mirror of
https://github.com/classilla/tenfourfox.git
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104 lines
3.3 KiB
C++
104 lines
3.3 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "mozilla/Logging.h"
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#include "nsEntropyCollector.h"
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#include "nsAlgorithm.h"
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#include <algorithm>
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nsEntropyCollector::nsEntropyCollector()
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:mBytesCollected(0), mWritePointer(mEntropyCache)
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{
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// We could use the uninitialized memory in mEntropyCache as initial
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// random data, but that means (if any entropy is collected before NSS
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// initialization and then forwarded) that we'll get warnings from
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// tools like valgrind for every later operation that depends on the
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// entropy.
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memset(mEntropyCache, 0, sizeof(mEntropyCache));
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}
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nsEntropyCollector::~nsEntropyCollector()
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{
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}
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NS_IMPL_ISUPPORTS(nsEntropyCollector,
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nsIEntropyCollector,
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nsIBufEntropyCollector)
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NS_IMETHODIMP
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nsEntropyCollector::RandomUpdate(void *new_entropy, int32_t bufLen)
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{
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if (bufLen > 0) {
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if (mForwardTarget) {
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return mForwardTarget->RandomUpdate(new_entropy, bufLen);
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}
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else {
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const unsigned char *InputPointer = (const unsigned char *)new_entropy;
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const unsigned char *PastEndPointer = mEntropyCache + entropy_buffer_size;
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// if the input is large, we only take as much as we can store
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int32_t bytes_wanted = std::min(bufLen, int32_t(entropy_buffer_size));
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// remember the number of bytes we will have after storing new_entropy
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mBytesCollected = std::min(int32_t(entropy_buffer_size),
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mBytesCollected + bytes_wanted);
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// as the above statements limit bytes_wanted to the entropy_buffer_size,
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// this loop will iterate at most twice.
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while (bytes_wanted > 0) {
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// how many bytes to end of cyclic buffer?
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const int32_t space_to_end = PastEndPointer - mWritePointer;
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// how many bytes can we copy, not reaching the end of the buffer?
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const int32_t this_time = std::min(space_to_end, bytes_wanted);
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// copy at most to the end of the cyclic buffer
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for (int32_t i = 0; i < this_time; ++i) {
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unsigned int old = *mWritePointer;
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// combine new and old value already stored in buffer
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// this logic comes from PSM 1
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*mWritePointer++ = ((old << 1) | (old >> 7)) ^ *InputPointer++;
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}
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PR_ASSERT(mWritePointer <= PastEndPointer);
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PR_ASSERT(mWritePointer >= mEntropyCache);
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// have we arrived at the end of the buffer?
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if (PastEndPointer == mWritePointer) {
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// reset write pointer back to begining of our buffer
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mWritePointer = mEntropyCache;
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}
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// subtract the number of bytes we have already copied
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bytes_wanted -= this_time;
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}
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}
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}
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return NS_OK;
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}
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NS_IMETHODIMP
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nsEntropyCollector::ForwardTo(nsIEntropyCollector *aCollector)
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{
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NS_PRECONDITION(!mForwardTarget, "|ForwardTo| should only be called once.");
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mForwardTarget = aCollector;
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mForwardTarget->RandomUpdate(mEntropyCache, mBytesCollected);
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mBytesCollected = 0;
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return NS_OK;
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}
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NS_IMETHODIMP
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nsEntropyCollector::DontForward()
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{
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mForwardTarget = nullptr;
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return NS_OK;
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}
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