Make the declaration of clear() in base classes pure virtual. So if an

implementation wishes to make this operation a no-op it has to explicitly
declare it as such, rather than just letting the no-op default in from
the base class. (Falko Strenzke was the one who pointed out this was
potentially problematic.)

2 files changed, 7 insertions, 5 deletions

diff --git a/include/base.h b/include/base.h
index 69bc71bca..9f63c0aad 100644
--- a/include/base.h
+++ b/include/base.h
@@ -49,7 +49,7 @@ class BOTAN_DLL BlockCipher : public SymmetricAlgorithm
       void decrypt(byte block[]) const { dec(block, block); }
 
       virtual BlockCipher* clone() const = 0;
-      virtual void clear() throw() {};
+      virtual void clear() throw() = 0;
 
       BlockCipher(u32bit, u32bit, u32bit = 0, u32bit = 1);
       virtual ~BlockCipher() {}
@@ -74,7 +74,7 @@ class BOTAN_DLL StreamCipher : public SymmetricAlgorithm
       virtual void seek(u32bit);
 
       virtual StreamCipher* clone() const = 0;
-      virtual void clear() throw() {};
+      virtual void clear() throw() = 0;
 
       StreamCipher(u32bit, u32bit = 0, u32bit = 1, u32bit = 0);
       virtual ~StreamCipher() {}
@@ -115,7 +115,7 @@ class BOTAN_DLL HashFunction : public BufferedComputation
 
       virtual HashFunction* clone() const = 0;
       virtual std::string name() const = 0;
-      virtual void clear() throw() {};
+      virtual void clear() throw() = 0;
 
       HashFunction(u32bit, u32bit = 0);
       virtual ~HashFunction() {}
@@ -132,7 +132,7 @@ class BOTAN_DLL MessageAuthenticationCode : public BufferedComputation,
 
       virtual MessageAuthenticationCode* clone() const = 0;
       virtual std::string name() const = 0;
-      virtual void clear() throw() {};
+      virtual void clear() throw() = 0;
 
       MessageAuthenticationCode(u32bit, u32bit, u32bit = 0, u32bit = 1);
       virtual ~MessageAuthenticationCode() {}
diff --git a/include/rng.h b/include/rng.h
index e9a6f4a6c..f8b9a7f62 100644
--- a/include/rng.h
+++ b/include/rng.h
@@ -31,7 +31,7 @@ class BOTAN_DLL RandomNumberGenerator
 
       virtual void randomize(byte[], u32bit) = 0;
       virtual bool is_seeded() const = 0;
-      virtual void clear() throw() {};
+      virtual void clear() throw() = 0;
 
       byte next_byte();
 
@@ -54,6 +54,8 @@ class BOTAN_DLL Null_RNG : public RandomNumberGenerator
    {
    public:
       void randomize(byte[], u32bit) { throw PRNG_Unseeded("Null_RNG"); }
+      void clear() throw() {};
+
       bool is_seeded() const { return false; }
       void add_entropy(const byte[], u32bit) {}
       void add_entropy_source(EntropySource* es) { delete es; }