[Boost-bugs] [Boost C++ Libraries] #5187: uuid\seed_rng.hpp sha1_random_digest_state_ not random

Subject: [Boost-bugs] [Boost C++ Libraries] #5187: uuid\seed_rng.hpp sha1_random_digest_state_ not random
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2011-02-14 08:09:54

#5187: uuid\seed_rng.hpp sha1_random_digest_state_ not random
-------------------------------------------+--------------------------------
 Reporter:  qiaozhiqiang@…                 |       Owner:         
     Type:  Bugs                           |      Status:  new    
Milestone:  To Be Determined               |   Component:  None   
  Version:  Boost 1.45.0                   |    Severity:  Problem
 Keywords:  seed_rng                       |  
-------------------------------------------+--------------------------------
 boost_1_45_0\boost\uuid\seed_rng.hpp

 static unsigned int * sha1_random_digest_state_()
     {
         // intentionally left uninitialized
         // ERROR 1: not uninitialized! static value always zero all.
         // ERROR 2: always return the same pointer of static value
         // should delete 'static'
         static unsigned int state[ 5 ];
         return state;
     }


 unsigned int * ps = sha1_random_digest_state_();

         unsigned int state[ 5 ];

         std::memcpy( state, ps, sizeof( state ) ); // harmless data race

 // ERROR 1: not uninitialized! static value always zero all.
 // so state is all zero
         sha.process_bytes( (unsigned char const*)state, sizeof( state ) );

 // ERROR 2: always return the same pointer of static value
 //  so ps is same ( ps === ps)
         sha.process_bytes( (unsigned char const*)&ps, sizeof( ps ) );

 namespace boost {
 namespace uuids {
 namespace detail {

 // should this be part of Boost.Random?
 class seed_rng
 {
 static unsigned int * sha1_random_digest_state_()
     {
         // intentionally left uninitialized
         static unsigned int state[ 5 ];
         return state;
     }

     void sha1_random_digest_()
     {
         boost::uuids::detail::sha1 sha;

         unsigned int * ps = sha1_random_digest_state_();

         unsigned int state[ 5 ];
         std::memcpy( state, ps, sizeof( state ) ); // harmless data race

         sha.process_bytes( (unsigned char const*)state, sizeof( state ) );
         sha.process_bytes( (unsigned char const*)&ps, sizeof( ps ) );

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/5187>
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