LCOV - app.info - security/manager/boot/src/nsEntropyCollector.cpp

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: | 2012-04-21 | 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            1365 : nsEntropyCollector::nsEntropyCollector()
          46            1365 : :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            1365 :   memset(mEntropyCache, 0, sizeof(mEntropyCache));
          54            1365 : }
          55                 :
          56            2728 : nsEntropyCollector::~nsEntropyCollector()
          57                 : {
          58            5456 : }
          59                 :
          60           17516 : 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             327 : nsEntropyCollector::ForwardTo(nsIEntropyCollector *aCollector)
         122                 : {
         123             327 :   NS_PRECONDITION(!mForwardTarget, "|ForwardTo| should only be called once.");
         124                 :
         125             327 :   mForwardTarget = aCollector;
         126             327 :   mForwardTarget->RandomUpdate(mEntropyCache, mBytesCollected);
         127             327 :   mBytesCollected = 0;
         128                 :
         129             327 :   return NS_OK;
         130                 : }
         131                 :
         132                 : NS_IMETHODIMP
         133             327 : nsEntropyCollector::DontForward()
         134                 : {
         135             327 :   mForwardTarget = nsnull;
         136             327 :   return NS_OK;
         137                 : }

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