Extend santize into hybrid

server/lib/sanitize.ts

@@ -0,0 +1,40 @@
+/**
+ * Sanitize a string field before inserting into a database TEXT column.
+ *
+ * Two passes are applied:
+ *
+ * 1. Lone UTF-16 surrogates – JavaScript strings can hold unpaired surrogates
+ *    (e.g. \uD800 without a following \uDC00-\uDFFF codepoint). These are
+ *    valid in JS but cannot be encoded as UTF-8, triggering
+ *    `report_invalid_encoding` in SQLite / Postgres. They are replaced with
+ *    the Unicode replacement character U+FFFD so the data is preserved as a
+ *    visible signal that something was malformed.
+ *
+ * 2. Null bytes and C0 control characters – SQLite stores TEXT as
+ *    null-terminated C strings, so \x00 in a value causes
+ *    `report_invalid_encoding`. Bots and scanners routinely inject null bytes
+ *    into URLs (e.g. `/path\u0000.jpg`). All C0 control characters in the
+ *    range \x00-\x1F are stripped except for the three that are legitimate in
+ *    text payloads: HT (\x09), LF (\x0A), and CR (\x0D). DEL (\x7F) is also
+ *    stripped.
+ */
+export function sanitizeString(value: string): string;
+export function sanitizeString(
+    value: string | null | undefined
+): string | undefined;
+export function sanitizeString(
+    value: string | null | undefined
+): string | undefined {
+    if (value == null) return undefined;
+    return (
+        value
+            // Replace lone high surrogates (not followed by a low surrogate)
+            // and lone low surrogates (not preceded by a high surrogate).
+            .replace(
+                /[\uD800-\uDBFF](?![\uDC00-\uDFFF])|(?<![\uD800-\uDBFF])[\uDC00-\uDFFF]/g,
+                "\uFFFD"
+            )
+            // Strip null bytes, C0 control chars (except HT/LF/CR), and DEL.
+            .replace(/[\x00-\x08\x0B\x0C\x0E-\x1F\x7F]/g, "")
+    );
+}