chaps_support.cc

// Copyright 2020 The Chromium 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 "crypto/chaps_support.h"

#include <dlfcn.h>
#include <secmodt.h>

#include "base/logging.h"
#include "base/threading/scoped_blocking_call.h"
#include "nss_util_internal.h"

namespace crypto {

namespace {

// Constants for loading the Chrome OS TPM-backed PKCS #11 library.
const char kChapsModuleName[] = "Chaps";
const char kChapsPath[] = "libchaps.so";

class ScopedChapsLoadFixup {
 public:
  ScopedChapsLoadFixup();
  ~ScopedChapsLoadFixup();

 private:
#if defined(COMPONENT_BUILD)
  void* chaps_handle_;
#endif
};

#if defined(COMPONENT_BUILD)

ScopedChapsLoadFixup::ScopedChapsLoadFixup() {
  // HACK: libchaps links the system protobuf and there are symbol conflicts
  // with the bundled copy. Load chaps with RTLD_DEEPBIND to workaround.
  chaps_handle_ = dlopen(kChapsPath, RTLD_LOCAL | RTLD_NOW | RTLD_DEEPBIND);
}

ScopedChapsLoadFixup::~ScopedChapsLoadFixup() {
  // LoadNSSModule() will have taken a 2nd reference.
  if (chaps_handle_)
    dlclose(chaps_handle_);
}

#else

ScopedChapsLoadFixup::ScopedChapsLoadFixup() = default;
ScopedChapsLoadFixup::~ScopedChapsLoadFixup() = default;

#endif  // defined(COMPONENT_BUILD)

}  // namespace

SECMODModule* LoadChaps() {
  // NSS functions may reenter //net via extension hooks. If the reentered
  // code needs to synchronously wait for a task to run but the thread pool in
  // which that task must run doesn't have enough threads to schedule it, a
  // deadlock occurs. To prevent that, the base::ScopedBlockingCall below
  // increments the thread pool capacity for the duration of the TPM
  // initialization.
  base::ScopedBlockingCall scoped_blocking_call(FROM_HERE,
                                                base::BlockingType::WILL_BLOCK);

  ScopedChapsLoadFixup chaps_loader;

  DVLOG(3) << "Loading chaps...";
  return LoadNSSModule(
      kChapsModuleName, kChapsPath,
      // For more details on these parameters, see:
      // https://developer.mozilla.org/en/PKCS11_Module_Specs
      // slotFlags=[PublicCerts] -- Certificates and public keys can be
      //   read from this slot without requiring a call to C_Login.
      // askpw=only -- Only authenticate to the token when necessary.
      "NSS=\"slotParams=(0={slotFlags=[PublicCerts] askpw=only})\"");
}

bool IsSlotProvidedByChaps(PK11SlotInfo* slot) {
  if (!slot)
    return false;

  SECMODModule* pk11_module = PK11_GetModule(slot);
  return pk11_module && base::StringPiece(pk11_module->commonName) ==
                            base::StringPiece(kChapsModuleName);
}

}  // namespace crypto