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libsnapshot: Fix footer values and verification

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A few values in the footer were being set inconsistently. We weren't
verifying them, so it didn't matter. This adds verification and sets
them properly.

Change-Id: I669a03a6e1e87ace31775aba5b67dde9b6e5ecf5
Bug: 168829493
Test: cow_api_test
This commit is contained in:
Daniel Rosenberg 2020-11-02 23:53:37 -08:00
parent 46ef7595d0
commit 290b0ed4b3
2 changed files with 18 additions and 2 deletions
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16
fs_mgr/libsnapshot/cow_reader.cpp
View file

@ -154,7 +154,8 @@ bool CowReader::ParseOps() {
}
} else if (current_op.type == kCowFooterOp) {
memcpy(&footer_.op, &current_op, sizeof(footer_.op));
// we don't consider this an operation for the checksum
current_op_num--;
if (android::base::ReadFully(fd_, &footer_.data, sizeof(footer_.data))) {
has_footer_ = true;
if (next_last_label) {
@ -170,6 +171,19 @@ bool CowReader::ParseOps() {
memset(csum, 0, sizeof(uint8_t) * 32);
if (has_footer_) {
if (ops_buffer->size() != footer_.op.num_ops) {
LOG(ERROR) << "num ops does not match";
return false;
}
if (ops_buffer->size() * sizeof(CowOperation) != footer_.op.ops_size) {
LOG(ERROR) << "ops size does not match ";
return false;
}
SHA256(&footer_.op, sizeof(footer_.op), footer_.data.footer_checksum);
if (memcmp(csum, footer_.data.ops_checksum, sizeof(csum)) != 0) {
LOG(ERROR) << "ops checksum does not match";
return false;
}
SHA256(ops_buffer.get()->data(), footer_.op.ops_size, csum);
if (memcmp(csum, footer_.data.ops_checksum, sizeof(csum)) != 0) {
LOG(ERROR) << "ops checksum does not match";

4
fs_mgr/libsnapshot/cow_writer.cpp
View file

@ -185,6 +185,7 @@ bool CowWriter::OpenForAppend() {
// Reset this, since we're going to reimport all operations.
footer_.op.num_ops = 0;
next_op_pos_ = sizeof(header_);
ops_.resize(0);
auto iter = reader->GetOpIter();
while (!iter->Done()) {
@ -233,6 +234,7 @@ bool CowWriter::OpenForAppend(uint64_t label) {
// Reset this, since we're going to reimport all operations.
footer_.op.num_ops = 0;
next_op_pos_ = sizeof(header_);
ops_.resize(0);
auto iter = reader->GetOpIter();
while (!iter->Done()) {
@ -384,7 +386,7 @@ static void SHA256(const void*, size_t, uint8_t[]) {
}
bool CowWriter::Finalize() {
footer_.op.ops_size = ops_.size() + sizeof(footer_.op);
footer_.op.ops_size = ops_.size();
uint64_t pos;
if (!GetDataPos(&pos)) {