Remove ?token= deletion-token path (#143)

The deletion token was accepted via the ?token= query parameter on both
DELETE /api/pastes/{id} and /redeem, and round-tripped through the paste
URL after creation. URL-carried bearer secrets leak into reverse-proxy
access logs and browser history.

- API: deletion tokens are now accepted only via the Authorization header
  (Bearer/Token/bare); query params are ignored on both endpoints
- Web create flow: token moves to the browser via a short-lived tok_<id>
  HttpOnly cookie instead of the redirect URL; the paste view reads it
  from the cookie, never from ?token=
- Web view: the delete button calls redeem() which takes the token from
  sessionStorage and sends it as an Authorization header
- Tests: correct token in query must be rejected (403/400); header path
  still deletes/redeems; extraction unit cases updated

Fixes #143

internal/api/delete_auth_test.go

@@ -1,9 +1,10 @@
 package api
 
-// Regression tests for #63: DELETE /api/pastes/{id} must require the
-// deletion token (Authorization header or ?token= query param, constant-time
-// compare). Without a token, or with a wrong token, the paste must survive
-// and the response must be 403.
+// Regression tests for #63 and #143: DELETE /api/pastes/{id} must require the
+// deletion token in the Authorization header (constant-time compare). The
+// ?token= query parameter is NOT accepted (#143): URL-carried tokens leak
+// into access logs and browser history. Without a token, or with a wrong
+// token, the paste must survive and the response must be 403.
 
 import (
 	"encoding/json"
@@ -68,10 +69,14 @@ func TestDeleteWithWrongTokenForbidden(t *testing.T) {
 	h := s.routes()
 	id, _ := createTestPaste(t, h)
 
-	// query param
-	rec := doReq(t, h, "DELETE", "/api/pastes/"+id+"?token=wrong-token", "", "")
+	// query param: even the CORRECT token must be rejected now (#143)
+	id2, tok2 := createTestPaste(t, h)
+	rec := doReq(t, h, "DELETE", "/api/pastes/"+id2+"?token="+tok2, "", "")
 	if rec.Code != http.StatusForbidden {
-		t.Fatalf("delete with wrong token (query): got %d want 403", rec.Code)
+		t.Fatalf("delete with correct token in query: got %d want 403 (#143)", rec.Code)
+	}
+	if !pasteExists(t, h, id2) {
+		t.Fatal("paste was deleted via ?token= query param (#143 regression)")
 	}
 	// header
 	req := httptest.NewRequest("DELETE", "/api/pastes/"+id, nil)
@@ -103,14 +108,43 @@ func TestDeleteWithCorrectToken(t *testing.T) {
 		t.Fatal("paste still exists after authorized delete")
 	}
 
-	// via query param
+	// query param: even with the correct token the delete must fail (#143)
 	id, tok = createTestPaste(t, h)
 	rec = doReq(t, h, "DELETE", "/api/pastes/"+id+"?token="+tok, "", "")
+	if rec.Code != http.StatusForbidden {
+		t.Fatalf("delete with correct token (query): got %d want 403 (#143)", rec.Code)
+	}
+	if !pasteExists(t, h, id) {
+		t.Fatal("paste was deleted via ?token= query param (#143 regression)")
+	}
+}
+
+// #143: the deletion token must be accepted via the Authorization header on
+// the redeem (hard delete) endpoint too.
+func TestRedeemWithCorrectTokenHeader(t *testing.T) {
+	s := testServer(t)
+	h := s.routes()
+	id, tok := createTestPaste(t, h)
+
+	req := httptest.NewRequest("DELETE", "/api/pastes/"+id+"/redeem", nil)
+	req.Header.Set("Authorization", "Bearer "+tok)
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
 	if rec.Code != 200 {
-		t.Fatalf("delete with correct token (query): got %d want 200", rec.Code)
+		t.Fatalf("redeem with correct token (header): got %d want 200: %s", rec.Code, rec.Body.String())
 	}
 	if pasteExists(t, h, id) {
-		t.Fatal("paste still exists after authorized delete (query)")
+		t.Fatal("paste still exists after authorized redeem")
+	}
+
+	// query param must NOT work on redeem either
+	id, tok = createTestPaste(t, h)
+	rec = doReq(t, h, "DELETE", "/api/pastes/"+id+"/redeem?token="+tok, "", "")
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("redeem via ?token= query: got %d want 400 (#143)", rec.Code)
+	}
+	if !pasteExists(t, h, id) {
+		t.Fatal("paste was hard-deleted via ?token= query param (#143 regression)")
 	}
 }
 
@@ -161,8 +195,8 @@ func TestDeletionAuthorizationExtract(t *testing.T) {
 		{"bearer tok", "", "tok"},
 		{"Token tok", "", "tok"},
 		{"tok", "", "tok"},
-		{"", "?token=q", "q"},
-		{"Bearer hdr", "?token=q", "hdr"}, // header wins
+		{"", "?token=q", ""},              // #143: query tokens are never accepted
+		{"Bearer hdr", "?token=q", "hdr"}, // header only
 	}
 	for _, c := range cases {
 		if got := deletionAuthorization(mk(c.hdr, c.q)); got != c.want {