1/***************************************************************************
2 *                                  _   _ ____  _
3 *  Project                     ___| | | |  _ \| |
4 *                             / __| | | | |_) | |
5 *                            | (__| |_| |  _ <| |___
6 *                             \___|\___/|_| \_\_____|
7 *
8 * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
9 *
10 * This software is licensed as described in the file COPYING, which
11 * you should have received as part of this distribution. The terms
12 * are also available at https://curl.haxx.se/docs/copyright.html.
13 *
14 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
15 * copies of the Software, and permit persons to whom the Software is
16 * furnished to do so, under the terms of the COPYING file.
17 *
18 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
19 * KIND, either express or implied.
20 *
21 ***************************************************************************/
22
23#include "curl_setup.h"
24
25#ifdef HAVE_FCNTL_H
26#include <fcntl.h>
27#endif
28
29#include <curl/curl.h>
30#include "vtls/vtls.h"
31#include "sendf.h"
32#include "rand.h"
33
34/* The last 3 #include files should be in this order */
35#include "curl_printf.h"
36#include "curl_memory.h"
37#include "memdebug.h"
38
39static CURLcode randit(struct Curl_easy *data, unsigned int *rnd)
40{
41  unsigned int r;
42  CURLcode result = CURLE_OK;
43  static unsigned int randseed;
44  static bool seeded = FALSE;
45
46#ifdef CURLDEBUG
47  char *force_entropy = getenv("CURL_ENTROPY");
48  if(force_entropy) {
49    if(!seeded) {
50      unsigned int seed = 0;
51      size_t elen = strlen(force_entropy);
52      size_t clen = sizeof(seed);
53      size_t min = elen < clen ? elen : clen;
54      memcpy((char *)&seed, force_entropy, min);
55      randseed = ntohl(seed);
56      seeded = TRUE;
57    }
58    else
59      randseed++;
60    *rnd = randseed;
61    return CURLE_OK;
62  }
63#endif
64
65  /* data may be NULL! */
66  result = Curl_ssl_random(data, (unsigned char *)rnd, sizeof(*rnd));
67  if(result != CURLE_NOT_BUILT_IN)
68    /* only if there is no random function in the TLS backend do the non crypto
69       version, otherwise return result */
70    return result;
71
72  /* ---- non-cryptographic version following ---- */
73
74#ifdef RANDOM_FILE
75  if(!seeded) {
76    /* if there's a random file to read a seed from, use it */
77    int fd = open(RANDOM_FILE, O_RDONLY);
78    if(fd > -1) {
79      /* read random data into the randseed variable */
80      ssize_t nread = read(fd, &randseed, sizeof(randseed));
81      if(nread == sizeof(randseed))
82        seeded = TRUE;
83      close(fd);
84    }
85  }
86#endif
87
88  if(!seeded) {
89    struct curltime now = Curl_now();
90    infof(data, "WARNING: Using weak random seed\n");
91    randseed += (unsigned int)now.tv_usec + (unsigned int)now.tv_sec;
92    randseed = randseed * 1103515245 + 12345;
93    randseed = randseed * 1103515245 + 12345;
94    randseed = randseed * 1103515245 + 12345;
95    seeded = TRUE;
96  }
97
98  /* Return an unsigned 32-bit pseudo-random number. */
99  r = randseed = randseed * 1103515245 + 12345;
100  *rnd = (r << 16) | ((r >> 16) & 0xFFFF);
101  return CURLE_OK;
102}
103
104/*
105 * Curl_rand() stores 'num' number of random unsigned integers in the buffer
106 * 'rndptr' points to.
107 *
108 * If libcurl is built without TLS support or with a TLS backend that lacks a
109 * proper random API (Gskit, PolarSSL or mbedTLS), this function will use
110 * "weak" random.
111 *
112 * When built *with* TLS support and a backend that offers strong random, it
113 * will return error if it cannot provide strong random values.
114 *
115 * NOTE: 'data' may be passed in as NULL when coming from external API without
116 * easy handle!
117 *
118 */
119
120CURLcode Curl_rand(struct Curl_easy *data, unsigned char *rnd, size_t num)
121{
122  CURLcode result = CURLE_BAD_FUNCTION_ARGUMENT;
123
124  DEBUGASSERT(num > 0);
125
126  while(num) {
127    unsigned int r;
128    size_t left = num < sizeof(unsigned int) ? num : sizeof(unsigned int);
129
130    result = randit(data, &r);
131    if(result)
132      return result;
133
134    while(left) {
135      *rnd++ = (unsigned char)(r & 0xFF);
136      r >>= 8;
137      --num;
138      --left;
139    }
140  }
141
142  return result;
143}
144
145/*
146 * Curl_rand_hex() fills the 'rnd' buffer with a given 'num' size with random
147 * hexadecimal digits PLUS a zero terminating byte. It must be an odd number
148 * size.
149 */
150
151CURLcode Curl_rand_hex(struct Curl_easy *data, unsigned char *rnd,
152                       size_t num)
153{
154  CURLcode result = CURLE_BAD_FUNCTION_ARGUMENT;
155  const char *hex = "0123456789abcdef";
156  unsigned char buffer[128];
157  unsigned char *bufp = buffer;
158  DEBUGASSERT(num > 1);
159
160#ifdef __clang_analyzer__
161  /* This silences a scan-build warning about accesssing this buffer with
162     uninitialized memory. */
163  memset(buffer, 0, sizeof(buffer));
164#endif
165
166  if((num/2 >= sizeof(buffer)) || !(num&1))
167    /* make sure it fits in the local buffer and that it is an odd number! */
168    return CURLE_BAD_FUNCTION_ARGUMENT;
169
170  num--; /* save one for zero termination */
171
172  result = Curl_rand(data, buffer, num/2);
173  if(result)
174    return result;
175
176  while(num) {
177    *rnd++ = hex[(*bufp & 0xF0)>>4];
178    *rnd++ = hex[*bufp & 0x0F];
179    bufp++;
180    num -= 2;
181  }
182  *rnd = 0;
183
184  return result;
185}
186