1/***************************************************************************
2 * _ _ ____ _
3 * Project ___| | | | _ \| |
4 * / __| | | | |_) | |
5 * | (__| |_| | _ <| |___
6 * \___|\___/|_| \_\_____|
7 *
8 * Copyright (C) 1998 - 2021, 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.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");
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 or mbedTLS), this function will use "weak" random.
110 *
111 * When built *with* TLS support and a backend that offers strong random, it
112 * will return error if it cannot provide strong random values.
113 *
114 * NOTE: 'data' may be passed in as NULL when coming from external API without
115 * easy handle!
116 *
117 */
118
119CURLcode Curl_rand(struct Curl_easy *data, unsigned char *rnd, size_t num)
120{
121 CURLcode result = CURLE_BAD_FUNCTION_ARGUMENT;
122
123 DEBUGASSERT(num > 0);
124
125 while(num) {
126 unsigned int r;
127 size_t left = num < sizeof(unsigned int) ? num : sizeof(unsigned int);
128
129 result = randit(data, &r);
130 if(result)
131 return result;
132
133 while(left) {
134 *rnd++ = (unsigned char)(r & 0xFF);
135 r >>= 8;
136 --num;
137 --left;
138 }
139 }
140
141 return result;
142}
143
144/*
145 * Curl_rand_hex() fills the 'rnd' buffer with a given 'num' size with random
146 * hexadecimal digits PLUS a zero terminating byte. It must be an odd number
147 * size.
148 */
149
150CURLcode Curl_rand_hex(struct Curl_easy *data, unsigned char *rnd,
151 size_t num)
152{
153 CURLcode result = CURLE_BAD_FUNCTION_ARGUMENT;
154 const char *hex = "0123456789abcdef";
155 unsigned char buffer[128];
156 unsigned char *bufp = buffer;
157 DEBUGASSERT(num > 1);
158
159#ifdef __clang_analyzer__
160 /* This silences a scan-build warning about accessing this buffer with
161 uninitialized memory. */
162 memset(buffer, 0, sizeof(buffer));
163#endif
164
165 if((num/2 >= sizeof(buffer)) || !(num&1))
166 /* make sure it fits in the local buffer and that it is an odd number! */
167 return CURLE_BAD_FUNCTION_ARGUMENT;
168
169 num--; /* save one for zero termination */
170
171 result = Curl_rand(data, buffer, num/2);
172 if(result)
173 return result;
174
175 while(num) {
176 /* clang-tidy warns on this line without this comment: */
177 /* NOLINTNEXTLINE(clang-analyzer-core.UndefinedBinaryOperatorResult) */
178 *rnd++ = hex[(*bufp & 0xF0)>>4];
179 *rnd++ = hex[*bufp & 0x0F];
180 bufp++;
181 num -= 2;
182 }
183 *rnd = 0;
184
185 return result;
186}
187