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_IO_H

27 #include <io.h>

28 #endif

29 #if HAVE_CRYPTGENRANDOM

30 #include <windows.h>

31 #include <wincrypt.h>

32 #endif

33 #include <fcntl.h>

34 #include <math.h>

35 #include <time.h>

36 #include <string.h>

37 #include "avassert.h"

38 #include "internal.h"

39 #include "intreadwrite.h"

40 #include "timer.h"

41 #include "random_seed.h"

42 #include "sha.h"

44 #ifndef TEST

45 #define TEST 0

46 #endif

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

49 {

50 #if HAVE_UNISTD_H

51 int fd = avpriv_open(file, O_RDONLY);

52 int err = -1;

54 if (fd == -1)

55 return -1;

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

57 close(fd);

59 return err;

60 #else

61 return -1;

62 #endif

63 }

65 static uint32_t get_generic_seed(void)

66 {

67 uint8_t tmp[120];

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

69 clock_t last_t = 0;

70 static uint64_t i = 0;

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

72 unsigned char digest[20];

73 uint64_t last_i = i;

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

77 if(TEST){

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

79 last_i = i = 0;

80 }else{

81 #ifdef AV_READ_TIME

82 buffer[13] ^= AV_READ_TIME();

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

84 #endif

85 }

87 for (;;) {

88 clock_t t = clock();

90 if (last_t == t) {

91 buffer[i & 511]++;

92 } else {

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

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

95 break;

96 }

97 last_t = t;

98 }

100 if(TEST)

101 buffer[0] = buffer[1] = 0;

102

103 av_sha_init(sha, 160);

104 av_sha_update(sha, (const uint8_t *)buffer, sizeof(buffer));

105 av_sha_final(sha, digest);

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

107 }

108

109 uint32_t av_get_random_seed(void)

110 {

111 uint32_t seed;

112

113 #if HAVE_CRYPTGENRANDOM

114 HCRYPTPROV provider;

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

116 CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) {

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

118 CryptReleaseContext(provider, 0);

119 if (ret)

120 return seed;

121 }

122 #endif

123

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

125 return seed;

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

127 return seed;

128 return get_generic_seed();

129 }

130

131 #if TEST

132 #undef printf

133 #define N 256

134 #include <stdio.h>

135

136 int main(void)

137 {

138 int i, j, retry;

139 uint32_t seeds[N];

140

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

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

143 seeds[i] = av_get_random_seed();

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

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

146 goto retry;

147 }

148 printf("seeds OK\n");

149 return 0;

150 retry:;

151 }

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

153 return 1;

154 }

155 #endif

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