Merge dev into human codebase evaluation

src/shared/config.c

@@ -45,20 +45,59 @@ static void config_set_defaults(Config* config) {
   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;
   config->follow_symlinks = false;
   config->partial = false;
   config->copy_links = false;
   config->safe_links = false;
   config->copy_unsafe_links = false;
+  config->preserve_hard_links = false;
+  config->preserve_acls = false;
+  config->preserve_xattrs = false;
+  config->preserve_devices = false;
   config->preserve_sparse = false;
+  config->itemize_changes = false;
+  config->out_format = NULL;
+  config->info_level = 0;
+  config->debug_level = 0;
+  config->list_only = false;
+  config->human_readable = false;
+  config->update = false;
   config->inplace = false;
+  config->append = false;
+  config->append_verify = false;
+  config->delete_excluded = false;
+  config->delete_after = false;
+  config->max_delete = 0;
+  config->filters = NULL;
+  config->files_from = NULL;
+  config->cvs_exclude = false;
+  config->prune_empty_dirs = false;
+  config->relative = false;
+  config->rsh_command = NULL;
+  config->rsync_path = NULL;
+  config->temp_dir = NULL;
+  config->compare_dest = NULL;
+  config->copy_dest = NULL;
+  config->link_dest = NULL;
   config->partial_dir = NULL;
   config->suffix = NULL;
+  config->delete_before = false;
+  config->address = NULL;
+  config->bind_address = NULL;
+  config->ipv6 = false;
+  config->ipv4 = false;
+  config->daemon = false;
+  config->daemon_config = NULL;
+  config->server_mode = false;
+  config->checksum = false;
+  config->compress_choice = NULL;
 }
 
 Config* config_create(void) {
@@ -114,8 +153,23 @@ void config_delete(Config* config) {
   free(config->tls_ca);
   free(config->backup_dir);
   free(config->server_host);
+  free(config->out_format);
+  free(config->files_from);
+  free(config->rsh_command);
+  free(config->rsync_path);
+  free(config->temp_dir);
+  free(config->compare_dest);
+  free(config->copy_dest);
+  free(config->link_dest);
   free(config->partial_dir);
   free(config->suffix);
+  free(config->address);
+  free(config->bind_address);
+  free(config->daemon_config);
+  free(config->compress_choice);
+  if (config->filters) {
+    array_list_delete(config->filters);
+  }
   free(config);
 }
 
@@ -124,11 +178,10 @@ void config_delete(Config* config) {
  * use_chunk_serialization, use_compression, use_metadata, compression_level, chunk_size,
  * use_sendfile, use_delete, use_incremental, use_delta, delta_block_size, delta_max_file_size,
  * backup, backup_dir, follow_symlinks, copy_links, safe_links, copy_unsafe_links,
- * obsolete metadata flags, preserve_sparse, obsolete transfer flags, inplace, obsolete delete
- * flags, obsolete path options, partial, partial_dir, suffix, obsolete checksum options, status
- *
- * Obsolete fields remain as zero/empty compatibility slots. They must be consumed in this order
- * until the protocol version is intentionally changed.
+ * preserve_hard_links, preserve_acls, preserve_xattrs, preserve_devices, preserve_sparse,
+ * update, inplace, append, append_verify, delete_excluded, delete_after, max_delete, relative,
+ * prune_empty_dirs, temp_dir, partial, partial_dir, suffix, delete_before, checksum,
+ * compress_choice, status
  */
 bool config_send(int file_descriptor, const Config* config) {
   if (!send_str(file_descriptor, config->version))
@@ -175,36 +228,35 @@ bool config_send(int file_descriptor, const Config* config) {
     return false;
   if (!send_int(file_descriptor, config->copy_unsafe_links))
     return false;
-  if (!send_int(file_descriptor, 0))
+  if (!send_int(file_descriptor, config->preserve_hard_links))
     return false;
-  if (!send_int(file_descriptor, 0))
+  if (!send_int(file_descriptor, config->preserve_acls))
     return false;
-  if (!send_int(file_descriptor, 0))
+  if (!send_int(file_descriptor, config->preserve_xattrs))
     return false;
-  if (!send_int(file_descriptor, 0))
+  if (!send_int(file_descriptor, config->preserve_devices))
     return false;
   if (!send_int(file_descriptor, config->preserve_sparse))
     return false;
-  if (!send_int(file_descriptor, 0))
+  if (!send_int(file_descriptor, config->update))
     return false;
   if (!send_int(file_descriptor, config->inplace))
     return false;
-  if (!send_int(file_descriptor, 0))
+  if (!send_int(file_descriptor, config->append))
     return false;
-  if (!send_int(file_descriptor, 0))
+  if (!send_int(file_descriptor, config->append_verify))
     return false;
-  if (!send_int(file_descriptor, 0))
+  if (!send_int(file_descriptor, config->delete_excluded))
     return false;
-  if (!send_int(file_descriptor, 0))
+  if (!send_int(file_descriptor, config->delete_after))
     return false;
-  int obsolete_int = 0;
-  if (!send_n_data(file_descriptor, &obsolete_int, sizeof(obsolete_int)))
+  if (!send_n_data(file_descriptor, &config->max_delete, sizeof(config->max_delete)))
     return false;
-  if (!send_int(file_descriptor, 0))
+  if (!send_int(file_descriptor, config->relative))
     return false;
-  if (!send_int(file_descriptor, 0))
+  if (!send_int(file_descriptor, config->prune_empty_dirs))
     return false;
-  if (!send_str(file_descriptor, ""))
+  if (!send_str(file_descriptor, config->temp_dir ? config->temp_dir : ""))
     return false;
   if (!send_int(file_descriptor, config->partial))
     return false;
@@ -212,11 +264,11 @@ bool config_send(int file_descriptor, const Config* config) {
     return false;
   if (!send_str(file_descriptor, config->suffix ? config->suffix : ""))
     return false;
-  if (!send_int(file_descriptor, 0))
+  if (!send_int(file_descriptor, config->delete_before))
     return false;
-  if (!send_int(file_descriptor, 0))
+  if (!send_int(file_descriptor, config->checksum))
     return false;
-  if (!send_str(file_descriptor, ""))
+  if (!send_str(file_descriptor, config->compress_choice ? config->compress_choice : ""))
     return false;
   Status status;
   if (!receive_status(file_descriptor, &status))
@@ -322,39 +374,48 @@ Config* config_receive(int file_descriptor) {
   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))
     goto error;
+  config->relative = tmp;
   if (!receive_int(file_descriptor, &tmp))
     goto error;
-  int obsolete_int = 0;
-  if (!receive_n_data(file_descriptor, &obsolete_int, sizeof(obsolete_int)))
+  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))
-    goto error;
-  if (!receive_int(file_descriptor, &tmp))
-    goto error;
-  char* obsolete_string = receive_str(file_descriptor);
-  if (obsolete_string == NULL)
-    goto error;
-  free(obsolete_string);
   if (!receive_int(file_descriptor, &tmp))
     goto error;
   config->partial = tmp;
@@ -366,12 +427,19 @@ Config* config_receive(int file_descriptor) {
     goto error;
   if (!receive_int(file_descriptor, &tmp))
     goto error;
+  config->delete_before = tmp;
   if (!receive_int(file_descriptor, &tmp))
     goto error;
-  obsolete_string = receive_str(file_descriptor);
-  if (obsolete_string == NULL)
+  config->checksum = tmp;
+  config->compress_choice = receive_str(file_descriptor);
+  if (config->compress_choice == NULL)
     goto error;
-  free(obsolete_string);
+  if (config->compress_choice[0] != '\0' && strcmp(config->compress_choice, "zstd") != 0 &&
+      strcmp(config->compress_choice, "none") != 0) {
+    fprintf(stderr, "Unsupported compression choice: %s\n", config->compress_choice);
+    send_status(file_descriptor, STATUS_ERROR);
+    goto error;
+  }
   if (!send_status(file_descriptor, STATUS_OK))
     goto error;
   return config;
@@ -382,8 +450,10 @@ error:
   free(config->receive_root_directory);
   free(config->server_host);
   free(config->backup_dir);
+  free(config->temp_dir);
   free(config->partial_dir);
   free(config->suffix);
+  free(config->compress_choice);
   free(config);
   return NULL;
 }

src/shared/config.h

@@ -1,6 +1,7 @@
 #ifndef CONFIG_H
 #define CONFIG_H
 
+#include "array_list.h"
 #include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
@@ -44,11 +45,13 @@ typedef struct Config {
   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;
   bool follow_symlinks;
   bool partial;
 
@@ -57,9 +60,46 @@ typedef struct Config {
   bool safe_links;
   bool copy_unsafe_links;
 
+  // Issue #121: Extended metadata preservation
+  bool preserve_hard_links;
+  bool preserve_acls;
+  bool preserve_xattrs;
+  bool preserve_devices;
   bool preserve_sparse;
 
+  // Issue #122: Output/logging options
+  bool itemize_changes;
+  char* out_format;
+  int info_level;
+  int debug_level;
+  bool list_only;
+  bool human_readable;
+
+  // Issue #127: Transfer modes
+  bool update;
   bool inplace;
+  bool append;
+  bool append_verify;
+
+  // Issue #128: Extended delete options
+  bool delete_excluded;
+  bool delete_after;
+  int max_delete;
+
+  // Issue #129: Advanced file selection
+  ArrayList* filters;
+  char* files_from;
+  bool cvs_exclude;
+  bool prune_empty_dirs;
+  bool relative;
+
+  // Issue #130: Remote shell/connection options
+  char* rsh_command;
+  char* rsync_path;
+  char* temp_dir;
+  char* compare_dest;
+  char* copy_dest;
+  char* link_dest;
 
   // PR #174: Partial transfer resumption
   char* partial_dir;
@@ -67,10 +107,28 @@ typedef struct Config {
   // PR #178: Backup versioning
   char* suffix;
 
+  // PR #179: Delete policies
+  bool delete_before;
+
+  // PR #181: IPv6 and bind address
+  char* address;
+  char* bind_address;
+  bool ipv6;
+  bool ipv4;
+
+  // PR #182: Daemon/server mode
+  bool daemon;
+  char* daemon_config;
+  bool server_mode;
+
+  // PR #183: Checksum comparison
+  bool checksum;
+
+  // PR #184: Compression algorithm negotiation
+  char* compress_choice;
 } Config;
 
-/* This version must be bumped whenever config_send / config_receive wire format changes. */
-#define PROTOCOL_VERSION "2.1.0"
+#define PROTOCOL_VERSION "2.2.0"
 #define DEFAULT_CHUNK_SIZE (10 * 1024 * 1024)
 
 Config* config_create(void);

src/shared/delta.c

@@ -27,6 +27,10 @@ uint32_t delta_xxhash32(const void* data, uint32_t len) {
   return XXH32(data, len, 0);
 }
 
+uint64_t delta_xxhash64(const void* data, size_t len) {
+  return XXH64(data, len, 0);
+}
+
 DeltaSignature* delta_signature_create(const void* old_file_data, uint64_t old_file_size,
                                        uint32_t block_size) {
   if (old_file_data == NULL || old_file_size == 0 || block_size == 0)

src/shared/delta.h

@@ -72,5 +72,6 @@ bool delta_is_worthwhile(const Delta* delta, uint64_t new_file_size);
 
 uint32_t delta_adler32(const void* data, uint32_t len);
 uint32_t delta_xxhash32(const void* data, uint32_t len);
+uint64_t delta_xxhash64(const void* data, size_t len);
 
 #endif

src/shared/file.c

@@ -2,6 +2,8 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <libgen.h>
+#include <limits.h>
+#include <poll.h>
 #include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -9,6 +11,7 @@
 #include <sys/sendfile.h>
 #include <sys/stat.h>
 #include <unistd.h>
+#include <time.h>
 
 #include "compression.h"
 #include "delta.h"
@@ -20,7 +23,22 @@
 #include "protocol.h"
 #include "utils.h"
 
+bool file_checksum(File* file, uint64_t* checksum) {
+  if (!file || !checksum || !file->data)
+    return false;
+  if (file->data->size == 0) {
+    *checksum = delta_xxhash64("", 0);
+    return true;
+  }
+  if (!file->data->data && !file_load_data(file))
+    return false;
+  *checksum = delta_xxhash64(file->data->data, file->data->size);
+  return true;
+}
+
 File* file_create(const char* path) {
+  if (!path)
+    return NULL;
   File* file = (File*)malloc(sizeof(File));
   if (file == NULL) {
     perror("ERROR: Could not allocate memory for file struct");
@@ -86,6 +104,8 @@ bool file_load_data(File* file) {
   if (file == NULL)
     return false;
   if (file->data->data == NULL) {
+    if (file->data->size == 0)
+      return true;
     file->data->data = malloc(file->data->size);
     if (file->data->data == NULL) {
       perror("Could not allocate memory for file data");
@@ -105,6 +125,8 @@ 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)
+    return false;
   const Data* data_to_send = file->data;
   Data* compressed_data = NULL;
   if (compression_level > 0 && !compression_should_skip(file->path)) {
@@ -131,22 +153,56 @@ 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, const Config* config) {
+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);
+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 n = strlen(root);
+  return strncmp(root, path, n) == 0 && (path[n] == '\0' || path[n] == '/');
+}
+
+bool file_save_to_disk(const char* root_directory, const File* file, const Config* config) {
   bool backup_enabled = config && config->backup;
   bool inplace = config && config->inplace;
   bool sparse = config && config->preserve_sparse;
   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;
 
-  if (has_path_traversal(file->path)) {
-    log_message(LOG_LEVEL_ERROR, "Path traversal detected in file path: %s", file->path);
+  if (!file || !file->path || !file->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))) {
+    log_message(LOG_LEVEL_ERROR, "Invalid file or path received");
+    return false;
+  }
+
+  /* These options arrive from the client.  They are names below the server
+     root, never independent filesystem roots. */
+  if ((backup_dir && (backup_dir[0] == '/' || has_path_traversal(backup_dir))) ||
+      (partial_dir && (partial_dir[0] == '/' || has_path_traversal(partial_dir))))
+    return false;
+  if (backup_dir && !(confined_backup = path_cat(root_directory, backup_dir)))
+    return false;
+  if (partial_dir && !(confined_partial = path_cat(root_directory, partial_dir))) {
+    free(confined_backup);
     return false;
   }
 
   char* resolved_root = NULL;
   const char* actual_root =
-      (partial_dir && config && config->partial) ? partial_dir : root_directory;
+      (partial_dir && config && config->partial) ? confined_partial : root_directory;
   resolved_root = realpath(actual_root, NULL);
   if (resolved_root == NULL) {
     if (mkdir_r(actual_root)) {
@@ -155,27 +211,56 @@ bool file_save_to_disk(const char* root_directory, File* file, const Config* con
   }
   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);
   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 &&
+        destination_stat.st_mtime > file->metadata->mtime_sec) {
+      free(resolved_root);
+      free(confined_backup);
+      free(confined_partial);
+      free(disk_path);
+      return true;
+    }
+  }
+
   if (backup_enabled) {
     struct stat backup_stat;
     if (stat(disk_path, &backup_stat) == 0) {
       char* backup_path = NULL;
       if (backup_dir) {
-        char* resolved_backup_dir = realpath(backup_dir, NULL);
+        char* resolved_backup_dir = realpath(confined_backup, NULL);
         if (!resolved_backup_dir) {
-          mkdir_r(backup_dir);
-          resolved_backup_dir = realpath(backup_dir, NULL);
+          mkdir_r(confined_backup);
+          resolved_backup_dir = realpath(confined_backup, NULL);
         }
         if (resolved_backup_dir) {
-          backup_path = path_cat(resolved_backup_dir, file->path);
+          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);
         }
       }
@@ -195,7 +280,14 @@ bool file_save_to_disk(const char* root_directory, File* file, const Config* con
           mkdir_r(bdir);
           free(backup_dir_path);
         }
-        rename(disk_path, backup_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;
+        }
         free(backup_path);
       }
     }
@@ -203,6 +295,8 @@ bool file_save_to_disk(const char* root_directory, File* file, const Config* con
 
   char* dir_dup = str_dup(disk_path);
   if (!dir_dup) {
+    free(confined_backup);
+    free(confined_partial);
     free(resolved_root);
     free(disk_path);
     return false;
@@ -210,6 +304,8 @@ bool file_save_to_disk(const char* root_directory, File* file, const Config* con
   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;
@@ -218,6 +314,8 @@ bool file_save_to_disk(const char* root_directory, File* file, const Config* con
   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;
@@ -228,6 +326,8 @@ bool file_save_to_disk(const char* root_directory, File* file, const Config* con
       (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;
@@ -235,31 +335,14 @@ bool file_save_to_disk(const char* root_directory, File* file, const Config* con
   free(resolved_dir);
   free(resolved_root);
 
-  bool ok = to_disk(disk_path, file->data->data, file->data->size, inplace, sparse);
-  if (ok)
-    file_restore_metadata(disk_path, file->metadata);
+  bool ok = to_disk_secure(disk_path, file->data->data, file->data->size, inplace, sparse,
+                           file->metadata);
+  free(confined_backup);
+  free(confined_partial);
   free(disk_path);
   return ok;
 }
 
-static void* old_data_from_path(const char* full_path, unsigned long long old_size) {
-  void* data = malloc((size_t)old_size);
-  if (!data)
-    return NULL;
-  FILE* fp = fopen(full_path, "rb");
-  if (!fp) {
-    free(data);
-    return NULL;
-  }
-  size_t nread = fread(data, 1, (size_t)old_size, fp);
-  fclose(fp);
-  if (nread != (size_t)old_size) {
-    free(data);
-    return NULL;
-  }
-  return data;
-}
-
 static File* receive_delta_file(int fd, const Config* config, const char* check_path,
                                 void* old_data, unsigned long long old_size) {
   if (!old_data)
@@ -423,12 +506,18 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
 
   unsigned long long check_size;
   long long check_mtime;
+  uint64_t check_checksum = 0;
   if (!receive_n_data(fd, &check_size, sizeof(check_size)) ||
       !receive_n_data(fd, &check_mtime, sizeof(check_mtime))) {
     free(check_path);
     send_status(fd, STATUS_ERROR);
     return NULL;
   }
+  if (config->checksum && !receive_n_data(fd, &check_checksum, sizeof(check_checksum))) {
+    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);
@@ -439,13 +528,53 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
 
   char* full_path = path_cat(config->receive_root_directory, check_path);
   struct stat st;
-  bool has_old_file = (full_path && lstat(full_path, &st) == 0);
+  bool has_old_file = false;
+  int old_fd = -1;
+  if (full_path) {
+    char* leaf = NULL;
+    int parent_fd = open_secure_parent(full_path, &leaf);
+    if (parent_fd >= 0) {
+      old_fd = openat(parent_fd, leaf, O_RDONLY | O_CLOEXEC | O_NOFOLLOW);
+      free(leaf);
+      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_data = malloc((size_t)old_size);
+    if (old_data) {
+      size_t got = 0;
+      while (got < (size_t)old_size) {
+        ssize_t n = read(old_fd, (char*)old_data + got, (size_t)old_size - got);
+        if (n <= 0) {
+          free(old_data);
+          old_data = NULL;
+          break;
+        }
+        got += (size_t)n;
+      }
+    }
+  }
+  if (old_fd >= 0) {
+    close(old_fd);
+  }
 
-  bool match = has_old_file && (unsigned long long)st.st_size == check_size &&
-               (long long)st.st_mtime == check_mtime;
+  bool match = has_old_file && (unsigned long long)st.st_size == check_size;
+  if (match && config->checksum) {
+    uint64_t old_checksum = old_size == 0 ? delta_xxhash64("", 0) : 0;
+    if (old_data)
+      old_checksum = delta_xxhash64(old_data, (size_t)old_size);
+    match = (old_size == 0 || old_data) && old_checksum == check_checksum;
+    free(old_data);
+    old_data = NULL;
+  } else if (match) {
+    match = (long long)st.st_mtime == check_mtime;
+  }
 
   if (match) {
+    free(old_data);
     if (!send_status(fd, STATUS_OK)) {
       free(full_path);
       free(check_path);
@@ -461,13 +590,15 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
                    delta_should_attempt(old_size, check_size, config->delta_max_file_size);
 
   if (try_delta) {
-    void* old_data = old_data_from_path(full_path, old_size);
     File* delta_file = receive_delta_file(fd, config, check_path, old_data, old_size);
+    old_data = NULL; /* receive_delta_file consumes the snapshot on every path */
     if (delta_file) {
       free(full_path);
       free(check_path);
       return delta_file;
     }
+    free(old_data);
+    old_data = NULL;
     try_delta = false;
   }
 
@@ -520,8 +651,144 @@ File* receive_incremental_check(int fd, const Config* config, bool* skipped) {
   return file;
 }
 
+static int open_secure_parent(const char* path, char** leaf_out) {
+  char* copy = str_dup(path);
+  if (!copy)
+    return -1;
+  char* parent = dirname(copy);
+  const char* slash = strrchr(path, '/');
+  char* leaf = str_dup(slash ? slash + 1 : path);
+  if (!leaf) {
+    free(copy);
+    return -1;
+  }
+  int fd;
+  if (authorized_root_fd >= 0 && authorized_root_path && path[0] == '/' &&
+      path_is_within_root(authorized_root_path, path)) {
+    fd = dup(authorized_root_fd);
+    size_t root_len = strlen(authorized_root_path);
+    char* relative = str_dup(path + root_len);
+    if (!relative) {
+      free(copy);
+      free(leaf);
+      close(fd);
+      return -1;
+    }
+    free(copy);
+    copy = relative;
+    parent = dirname(copy);
+  } else {
+    fd = (parent[0] == '/') ? open("/", O_RDONLY | O_DIRECTORY | O_CLOEXEC)
+                            : open(".", O_RDONLY | O_DIRECTORY | O_CLOEXEC);
+  }
+  if (fd < 0) {
+    free(copy);
+    free(leaf);
+    return -1;
+  }
+  char* save = NULL;
+  char* component = strtok_r(parent, "/", &save);
+  while (component) {
+    if (strcmp(component, ".") != 0 && strcmp(component, "..") != 0) {
+      int next = openat(fd, component, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
+      if (next < 0 && errno == ENOENT && mkdirat(fd, component, 0755) == 0)
+        next = openat(fd, component, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
+      if (next < 0) {
+        close(fd);
+        free(copy);
+        free(leaf);
+        return -1;
+      }
+      close(fd);
+      fd = next;
+    }
+    component = strtok_r(NULL, "/", &save);
+  }
+  free(copy);
+  *leaf_out = leaf;
+  return fd;
+}
+
+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);
+  int new_parent = open_secure_parent(new_path, &new_leaf);
+  bool ok = old_parent >= 0 && new_parent >= 0 &&
+            renameat(old_parent, old_leaf, new_parent, new_leaf) == 0;
+  if (old_parent >= 0)
+    close(old_parent);
+  if (new_parent >= 0)
+    close(new_parent);
+  free(old_leaf);
+  free(new_leaf);
+  return ok;
+}
+
+static bool write_all(int fd, const void* data, unsigned long long size) {
+  const unsigned char* p = data;
+  unsigned long long done = 0;
+  while (done < size) {
+    ssize_t n = write(fd, p + done, (size_t)(size - done));
+    if (n < 0 && errno == EINTR)
+      continue;
+    if (n <= 0)
+      return false;
+    done += (unsigned long long)n;
+  }
+  return true;
+}
+
+static bool to_disk_secure(const char* path, const void* data, unsigned long long data_size,
+                           bool inplace, bool sparse, const FileMetadata* metadata) {
+  char* leaf = NULL;
+  int dirfd = open_secure_parent(path, &leaf);
+  if (dirfd < 0)
+    return false;
+  int fd = -1;
+  bool ok = false;
+  if (inplace) {
+    fd = openat(dirfd, leaf, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC | O_NOFOLLOW, 0644);
+    if (fd >= 0) {
+      if (!sparse || data_size == 0 || ftruncate(fd, (off_t)data_size) == 0)
+        ok = write_all(fd, data, data_size);
+      if (ok && metadata)
+        ok = file_restore_metadata_fd(fd, metadata);
+    }
+  } else {
+    char tmp[NAME_MAX];
+    for (unsigned int i = 0; i < 100 && !ok; ++i) {
+      snprintf(tmp, sizeof(tmp), ".%s.tmp.%ld.%u", leaf, (long)getpid(), i);
+      fd = openat(dirfd, tmp, O_WRONLY | O_CREAT | O_EXCL | O_CLOEXEC | O_NOFOLLOW, 0600);
+      if (fd < 0)
+        continue;
+      if (sparse && data_size > 0)
+        ok = ftruncate(fd, (off_t)data_size) == 0;
+      if (ok || (!sparse || data_size == 0))
+        ok = write_all(fd, data, data_size);
+      if (ok && metadata)
+        ok = file_restore_metadata_fd(fd, metadata);
+      if (close(fd) != 0)
+        ok = false;
+      fd = -1;
+      if (ok && renameat(dirfd, tmp, dirfd, leaf) != 0)
+        ok = false;
+      if (!ok)
+        unlinkat(dirfd, tmp, 0);
+    }
+  }
+  if (fd >= 0)
+    close(fd);
+  close(dirfd);
+  free(leaf);
+  return ok;
+}
+
 bool to_disk(const char* path, const void* data, unsigned long long data_size, bool inplace,
              bool sparse) {
+  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;
 
@@ -625,6 +892,8 @@ done:
 
 bool file_send_sendfile(File* file, int file_descriptor, bool use_metadata, int compression_level,
                         bool send_path) {
+  if (!file || !file->path || !file->data)
+    return false;
   if (compression_level > 0)
     return file_send_single_calls(file, file_descriptor, use_metadata, compression_level,
                                   send_path);
@@ -641,13 +910,56 @@ bool file_send_sendfile(File* file, int file_descriptor, bool use_metadata, int
   }
 
   unsigned long long file_size = file->data->size;
+  struct stat source_stat;
+  if (fstat(fd, &source_stat) != 0 || !S_ISREG(source_stat.st_mode) ||
+      (unsigned long long)source_stat.st_size < file_size) {
+    close(fd);
+    return false;
+  }
   if (!send_n_data(file_descriptor, &file_size, sizeof(unsigned long long))) {
     close(fd);
     return false;
   }
 
+  /* sendfile cannot encrypt TLS records.  Keep the framing identical but
+     route encrypted transfers through the deadline-aware IO layer. */
+  if (io_get_ssl() != NULL) {
+    unsigned char buffer[64 * 1024];
+    unsigned long long remaining = file_size;
+    bool ok = true;
+    while (remaining > 0) {
+      size_t want = remaining > sizeof(buffer) ? sizeof(buffer) : (size_t)remaining;
+      ssize_t got = read(fd, buffer, want);
+      if (got <= 0 || !send_n_data(file_descriptor, buffer, (size_t)got)) {
+        ok = false;
+        break;
+      }
+      remaining -= (unsigned long long)got;
+    }
+    close(fd);
+    return ok;
+  }
+
   off_t offset = 0;
+  struct timespec deadline;
+  clock_gettime(CLOCK_MONOTONIC, &deadline);
+  deadline.tv_sec += 60;
   while ((unsigned long long)offset < file_size) {
+    struct timespec now;
+    clock_gettime(CLOCK_MONOTONIC, &now);
+    long long remaining = (long long)(deadline.tv_sec - now.tv_sec) * 1000LL +
+                          (deadline.tv_nsec - now.tv_nsec) / 1000000LL;
+    if (remaining <= 0) {
+      close(fd);
+      return false;
+    }
+    struct pollfd pfd = {.fd = file_descriptor, .events = POLLOUT};
+    int timeout = remaining > INT_MAX ? INT_MAX : (int)remaining;
+    int polled = poll(&pfd, 1, timeout);
+    if (polled <= 0 || (pfd.revents & (POLLERR | POLLHUP | POLLNVAL))) {
+      close(fd);
+      return false;
+    }
     ssize_t sent = sendfile(file_descriptor, fd, &offset, file_size - offset);
     if (sent == -1) {
       if (errno == EAGAIN || errno == EINTR)
@@ -656,6 +968,10 @@ bool file_send_sendfile(File* file, int file_descriptor, bool use_metadata, int
       close(fd);
       return false;
     }
+    if (sent == 0) {
+      close(fd);
+      return false;
+    }
   }
 
   close(fd);
@@ -666,6 +982,11 @@ File* file_receive(const Config* config, int file_descriptor) {
   char* path = receive_str(file_descriptor);
   if (path == NULL)
     return NULL;
+  if (path[0] == '\0' || has_path_traversal(path)) {
+    log_message(LOG_LEVEL_ERROR, "Invalid received file path: %s", path);
+    free(path);
+    return NULL;
+  }
   File* file = file_create(path);
   free(path);
   if (file == NULL)
@@ -714,21 +1035,40 @@ size_t file_content_to_buffer(File* file) {
 }
 
 int receive_manifest(int fd, const Config* config, int* next_status) {
+  int received_status = STATUS_ERROR;
+  int* status_out = next_status ? next_status : &received_status;
   int count;
   if (!receive_int(fd, &count))
     return -1;
-  ArrayList* manifest = array_list_create(free);
-  if (manifest) {
-    for (int i = 0; i < count; i++) {
-      char* s = receive_str(fd);
-      if (s)
-        array_list_add(manifest, s);
-    }
-    fprintf(stderr, "Deleting files not in manifest...\n");
-    delete_extras(config->receive_root_directory, manifest);
-    array_list_delete(manifest);
-  }
-  if (!receive_status(fd, next_status))
+  if (count < 0 || count > MAX_MANIFEST_ENTRIES)
     return -1;
-  return 0;
+  ArrayList* manifest = array_list_create(free);
+  if (!manifest)
+    return -1;
+  size_t manifest_bytes = 0;
+  for (int i = 0; i < count; i++) {
+    char* s = receive_str(fd);
+    size_t entry_size = s ? strlen(s) : 0;
+    if (!s || s[0] == '\0' || s[0] == '/' || has_path_traversal(s) ||
+        entry_size > MAX_MANIFEST_BYTES - manifest_bytes ||
+        (manifest_bytes += entry_size) > MAX_MANIFEST_BYTES || !array_list_add(manifest, s)) {
+      free(s);
+      array_list_delete(manifest);
+      return -1;
+    }
+  }
+  if (!receive_status(fd, status_out)) {
+    array_list_delete(manifest);
+    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);
+    return *status_out == STATUS_FINISHED ? 0 : -1;
+  }
+  fprintf(stderr, "Deleting files not in manifest...\n");
+  bool deletion_ok = delete_extras(config->receive_root_directory, manifest);
+  array_list_delete(manifest);
+  return deletion_ok ? 0 : -1;
 }

src/shared/file.h

@@ -26,6 +26,7 @@ typedef struct {
 File* file_create(const char* path);
 void file_destroy(void* item);
 bool file_load_data(File* file);
+bool file_checksum(File* file, uint64_t* checksum);
 File* file_receive(const Config* config, int file_descriptor);
 bool file_send_single_calls(File* file, int file_descriptor, bool use_metadata,
                             int compression_level, bool send_path);
@@ -36,7 +37,8 @@ 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 inplace,
              bool sparse);
-bool file_save_to_disk(const char* root_directory, File* file, const Config* config);
+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);
 File* receive_incremental_check(int fd, const Config* config, bool* skipped);
 int receive_manifest(int fd, const Config* config, int* next_status);
 

src/shared/metadata.c

@@ -105,11 +105,16 @@ FileMetadata* metadata_receive(int file_descriptor, int* ok) {
       *ok = 0;
     return NULL;
   }
-  if (!present) {
+  if (present == 0) {
     if (ok)
       *ok = 1;
     return NULL;
   }
+  if (present != 1) {
+    if (ok)
+      *ok = 0;
+    return NULL;
+  }
   FileMetadata* m = malloc(sizeof(FileMetadata));
   if (m == NULL) {
     if (ok)
@@ -156,18 +161,24 @@ FileMetadata* metadata_receive(int file_descriptor, int* ok) {
     return NULL;
   }
   m->mtime_nsec = (long)mtime_nsec;
+  if (mtime_nsec < 0 || mtime_nsec >= 1000000000LL || mode < 0 || uid < 0 || gid < 0) {
+    free(m);
+    if (ok)
+      *ok = 0;
+    return NULL;
+  }
   if (ok)
     *ok = 1;
   return m;
 }
 
-void file_restore_metadata(const char* path, FileMetadata* metadata) {
+void file_restore_metadata(const char* path, const FileMetadata* metadata) {
   if (metadata == NULL)
     return;
   if (chmod(path, metadata->mode & 07777 & ~(S_ISUID | S_ISGID)) != 0)
     log_message(LOG_LEVEL_WARNING, "Failed to chmod %s: %s", path, strerror(errno));
-  if (chown(path, metadata->uid, metadata->gid) != 0)
-    log_message(LOG_LEVEL_WARNING, "Failed to chown %s: %s", path, strerror(errno));
+  /* Never apply client-supplied ownership.  The descriptor API below is the
+     receiver write path; retain this legacy API only for compatibility. */
   struct timespec times[2];
   times[0].tv_sec = 0;
   times[0].tv_nsec = UTIME_OMIT;
@@ -176,3 +187,17 @@ void file_restore_metadata(const char* path, FileMetadata* metadata) {
   if (utimensat(AT_FDCWD, path, times, 0) != 0)
     log_message(LOG_LEVEL_WARNING, "Failed to set timestamps on %s: %s", path, strerror(errno));
 }
+
+bool file_restore_metadata_fd(int fd, const FileMetadata* metadata) {
+  if (fd < 0 || metadata == NULL)
+    return metadata == NULL;
+  bool ok = true;
+  if (fchmod(fd, metadata->mode & 07777 & ~(S_ISUID | S_ISGID)) != 0)
+    ok = false;
+  /* Client uid/gid values are deliberately not authoritative. */
+  struct timespec times[2] = {{.tv_sec = 0, .tv_nsec = UTIME_OMIT},
+                              {.tv_sec = metadata->mtime_sec, .tv_nsec = metadata->mtime_nsec}};
+  if (futimens(fd, times) != 0)
+    ok = false;
+  return ok;
+}

src/shared/metadata.h

@@ -29,6 +29,7 @@ void metadata_to_buf(char** buf, const FileMetadata* m);
 FileMetadata* metadata_from_buf(char** buf);
 bool metadata_send(int file_descriptor, FileMetadata* m);
 FileMetadata* metadata_receive(int file_descriptor, int* ok);
-void file_restore_metadata(const char* path, FileMetadata* metadata);
+void file_restore_metadata(const char* path, const FileMetadata* metadata);
+bool file_restore_metadata_fd(int fd, const FileMetadata* metadata);
 
 #endif

src/shared/multiprocessing.c

@@ -1,4 +1,5 @@
 #include "multiprocessing.h"
+
 #include "array_list.h"
 #include "chunk.h"
 #include "config.h"
@@ -13,6 +14,10 @@
 #include <string.h>
 #include <threads.h>
 
+static bool valid_batch_path(const char* path) {
+  return path && path[0] != '\0' && path[0] != '/' && !has_path_traversal(path);
+}
+
 PipelineContextSender* pipeline_context_sender_create(Config* config, Queue* queue_scanner,
                                                       Queue* queue_loader) {
   PipelineContextSender* context = malloc(sizeof(PipelineContextSender));
@@ -26,7 +31,7 @@ PipelineContextSender* pipeline_context_sender_create(Config* config, Queue* que
   context->manifest = NULL;
   context->progress_bytes = 0;
   context->sender_done = false;
-  context->cancelled = false;
+  atomic_init(&context->cancelled, false);
   int init = 0;
   if (mtx_init(&context->mutex_scanner, mtx_plain) != thrd_success)
     goto fail;
@@ -97,7 +102,7 @@ PipelineContextReceiver* pipeline_context_receiver_create(Config* config, Queue*
   context->file_descriptor = file_descriptor;
   context->ssl = ssl;
   context->receiver_done = false;
-  context->cancelled = false;
+  atomic_init(&context->cancelled, false);
   int init = 0;
   if (mtx_init(&context->mutex, mtx_plain) != thrd_success)
     goto fail;
@@ -152,7 +157,21 @@ static bool receive_chunk_enqueue(int file_descriptor, PipelineContextReceiver*
   return true;
 }
 
+static void receiver_thread_fail(PipelineContextReceiver* context) {
+  mtx_lock(&context->mutex);
+  atomic_store(&context->cancelled, true);
+  context->receiver_done = true;
+  cnd_broadcast(&context->condition_not_empty);
+  cnd_broadcast(&context->condition_not_full);
+  mtx_unlock(&context->mutex);
+}
+
 int receive_thread(void* pipeline_context) {
+#define RECEIVE_THREAD_FAIL()                                                                      \
+  do {                                                                                             \
+    receiver_thread_fail(context);                                                                 \
+    return thrd_error;                                                                             \
+  } while (0)
   PipelineContextReceiver* context = (PipelineContextReceiver*)pipeline_context;
   if (context->ssl)
     io_set_ssl(context->ssl);
@@ -163,57 +182,63 @@ int receive_thread(void* pipeline_context) {
 
   Status status;
   if (!receive_status(file_descriptor, &status))
-    return thrd_error;
+    RECEIVE_THREAD_FAIL();
   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);
+      if (!send_status(file_descriptor, STATUS_KEEPALIVE))
+        RECEIVE_THREAD_FAIL();
       goto next;
     }
     if (status == STATUS_ABORT) {
       log_message(LOG_LEVEL_INFO, "Received abort from client, cleaning up");
-      return thrd_error;
+      RECEIVE_THREAD_FAIL();
     }
     if (status == STATUS_CHECK) {
       bool skipped;
       File* file = receive_incremental_check(file_descriptor, config, &skipped);
       if (!skipped) {
         if (file == NULL)
-          return thrd_error;
+          RECEIVE_THREAD_FAIL();
         if (!queue_enqueue_multithreaded_cancel(
                 context->queue, file, &context->mutex, &context->condition_not_empty,
                 &context->condition_not_full, &context->cancelled)) {
           file_destroy(file);
-          return thrd_error;
+          RECEIVE_THREAD_FAIL();
         }
       }
     } else if (status == STATUS_CHUNK) {
       if (!receive_chunk_enqueue(file_descriptor, context))
-        return thrd_error;
+        RECEIVE_THREAD_FAIL();
     } else if (status == STATUS_CHECK_BATCH) {
       int count;
-      if (!receive_int(file_descriptor, &count))
-        return thrd_error;
+      if (config->checksum || !receive_int(file_descriptor, &count) || count < 0 ||
+          count > MAX_MANIFEST_ENTRIES)
+        RECEIVE_THREAD_FAIL();
       for (int i = 0; i < count; i++) {
         char* check_path = receive_str(file_descriptor);
         if (!check_path)
-          return thrd_error;
+          RECEIVE_THREAD_FAIL();
         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;
+          RECEIVE_THREAD_FAIL();
+        }
+        if (!valid_batch_path(check_path)) {
+          free(check_path);
+          if (!send_status(file_descriptor, STATUS_ERROR))
+            RECEIVE_THREAD_FAIL();
+          RECEIVE_THREAD_FAIL();
         }
         char* full_path = path_cat(config->receive_root_directory, check_path);
         struct stat st;
         bool has_old = full_path && lstat(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);
+        if (!send_status(file_descriptor, match ? STATUS_OK : STATUS_NEXT))
+          RECEIVE_THREAD_FAIL();
         free(full_path);
         free(check_path);
       }
@@ -225,25 +250,29 @@ int receive_thread(void* pipeline_context) {
                 context->queue, file, &context->mutex, &context->condition_not_empty,
                 &context->condition_not_full, &context->cancelled)) {
           file_destroy(file);
+          receiver_thread_fail(context);
           return thrd_error;
         }
       } else {
         log_message(LOG_LEVEL_ERROR, "Failed to receive file");
-        return thrd_error;
+        RECEIVE_THREAD_FAIL();
       }
     }
   next:
     if (!receive_status(file_descriptor, &status))
-      return thrd_error;
+      RECEIVE_THREAD_FAIL();
   }
   if (status == STATUS_MANIFEST) {
     if (receive_manifest(file_descriptor, config, &status) != 0)
-      return thrd_error;
+      RECEIVE_THREAD_FAIL();
   }
+  if (status != STATUS_FINISHED)
+    RECEIVE_THREAD_FAIL();
   mtx_lock(&context->mutex);
   context->receiver_done = true;
   cnd_signal(&context->condition_not_empty);
   mtx_unlock(&context->mutex);
+#undef RECEIVE_THREAD_FAIL
   return thrd_success;
 }
 
@@ -264,8 +293,17 @@ int write_thread(void* pipeline_context) {
       free(root_directory);
       return thrd_success;
     }
-    if (save_to_disk)
-      file_save_to_disk(root_directory, file, context->config);
+    if (save_to_disk && !file_save_to_disk(root_directory, file, context->config)) {
+      file_destroy(file);
+      mtx_lock(&context->mutex);
+      atomic_store(&context->cancelled, true);
+      context->receiver_done = true;
+      cnd_broadcast(&context->condition_not_full);
+      cnd_broadcast(&context->condition_not_empty);
+      mtx_unlock(&context->mutex);
+      free(root_directory);
+      return thrd_error;
+    }
     file_destroy(file);
   }
 }

src/shared/multiprocessing.h

@@ -2,6 +2,7 @@
 #define MULTIPROCESSING_H
 
 #include <threads.h>
+#include <stdatomic.h>
 
 #include "array_list.h"
 #include "config.h"
@@ -26,7 +27,7 @@ typedef struct {
   mtx_t mutex_progress;
   unsigned long long progress_bytes;
   bool sender_done;
-  bool cancelled;
+  atomic_bool cancelled;
 } PipelineContextSender;
 
 typedef struct PipelineContextReceiver {
@@ -38,7 +39,7 @@ typedef struct PipelineContextReceiver {
   cnd_t condition_not_full;
   cnd_t condition_not_empty;
   bool receiver_done;
-  bool cancelled;
+  atomic_bool cancelled;
 } PipelineContextReceiver;
 
 PipelineContextSender* pipeline_context_sender_create(Config* config, Queue* queue_scanner,

src/shared/protocol.c

@@ -1,6 +1,7 @@
 #include "protocol.h"
 #include "log.h"
 #include <errno.h>
+#include <limits.h>
 #include <openssl/ssl.h>
 #include <poll.h>
 #include <stdio.h>
@@ -10,7 +11,8 @@
 #include <time.h>
 #include <unistd.h>
 
-#define RECEIVE_TIMEOUT_SEC 60                        /* 60 second per-message timeout */
+#define RECEIVE_TIMEOUT_SEC 60 /* 60 second per-message timeout */
+#define SEND_TIMEOUT_SEC 60
 #define MAX_CONNECTION_MEMORY (1024ULL * 1024 * 1024) /* 1 GB total per connection */
 
 static __thread int io_read_fd = -1;
@@ -28,6 +30,10 @@ 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;
+  /* A descriptor switch starts a new transport; never reuse a TLS object
+     belonging to a previous connection or test pipe. */
+  io_ssl = NULL;
+  total_allocated_bytes = 0;
 }
 
 static void bw_mutex_init(void) {
@@ -87,14 +93,39 @@ static int io_fd(int dir_fd, int file_descriptor) {
   return (dir_fd != -1) ? dir_fd : file_descriptor;
 }
 
+static int deadline_remaining_ms(const struct timespec* deadline) {
+  struct timespec now;
+  clock_gettime(CLOCK_MONOTONIC, &now);
+  long long ns =
+      (long long)(deadline->tv_sec - now.tv_sec) * 1000000000LL + deadline->tv_nsec - now.tv_nsec;
+  if (ns <= 0)
+    return 0;
+  long long ms = (ns + 999999) / 1000000;
+  return ms > INT_MAX ? INT_MAX : (int)ms;
+}
+
 bool send_n_data(int file_descriptor, const void* data, size_t data_size) {
   log_message(LOG_LEVEL_DEBUG, "    Sending n Data: %zu", data_size);
   int fd = io_fd(io_write_fd, file_descriptor);
+  struct timespec deadline;
+  clock_gettime(CLOCK_MONOTONIC, &deadline);
+  deadline.tv_sec += SEND_TIMEOUT_SEC;
+  short wait_events = POLLOUT;
   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)
       chunk = 65536;
+    struct pollfd pfd = {.fd = fd, .events = wait_events};
+    int poll_result = poll(&pfd, 1, deadline_remaining_ms(&deadline));
+    if (poll_result == 0 || (poll_result < 0 && errno != EINTR)) {
+      log_message(LOG_LEVEL_ERROR, "Send timeout or poll failure");
+      return false;
+    }
+    if (poll_result < 0)
+      continue;
+    if (pfd.revents & (POLLERR | POLLNVAL))
+      return false;
     ssize_t bytes_send;
     if (io_ssl)
       bytes_send = SSL_write(io_ssl, (const char*)data + total_bytes_send, chunk);
@@ -103,8 +134,10 @@ bool send_n_data(int file_descriptor, const void* data, size_t data_size) {
     if (bytes_send <= 0) {
       if (io_ssl) {
         int ssl_err = SSL_get_error(io_ssl, (int)bytes_send);
-        if (ssl_err == SSL_ERROR_WANT_WRITE || ssl_err == SSL_ERROR_WANT_READ)
+        if (ssl_err == SSL_ERROR_WANT_WRITE || ssl_err == SSL_ERROR_WANT_READ) {
+          wait_events = ssl_err == SSL_ERROR_WANT_WRITE ? POLLOUT : POLLIN;
           continue;
+        }
       }
       log_message(LOG_LEVEL_ERROR, "Could not send data");
       return false;
@@ -125,14 +158,22 @@ bool receive_n_data(int file_descriptor, void* data, size_t data_size) {
   deadline.tv_sec += RECEIVE_TIMEOUT_SEC;
 
   size_t total_bytes_received = 0;
+  short wait_events = POLLIN;
   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)) {
+    struct pollfd pfd = {.fd = fd, .events = wait_events};
+    int poll_result = poll(&pfd, 1, deadline_remaining_ms(&deadline));
+    if (poll_result == 0) {
       log_message(LOG_LEVEL_ERROR, "Receive timeout after %ds", RECEIVE_TIMEOUT_SEC);
       return false;
     }
+    if (poll_result < 0) {
+      if (errno == EINTR)
+        continue;
+      return false;
+    }
+    /* POLLHUP may accompany the final readable bytes on pipes/sockets. */
+    if (pfd.revents & (POLLERR | POLLNVAL))
+      return false;
 
     ssize_t bytes_received;
     if (io_ssl)
@@ -144,8 +185,10 @@ bool receive_n_data(int file_descriptor, void* data, size_t data_size) {
     if (bytes_received <= 0) {
       if (io_ssl) {
         int ssl_err = SSL_get_error(io_ssl, (int)bytes_received);
-        if (ssl_err == SSL_ERROR_WANT_WRITE || ssl_err == SSL_ERROR_WANT_READ)
+        if (ssl_err == SSL_ERROR_WANT_WRITE || ssl_err == SSL_ERROR_WANT_READ) {
+          wait_events = ssl_err == SSL_ERROR_WANT_WRITE ? POLLOUT : POLLIN;
           continue;
+        }
       }
       if (bytes_received == 0)
         log_message(LOG_LEVEL_ERROR, "Connection closed while receiving data");
@@ -204,7 +247,8 @@ 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) {
+  if (size > MAX_STRING_SIZE || size > SIZE_MAX - 1 ||
+      size + 1 > MAX_CONNECTION_MEMORY - total_allocated_bytes) {
     log_message(LOG_LEVEL_ERROR, "String size %zu exceeds maximum %llu", size,
                 (unsigned long long)MAX_STRING_SIZE);
     return NULL;
@@ -217,6 +261,7 @@ 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;
 }
@@ -240,22 +285,28 @@ Data* receive_data(int file_descriptor) {
                 (unsigned long long)MAX_DATA_PAYLOAD_SIZE);
     return NULL;
   }
-  if (total_allocated_bytes + size > MAX_CONNECTION_MEMORY) {
+  size_t allocation_size = size == 0 ? 1 : (size_t)size;
+  if (allocation_size > MAX_CONNECTION_MEMORY - total_allocated_bytes) {
     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);
+  void* data = malloc(allocation_size);
   if (data == NULL)
     return NULL;
   if (!receive_n_data(file_descriptor, data, (size_t)size)) {
     free(data);
     return NULL;
   }
-  total_allocated_bytes += size;
+  total_allocated_bytes += allocation_size;
   log_message(LOG_LEVEL_DEBUG, "Received %lld data", size);
-  return data_create(data, (size_t)size);
+  Data* result = data_create(data, (size_t)size);
+  if (!result) {
+    free(data);
+    total_allocated_bytes -= allocation_size;
+  }
+  return result;
 }
 
 bool send_int(int file_descriptor, int data) {

src/shared/protocol.h

@@ -13,6 +13,9 @@
 
 /* Maximum chunk size (64 MB) — prevents unbounded allocation from the wire */
 #define MAX_CHUNK_SIZE (64ULL * 1024 * 1024)
+#define MAX_MANIFEST_ENTRIES (1024 * 1024)
+/* Aggregate bytes retained by one received deletion manifest. */
+#define MAX_MANIFEST_BYTES (16ULL * 1024 * 1024)
 
 typedef struct ssl_st SSL;
 

src/shared/queue.c

@@ -1,148 +1,154 @@
-#include <stdbool.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <threads.h>
-
-#include "queue.h"
-
-Queue* queue_create(int capacity, void (*destroyer)(void* item)) {
-  Queue* queue = (Queue*)malloc(sizeof(Queue));
-  if (queue == NULL) {
-    perror("ERROR: Could not allocate memory for queue structure");
-    return NULL;
-  }
-
-  queue->items = malloc(capacity * sizeof(void*));
-  if (queue->items == NULL) {
-    free(queue);
-    return NULL;
-  }
-
-  for (int i = 0; i < capacity; ++i) {
-    queue->items[i] = NULL;
-  }
-
-  queue->capacity = capacity;
-  queue->front = 0;
-  queue->rear = 0;
-  queue->size = 0;
-  queue->item_destroyer = destroyer;
-
-  return queue;
-}
-
-void queue_destroy(Queue* queue) {
-  if (queue == NULL)
-    return;
-
-  if (queue->item_destroyer != NULL) {
-    for (int i = 0; i < queue->size; ++i) {
-      int index = (queue->front + i) % queue->capacity;
-      queue->item_destroyer(queue->items[index]);
-    }
-  }
-  free(queue->items);
-  free(queue);
-}
-
-bool queue_is_empty(const Queue* queue) {
-  if (queue == NULL)
-    return true;
-  return queue->size == 0;
-}
-
-bool queue_is_full(const Queue* queue) {
-  if (queue == NULL)
-    return false;
-  return queue->size == queue->capacity;
-}
-
-static bool queue_double_capacity(Queue* queue) {
-  if (queue == NULL)
-    return false;
-  unsigned int new_capacity = queue->capacity * 2;
-  if (new_capacity <= 1)
-    new_capacity = 100;
-  void** new_items = malloc(new_capacity * sizeof(void*));
-  if (new_items == NULL) {
-    perror("ERROR: Could not allocate memory for doubling capacity of queue.");
-    return false;
-  }
-  for (int i = 0; i < queue->size; i++)
-    new_items[i] = queue->items[(i + queue->front) % queue->capacity];
-  free(queue->items);
-  queue->items = new_items;
-  queue->front = 0;
-  queue->rear = queue->size;
-  queue->capacity = new_capacity;
-  return true;
-}
-
-bool queue_enqueue(Queue* queue, void* item) {
-  if (queue == NULL || item == NULL)
-    return false;
-  if (queue_is_full(queue)) {
-    if (!queue_double_capacity(queue))
-      return false;
-  }
-  queue->items[queue->rear] = item;
-  queue->rear = (queue->rear + 1) % queue->capacity;
-  queue->size++;
-  return true;
-}
-
-bool queue_enqueue_multithreaded(Queue* queue, void* item, mtx_t* mutex, cnd_t* condition_not_empty,
-                                 cnd_t* condition_not_full) {
-  mtx_lock(mutex);
-  while (queue_is_full(queue))
-    cnd_wait(condition_not_full, mutex);
-  bool ok = queue_enqueue(queue, item);
-  cnd_signal(condition_not_empty);
-  mtx_unlock(mutex);
-  return ok;
-}
-
-bool queue_enqueue_multithreaded_cancel(Queue* queue, void* item, mtx_t* mutex,
-                                        cnd_t* condition_not_empty, cnd_t* condition_not_full,
-                                        const bool* cancelled) {
-  mtx_lock(mutex);
-  while (queue_is_full(queue) && (cancelled == NULL || !*cancelled))
-    cnd_wait(condition_not_full, mutex);
-  if (cancelled != NULL && *cancelled) {
-    mtx_unlock(mutex);
-    return false;
-  }
-  bool ok = queue_enqueue(queue, item);
-  cnd_signal(condition_not_empty);
-  mtx_unlock(mutex);
-  return ok;
-}
-
-void* queue_dequeue(Queue* queue) {
-  if (queue == NULL || queue_is_empty(queue)) {
-    perror("ERROR: Could not dequeue from null or empty queue.");
-    return NULL;
-  }
-
-  void* item = queue->items[queue->front];
-  queue->items[queue->front] = NULL;
-  queue->front = (queue->front + 1) % queue->capacity;
-  queue->size--;
-  return item;
-}
-
-void* queue_dequeue_multithreaded(Queue* queue, mtx_t* mutex, cnd_t* condition_not_empty,
-                                  cnd_t* condition_not_full, const bool* other_thread_done) {
-  mtx_lock(mutex);
-  while (queue_is_empty(queue) && !*other_thread_done)
-    cnd_wait(condition_not_empty, mutex);
-  if (queue_is_empty(queue) && *other_thread_done) {
-    mtx_unlock(mutex);
-    return NULL;
-  }
-  void* item = queue_dequeue(queue);
-  cnd_signal(condition_not_full);
-  mtx_unlock(mutex);
-  return item;
-}
+#include <stdbool.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <threads.h>
+
+#include "queue.h"
+
+Queue* queue_create(int capacity, void (*destroyer)(void* item)) {
+  if (capacity <= 0)
+    return NULL;
+
+  Queue* queue = (Queue*)malloc(sizeof(Queue));
+  if (queue == NULL) {
+    perror("ERROR: Could not allocate memory for queue structure");
+    return NULL;
+  }
+
+  queue->items = malloc(capacity * sizeof(void*));
+  if (queue->items == NULL) {
+    free(queue);
+    return NULL;
+  }
+
+  for (int i = 0; i < capacity; ++i) {
+    queue->items[i] = NULL;
+  }
+
+  queue->capacity = capacity;
+  queue->front = 0;
+  queue->rear = 0;
+  queue->size = 0;
+  queue->item_destroyer = destroyer;
+
+  return queue;
+}
+
+void queue_destroy(Queue* queue) {
+  if (queue == NULL)
+    return;
+
+  if (queue->item_destroyer != NULL) {
+    for (int i = 0; i < queue->size; ++i) {
+      int index = (queue->front + i) % queue->capacity;
+      queue->item_destroyer(queue->items[index]);
+    }
+  }
+  free(queue->items);
+  free(queue);
+}
+
+bool queue_is_empty(const Queue* queue) {
+  if (queue == NULL)
+    return true;
+  return queue->size == 0;
+}
+
+bool queue_is_full(const Queue* queue) {
+  if (queue == NULL)
+    return false;
+  return queue->size == queue->capacity;
+}
+
+static bool queue_double_capacity(Queue* queue) {
+  if (queue == NULL)
+    return false;
+  if (queue->capacity > INT_MAX / 2)
+    return false;
+  int new_capacity = queue->capacity * 2;
+  if (new_capacity <= 1)
+    new_capacity = 100;
+  void** new_items = malloc(new_capacity * sizeof(void*));
+  if (new_items == NULL) {
+    perror("ERROR: Could not allocate memory for doubling capacity of queue.");
+    return false;
+  }
+  for (int i = 0; i < queue->size; i++)
+    new_items[i] = queue->items[(i + queue->front) % queue->capacity];
+  free(queue->items);
+  queue->items = new_items;
+  queue->front = 0;
+  queue->rear = queue->size;
+  queue->capacity = new_capacity;
+  return true;
+}
+
+bool queue_enqueue(Queue* queue, void* item) {
+  if (queue == NULL || item == NULL)
+    return false;
+  if (queue_is_full(queue)) {
+    if (!queue_double_capacity(queue))
+      return false;
+  }
+  queue->items[queue->rear] = item;
+  queue->rear = (queue->rear + 1) % queue->capacity;
+  queue->size++;
+  return true;
+}
+
+bool queue_enqueue_multithreaded(Queue* queue, void* item, mtx_t* mutex, cnd_t* condition_not_empty,
+                                 cnd_t* condition_not_full) {
+  mtx_lock(mutex);
+  while (queue_is_full(queue))
+    cnd_wait(condition_not_full, mutex);
+  bool ok = queue_enqueue(queue, item);
+  cnd_signal(condition_not_empty);
+  mtx_unlock(mutex);
+  return ok;
+}
+
+bool queue_enqueue_multithreaded_cancel(Queue* queue, void* item, mtx_t* mutex,
+                                        cnd_t* condition_not_empty, cnd_t* condition_not_full,
+                                        const atomic_bool* cancelled) {
+  mtx_lock(mutex);
+  while (queue_is_full(queue) && (cancelled == NULL || !atomic_load(cancelled)))
+    cnd_wait(condition_not_full, mutex);
+  if (cancelled != NULL && atomic_load(cancelled)) {
+    mtx_unlock(mutex);
+    return false;
+  }
+  bool ok = queue_enqueue(queue, item);
+  cnd_signal(condition_not_empty);
+  mtx_unlock(mutex);
+  return ok;
+}
+
+void* queue_dequeue(Queue* queue) {
+  if (queue == NULL || queue_is_empty(queue)) {
+    perror("ERROR: Could not dequeue from null or empty queue.");
+    return NULL;
+  }
+
+  void* item = queue->items[queue->front];
+  queue->items[queue->front] = NULL;
+  queue->front = (queue->front + 1) % queue->capacity;
+  queue->size--;
+  return item;
+}
+
+void* queue_dequeue_multithreaded(Queue* queue, mtx_t* mutex, cnd_t* condition_not_empty,
+                                  cnd_t* condition_not_full, const bool* other_thread_done) {
+  mtx_lock(mutex);
+  while (queue_is_empty(queue) && !*other_thread_done)
+    cnd_wait(condition_not_empty, mutex);
+  if (queue_is_empty(queue) && *other_thread_done) {
+    mtx_unlock(mutex);
+    return NULL;
+  }
+  void* item = queue_dequeue(queue);
+  cnd_signal(condition_not_full);
+  mtx_unlock(mutex);
+  return item;
+}

src/shared/queue.h

@@ -1,30 +1,31 @@
-#ifndef QUEUE_H
-#define QUEUE_H
-
-#include <stdbool.h>
-#include <threads.h>
-
-typedef struct Queue {
-  void** items;
-  int front;
-  int rear;
-  int size;
-  int capacity;
-  void (*item_destroyer)(void* item);
-} Queue;
-
-Queue* queue_create(int capacity, void (*destroyer)(void* item));
-void queue_destroy(Queue* queue);
-bool queue_is_empty(const Queue* queue);
-bool queue_is_full(const Queue* queue);
-bool queue_enqueue(Queue* queue, void* item);
-bool queue_enqueue_multithreaded(Queue* queue, void* item, mtx_t* mutex, cnd_t* condition_not_empty,
-                                 cnd_t* condition_not_full);
-bool queue_enqueue_multithreaded_cancel(Queue* queue, void* item, mtx_t* mutex,
-                                        cnd_t* condition_not_empty, cnd_t* condition_not_full,
-                                        const bool* cancelled);
-void* queue_dequeue(Queue* queue);
-void* queue_dequeue_multithreaded(Queue* queue, mtx_t* mutex, cnd_t* condition_not_empty,
-                                  cnd_t* condition_not_full, const bool* other_thread_done);
-
-#endif
+#ifndef QUEUE_H
+#define QUEUE_H
+
+#include <stdbool.h>
+#include <stdatomic.h>
+#include <threads.h>
+
+typedef struct Queue {
+  void** items;
+  int front;
+  int rear;
+  int size;
+  int capacity;
+  void (*item_destroyer)(void* item);
+} Queue;
+
+Queue* queue_create(int capacity, void (*destroyer)(void* item));
+void queue_destroy(Queue* queue);
+bool queue_is_empty(const Queue* queue);
+bool queue_is_full(const Queue* queue);
+bool queue_enqueue(Queue* queue, void* item);
+bool queue_enqueue_multithreaded(Queue* queue, void* item, mtx_t* mutex, cnd_t* condition_not_empty,
+                                 cnd_t* condition_not_full);
+bool queue_enqueue_multithreaded_cancel(Queue* queue, void* item, mtx_t* mutex,
+                                        cnd_t* condition_not_empty, cnd_t* condition_not_full,
+                                        const atomic_bool* cancelled);
+void* queue_dequeue(Queue* queue);
+void* queue_dequeue_multithreaded(Queue* queue, mtx_t* mutex, cnd_t* condition_not_empty,
+                                  cnd_t* condition_not_full, const bool* other_thread_done);
+
+#endif

src/shared/transport_tcp.c

@@ -15,6 +15,8 @@
 
 static volatile sig_atomic_t g_active_connections = 0;
 
+static void tcp_apply_socket_timeout(int fd);
+
 static void sigchld_handler(int sig) {
   (void)sig;
   int saved_errno = errno;
@@ -93,6 +95,7 @@ static void accept_loop(Server* server, void (*child_fn)(int, void*), void* chil
       perror("Could not accept the connection");
       continue;
     }
+    tcp_apply_socket_timeout(fd);
     if ((unsigned int)g_active_connections >= server->max_connections) {
       log_message(LOG_LEVEL_WARNING, "Max connections (%u) reached, rejecting",
                   server->max_connections);

src/shared/transport_tls.c

@@ -71,7 +71,7 @@ static SSL_CTX* create_ssl_ctx(bool is_server, const char* cert, const char* key
       SSL_CTX_free(ctx);
       return NULL;
     }
-    SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER, NULL);
+    SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT, NULL);
     SSL_CTX_set_verify_depth(ctx, 4);
   } else {
     SSL_CTX_set_verify(ctx, SSL_VERIFY_NONE, NULL);

src/shared/utils.c

@@ -3,12 +3,19 @@
 #include "libgen.h"
 #include <dirent.h>
 #include <errno.h>
+#include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
+static int authorized_root_fd = -1;
+
+void utils_set_authorized_root_fd(int fd) {
+  authorized_root_fd = fd;
+}
+
 bool mkdir_r(const char* path) {
   size_t path_len = strlen(path);
   char* path_duplicate = malloc(path_len + 1);
@@ -136,34 +143,43 @@ static bool is_dir_in_manifest(const char* rel_path, ArrayList* manifest) {
   return false;
 }
 
-static void delete_extras_walk(const char* abs_path, const char* rel_path, ArrayList* manifest) {
-  DIR* dir = opendir(abs_path);
-  if (!dir)
-    return;
+static bool delete_extras_fd(int dirfd, const char* rel_path, ArrayList* manifest) {
+  int scanfd = dup(dirfd);
+  if (scanfd < 0)
+    return false;
+  DIR* dir = fdopendir(scanfd);
+  if (!dir) {
+    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_abs = path_cat((char*)abs_path, entry->d_name);
     char* child_rel = path_cat((char*)rel_path, entry->d_name);
     struct stat st;
-    if (lstat(child_abs, &st) != 0) {
-      free(child_abs);
+    if (fstatat(dirfd, entry->d_name, &st, AT_SYMLINK_NOFOLLOW) != 0) {
       free(child_rel);
       continue;
     }
     // Skip symlinks to prevent following them outside the destination tree
     if (S_ISLNK(st.st_mode)) {
-      free(child_abs);
       free(child_rel);
       continue;
     }
     if (S_ISDIR(st.st_mode)) {
-      delete_extras_walk(child_abs, child_rel, manifest);
-      // After recursion, try to remove the subdirectory if it's now empty.
-      // Ignore ENOENT: the recursive call may have already removed it.
-      if (rmdir(child_abs) != 0 && errno != ENOENT) {
+      int childfd = openat(dirfd, entry->d_name, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
+      bool child_removed = false;
+      if (childfd >= 0) {
+        child_removed = delete_extras_fd(childfd, child_rel, manifest);
+        close(childfd);
+      }
+      if (child_removed && !is_dir_in_manifest(child_rel, manifest) &&
+          unlinkat(dirfd, entry->d_name, AT_REMOVEDIR) != 0 && errno != ENOENT) {
+        operation_ok = false;
+      } else if (!child_removed) {
         all_removed = false;
       }
     } else {
@@ -176,25 +192,30 @@ static void delete_extras_walk(const char* abs_path, const char* rel_path, Array
         }
       }
       if (!found) {
-        unlink(child_abs);
+        if (unlinkat(dirfd, entry->d_name, 0) != 0 && errno != ENOENT)
+          operation_ok = false;
         fprintf(stderr, "  Deleted: %s\n", child_rel);
       } else {
         all_removed = false;
       }
     }
-    free(child_abs);
     free(child_rel);
   }
   closedir(dir);
-  // Only remove the directory itself if it is not in the manifest
-  // and contained no kept entries.
-  if (all_removed && rel_path[0] != '\0' && !is_dir_in_manifest(rel_path, manifest)) {
-    rmdir(abs_path);
-  }
+  (void)all_removed;
+  return operation_ok;
 }
 
-void delete_extras(const char* dest_root, ArrayList* manifest) {
-  delete_extras_walk(dest_root, "", manifest);
+bool delete_extras(const char* dest_root, ArrayList* manifest) {
+  int rootfd = authorized_root_fd >= 0
+                   ? dup(authorized_root_fd)
+                   : open(dest_root, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC);
+  if (rootfd < 0)
+    return false;
+  bool ok = delete_extras_fd(rootfd, "", manifest);
+  if (close(rootfd) != 0)
+    ok = false;
+  return ok;
 }
 
 bool has_path_traversal(const char* path) {

src/shared/utils.h

@@ -8,7 +8,8 @@ bool mkdir_r(const char* path);
 char* str_dup(const char* string);
 char* path_cat(const char* path1, const char* path2);
 bool glob_match(const char* pattern, const char* str);
-void delete_extras(const char* dest_root, ArrayList* manifest);
+bool delete_extras(const char* dest_root, ArrayList* manifest);
+void utils_set_authorized_root_fd(int fd);
 bool has_path_traversal(const char* path);
 
 #endif