FFmpeg: libavutil/random_seed.c Source File

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libavutil

random_seed.c

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1 /*

3 *

4 * This file is part of FFmpeg.

5 *

6 * FFmpeg is free software; you can redistribute it and/or

7 * modify it under the terms of the GNU Lesser General Public

8 * License as published by the Free Software Foundation; either

9 * version 2.1 of the License, or (at your option) any later version.

10 *

11 * FFmpeg is distributed in the hope that it will be useful,

12 * but WITHOUT ANY WARRANTY; without even the implied warranty of

13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

14 * Lesser General Public License for more details.

15 *

16 * You should have received a copy of the GNU Lesser General Public

17 * License along with FFmpeg; if not, write to the Free Software

18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

19 */

21 #include "config.h"

23 #if HAVE_UNISTD_H

24 #include <unistd.h>

25 #endif

26 #if HAVE_CRYPTGENRANDOM

27 #include <windows.h>

28 #include <wincrypt.h>

29 #endif

30 #include <fcntl.h>

31 #include <math.h>

32 #include <time.h>

33 #include <string.h>

34 #include "avassert.h"

35 #include "internal.h"

36 #include "timer.h"

37 #include "random_seed.h"

38 #include "sha.h"

39 #include "intreadwrite.h"

41 #ifndef TEST

42 #define TEST 0

43 #endif

45 static int read_random(uint32_t *dst, const char *file)

46 {

47 #if HAVE_UNISTD_H

48 int fd = avpriv_open(file, O_RDONLY);

49 int err = -1;

51 if (fd == -1)

52 return -1;

53 err = read(fd, dst, sizeof(*dst));

54 close(fd);

56 return err;

57 #else

58 return -1;

59 #endif

60 }

62 static uint32_t get_generic_seed(void)

63 {

64 uint8_t tmp[120];

65 struct AVSHA *sha = (void*)tmp;

66 clock_t last_t = 0;

67 static uint64_t i = 0;

68 static uint32_t buffer[512] = {0};

69 unsigned char digest[20];

70 uint64_t last_i = i;

72 av_assert0(sizeof(tmp) >= av_sha_size);

74 if(TEST){

75 memset(buffer, 0, sizeof(buffer));

76 last_i = i = 0;

77 }else{

78 #ifdef AV_READ_TIME

79 buffer[13] ^= AV_READ_TIME();

80 buffer[41] ^= AV_READ_TIME()>>32;

81 #endif

82 }

84 for (;;) {

85 clock_t t = clock();

87 if(last_t == t){

88 buffer[i&511]++;

89 }else{

90 buffer[++i&511]+= (t-last_t) % 3294638521U;

91 if(last_i && i-last_i > 4 || i-last_i > 64 || TEST && i-last_i > 8)

92 break;

93 }

94 last_t = t;

95 }

97 if(TEST)

98 buffer[0] = buffer[1] = 0;

100 av_sha_init(sha, 160);

101 av_sha_update(sha, (uint8_t*)buffer, sizeof(buffer));

102 av_sha_final(sha, digest);

103 return AV_RB32(digest) + AV_RB32(digest+16);

104 }

105

106 uint32_t av_get_random_seed(void)

107 {

108 uint32_t seed;

109

110 #if HAVE_CRYPTGENRANDOM

111 HCRYPTPROV provider;

112 if (CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL,

113 CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) {

114 BOOL ret = CryptGenRandom(provider, sizeof(seed), (PBYTE) &seed);

115 CryptReleaseContext(provider, 0);

116 if (ret)

117 return seed;

118 }

119 #endif

120

121 if (read_random(&seed, "/dev/urandom") == sizeof(seed))

122 return seed;

123 if (read_random(&seed, "/dev/random") == sizeof(seed))

124 return seed;

125 return get_generic_seed();

126 }

127

128 #if TEST

129 #undef printf

130 #define N 256

131 #include <stdio.h>

132

133 int main(void)

134 {

135 int i, j, retry;

136 uint32_t seeds[N];

137

138 for (retry=0; retry<3; retry++){

139 for (i=0; i<N; i++){

140 seeds[i] = av_get_random_seed();

141 for (j=0; j<i; j++)

142 if (seeds[j] == seeds[i])

143 goto retry;

144 }

145 printf("seeds OK\n");

146 return 0;

147 retry:;

148 }

149 printf("FAIL at %d with %X\n", j, seeds[j]);

150 return 1;

151 }

152 #endif

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