// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab

/** \file
 *
 * This is an OSD class that implements methods for management
 * and use of otp (one time password).
 *
 */

#include <errno.h>
#include <map>
#include <list>

#include <boost/range/adaptor/reversed.hpp>

#include <liboath/oath.h>

#include "include/types.h"
#include "include/utime.h"
#include "objclass/objclass.h"

#include "common/errno.h"
#include "common/Clock.h"

#include "cls/otp/cls_otp_ops.h"
#include "cls/otp/cls_otp_types.h"

using std::list;
using std::string;
using std::set;

using ceph::bufferlist;
using ceph::encode;
using ceph::real_clock;

using namespace rados::cls::otp;


CLS_VER(1,0)
CLS_NAME(otp)

#define ATTEMPTS_PER_WINDOW 5

static string otp_header_key = "header";
static string otp_key_prefix = "otp/";

struct otp_header {
  set<string> ids;

  otp_header() {}

  void encode(bufferlist &bl) const {
    ENCODE_START(1, 1, bl);
    encode(ids, bl);
    ENCODE_FINISH(bl);
  }
  void decode(bufferlist::const_iterator &bl) {
    DECODE_START(1, bl);
    decode(ids, bl);
    DECODE_FINISH(bl);
  }
};
WRITE_CLASS_ENCODER(otp_header)

struct otp_instance {
  otp_info_t otp;

  list<otp_check_t> last_checks; 
  uint64_t last_success{0}; /* otp counter/step of last successful check */

  otp_instance() {}

  void encode(bufferlist &bl) const {
    ENCODE_START(1, 1, bl);
    encode(otp, bl);
    encode(last_checks, bl);
    encode(last_success, bl);
    ENCODE_FINISH(bl);
  }
  void decode(bufferlist::const_iterator &bl) {
    DECODE_START(1, bl);
    decode(otp, bl);
    decode(last_checks, bl);
    decode(last_success, bl);
    DECODE_FINISH(bl);
  }

  void trim_expired(const ceph::real_time& now);
  void check(const string& token, const string& val, bool *update);
  bool verify(const ceph::real_time& timestamp, const string& val);

  void find(const string& token, otp_check_t *result);
};
WRITE_CLASS_ENCODER(otp_instance)


void otp_instance::trim_expired(const ceph::real_time& now)
{
  ceph::real_time window_start = now - std::chrono::seconds(otp.step_size);

  while (!last_checks.empty() &&
         last_checks.front().timestamp < window_start) {
    last_checks.pop_front();
  }
}

void otp_instance::check(const string& token, const string& val, bool *update)
{
  ceph::real_time now = ceph::real_clock::now();
  trim_expired(now);

  if (last_checks.size() >= ATTEMPTS_PER_WINDOW) {
    /* too many attempts */
    *update = false;
    return;
  }

  otp_check_t check;
  check.token = token;
  check.timestamp = now;
  check.result = (verify(now, val) ? OTP_CHECK_SUCCESS : OTP_CHECK_FAIL);

  last_checks.push_back(check);

  *update = true;
}

bool otp_instance::verify(const ceph::real_time& timestamp, const string& val)
{
  uint64_t index;
  uint32_t secs = (uint32_t)ceph::real_clock::to_time_t(timestamp);
  int result = oath_totp_validate2(otp.seed_bin.c_str(), otp.seed_bin.length(),
                                   secs, otp.step_size, otp.time_ofs, otp.window,
                                   nullptr /* otp pos */,
                                   val.c_str());
  if (result == OATH_INVALID_OTP ||
      result < 0) {
    CLS_LOG(20, "otp check failed, result=%d", result);
    return false;
  }

  index = result + (secs - otp.time_ofs) / otp.step_size;

  if (index <= last_success) { /* already used value */
    CLS_LOG(20, "otp, use of old token: index=%lld last_success=%lld", (long long)index, (long long)last_success);
    return false;
  }

  last_success = index;

  return true;
}

void otp_instance::find(const string& token, otp_check_t *result)
{
  auto now = real_clock::now();
  trim_expired(now);

  for (auto& entry : boost::adaptors::reverse(last_checks)) {
    if (entry.token == token) {
      *result = entry;
      return;
    }
  }
  result->token = token;
  result->result = OTP_CHECK_UNKNOWN;
  result->timestamp = now;
}

static int get_otp_instance(cls_method_context_t hctx, const string& id, otp_instance *instance)
{
  bufferlist bl;
  string key = otp_key_prefix + id;
 
  int r = cls_cxx_map_get_val(hctx, key, &bl);
  if (r < 0) {
    if (r != -ENOENT) {
      CLS_ERR("error reading key %s: %d", key.c_str(), r);
    }
    return r;
  }

  try {
    auto it = bl.cbegin();
    decode(*instance, it);
  } catch (const ceph::buffer::error &err) {
    CLS_ERR("ERROR: failed to decode %s", key.c_str());
    return -EIO;
  }

  return 0;
}

static int write_otp_instance(cls_method_context_t hctx, const otp_instance& instance)
{
  string key = otp_key_prefix + instance.otp.id;

  bufferlist bl;
  encode(instance, bl);

  int r = cls_cxx_map_set_val(hctx, key, &bl);
  if (r < 0) {
    CLS_ERR("ERROR: %s(): failed to store key (otp id=%s, r=%d)", __func__, instance.otp.id.c_str(), r);
    return r;
  }

  return 0;
}

static int remove_otp_instance(cls_method_context_t hctx, const string& id)
{
  string key = otp_key_prefix + id;

  int r = cls_cxx_map_remove_key(hctx, key);
  if (r < 0) {
    CLS_ERR("ERROR: %s(): failed to remove key (otp id=%s, r=%d)", __func__, id.c_str(), r);
    return r;
  }

  return 0;
}

static int read_header(cls_method_context_t hctx, otp_header *h)
{
  bufferlist bl;
  encode(h, bl);
  int r = cls_cxx_map_get_val(hctx, otp_header_key, &bl);
  if (r == -ENOENT || r == -ENODATA) {
    *h = otp_header();
    return 0;
  }
  if (r < 0) {
    CLS_ERR("ERROR: %s(): failed to read header (r=%d)", __func__, r);
    return r;
  }

  if (bl.length() == 0) {
    *h = otp_header();
    return 0;
  }

  auto iter = bl.cbegin();
  try {
    decode(*h, iter);
  } catch (ceph::buffer::error& err) {
    CLS_ERR("failed to decode otp_header");
    return -EIO;
  }

  return 0;
}

static int write_header(cls_method_context_t hctx, const otp_header& h)
{
  bufferlist bl;
  encode(h, bl);

  int r = cls_cxx_map_set_val(hctx, otp_header_key, &bl);
  if (r < 0) {
    CLS_ERR("failed to store header (r=%d)", r);
    return r;
  }

  return 0;
}

static int parse_seed(const string& seed, SeedType seed_type, bufferlist *seed_bin)
{
  size_t slen = seed.length();
  char secret[seed.length()];
  char *psecret = secret;
  int result;
  bool need_free = false;

  seed_bin->clear();

  switch (seed_type) {
    case OTP_SEED_BASE32:
      need_free = true; /* oath_base32_decode allocates dest buffer */
      result = oath_base32_decode(seed.c_str(), seed.length(),
                                  &psecret, &slen);
      break;
    default: /* just assume hex is the default */
      result = oath_hex2bin(seed.c_str(), psecret, &slen);
  }
  if (result != OATH_OK) {
    CLS_LOG(20, "failed to parse seed");
    return -EINVAL;
  }

  seed_bin->append(psecret, slen);

  if (need_free) {
    free(psecret);
  }

  return 0;
}

static int otp_set_op(cls_method_context_t hctx,
                       bufferlist *in, bufferlist *out)
{
  CLS_LOG(20, "%s", __func__);
  cls_otp_set_otp_op op;
  try {
    auto iter = in->cbegin();
    decode(op, iter);
  } catch (const ceph::buffer::error &err) {
    CLS_ERR("ERROR: %s(): failed to decode request", __func__);
    return -EINVAL;
  }

  otp_header h;
  int r = read_header(hctx, &h);
  if (r < 0) {
    return r;
  }

  for (auto entry : op.entries) {
    otp_instance instance;
    r = get_otp_instance(hctx, entry.id, &instance);
    if (r < 0 &&
        r != -ENOENT) {
      return r;
    }
    instance.otp = entry;

    r = parse_seed(instance.otp.seed, instance.otp.seed_type, &instance.otp.seed_bin);
    if (r < 0) {
      return r;
    }

    r = write_otp_instance(hctx, instance);
    if (r < 0) {
      return r;
    }

    h.ids.insert(entry.id);
  }

  r = write_header(hctx, h);
  if (r < 0) {
    return r;
  }

  return 0;
}

static int otp_remove_op(cls_method_context_t hctx,
                          bufferlist *in, bufferlist *out)
{
  CLS_LOG(20, "%s", __func__);
  cls_otp_remove_otp_op op;
  try {
    auto iter = in->cbegin();
    decode(op, iter);
  } catch (const ceph::buffer::error &err) {
    CLS_ERR("ERROR: %s(): failed to decode request", __func__);
    return -EINVAL;
  }

  otp_header h;
  bool removed_existing = false;
  int r = read_header(hctx, &h);
  if (r < 0) {
    return r;
  }

  for (auto id : op.ids) {
    bool existed = (h.ids.find(id) != h.ids.end());
    removed_existing = (removed_existing || existed);

    if (!existed) {
      continue;
    }

    r = remove_otp_instance(hctx, id);
    if (r < 0) {
      return r;
    }

    h.ids.erase(id);
  }

  if (removed_existing) {
    r = write_header(hctx, h);
    if (r < 0) {
      return r;
    }
  }

  return 0;
}

static int otp_get_op(cls_method_context_t hctx,
                          bufferlist *in, bufferlist *out)
{
  CLS_LOG(20, "%s", __func__);
  cls_otp_get_otp_op op;
  try {
    auto iter = in->cbegin();
    decode(op, iter);
  } catch (const ceph::buffer::error &err) {
    CLS_ERR("ERROR: %s(): failed to decode request", __func__);
    return -EINVAL;
  }

  cls_otp_get_otp_reply result;

  otp_header h;
  int r;

  r = read_header(hctx, &h);
  if (r < 0) {
    return r;
  }

  if (op.get_all) {
    op.ids.clear();
    for (auto id : h.ids) {
      op.ids.push_back(id);
    }
  }

  for (auto id : op.ids) {
    bool exists = (h.ids.find(id) != h.ids.end());

    if (!exists) {
      continue;
    }

    otp_instance instance;
    r = get_otp_instance(hctx, id, &instance);
    if (r < 0) {
      return r;
    }

    result.found_entries.push_back(instance.otp);
  }

  encode(result, *out);

  return 0;
}

static int otp_check_op(cls_method_context_t hctx,
                          bufferlist *in, bufferlist *out)
{
  CLS_LOG(20, "%s", __func__);
  cls_otp_check_otp_op op;
  try {
    auto iter = in->cbegin();
    decode(op, iter);
  } catch (const ceph::buffer::error &err) {
    CLS_ERR("ERROR: %s(): failed to decode request", __func__);
    return -EINVAL;
  }

  otp_header h;
  int r;

  otp_instance instance;

  r = get_otp_instance(hctx, op.id, &instance);
  if (r < 0) {
    return r;
  }

  bool update{false};
  instance.check(op.token, op.val, &update);

  if (update) {
    r = write_otp_instance(hctx, instance);
    if (r < 0) {
      return r;
    }
  }

  return 0;
}

static int otp_get_result(cls_method_context_t hctx,
                          bufferlist *in, bufferlist *out)
{
  CLS_LOG(20, "%s", __func__);
  cls_otp_check_otp_op op;
  try {
    auto iter = in->cbegin();
    decode(op, iter);
  } catch (const ceph::buffer::error &err) {
    CLS_ERR("ERROR: %s(): failed to decode request", __func__);
    return -EINVAL;
  }

  otp_header h;
  int r;

  otp_instance instance;

  r = get_otp_instance(hctx, op.id, &instance);
  if (r < 0) {
    return r;
  }

  cls_otp_get_result_reply reply;
  instance.find(op.token, &reply.result);
  encode(reply, *out);

  return 0;
}

static int otp_get_current_time_op(cls_method_context_t hctx,
                        bufferlist *in, bufferlist *out)
{
  CLS_LOG(20, "%s", __func__);
  cls_otp_get_current_time_op op;
  try {
    auto iter = in->cbegin();
    decode(op, iter);
  } catch (const ceph::buffer::error &err) {
    CLS_ERR("ERROR: %s(): failed to decode request", __func__);
    return -EINVAL;
  }

  cls_otp_get_current_time_reply reply;
  reply.time = real_clock::now();
  encode(reply, *out);

  return 0;
}

CLS_INIT(otp)
{
  CLS_LOG(20, "Loaded otp class!");

  oath_init();

  cls_handle_t h_class;
  cls_method_handle_t h_set_otp_op;
  cls_method_handle_t h_get_otp_op;
  cls_method_handle_t h_check_otp_op;
  cls_method_handle_t h_get_result_op; /*
                                        * need to check and get check result in two phases. The
                                        * reason is that we need to update failure internally,
                                        * however, there's no way to both return a failure and
                                        * update, because a failure will cancel the operation,
                                        * and write operations will not return a value. So
                                        * we're returning a success, potentially updating the
                                        * status internally, then a subsequent request can try
                                        * to fetch the status. If it fails it means that failed
                                        * to authenticate.
                                        */
  cls_method_handle_t h_remove_otp_op;
  cls_method_handle_t h_get_current_time_op;

  cls_register("otp", &h_class);
  cls_register_cxx_method(h_class, "otp_set",
                          CLS_METHOD_RD | CLS_METHOD_WR,
                          otp_set_op, &h_set_otp_op);
  cls_register_cxx_method(h_class, "otp_get",
                          CLS_METHOD_RD,
                          otp_get_op, &h_get_otp_op);
  cls_register_cxx_method(h_class, "otp_check",
                          CLS_METHOD_RD | CLS_METHOD_WR,
                          otp_check_op, &h_check_otp_op);
  cls_register_cxx_method(h_class, "otp_get_result",
                          CLS_METHOD_RD,
                          otp_get_result, &h_get_result_op);
  cls_register_cxx_method(h_class, "otp_remove",
                          CLS_METHOD_RD | CLS_METHOD_WR,
                          otp_remove_op, &h_remove_otp_op);
  cls_register_cxx_method(h_class, "get_current_time",
                          CLS_METHOD_RD,
                          otp_get_current_time_op, &h_get_current_time_op);

  return;
}