Bug 1781116 - QuotaManager needs to deal with SQLite path canonicalization/symlink piercing; r=asuth,dom-storage-reviewers

Depends on D171440

Differential Revision: https://phabricator.services.mozilla.com/D171869

modules/libpref/init/StaticPrefList.yaml

@@ -3415,7 +3415,7 @@
   value: false
   mirror: always
 
-#ifdef XP_WIN
+#if defined(XP_WIN)
   # Preference that is used to set nsILocalFileWin::useDOSDevicePathSyntax
   # attribute for all local file instances created by QuotaManager and its
   # clients. The value of this preference is cached so changing the preference
@@ -3433,6 +3433,13 @@
     type: RelaxedAtomicBool
     value: true
     mirror: always
+#elif defined(XP_UNIX)
+  # Preference that is used to enable the overriding of Unix xFullPathname
+  # implementation in QuotaVFS.
+-   name: dom.quotaManager.overrideXFullPathnameUnix
+    type: RelaxedAtomicBool
+    value: true
+    mirror: always
 #endif
 
 # How many times we should retry directory removal or renaming if access was

storage/QuotaVFS.cpp

@@ -8,10 +8,12 @@
 #include "mozilla/dom/quota/PersistenceType.h"
 #include "mozilla/dom/quota/QuotaManager.h"
 #include "mozilla/dom/quota/QuotaObject.h"
+#include "mozilla/dom/quota/ResultExtensions.h"
+#include "nsDirectoryServiceDefs.h"
 #include "nsEscape.h"
 #include "mozilla/StaticPrefs_storage.h"
 
-#ifdef XP_WIN
+#if defined(XP_WIN) || defined(XP_UNIX)
 #  include "mozilla/StaticPrefs_dom.h"
 #endif
 
@@ -428,6 +430,60 @@ int QuotaFullPathname(sqlite3_vfs* vfs, const char* zName, int nOut,
     }
     zOut[index] = '\0';
 
+    return SQLITE_OK;
+  }
+#elif defined(XP_UNIX)
+  // SQLite canonicalizes (resolves path components) file paths on Unix which
+  // doesn't work well with file path sanity checks in quota manager. This is
+  // especially a problem on mac where /var is a symlink to /private/var.
+  // Since QuotaVFS is used only by quota clients which never access databases
+  // outside of PROFILE/storage, we override Unix xFullPathname with own
+  // implementation that doesn't do any canonicalization.
+
+  if (StaticPrefs::dom_quotaManager_overrideXFullPathnameUnix()) {
+    if (nOut < 0) {
+      // Match the return code used by SQLite's xFullPathname implementation
+      // here and below.
+      return SQLITE_CANTOPEN;
+    }
+
+    QM_TRY_INSPECT(
+        const auto& path, ([&zName]() -> Result<nsString, nsresult> {
+          NS_ConvertUTF8toUTF16 name(zName);
+
+          if (name.First() == '/') {
+            return name;
+          }
+
+          QM_TRY_INSPECT(const auto& file,
+                         MOZ_TO_RESULT_INVOKE_TYPED(nsCOMPtr<nsIFile>,
+                                                    NS_GetSpecialDirectory,
+                                                    NS_OS_CURRENT_WORKING_DIR));
+
+          QM_TRY(MOZ_TO_RESULT(file->Append(name)));
+
+          QM_TRY_RETURN(
+              MOZ_TO_RESULT_INVOKE_MEMBER_TYPED(nsString, file, GetPath));
+        }()),
+        SQLITE_CANTOPEN);
+
+    QM_TRY_INSPECT(const auto& quotaFile, QM_NewLocalFile(path),
+                   SQLITE_CANTOPEN);
+
+    QM_TRY_INSPECT(
+        const auto& quotaPath,
+        MOZ_TO_RESULT_INVOKE_MEMBER_TYPED(nsString, quotaFile, GetPath),
+        SQLITE_CANTOPEN);
+
+    NS_ConvertUTF16toUTF8 sqlitePath(quotaPath);
+
+    if (sqlitePath.Length() > (unsigned int)nOut) {
+      return SQLITE_CANTOPEN;
+    }
+
+    nsCharTraits<char>::copy(zOut, sqlitePath.get(), sqlitePath.Length());
+    zOut[sqlitePath.Length()] = '\0';
+
     return SQLITE_OK;
   }
 #endif