// Copyright (c) 2009 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 "net/base/strict_transport_security_state.h"

#include "base/json_reader.h"
#include "base/json_writer.h"
#include "base/logging.h"
#include "base/scoped_ptr.h"
#include "base/sha2.h"
#include "base/string_tokenizer.h"
#include "base/string_util.h"
#include "base/values.h"
#include "googleurl/src/gurl.h"
#include "net/base/base64.h"
#include "net/base/dns_util.h"

namespace net {

StrictTransportSecurityState::StrictTransportSecurityState()
    : delegate_(NULL) {
}

void StrictTransportSecurityState::DidReceiveHeader(const GURL& url,
                                                    const std::string& value) {
  int max_age;
  bool include_subdomains;

  if (!ParseHeader(value, &max_age, &include_subdomains))
    return;

  base::Time current_time(base::Time::Now());
  base::TimeDelta max_age_delta = base::TimeDelta::FromSeconds(max_age);
  base::Time expiry = current_time + max_age_delta;

  EnableHost(url.host(), expiry, include_subdomains);
}

void StrictTransportSecurityState::EnableHost(const std::string& host,
                                              base::Time expiry,
                                              bool include_subdomains) {
  const std::string canonicalised_host = CanonicaliseHost(host);
  if (canonicalised_host.empty())
    return;
  char hashed[base::SHA256_LENGTH];
  base::SHA256HashString(canonicalised_host, hashed, sizeof(hashed));

  AutoLock lock(lock_);

  State state = {expiry, include_subdomains};
  enabled_hosts_[std::string(hashed, sizeof(hashed))] = state;
  DirtyNotify();
}

bool StrictTransportSecurityState::IsEnabledForHost(const std::string& host) {
  const std::string canonicalised_host = CanonicaliseHost(host);
  if (canonicalised_host.empty())
    return false;

  base::Time current_time(base::Time::Now());
  AutoLock lock(lock_);

  for (size_t i = 0; canonicalised_host[i]; i += canonicalised_host[i] + 1) {
    char hashed_domain[base::SHA256_LENGTH];

    base::SHA256HashString(&canonicalised_host[i], &hashed_domain,
                           sizeof(hashed_domain));
    std::map<std::string, State>::iterator j =
        enabled_hosts_.find(std::string(hashed_domain, sizeof(hashed_domain)));
    if (j == enabled_hosts_.end())
      continue;

    if (current_time > j->second.expiry) {
      enabled_hosts_.erase(j);
      DirtyNotify();
      continue;
    }

    // If we matched the domain exactly, it doesn't matter what the value of
    // include_subdomains is.
    if (i == 0)
      return true;

    return j->second.include_subdomains;
  }

  return false;
}

// "Strict-Transport-Security" ":"
//     "max-age" "=" delta-seconds [ ";" "includeSubDomains" ]
bool StrictTransportSecurityState::ParseHeader(const std::string& value,
                                               int* max_age,
                                               bool* include_subdomains) {
  DCHECK(max_age);
  DCHECK(include_subdomains);

  int max_age_candidate;

  enum ParserState {
    START,
    AFTER_MAX_AGE_LABEL,
    AFTER_MAX_AGE_EQUALS,
    AFTER_MAX_AGE,
    AFTER_MAX_AGE_INCLUDE_SUB_DOMAINS_DELIMITER,
    AFTER_INCLUDE_SUBDOMAINS,
  } state = START;

  StringTokenizer tokenizer(value, " \t=;");
  tokenizer.set_options(StringTokenizer::RETURN_DELIMS);
  while (tokenizer.GetNext()) {
    DCHECK(!tokenizer.token_is_delim() || tokenizer.token().length() == 1);
    switch (state) {
      case START:
        if (IsAsciiWhitespace(*tokenizer.token_begin()))
          continue;
        if (!LowerCaseEqualsASCII(tokenizer.token(), "max-age"))
          return false;
        state = AFTER_MAX_AGE_LABEL;
        break;

      case AFTER_MAX_AGE_LABEL:
        if (IsAsciiWhitespace(*tokenizer.token_begin()))
          continue;
        if (*tokenizer.token_begin() != '=')
          return false;
        DCHECK(tokenizer.token().length() ==  1);
        state = AFTER_MAX_AGE_EQUALS;
        break;

      case AFTER_MAX_AGE_EQUALS:
        if (IsAsciiWhitespace(*tokenizer.token_begin()))
          continue;
        if (!StringToInt(tokenizer.token(), &max_age_candidate))
          return false;
        if (max_age_candidate < 0)
          return false;
        state = AFTER_MAX_AGE;
        break;

      case AFTER_MAX_AGE:
        if (IsAsciiWhitespace(*tokenizer.token_begin()))
          continue;
        if (*tokenizer.token_begin() != ';')
          return false;
        state = AFTER_MAX_AGE_INCLUDE_SUB_DOMAINS_DELIMITER;
        break;

      case AFTER_MAX_AGE_INCLUDE_SUB_DOMAINS_DELIMITER:
        if (IsAsciiWhitespace(*tokenizer.token_begin()))
          continue;
        if (!LowerCaseEqualsASCII(tokenizer.token(), "includesubdomains"))
          return false;
        state = AFTER_INCLUDE_SUBDOMAINS;
        break;

      case AFTER_INCLUDE_SUBDOMAINS:
        if (!IsAsciiWhitespace(*tokenizer.token_begin()))
          return false;
        break;

      default:
        NOTREACHED();
    }
  }

  // We've consumed all the input.  Let's see what state we ended up in.
  switch (state) {
    case START:
    case AFTER_MAX_AGE_LABEL:
    case AFTER_MAX_AGE_EQUALS:
      return false;
    case AFTER_MAX_AGE:
      *max_age = max_age_candidate;
      *include_subdomains = false;
      return true;
    case AFTER_MAX_AGE_INCLUDE_SUB_DOMAINS_DELIMITER:
      return false;
    case AFTER_INCLUDE_SUBDOMAINS:
      *max_age = max_age_candidate;
      *include_subdomains = true;
      return true;
    default:
      NOTREACHED();
      return false;
  }
}

void StrictTransportSecurityState::SetDelegate(
    StrictTransportSecurityState::Delegate* delegate) {
  AutoLock lock(lock_);

  delegate_ = delegate;
}

// This function converts the binary hashes, which we store in
// |enabled_hosts_|, to a base64 string which we can include in a JSON file.
static std::wstring HashedDomainToExternalString(const std::string& hashed) {
  std::string out;
  CHECK(Base64Encode(hashed, &out));
  return ASCIIToWide(out);
}

// This inverts |HashedDomainToExternalString|, above. It turns an external
// string (from a JSON file) into an internal (binary) string.
static std::string ExternalStringToHashedDomain(const std::wstring& external) {
  std::string external_ascii = WideToASCII(external);
  std::string out;
  if (!Base64Decode(external_ascii, &out) ||
      out.size() != base::SHA256_LENGTH) {
    return std::string();
  }

  return out;
}

bool StrictTransportSecurityState::Serialise(std::string* output) {
  AutoLock lock(lock_);

  DictionaryValue toplevel;
  for (std::map<std::string, State>::const_iterator
       i = enabled_hosts_.begin(); i != enabled_hosts_.end(); ++i) {
    DictionaryValue* state = new DictionaryValue;
    state->SetBoolean(L"include_subdomains", i->second.include_subdomains);
    state->SetReal(L"expiry", i->second.expiry.ToDoubleT());

    toplevel.Set(HashedDomainToExternalString(i->first), state);
  }

  JSONWriter::Write(&toplevel, true /* pretty print */, output);
  return true;
}

bool StrictTransportSecurityState::Deserialise(const std::string& input) {
  AutoLock lock(lock_);

  enabled_hosts_.clear();

  scoped_ptr<Value> value(
      JSONReader::Read(input, false /* do not allow trailing commas */));
  if (!value.get() || !value->IsType(Value::TYPE_DICTIONARY))
    return false;

  DictionaryValue* dict_value = reinterpret_cast<DictionaryValue*>(value.get());
  const base::Time current_time(base::Time::Now());

  for (DictionaryValue::key_iterator
       i = dict_value->begin_keys(); i != dict_value->end_keys(); ++i) {
    DictionaryValue* state;
    if (!dict_value->GetDictionary(*i, &state))
      continue;

    bool include_subdomains;
    double expiry;

    if (!state->GetBoolean(L"include_subdomains", &include_subdomains) ||
        !state->GetReal(L"expiry", &expiry)) {
      continue;
    }

    base::Time expiry_time = base::Time::FromDoubleT(expiry);
    if (expiry_time <= current_time)
      continue;

    std::string hashed = ExternalStringToHashedDomain(*i);
    if (hashed.empty())
      continue;

    State new_state = { expiry_time, include_subdomains };
    enabled_hosts_[hashed] = new_state;
  }

  return true;
}

void StrictTransportSecurityState::DirtyNotify() {
  if (delegate_)
    delegate_->StateIsDirty(this);
}

// static
std::string StrictTransportSecurityState::CanonicaliseHost(
    const std::string& host) {
  // We cannot perform the operations as detailed in the spec here as |host|
  // has already undergone IDN processing before it reached us. Thus, we check
  // that there are no invalid characters in the host and lowercase the result.

  std::string new_host;
  if (!DNSDomainFromDot(host, &new_host)) {
    NOTREACHED();
    return std::string();
  }

  for (size_t i = 0; new_host[i]; i += new_host[i] + 1) {
    const unsigned label_length = static_cast<unsigned>(new_host[i]);
    if (!label_length)
      break;

    for (size_t j = 0; j < label_length; ++j) {
      // RFC 3490, 4.1, step 3
      if (!IsSTD3ASCIIValidCharacter(new_host[i + 1 + j]))
        return std::string();

      new_host[i + 1 + j] = tolower(new_host[i + 1 + j]);
    }

    // step 3(b)
    if (new_host[i + 1] == '-' ||
        new_host[i + label_length] == '-') {
      return std::string();
    }
  }

  return new_host;
}

}  // namespace