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comparison: security/manager/boot/src/nsEntropyCollector.cpp
security/manager/boot/src/nsEntropyCollector.cpp
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| 1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ | |
| 2 /* This Source Code Form is subject to the terms of the Mozilla Public | |
| 3 * License, v. 2.0. If a copy of the MPL was not distributed with this | |
| 4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ | |
| 5 | |
| 6 #include "prlog.h" | |
| 7 #include "nsEntropyCollector.h" | |
| 8 #include "nsAlgorithm.h" | |
| 9 #include <algorithm> | |
| 10 | |
| 11 nsEntropyCollector::nsEntropyCollector() | |
| 12 :mBytesCollected(0), mWritePointer(mEntropyCache) | |
| 13 { | |
| 14 // We could use the uninitialized memory in mEntropyCache as initial | |
| 15 // random data, but that means (if any entropy is collected before NSS | |
| 16 // initialization and then forwarded) that we'll get warnings from | |
| 17 // tools like valgrind for every later operation that depends on the | |
| 18 // entropy. | |
| 19 memset(mEntropyCache, 0, sizeof(mEntropyCache)); | |
| 20 } | |
| 21 | |
| 22 nsEntropyCollector::~nsEntropyCollector() | |
| 23 { | |
| 24 } | |
| 25 | |
| 26 NS_IMPL_ISUPPORTS(nsEntropyCollector, | |
| 27 nsIEntropyCollector, | |
| 28 nsIBufEntropyCollector) | |
| 29 | |
| 30 NS_IMETHODIMP | |
| 31 nsEntropyCollector::RandomUpdate(void *new_entropy, int32_t bufLen) | |
| 32 { | |
| 33 if (bufLen > 0) { | |
| 34 if (mForwardTarget) { | |
| 35 return mForwardTarget->RandomUpdate(new_entropy, bufLen); | |
| 36 } | |
| 37 else { | |
| 38 const unsigned char *InputPointer = (const unsigned char *)new_entropy; | |
| 39 const unsigned char *PastEndPointer = mEntropyCache + entropy_buffer_size; | |
| 40 | |
| 41 // if the input is large, we only take as much as we can store | |
| 42 int32_t bytes_wanted = std::min(bufLen, int32_t(entropy_buffer_size)); | |
| 43 | |
| 44 // remember the number of bytes we will have after storing new_entropy | |
| 45 mBytesCollected = std::min(int32_t(entropy_buffer_size), | |
| 46 mBytesCollected + bytes_wanted); | |
| 47 | |
| 48 // as the above statements limit bytes_wanted to the entropy_buffer_size, | |
| 49 // this loop will iterate at most twice. | |
| 50 while (bytes_wanted > 0) { | |
| 51 | |
| 52 // how many bytes to end of cyclic buffer? | |
| 53 const int32_t space_to_end = PastEndPointer - mWritePointer; | |
| 54 | |
| 55 // how many bytes can we copy, not reaching the end of the buffer? | |
| 56 const int32_t this_time = std::min(space_to_end, bytes_wanted); | |
| 57 | |
| 58 // copy at most to the end of the cyclic buffer | |
| 59 for (int32_t i = 0; i < this_time; ++i) { | |
| 60 | |
| 61 unsigned int old = *mWritePointer; | |
| 62 | |
| 63 // combine new and old value already stored in buffer | |
| 64 // this logic comes from PSM 1 | |
| 65 *mWritePointer++ = ((old << 1) | (old >> 7)) ^ *InputPointer++; | |
| 66 } | |
| 67 | |
| 68 PR_ASSERT(mWritePointer <= PastEndPointer); | |
| 69 PR_ASSERT(mWritePointer >= mEntropyCache); | |
| 70 | |
| 71 // have we arrived at the end of the buffer? | |
| 72 if (PastEndPointer == mWritePointer) { | |
| 73 // reset write pointer back to begining of our buffer | |
| 74 mWritePointer = mEntropyCache; | |
| 75 } | |
| 76 | |
| 77 // subtract the number of bytes we have already copied | |
| 78 bytes_wanted -= this_time; | |
| 79 } | |
| 80 } | |
| 81 } | |
| 82 | |
| 83 return NS_OK; | |
| 84 } | |
| 85 | |
| 86 NS_IMETHODIMP | |
| 87 nsEntropyCollector::ForwardTo(nsIEntropyCollector *aCollector) | |
| 88 { | |
| 89 NS_PRECONDITION(!mForwardTarget, "|ForwardTo| should only be called once."); | |
| 90 | |
| 91 mForwardTarget = aCollector; | |
| 92 mForwardTarget->RandomUpdate(mEntropyCache, mBytesCollected); | |
| 93 mBytesCollected = 0; | |
| 94 | |
| 95 return NS_OK; | |
| 96 } | |
| 97 | |
| 98 NS_IMETHODIMP | |
| 99 nsEntropyCollector::DontForward() | |
| 100 { | |
| 101 mForwardTarget = nullptr; | |
| 102 return NS_OK; | |
| 103 } |
