[gparted] Add unit testing of erasing all passwords (#795617)

[Curtis Gedak <gedakc src gnome org>]

commit d2a2ebe4a189a86dace668092adc8b200931c7b4
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Fri Nov 10 07:39:04 2017 +0000

    Add unit testing of erasing all passwords (#795617)
    
    Test that all passwords are zeroed by PasswordRAMStore::erase_all(), the
    same method as used in the PasswordRAMStore destructor.
    
    Bug 795617 - Implement opening and closing of LUKS mappings

 include/PasswordRAMStore.h     |    6 ++++++
 src/PasswordRAMStore.cc        |    9 ++++++++-
 tests/test_PasswordRAMStore.cc |   28 ++++++++++++++++++++++------
 3 files changed, 36 insertions(+), 7 deletions(-)
---
diff --git a/include/PasswordRAMStore.h b/include/PasswordRAMStore.h
index acfabb8..c8d67da 100644
--- a/include/PasswordRAMStore.h
+++ b/include/PasswordRAMStore.h
@@ -36,10 +36,16 @@ namespace GParted
 
 class PasswordRAMStore
 {
+friend class PasswordRAMStoreTest;  // To allow unit testing PasswordRAMStoreTest class
+                                    // access to private erase_all() method.
+
 public:
        static bool insert( const Glib::ustring & key, const char * password );
        static bool erase( const Glib::ustring & key );
        static const char * lookup( const Glib::ustring & key );
+
+private:
+       static void erase_all();
 };
 
 } //GParted
diff --git a/src/PasswordRAMStore.cc b/src/PasswordRAMStore.cc
index de28702..8125b15 100644
--- a/src/PasswordRAMStore.cc
+++ b/src/PasswordRAMStore.cc
@@ -44,10 +44,10 @@ public:
        bool insert( const Glib::ustring & key, const char * password );
        bool erase( const Glib::ustring & key );
        const char * lookup( const Glib::ustring & key );
+       void erase_all();
 
 private:
        iterator find_key( const Glib::ustring & key );
-       void erase_all();
 
        std::vector<PWEntry> pw_entries;     // Linear vector of password entries
        char *               protected_mem;  // Block of virtual memory locked into RAM
@@ -212,4 +212,11 @@ const char * PasswordRAMStore::lookup( const Glib::ustring & key )
        return single_pwstore.lookup( key );
 }
 
+// PasswordRAMStore private methods
+
+void PasswordRAMStore::erase_all()
+{
+       single_pwstore.erase_all();
+}
+
 } //GParted
diff --git a/tests/test_PasswordRAMStore.cc b/tests/test_PasswordRAMStore.cc
index 78a4360..08e54da 100644
--- a/tests/test_PasswordRAMStore.cc
+++ b/tests/test_PasswordRAMStore.cc
@@ -17,12 +17,10 @@
 /* Test PasswordRAMStore
  *
  * WARNING:
- * This unit testing only calls the public API of the PasswordRAMStore so would normally
- * be black box testing, however knowledge of the implementation is used to look through
- * the API to the internals making this white box testing.  This is so that the hidden
- * behaviour of zeroing password storing memory before and after use can be tested.
- * FIXME: Can't currently test memory is zeroed when the password store is destroyed
- * because destructor zeros memory AND removes it from the process address space.
+ * This unit testing calls the public API of PasswordRAMStore and also the private member.
+ * It also uses knowledge of the implementation to look through the API to the internals
+ * making this white box testing.  This is so that the hidden behaviour of zeroing
+ * password storing memory before and after use can be tested.
  *
  * WARNING:
  * Each test fixture would normally initialise separate resources to make the tests
@@ -85,6 +83,8 @@ protected:
 
        static void SetUpTestCase();
 
+       static void erase_all()  { PasswordRAMStore::erase_all(); };
+
        static const char *  protected_mem;
 
        std::string pw;
@@ -262,4 +262,20 @@ TEST_F( PasswordRAMStoreTest, TooLongPassword )
        EXPECT_TRUE( mem_is_zero( protected_mem, ProtectedMemSize ) );
 }
 
+TEST_F( PasswordRAMStoreTest, TotalErasure )
+{
+       // Test all passwords are erased (and zeroed using the same code called during
+       // password cache destruction).
+       unsigned int i;
+       for ( i = 0 ; i < 100 ; i ++ )
+       {
+               pw = gen_passwd( i );
+               EXPECT_TRUE( PasswordRAMStore::insert( gen_key(i), pw.c_str() ) );
+       }
+       EXPECT_FALSE( mem_is_zero( protected_mem, ProtectedMemSize ) );
+
+       PasswordRAMStoreTest::erase_all();
+       EXPECT_TRUE( mem_is_zero( protected_mem, ProtectedMemSize ) );
+}
+
 }  // namespace GParted