client/incremental.cpp

/*
 * Copyright (C) 2020 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 "incremental.h"

#include <android-base/file.h>
#include <android-base/stringprintf.h>
#include <openssl/base64.h>

#include "adb_client.h"
#include "adb_io.h"
#include "adb_utils.h"
#include "commandline.h"
#include "sysdeps.h"

#ifndef _WIN32
#include <endian.h>
#else
#define be32toh(x) _byteswap_ulong(x)
#endif

using namespace std::literals;

namespace incremental {

namespace {

static constexpr auto IDSIG = ".idsig"sv;

using android::base::StringPrintf;

using Size = int64_t;

static inline int32_t read_int32(borrowed_fd fd) {
    int32_t result;
    ReadFully(fd, &result, sizeof(result));
    return result;
}

static inline int32_t read_be_int32(borrowed_fd fd) {
    return int32_t(be32toh(read_int32(fd)));
}

static inline void append_bytes_with_size(borrowed_fd fd, std::vector<char>* bytes) {
    int32_t be_size = read_int32(fd);
    int32_t size = int32_t(be32toh(be_size));
    auto old_size = bytes->size();
    bytes->resize(old_size + sizeof(be_size) + size);
    memcpy(bytes->data() + old_size, &be_size, sizeof(be_size));
    ReadFully(fd, bytes->data() + old_size + sizeof(be_size), size);
}

static inline std::pair<std::vector<char>, int32_t> read_id_sig_headers(borrowed_fd fd) {
    std::vector<char> result;
    append_bytes_with_size(fd, &result);  // verityRootHash
    append_bytes_with_size(fd, &result);  // v3Digest
    append_bytes_with_size(fd, &result);  // pkcs7SignatureBlock
    auto tree_size = read_be_int32(fd);   // size of the verity tree
    return {std::move(result), tree_size};
}

static inline Size verity_tree_size_for_file(Size fileSize) {
    constexpr int INCFS_DATA_FILE_BLOCK_SIZE = 4096;
    constexpr int SHA256_DIGEST_SIZE = 32;
    constexpr int digest_size = SHA256_DIGEST_SIZE;
    constexpr int hash_per_block = INCFS_DATA_FILE_BLOCK_SIZE / digest_size;

    Size total_tree_block_count = 0;

    auto block_count = 1 + (fileSize - 1) / INCFS_DATA_FILE_BLOCK_SIZE;
    auto hash_block_count = block_count;
    for (auto i = 0; hash_block_count > 1; i++) {
        hash_block_count = (hash_block_count + hash_per_block - 1) / hash_per_block;
        total_tree_block_count += hash_block_count;
    }
    return total_tree_block_count * INCFS_DATA_FILE_BLOCK_SIZE;
}

// Base64-encode signature bytes. Keeping fd at the position of start of verity tree.
static std::pair<unique_fd, std::string> read_and_encode_signature(Size file_size,
                                                                   std::string signature_file) {
    signature_file += IDSIG;

    struct stat st;
    if (stat(signature_file.c_str(), &st)) {
        fprintf(stderr, "Failed to stat signature file %s. Abort.\n", signature_file.c_str());
        return {};
    }

    unique_fd fd(adb_open(signature_file.c_str(), O_RDONLY | O_CLOEXEC));
    if (fd < 0) {
        fprintf(stderr, "Failed to open signature file: %s. Abort.\n", signature_file.c_str());
        return {};
    }

    auto [signature, tree_size] = read_id_sig_headers(fd);
    if (auto expected = verity_tree_size_for_file(file_size); tree_size != expected) {
        fprintf(stderr,
                "Verity tree size mismatch in signature file: %s [was %lld, expected %lld].\n",
                signature_file.c_str(), (long long)tree_size, (long long)expected);
        return {};
    }

    size_t base64_len = 0;
    if (!EVP_EncodedLength(&base64_len, signature.size())) {
        fprintf(stderr, "Fail to estimate base64 encoded length. Abort.\n");
        return {};
    }
    std::string encoded_signature;
    encoded_signature.resize(base64_len);
    encoded_signature.resize(EVP_EncodeBlock((uint8_t*)encoded_signature.data(),
                                             (const uint8_t*)signature.data(), signature.size()));

    return {std::move(fd), std::move(encoded_signature)};
}

// Send install-incremental to the device along with properly configured file descriptors in
// streaming format. Once connection established, send all fs-verity tree bytes.
static unique_fd start_install(const std::vector<std::string>& files) {
    std::vector<std::string> command_args{"package", "install-incremental"};

    // fd's with positions at the beginning of fs-verity
    std::vector<unique_fd> signature_fds;
    signature_fds.reserve(files.size());
    for (int i = 0, size = files.size(); i < size; ++i) {
        const auto& file = files[i];

        struct stat st;
        if (stat(file.c_str(), &st)) {
            fprintf(stderr, "Failed to stat input file %s. Abort.\n", file.c_str());
            return {};
        }

        auto [signature_fd, signature] = read_and_encode_signature(st.st_size, file);
        if (!signature_fd.ok()) {
            return {};
        }

        auto file_desc =
                StringPrintf("%s:%lld:%s:%s", android::base::Basename(file).c_str(),
                             (long long)st.st_size, std::to_string(i).c_str(), signature.c_str());
        command_args.push_back(std::move(file_desc));

        signature_fds.push_back(std::move(signature_fd));
    }

    std::string error;
    auto connection_fd = unique_fd(send_abb_exec_command(command_args, &error));
    if (connection_fd < 0) {
        fprintf(stderr, "Failed to run: %s, error: %s\n",
                android::base::Join(command_args, " ").c_str(), error.c_str());
        return {};
    }

    // Pushing verity trees for all installation files.
    for (auto&& local_fd : signature_fds) {
        if (!copy_to_file(local_fd.get(), connection_fd.get())) {
            fprintf(stderr, "Failed to stream tree bytes: %s. Abort.\n", strerror(errno));
            return {};
        }
    }

    return connection_fd;
}

}  // namespace

std::optional<Process> install(std::vector<std::string> files) {
    auto connection_fd = start_install(files);
    if (connection_fd < 0) {
        fprintf(stderr, "adb: failed to initiate installation on device.\n");
        return {};
    }

    std::string adb_path = android::base::GetExecutablePath();

    auto osh = adb_get_os_handle(connection_fd.get());
#ifdef _WIN32
    auto fd_param = std::to_string(reinterpret_cast<intptr_t>(osh));
#else /* !_WIN32 a.k.a. Unix */
    auto fd_param = std::to_string(osh);
#endif

    std::vector<std::string> args(std::move(files));
    args.insert(args.begin(), {"inc-server", fd_param});
    auto child = adb_launch_process(adb_path, std::move(args), {connection_fd.get()});
    if (!child) {
        fprintf(stderr, "adb: failed to fork: %s\n", strerror(errno));
        return {};
    }

    auto killOnExit = [](Process* p) { p->kill(); };
    std::unique_ptr<Process, decltype(killOnExit)> serverKiller(&child, killOnExit);
    // TODO: Terminate server process if installation fails.
    serverKiller.release();

    return child;
}

}  // namespace incremental