//
//
// Copyright 2015 gRPC authors.
//
// 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 "src/core/credentials/transport/tls/ssl_utils.h"

#include <grpc/credentials.h>
#include <grpc/grpc.h>
#include <grpc/grpc_crl_provider.h>
#include <grpc/impl/channel_arg_names.h>
#include <grpc/support/alloc.h>
#include <grpc/support/port_platform.h>
#include <grpc/support/string_util.h>
#include <grpc/support/sync.h>
#include <stdint.h>
#include <string.h>

#include <memory>
#include <utility>
#include <vector>

#include "src/core/config/config_vars.h"
#include "src/core/credentials/transport/tls/load_system_roots.h"
#include "src/core/ext/transport/chttp2/alpn/alpn.h"
#include "src/core/lib/channel/channel_args.h"
#include "src/core/transport/auth_context.h"
#include "src/core/tsi/ssl_transport_security.h"
#include "src/core/tsi/transport_security.h"
#include "src/core/util/grpc_check.h"
#include "src/core/util/host_port.h"
#include "src/core/util/load_file.h"
#include "src/core/util/match.h"
#include "src/core/util/ref_counted_ptr.h"
#include "src/core/util/useful.h"
#include "absl/log/log.h"
#include "absl/strings/match.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/str_split.h"

// -- Constants. --

#if defined(GRPC_ROOT_PEM_PATH)
static const char* installed_roots_path = GRPC_ROOT_PEM_PATH;
#elif defined(INSTALL_PREFIX)
static const char* installed_roots_path =
    INSTALL_PREFIX "/usr/share/grpc/roots.pem";
#else
static const char* installed_roots_path = "/usr/share/grpc/roots.pem";
#endif

#ifndef TSI_OPENSSL_ALPN_SUPPORT
#define TSI_OPENSSL_ALPN_SUPPORT 1
#endif

// -- Overridden default roots. --

static grpc_ssl_roots_override_callback ssl_roots_override_cb = nullptr;

void grpc_set_ssl_roots_override_callback(grpc_ssl_roots_override_callback cb) {
  ssl_roots_override_cb = cb;
}

// -- Cipher suites. --

static gpr_once cipher_suites_once = GPR_ONCE_INIT;
static const char* cipher_suites = nullptr;

static void init_cipher_suites(void) {
  cipher_suites = gpr_strdup(
      std::string(grpc_core::ConfigVars::Get().SslCipherSuites()).c_str());
}

// --- Util ---

const char* grpc_get_ssl_cipher_suites(void) {
  gpr_once_init(&cipher_suites_once, init_cipher_suites);
  return cipher_suites;
}

tsi_client_certificate_request_type
grpc_get_tsi_client_certificate_request_type(
    grpc_ssl_client_certificate_request_type grpc_request_type) {
  switch (grpc_request_type) {
    case GRPC_SSL_DONT_REQUEST_CLIENT_CERTIFICATE:
      return TSI_DONT_REQUEST_CLIENT_CERTIFICATE;

    case GRPC_SSL_REQUEST_CLIENT_CERTIFICATE_BUT_DONT_VERIFY:
      return TSI_REQUEST_CLIENT_CERTIFICATE_BUT_DONT_VERIFY;

    case GRPC_SSL_REQUEST_CLIENT_CERTIFICATE_AND_VERIFY:
      return TSI_REQUEST_CLIENT_CERTIFICATE_AND_VERIFY;

    case GRPC_SSL_REQUEST_AND_REQUIRE_CLIENT_CERTIFICATE_BUT_DONT_VERIFY:
      return TSI_REQUEST_AND_REQUIRE_CLIENT_CERTIFICATE_BUT_DONT_VERIFY;

    case GRPC_SSL_REQUEST_AND_REQUIRE_CLIENT_CERTIFICATE_AND_VERIFY:
      return TSI_REQUEST_AND_REQUIRE_CLIENT_CERTIFICATE_AND_VERIFY;

    default:
      return TSI_DONT_REQUEST_CLIENT_CERTIFICATE;
  }
}

tsi_tls_version grpc_get_tsi_tls_version(grpc_tls_version tls_version) {
  switch (tls_version) {
    case grpc_tls_version::TLS1_2:
      return tsi_tls_version::TSI_TLS1_2;
    case grpc_tls_version::TLS1_3:
      return tsi_tls_version::TSI_TLS1_3;
    default:
      LOG(INFO) << "Falling back to TLS 1.2.";
      return tsi_tls_version::TSI_TLS1_2;
  }
}

grpc_error_handle grpc_ssl_check_alpn(const tsi_peer* peer) {
#if TSI_OPENSSL_ALPN_SUPPORT
  // Check the ALPN if ALPN is supported.
  const tsi_peer_property* p =
      tsi_peer_get_property_by_name(peer, TSI_SSL_ALPN_SELECTED_PROTOCOL);
  if (p == nullptr) {
    return GRPC_ERROR_CREATE(
        "Cannot check peer: missing selected ALPN property.");
  }
  if (!grpc_chttp2_is_alpn_version_supported(p->value.data, p->value.length)) {
    return GRPC_ERROR_CREATE("Cannot check peer: invalid ALPN value.");
  }
#endif  // TSI_OPENSSL_ALPN_SUPPORT
  return absl::OkStatus();
}

grpc_error_handle grpc_ssl_check_peer_name(absl::string_view peer_name,
                                           const tsi_peer* peer) {
  // Check the peer name if specified.
  if (!peer_name.empty() && !grpc_ssl_host_matches_name(peer, peer_name)) {
    return GRPC_ERROR_CREATE(
        absl::StrCat("Peer name ", peer_name, " is not in peer certificate"));
  }
  return absl::OkStatus();
}

namespace grpc_core {

absl::Status SslCheckCallHost(absl::string_view host,
                              absl::string_view target_name,
                              absl::string_view overridden_target_name,
                              grpc_auth_context* auth_context) {
  grpc_security_status status = GRPC_SECURITY_ERROR;
  tsi_peer peer = grpc_shallow_peer_from_ssl_auth_context(auth_context);
  if (grpc_ssl_host_matches_name(&peer, host)) status = GRPC_SECURITY_OK;
  // If the target name was overridden, then the original target_name was
  //'checked' transitively during the previous peer check at the end of the
  // handshake.
  if (!overridden_target_name.empty() && host == target_name) {
    status = GRPC_SECURITY_OK;
  }
  if (status != GRPC_SECURITY_OK) {
    LOG(ERROR) << "call host does not match SSL server name";
    grpc_shallow_peer_destruct(&peer);
    return absl::UnauthenticatedError(
        "call host does not match SSL server name");
  }
  grpc_shallow_peer_destruct(&peer);
  return absl::OkStatus();
}

}  // namespace grpc_core

const char** grpc_fill_alpn_protocol_strings(size_t* num_alpn_protocols) {
  GRPC_CHECK_NE(num_alpn_protocols, nullptr);
  *num_alpn_protocols = grpc_chttp2_num_alpn_versions();
  const char** alpn_protocol_strings = static_cast<const char**>(
      gpr_malloc(sizeof(const char*) * (*num_alpn_protocols)));
  for (size_t i = 0; i < *num_alpn_protocols; i++) {
    alpn_protocol_strings[i] = grpc_chttp2_get_alpn_version_index(i);
  }
  return alpn_protocol_strings;
}

const char** ParseAlpnStringIntoArray(absl::string_view preferred_protocols_raw,
                                      size_t* num_alpn_protocols) {
  GRPC_CHECK_NE(num_alpn_protocols, nullptr);
  std::vector<std::string> preferred_protocols;
  preferred_protocols =
      absl::StrSplit(preferred_protocols_raw, ',', absl::SkipWhitespace());
  *num_alpn_protocols = preferred_protocols.size();
  const char** alpn_protocol_strings = nullptr;
  if (*num_alpn_protocols != 0) {
    alpn_protocol_strings = static_cast<const char**>(
        gpr_malloc(sizeof(const char*) * (*num_alpn_protocols)));
    for (size_t i = 0; i < *num_alpn_protocols; i++) {
      alpn_protocol_strings[i] = gpr_strdup(preferred_protocols[i].c_str());
    }
  }
  return alpn_protocol_strings;
}

int grpc_ssl_host_matches_name(const tsi_peer* peer,
                               absl::string_view peer_name) {
  absl::string_view allocated_name;
  absl::string_view ignored_port;
  grpc_core::SplitHostPort(peer_name, &allocated_name, &ignored_port);
  if (allocated_name.empty()) return 0;

  // IPv6 zone-id should not be included in comparisons.
  const size_t zone_id = allocated_name.find('%');
  if (zone_id != absl::string_view::npos) {
    allocated_name.remove_suffix(allocated_name.size() - zone_id);
  }
  return tsi_ssl_peer_matches_name(peer, allocated_name);
}

int grpc_ssl_cmp_target_name(absl::string_view target_name,
                             absl::string_view other_target_name,
                             absl::string_view overridden_target_name,
                             absl::string_view other_overridden_target_name) {
  int c = target_name.compare(other_target_name);
  if (c != 0) return c;
  return overridden_target_name.compare(other_overridden_target_name);
}

static bool IsSpiffeId(absl::string_view uri) {
  // Return false without logging for a non-spiffe uri scheme.
  if (!absl::StartsWith(uri, "spiffe://")) {
    return false;
  };
  if (uri.size() > 2048) {
    GRPC_TRACE_LOG(tsi, INFO)
        << "Invalid SPIFFE ID: ID longer than 2048 bytes.";
    return false;
  }
  std::vector<absl::string_view> splits = absl::StrSplit(uri, '/');
  if (splits.size() < 4 || splits[3].empty()) {
    GRPC_TRACE_LOG(tsi, INFO) << "Invalid SPIFFE ID: workload id is empty.";
    return false;
  }
  if (splits[2].size() > 255) {
    GRPC_TRACE_LOG(tsi, INFO)
        << "Invalid SPIFFE ID: domain longer than 255 characters.";
    return false;
  }
  return true;
}

grpc_core::RefCountedPtr<grpc_auth_context> grpc_ssl_peer_to_auth_context(
    const tsi_peer* peer, const char* transport_security_type) {
  size_t i;
  const char* peer_identity_property_name = nullptr;

  // The caller has checked the certificate type property.
  GRPC_CHECK_GE(peer->property_count, 1u);
  grpc_core::RefCountedPtr<grpc_auth_context> ctx =
      grpc_core::MakeRefCounted<grpc_auth_context>(nullptr);
  grpc_auth_context_add_cstring_property(
      ctx.get(), GRPC_TRANSPORT_SECURITY_TYPE_PROPERTY_NAME,
      transport_security_type);
  const char* spiffe_data = nullptr;
  size_t spiffe_length = 0;
  int uri_count = 0;
  bool has_spiffe_id = false;
  for (i = 0; i < peer->property_count; i++) {
    const tsi_peer_property* prop = &peer->properties[i];
    if (prop->name == nullptr) continue;
    if (strcmp(prop->name, TSI_X509_SUBJECT_PEER_PROPERTY) == 0) {
      grpc_auth_context_add_property(ctx.get(), GRPC_X509_SUBJECT_PROPERTY_NAME,
                                     prop->value.data, prop->value.length);
    } else if (strcmp(prop->name, TSI_X509_SUBJECT_COMMON_NAME_PEER_PROPERTY) ==
               0) {
      // If there is no subject alt name, have the CN as the identity.
      if (peer_identity_property_name == nullptr) {
        peer_identity_property_name = GRPC_X509_CN_PROPERTY_NAME;
      }
      grpc_auth_context_add_property(ctx.get(), GRPC_X509_CN_PROPERTY_NAME,
                                     prop->value.data, prop->value.length);
    } else if (strcmp(prop->name,
                      TSI_X509_SUBJECT_ALTERNATIVE_NAME_PEER_PROPERTY) == 0) {
      peer_identity_property_name = GRPC_X509_SAN_PROPERTY_NAME;
      grpc_auth_context_add_property(ctx.get(), GRPC_X509_SAN_PROPERTY_NAME,
                                     prop->value.data, prop->value.length);
    } else if (strcmp(prop->name, TSI_X509_PEM_CERT_PROPERTY) == 0) {
      grpc_auth_context_add_property(ctx.get(),
                                     GRPC_X509_PEM_CERT_PROPERTY_NAME,
                                     prop->value.data, prop->value.length);
    } else if (strcmp(prop->name, TSI_X509_PEM_CERT_CHAIN_PROPERTY) == 0) {
      grpc_auth_context_add_property(ctx.get(),
                                     GRPC_X509_PEM_CERT_CHAIN_PROPERTY_NAME,
                                     prop->value.data, prop->value.length);
    } else if (strcmp(prop->name, TSI_SSL_SESSION_REUSED_PEER_PROPERTY) == 0) {
      grpc_auth_context_add_property(ctx.get(),
                                     GRPC_SSL_SESSION_REUSED_PROPERTY,
                                     prop->value.data, prop->value.length);
    } else if (strcmp(prop->name, TSI_SECURITY_LEVEL_PEER_PROPERTY) == 0) {
      grpc_auth_context_add_property(
          ctx.get(), GRPC_TRANSPORT_SECURITY_LEVEL_PROPERTY_NAME,
          prop->value.data, prop->value.length);
    } else if (strcmp(prop->name, TSI_X509_DNS_PEER_PROPERTY) == 0) {
      grpc_auth_context_add_property(ctx.get(), GRPC_PEER_DNS_PROPERTY_NAME,
                                     prop->value.data, prop->value.length);
    } else if (strcmp(prop->name, TSI_X509_URI_PEER_PROPERTY) == 0) {
      grpc_auth_context_add_property(ctx.get(), GRPC_PEER_URI_PROPERTY_NAME,
                                     prop->value.data, prop->value.length);
      uri_count++;
      absl::string_view spiffe_id(prop->value.data, prop->value.length);
      if (IsSpiffeId(spiffe_id)) {
        spiffe_data = prop->value.data;
        spiffe_length = prop->value.length;
        has_spiffe_id = true;
      }
    } else if (strcmp(prop->name, TSI_X509_EMAIL_PEER_PROPERTY) == 0) {
      grpc_auth_context_add_property(ctx.get(), GRPC_PEER_EMAIL_PROPERTY_NAME,
                                     prop->value.data, prop->value.length);
    } else if (strcmp(prop->name, TSI_X509_IP_PEER_PROPERTY) == 0) {
      grpc_auth_context_add_property(ctx.get(), GRPC_PEER_IP_PROPERTY_NAME,
                                     prop->value.data, prop->value.length);
    }
  }
  if (peer_identity_property_name != nullptr) {
    GRPC_CHECK(grpc_auth_context_set_peer_identity_property_name(
                   ctx.get(), peer_identity_property_name) == 1);
  }
  // A valid SPIFFE certificate can only have exact one URI SAN field.
  if (has_spiffe_id) {
    if (uri_count == 1) {
      GRPC_CHECK_GT(spiffe_length, 0u);
      GRPC_CHECK_NE(spiffe_data, nullptr);
      grpc_auth_context_add_property(ctx.get(),
                                     GRPC_PEER_SPIFFE_ID_PROPERTY_NAME,
                                     spiffe_data, spiffe_length);
    } else {
      GRPC_TRACE_LOG(tsi, INFO) << "Invalid SPIFFE ID: multiple URI SANs.";
    }
  }
  return ctx;
}

static void add_shallow_auth_property_to_peer(tsi_peer* peer,
                                              const grpc_auth_property* prop,
                                              const char* tsi_prop_name) {
  tsi_peer_property* tsi_prop = &peer->properties[peer->property_count++];
  tsi_prop->name = const_cast<char*>(tsi_prop_name);
  tsi_prop->value.data = prop->value;
  tsi_prop->value.length = prop->value_length;
}

tsi_peer grpc_shallow_peer_from_ssl_auth_context(
    const grpc_auth_context* auth_context) {
  size_t max_num_props = 0;
  grpc_auth_property_iterator it;
  const grpc_auth_property* prop;
  tsi_peer peer;
  memset(&peer, 0, sizeof(peer));

  it = grpc_auth_context_property_iterator(auth_context);
  while (grpc_auth_property_iterator_next(&it) != nullptr) max_num_props++;

  if (max_num_props > 0) {
    peer.properties = static_cast<tsi_peer_property*>(
        gpr_malloc(max_num_props * sizeof(tsi_peer_property)));
    it = grpc_auth_context_property_iterator(auth_context);
    while ((prop = grpc_auth_property_iterator_next(&it)) != nullptr) {
      if (strcmp(prop->name, GRPC_X509_SAN_PROPERTY_NAME) == 0) {
        add_shallow_auth_property_to_peer(
            &peer, prop, TSI_X509_SUBJECT_ALTERNATIVE_NAME_PEER_PROPERTY);
      } else if (strcmp(prop->name, GRPC_X509_SUBJECT_PROPERTY_NAME) == 0) {
        add_shallow_auth_property_to_peer(&peer, prop,
                                          TSI_X509_SUBJECT_PEER_PROPERTY);
      } else if (strcmp(prop->name, GRPC_X509_CN_PROPERTY_NAME) == 0) {
        add_shallow_auth_property_to_peer(
            &peer, prop, TSI_X509_SUBJECT_COMMON_NAME_PEER_PROPERTY);
      } else if (strcmp(prop->name, GRPC_X509_PEM_CERT_PROPERTY_NAME) == 0) {
        add_shallow_auth_property_to_peer(&peer, prop,
                                          TSI_X509_PEM_CERT_PROPERTY);
      } else if (strcmp(prop->name,
                        GRPC_TRANSPORT_SECURITY_LEVEL_PROPERTY_NAME) == 0) {
        add_shallow_auth_property_to_peer(&peer, prop,
                                          TSI_SECURITY_LEVEL_PEER_PROPERTY);
      } else if (strcmp(prop->name, GRPC_X509_PEM_CERT_CHAIN_PROPERTY_NAME) ==
                 0) {
        add_shallow_auth_property_to_peer(&peer, prop,
                                          TSI_X509_PEM_CERT_CHAIN_PROPERTY);
      } else if (strcmp(prop->name, GRPC_PEER_DNS_PROPERTY_NAME) == 0) {
        add_shallow_auth_property_to_peer(&peer, prop,
                                          TSI_X509_DNS_PEER_PROPERTY);
      } else if (strcmp(prop->name, GRPC_PEER_URI_PROPERTY_NAME) == 0) {
        add_shallow_auth_property_to_peer(&peer, prop,
                                          TSI_X509_URI_PEER_PROPERTY);
      } else if (strcmp(prop->name, GRPC_PEER_SPIFFE_ID_PROPERTY_NAME) == 0) {
        add_shallow_auth_property_to_peer(&peer, prop,
                                          TSI_X509_URI_PEER_PROPERTY);
      } else if (strcmp(prop->name, GRPC_PEER_EMAIL_PROPERTY_NAME) == 0) {
        add_shallow_auth_property_to_peer(&peer, prop,
                                          TSI_X509_EMAIL_PEER_PROPERTY);
      } else if (strcmp(prop->name, GRPC_PEER_IP_PROPERTY_NAME) == 0) {
        add_shallow_auth_property_to_peer(&peer, prop,
                                          TSI_X509_IP_PEER_PROPERTY);
      }
    }
  }
  return peer;
}

void grpc_shallow_peer_destruct(tsi_peer* peer) {
  if (peer->properties != nullptr) gpr_free(peer->properties);
}

grpc_security_status grpc_ssl_tsi_client_handshaker_factory_init(
    tsi_ssl_pem_key_cert_pair* pem_key_cert_pair,
    std::shared_ptr<tsi::RootCertInfo> root_cert_info,
    bool skip_server_certificate_verification, tsi_tls_version min_tls_version,
    tsi_tls_version max_tls_version, tsi_ssl_session_cache* ssl_session_cache,
    tsi::TlsSessionKeyLoggerCache::TlsSessionKeyLogger* tls_session_key_logger,
    const char* crl_directory,
    std::shared_ptr<grpc_core::experimental::CrlProvider> crl_provider,
    tsi_ssl_client_handshaker_factory** handshaker_factory) {
  const char* root_certs = nullptr;
  const tsi_ssl_root_certs_store* root_store = nullptr;
  tsi_ssl_client_handshaker_options options;
  bool roots_are_configured = root_cert_info != nullptr;
  if (!roots_are_configured && !skip_server_certificate_verification) {
    GRPC_TRACE_LOG(tsi, INFO)
        << "No root certificates specified; use ones stored in system "
           "default locations instead";
    // Use default root certificates.
    root_certs = grpc_core::DefaultSslRootStore::GetPemRootCerts();
    if (root_certs == nullptr) {
      LOG(ERROR) << "Could not get default pem root certs.";
      return GRPC_SECURITY_ERROR;
    }
    root_store = grpc_core::DefaultSslRootStore::GetRootStore();
    options.root_cert_info = std::make_shared<tsi::RootCertInfo>(root_certs);
  } else {
    options.root_cert_info = std::move(root_cert_info);
  }
  bool has_key_cert_pair =
      pem_key_cert_pair != nullptr &&
      !grpc_core::IsPrivateKeyEmpty(pem_key_cert_pair->private_key) &&
      !pem_key_cert_pair->cert_chain.empty();
  options.root_store = root_store;
  options.alpn_protocols =
      grpc_fill_alpn_protocol_strings(&options.num_alpn_protocols);
  if (has_key_cert_pair) {
    options.pem_key_cert_pair = pem_key_cert_pair;
  }
  options.cipher_suites = grpc_get_ssl_cipher_suites();
  options.session_cache = ssl_session_cache;
  options.key_logger = tls_session_key_logger;
  options.skip_server_certificate_verification =
      skip_server_certificate_verification;
  options.min_tls_version = min_tls_version;
  options.max_tls_version = max_tls_version;
  options.crl_directory = crl_directory;
  options.crl_provider = std::move(crl_provider);
  const tsi_result result =
      tsi_create_ssl_client_handshaker_factory_with_options(&options,
                                                            handshaker_factory);
  gpr_free(options.alpn_protocols);
  if (result != TSI_OK) {
    LOG(ERROR) << "Handshaker factory creation failed with "
               << tsi_result_to_string(result);
    return GRPC_SECURITY_ERROR;
  }
  return GRPC_SECURITY_OK;
}

grpc_security_status grpc_ssl_tsi_server_handshaker_factory_init(
    std::vector<tsi_ssl_pem_key_cert_pair> pem_key_cert_pairs,
    std::shared_ptr<tsi::RootCertInfo> root_cert_info,
    grpc_ssl_client_certificate_request_type client_certificate_request,
    tsi_tls_version min_tls_version, tsi_tls_version max_tls_version,
    tsi::TlsSessionKeyLoggerCache::TlsSessionKeyLogger* tls_session_key_logger,
    const char* crl_directory, bool send_client_ca_list,
    std::shared_ptr<grpc_core::experimental::CrlProvider> crl_provider,
    tsi_ssl_server_handshaker_factory** handshaker_factory) {
  size_t num_alpn_protocols = 0;
  const char** alpn_protocol_strings =
      grpc_fill_alpn_protocol_strings(&num_alpn_protocols);
  tsi_ssl_server_handshaker_options options;
  options.pem_key_cert_pairs = pem_key_cert_pairs;
  options.client_certificate_request =
      grpc_get_tsi_client_certificate_request_type(client_certificate_request);
  options.cipher_suites = grpc_get_ssl_cipher_suites();
  options.alpn_protocols = alpn_protocol_strings;
  options.num_alpn_protocols = static_cast<uint16_t>(num_alpn_protocols);
  options.min_tls_version = min_tls_version;
  options.max_tls_version = max_tls_version;
  options.key_logger = tls_session_key_logger;
  options.crl_directory = crl_directory;
  options.crl_provider = std::move(crl_provider);
  options.send_client_ca_list = send_client_ca_list;
  options.root_cert_info = std::move(root_cert_info);
  const tsi_result result =
      tsi_create_ssl_server_handshaker_factory_with_options(&options,
                                                            handshaker_factory);
  gpr_free(alpn_protocol_strings);
  if (result != TSI_OK) {
    LOG(ERROR) << "Handshaker factory creation failed with "
               << tsi_result_to_string(result);
    return GRPC_SECURITY_ERROR;
  }
  return GRPC_SECURITY_OK;
}

// --- Ssl cache implementation. ---

grpc_ssl_session_cache* grpc_ssl_session_cache_create_lru(size_t capacity) {
  tsi_ssl_session_cache* cache = tsi_ssl_session_cache_create_lru(capacity);
  return reinterpret_cast<grpc_ssl_session_cache*>(cache);
}

void grpc_ssl_session_cache_destroy(grpc_ssl_session_cache* cache) {
  tsi_ssl_session_cache* tsi_cache =
      reinterpret_cast<tsi_ssl_session_cache*>(cache);
  tsi_ssl_session_cache_unref(tsi_cache);
}

static void* grpc_ssl_session_cache_arg_copy(void* p) {
  tsi_ssl_session_cache* tsi_cache =
      reinterpret_cast<tsi_ssl_session_cache*>(p);
  // destroy call below will unref the pointer.
  tsi_ssl_session_cache_ref(tsi_cache);
  return p;
}

static void grpc_ssl_session_cache_arg_destroy(void* p) {
  tsi_ssl_session_cache* tsi_cache =
      reinterpret_cast<tsi_ssl_session_cache*>(p);
  tsi_ssl_session_cache_unref(tsi_cache);
}

static int grpc_ssl_session_cache_arg_cmp(void* p, void* q) {
  return grpc_core::QsortCompare(p, q);
}

grpc_arg grpc_ssl_session_cache_create_channel_arg(
    grpc_ssl_session_cache* cache) {
  static const grpc_arg_pointer_vtable vtable = {
      grpc_ssl_session_cache_arg_copy,
      grpc_ssl_session_cache_arg_destroy,
      grpc_ssl_session_cache_arg_cmp,
  };
  return grpc_channel_arg_pointer_create(
      const_cast<char*>(GRPC_SSL_SESSION_CACHE_ARG), cache, &vtable);
}

// --- Default SSL root store implementation. ---

namespace grpc_core {

bool IsPrivateKeyEmpty(const PrivateKey& private_key) {
  return Match(
      private_key,
      [&](const std::string& pem_root_certs) { return pem_root_certs.empty(); },
      [&](const std::shared_ptr<PrivateKeySigner> key_signer) {
        return key_signer == nullptr;
      });
}

tsi_ssl_root_certs_store* DefaultSslRootStore::default_root_store_;
grpc_slice DefaultSslRootStore::default_pem_root_certs_;

const tsi_ssl_root_certs_store* DefaultSslRootStore::GetRootStore() {
  InitRootStore();
  return default_root_store_;
}

const char* DefaultSslRootStore::GetPemRootCerts() {
  InitRootStore();
  return GRPC_SLICE_IS_EMPTY(default_pem_root_certs_)
             ? nullptr
             : reinterpret_cast<const char*>
                   GRPC_SLICE_START_PTR(default_pem_root_certs_);
}

grpc_slice DefaultSslRootStore::ComputePemRootCerts() {
  Slice result;
  // First try to load the roots from the configuration.
  std::string default_root_certs_path =
      ConfigVars::Get().DefaultSslRootsFilePath();
  if (!default_root_certs_path.empty()) {
    auto slice =
        LoadFile(default_root_certs_path, /*add_null_terminator=*/true);
    if (!slice.ok()) {
      LOG(ERROR) << "error loading file " << default_root_certs_path << ": "
                 << slice.status();
    } else {
      result = std::move(*slice);
    }
  }
  // Try loading roots from OS trust store if preferred over callback.
  if (result.empty() &&
      ConfigVars::Get().UseSystemRootsOverLanguageCallback()) {
    result = Slice(LoadSystemRootCerts());
  }
  // Try overridden roots if needed.
  grpc_ssl_roots_override_result ovrd_res = GRPC_SSL_ROOTS_OVERRIDE_FAIL;
  if (result.empty() && ssl_roots_override_cb != nullptr) {
    char* pem_root_certs = nullptr;
    ovrd_res = ssl_roots_override_cb(&pem_root_certs);
    if (ovrd_res == GRPC_SSL_ROOTS_OVERRIDE_OK) {
      GRPC_CHECK_NE(pem_root_certs, nullptr);
      result = Slice::FromCopiedBuffer(
          pem_root_certs,
          strlen(pem_root_certs) + 1);  // nullptr terminator.
    }
    gpr_free(pem_root_certs);
  }
  // Try loading roots from OS trust store if flag is enabled.
  if (result.empty() && !ConfigVars::Get().NotUseSystemSslRoots()) {
    result = Slice(LoadSystemRootCerts());
  }
  // Fallback to roots manually shipped with gRPC.
  if (result.empty() && ovrd_res != GRPC_SSL_ROOTS_OVERRIDE_FAIL_PERMANENTLY) {
    auto slice = LoadFile(installed_roots_path, /*add_null_terminator=*/true);
    if (!slice.ok()) {
      LOG(ERROR) << "error loading file " << installed_roots_path << ": "
                 << slice.status();
    } else {
      result = std::move(*slice);
    }
  }
  return result.TakeCSlice();
}

void DefaultSslRootStore::InitRootStore() {
  static gpr_once once = GPR_ONCE_INIT;
  gpr_once_init(&once, DefaultSslRootStore::InitRootStoreOnce);
}

void DefaultSslRootStore::InitRootStoreOnce() {
  default_pem_root_certs_ = ComputePemRootCerts();
  if (!GRPC_SLICE_IS_EMPTY(default_pem_root_certs_)) {
    default_root_store_ =
        tsi_ssl_root_certs_store_create(reinterpret_cast<const char*>(
            GRPC_SLICE_START_PTR(default_pem_root_certs_)));
  }
}

}  // namespace grpc_core
