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57b90af7 JG |
1 | /* |
2 | * Copyright (C) 2023 Jérémie Galarneau <jeremie.galarneau@efficios.com> | |
3 | * | |
4 | * SPDX-License-Identifier: LGPL-2.1-only | |
5 | * | |
6 | */ | |
7 | ||
57b90af7 JG |
8 | #include <common/file-descriptor.hpp> |
9 | #include <common/format.hpp> | |
10 | #include <common/hashtable/utils.hpp> | |
11 | #include <common/random.hpp> | |
12 | #include <common/readwrite.hpp> | |
13 | #include <common/time.hpp> | |
14 | ||
28ab034a JG |
15 | #include <lttng/constant.h> |
16 | ||
57b90af7 JG |
17 | #include <fcntl.h> |
18 | ||
19 | #ifdef HAVE_SYS_SYSCALL_H | |
20 | #include <sys/syscall.h> | |
21 | #endif | |
22 | ||
23 | #define LTTNG_THROW_RANDOM_PRODUCTION_ERROR(msg) \ | |
24 | throw lttng::random::production_error(msg, __FILE__, __func__, __LINE__) | |
25 | ||
26 | namespace { | |
27 | /* getrandom is available in Linux >= 3.17. */ | |
28 | #if defined(__linux__) && defined(SYS_getrandom) && defined(HAVE_SYS_RANDOM_H) | |
29 | ||
30 | #include <sys/random.h> | |
31 | ||
32 | /* A glibc wrapper is provided only for glibc >= 2.25. */ | |
33 | #if defined(HAVE_GETRANDOM) | |
34 | /* Simply use the existing wrapper, passing the non-block flag. */ | |
35 | ssize_t _call_getrandom_nonblock(char *out_data, std::size_t size) | |
36 | { | |
37 | return getrandom(out_data, size, GRND_NONBLOCK); | |
38 | } | |
39 | #else | |
40 | ssize_t _call_getrandom_nonblock(char *out_data, std::size_t size) | |
41 | { | |
42 | const int grnd_nonblock_flag = 0x1; | |
43 | ||
44 | auto ret = syscall(SYS_getrandom, out_data, size, grnd_nonblock_flag); | |
45 | if (ret < 0) { | |
46 | errno = -ret; | |
47 | ret = -1; | |
48 | } | |
49 | ||
50 | return ret; | |
51 | } | |
52 | #endif /* defined(HAVE_GETRANDOM) */ | |
53 | ||
54 | /* Returns either with a full read or throws. */ | |
55 | void getrandom_nonblock(char *out_data, std::size_t size) | |
56 | { | |
57 | /* | |
58 | * Since GRND_RANDOM is _not_ used, a partial read can only be caused | |
59 | * by a signal interruption. In this case, retry. | |
60 | */ | |
61 | ssize_t ret; | |
62 | ||
63 | do { | |
64 | ret = _call_getrandom_nonblock(out_data, size); | |
65 | } while ((ret > 0 && ret != size) || (ret == -1 && errno == EINTR)); | |
66 | ||
67 | if (ret < 0) { | |
68 | LTTNG_THROW_POSIX( | |
28ab034a JG |
69 | fmt::format("Failed to get true random data using getrandom(): size={}", |
70 | size), | |
71 | errno); | |
57b90af7 JG |
72 | } |
73 | } | |
74 | #else /* defined(__linux__) && defined(SYS_getrandom) && defined(HAVE_SYS_RANDOM_H) */ | |
45cc2527 MJ |
75 | __attribute__((noreturn)) |
76 | void getrandom_nonblock(char *out_data __attribute__((unused)), | |
77 | std::size_t size __attribute__((unused))) | |
57b90af7 | 78 | { |
28ab034a | 79 | LTTNG_THROW_RANDOM_PRODUCTION_ERROR("getrandom() is not supported by this platform"); |
57b90af7 JG |
80 | } |
81 | #endif /* defined(__linux__) && defined(SYS_getrandom) && defined(HAVE_SYS_RANDOM_H) */ | |
82 | ||
83 | lttng::random::seed_t produce_pseudo_random_seed() | |
84 | { | |
85 | int ret; | |
86 | struct timespec real_time = {}; | |
87 | struct timespec monotonic_time = {}; | |
88 | unsigned long hash_seed; | |
89 | char hostname[LTTNG_HOST_NAME_MAX] = {}; | |
90 | unsigned long seed; | |
91 | ||
92 | ret = clock_gettime(CLOCK_REALTIME, &real_time); | |
93 | if (ret) { | |
94 | LTTNG_THROW_POSIX("Failed to read real time while generating pseudo-random seed", | |
28ab034a | 95 | errno); |
57b90af7 JG |
96 | } |
97 | ||
98 | ret = clock_gettime(CLOCK_MONOTONIC, &monotonic_time); | |
99 | if (ret) { | |
100 | LTTNG_THROW_POSIX( | |
28ab034a | 101 | "Failed to read monotonic time while generating pseudo-random seed", errno); |
57b90af7 JG |
102 | } |
103 | ||
104 | ret = gethostname(hostname, sizeof(hostname)); | |
105 | if (ret) { | |
106 | LTTNG_THROW_POSIX("Failed to get host name while generating pseudo-random seed", | |
28ab034a | 107 | errno); |
57b90af7 JG |
108 | } |
109 | ||
110 | hash_seed = (unsigned long) real_time.tv_nsec ^ (unsigned long) real_time.tv_sec ^ | |
28ab034a | 111 | (unsigned long) monotonic_time.tv_nsec ^ (unsigned long) monotonic_time.tv_sec; |
57b90af7 JG |
112 | seed = hash_key_ulong((void *) real_time.tv_sec, hash_seed); |
113 | seed ^= hash_key_ulong((void *) real_time.tv_nsec, hash_seed); | |
114 | seed ^= hash_key_ulong((void *) monotonic_time.tv_sec, hash_seed); | |
115 | seed ^= hash_key_ulong((void *) monotonic_time.tv_nsec, hash_seed); | |
116 | ||
117 | const unsigned long pid = getpid(); | |
118 | seed ^= hash_key_ulong((void *) pid, hash_seed); | |
119 | seed ^= hash_key_str(hostname, hash_seed); | |
120 | ||
121 | return static_cast<lttng::random::seed_t>(seed); | |
122 | } | |
123 | ||
124 | lttng::random::seed_t produce_random_seed_from_urandom() | |
125 | { | |
126 | /* | |
127 | * Open /dev/urandom as a file_descriptor, or throw on error. The | |
128 | * lambda is used to reduce the scope of the raw fd as much as possible. | |
129 | */ | |
28ab034a | 130 | lttng::file_descriptor urandom{ []() { |
57b90af7 JG |
131 | const auto urandom_raw_fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC); |
132 | ||
133 | if (urandom_raw_fd < 0) { | |
134 | LTTNG_THROW_POSIX("Failed to open `/dev/urandom`", errno); | |
135 | } | |
136 | ||
137 | return urandom_raw_fd; | |
28ab034a | 138 | }() }; |
57b90af7 JG |
139 | |
140 | lttng::random::seed_t seed; | |
141 | const auto read_ret = lttng_read(urandom.fd(), &seed, sizeof(seed)); | |
142 | if (read_ret != sizeof(seed)) { | |
143 | LTTNG_THROW_POSIX(fmt::format("Failed to read from `/dev/urandom`: size={}", | |
28ab034a JG |
144 | sizeof(seed)), |
145 | errno); | |
57b90af7 JG |
146 | } |
147 | ||
148 | return seed; | |
149 | } | |
150 | ||
151 | } /* namespace */ | |
152 | ||
153 | lttng::random::production_error::production_error(const std::string& msg, | |
28ab034a JG |
154 | const char *file_name, |
155 | const char *function_name, | |
156 | unsigned int line_number) : | |
57b90af7 JG |
157 | lttng::runtime_error(msg, file_name, function_name, line_number) |
158 | { | |
159 | } | |
160 | ||
161 | lttng::random::seed_t lttng::random::produce_true_random_seed() | |
162 | { | |
163 | lttng::random::seed_t seed; | |
164 | ||
165 | getrandom_nonblock(reinterpret_cast<char *>(&seed), sizeof(seed)); | |
166 | return seed; | |
167 | } | |
168 | ||
169 | lttng::random::seed_t lttng::random::produce_best_effort_random_seed() | |
170 | { | |
171 | try { | |
172 | return lttng::random::produce_true_random_seed(); | |
173 | } catch (std::exception& e) { | |
174 | WARN("%s", | |
28ab034a JG |
175 | fmt::format( |
176 | "Failed to produce a random seed using getrandom(), falling back to pseudo-random device seed generation which will block until its pool is initialized: {}", | |
177 | e.what()) | |
178 | .c_str()); | |
57b90af7 JG |
179 | } |
180 | ||
181 | try { | |
182 | /* | |
183 | * Can fail for various reasons, including not being accessible | |
184 | * under some containerized environments. | |
185 | */ | |
186 | produce_random_seed_from_urandom(); | |
187 | } catch (std::exception& e) { | |
188 | WARN("%s", | |
28ab034a JG |
189 | fmt::format("Failed to produce a random seed from the urandom device: {}", |
190 | e.what()) | |
191 | .c_str()); | |
57b90af7 JG |
192 | } |
193 | ||
194 | /* Fallback to time-based seed generation. */ | |
195 | return produce_pseudo_random_seed(); | |
196 | } |