Fix disabled vanity field

internal/server/server_test.go

@@ -1627,6 +1627,65 @@ func TestUploadPageKeepsTheOneOffTokenField(t *testing.T) {
 	}
 }
 
+// The server reads the multipart body as a stream and stops at the file part,
+// so anything the upload depends on has to be in the markup ahead of it. The
+// form is laid out to look otherwise, which is exactly why this is pinned: a
+// tidy-up that moves the drop zone back up in the markup would silently strip
+// the expiry, the custom name and the one-off token from every upload.
+func TestUploadFormSendsTheFileLast(t *testing.T) {
+	h := newHarness(t, nil)
+	resp := h.get(t, "/", "")
+	raw, _ := io.ReadAll(resp.Body)
+	resp.Body.Close()
+	page := string(raw)
+
+	file := strings.Index(page, `name="file"`)
+	if file < 0 {
+		t.Fatal("the upload form has no file field")
+	}
+	for _, field := range []string{"expiry", "vanity", "token"} {
+		at := strings.Index(page, `name="`+field+`"`)
+		if at < 0 {
+			t.Errorf("the upload form has no %s field", field)
+			continue
+		}
+		if at > file {
+			t.Errorf("the %s field follows the file part, where the server can no longer read it", field)
+		}
+	}
+}
+
+// Anonymous visitors may type a custom name: the token that permits it can be
+// supplied in the same form, for this upload only. The rule itself is the
+// server's to enforce, not the markup's.
+func TestCustomNameFieldIsAlwaysUsable(t *testing.T) {
+	h := newHarness(t, nil)
+	resp := h.get(t, "/", "")
+	raw, _ := io.ReadAll(resp.Body)
+	resp.Body.Close()
+
+	form := string(raw)
+	if i := strings.Index(form, `name="vanity"`); i < 0 {
+		t.Fatal("the upload form has no custom name field")
+	} else if j := strings.Index(form[i:], ">"); strings.Contains(form[i:i+j], "disabled") {
+		t.Error("the custom name field is disabled, so a one-off token cannot be used with it")
+	}
+
+	// Enabled in the page, still refused on the wire without a token.
+	res := h.formUpload(t, map[string]string{"vanity": "anonymous-pick"}, "f.txt", "hello")
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusForbidden {
+		t.Errorf("anonymous vanity upload = %s, want 403", res.Status)
+	}
+
+	// And accepted when the form carries a token that allows it.
+	res2 := h.formUpload(t, map[string]string{"vanity": "chosen-name", "token": h.token}, "f.txt", "hello")
+	defer res2.Body.Close()
+	if res2.StatusCode != http.StatusCreated {
+		t.Errorf("one-off token vanity upload = %s, want 201", res2.Status)
+	}
+}
+
 // A chosen passphrase has to work everywhere a generated token does: at the
 // login form, on an upload, and as a session.
 func TestChosenPassphraseWorksEndToEnd(t *testing.T) {

web/static/app.js

@@ -108,8 +108,9 @@
     submit.disabled = true;
     progress.hidden = false;
 
-    // FormData follows DOM order, so the token, expiry and vanity fields all
+    // FormData follows markup order, not painted order, so the options and the
-    // precede the file part, which is exactly what the server requires.
+    // token precede the file part exactly as the server requires. The drop
+    // zone only looks like it comes first; see the order rules in style.css.
     var data = new FormData(form);
     var started = Date.now();
 

web/static/style.css

@@ -77,6 +77,14 @@ input[type=text], input[type=password] {
 .row { display: flex; gap: 1rem; flex-wrap: wrap; }
 .row > .field { flex: 1 1 12rem; }
 
+/* The file input has to be the last part in the submitted body, so it sits at
+   the bottom of the form's markup and is lifted back to the top here. Only the
+   painting order moves; the submission order, which the server depends on, is
+   the markup's. */
+#upload { display: flex; flex-direction: column; }
+#upload > .drop { order: -1; }
+#upload > button { align-self: flex-start; }
+
 .drop {
   border: 2px dashed var(--line);
   border-radius: var(--radius);

web/templates/index.html

@@ -6,10 +6,10 @@
 <form id="upload" class="card" method="post" action="{{.Base}}api/upload"
       enctype="multipart/form-data" data-max-size="{{.MaxSizeBytes}}">
 
-  <div class="drop" id="drop">
+  <!-- Field order is load-bearing: the server streams this body rather than
-    <input type="file" name="file" id="file" required>
+       spooling it, so every option and the token have to arrive before the
-    <p class="hint" id="drop-hint">Choose a file, or drop one here.</p>
+       file part does. The drop zone is lifted back to the top of the card with
-  </div>
+       CSS order, which changes what is seen without changing what is sent. -->
 
   <div class="row">
     <label class="field">
@@ -19,7 +19,7 @@
     <label class="field">
       <span>Custom name <em>({{if .AllowVanity}}optional{{else}}needs a token{{end}})</em></span>
       <input type="text" name="vanity" id="vanity" placeholder="auto" autocomplete="off"
-             pattern="[A-Za-z0-9][A-Za-z0-9._-]{1,63}"{{if not .AllowVanity}} disabled{{end}}>
+             pattern="[A-Za-z0-9][A-Za-z0-9._-]{1,63}">
     </label>
   </div>
 
@@ -35,6 +35,11 @@
     </label>
   </details>
 
+  <div class="drop" id="drop">
+    <input type="file" name="file" id="file" required>
+    <p class="hint" id="drop-hint">Choose a file, or drop one here.</p>
+  </div>
+
   <div class="progress" id="progress" hidden>
     <div class="bar"><div class="fill" id="bar-fill"></div></div>
     <p class="hint" id="progress-text"></p>