4 files changed, 25 insertions, 1 deletions
diff --git a/src/liolib.c b/src/liolib.c
index feeeb8f..7824a58 100644
--- a/src/liolib.c
+++ b/src/liolib.c
@@ -139,7 +139,11 @@ static int io_open (lua_State *L) {
   /* other filenames starting with teliva_ are never ok (reserved for the
    * framework, should not be accessed by apps directly */
   else if (starts_with(filename, "teliva_")) {
-    snprintf(iolib_errbuf, 1024, "app tried to open file '%s'; that's never allowed for filenames starting with 'teliva_'", filename);
+    snprintf(iolib_errbuf, 1024, "app tried to open file '%s'; relative paths are never allowed", filename);
+    Previous_message = iolib_errbuf;
+  }
+  else if (contains(filename, "./")) {
+    snprintf(iolib_errbuf, 1024, "app tried to open file '%s'; relative paths are never allowed", filename);
     Previous_message = iolib_errbuf;
   }
   else if (file_operation_permitted(filename, mode)) {
diff --git a/src/loslib.c b/src/loslib.c
index 4715daa..530af6b 100644
--- a/src/loslib.c
+++ b/src/loslib.c
@@ -47,6 +47,11 @@ static int os_remove (lua_State *L) {
     Previous_message = oslib_errbuf;
     return os_pushresult(L, 0, filename);
   }
+  else if (contains(filename, "./")) {
+    snprintf(oslib_errbuf, 1024, "app tried to remove file '%s'; relative paths are never allowed", filename);
+    Previous_message = oslib_errbuf;
+    return os_pushresult(L, 0, filename);
+  }
   else if (!file_operation_permitted(filename, "w")) {
     snprintf(oslib_errbuf, 1024, "app tried to remove file '%s'; give it write permissions (ctrl-p) if that is expected", filename);
     Previous_message = oslib_errbuf;
@@ -69,6 +74,11 @@ static int os_rename (lua_State *L) {
     Previous_message = oslib_errbuf;
     return os_pushresult(L, 0, fromname);
   }
+  else if (contains(fromname, "./")) {
+    snprintf(oslib_errbuf, 1024, "app tried to rename file '%s'; relative paths are never allowed", fromname);
+    Previous_message = oslib_errbuf;
+    return os_pushresult(L, 0, fromname);
+  }
   else if (!file_operation_permitted(fromname, "r")) {
     snprintf(oslib_errbuf, 1024, "app tried to rename file '%s'; give it read permissions (ctrl-p) if that is expected", fromname);
     Previous_message = oslib_errbuf;
@@ -82,6 +92,11 @@ static int os_rename (lua_State *L) {
     Previous_message = oslib_errbuf;
     return os_pushresult(L, 0, toname);
   }
+  else if (contains(fromname, "./")) {
+    snprintf(oslib_errbuf, 1024, "app tried to rename to file '%s'; relative paths are never allowed", toname);
+    Previous_message = oslib_errbuf;
+    return os_pushresult(L, 0, toname);
+  }
   else if (!file_operation_permitted(toname, "w")) {
     snprintf(oslib_errbuf, 1024, "app tried to rename to file '%s'; give it write permissions (ctrl-p) if that is expected", toname);
     Previous_message = oslib_errbuf;
diff --git a/src/teliva.c b/src/teliva.c
index b88a42b..4ad530e 100644
--- a/src/teliva.c
+++ b/src/teliva.c
@@ -23,6 +23,10 @@ int starts_with(const char* s, const char* prefix) {
   return strncmp(s, prefix, strlen(prefix)) == 0;
 }
 
+int contains(const char* s, const char* sub) {
+  return strstr(s, sub) != NULL;
+}
+
 /*** Standard UI elements */
 
 int menu_column = 0;
diff --git a/src/teliva.h b/src/teliva.h
index 6777240..7455cfc 100644
--- a/src/teliva.h
+++ b/src/teliva.h
@@ -189,5 +189,6 @@ extern void render_previous_error(void);
 
 /* Misc */
 extern int starts_with(const char* s, const char* prefix);
+extern int contains(const char* s, const char* sub);
 
 #endif