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Fix AlignedBuffer's usage in Encryption Env (facebook#5396)
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Summary:
The usage of `AlignedBuffer` in env_encryption.cc writes and reads to/from the AlignedBuffer's internal buffer directly without going through AlignedBuffer's APIs (like `Append` and `Read`), causing encapsulation to break in some cases. The writes are especially problematic as after the data is written to the buffer (directly using either memmove or memcpy), the size of the buffer is not updated ... causing the AlignedBuffer to lose track of the encapsulated buffer's current size.
Fixed this by updating the buffer size after every write.

Todo for later:
Add an overloaded method to AlignedBuffer to support a memmove in addition to a memcopy. Encryption env does a memmove, and hence I couldn't switch to using `AlignedBuffer.Append()`.
Pull Request resolved: facebook#5396

Test Plan: `make check`

Differential Revision: D15764756

Pulled By: sagar0

fbshipit-source-id: 2e24b52bd3b4b5056c5c1da157f91ddf89370183
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@sagar0 @facebook-github-bot
sagar0 authored and facebook-github-bot committed Jun 19, 2019
1 parent db265f9 commit 5889185
Showing 1 changed file with 49 additions and 38 deletions.
87 changes: 49 additions & 38 deletions env/env_encryption.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -195,23 +195,26 @@ class EncryptedWritableFile : public WritableFileWrapper {
EncryptedWritableFile(WritableFile* f, BlockAccessCipherStream* s, size_t prefixLength)
: WritableFileWrapper(f), file_(f), stream_(s), prefixLength_(prefixLength) { }

Status Append(const Slice& data) override {
Status Append(const Slice& data) override {
AlignedBuffer buf;
Status status;
Slice dataToAppend(data);
Slice dataToAppend(data);
if (data.size() > 0) {
auto offset = file_->GetFileSize(); // size including prefix
// Encrypt in cloned buffer
buf.Alignment(GetRequiredBufferAlignment());
buf.AllocateNewBuffer(data.size());
// TODO (sagar0): Modify AlignedBuffer.Append to allow doing a memmove
// so that the next two lines can be replaced with buf.Append().
memmove(buf.BufferStart(), data.data(), data.size());
status = stream_->Encrypt(offset, buf.BufferStart(), data.size());
buf.Size(data.size());
status = stream_->Encrypt(offset, buf.BufferStart(), buf.CurrentSize());
if (!status.ok()) {
return status;
}
dataToAppend = Slice(buf.BufferStart(), data.size());
dataToAppend = Slice(buf.BufferStart(), buf.CurrentSize());
}
status = file_->Append(dataToAppend);
status = file_->Append(dataToAppend);
if (!status.ok()) {
return status;
}
Expand All @@ -221,18 +224,19 @@ class EncryptedWritableFile : public WritableFileWrapper {
Status PositionedAppend(const Slice& data, uint64_t offset) override {
AlignedBuffer buf;
Status status;
Slice dataToAppend(data);
Slice dataToAppend(data);
offset += prefixLength_;
if (data.size() > 0) {
// Encrypt in cloned buffer
buf.Alignment(GetRequiredBufferAlignment());
buf.AllocateNewBuffer(data.size());
memmove(buf.BufferStart(), data.data(), data.size());
status = stream_->Encrypt(offset, buf.BufferStart(), data.size());
buf.Size(data.size());
status = stream_->Encrypt(offset, buf.BufferStart(), buf.CurrentSize());
if (!status.ok()) {
return status;
}
dataToAppend = Slice(buf.BufferStart(), data.size());
dataToAppend = Slice(buf.BufferStart(), buf.CurrentSize());
}
status = file_->PositionedAppend(dataToAppend, offset);
if (!status.ok()) {
Expand Down Expand Up @@ -325,18 +329,19 @@ class EncryptedRandomRWFile : public RandomRWFile {
Status Write(uint64_t offset, const Slice& data) override {
AlignedBuffer buf;
Status status;
Slice dataToWrite(data);
Slice dataToWrite(data);
offset += prefixLength_;
if (data.size() > 0) {
// Encrypt in cloned buffer
buf.Alignment(GetRequiredBufferAlignment());
buf.AllocateNewBuffer(data.size());
memmove(buf.BufferStart(), data.data(), data.size());
status = stream_->Encrypt(offset, buf.BufferStart(), data.size());
buf.Size(data.size());
status = stream_->Encrypt(offset, buf.BufferStart(), buf.CurrentSize());
if (!status.ok()) {
return status;
}
dataToWrite = Slice(buf.BufferStart(), data.size());
dataToWrite = Slice(buf.BufferStart(), buf.CurrentSize());
}
status = file_->Write(offset, dataToWrite);
return status;
Expand Down Expand Up @@ -393,13 +398,14 @@ class EncryptedEnv : public EnvWrapper {
Slice prefixSlice;
size_t prefixLength = provider_->GetPrefixLength();
if (prefixLength > 0) {
// Read prefix
// Read prefix
prefixBuf.Alignment(underlying->GetRequiredBufferAlignment());
prefixBuf.AllocateNewBuffer(prefixLength);
status = underlying->Read(prefixLength, &prefixSlice, prefixBuf.BufferStart());
if (!status.ok()) {
return status;
}
prefixBuf.Size(prefixLength);
}
// Create cipher stream
std::unique_ptr<BlockAccessCipherStream> stream;
Expand Down Expand Up @@ -430,13 +436,14 @@ class EncryptedEnv : public EnvWrapper {
Slice prefixSlice;
size_t prefixLength = provider_->GetPrefixLength();
if (prefixLength > 0) {
// Read prefix
// Read prefix
prefixBuf.Alignment(underlying->GetRequiredBufferAlignment());
prefixBuf.AllocateNewBuffer(prefixLength);
status = underlying->Read(0, prefixLength, &prefixSlice, prefixBuf.BufferStart());
if (!status.ok()) {
return status;
}
prefixBuf.Size(prefixLength);
}
// Create cipher stream
std::unique_ptr<BlockAccessCipherStream> stream;
Expand Down Expand Up @@ -467,12 +474,13 @@ class EncryptedEnv : public EnvWrapper {
Slice prefixSlice;
size_t prefixLength = provider_->GetPrefixLength();
if (prefixLength > 0) {
// Initialize prefix
// Initialize prefix
prefixBuf.Alignment(underlying->GetRequiredBufferAlignment());
prefixBuf.AllocateNewBuffer(prefixLength);
provider_->CreateNewPrefix(fname, prefixBuf.BufferStart(), prefixLength);
prefixSlice = Slice(prefixBuf.BufferStart(), prefixLength);
// Write prefix
prefixBuf.Size(prefixLength);
prefixSlice = Slice(prefixBuf.BufferStart(), prefixBuf.CurrentSize());
// Write prefix
status = underlying->Append(prefixSlice);
if (!status.ok()) {
return status;
Expand Down Expand Up @@ -513,12 +521,13 @@ class EncryptedEnv : public EnvWrapper {
Slice prefixSlice;
size_t prefixLength = provider_->GetPrefixLength();
if (prefixLength > 0) {
// Initialize prefix
// Initialize prefix
prefixBuf.Alignment(underlying->GetRequiredBufferAlignment());
prefixBuf.AllocateNewBuffer(prefixLength);
provider_->CreateNewPrefix(fname, prefixBuf.BufferStart(), prefixLength);
prefixSlice = Slice(prefixBuf.BufferStart(), prefixLength);
// Write prefix
prefixBuf.Size(prefixLength);
prefixSlice = Slice(prefixBuf.BufferStart(), prefixBuf.CurrentSize());
// Write prefix
status = underlying->Append(prefixSlice);
if (!status.ok()) {
return status;
Expand Down Expand Up @@ -554,12 +563,13 @@ class EncryptedEnv : public EnvWrapper {
Slice prefixSlice;
size_t prefixLength = provider_->GetPrefixLength();
if (prefixLength > 0) {
// Initialize prefix
// Initialize prefix
prefixBuf.Alignment(underlying->GetRequiredBufferAlignment());
prefixBuf.AllocateNewBuffer(prefixLength);
provider_->CreateNewPrefix(fname, prefixBuf.BufferStart(), prefixLength);
prefixSlice = Slice(prefixBuf.BufferStart(), prefixLength);
// Write prefix
prefixBuf.Size(prefixLength);
prefixSlice = Slice(prefixBuf.BufferStart(), prefixBuf.CurrentSize());
// Write prefix
status = underlying->Append(prefixSlice);
if (!status.ok()) {
return status;
Expand Down Expand Up @@ -609,11 +619,13 @@ class EncryptedEnv : public EnvWrapper {
if (!status.ok()) {
return status;
}
prefixBuf.Size(prefixLength);
} else {
// File is new, initialize & write prefix
// File is new, initialize & write prefix
provider_->CreateNewPrefix(fname, prefixBuf.BufferStart(), prefixLength);
prefixSlice = Slice(prefixBuf.BufferStart(), prefixLength);
// Write prefix
prefixBuf.Size(prefixLength);
prefixSlice = Slice(prefixBuf.BufferStart(), prefixBuf.CurrentSize());
// Write prefix
status = underlying->Write(0, prefixSlice);
if (!status.ok()) {
return status;
Expand All @@ -630,7 +642,7 @@ class EncryptedEnv : public EnvWrapper {
return Status::OK();
}

// Store in *result the attributes of the children of the specified directory.
// Store in *result the attributes of the children of the specified directory.
// In case the implementation lists the directory prior to iterating the files
// and files are concurrently deleted, the deleted files will be omitted from
// result.
Expand Down Expand Up @@ -670,8 +682,7 @@ class EncryptedEnv : public EnvWrapper {
EncryptionProvider *provider_;
};


// Returns an Env that encrypts data when stored on disk and decrypts data when
// Returns an Env that encrypts data when stored on disk and decrypts data when
// read from disk.
Env* NewEncryptedEnv(Env* base_env, EncryptionProvider* provider) {
return new EncryptedEnv(base_env, provider);
Expand All @@ -694,14 +705,14 @@ Status BlockAccessCipherStream::Encrypt(uint64_t fileOffset, char *data, size_t
char *block = data;
size_t n = std::min(dataSize, blockSize - blockOffset);
if (n != blockSize) {
// We're not encrypting a full block.
// We're not encrypting a full block.
// Copy data to blockBuffer
if (!blockBuffer.get()) {
// Allocate buffer
blockBuffer = std::unique_ptr<char[]>(new char[blockSize]);
}
block = blockBuffer.get();
// Copy plain data to block buffer
// Copy plain data to block buffer
memmove(block + blockOffset, data, n);
}
auto status = EncryptBlock(blockIndex, block, (char*)scratch.data());
Expand Down Expand Up @@ -741,14 +752,14 @@ Status BlockAccessCipherStream::Decrypt(uint64_t fileOffset, char *data, size_t
char *block = data;
size_t n = std::min(dataSize, blockSize - blockOffset);
if (n != blockSize) {
// We're not decrypting a full block.
// We're not decrypting a full block.
// Copy data to blockBuffer
if (!blockBuffer.get()) {
// Allocate buffer
blockBuffer = std::unique_ptr<char[]>(new char[blockSize]);
}
block = blockBuffer.get();
// Copy encrypted data to block buffer
// Copy encrypted data to block buffer
memmove(block + blockOffset, data, n);
}
auto status = DecryptBlock(blockIndex, block, (char*)scratch.data());
Expand Down Expand Up @@ -807,7 +818,7 @@ Status CTRCipherStream::EncryptBlock(uint64_t blockIndex, char *data, char* scra
memmove(scratch, iv_.data(), blockSize);
EncodeFixed64(scratch, blockIndex + initialCounter_);

// Encrypt nonce+counter
// Encrypt nonce+counter
auto status = cipher_.Encrypt(scratch);
if (!status.ok()) {
return status;
Expand All @@ -823,13 +834,13 @@ Status CTRCipherStream::EncryptBlock(uint64_t blockIndex, char *data, char* scra
// Decrypt a block of data at the given block index.
// Length of data is equal to BlockSize();
Status CTRCipherStream::DecryptBlock(uint64_t blockIndex, char *data, char* scratch) {
// For CTR decryption & encryption are the same
// For CTR decryption & encryption are the same
return EncryptBlock(blockIndex, data, scratch);
}

// GetPrefixLength returns the length of the prefix that is added to every file
// and used for storing encryption options.
// For optimal performance, the prefix length should be a multiple of
// For optimal performance, the prefix length should be a multiple of
// the page size.
size_t CTREncryptionProvider::GetPrefixLength() {
return defaultPrefixLength;
Expand All @@ -844,7 +855,7 @@ static void decodeCTRParameters(const char *prefix, size_t blockSize, uint64_t &
iv = Slice(prefix + blockSize, blockSize);
}

// CreateNewPrefix initialized an allocated block of prefix memory
// CreateNewPrefix initialized an allocated block of prefix memory
// for a new file.
Status CTREncryptionProvider::CreateNewPrefix(const std::string& /*fname*/,
char* prefix,
Expand Down Expand Up @@ -873,7 +884,7 @@ Status CTREncryptionProvider::CreateNewPrefix(const std::string& /*fname*/,
return Status::OK();
}

// PopulateSecretPrefixPart initializes the data into a new prefix block
// PopulateSecretPrefixPart initializes the data into a new prefix block
// in plain text.
// Returns the amount of space (starting from the start of the prefix)
// that has been initialized.
Expand Down Expand Up @@ -908,7 +919,7 @@ Status CTREncryptionProvider::CreateCipherStream(
return status;
}

// Create cipher stream
// Create cipher stream
return CreateCipherStreamFromPrefix(fname, options, initialCounter, iv, prefix, result);
}

Expand Down

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