression_level,
@@ -1044,13 +938,13 @@ File* file_receive(const Config* config, int file_descriptor) {
      return NULL;
    }
  }
-  Data* file_data = receive_data(file_descriptor);
+  Data* file_data = receive_data_limited(file_descriptor, MAX_RECEIVE_FILE_SIZE);
  if (file_data == NULL) {
    file_destroy(file);
    return NULL;
  }
-  if (config->use_compression) {
-    Data* file_data_uncompressed = data_decompress(file_data);
+  if (config->use_compression && !compression_should_skip(file->path)) {
+    Data* file_data_uncompressed = data_decompress_limited(file_data, MAX_RECEIVE_FILE_SIZE);
    data_destroy(file_data);
    if (file_data_uncompressed == NULL) {
      file_destroy(file);
@@ -1069,6 +963,8 @@ File* file_receive(const Config* config, int file_descriptor) {
 }

 size_t file_content_to_buffer(File* file) {
+  if (!file || !file->path || !file->data || (!file->data->data && file->data->size != 0))
+    return 0;
  FILE* file_pointer = fopen(file->path, "rb");
  if (file_pointer == NULL) {
    perror("Could not open the file!");
@@ -1085,16 +981,26 @@ size_t file_content_to_buffer(File* file) {
 }

 int receive_manifest(int fd, const Config* config, int* next_status) {
+  if (!config) {
+    send_status(fd, STATUS_ERROR);
+    return -1;
+  }
  int received_status = STATUS_ERROR;
  int* status_out = next_status ? next_status : &received_status;
  int count;
-  if (!receive_int(fd, &count))
+  if (!receive_int(fd, &count)) {
+    send_status(fd, STATUS_ERROR);
    return -1;
-  if (count < 0 || count > MAX_MANIFEST_ENTRIES)
+  }
+  if (count < 0 || count > MAX_MANIFEST_ENTRIES) {
+    send_status(fd, STATUS_ERROR);
    return -1;
+  }
  ArrayList* manifest = array_list_create(free);
-  if (!manifest)
+  if (!manifest) {
+    send_status(fd, STATUS_ERROR);
    return -1;
+  }
  size_t manifest_bytes = 0;
  for (int i = 0; i < count; i++) {
    char* s = receive_str(fd);
@@ -1104,22 +1010,28 @@ int receive_manifest(int fd, const Config* config, int* next_status) {
        (manifest_bytes += entry_size) > MAX_MANIFEST_BYTES || !array_list_add(manifest, s)) {
      free(s);
      array_list_delete(manifest);
+      send_status(fd, STATUS_ERROR);
      return -1;
    }
  }
  if (!receive_status(fd, status_out)) {
    array_list_delete(manifest);
+    send_status(fd, STATUS_ERROR);
    return -1;
  }
  /* Deletion is a commit operation: never perform it until the sender has
     completed the manifest frame successfully. */
  if (*status_out != STATUS_FINISHED || !config->use_delete) {
    array_list_delete(manifest);
+    if (*status_out != STATUS_FINISHED)
+      send_status(fd, STATUS_ERROR);
    return *status_out == STATUS_FINISHED ? 0 : -1;
  }
  fprintf(stderr, "Deleting files not in manifest...\n");
  bool deletion_ok =
      delete_extras_limited(config->receive_root_directory, manifest, MAX_SERVER_DELETE_COUNT);
  array_list_delete(manifest);
+  if (!deletion_ok)
+    send_status(fd, STATUS_ERROR);
  return deletion_ok ? 0 : -1;
 }
@@ -38,7 +38,8 @@ void file_metadata_destroy(void* metadata);
 bool to_disk(const char* path, const void* data, unsigned long long data_size, bool inplace,
             bool sparse);
 bool file_save_to_disk(const char* root_directory, const File* file, const Config* config);
-void file_set_authorized_root(int fd, const char* canonical_path);
+/* A configured fd without a canonical identity deliberately rejects paths. */
+bool file_set_authorized_root(int fd, const char* canonical_path);
 File* receive_incremental_check(int fd, const Config* config, bool* skipped);
 bool file_path_exists_secure(const char* path);
 bool file_stat_secure(const char* path, struct stat* st);
@@ -51,6 +51,8 @@ FileMetadata* metadata_from_buf(char** buf) {
  int32_t present;
  memcpy(&present, *buf, sizeof(present));
  *buf += sizeof(present);
+  if (present != 0 && present != 1)
+    return NULL;
  if (!present)
    return NULL;
  FileMetadata* m = malloc(sizeof(FileMetadata));
@@ -84,7 +86,7 @@ FileMetadata* metadata_from_buf(char** buf) {
  return m;
 }

-bool metadata_send(int file_descriptor, FileMetadata* m) {
+bool metadata_send(int file_descriptor, const FileMetadata* m) {
  if (m == NULL) {
    int32_t zero = 0;
    return send_n_data(file_descriptor, &zero, sizeof(zero));
@@ -27,7 +27,7 @@

 void metadata_to_buf(char** buf, const FileMetadata* m);
 FileMetadata* metadata_from_buf(char** buf);
-bool metadata_send(int file_descriptor, FileMetadata* m);
+bool metadata_send(int file_descriptor, const FileMetadata* m);
 FileMetadata* metadata_receive(int file_descriptor, int* ok);
 void file_restore_metadata(const char* path, const FileMetadata* metadata);
 bool file_restore_metadata_fd(int fd, const FileMetadata* metadata);
@@ -233,6 +233,12 @@ int receive_thread(void* pipeline_context) {
          RECEIVE_THREAD_FAIL();
        }
        char* full_path = path_cat(config->receive_root_directory, check_path);
+        if (!full_path) {
+          free(check_path);
+          if (!send_status(file_descriptor, STATUS_ERROR))
+            RECEIVE_THREAD_FAIL();
+          RECEIVE_THREAD_FAIL();
+        }
        struct stat st;
        bool has_old = full_path && file_stat_secure(full_path, &st);
        bool match = has_old && (unsigned long long)st.st_size == check_size &&
@@ -263,9 +269,10 @@ int receive_thread(void* pipeline_context) {
      RECEIVE_THREAD_FAIL();
  }
  if (status == STATUS_MANIFEST) {
-    if (receive_manifest(file_descriptor, config, &status) != 0)
+    if (receive_manifest(file_descriptor, config, &status) != 0) {
      RECEIVE_THREAD_FAIL();
    }
+  }
  if (status != STATUS_FINISHED)
    RECEIVE_THREAD_FAIL();
  mtx_lock(&context->mutex);
@@ -27,6 +27,13 @@ static once_flag bw_mutex_once = ONCE_FLAG_INIT;

 static __thread unsigned long long total_allocated_bytes;

+void protocol_release_memory(size_t charge) {
+  if ((unsigned long long)charge >= total_allocated_bytes)
+    total_allocated_bytes = 0;
+  else
+    total_allocated_bytes -= charge;
+}
+
 void io_set_fds(int read_fd, int write_fd) {
  io_read_fd = read_fd;
  io_write_fd = write_fd;
@@ -43,17 +50,20 @@ static void bw_mutex_init(void) {
 void io_set_bwlimit(unsigned long long bytes_per_sec) {
  call_once(&bw_mutex_once, bw_mutex_init);
  mtx_lock(&bw_mutex);
-  io_bwlimit = bytes_per_sec;
+  io_bwlimit =
+      bytes_per_sec > (unsigned long long)LLONG_MAX ? (unsigned long long)LLONG_MAX : bytes_per_sec;
  bw_tokens = (long long)io_bwlimit;
  clock_gettime(CLOCK_MONOTONIC, &bw_last_refill);
  mtx_unlock(&bw_mutex);
 }

 static void bw_throttle(size_t bytes_written) {
-  if (io_bwlimit == 0)
-    return;
  call_once(&bw_mutex_once, bw_mutex_init);
  mtx_lock(&bw_mutex);
+  if (io_bwlimit == 0) {
+    mtx_unlock(&bw_mutex);
+    return;
+  }

  struct timespec now;
  clock_gettime(CLOCK_MONOTONIC, &now);
@@ -81,6 +91,15 @@ static void bw_throttle(size_t bytes_written) {
  mtx_unlock(&bw_mutex);
 }

+static bool bw_enabled(void) {
+  bool enabled;
+  call_once(&bw_mutex_once, bw_mutex_init);
+  mtx_lock(&bw_mutex);
+  enabled = io_bwlimit != 0;
+  mtx_unlock(&bw_mutex);
+  return enabled;
+}
+
 void io_set_ssl(SSL* ssl) {
  io_ssl = ssl;
 }
@@ -105,6 +124,8 @@ static int deadline_remaining_ms(const struct timespec* deadline) {
 }

 bool send_n_data(int file_descriptor, const void* data, size_t data_size) {
+  if (!data && data_size != 0)
+    return false;
  log_message(LOG_LEVEL_DEBUG, "    Sending n Data: %zu", data_size);
  int fd = io_fd(io_write_fd, file_descriptor);
  struct timespec deadline;
@@ -114,7 +135,7 @@ bool send_n_data(int file_descriptor, const void* data, size_t data_size) {
  ssize_t total_bytes_send = 0;
  while ((size_t)total_bytes_send < data_size) {
    size_t chunk = data_size - total_bytes_send;
-    if (io_bwlimit > 0 && chunk > 65536)
+    if (bw_enabled() && chunk > 65536)
      chunk = 65536;
    struct pollfd pfd = {.fd = fd, .events = wait_events};
    int poll_result = poll(&pfd, 1, deadline_remaining_ms(&deadline));
@@ -144,6 +165,8 @@ bool send_n_data(int file_descriptor, const void* data, size_t data_size) {
    }
    bw_throttle((size_t)bytes_send);
    total_bytes_send += bytes_send;
+    if (io_ssl)
+      wait_events = POLLOUT;
  }
  log_message(LOG_LEVEL_DEBUG, "    Send n Data: %zu", total_bytes_send);
  return true;
@@ -160,6 +183,7 @@ bool receive_n_data(int file_descriptor, void* data, size_t data_size) {
  size_t total_bytes_received = 0;
  short wait_events = POLLIN;
  while (total_bytes_received < data_size) {
+    if (!io_ssl || SSL_pending(io_ssl) == 0) {
      struct pollfd pfd = {.fd = fd, .events = wait_events};
      int poll_result = poll(&pfd, 1, deadline_remaining_ms(&deadline));
      if (poll_result == 0) {
@@ -174,6 +198,7 @@ bool receive_n_data(int file_descriptor, void* data, size_t data_size) {
      /* POLLHUP may accompany the final readable bytes on pipes/sockets. */
      if (pfd.revents & (POLLERR | POLLNVAL))
        return false;
+    }

    ssize_t bytes_received;
    if (io_ssl)
@@ -196,7 +221,9 @@ bool receive_n_data(int file_descriptor, void* data, size_t data_size) {
        log_message(LOG_LEVEL_ERROR, "Could not receive bytes");
      return false;
    }
-    total_bytes_received += bytes_received;
+    total_bytes_received += (size_t)bytes_received;
+    if (io_ssl)
+      wait_events = POLLIN;
  }
  log_message(LOG_LEVEL_DEBUG, "    Received n Data: %zu", total_bytes_received);
  return true;
@@ -247,8 +274,7 @@ char* receive_str(int file_descriptor) {
  size_t size;
  if (!receive_n_data(file_descriptor, &size, sizeof(size_t)))
    return NULL;
-  if (size > MAX_STRING_SIZE || size > SIZE_MAX - 1 ||
-      size + 1 > MAX_CONNECTION_MEMORY - total_allocated_bytes) {
+  if (size > MAX_STRING_SIZE || size > SIZE_MAX - 1) {
    log_message(LOG_LEVEL_ERROR, "String size %zu exceeds maximum %llu", size,
                (unsigned long long)MAX_STRING_SIZE);
    return NULL;
@@ -266,12 +292,13 @@ char* receive_str(int file_descriptor) {
    return NULL;
  }
  data[size] = '\0';
-  total_allocated_bytes += size + 1;
  log_message(LOG_LEVEL_DEBUG, "Received String: %s", data);
  return data;
 }

 bool send_data(int file_descriptor, const Data* data) {
+  if (!data || (!data->data && data->size != 0))
+    return false;
  unsigned long long data_size = data->size;
  if (!send_n_data(file_descriptor, &data_size, sizeof(unsigned long long)))
    return false;
@@ -281,11 +308,11 @@ bool send_data(int file_descriptor, const Data* data) {
  return true;
 }

-Data* receive_data(int file_descriptor) {
+Data* receive_data_limited(int file_descriptor, unsigned long long maximum_size) {
  unsigned long long size = 0;
  if (!receive_n_data(file_descriptor, &size, sizeof(unsigned long long)))
    return NULL;
-  if (size > MAX_DATA_PAYLOAD_SIZE) {
+  if (size > MAX_DATA_PAYLOAD_SIZE || size > maximum_size) {
    log_message(LOG_LEVEL_ERROR, "Data size %llu exceeds maximum %llu", size,
                (unsigned long long)MAX_DATA_PAYLOAD_SIZE);
    return NULL;
@@ -302,16 +329,21 @@ Data* receive_data(int file_descriptor) {
    free(data);
    return NULL;
  }
-  total_allocated_bytes += allocation_size;
  log_message(LOG_LEVEL_DEBUG, "Received %lld data", size);
  Data* result = data_create(data, (size_t)size);
  if (!result) {
    free(data);
-    total_allocated_bytes -= allocation_size;
+    return NULL;
  }
+  total_allocated_bytes += allocation_size;
+  result->protocol_charge = allocation_size;
  return result;
 }

+Data* receive_data(int file_descriptor) {
+  return receive_data_limited(file_descriptor, MAX_DATA_PAYLOAD_SIZE);
+}
+
 bool send_int(int file_descriptor, int data) {
  if (!send_n_data(file_descriptor, &data, sizeof(int)))
    return false;
@@ -10,6 +10,8 @@

 /* Maximum allowed data payload size for receive_data (100 MB) */
 #define MAX_DATA_PAYLOAD_SIZE (100ULL * 1024 * 1024)
+/* Maximum uncompressed file payload accepted by the receiver. */
+#define MAX_RECEIVE_FILE_SIZE (64ULL * 1024 * 1024)

 /* Maximum chunk size (64 MB) — prevents unbounded allocation from the wire */
 #define MAX_CHUNK_SIZE (64ULL * 1024 * 1024)
@@ -46,6 +48,7 @@ bool send_str(int file_descriptor, const char* data);
 char* receive_str(int file_descriptor);
 bool send_data(int file_descriptor, const Data* data);
 Data* receive_data(int file_descriptor);
+Data* receive_data_limited(int file_descriptor, unsigned long long maximum_size);
 bool send_int(int file_descriptor, int data);
 bool receive_int(int file_descriptor, int* data);
 bool send_status(int file_descriptor, Status status);
@@ -105,7 +105,10 @@ static SSL* wrap_fd_with_ssl(int fd, SSL_CTX* ctx, bool is_server, const char* h
    log_message(LOG_LEVEL_ERROR, "Failed to create SSL object");
    return NULL;
  }
-  SSL_set_fd(ssl, fd);
+  if (SSL_set_fd(ssl, fd) != 1) {
+    SSL_free(ssl);
+    return NULL;
+  }

  // Enable hostname verification for client connections when a hostname is provided.
  // Must be done before SSL_connect to take effect during the handshake.
@@ -154,8 +157,10 @@ struct tls_child_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, NULL);
-  if (!ssl)
+  if (!ssl) {
+    io_set_ssl(NULL);
    return;
+  }
  io_set_ssl(ssl);
  ctx->handler(fd);
  SSL_shutdown(ssl);
@@ -184,6 +189,10 @@ bool client_connect_tls(Client* client, char* host, int port, const char* cert_p
  int err = getaddrinfo(host, port_str, &hints, &result);
  if (err != 0 || result == NULL) {
    fprintf(stderr, "Could not resolve host: %s (%s)\n", host, gai_strerror(err));
+    if (client->file_descriptor >= 0) {
+      close(client->file_descriptor);
+      client->file_descriptor = -1;
+    }
    return false;
  }

@@ -216,12 +225,18 @@ bool client_connect_tls(Client* client, char* host, int port, const char* cert_p

  if (!connected) {
    perror("Could not connect to Server!");
+    if (client->file_descriptor >= 0)
+      close(client->file_descriptor);
+    client->file_descriptor = -1;
    return false;
  }

  SSL_CTX* ctx = create_ssl_ctx(false, cert_path, key_path, ca_path);
-  if (!ctx)
+  if (!ctx) {
+    close(client->file_descriptor);
+    client->file_descriptor = -1;
    return false;
+  }
  client->ssl_ctx = ctx;

  // Pass the server hostname for TLS hostname verification (SSL_set1_host
@@ -231,6 +246,8 @@ bool client_connect_tls(Client* client, char* host, int port, const char* cert_p
  if (!ssl) {
    SSL_CTX_free(ctx);
    client->ssl_ctx = NULL;
+    close(client->file_descriptor);
+    client->file_descriptor = -1;
    return false;
  }

@@ -14,14 +14,22 @@
 static int authorized_root_fd = -1;
 static char* authorized_root_path;

-void utils_set_authorized_root(int fd, const char* canonical_path) {
+bool utils_set_authorized_root(int fd, const char* canonical_path) {
+  char* path_copy = canonical_path ? str_dup(canonical_path) : NULL;
+  if (canonical_path && !path_copy) {
+    authorized_root_fd = -1;
+    free(authorized_root_path);
+    authorized_root_path = NULL;
+    return false;
+  }
  authorized_root_fd = fd;
  free(authorized_root_path);
-  authorized_root_path = canonical_path ? str_dup(canonical_path) : NULL;
+  authorized_root_path = path_copy;
+  return true;
 }

 void utils_set_authorized_root_fd(int fd) {
-  utils_set_authorized_root(fd, NULL);
+  (void)utils_set_authorized_root(fd, NULL);
 }

 static bool path_is_within_root(const char* root, const char* path) {
@@ -50,11 +58,15 @@ static int open_authorized_destination(const char* dest_root) {
  char* saveptr = NULL;
  char* component = strtok_r(relative, "/", &saveptr);
  while (component) {
-    if (strcmp(component, ".") == 0 || strcmp(component, "..") == 0) {
+    if (strcmp(component, "..") == 0) {
      free(relative);
      close(dirfd);
      return -1;
    }
+    if (strcmp(component, ".") == 0) {
+      component = strtok_r(NULL, "/", &saveptr);
+      continue;
+    }
    int next = openat(dirfd, component, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
    if (next < 0) {
      free(relative);
@@ -71,52 +83,41 @@ static int open_authorized_destination(const char* dest_root) {
 }

 bool mkdir_r(const char* path) {
-  size_t path_len = strlen(path);
-  char* path_duplicate = malloc(path_len + 1);
-  if (!path_duplicate)
+  if (!path || *path == '\0')
    return false;
-  memcpy(path_duplicate, path, path_len + 1);
-  size_t capacity = path_len + 2;
-  char* path_current = (char*)malloc(capacity * sizeof(char));
-  if (!path_current) {
-    free(path_duplicate);
+  char* duplicate = str_dup(path);
+  if (!duplicate)
+    return false;
+  int dirfd = open(path[0] == '/' ? "/" : ".", O_RDONLY | O_DIRECTORY | O_CLOEXEC | O_NOFOLLOW);
+  if (dirfd < 0) {
+    free(duplicate);
    return false;
  }
-  char* path_current_position = path_current;
-  if (path[0] == '/') {
-    path_current[0] = '/';
-    path_current[1] = '\0';
-    path_current_position += 1;
-  } else {
-    path_current[0] = '\0';
-  }
-  const char* delimiter = "/";
-  char* saveptr;
-  const char* part = strtok_r(path_duplicate, delimiter, &saveptr);
  bool ok = true;
-  while (part != NULL) {
-    size_t part_len = strlen(part);
-    if ((size_t)(path_current_position - path_current) + part_len + 2 > capacity) {
+  char* saveptr = NULL;
+  char* component = strtok_r(duplicate, "/", &saveptr);
+  while (component) {
+    if (strcmp(component, "..") == 0) {
      ok = false;
      break;
    }
-    memcpy(path_current_position, part, part_len);
-    path_current_position += part_len;
-    path_current_position[0] = '/';
-    path_current_position[1] = '\0';
-    path_current_position++;
-    struct stat st;
-    if (stat(path_current, &st) != 0) {
-      if (mkdir(path_current, 0755) != 0) {
-        perror("Could not create directory");
+    if (strcmp(component, ".") != 0) {
+      int next = openat(dirfd, component, O_RDONLY | O_DIRECTORY | O_CLOEXEC | O_NOFOLLOW);
+      if (next < 0 && errno == ENOENT) {
+        if (mkdirat(dirfd, component, 0755) == 0 || errno == EEXIST)
+          next = openat(dirfd, component, O_RDONLY | O_DIRECTORY | O_CLOEXEC | O_NOFOLLOW);
+      }
+      if (next < 0) {
        ok = false;
        break;
      }
+      close(dirfd);
+      dirfd = next;
    }
-    part = strtok_r(NULL, delimiter, &saveptr);
+    component = strtok_r(NULL, "/", &saveptr);
  }
-  free(path_duplicate);
-  free(path_current);
+  close(dirfd);
+  free(duplicate);
  return ok;
 }

@@ -207,15 +208,20 @@ static bool delete_extras_fd(int dirfd, const char* rel_path, ArrayList* manifes
    close(scanfd);
    return false;
  }
-  bool all_removed = true;
  bool operation_ok = true;
  const struct dirent* entry;
  while ((entry = readdir(dir)) != NULL) {
    if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
      continue;
    char* child_rel = path_cat((char*)rel_path, entry->d_name);
+    if (!child_rel) {
+      operation_ok = false;
+      continue;
+    }
    struct stat st;
    if (fstatat(dirfd, entry->d_name, &st, AT_SYMLINK_NOFOLLOW) != 0) {
+      if (errno != ENOENT)
+        operation_ok = false;
      free(child_rel);
      continue;
    }
@@ -229,18 +235,23 @@ static bool delete_extras_fd(int dirfd, const char* rel_path, ArrayList* manifes
      bool child_removed = false;
      if (childfd >= 0) {
        child_removed = delete_extras_fd(childfd, child_rel, manifest, max_delete, deleted_count);
+        if (!child_removed)
+          operation_ok = false;
        close(childfd);
+      } else if (errno != ENOENT) {
+        operation_ok = false;
      }
      if (child_removed && !is_dir_in_manifest(child_rel, manifest)) {
        if (*deleted_count >= max_delete) {
          operation_ok = false;
-        } else if (unlinkat(dirfd, entry->d_name, AT_REMOVEDIR) != 0 && errno != ENOENT) {
+        } else {
+          if (unlinkat(dirfd, entry->d_name, AT_REMOVEDIR) != 0) {
+            if (errno != ENOENT)
              operation_ok = false;
          } else {
            (*deleted_count)++;
          }
-      } else if (!child_removed) {
-        all_removed = false;
+        }
      }
    } else {
      // Check if relative path is in manifest
@@ -257,27 +268,32 @@ static bool delete_extras_fd(int dirfd, const char* rel_path, ArrayList* manifes
          free(child_rel);
          continue;
        }
-        if (unlinkat(dirfd, entry->d_name, 0) != 0 && errno != ENOENT)
+        if (unlinkat(dirfd, entry->d_name, 0) != 0) {
+          if (errno != ENOENT)
            operation_ok = false;
-        else
-          (*deleted_count)++;
-        fprintf(stderr, "  Deleted: %s\n", child_rel);
        } else {
-        all_removed = false;
+          (*deleted_count)++;
+        }
+        fprintf(stderr, "  Deleted: %s\n", child_rel);
      }
    }
    free(child_rel);
  }
  closedir(dir);
-  (void)all_removed;
  return operation_ok;
 }

 bool delete_extras_limited(const char* dest_root, ArrayList* manifest, size_t max_delete) {
+  if (!manifest)
+    return false;
  int rootfd;
  if (authorized_root_fd >= 0) {
-    rootfd =
-        authorized_root_path ? open_authorized_destination(dest_root) : dup(authorized_root_fd);
+    if (authorized_root_path)
+      rootfd = open_authorized_destination(dest_root);
+    else if (dest_root == NULL)
+      rootfd = dup(authorized_root_fd);
+    else
+      rootfd = -1;
  } else {
    rootfd = open(dest_root, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
  }
@@ -296,10 +312,10 @@ bool delete_extras(const char* dest_root, ArrayList* manifest) {

 bool has_path_traversal(const char* path) {
  if (!path)
-    return false;
+    return true;
  char* dup = str_dup(path);
  if (!dup)
-    return false;
+    return true;
  char* saveptr;
  const char* part = strtok_r(dup, "/", &saveptr);
  while (part) {
@@ -327,6 +343,8 @@ char* path_cat(const char* path1, const char* path2) {
    offset = 1;
    path2_len -= 1;
  }
+  if (path1_len > SIZE_MAX - path2_len - 2)
+    return NULL;
  char* new_path = malloc(path1_len + path2_len + 2);
  if (new_path == NULL)
    return NULL;
@@ -11,7 +11,9 @@ char* path_cat(const char* path1, const char* path2);
 bool glob_match(const char* pattern, const char* str);
 bool delete_extras(const char* dest_root, ArrayList* manifest);
 bool delete_extras_limited(const char* dest_root, ArrayList* manifest, size_t max_delete);
-void utils_set_authorized_root(int fd, const char* canonical_path);
+bool utils_set_authorized_root(int fd, const char* canonical_path);
+/* The fd-only compatibility form is fail-closed for path-based operations;
+ * callers should use utils_set_authorized_root with the canonical identity. */
 void utils_set_authorized_root_fd(int fd);
 bool has_path_traversal(const char* path);

@@ -12,11 +12,15 @@ static void test_destroyer(void* item) {
 void test_array_list() {
  ArrayList* list = array_list_create(free);
  EXPECT_NOT_NULL(list);
+  if (!list)
+    return;
  EXPECT_EQ_INT(list->size, 0);
  EXPECT_EQ_INT(list->capacity, 100);

  // Test adding
  int* val1 = malloc(sizeof(int));
+  if (!val1)
+    return;
  *val1 = 42;
  array_list_add(list, val1);
  EXPECT_EQ_INT(list->size, 1);
@@ -26,6 +30,8 @@ void test_array_list() {
  // Initial capacity is 100. Let's add 105 elements.
  for (int i = 0; i < 105; i++) {
    int* val = malloc(sizeof(int));
+    if (!val)
+      return;
    *val = i;
    array_list_add(list, val);
  }
@@ -13,6 +13,8 @@ static void test_data_compress_decompress_roundtrip() {
  size_t len = strlen(original);

  char* buf = malloc(len);
+  if (!buf)
+    return;
  memcpy(buf, original, len);
  Data* original_data = data_create(buf, len);
  EXPECT_NOT_NULL(original_data);
@@ -14,6 +14,8 @@
 static Data* random_data(int min_size, int max_size) {
  int size = min_size + rand() % (max_size - min_size + 1);
  char* buf = malloc(size);
+  if (!buf)
+    return NULL;
  for (int i = 0; i < size; i++)
    buf[i] = (char)(rand() % 256);
  return data_create(buf, size);
@@ -23,10 +25,16 @@ static void test_property_compress_roundtrip() {
  for (int iter = 0; iter < 10; iter++) {
    Data* original = random_data(1, 10000);
    EXPECT_NOT_NULL(original);
+    if (!original)
+      return;

    size_t orig_size = original->size;
    void* orig_copy = malloc(orig_size);
    EXPECT_NOT_NULL(orig_copy);
+    if (!orig_copy) {
+      data_destroy(original);
+      return;
+    }
    memcpy(orig_copy, original->data, orig_size);

    Data* compressed = data_compress(original, 3);
@@ -81,6 +89,8 @@ static void test_property_chunk_roundtrip() {

    int content_len = 1 + rand() % 4096;
    char* content = malloc(content_len);
+    if (!content)
+      return;
    for (int i = 0; i < content_len; i++)
      content[i] = (char)(rand() % 256);

@@ -119,9 +119,13 @@ static void test_queue_destroyer() {
  destroyer_calls = 0;
  Queue* q = queue_create(5, my_destroyer);
  EXPECT_NOT_NULL(q);
+  if (!q)
+    return;

  for (int i = 0; i < 3; i++) {
    int* val = malloc(sizeof(int));
+    if (!val)
+      break;
    *val = i;
    queue_enqueue(q, val);
  }
@@ -181,6 +185,8 @@ static void test_queue_multithreaded() {

  for (int i = 1; i <= 100; i++) {
    int* val = malloc(sizeof(int));
+    if (!val)
+      break;
    *val = i;
    queue_enqueue_multithreaded(q, val, &mutex, &cnd_empty, &cnd_full);
  }
@@ -32,6 +32,8 @@ static int mpmc_producer_func(void* arg) {
  ProducerCtx* ctx = (ProducerCtx*)arg;
  for (int i = 1; i <= ITEMS_PER_PRODUCER; i++) {
    int* val = malloc(sizeof(int));
+    if (!val)
+      return thrd_error;
    *val = ctx->producer_id * ITEMS_PER_PRODUCER + i;
    queue_enqueue_multithreaded(ctx->q, val, ctx->mutex, ctx->cnd_empty, ctx->cnd_full);
  }
@@ -121,6 +123,8 @@ static int bp_producer_func(void* arg) {
  BackpressureCtx* ctx = (BackpressureCtx*)arg;
  for (int i = 0; i < 5; i++) {
    int* val = malloc(sizeof(int));
+    if (!val)
+      return thrd_error;
    *val = i + 1;
    queue_enqueue_multithreaded(ctx->q, val, ctx->mutex, ctx->cnd_empty, ctx->cnd_full);
    ctx->items_sent++;
@@ -191,9 +195,13 @@ static void test_queue_rapid_create_destroy() {
  for (int i = 0; i < 100; i++) {
    Queue* q = queue_create(4, free);
    EXPECT_NOT_NULL(q);
+    if (!q)
+      return;

    for (int j = 0; j < 3; j++) {
      int* val = malloc(sizeof(int));
+      if (!val)
+        break;
      *val = j;
      queue_enqueue(q, val);
    }