1/*
2 Copyright (c) 2007-2017 Contributors as noted in the AUTHORS file
3
4 This file is part of libzmq, the ZeroMQ core engine in C++.
5
6 libzmq is free software; you can redistribute it and/or modify it under
7 the terms of the GNU Lesser General Public License (LGPL) as published
8 by the Free Software Foundation; either version 3 of the License, or
9 (at your option) any later version.
10
11 As a special exception, the Contributors give you permission to link
12 this library with independent modules to produce an executable,
13 regardless of the license terms of these independent modules, and to
14 copy and distribute the resulting executable under terms of your choice,
15 provided that you also meet, for each linked independent module, the
16 terms and conditions of the license of that module. An independent
17 module is a module which is not derived from or based on this library.
18 If you modify this library, you must extend this exception to your
19 version of the library.
20
21 libzmq is distributed in the hope that it will be useful, but WITHOUT
22 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
23 FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
24 License for more details.
25
26 You should have received a copy of the GNU Lesser General Public License
27 along with this program. If not, see <http://www.gnu.org/licenses/>.
28*/
29
30#include "precompiled.hpp"
31#include <stdlib.h>
32
33#if !defined ZMQ_HAVE_WINDOWS
34#include <unistd.h>
35#endif
36
37#include "random.hpp"
38#include "stdint.hpp"
39#include "clock.hpp"
40#include "mutex.hpp"
41#include "macros.hpp"
42
43#if defined(ZMQ_USE_TWEETNACL)
44#include "tweetnacl.h"
45#elif defined(ZMQ_USE_LIBSODIUM)
46#include "sodium.h"
47#endif
48
49void zmq::seed_random ()
50{
51#if defined ZMQ_HAVE_WINDOWS
52 int pid = static_cast<int> (GetCurrentProcessId ());
53#else
54 int pid = static_cast<int> (getpid ());
55#endif
56 srand (static_cast<unsigned int> (clock_t::now_us () + pid));
57}
58
59uint32_t zmq::generate_random ()
60{
61 // Compensate for the fact that rand() returns signed integer.
62 uint32_t low = static_cast<uint32_t> (rand ());
63 uint32_t high = static_cast<uint32_t> (rand ());
64 high <<= (sizeof (int) * 8 - 1);
65 return high | low;
66}
67
68// When different threads have their own context the file descriptor
69// variable is shared and is subject to race conditions in tweetnacl,
70// that lead to file descriptors leaks. In long-running programs with
71// ephemeral threads this is a problem as it accumulates.
72// thread-local storage cannot be used to initialise the file descriptor
73// as it is perfectly legal to share a context among many threads, each
74// of which might call curve APIs.
75// Also libsodium documentation specifically states that sodium_init
76// must not be called concurrently from multiple threads, for the
77// same reason. Inspecting the code also reveals that the close API is
78// not thread safe.
79// The context class cannot be used with static variables as the curve
80// utility APIs like zmq_curve_keypair also call into the crypto
81// library.
82// The safest solution for all use cases therefore is to have a
83// static lock to serialize calls into an initialiser and a finaliser,
84// using refcounts to make sure that a thread does not close the library
85// while another is still using it. To avoid the static initialization
86// order fiasco, this is done using function-local statics, if the
87// compiler implementation supports thread-safe initialization of those.
88// Otherwise, we fall back to global statics.
89// HOWEVER, this initialisation code imposes ordering constraints, which
90// are not obvious to users of libzmq, and may lead to problems if atexit
91// or similar methods are used for cleanup.
92// In that case, a strict ordering is imposed whereas the contexts MUST
93// be initialised BEFORE registering the cleanup with atexit. CZMQ is an
94// example. Hence we make the choice to restrict this global transition
95// mechanism ONLY to Tweenacl + *NIX (when using /dev/urandom) as it is
96// the less risky option.
97
98// TODO if there is some other user of libsodium besides libzmq, this must
99// be synchronized by the application. This should probably also be
100// configurable via config.h
101
102// TODO this should probably be done via config.h
103#if __cplusplus >= 201103L \
104 || (defined(__cpp_threadsafe_static_init) \
105 && __cpp_threadsafe_static_init >= 200806) \
106 || (defined(_MSC_VER) && _MSC_VER >= 1900)
107#define ZMQ_HAVE_THREADSAFE_STATIC_LOCAL_INIT 1
108// TODO this might probably also be set if a sufficiently recent gcc is used
109// without -fno-threadsafe-statics, but this cannot be determined at
110// compile-time, so it must be set via config.h
111#else
112#define ZMQ_HAVE_THREADSAFE_STATIC_LOCAL_INIT 0
113#endif
114
115#if !ZMQ_HAVE_THREADSAFE_STATIC_LOCAL_INIT \
116 && (defined(ZMQ_USE_TWEETNACL) && !defined(ZMQ_HAVE_WINDOWS) \
117 && !defined(ZMQ_HAVE_GETRANDOM))
118static unsigned int random_refcount = 0;
119static zmq::mutex_t random_sync;
120#endif
121
122static void manage_random (bool init_)
123{
124#if defined(ZMQ_USE_TWEETNACL) && !defined(ZMQ_HAVE_WINDOWS) \
125 && !defined(ZMQ_HAVE_GETRANDOM)
126
127#if ZMQ_HAVE_THREADSAFE_STATIC_LOCAL_INIT
128 static int random_refcount = 0;
129 static zmq::mutex_t random_sync;
130#endif
131
132 if (init_) {
133 zmq::scoped_lock_t locker (random_sync);
134
135 if (random_refcount == 0) {
136 int rc = sodium_init ();
137 zmq_assert (rc != -1);
138 }
139
140 ++random_refcount;
141 } else {
142 zmq::scoped_lock_t locker (random_sync);
143 --random_refcount;
144
145 if (random_refcount == 0) {
146 randombytes_close ();
147 }
148 }
149
150#elif defined(ZMQ_USE_LIBSODIUM)
151 if (init_) {
152 int rc = sodium_init ();
153 zmq_assert (rc != -1);
154 } else {
155 randombytes_close ();
156 }
157#else
158 LIBZMQ_UNUSED (init_);
159#endif
160}
161
162void zmq::random_open ()
163{
164 manage_random (true);
165}
166
167void zmq::random_close ()
168{
169 manage_random (false);
170}
171