Bug 1754320 - Re-escape existing escape sequences in precursor origins, r=ckerschb

Apparently the esc_NonASCIIOnly and esc_Forced flags to NS_EscapeURL are
incompatible, meaning that the escaping and unescaping code was not
handling existing escape sequences properly. This patch adds an explicit
gtest to make sure sequences round-trip correctly, and switches
serialization to use `esc_Query | esc_Forced` instead, which may escape
more aggressively than required but should work correctly.

Differential Revision: https://phabricator.services.mozilla.com/D142111

caps/NullPrincipal.cpp

@@ -76,18 +76,17 @@ already_AddRefed<NullPrincipal> NullPrincipal::CreateWithoutOriginAttributes() {
   return NullPrincipal::Create(OriginAttributes(), nullptr);
 }
 
-static void EscapePrecursorQuery(nsACString& aPrecursorQuery) {
+void NullPrincipal::EscapePrecursorQuery(nsACString& aPrecursorQuery) {
   // origins should not contain existing escape sequences, so set `esc_Forced`
   // to force any `%` in the input to be escaped in addition to non-ascii,
   // control characters and DEL.
   nsCString modified;
-  if (NS_EscapeURLSpan(aPrecursorQuery, esc_OnlyNonASCII | esc_Forced,
-                       modified)) {
+  if (NS_EscapeURLSpan(aPrecursorQuery, esc_Query | esc_Forced, modified)) {
     aPrecursorQuery.Assign(std::move(modified));
   }
 }
 
-static void UnescapePrecursorQuery(nsACString& aPrecursorQuery) {
+void NullPrincipal::UnescapePrecursorQuery(nsACString& aPrecursorQuery) {
   nsCString modified;
   if (NS_UnescapeURL(aPrecursorQuery.BeginReading(), aPrecursorQuery.Length(),
                      /* aFlags */ 0, modified)) {

caps/NullPrincipal.h

@@ -116,6 +116,10 @@ class NullPrincipal final : public BasePrincipal {
 
  private:
   FRIEND_TEST(OriginAttributes, NullPrincipal);
+  FRIEND_TEST(NullPrincipalPrecursor, EscapingRoundTrips);
+
+  static void EscapePrecursorQuery(nsACString& aPrecursorQuery);
+  static void UnescapePrecursorQuery(nsACString& aPrecursorQuery);
 
   // If aIsFirstParty is true, this NullPrincipal will be initialized based on
   // the aOriginAttributes with FirstPartyDomain set to a unique value.  This

caps/tests/gtest/TestNullPrincipalPrecursor.cpp

@@ -0,0 +1,55 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "gtest/gtest.h"
+#include "mozilla/NullPrincipal.h"
+#include "nsIURIMutator.h"
+#include "nsPrintfCString.h"
+
+namespace mozilla {
+
+TEST(NullPrincipalPrecursor, EscapingRoundTrips)
+{
+  nsTArray<nsCString> inputs;
+
+  inputs.AppendElements(mozilla::Span(std::array{
+      "mailbox:///dev/shm/tmp5wkt9ff_.mozrunner/Mail/Local%20Folders/secure-mail?number=5"_ns,
+  }));
+
+  // Add a string for every ASCII byte both escaped and unescaped.
+  for (uint8_t c = 0; c < 128; ++c) {
+    inputs.AppendElement(nsPrintfCString("%02X: %c", c, (char)c));
+    inputs.AppendElement(nsPrintfCString("%02X: %%%02X", c, c));
+  }
+
+  nsID dummyID{0xddf15eaf,
+               0x3837,
+               0x4678,
+               {0x80, 0x3b, 0x86, 0x86, 0xe8, 0x17, 0x66, 0x71}};
+  nsCOMPtr<nsIURI> baseURI = NullPrincipal::CreateURI(nullptr, &dummyID);
+  ASSERT_TRUE(baseURI);
+
+  for (auto& input : inputs) {
+    // First build an escaped version of the input string using
+    // `EscapePrecursorQuery`.
+    nsCString escaped(input);
+    NullPrincipal::EscapePrecursorQuery(escaped);
+
+    // Make sure that this escaped URI round-trips through a `moz-nullprincipal`
+    // URI's query without any additional escapes.
+    nsCOMPtr<nsIURI> clone;
+    EXPECT_TRUE(
+        NS_SUCCEEDED(NS_MutateURI(baseURI).SetQuery(escaped).Finalize(clone)));
+    nsCString query;
+    EXPECT_TRUE(NS_SUCCEEDED(clone->GetQuery(query)));
+    EXPECT_EQ(escaped, query);
+
+    // Try to unescape our escaped URI and make sure we recover the input
+    // string.
+    nsCString unescaped(escaped);
+    NullPrincipal::UnescapePrecursorQuery(unescaped);
+    EXPECT_EQ(input, unescaped);
+  }
+}
+
+}  // namespace mozilla

caps/tests/gtest/moz.build

@@ -5,6 +5,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 UNIFIED_SOURCES += [
+    "TestNullPrincipalPrecursor.cpp",
     "TestOriginAttributes.cpp",
     "TestPrincipalAttributes.cpp",
     "TestPrincipalSerialization.cpp",