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/*
* Copyright (C) 2017 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "PrivacyBuffer.h"
#include "io_util.h"
#include <android/util/protobuf.h>
#include <deque>
using namespace android::util;
/**
* Write the field to buf based on the wire type, iterator will point to next field.
* If skip is set to true, no data will be written to buf. Return number of bytes written.
*/
static size_t
write_field_or_skip(EncodedBuffer::iterator* iter, EncodedBuffer* buf, uint8_t wireType, bool skip)
{
EncodedBuffer::Pointer snapshot = iter->rp()->copy();
size_t bytesToWrite = 0;
uint32_t varint = 0;
switch (wireType) {
case WIRE_TYPE_VARINT:
varint = iter->readRawVarint();
if(!skip) return buf->writeRawVarint(varint);
break;
case WIRE_TYPE_FIXED64:
bytesToWrite = 8;
break;
case WIRE_TYPE_LENGTH_DELIMITED:
bytesToWrite = iter->readRawVarint();
if(!skip) buf->writeRawVarint(bytesToWrite);
break;
case WIRE_TYPE_FIXED32:
bytesToWrite = 4;
break;
}
if (skip) {
iter->rp()->move(bytesToWrite);
} else {
for (size_t i=0; i<bytesToWrite; i++) {
*buf->writeBuffer() = iter->next();
buf->wp()->move();
}
}
return skip ? 0 : iter->rp()->pos() - snapshot.pos();
}
/**
* Strip next field based on its private policy and request spec, then stores data in buf.
* Return NO_ERROR if succeeds, otherwise BAD_VALUE is returned to indicate bad data in FdBuffer.
*
* The iterator must point to the head of a protobuf formatted field for successful operation.
* After exit with NO_ERROR, iterator points to the next protobuf field's head.
*/
static status_t
stripField(EncodedBuffer::iterator* iter, EncodedBuffer* buf, const Privacy* parentPolicy, const PrivacySpec& spec)
{
if (!iter->hasNext() || parentPolicy == NULL) return BAD_VALUE;
uint32_t varint = iter->readRawVarint();
uint8_t wireType = read_wire_type(varint);
uint32_t fieldId = read_field_id(varint);
const Privacy* policy = parentPolicy->lookup(fieldId);
if (policy == NULL || !policy->IsMessageType() || !policy->HasChildren()) {
bool skip = !spec.CheckPremission(policy);
size_t amt = buf->size();
if (!skip) amt += buf->writeHeader(fieldId, wireType);
amt += write_field_or_skip(iter, buf, wireType, skip); // point to head of next field
return buf->size() != amt ? BAD_VALUE : NO_ERROR;
}
// current field is message type and its sub-fields have extra privacy policies
deque<EncodedBuffer*> q;
uint32_t msgSize = iter->readRawVarint();
size_t finalSize = 0;
EncodedBuffer::Pointer start = iter->rp()->copy();
while (iter->rp()->pos() - start.pos() != msgSize) {
EncodedBuffer* v = new EncodedBuffer();
status_t err = stripField(iter, v, policy, spec);
if (err != NO_ERROR) return err;
if (v->size() == 0) continue;
q.push_back(v);
finalSize += v->size();
}
buf->writeHeader(fieldId, wireType);
buf->writeRawVarint(finalSize);
while (!q.empty()) {
EncodedBuffer* subField = q.front();
EncodedBuffer::iterator it = subField->begin();
while (it.hasNext()) {
*buf->writeBuffer() = it.next();
buf->wp()->move();
}
q.pop_front();
delete subField;
}
return NO_ERROR;
}
// ================================================================================
PrivacyBuffer::PrivacyBuffer(const Privacy* policy, EncodedBuffer::iterator& data)
:mPolicy(policy),
mData(data),
mBuffer(0),
mSize(0)
{
}
PrivacyBuffer::~PrivacyBuffer()
{
}
status_t
PrivacyBuffer::strip(const PrivacySpec& spec)
{
// optimization when no strip happens
if (mPolicy == NULL || !mPolicy->HasChildren() || spec.RequireAll()) {
if (spec.CheckPremission(mPolicy)) mSize = mData.size();
return NO_ERROR;
}
while (mData.hasNext()) {
status_t err = stripField(&mData, &mBuffer, mPolicy, spec);
if (err != NO_ERROR) return err;
}
if (mData.bytesRead() != mData.size()) return BAD_VALUE;
mSize = mBuffer.size();
mData.rp()->rewind(); // rewind the read pointer back to beginning after the strip.
return NO_ERROR;
}
void
PrivacyBuffer::clear()
{
mSize = 0;
mBuffer.wp()->rewind();
}
size_t
PrivacyBuffer::size() const { return mSize; }
status_t
PrivacyBuffer::flush(int fd)
{
status_t err = NO_ERROR;
EncodedBuffer::iterator iter = size() == mData.size() ? mData : mBuffer.begin();
while (iter.readBuffer() != NULL) {
err = write_all(fd, iter.readBuffer(), iter.currentToRead());
iter.rp()->move(iter.currentToRead());
if (err != NO_ERROR) return err;
}
return NO_ERROR;
}