Refactor random data generation

Add new RandomDataProvider object and implement existing random number
generation in terms of that.  This enables end users to supply their
own random data providers.

2 files changed, 52 insertions, 0 deletions

diff --git a/include/qpdf/QUtil.hh b/include/qpdf/QUtil.hh
index cbdc065c..f61fa844 100644
--- a/include/qpdf/QUtil.hh
+++ b/include/qpdf/QUtil.hh
@@ -15,6 +15,8 @@
 #include <stdexcept>
 #include <stdio.h>
 
+class RandomDataProvider;
+
 namespace QUtil
 {
     // This is a collection of useful utility functions that don't
@@ -123,8 +125,26 @@ namespace QUtil
     QPDF_DLL
     void srandom(unsigned int seed);
 
+    // Initialize a buffer with random bytes.  By default, qpdf tries
+    // to use a secure random number source.  It can be configured at
+    // compile time to use an insecure random number source (from
+    // stdlib).  You can also call setRandomDataProvider with a
+    // RandomDataProvider, in which case this method will get its
+    // random bytes from that.
+
     QPDF_DLL
     void initializeWithRandomBytes(unsigned char* data, size_t len);
+
+    // Supply a random data provider.  If not supplied, depending on
+    // compile time options, qpdf will either use the operating
+    // system's secure random number source or an insecure random
+    // source from stdlib.  The caller is responsible for managing the
+    // memory for the RandomDataProvider.  This method modifies a
+    // static variable.  If you are providing your own random data
+    // provider, you should call this at the beginning of your program
+    // before creating any QPDF objects.
+    QPDF_DLL
+    void setRandomDataProvider(RandomDataProvider*);
 };
 
 #endif // __QUTIL_HH__
diff --git a/include/qpdf/RandomDataProvider.hh b/include/qpdf/RandomDataProvider.hh
new file mode 100644
index 00000000..68c9cb6e
--- /dev/null
+++ b/include/qpdf/RandomDataProvider.hh
@@ -0,0 +1,32 @@
+/* Copyright (c) 2005-2013 Jay Berkenbilt
+ *
+ * This file is part of qpdf.  This software may be distributed under
+ * the terms of version 2 of the Artistic License which may be found
+ * in the source distribution.  It is provided "as is" without express
+ * or implied warranty.
+ */
+
+#ifndef __RANDOMDATAPROVIDER_HH__
+#define __RANDOMDATAPROVIDER_HH__
+
+#include <string.h> // for size_t
+
+class RandomDataProvider
+{
+  public:
+    virtual ~RandomDataProvider()
+    {
+    }
+    virtual void provideRandomData(unsigned char* data, size_t len) = 0;
+
+  protected:
+    RandomDataProvider()
+    {
+    }
+
+  private:
+    RandomDataProvider(RandomDataProvider const&);
+    RandomDataProvider& operator=(RandomDataProvider const&);
+};
+
+#endif // __RANDOMDATAPROVIDER_HH__