summaryrefslogtreecommitdiffstats
path: root/Python/random.c
blob: 1ad4c3df7f8793cc71804aa08fbe98bb2077a7dd (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
#include "Python.h"
#ifdef MS_WINDOWS
#include <windows.h>
#else
#include <fcntl.h>
#endif

#ifdef Py_DEBUG
int _Py_HashSecret_Initialized = 0;
#else
static int _Py_HashSecret_Initialized = 0;
#endif

#ifdef MS_WINDOWS
/* This handle is never explicitly released. Instead, the operating
   system will release it when the process terminates. */
static HCRYPTPROV hCryptProv = 0;

static int
win32_urandom_init(int raise)
{
    /* Acquire context */
    if (!CryptAcquireContext(&hCryptProv, NULL, NULL,
                             PROV_RSA_FULL, CRYPT_VERIFYCONTEXT))
        goto error;

    return 0;

error:
    if (raise)
        PyErr_SetFromWindowsErr(0);
    else
        Py_FatalError("Failed to initialize Windows random API (CryptoGen)");
    return -1;
}

/* Fill buffer with size pseudo-random bytes generated by the Windows CryptoGen
   API. Return 0 on success, or -1 on error. */
static int
win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
{
    Py_ssize_t chunk;

    if (hCryptProv == 0)
    {
        if (win32_urandom_init(raise) == -1)
            return -1;
    }

    while (size > 0)
    {
        chunk = size > INT_MAX ? INT_MAX : size;
        if (!CryptGenRandom(hCryptProv, chunk, buffer))
        {
            /* CryptGenRandom() failed */
            if (raise)
                PyErr_SetFromWindowsErr(0);
            else
                Py_FatalError("Failed to initialized the randomized hash "
                        "secret using CryptoGen)");
            return -1;
        }
        buffer += chunk;
        size -= chunk;
    }
    return 0;
}
#endif /* MS_WINDOWS */


#ifdef __VMS
/* Use openssl random routine */
#include <openssl/rand.h>
static int
vms_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
{
    if (RAND_pseudo_bytes(buffer, size) < 0) {
        if (raise) {
            PyErr_Format(PyExc_ValueError,
                         "RAND_pseudo_bytes");
        } else {
            Py_FatalError("Failed to initialize the randomized hash "
                          "secret using RAND_pseudo_bytes");
        }
        return -1;
    }
    return 0;
}
#endif /* __VMS */


#if !defined(MS_WINDOWS) && !defined(__VMS)

/* Read size bytes from /dev/urandom into buffer.
   Call Py_FatalError() on error. */
static void
dev_urandom_noraise(char *buffer, Py_ssize_t size)
{
    int fd;
    Py_ssize_t n;

    assert (0 < size);

    fd = open("/dev/urandom", O_RDONLY);
    if (fd < 0)
        Py_FatalError("Failed to open /dev/urandom");

    while (0 < size)
    {
        do {
            n = read(fd, buffer, (size_t)size);
        } while (n < 0 && errno == EINTR);
        if (n <= 0)
        {
            /* stop on error or if read(size) returned 0 */
            Py_FatalError("Failed to read bytes from /dev/urandom");
            break;
        }
        buffer += n;
        size -= (Py_ssize_t)n;
    }
    close(fd);
}

/* Read size bytes from /dev/urandom into buffer.
   Return 0 on success, raise an exception and return -1 on error. */
static int
dev_urandom_python(char *buffer, Py_ssize_t size)
{
    int fd;
    Py_ssize_t n;

    if (size <= 0)
        return 0;

    Py_BEGIN_ALLOW_THREADS
    fd = open("/dev/urandom", O_RDONLY);
    Py_END_ALLOW_THREADS
    if (fd < 0)
    {
        PyErr_SetString(PyExc_NotImplementedError,
                        "/dev/urandom (or equivalent) not found");
        return -1;
    }

    Py_BEGIN_ALLOW_THREADS
    do {
        do {
            n = read(fd, buffer, (size_t)size);
        } while (n < 0 && errno == EINTR);
        if (n <= 0)
            break;
        buffer += n;
        size -= (Py_ssize_t)n;
    } while (0 < size);
    Py_END_ALLOW_THREADS

    if (n <= 0)
    {
        /* stop on error or if read(size) returned 0 */
        if (n < 0)
            PyErr_SetFromErrno(PyExc_OSError);
        else
            PyErr_Format(PyExc_RuntimeError,
                         "Failed to read %zi bytes from /dev/urandom",
                         size);
        close(fd);
        return -1;
    }
    close(fd);
    return 0;
}
#endif /* !defined(MS_WINDOWS) && !defined(__VMS) */

/* Fill buffer with pseudo-random bytes generated by a linear congruent
   generator (LCG):

       x(n+1) = (x(n) * 214013 + 2531011) % 2^32

   Use bits 23..16 of x(n) to generate a byte. */
static void
lcg_urandom(unsigned int x0, unsigned char *buffer, size_t size)
{
    size_t index;
    unsigned int x;

    x = x0;
    for (index=0; index < size; index++) {
        x *= 214013;
        x += 2531011;
        /* modulo 2 ^ (8 * sizeof(int)) */
        buffer[index] = (x >> 16) & 0xff;
    }
}

/* Fill buffer with size pseudo-random bytes, not suitable for cryptographic
   use, from the operating random number generator (RNG).

   Return 0 on success, raise an exception and return -1 on error. */
int
_PyOS_URandom(void *buffer, Py_ssize_t size)
{
    if (size < 0) {
        PyErr_Format(PyExc_ValueError,
                     "negative argument not allowed");
        return -1;
    }
    if (size == 0)
        return 0;

#ifdef MS_WINDOWS
    return win32_urandom((unsigned char *)buffer, size, 1);
#else
# ifdef __VMS
    return vms_urandom((unsigned char *)buffer, size, 1);
# else
    return dev_urandom_python((char*)buffer, size);
# endif
#endif
}

void
_PyRandom_Init(void)
{
    char *env;
    void *secret = &_Py_HashSecret;
    Py_ssize_t secret_size = sizeof(_Py_HashSecret_t);

    if (_Py_HashSecret_Initialized)
        return;
    _Py_HashSecret_Initialized = 1;

    /*
      Hash randomization is enabled.  Generate a per-process secret,
      using PYTHONHASHSEED if provided.
    */

    env = Py_GETENV("PYTHONHASHSEED");
    if (env && *env != '\0' && strcmp(env, "random") != 0) {
        char *endptr = env;
        unsigned long seed;
        seed = strtoul(env, &endptr, 10);
        if (*endptr != '\0'
            || seed > 4294967295UL
            || (errno == ERANGE && seed == ULONG_MAX))
        {
            Py_FatalError("PYTHONHASHSEED must be \"random\" or an integer "
                          "in range [0; 4294967295]");
        }
        if (seed == 0) {
            /* disable the randomized hash */
            memset(secret, 0, secret_size);
        }
        else {
            lcg_urandom(seed, (unsigned char*)secret, secret_size);
        }
    }
    else {
#ifdef MS_WINDOWS
        (void)win32_urandom((unsigned char *)secret, secret_size, 0);
#else /* #ifdef MS_WINDOWS */
# ifdef __VMS
        vms_urandom((unsigned char *)secret, secret_size, 0);
# else
        dev_urandom_noraise((char*)secret, secret_size);
# endif
#endif
    }
}