src/client/client_validation.c

@@ -102,6 +102,16 @@ bool validate_config(const Config* config) {
     log_message(LOG_LEVEL_ERROR, "%s", invariants_error);
     return false;
   }
+  /* The receiver rejects a protect-rule block with more than MAX_FILTER_RULES
+     entries as an opaque protocol error; reject an over-limit --filter set here,
+     before any network I/O, with an actionable message.  send_protect_entries()
+     re-checks the final built count because cvs-exclude / merge rules can
+     expand it beyond config->filters->size. */
+  if (config->filters && config->filters->size > MAX_FILTER_RULES) {
+    log_message(LOG_LEVEL_ERROR, "too many filter rules: %d (maximum %d)", config->filters->size,
+                MAX_FILTER_RULES);
+    return false;
+  }
   /* --protocol: FastSync has exactly one wire format, so the forced version
      must equal the current PROTOCOL_VERSION exactly.  Rejected here, before any
      network I/O, rather than letting the server hit its own mismatch check. */

src/shared/config.c

@@ -230,6 +230,13 @@ Config* config_create(void) {
   if (!config)
     return NULL;
   config_set_defaults(config);
+  /* config_set_defaults() dups the default server host; a failure there leaves
+   * server_host NULL and would crash later consumers, so fail the whole create
+   * (every caller already handles a NULL return). */
+  if (!config->server_host) {
+    free(config);
+    return NULL;
+  }
   return config;
 }
 
@@ -686,9 +693,15 @@ int config_parse_ssh_dest(Config* config) {
     return daemon_dest_parse_error("invalid remote destination user@host (must not be empty or "
                                    "start with '-')",
                                    dest);
-  config->transport = TRANSPORT_SSH;
-  config->ssh_destination = str_dup(dest);
+  char* ssh_destination = str_dup(dest);
   char* path = str_dup(colon + 1);
+  if (!ssh_destination || !path) {
+    free(ssh_destination);
+    free(path);
+    return daemon_dest_parse_error("out of memory parsing remote destination", dest);
+  }
+  config->transport = TRANSPORT_SSH;
+  config->ssh_destination = ssh_destination;
   free(config->receive_root_directory);
   config->receive_root_directory = path;
   return 0;
@@ -1052,6 +1065,16 @@ static bool send_protect_entries(int fd, const Config* c) {
     log_message(LOG_LEVEL_ERROR, "invalid filter rule: %s", err);
     return false;
   }
+  /* The receiver rejects any block with more than MAX_FILTER_RULES entries as a
+   * protocol error; refuse to emit such a frame at all.  filter_base_build()
+   * can expand the client rule set (cvs-exclude, merge files), so this is the
+   * authoritative bound, not config->filters->size. */
+  if (rules->count < 0 || rules->count > MAX_FILTER_RULES) {
+    log_message(LOG_LEVEL_ERROR, "too many filter rules: %d (maximum %d)", rules->count,
+                MAX_FILTER_RULES);
+    filter_rule_list_free(rules);
+    return false;
+  }
   bool ok = send_int(fd, rules->count);
   for (int i = 0; ok && i < rules->count; i++) {
     const FilterRule* r = rules->items[i];

tests/test_client_cli.c

@@ -171,6 +171,38 @@ static void test_validate_config_unified_invariants() {
   config_delete(cfg);
 }
 
+/* The receiver enforces MAX_FILTER_RULES on the protect-rule block and would
+   otherwise fail the session with an opaque protocol error.  The client must
+   accept exactly the limit and reject one more up front, before any network
+   I/O, with an actionable message. */
+static void test_validate_config_filter_rule_limit() {
+  Config* cfg = valid_client_config();
+  cfg->filters = array_list_create(free);
+  EXPECT_NOT_NULL(cfg->filters);
+  for (int i = 0; i < MAX_FILTER_RULES; i++)
+    EXPECT_TRUE(array_list_add(cfg->filters, str_dup("- *.tmp")));
+  EXPECT_TRUE(validate_config(cfg)); /* exactly the limit is accepted */
+
+  FILE* log_capture = tmpfile();
+  EXPECT_NOT_NULL(log_capture);
+  log_set_file(log_capture);
+  EXPECT_TRUE(array_list_add(cfg->filters, str_dup("- *.bak")));
+  EXPECT_FALSE(validate_config(cfg)); /* one over the limit is rejected */
+  fflush(log_capture);
+  rewind(log_capture);
+  char line[512];
+  bool saw_message = false;
+  while (fgets(line, sizeof(line), log_capture) != NULL) {
+    if (strstr(line, "too many filter rules") != NULL && strstr(line, "(maximum 1024)") != NULL)
+      saw_message = true;
+  }
+  log_set_file(NULL);
+  fclose(log_capture);
+  EXPECT_TRUE(saw_message);
+
+  config_delete(cfg);
+}
+
 /* Test main() with --help flag (early return path, no server connection needed) */
 static void test_cli_help() {
   /* We can't easily call main() because it calls send_files which needs a server.
@@ -4824,6 +4856,7 @@ void test_client_cli() {
   test_validate_config_credentials_require_tls_or_loopback();
   test_validate_config_delta_sendfile_constraints();
   test_validate_config_unified_invariants();
+  test_validate_config_filter_rule_limit();
   test_cli_help();
   test_cli_archive_flags();
   test_cli_dry_run();