Never call putenv() with data on the stack.

[tinc] / src / script.c

diff --git a/src/script.c b/src/script.c
index 55473b1..5ca5673 100644 (file)
--- a/src/script.c
+++ b/src/script.c
@@ -26,6 +26,43 @@
 #include "script.h"
 #include "xalloc.h"
 
+#ifdef HAVE_PUTENV
+static void unputenv(const char *p) {
+       const char *e = strchr(p, '=');
+       if(!e)
+               return;
+       int len = e - p;
+#ifndef HAVE_UNSETENV
+#ifdef HAVE_MINGW
+       // Windows requires putenv("FOO=") to unset %FOO%
+       len++;
+#endif
+#endif
+       char var[len + 1];
+       strncpy(var, p, len);
+       var[len] = 0;
+#ifdef HAVE_UNSETENV
+       unsetenv(var);
+#else
+       // We must keep what we putenv() around in memory.
+       // To do this without memory leaks, keep things in a list and reuse if possible.
+       static list_t list = {};
+       for list_each(char, data, &list) {
+               if(!strcmp(data, var)) {
+                       putenv(data);
+                       return;
+               }
+       }
+       char *data = xstrdup(var);
+       list_insert_tail(&list, data);
+       putenv(data);
+#endif
+}
+#else
+static void putenv(const char *p) {}
+static void unputenv(const char *p) {}
+#endif
+
 bool execute_script(const char *name, char **envp) {
 #ifdef HAVE_SYSTEM
        char scriptname[PATH_MAX];
@@ -67,12 +104,10 @@ bool execute_script(const char *name, char **envp) {
 
        logger(DEBUG_STATUS, LOG_INFO, "Executing script %s", name);
 
-#ifdef HAVE_PUTENV
        /* Set environment */
 
        for(int i = 0; envp[i]; i++)
                putenv(envp[i]);
-#endif
 
        if(scriptinterpreter)
                xasprintf(&command, "%s \"%s\"", scriptinterpreter, scriptname);
@@ -85,15 +120,8 @@ bool execute_script(const char *name, char **envp) {
 
        /* Unset environment */
 
-       for(int i = 0; envp[i]; i++) {
-               char *e = strchr(envp[i], '=');
-               if(e) {
-                       char p[e - envp[i] + 1];
-                       strncpy(p, envp[i], e - envp[i]);
-                       p[e - envp[i]] = '\0';
-                       putenv(p);
-               }
-       }
+       for(int i = 0; envp[i]; i++)
+               unputenv(envp[i]);
 
        if(status != -1) {
 #ifdef WEXITSTATUS