~singpolyma/biboumi

ref: 7b3e0e0cf3eddd3537455a3605b04a48ee663f47 biboumi/src/network/resolver.cpp -rw-r--r-- 6.8 KiB
7b3e0e0c — louiz’ Make botan’s policy configurable from a file 5 years ago
                                                                                
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
#include <network/dns_handler.hpp>
#include <utils/timed_events.hpp>
#include <network/resolver.hpp>
#include <cstring>
#include <arpa/inet.h>
#include <netinet/in.h>
#ifdef UDNS_FOUND
# include <udns.h>
#endif

#include <fstream>
#include <cstdlib>
#include <sstream>
#include <chrono>
#include <map>

using namespace std::string_literals;

#ifdef UDNS_FOUND
static std::map<int, std::string> dns_error_messages {
    {DNS_E_TEMPFAIL, "Timeout while contacting DNS servers"},
    {DNS_E_PROTOCOL, "Misformatted DNS reply"},
    {DNS_E_NXDOMAIN, "Domain name not found"},
    {DNS_E_NOMEM, "Out of memory"},
    {DNS_E_BADQUERY, "Misformatted domain name"}
};
#endif

Resolver::Resolver():
#ifdef UDNS_FOUND
  resolved4(false),
  resolved6(false),
  resolving(false),
  port{},
#endif
  resolved(false),
  error_msg{}
{
}

void Resolver::resolve(const std::string& hostname, const std::string& port,
                       SuccessCallbackType success_cb, ErrorCallbackType error_cb)
{
  this->error_cb = std::move(error_cb);
  this->success_cb = std::move(success_cb);
#ifdef UDNS_FOUND
  this->port = port;
#endif

  this->start_resolving(hostname, port);
}

int Resolver::call_getaddrinfo(const char *name, const char* port, int flags)
{
  struct addrinfo hints{};
  hints.ai_flags = flags;
  hints.ai_family = AF_UNSPEC;
  hints.ai_socktype = SOCK_STREAM;
  hints.ai_protocol = 0;

  struct addrinfo* addr_res = nullptr;
  const int res = ::getaddrinfo(name, port,
                                &hints, &addr_res);

  if (res == 0 && addr_res)
    {
      if (!this->addr)
        this->addr.reset(addr_res);
      else
        { // Append this result at the end of the linked list
          struct addrinfo *rp = this->addr.get();
          while (rp->ai_next)
            rp = rp->ai_next;
          rp->ai_next = addr_res;
        }
    }

  return res;
}

#ifdef UDNS_FOUND
void Resolver::start_resolving(const std::string& hostname, const std::string& port)
{
  this->resolving = true;
  this->resolved = false;
  this->resolved4 = false;
  this->resolved6 = false;

  this->error_msg.clear();
  this->addr.reset(nullptr);

  // We first try to use it as an IP address directly. We tell getaddrinfo
  // to NOT use any DNS resolution.
  if (this->call_getaddrinfo(hostname.data(), port.data(), AI_NUMERICHOST) == 0)
    {
      this->on_resolved();
      return;
    }

  // Then we look into /etc/hosts to translate the given hostname
  const auto hosts = this->look_in_etc_hosts(hostname);
  if (!hosts.empty())
    {
      for (const auto &host: hosts)
        this->call_getaddrinfo(host.data(), port.data(), AI_NUMERICHOST);
      this->on_resolved();
      return;
    }

  // And finally, we try a DNS resolution
  auto hostname6_resolved = [](dns_ctx*, dns_rr_a6* result, void* data)
  {
    auto resolver = static_cast<Resolver*>(data);
    resolver->on_hostname6_resolved(result);
    resolver->after_resolved();
    std::free(result);
  };

  auto hostname4_resolved = [](dns_ctx*, dns_rr_a4* result, void* data)
  {
    auto resolver = static_cast<Resolver*>(data);
    resolver->on_hostname4_resolved(result);
    resolver->after_resolved();
    std::free(result);
  };

  DNSHandler::watch();
  auto res = dns_submit_a4(nullptr, hostname.data(), 0, hostname4_resolved, this);
  if (!res)
    this->on_hostname4_resolved(nullptr);
  res = dns_submit_a6(nullptr, hostname.data(), 0, hostname6_resolved, this);
  if (!res)
    this->on_hostname6_resolved(nullptr);

  this->start_timer();
}

void Resolver::start_timer()
{
  const auto timeout = dns_timeouts(nullptr, -1, 0);
  if (timeout < 0)
    return;
  TimedEvent event(std::chrono::steady_clock::now() + std::chrono::seconds(timeout), [this]() { this->start_timer(); }, "DNS");
  TimedEventsManager::instance().add_event(std::move(event));
}

std::vector<std::string> Resolver::look_in_etc_hosts(const std::string &hostname)
{
  std::ifstream hosts("/etc/hosts");
  std::string line;

  std::vector<std::string> results;
  while (std::getline(hosts, line))
    {
      if (line.empty())
        continue;

      std::string ip;
      std::istringstream line_stream(line);
      line_stream >> ip;
      if (ip.empty() || ip[0] == '#')
        continue;

      std::string host;
      while (line_stream >> host && !host.empty() && host[0] != '#')
        {
          if (hostname == host)
            {
              results.push_back(ip);
              break;
            }
        }
    }
  return results;
}

void Resolver::on_hostname4_resolved(dns_rr_a4 *result)
{
  this->resolved4 = true;

  const auto status = dns_status(nullptr);

  if (status >= 0 && result)
    {
      char buf[INET6_ADDRSTRLEN];

      for (auto i = 0; i < result->dnsa4_nrr; ++i)
        {
          inet_ntop(AF_INET, &result->dnsa4_addr[i], buf, sizeof(buf));
          this->call_getaddrinfo(buf, this->port.data(), AI_NUMERICHOST);
        }
    }
  else
    {
      const auto error = dns_error_messages.find(status);
      if (error != end(dns_error_messages))
        this->error_msg = error->second;
    }
}

void Resolver::on_hostname6_resolved(dns_rr_a6 *result)
{
  this->resolved6 = true;

  const auto status = dns_status(nullptr);

  if (status >= 0 && result)
    {
      char buf[INET6_ADDRSTRLEN];
      for (auto i = 0; i < result->dnsa6_nrr; ++i)
        {
          inet_ntop(AF_INET6, &result->dnsa6_addr[i], buf, sizeof(buf));
          this->call_getaddrinfo(buf, this->port.data(), AI_NUMERICHOST);
        }
    }
}

void Resolver::after_resolved()
{
  if (dns_active(nullptr) == 0)
    DNSHandler::unwatch();

  if (this->resolved6 && this->resolved4)
    this->on_resolved();
}

void Resolver::on_resolved()
{
  this->resolved = true;
  this->resolving = false;
  if (!this->addr)
    {
      if (this->error_cb)
        this->error_cb(this->error_msg.data());
    }
  else
    {
      if (this->success_cb)
        this->success_cb(this->addr.get());
    }
}

#else  // ifdef UDNS_FOUND

void Resolver::start_resolving(const std::string& hostname, const std::string& port)
{
  // If the resolution fails, the addr will be unset
  this->addr.reset(nullptr);

  const auto res = this->call_getaddrinfo(hostname.data(), port.data(), 0);

  this->resolved = true;

  if (res != 0)
    {
      this->error_msg = gai_strerror(res);
      if (this->error_cb)
        this->error_cb(this->error_msg.data());
    }
  else
    {
      if (this->success_cb)
        this->success_cb(this->addr.get());
    }
}
#endif  // ifdef UDNS_FOUND

std::string addr_to_string(const struct addrinfo* rp)
{
  char buf[INET6_ADDRSTRLEN];
  if (rp->ai_family == AF_INET)
    return ::inet_ntop(rp->ai_family,
                       &reinterpret_cast<sockaddr_in*>(rp->ai_addr)->sin_addr,
                       buf, sizeof(buf));
  else if (rp->ai_family == AF_INET6)
    return ::inet_ntop(rp->ai_family,
                       &reinterpret_cast<sockaddr_in6*>(rp->ai_addr)->sin6_addr,
                       buf, sizeof(buf));
  return {};
}