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Merge "Simplify IV Incrementation"

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This commit is contained in:
John Bruce
2016-11-30 23:39:41 +00:00
committed by Android (Google) Code Review
parent 6d000b5295 3847adb78e
commit e990c82466
2 changed files with 10 additions and 22 deletions
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3
libwvdrmengine/mediacrypto/include/WVCryptoPlugin.h
View File

@@ -46,8 +46,7 @@ class WVCryptoPlugin : public android::CryptoPlugin {
wvcdm::CdmSessionId configureTestMode(const void* data, size_t size);
static wvcdm::CdmResponseType countEncryptedBlocksInPatternedRange(
size_t range, size_t startingOffset, const Pattern& pattern,
uint64_t* result);
size_t range, const Pattern& pattern, uint64_t* result);
static void incrementIV(uint64_t increaseBy, std::vector<uint8_t>* ivPtr);
};

29
libwvdrmengine/mediacrypto/src/WVCryptoPlugin.cpp
View File

@@ -292,8 +292,7 @@ ssize_t WVCryptoPlugin::decrypt(bool secure, const uint8_t key[KEY_ID_SIZE],
kAESBlockSize;
} else {
res = countEncryptedBlocksInPatternedRange(
subSample.mNumBytesOfEncryptedData, blockOffset, pattern,
&increment);
subSample.mNumBytesOfEncryptedData, pattern, &increment);
if (!isCdmResponseTypeSuccess(res)) {
// Swallow the specifics of the error to obscure decrypt internals.
return kErrorCDMGeneric;
@@ -348,32 +347,22 @@ ssize_t WVCryptoPlugin::decrypt(bool secure, const uint8_t key[KEY_ID_SIZE],
}
CdmResponseType WVCryptoPlugin::countEncryptedBlocksInPatternedRange(
size_t range, size_t startingOffset, const Pattern& pattern,
uint64_t* result) {
uint64_t blocksPassed = 0;
size_t bytesRemaining = range;
size_t patternPosition = 0;
size_t patternLength = pattern.mEncryptBlocks + pattern.mSkipBlocks;
if (result == NULL || startingOffset >= kAESBlockSize) {
size_t range, const Pattern& pattern, uint64_t* result) {
if (result == NULL || range % kAESBlockSize != 0) {
return wvcdm::UNKNOWN_ERROR;
}
// We may already be partway into a block, so reduce the number of bytes
// that must be passed to complete a block if so.
size_t bytesNeededToCompleteABlock = kAESBlockSize - startingOffset;
while (bytesRemaining >= bytesNeededToCompleteABlock) {
bytesRemaining -= bytesNeededToCompleteABlock;
const size_t patternLength = pattern.mEncryptBlocks + pattern.mSkipBlocks;
uint64_t encryptedBlocksPassed = 0;
size_t patternPosition = 0;
for (size_t remaining = range / kAESBlockSize; remaining > 0; --remaining) {
if (patternPosition < pattern.mEncryptBlocks) {
++blocksPassed;
++encryptedBlocksPassed;
}
patternPosition = (patternPosition + 1) % patternLength;
// After the first block, we only concern ourselves with complete blocks.
bytesNeededToCompleteABlock = kAESBlockSize;
}
*result = blocksPassed;
*result = encryptedBlocksPassed;
return wvcdm::NO_ERROR;
}