LCOV - code coverage report
Current view: directory - security/manager/boot/src - nsEntropyCollector.cpp (source / functions) Found Hit Coverage
Test: app.info Lines: 36 16 44.4 %
Date: 2012-06-02 Functions: 9 8 88.9 %

       1                 : /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
       2                 : /* ***** BEGIN LICENSE BLOCK *****
       3                 :  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
       4                 :  *
       5                 :  * The contents of this file are subject to the Mozilla Public License Version
       6                 :  * 1.1 (the "License"); you may not use this file except in compliance with
       7                 :  * the License. You may obtain a copy of the License at
       8                 :  * http://www.mozilla.org/MPL/
       9                 :  *
      10                 :  * Software distributed under the License is distributed on an "AS IS" basis,
      11                 :  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
      12                 :  * for the specific language governing rights and limitations under the
      13                 :  * License.
      14                 :  *
      15                 :  * The Original Code is mozilla.org code.
      16                 :  *
      17                 :  * The Initial Developer of the Original Code is
      18                 :  * Netscape Communications Corporation.
      19                 :  * Portions created by the Initial Developer are Copyright (C) 2001
      20                 :  * the Initial Developer. All Rights Reserved.
      21                 :  *
      22                 :  * Contributor(s):
      23                 :  *   L. David Baron <dbaron@dbaron.org> (original author)
      24                 :  *   Kai Engert <kaie@netscape.com>
      25                 :  *
      26                 :  * Alternatively, the contents of this file may be used under the terms of
      27                 :  * either the GNU General Public License Version 2 or later (the "GPL"), or
      28                 :  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
      29                 :  * in which case the provisions of the GPL or the LGPL are applicable instead
      30                 :  * of those above. If you wish to allow use of your version of this file only
      31                 :  * under the terms of either the GPL or the LGPL, and not to allow others to
      32                 :  * use your version of this file under the terms of the MPL, indicate your
      33                 :  * decision by deleting the provisions above and replace them with the notice
      34                 :  * and other provisions required by the GPL or the LGPL. If you do not delete
      35                 :  * the provisions above, a recipient may use your version of this file under
      36                 :  * the terms of any one of the MPL, the GPL or the LGPL.
      37                 :  *
      38                 :  * ***** END LICENSE BLOCK ***** */
      39                 : 
      40                 : #include "prlog.h"
      41                 : #include "nsEntropyCollector.h"
      42                 : #include "nsMemory.h"
      43                 : #include "nsAlgorithm.h"
      44                 : 
      45            1404 : nsEntropyCollector::nsEntropyCollector()
      46            1404 : :mBytesCollected(0), mWritePointer(mEntropyCache)
      47                 : {
      48                 :   // We could use the uninitialized memory in mEntropyCache as initial
      49                 :   // random data, but that means (if any entropy is collected before NSS
      50                 :   // initialization and then forwarded) that we'll get warnings from
      51                 :   // tools like valgrind for every later operation that depends on the
      52                 :   // entropy.
      53            1404 :   memset(mEntropyCache, 0, sizeof(mEntropyCache));
      54            1404 : }
      55                 : 
      56            2806 : nsEntropyCollector::~nsEntropyCollector()
      57                 : {
      58            5612 : }
      59                 : 
      60           17883 : NS_IMPL_THREADSAFE_ISUPPORTS2(nsEntropyCollector,
      61                 :                               nsIEntropyCollector,
      62                 :                               nsIBufEntropyCollector)
      63                 : 
      64                 : NS_IMETHODIMP
      65               0 : nsEntropyCollector::RandomUpdate(void *new_entropy, PRInt32 bufLen)
      66                 : {
      67               0 :   if (bufLen > 0) {
      68               0 :     if (mForwardTarget) {
      69               0 :       return mForwardTarget->RandomUpdate(new_entropy, bufLen);
      70                 :     }
      71                 :     else {
      72               0 :       const unsigned char *InputPointer = (const unsigned char *)new_entropy;
      73               0 :       const unsigned char *PastEndPointer = mEntropyCache + entropy_buffer_size;
      74                 : 
      75                 :       // if the input is large, we only take as much as we can store
      76               0 :       PRInt32 bytes_wanted = NS_MIN(bufLen, PRInt32(entropy_buffer_size));
      77                 : 
      78                 :       // remember the number of bytes we will have after storing new_entropy
      79                 :       mBytesCollected = NS_MIN(PRInt32(entropy_buffer_size),
      80               0 :                                mBytesCollected + bytes_wanted);
      81                 : 
      82                 :       // as the above statements limit bytes_wanted to the entropy_buffer_size,
      83                 :       // this loop will iterate at most twice.
      84               0 :       while (bytes_wanted > 0) {
      85                 : 
      86                 :         // how many bytes to end of cyclic buffer?
      87               0 :         const PRInt32 space_to_end = PastEndPointer - mWritePointer;
      88                 : 
      89                 :         // how many bytes can we copy, not reaching the end of the buffer?
      90               0 :         const PRInt32 this_time = NS_MIN(space_to_end, bytes_wanted);
      91                 : 
      92                 :         // copy at most to the end of the cyclic buffer
      93               0 :         for (PRInt32 i = 0; i < this_time; ++i) {
      94                 : 
      95               0 :           unsigned int old = *mWritePointer;
      96                 : 
      97                 :           // combine new and old value already stored in buffer
      98                 :           // this logic comes from PSM 1
      99               0 :           *mWritePointer++ = ((old << 1) | (old >> 7)) ^ *InputPointer++;
     100                 :         }
     101                 : 
     102               0 :         PR_ASSERT(mWritePointer <= PastEndPointer);
     103               0 :         PR_ASSERT(mWritePointer >= mEntropyCache);
     104                 : 
     105                 :         // have we arrived at the end of the buffer?
     106               0 :         if (PastEndPointer == mWritePointer) {
     107                 :           // reset write pointer back to begining of our buffer
     108               0 :           mWritePointer = mEntropyCache;
     109                 :         }
     110                 : 
     111                 :         // subtract the number of bytes we have already copied
     112               0 :         bytes_wanted -= this_time;
     113                 :       }
     114                 :     }
     115                 :   }
     116                 : 
     117               0 :   return NS_OK;
     118                 : }
     119                 : 
     120                 : NS_IMETHODIMP
     121             328 : nsEntropyCollector::ForwardTo(nsIEntropyCollector *aCollector)
     122                 : {
     123             328 :   NS_PRECONDITION(!mForwardTarget, "|ForwardTo| should only be called once.");
     124                 : 
     125             328 :   mForwardTarget = aCollector;
     126             328 :   mForwardTarget->RandomUpdate(mEntropyCache, mBytesCollected);
     127             328 :   mBytesCollected = 0;
     128                 : 
     129             328 :   return NS_OK;
     130                 : }
     131                 : 
     132                 : NS_IMETHODIMP
     133             328 : nsEntropyCollector::DontForward()
     134                 : {
     135             328 :   mForwardTarget = nsnull;
     136             328 :   return NS_OK;
     137                 : }

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