fix: guard source removal against file replacement

src/client/client_send.c

@@ -16,6 +16,8 @@
 #include "transport_ssh.h"
 #include "transport_tls.h"
 #include "utils.h"
+#include <fcntl.h>
+#include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -105,26 +107,83 @@ static bool finalize_transfer(Client* client) {
          receive_status(client->file_descriptor, &status) && status == STATUS_OK;
 }
 
-/* Remove only regular source files after the receiver confirms the whole transfer. */
+typedef struct {
+  char* path;
+  dev_t device;
+  ino_t inode;
+} SourceFile;
+
+static void source_file_destroy(void* item) {
+  SourceFile* source = item;
+  if (source) {
+    free(source->path);
+    free(source);
+  }
+}
+
+/* Remove only the same regular source file that was sent. */
 static void remove_transferred_sources(const Config* config, ArrayList* paths) {
   if (!config->remove_source_files || !paths)
     return;
   for (int i = 0; i < paths->size; i++) {
-    const char* path = paths->items[i];
-    struct stat st;
-    if (lstat(path, &st) != 0 || !S_ISREG(st.st_mode))
+    SourceFile* source = paths->items[i];
+    const char* slash = strrchr(source->path, '/');
+    const char* leaf = slash ? slash + 1 : source->path;
+    char parent[PATH_MAX];
+    if (slash) {
+      size_t parent_length = (size_t)(slash - source->path);
+      if (parent_length == 0)
+        parent_length = 1;
+      if (parent_length >= sizeof(parent))
         continue;
-    if (unlink(path) != 0)
-      log_message(LOG_LEVEL_WARNING, "Could not remove source file %s", path);
+      memcpy(parent, source->path, parent_length);
+      parent[parent_length] = '\0';
+    } else {
+      (void)snprintf(parent, sizeof(parent), ".");
     }
+
+    int dirfd = open(parent, O_RDONLY | O_DIRECTORY | O_CLOEXEC);
+    if (dirfd < 0)
+      continue;
+    struct stat st;
+    if (fstatat(dirfd, leaf, &st, AT_SYMLINK_NOFOLLOW) != 0 || !S_ISREG(st.st_mode) ||
+        st.st_dev != source->device || st.st_ino != source->inode) {
+      close(dirfd);
+      continue;
+    }
+    if (unlinkat(dirfd, leaf, 0) != 0)
+      log_message(LOG_LEVEL_WARNING, "Could not remove source file %s", source->path);
+    close(dirfd);
+  }
+}
+
+static SourceFile* source_file_create(const File* file) {
+  if (!file || !file->path)
+    return NULL;
+  struct stat st;
+  if (lstat(file->path, &st) != 0 || !S_ISREG(st.st_mode))
+    return NULL;
+  SourceFile* source = malloc(sizeof(*source));
+  if (!source)
+    return NULL;
+  source->path = str_dup(file->path);
+  source->device = st.st_dev;
+  source->inode = st.st_ino;
+  if (!source->path) {
+    source_file_destroy(source);
+    return NULL;
+  }
+  return source;
 }
 
 static bool remember_source_file(ArrayList* paths, const File* file) {
   if (!paths || !file || !file->path)
     return true;
-  char* path = str_dup(file->path);
-  if (!path || !array_list_add(paths, path)) {
-    free(path);
+  SourceFile* source = source_file_create(file);
+  if (!source)
+    return true;
+  if (!array_list_add(paths, source)) {
+    source_file_destroy(source);
     return false;
   }
   return true;
@@ -372,6 +431,12 @@ static int send_single_file(Client* client, File* file, Config* config, bool use
 static int send_chunk_with_removal(Client* client, Chunk* chunk, Config* config,
                                    ArrayList* remove_sources) {
   if (config->use_chunk_serialization) {
+    if (remove_sources) {
+      for (int i = 0; i < chunk->element_count; i++) {
+        if (!remember_source_file(remove_sources, chunk->items[i]))
+          return -1;
+      }
+    }
     if (!send_status(client->file_descriptor, STATUS_CHUNK))
       return -1;
     Data* data;
@@ -387,12 +452,6 @@ static int send_chunk_with_removal(Client* client, Chunk* chunk, Config* config,
       return -1;
     }
     data_destroy(data);
-    if (remove_sources) {
-      for (int i = 0; i < chunk->element_count; i++) {
-        if (!remember_source_file(remove_sources, chunk->items[i]))
-          return -1;
-      }
-    }
     return 0;
   }
 
@@ -403,14 +462,21 @@ static int send_chunk_with_removal(Client* client, Chunk* chunk, Config* config,
     bool stream = f->data->data == NULL && f->data->size > 0;
     bool use_sendfile =
         (config->use_sendfile && !config->use_compression) || (stream && !config->use_compression);
+    SourceFile* source = remove_sources ? source_file_create(f) : NULL;
     int rc = send_single_file(client, f, config, config->use_incremental, use_sendfile);
-    if (rc == 1)
+    if (rc == 1) {
+      source_file_destroy(source);
       continue;
-    if (rc < 0)
+    }
+    if (rc < 0) {
+      source_file_destroy(source);
       return -1;
-    if (rc == 0 && !remember_source_file(remove_sources, f))
+    }
+    if (source && !array_list_add(remove_sources, source)) {
+      source_file_destroy(source);
       return -1;
     }
+  }
   return 0;
 }
 
@@ -652,7 +718,7 @@ int send_files(Config* config) {
   scanner = directory_scanner_create_with_options(config->send_directory, &scanner_options);
   manifest = create_transfer_manifest(config);
   if (config->remove_source_files)
-    remove_sources = array_list_create(free);
+    remove_sources = array_list_create(source_file_destroy);
   if (!scanner || (config->use_delete && !manifest) ||
       (config->remove_source_files && !remove_sources))
     goto send_fail;
@@ -782,7 +848,7 @@ int send_files_multithreaded(Config** config_ptr) {
   if (config->use_delete)
     context->manifest = array_list_create(free);
   if (config->remove_source_files)
-    context->remove_source_files = array_list_create(free);
+    context->remove_source_files = array_list_create(source_file_destroy);
   if ((config->use_delete && !context->manifest) ||
       (config->remove_source_files && !context->remove_source_files)) {
     pipeline_context_sender_destroy(context);

tests/integration/test_features.py

@@ -57,6 +57,20 @@ class TestRemoveSourceFiles:
         assert os.path.isdir(os.path.join(source, "directory"))
         assert os.path.islink(os.path.join(source, "link.txt"))
 
+    def test_single_threaded_removes_transferred_file(self, shared_server):
+        source = os.path.join(TEST_DATA_DIR, "remove_single_source")
+        dest = os.path.join(TEST_DATA_DIR, "remove_single_dest")
+        clean_dir(source)
+        clean_dir(dest)
+        source_file = os.path.join(source, "file.txt")
+        with open(source_file, "wb") as f:
+            f.write(b"single threaded")
+
+        result, _ = run_client(source, dest, flags=["--remove-source-files"],
+                               port=shared_server.port)
+        assert result.returncode == 0
+        assert not os.path.exists(source_file)
+
     def test_dry_run_preserves_source_files(self):
         source = os.path.join(TEST_DATA_DIR, "remove_dry_source")
         dest = os.path.join(TEST_DATA_DIR, "remove_dry_dest")
@@ -83,6 +97,23 @@ class TestRemoveSourceFiles:
         assert result.returncode != 0
         assert os.path.isfile(source_file)
 
+    def test_incremental_skip_preserves_source_file(self, shared_server):
+        source = os.path.join(TEST_DATA_DIR, "remove_skipped_source")
+        dest = os.path.join(TEST_DATA_DIR, "remove_skipped_dest")
+        clean_dir(source)
+        clean_dir(dest)
+        source_file = os.path.join(source, "file.txt")
+        with open(source_file, "wb") as f:
+            f.write(b"keep after skip")
+
+        result, _ = run_client(source, dest, port=shared_server.port)
+        assert result.returncode == 0
+        result, _ = run_client(source, dest,
+                               flags=["--remove-source-files", "--incremental"],
+                               port=shared_server.port)
+        assert result.returncode == 0
+        assert os.path.isfile(source_file)
+
 
 class TestArchiveMode:
     def test_archive_mode(self, shared_server):