xref: /unit/src/nxt_random.c (revision 677:91cde03ec16c)
1 
2 /*
3  * Copyright (C) Igor Sysoev
4  * Copyright (C) NGINX, Inc.
5  */
6 
7 
8 #include <nxt_main.h>
9 
10 
11 /*
12  * The pseudorandom generator based on OpenBSD arc4random.  Although it is
13  * usually stated that arc4random uses RC4 pseudorandom generation algorithm
14  * they are actually different in nxt_random_add().
15  */
16 
17 
18 #define NXT_RANDOM_KEY_SIZE  128
19 
20 
21 nxt_inline void nxt_random_start_schedule(nxt_random_t *r);
22 static void nxt_random_stir(nxt_random_t *r);
23 static void nxt_random_add(nxt_random_t *r, const u_char *key, uint32_t len);
24 nxt_inline uint8_t nxt_random_byte(nxt_random_t *r);
25 
26 
27 void
28 nxt_random_init(nxt_random_t *r)
29 {
30     nxt_random_start_schedule(r);
31 
32     nxt_random_stir(r);
33 }
34 
35 
36 nxt_inline void
37 nxt_random_start_schedule(nxt_random_t *r)
38 {
39     nxt_uint_t  i;
40 
41     r->i = 0;
42     r->j = 0;
43 
44     for (i = 0; i < 256; i++) {
45         r->s[i] = i;
46     }
47 }
48 
49 
50 static void
51 nxt_random_stir(nxt_random_t *r)
52 {
53     int             fd;
54     ssize_t         n;
55     struct timeval  tv;
56     union {
57         uint32_t    value[4];
58         u_char      bytes[NXT_RANDOM_KEY_SIZE];
59     } key;
60 
61 #if (NXT_HAVE_GETRANDOM)
62 
63     n = getrandom(&key, NXT_RANDOM_KEY_SIZE, 0);
64 
65 #elif (NXT_HAVE_LINUX_SYS_GETRANDOM)
66 
67     /* Linux 3.17 SYS_getrandom. */
68 
69     n = syscall(SYS_getrandom, &key, NXT_RANDOM_KEY_SIZE, 0);
70 
71 #else
72 
73     n = 0;
74 
75 #endif
76 
77     if (n != NXT_RANDOM_KEY_SIZE) {
78         fd = open("/dev/urandom", O_RDONLY);
79 
80         if (fd >= 0) {
81             n = read(fd, &key, NXT_RANDOM_KEY_SIZE);
82             (void) close(fd);
83         }
84     }
85 
86     if (n != NXT_RANDOM_KEY_SIZE) {
87         (void) gettimeofday(&tv, NULL);
88 
89         /* XOR with stack garbage. */
90 
91         key.value[0] ^= tv.tv_usec;
92         key.value[1] ^= tv.tv_sec;
93         key.value[2] ^= nxt_pid;
94         key.value[3] ^= (uintptr_t) nxt_thread_tid(NULL);
95     }
96 
97     nxt_random_add(r, key.bytes, NXT_RANDOM_KEY_SIZE);
98 
99     /* Drop the first 3072 bytes. */
100     for (n = 3072; n != 0; n--) {
101         (void) nxt_random_byte(r);
102     }
103 
104     /* Stir again after 1,600,000 bytes. */
105     r->count = 400000;
106 }
107 
108 
109 static void
110 nxt_random_add(nxt_random_t *r, const u_char *key, uint32_t len)
111 {
112     uint8_t   val;
113     uint32_t  n;
114 
115     for (n = 0; n < 256; n++) {
116         val = r->s[r->i];
117         r->j += val + key[n % len];
118 
119         r->s[r->i] = r->s[r->j];
120         r->s[r->j] = val;
121 
122         r->i++;
123     }
124 
125     /* This index is not decremented in RC4 algorithm. */
126     r->i--;
127 
128     r->j = r->i;
129 }
130 
131 
132 uint32_t
133 nxt_random(nxt_random_t *r)
134 {
135     uint32_t  val;
136 
137     r->count--;
138 
139     if (r->count <= 0) {
140         nxt_random_stir(r);
141     }
142 
143     val  = nxt_random_byte(r) << 24;
144     val |= nxt_random_byte(r) << 16;
145     val |= nxt_random_byte(r) << 8;
146     val |= nxt_random_byte(r);
147 
148     return val;
149 }
150 
151 
152 nxt_inline uint8_t
153 nxt_random_byte(nxt_random_t *r)
154 {
155     uint8_t  si, sj;
156 
157     r->i++;
158     si = r->s[r->i];
159     r->j += si;
160 
161     sj = r->s[r->j];
162     r->s[r->i] = sj;
163     r->s[r->j] = si;
164 
165     si += sj;
166 
167     return r->s[si];
168 }
169 
170 
171 #if (NXT_TESTS)
172 
173 nxt_int_t
174 nxt_random_test(nxt_thread_t *thr)
175 {
176     nxt_uint_t    n;
177     nxt_random_t  r;
178 
179     nxt_random_start_schedule(&r);
180 
181     r.count = 400000;
182 
183     nxt_random_add(&r, (u_char *) "arc4random", sizeof("arc4random") - 1);
184 
185     /*
186      * Test arc4random() numbers.
187      * RC4 pseudorandom numbers would be 0x4642AFC3 and 0xBAF0FFF0.
188      */
189 
190     if (nxt_random(&r) == 0xD6270B27) {
191 
192         for (n = 100000; n != 0; n--) {
193             (void) nxt_random(&r);
194         }
195 
196         if (nxt_random(&r) == 0x6FCAE186) {
197             nxt_log_error(NXT_LOG_NOTICE, thr->log, "arc4random test passed");
198 
199             return NXT_OK;
200         }
201     }
202 
203     nxt_log_error(NXT_LOG_NOTICE, thr->log, "arc4random test failed");
204 
205     return NXT_ERROR;
206 }
207 
208 #endif
209