socket_udp.cpp

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/*
* (C) 2015,2016,2017 Jack Lloyd
* (C) 2016 Daniel Neus
* (C) 2019 Nuno Goncalves <nunojpg@gmail.com>
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#include <botan/internal/socket_udp.h>
 
#include <botan/exceptn.h>
#include <botan/mem_ops.h>
#include <botan/uri.h>
#include <botan/internal/fmt.h>
#include <botan/internal/stl_util.h>
#include <botan/internal/target_info.h>
#include <chrono>
 
#if defined(BOTAN_HAS_BOOST_ASIO)
   /*
   * We don't need serial port support anyway, and asking for it
   * causes macro conflicts with Darwin's termios.h when this
   * file is included in the amalgamation. GH #350
   */
   #define BOOST_ASIO_DISABLE_SERIAL_PORT
   #include <boost/asio.hpp>
   #include <boost/asio/system_timer.hpp>
#elif defined(BOTAN_TARGET_OS_HAS_SOCKETS)
   #include <errno.h>
   #include <fcntl.h>
   #include <netdb.h>
   #include <netinet/in.h>
   #include <string.h>
   #include <sys/socket.h>
   #include <sys/time.h>
   #include <unistd.h>
 
#elif defined(BOTAN_TARGET_OS_HAS_WINSOCK2)
   #include <ws2tcpip.h>
#endif
 
namespace Botan {
 
namespace {
 
#if defined(BOTAN_HAS_BOOST_ASIO)
class Asio_SocketUDP final : public OS::SocketUDP {
   public:
      Asio_SocketUDP(std::string_view hostname, std::string_view service, std::chrono::microseconds timeout) :
            m_timeout(timeout), m_timer(m_io), m_udp(m_io) {
         m_timer.expires_after(m_timeout);
         check_timeout();
 
         // Resolve asynchronously so the timer covers DNS as well as connect.
         // check_timeout() only closes m_udp, which isn't open yet during the
         // resolve, so cancel the resolver inline if the deadline passes.
         boost::asio::ip::udp::resolver resolver(m_io);
         boost::asio::ip::udp::resolver::results_type dns_iter;
         boost::system::error_code resolve_ec = boost::asio::error::would_block;
         resolver.async_resolve(
            std::string{hostname}, std::string{service}, [&](const boost::system::error_code& e, auto results) {
               resolve_ec = e;
               dns_iter = std::move(results);
            });
         while(resolve_ec == boost::asio::error::would_block) {
            if(m_timer.expiry() < decltype(m_timer)::clock_type::now()) {
               resolver.cancel();
            }
            m_io.run_one();
         }
         if(resolve_ec) {
            throw boost::system::system_error(resolve_ec);
         }
 
         boost::system::error_code ec = boost::asio::error::would_block;
 
         auto connect_cb = [&ec](const boost::system::error_code& e,
                                 const boost::asio::ip::udp::resolver::results_type::iterator&) { ec = e; };
 
         boost::asio::async_connect(m_udp, dns_iter.begin(), dns_iter.end(), connect_cb);
 
         while(ec == boost::asio::error::would_block) {
            m_io.run_one();
         }
 
         if(ec) {
            throw boost::system::system_error(ec);
         }
         if(!m_udp.is_open()) {
            throw System_Error(fmt("Connection to host {} failed", hostname));
         }
      }
 
      void write(const uint8_t buf[], size_t len) override {
         m_timer.expires_after(m_timeout);
 
         boost::system::error_code ec = boost::asio::error::would_block;
 
         m_udp.async_send(boost::asio::buffer(buf, len), [&ec](boost::system::error_code e, size_t) { ec = e; });
 
         while(ec == boost::asio::error::would_block) {
            m_io.run_one();
         }
 
         if(ec) {
            throw boost::system::system_error(ec);
         }
      }
 
      size_t read(uint8_t buf[], size_t len) override {
         m_timer.expires_after(m_timeout);
 
         boost::system::error_code ec = boost::asio::error::would_block;
         size_t got = 0;
 
         m_udp.async_receive(boost::asio::buffer(buf, len), [&](boost::system::error_code cb_ec, size_t cb_got) {
            ec = cb_ec;
            got = cb_got;
         });
 
         while(ec == boost::asio::error::would_block) {
            m_io.run_one();
         }
 
         if(ec) {
            if(ec == boost::asio::error::eof) {
               return 0;
            }
            throw boost::system::system_error(ec);  // Some other error.
         }
 
         return got;
      }
 
   private:
      void check_timeout() {
         if(m_udp.is_open() && m_timer.expiry() < decltype(m_timer)::clock_type::now()) {
            boost::system::error_code err;
 
            // NOLINTNEXTLINE(bugprone-unused-return-value,cert-err33-c)
            m_udp.close(err);
         }
 
         // NOLINTNEXTLINE(*-avoid-bind) FIXME - unclear why we can't use a lambda here
         m_timer.async_wait(std::bind(&Asio_SocketUDP::check_timeout, this));
      }
 
      const std::chrono::microseconds m_timeout;
      boost::asio::io_context m_io;
      boost::asio::system_timer m_timer;
      boost::asio::ip::udp::socket m_udp;
};
#elif defined(BOTAN_TARGET_OS_HAS_SOCKETS) || defined(BOTAN_TARGET_OS_HAS_WINSOCK2)
class BSD_SocketUDP final : public OS::SocketUDP {
   public:
      BSD_SocketUDP(std::string_view hostname, std::string_view service, std::chrono::microseconds timeout) :
            m_timeout(timeout), m_socket(invalid_socket()) {
         socket_init();
 
         // A constructor that throws does not run its destructor, so do
         // cleanup explicitly on any failure between socket_init() above and
         // the end of construction below.
         try {
            do_connect(hostname, service);
         } catch(...) {
            if(m_socket != invalid_socket()) {
               close_socket(m_socket);
               m_socket = invalid_socket();
            }
            socket_fini();
            throw;
         }
      }
 
   private:
      void do_connect(std::string_view hostname, std::string_view service) {
         const std::string hostname_str(hostname);
         const std::string service_str(service);
 
         addrinfo hints{};
         hints.ai_family = AF_UNSPEC;
         hints.ai_socktype = SOCK_DGRAM;
 
         unique_addr_info_ptr res = nullptr;
 
         const int rc = ::getaddrinfo(hostname_str.c_str(), service_str.c_str(), &hints, Botan::out_ptr(res));
         if(rc != 0) {
            throw System_Error(fmt("Name resolution failed for {}", hostname), rc);
         }
 
         for(const addrinfo* rp = res.get(); (m_socket == invalid_socket()) && (rp != nullptr); rp = rp->ai_next) {
            if(rp->ai_family != AF_INET && rp->ai_family != AF_INET6) {
               continue;
            }
 
            m_socket = ::socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
 
            if(m_socket == invalid_socket()) [[unlikely]] {
               // unsupported socket type?
               continue;
            }
 
   #if !defined(BOTAN_TARGET_OS_HAS_WINSOCK2)
            // Windows fd_set is an array of sockets and doesn't have this limitation
            if(m_socket >= FD_SETSIZE) {
               close_socket(m_socket);
               m_socket = invalid_socket();
               throw System_Error("Socket descriptor exceeds FD_SETSIZE; select() would be unsafe");
            }
   #endif
 
            set_nonblocking(m_socket);
 
            // Connect the UDP socket to the selected peer so the kernel drops
            // datagrams arriving from anyone else. Without this a stray or
            // spoofed datagram could be accepted as the response.
            //
            // ::connect on a UDP socket only records the peer address in the
            // kernel; it does not produce or consume traffic. It is effectively
            // non-blocking on every supported platform, so we don't wrap this
            // in the select() pattern used by the TCP path.
            if(::connect(m_socket, rp->ai_addr, static_cast<socklen_t>(rp->ai_addrlen)) != 0) {
               close_socket(m_socket);
               m_socket = invalid_socket();
               continue;
            }
         }
 
         if(m_socket == invalid_socket()) {
            throw System_Error(
               fmt("Connecting to {} for service {} failed with errno {}", hostname, service, last_socket_error()),
               last_socket_error());
         }
      }
 
   public:
      ~BSD_SocketUDP() override {
         close_socket(m_socket);
         m_socket = invalid_socket();
         socket_fini();
      }
 
      BSD_SocketUDP(const BSD_SocketUDP& other) = delete;
      BSD_SocketUDP(BSD_SocketUDP&& other) = delete;
      BSD_SocketUDP& operator=(const BSD_SocketUDP& other) = delete;
      BSD_SocketUDP& operator=(BSD_SocketUDP&& other) = delete;
 
      void write(const uint8_t buf[], size_t len) override {
         size_t sent_so_far = 0;
         while(sent_so_far != len) {
            fd_set write_set;
            FD_ZERO(&write_set);
            FD_SET(m_socket, &write_set);
 
            struct timeval timeout = make_timeout_tv();
            const int active = ::select(static_cast<int>(m_socket + 1), nullptr, &write_set, nullptr, &timeout);
 
            if(active < 0) {
               if(last_error_is_retryable()) {
                  continue;
               }
               throw System_Error("Socket select failed", last_socket_error());
            }
 
            if(active == 0) {
               throw System_Error("Timeout during socket write");
            }
 
            const size_t left = len - sent_so_far;
            const socket_op_ret_type sent =
               ::send(m_socket, cast_uint8_ptr_to_char(buf + sent_so_far), static_cast<sendrecv_len_type>(left), 0);
            if(sent < 0) {
               if(last_error_is_retryable()) {
                  continue;
               }
               throw System_Error("Socket write failed", last_socket_error());
            } else {
               sent_so_far += static_cast<size_t>(sent);
            }
         }
      }
 
      size_t read(uint8_t buf[], size_t len) override {
         for(;;) {
            fd_set read_set;
            FD_ZERO(&read_set);
            FD_SET(m_socket, &read_set);
 
            struct timeval timeout = make_timeout_tv();
            const int active = ::select(static_cast<int>(m_socket + 1), &read_set, nullptr, nullptr, &timeout);
 
            if(active < 0) {
               if(last_error_is_retryable()) {
                  continue;
               }
               throw System_Error("Socket select failed", last_socket_error());
            }
 
            if(active == 0) {
               throw System_Error("Timeout during socket read");
            }
 
            // Socket is connected, so recv() filters out datagrams from any
            // sender other than the configured peer.
            const socket_op_ret_type got =
               ::recv(m_socket, cast_uint8_ptr_to_char(buf), static_cast<sendrecv_len_type>(len), 0);
 
            if(got < 0) {
               if(last_error_is_retryable()) {
                  continue;
               }
               throw System_Error("Socket read failed", last_socket_error());
            }
 
            return static_cast<size_t>(got);
         }
      }
 
   private:
   #if defined(BOTAN_TARGET_OS_HAS_WINSOCK2)
      typedef SOCKET socket_type;
      typedef int socket_op_ret_type;
      typedef int sendrecv_len_type;
 
      static socket_type invalid_socket() { return INVALID_SOCKET; }
 
      static void close_socket(socket_type s) { ::closesocket(s); }
 
      static int last_socket_error() { return ::WSAGetLastError(); }
 
      static std::string get_last_socket_error() { return std::to_string(::WSAGetLastError()); }
 
      static bool nonblocking_connect_in_progress() { return (::WSAGetLastError() == WSAEWOULDBLOCK); }
 
      static bool last_error_is_retryable() { return (::WSAGetLastError() == WSAEINTR); }
 
      static void set_nonblocking(socket_type s) {
         u_long nonblocking = 1;
         ::ioctlsocket(s, FIONBIO, &nonblocking);
      }
 
      static void socket_init() {
         WSAData wsa_data;
         WORD wsa_version = MAKEWORD(2, 2);
 
         if(::WSAStartup(wsa_version, &wsa_data) != 0) {
            throw System_Error("WSAStartup() failed", WSAGetLastError());
         }
 
         if(LOBYTE(wsa_data.wVersion) != 2 || HIBYTE(wsa_data.wVersion) != 2) {
            ::WSACleanup();
            throw System_Error("Could not find a usable version of Winsock.dll");
         }
      }
 
      static void socket_fini() { ::WSACleanup(); }
   #else
      typedef int socket_type;
      typedef ssize_t socket_op_ret_type;
      typedef size_t sendrecv_len_type;
 
      static socket_type invalid_socket() { return -1; }
 
      static void close_socket(socket_type s) { ::close(s); }
 
      static int last_socket_error() { return errno; }
 
      static std::string get_last_socket_error() { return ::strerror(errno); }
 
      static bool nonblocking_connect_in_progress() { return (errno == EINPROGRESS); }
 
      static bool last_error_is_retryable() { return (errno == EINTR); }
 
      static void set_nonblocking(socket_type s) {
         // NOLINTNEXTLINE(*-vararg)
         if(::fcntl(s, F_SETFL, O_NONBLOCK) < 0) {
            throw System_Error("Setting socket to non-blocking state failed", errno);
         }
      }
 
      static void socket_init() {}
 
      static void socket_fini() {}
   #endif
      struct timeval make_timeout_tv() const {
         struct timeval tv {};
 
         tv.tv_sec = static_cast<decltype(timeval::tv_sec)>(m_timeout.count() / 1000000);
         tv.tv_usec = static_cast<decltype(timeval::tv_usec)>(m_timeout.count() % 1000000);
         return tv;
      }
 
      const std::chrono::microseconds m_timeout;
      socket_type m_socket;
 
      using unique_addr_info_ptr = std::unique_ptr<addrinfo, decltype([](addrinfo* p) {
                                                      if(p != nullptr) {
                                                         ::freeaddrinfo(p);
                                                      }
                                                   })>;
};
#endif
}  // namespace
 
std::unique_ptr<OS::SocketUDP> OS::open_socket_udp(std::string_view hostname,
                                                   std::string_view service,
                                                   std::chrono::microseconds timeout) {
#if defined(BOTAN_HAS_BOOST_ASIO)
   return std::make_unique<Asio_SocketUDP>(hostname, service, timeout);
#elif defined(BOTAN_TARGET_OS_HAS_SOCKETS) || defined(BOTAN_TARGET_OS_HAS_WINSOCK2)
   return std::make_unique<BSD_SocketUDP>(hostname, service, timeout);
#else
   BOTAN_UNUSED(hostname);
   BOTAN_UNUSED(service);
   BOTAN_UNUSED(timeout);
   return std::unique_ptr<OS::SocketUDP>();
#endif
}
 
std::unique_ptr<OS::SocketUDP> OS::open_socket_udp(std::string_view uri_string, std::chrono::microseconds timeout) {
   const auto authority = URI::Authority::from_string(uri_string);
   if(!authority.has_value() || !authority->port().has_value()) {
      throw Invalid_Argument("UDP port not specified");
   }
   return open_socket_udp(authority->host_to_string(), std::to_string(*authority->port()), timeout);
}
 
}  // namespace Botan