1 /* Tests for the getentropy, getrandom functions.
2 Copyright (C) 2016-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19 #include <errno.h>
20 #include <stdbool.h>
21 #include <stdio.h>
22 #include <string.h>
23 #include <sys/random.h>
24
25 /* Set to true if any errors are encountered. */
26 static bool errors;
27
28 /* Test getrandom with a single buffer length. NB: The passed-in
29 buffer must have room for four extra bytes after the specified
30 length, which are used to test that getrandom leaves those bytes
31 unchanged. */
32 static void
33 test_length (char *buffer, size_t length, unsigned int flags)
34 {
35 memset (buffer, 0, length);
36 strcpy (buffer + length, "123");
37 ssize_t ret = getrandom (buffer, length, flags);
38 if (ret < 0)
39 {
40 /* EAGAIN is an expected error with GRND_RANDOM and
41 GRND_NONBLOCK. */
42 if ((flags & GRND_RANDOM)
43 && (flags & GRND_NONBLOCK)
44 && errno == EAGAIN)
45 return;
46 printf ("error: getrandom (%zu, 0x%x): %m\n", length, flags);
47 errors = true;
48 return;
49 }
50 if (ret != length)
51 {
52 if (flags & GRND_RANDOM)
53 {
54 if (ret == 0 || ret > length)
55 {
56 printf ("error: getrandom (%zu, 0x%x) returned %zd\n",
57 length, flags, ret);
58 errors = true;
59 }
60 }
61 else
62 {
63 printf ("error: getrandom (%zu, 0x%x) returned %zd\n",
64 length, flags, ret);
65 errors = true;
66 }
67 }
68 if (length >= 7)
69 {
70 /* One spurious test failure in 2**56 is sufficiently
71 unlikely. */
72 int non_null = 0;
73 for (int i = 0; i < length; ++i)
74 non_null += buffer[i] != 0;
75 if (non_null == 0)
76 {
77 printf ("error: getrandom (%zu, 0x%x) returned all-zero bytes\n",
78 length, flags);
79 errors = true;
80 }
81 }
82 if (memcmp (buffer + length, "123", 4) != 0)
83 {
84 printf ("error: getrandom (%zu, 0x%x) wrote spurious bytes\n",
85 length, flags);
86 errors = true;
87 }
88 }
89
90 /* Call getrandom repeatedly to fill the buffer. */
91 static bool
92 getrandom_full (char *buffer, size_t length, unsigned int flags)
93 {
94 char *end = buffer + length;
95 while (buffer < end)
96 {
97 ssize_t ret = getrandom (buffer, end - buffer, flags);
98 if (ret < 0)
99 {
100 printf ("error: getrandom (%zu, 0x%x): %m\n", length, flags);
101 errors = true;
102 return false;
103 }
104 buffer += ret;
105 }
106
107 return true;
108 }
109
110 static void
111 test_flags (unsigned int flags)
112 {
113 /* Test various lengths, but only for !GRND_RANDOM, to conserve
114 entropy. */
115 {
116 enum { max_length = 300 };
117 char buffer[max_length + 4];
118 if (flags & GRND_RANDOM)
119 test_length (buffer, 0, flags);
120 else
121 {
122 for (int length = 0; length <= 9; ++length)
123 test_length (buffer, length, flags);
124 test_length (buffer, 16, flags);
125 test_length (buffer, max_length, flags);
126 }
127 }
128
129 /* Test that getrandom returns different data. */
130 if (!(flags & GRND_NONBLOCK))
131 {
132 char buffer1[8];
133 memset (buffer1, 0, sizeof (buffer1));
134
135 char buffer2[8];
136 memset (buffer2, 0, sizeof (buffer2));
137
138 if (getrandom_full (buffer1, sizeof (buffer1), flags)
139 && getrandom_full (buffer2, sizeof (buffer2), flags))
140 {
141 /* The probability that these two 8-byte buffers are equal
142 is very small (assuming that two subsequent calls to
143 getrandom result are independent, uniformly distributed
144 random variables). */
145 if (memcmp (buffer1, buffer2, sizeof (buffer1)) == 0)
146 {
147 printf ("error: getrandom returns constant value\n");
148 errors = true;
149 }
150 }
151 }
152 }
153
154 static void
155 test_getentropy (void)
156 {
157 char buf[16];
158 memset (buf, '@', sizeof (buf));
159 if (getentropy (buf, 0) != 0)
160 {
161 printf ("error: getentropy zero length: %m\n");
162 errors = true;
163 return;
164 }
165 for (size_t i = 0; i < sizeof (buf); ++i)
166 if (buf[i] != '@')
167 {
168 printf ("error: getentropy modified zero-length buffer\n");
169 errors = true;
170 return;
171 }
172
173 if (getentropy (buf, sizeof (buf)) != 0)
174 {
175 printf ("error: getentropy buf: %m\n");
176 errors = true;
177 return;
178 }
179
180 char buf2[256];
181 _Static_assert (sizeof (buf) < sizeof (buf2), "buf and buf2 compatible");
182 memset (buf2, '@', sizeof (buf2));
183 if (getentropy (buf2, sizeof (buf)) != 0)
184 {
185 printf ("error: getentropy buf2: %m\n");
186 errors = true;
187 return;
188 }
189
190 /* The probability that these two buffers are equal is very
191 small. */
192 if (memcmp (buf, buf2, sizeof (buf)) == 0)
193 {
194 printf ("error: getentropy appears to return constant bytes\n");
195 errors = true;
196 return;
197 }
198
199 for (size_t i = sizeof (buf); i < sizeof (buf2); ++i)
200 if (buf2[i] != '@')
201 {
202 printf ("error: getentropy wrote beyond the end of the buffer\n");
203 errors = true;
204 return;
205 }
206
207 char buf3[257];
208 if (getentropy (buf3, sizeof (buf3)) == 0)
209 {
210 printf ("error: getentropy successful for 257 byte buffer\n");
211 errors = true;
212 return;
213 }
214 if (errno != EIO)
215 {
216 printf ("error: getentropy wrong error for 257 byte buffer: %m\n");
217 errors = true;
218 return;
219 }
220 }
221
222 static int
223 do_test (void)
224 {
225 /* Check if getrandom is not supported by this system. */
226 if (getrandom (NULL, 0, 0) == -1 && errno == ENOSYS)
227 return 77;
228
229 for (int use_random = 0; use_random < 2; ++use_random)
230 for (int use_nonblock = 0; use_nonblock < 2; ++use_nonblock)
231 {
232 unsigned int flags = 0;
233 if (use_random)
234 flags |= GRND_RANDOM;
235 if (use_nonblock)
236 flags |= GRND_NONBLOCK;
237 test_flags (flags);
238 }
239
240 test_getentropy ();
241
242 return errors;
243 }
244
245 #include <support/test-driver.c>