payload_signer.cc

// Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "update_engine/payload_signer.h"

#include <base/logging.h>
#include <base/strings/string_split.h>
#include <base/strings/string_util.h>
#include <openssl/pem.h>

#include "update_engine/delta_performer.h"
#include "update_engine/omaha_hash_calculator.h"
#include "update_engine/payload_generator/delta_diff_generator.h"
#include "update_engine/subprocess.h"
#include "update_engine/update_metadata.pb.h"
#include "update_engine/utils.h"

using std::string;
using std::vector;

namespace chromeos_update_engine {

const uint32_t kSignatureMessageOriginalVersion = 1;
const uint32_t kSignatureMessageCurrentVersion = 1;

namespace {

// The following is a standard PKCS1-v1_5 padding for SHA256 signatures, as
// defined in RFC3447. It is prepended to the actual signature (32 bytes) to
// form a sequence of 256 bytes (2048 bits) that is amenable to RSA signing. The
// padded hash will look as follows:
//
//    0x00 0x01 0xff ... 0xff 0x00  ASN1HEADER  SHA256HASH
//   |--------------205-----------||----19----||----32----|
//
// where ASN1HEADER is the ASN.1 description of the signed data. The complete 51
// bytes of actual data (i.e. the ASN.1 header complete with the hash) are
// packed as follows:
//
//  SEQUENCE(2+49) {
//   SEQUENCE(2+13) {
//    OBJECT(2+9) id-sha256
//    NULL(2+0)
//   }
//   OCTET STRING(2+32) <actual signature bytes...>
//  }
const unsigned char kRSA2048SHA256Padding[] = {
  // PKCS1-v1_5 padding
  0x00, 0x01, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  0xff, 0xff, 0xff, 0xff, 0x00,
  // ASN.1 header
  0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
  0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05,
  0x00, 0x04, 0x20,
};

// Given raw |signatures|, packs them into a protobuf and serializes it into a
// binary blob. Returns true on success, false otherwise.
bool ConvertSignatureToProtobufBlob(const vector<vector<char> >& signatures,
                                    vector<char>* out_signature_blob) {
  // Pack it into a protobuf
  Signatures out_message;
  uint32_t version = kSignatureMessageOriginalVersion;
  LOG_IF(WARNING, kSignatureMessageCurrentVersion -
         kSignatureMessageOriginalVersion + 1 < signatures.size())
      << "You may want to support clients in the range ["
      << kSignatureMessageOriginalVersion << ", "
      << kSignatureMessageCurrentVersion << "] inclusive, but you only "
      << "provided " << signatures.size() << " signatures.";
  for (vector<vector<char> >::const_iterator it = signatures.begin(),
           e = signatures.end(); it != e; ++it) {
    const vector<char>& signature = *it;
    Signatures_Signature* sig_message = out_message.add_signatures();
    sig_message->set_version(version++);
    sig_message->set_data(signature.data(), signature.size());
  }

  // Serialize protobuf
  string serialized;
  TEST_AND_RETURN_FALSE(out_message.AppendToString(&serialized));
  out_signature_blob->insert(out_signature_blob->end(),
                             serialized.begin(),
                             serialized.end());
  LOG(INFO) << "Signature blob size: " << out_signature_blob->size();
  return true;
}

// Given an unsigned payload under |payload_path| and the |signature_blob_size|
// generates an updated payload that includes a dummy signature op in its
// manifest. It populates |out_metadata_size| with the size of the final
// manifest after adding the dummy signature operation, and
// |out_signatures_offset| with the expected offset for the new blob. Returns
// true on success, false otherwise.
bool AddSignatureOpToPayload(const string& payload_path,
                             uint64_t signature_blob_size,
                             vector<char>* out_payload,
                             uint64_t* out_metadata_size,
                             uint64_t* out_signatures_offset) {
  const int kProtobufOffset = 20;
  const int kProtobufSizeOffset = 12;

  // Loads the payload.
  vector<char> payload;
  DeltaArchiveManifest manifest;
  uint64_t metadata_size;
  TEST_AND_RETURN_FALSE(PayloadSigner::LoadPayload(
      payload_path, &payload, &manifest, &metadata_size));

  // Is there already a signature op in place?
  if (manifest.has_signatures_size()) {

    // The signature op is tied to the size of the signature blob, but not it's
    // contents. We don't allow the manifest to change if there is already an op
    // present, because that might invalidate previously generated
    // hashes/signatures.
    if (manifest.signatures_size() != signature_blob_size) {
      LOG(ERROR) << "Attempt to insert different signature sized blob. "
                 << "(current:" << manifest.signatures_size()
                 << "new:" << signature_blob_size << ")";
      return false;
    }

    LOG(INFO) << "Matching signature sizes already present.";
  } else {
    // Updates the manifest to include the signature operation.
    DeltaDiffGenerator::AddSignatureOp(payload.size() - metadata_size,
                                       signature_blob_size,
                                       &manifest);

    // Updates the payload to include the new manifest.
    string serialized_manifest;
    TEST_AND_RETURN_FALSE(manifest.AppendToString(&serialized_manifest));
    LOG(INFO) << "Updated protobuf size: " << serialized_manifest.size();
    payload.erase(payload.begin() + kProtobufOffset,
                  payload.begin() + metadata_size);
    payload.insert(payload.begin() + kProtobufOffset,
                   serialized_manifest.begin(),
                   serialized_manifest.end());

    // Updates the protobuf size.
    uint64_t size_be = htobe64(serialized_manifest.size());
    memcpy(&payload[kProtobufSizeOffset], &size_be, sizeof(size_be));
    metadata_size = serialized_manifest.size() + kProtobufOffset;

    LOG(INFO) << "Updated payload size: " << payload.size();
    LOG(INFO) << "Updated metadata size: " << metadata_size;
  }

  out_payload->swap(payload);
  *out_metadata_size = metadata_size;
  *out_signatures_offset = metadata_size + manifest.signatures_offset();
  LOG(INFO) << "Signature Blob Offset: " << *out_signatures_offset;
  return true;
}
}  // namespace {}

bool PayloadSigner::LoadPayload(const string& payload_path,
                 vector<char>* out_payload,
                 DeltaArchiveManifest* out_manifest,
                 uint64_t* out_metadata_size) {
  vector<char> payload;
  // Loads the payload and parses the manifest.
  TEST_AND_RETURN_FALSE(utils::ReadFile(payload_path, &payload));
  LOG(INFO) << "Payload size: " << payload.size();
  ErrorCode error = kErrorCodeSuccess;
  InstallPlan install_plan;
  DeltaPerformer delta_performer(NULL, NULL, &install_plan);
  TEST_AND_RETURN_FALSE(
      delta_performer.ParsePayloadMetadata(payload, &error) ==
      DeltaPerformer::kMetadataParseSuccess);
  TEST_AND_RETURN_FALSE(delta_performer.GetManifest(out_manifest));
  *out_metadata_size = delta_performer.GetMetadataSize();
  LOG(INFO) << "Metadata size: " << *out_metadata_size;
  out_payload->swap(payload);
  return true;
}

bool PayloadSigner::SignHash(const vector<char>& hash,
                             const string& private_key_path,
                             vector<char>* out_signature) {
  LOG(INFO) << "Signing hash with private key: " << private_key_path;
  string sig_path;
  TEST_AND_RETURN_FALSE(
      utils::MakeTempFile("signature.XXXXXX", &sig_path, NULL));
  ScopedPathUnlinker sig_path_unlinker(sig_path);

  string hash_path;
  TEST_AND_RETURN_FALSE(
      utils::MakeTempFile("hash.XXXXXX", &hash_path, NULL));
  ScopedPathUnlinker hash_path_unlinker(hash_path);
  // We expect unpadded SHA256 hash coming in
  TEST_AND_RETURN_FALSE(hash.size() == 32);
  vector<char> padded_hash(hash);
  PadRSA2048SHA256Hash(&padded_hash);
  TEST_AND_RETURN_FALSE(utils::WriteFile(hash_path.c_str(),
                                         padded_hash.data(),
                                         padded_hash.size()));

  // This runs on the server, so it's okay to cop out and call openssl
  // executable rather than properly use the library
  vector<string> cmd;
  base::SplitString("openssl rsautl -raw -sign -inkey x -in x -out x",
                    ' ',
                    &cmd);
  cmd[cmd.size() - 5] = private_key_path;
  cmd[cmd.size() - 3] = hash_path;
  cmd[cmd.size() - 1] = sig_path;

  int return_code = 0;
  TEST_AND_RETURN_FALSE(Subprocess::SynchronousExec(cmd, &return_code, NULL));
  TEST_AND_RETURN_FALSE(return_code == 0);

  vector<char> signature;
  TEST_AND_RETURN_FALSE(utils::ReadFile(sig_path, &signature));
  out_signature->swap(signature);
  return true;
}

bool PayloadSigner::SignPayload(const string& unsigned_payload_path,
                                const vector<string>& private_key_paths,
                                vector<char>* out_signature_blob) {
  vector<char> hash_data;
  TEST_AND_RETURN_FALSE(OmahaHashCalculator::RawHashOfFile(
      unsigned_payload_path, -1, &hash_data) ==
                        utils::FileSize(unsigned_payload_path));

  vector<vector<char> > signatures;
  for (vector<string>::const_iterator it = private_key_paths.begin(),
           e = private_key_paths.end(); it != e; ++it) {
    vector<char> signature;
    TEST_AND_RETURN_FALSE(SignHash(hash_data, *it, &signature));
    signatures.push_back(signature);
  }
  TEST_AND_RETURN_FALSE(ConvertSignatureToProtobufBlob(signatures,
                                                       out_signature_blob));
  return true;
}

bool PayloadSigner::SignatureBlobLength(const vector<string>& private_key_paths,
                                        uint64_t* out_length) {
  DCHECK(out_length);

  string x_path;
  TEST_AND_RETURN_FALSE(
      utils::MakeTempFile("signed_data.XXXXXX", &x_path, NULL));
  ScopedPathUnlinker x_path_unlinker(x_path);
  TEST_AND_RETURN_FALSE(utils::WriteFile(x_path.c_str(), "x", 1));

  vector<char> sig_blob;
  TEST_AND_RETURN_FALSE(PayloadSigner::SignPayload(x_path,
                                                   private_key_paths,
                                                   &sig_blob));
  *out_length = sig_blob.size();
  return true;
}

bool PayloadSigner::VerifySignature(const std::vector<char>& signature_blob,
                                    const std::string& public_key_path,
                                    std::vector<char>* out_hash_data) {
  return VerifySignatureBlob(signature_blob, public_key_path,
                                kSignatureMessageCurrentVersion, out_hash_data);
}

bool PayloadSigner::VerifySignatureBlob(
    const std::vector<char>& signature_blob,
    const std::string& public_key_path,
    uint32_t client_version,
    std::vector<char>* out_hash_data) {
  TEST_AND_RETURN_FALSE(!public_key_path.empty());

  Signatures signatures;
  LOG(INFO) << "signature size = " <<  signature_blob.size();
  TEST_AND_RETURN_FALSE(signatures.ParseFromArray(&signature_blob[0],
                                                  signature_blob.size()));

  // Finds a signature that matches the current version.
  int sig_index = 0;
  for (; sig_index < signatures.signatures_size(); sig_index++) {
    const Signatures_Signature& signature = signatures.signatures(sig_index);
    if (signature.has_version() &&
        signature.version() == client_version) {
      break;
    }
  }
  TEST_AND_RETURN_FALSE(sig_index < signatures.signatures_size());

  const Signatures_Signature& signature = signatures.signatures(sig_index);
  vector<char> sig_data(signature.data().begin(), signature.data().end());

  return GetRawHashFromSignature(sig_data, public_key_path, out_hash_data);
}


bool PayloadSigner::GetRawHashFromSignature(
    const std::vector<char>& sig_data,
    const std::string& public_key_path,
    std::vector<char>* out_hash_data) {
  TEST_AND_RETURN_FALSE(!public_key_path.empty());

  // The code below executes the equivalent of:
  //
  // openssl rsautl -verify -pubin -inkey |public_key_path|
  //   -in |sig_data| -out |out_hash_data|

  // Loads the public key.
  FILE* fpubkey = fopen(public_key_path.c_str(), "rb");
  if (!fpubkey) {
    LOG(ERROR) << "Unable to open public key file: " << public_key_path;
    return false;
  }

  char dummy_password[] = { ' ', 0 };  // Ensure no password is read from stdin.
  RSA* rsa = PEM_read_RSA_PUBKEY(fpubkey, NULL, NULL, dummy_password);
  fclose(fpubkey);
  TEST_AND_RETURN_FALSE(rsa != NULL);
  unsigned int keysize = RSA_size(rsa);
  if (sig_data.size() > 2 * keysize) {
    LOG(ERROR) << "Signature size is too big for public key size.";
    RSA_free(rsa);
    return false;
  }

  // Decrypts the signature.
  vector<char> hash_data(keysize);
  int decrypt_size = RSA_public_decrypt(
      sig_data.size(),
      reinterpret_cast<const unsigned char*>(sig_data.data()),
      reinterpret_cast<unsigned char*>(hash_data.data()),
      rsa,
      RSA_NO_PADDING);
  RSA_free(rsa);
  TEST_AND_RETURN_FALSE(decrypt_size > 0 &&
                        decrypt_size <= static_cast<int>(hash_data.size()));
  hash_data.resize(decrypt_size);
  out_hash_data->swap(hash_data);
  return true;
}

bool PayloadSigner::VerifySignedPayload(const std::string& payload_path,
                                        const std::string& public_key_path,
                                        uint32_t client_key_check_version) {
  vector<char> payload;
  DeltaArchiveManifest manifest;
  uint64_t metadata_size;
  TEST_AND_RETURN_FALSE(LoadPayload(
      payload_path, &payload, &manifest, &metadata_size));
  TEST_AND_RETURN_FALSE(manifest.has_signatures_offset() &&
                        manifest.has_signatures_size());
  CHECK_EQ(payload.size(),
           metadata_size + manifest.signatures_offset() +
           manifest.signatures_size());
  vector<char> signature_blob(
      payload.begin() + metadata_size + manifest.signatures_offset(),
      payload.end());
  vector<char> signed_hash;
  TEST_AND_RETURN_FALSE(VerifySignatureBlob(
      signature_blob, public_key_path, client_key_check_version, &signed_hash));
  TEST_AND_RETURN_FALSE(!signed_hash.empty());
  vector<char> hash;
  TEST_AND_RETURN_FALSE(OmahaHashCalculator::RawHashOfBytes(
      payload.data(), metadata_size + manifest.signatures_offset(), &hash));
  PadRSA2048SHA256Hash(&hash);
  TEST_AND_RETURN_FALSE(hash == signed_hash);
  return true;
}

bool PayloadSigner::PrepPayloadForHashing(
        const string& payload_path,
        const vector<int>& signature_sizes,
        vector<char>* payload_out,
        uint64_t* metadata_size_out,
        uint64_t* signatures_offset_out) {
  // TODO(petkov): Reduce memory usage -- the payload is manipulated in memory.

  // Loads the payload and adds the signature op to it.
  vector<vector<char> > signatures;
  for (vector<int>::const_iterator it = signature_sizes.begin(),
           e = signature_sizes.end(); it != e; ++it) {
    vector<char> signature(*it, 0);
    signatures.push_back(signature);
  }
  vector<char> signature_blob;
  TEST_AND_RETURN_FALSE(ConvertSignatureToProtobufBlob(signatures,
                                                       &signature_blob));
  TEST_AND_RETURN_FALSE(AddSignatureOpToPayload(payload_path,
                                                signature_blob.size(),
                                                payload_out,
                                                metadata_size_out,
                                                signatures_offset_out));

  return true;
}

bool PayloadSigner::HashPayloadForSigning(const string& payload_path,
                                          const vector<int>& signature_sizes,
                                          vector<char>* out_hash_data) {
  vector<char> payload;
  uint64_t metadata_size;
  uint64_t signatures_offset;

  TEST_AND_RETURN_FALSE(PrepPayloadForHashing(payload_path,
                                              signature_sizes,
                                              &payload,
                                              &metadata_size,
                                              &signatures_offset));

  // Calculates the hash on the updated payload. Note that we stop calculating
  // before we reach the signature information.
  TEST_AND_RETURN_FALSE(OmahaHashCalculator::RawHashOfBytes(&payload[0],
                                                            signatures_offset,
                                                            out_hash_data));
  return true;
}

bool PayloadSigner::HashMetadataForSigning(const string& payload_path,
                                           const vector<int>& signature_sizes,
                                           vector<char>* out_metadata_hash) {
  vector<char> payload;
  uint64_t metadata_size;
  uint64_t signatures_offset;

  TEST_AND_RETURN_FALSE(PrepPayloadForHashing(payload_path,
                                              signature_sizes,
                                              &payload,
                                              &metadata_size,
                                              &signatures_offset));

  // Calculates the hash on the manifest.
  TEST_AND_RETURN_FALSE(OmahaHashCalculator::RawHashOfBytes(&payload[0],
                                                            metadata_size,
                                                            out_metadata_hash));
  return true;
}

bool PayloadSigner::AddSignatureToPayload(
    const string& payload_path,
    const vector<vector<char> >& signatures,
    const string& signed_payload_path,
    uint64_t *out_metadata_size) {
  // TODO(petkov): Reduce memory usage -- the payload is manipulated in memory.

  // Loads the payload and adds the signature op to it.
  vector<char> signature_blob;
  TEST_AND_RETURN_FALSE(ConvertSignatureToProtobufBlob(signatures,
                                                       &signature_blob));
  vector<char> payload;
  uint64_t signatures_offset;
  TEST_AND_RETURN_FALSE(AddSignatureOpToPayload(payload_path,
                                                signature_blob.size(),
                                                &payload,
                                                out_metadata_size,
                                                &signatures_offset));
  // Appends the signature blob to the end of the payload and writes the new
  // payload.
  LOG(INFO) << "Payload size before signatures: " << payload.size();
  payload.resize(signatures_offset);
  payload.insert(payload.begin() + signatures_offset,
                 signature_blob.begin(),
                 signature_blob.end());
  LOG(INFO) << "Signed payload size: " << payload.size();
  TEST_AND_RETURN_FALSE(utils::WriteFile(signed_payload_path.c_str(),
                                         payload.data(),
                                         payload.size()));
  return true;
}

bool PayloadSigner::PadRSA2048SHA256Hash(std::vector<char>* hash) {
  TEST_AND_RETURN_FALSE(hash->size() == 32);
  hash->insert(hash->begin(),
               reinterpret_cast<const char*>(kRSA2048SHA256Padding),
               reinterpret_cast<const char*>(kRSA2048SHA256Padding +
                                             sizeof(kRSA2048SHA256Padding)));
  TEST_AND_RETURN_FALSE(hash->size() == 256);
  return true;
}

bool PayloadSigner::GetMetadataSignature(const char* const metadata,
                                         size_t metadata_size,
                                         const string& private_key_path,
                                         string* out_signature) {
  // Calculates the hash on the updated payload. Note that the payload includes
  // the signature op but doesn't include the signature blob at the end.
  vector<char> metadata_hash;
  TEST_AND_RETURN_FALSE(OmahaHashCalculator::RawHashOfBytes(metadata,
                                                            metadata_size,
                                                            &metadata_hash));

  vector<char> signature;
  TEST_AND_RETURN_FALSE(SignHash(metadata_hash,
                                 private_key_path,
                                 &signature));

  TEST_AND_RETURN_FALSE(OmahaHashCalculator::Base64Encode(&signature[0],
                                                          signature.size(),
                                                          out_signature));
  return true;
}


}  // namespace chromeos_update_engine