exchange

commit bceed922d932287e66fe6d4538cbd21cb9208f06
parent 60323e2ceb2b585c6d3865458f39a8811e42b452
Author: Christian Grothoff <christian@grothoff.org>
Date:   Tue, 30 Jun 2026 10:46:09 +0200

check that form_name and version are well-formed

Diffstat:
M
src/mhd/mhd_typst.c
 | 
49
+++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 49 insertions(+), 0 deletions(-)
diff --git a/src/mhd/mhd_typst.c b/src/mhd/mhd_typst.c
@@ -542,6 +542,37 @@ typst_done_cb (void *cls,
 
 
 /**
+ * Check that @a id only consists of characters that are safe to
+ * interpolate into a Typst `#import` statement (alphanumerics and
+ * `.`, `-`, `_`).  This prevents code/path injection via the form
+ * name or version.
+ *
+ * @param id identifier to validate
+ * @return true if @a id is non-empty and only uses the safe charset
+ */
+static bool
+is_valid_form_identifier (const char *id)
+{
+  if ( (NULL == id) ||
+       ('\0' == id[0]) )
+    return false;
+  for (const char *p = id; '\0' != *p; p++)
+  {
+    char c = *p;
+
+    if (! ( ( ('a' <= c) && ('z' >= c)) ||
+            ( ('A' <= c) && ('Z' >= c)) ||
+            ( ('0' <= c) && ('9' >= c)) ||
+            ('.' == c) ||
+            ('-' == c) ||
+            ('_' == c) ) )
+      return false;
+  }
+  return true;
+}
+
+
+/**
  * Setup typst stage to produce one of the PDF inputs.
  *
  * @param[out] stage initialized stage data
@@ -572,6 +603,24 @@ setup_stage (struct TypstStage *stage,
                              doc->data);
   }
 
+  if (! is_valid_form_identifier (doc->form_name))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Stage %u: Invalid form name `%s'\n",
+                i,
+                doc->form_name);
+    return false;
+  }
+  if ( (NULL != doc->form_version) &&
+       (! is_valid_form_identifier (doc->form_version)) )
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Stage %u: Invalid form version `%s'\n",
+                i,
+                doc->form_version);
+    return false;
+  }
+
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Stage %u: Handling form %s\n",
               i,