按源保护 PythonPlugin TOPLEVEL 路径边界

core/wasm_shims/pythonplugin/python_plugin.cc

@@ -1,7 +1,12 @@
 #include "pythonplugin/python_plugin.hh"
 
+#include <algorithm>
 #include <cstdio>
 #include <cstdlib>
+#include <cstring>
+#include <limits.h>
+#include <string>
+#include <unistd.h>
 
 // LinuxCNC source basis: src/emc/pythonplugin/python_plugin.cc provides the
 // native PythonPlugin implementation called by RS274 Python/remap paths.
@@ -11,6 +16,61 @@ __attribute__((weak)) std::string handle_pyerror() {
 
 PythonPlugin *python_plugin = nullptr;
 
+namespace {
+
+std::string trim_ini_value(std::string value) {
+    const auto first = std::find_if_not(value.begin(), value.end(), [](unsigned char ch) {
+        return ch == ' ' || ch == '\t' || ch == '\r' || ch == '\n';
+    });
+    const auto last = std::find_if_not(value.rbegin(), value.rend(), [](unsigned char ch) {
+        return ch == ' ' || ch == '\t' || ch == '\r' || ch == '\n';
+    }).base();
+    if (first >= last) {
+        return {};
+    }
+    return std::string(first, last);
+}
+
+bool find_ini_value(const char *iniFilename,
+                    const char *section,
+                    const char *key,
+                    std::string &value) {
+    FILE *file = std::fopen(iniFilename, "r");
+    if (!file) {
+        return false;
+    }
+
+    bool in_section = false;
+    char line[PATH_MAX + 256];
+    while (std::fgets(line, sizeof(line), file)) {
+        std::string text = trim_ini_value(line);
+        if (text.empty() || text[0] == ';' || text[0] == '#') {
+            continue;
+        }
+        if (text.front() == '[' && text.back() == ']') {
+            in_section = text.substr(1, text.size() - 2) == section;
+            continue;
+        }
+        if (!in_section) {
+            continue;
+        }
+        const auto equals = text.find('=');
+        if (equals == std::string::npos) {
+            continue;
+        }
+        if (trim_ini_value(text.substr(0, equals)) == key) {
+            value = trim_ini_value(text.substr(equals + 1));
+            std::fclose(file);
+            return true;
+        }
+    }
+
+    std::fclose(file);
+    return false;
+}
+
+} // namespace
+
 PythonPlugin *PythonPlugin::instantiate(struct _inittab *) {
     static PythonPlugin plugin;
     python_plugin = &plugin;
@@ -42,6 +102,19 @@ int PythonPlugin::configure(const char *iniFilename, const char *section) {
     }
     std::fclose(file);
 
+    std::string toplevel;
+    if (find_ini_value(iniFilename, section, "TOPLEVEL", toplevel)) {
+        char resolved_path[PATH_MAX];
+        // LinuxCNC source basis: python_plugin.cc configure() expands and
+        // resolves [PYTHON] TOPLEVEL before initialize(); a missing path
+        // returns PLUGIN_BAD_PATH before Python runtime status is considered.
+        if (realpath(toplevel.c_str(), resolved_path) == nullptr) {
+            error_msg = "bad path";
+            status = PLUGIN_BAD_PATH;
+            return status;
+        }
+    }
+
     return initialize();
 }
 

core/wasm_shims/pythonplugin/python_plugin_probe_main.cc

@@ -60,6 +60,32 @@ int main() {
         std::fputs("[PYTHON]\n", file);
         std::fclose(file);
     }
+    const char *bad_path_ini = "/tmp/cnc_sim_python_plugin_probe_bad_path.ini";
+    {
+        FILE *file = std::fopen(bad_path_ini, "w");
+        if (!file) {
+            std::remove(ini);
+            return 33;
+        }
+        std::fputs("[PYTHON]\nTOPLEVEL = /tmp/cnc_sim_missing_python_toplevel.py\n", file);
+        std::fclose(file);
+    }
+    if (plugin->configure(bad_path_ini, "PYTHON") != PLUGIN_BAD_PATH) {
+        std::remove(ini);
+        std::remove(bad_path_ini);
+        return 34;
+    }
+    if (plugin->usable()) {
+        std::remove(ini);
+        std::remove(bad_path_ini);
+        return 35;
+    }
+    if (plugin->last_errmsg() != "bad path") {
+        std::remove(ini);
+        std::remove(bad_path_ini);
+        return 36;
+    }
+    std::remove(bad_path_ini);
     setenv("INI_FILE_NAME", ini, 1);
     if (plugin->configure(nullptr, "PYTHON") != PLUGIN_PYTHON_NOT_INITIALIZED) {
         std::remove(ini);