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Commit 290b0ed4 authored by Daniel Rosenberg's avatar Daniel Rosenberg
Browse files

libsnapshot: Fix footer values and verification 

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
parent 46ef7595

fs_mgr/libsnapshot/cow_reader.cpp

+15 −1
Original line number Diff line number Diff line
@@ -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";

fs_mgr/libsnapshot/cow_writer.cpp

+3 −1
Original line number Diff line number Diff line
@@ -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)) {