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openssl: improve fallback seed of PRNG with a time based hash

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Fixes #1620
This commit is contained in:
dmitrykos 2017-06-27 20:56:12 +03:00 committed by Daniel Stenberg
parent f8f040e659
commit 192877058e
1 changed files with 26 additions and 17 deletions
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43
lib/vtls/openssl.c
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@ -236,7 +236,6 @@ static CURLcode Curl_ossl_seed(struct Curl_easy *data)
/* we have the "SSL is seeded" boolean static to prevent multiple /* we have the "SSL is seeded" boolean static to prevent multiple
time-consuming seedings in vain */ time-consuming seedings in vain */
static bool ssl_seeded = FALSE; static bool ssl_seeded = FALSE;
int nread=0;
char fname[256]; char fname[256];
if(ssl_seeded) if(ssl_seeded)
@ -256,12 +255,12 @@ static CURLcode Curl_ossl_seed(struct Curl_easy *data)
#endif #endif
{ {
/* let the option override the define */ /* let the option override the define */
nread += RAND_load_file((data->set.str[STRING_SSL_RANDOM_FILE]? RAND_load_file((data->set.str[STRING_SSL_RANDOM_FILE]?
data->set.str[STRING_SSL_RANDOM_FILE]: data->set.str[STRING_SSL_RANDOM_FILE]:
RANDOM_FILE), RANDOM_FILE),
RAND_LOAD_LENGTH); RAND_LOAD_LENGTH);
if(rand_enough()) if(rand_enough())
return nread; return CURLE_OK;
} }
#if defined(HAVE_RAND_EGD) #if defined(HAVE_RAND_EGD)
@ -279,21 +278,30 @@ static CURLcode Curl_ossl_seed(struct Curl_easy *data)
int ret = RAND_egd(data->set.str[STRING_SSL_EGDSOCKET]? int ret = RAND_egd(data->set.str[STRING_SSL_EGDSOCKET]?
data->set.str[STRING_SSL_EGDSOCKET]:EGD_SOCKET); data->set.str[STRING_SSL_EGDSOCKET]:EGD_SOCKET);
if(-1 != ret) { if(-1 != ret) {
nread += ret;
if(rand_enough()) if(rand_enough())
return nread; return CURLE_OK;
} }
} }
#endif #endif
/* If we get here, it means we need to seed the PRNG using a "silly" /* fallback to a custom seeding of the PRNG using a hash based on a current
approach! */ time */
do { do {
unsigned char randb[64]; unsigned char randb[64];
int len = sizeof(randb); size_t len = sizeof(randb);
if(!RAND_bytes(randb, len)) size_t i, i_max;
break; for(i = 0, i_max = len / sizeof(struct timeval); i < i_max; ++i) {
RAND_add(randb, len, (len >> 1)); struct timeval tv = curlx_tvnow();
Curl_wait_ms(1);
tv.tv_sec *= i + 1;
tv.tv_usec *= i + 2;
tv.tv_sec ^= ((curlx_tvnow().tv_sec + curlx_tvnow().tv_usec) *
(i + 3)) << 8;
tv.tv_usec ^= ((curlx_tvnow().tv_sec + curlx_tvnow().tv_usec) *
(i + 4)) << 16;
memcpy(&randb[i * sizeof(struct timeval)], &tv, sizeof(struct timeval));
}
RAND_add(randb, (int)len, (double)len/2);
} while(!rand_enough()); } while(!rand_enough());
/* generates a default path for the random seed file */ /* generates a default path for the random seed file */
@ -301,13 +309,14 @@ static CURLcode Curl_ossl_seed(struct Curl_easy *data)
RAND_file_name(fname, sizeof(fname)); RAND_file_name(fname, sizeof(fname));
if(fname[0]) { if(fname[0]) {
/* we got a file name to try */ /* we got a file name to try */
nread += RAND_load_file(fname, RAND_LOAD_LENGTH); RAND_load_file(fname, RAND_LOAD_LENGTH);
if(rand_enough()) if(rand_enough())
return nread; return CURLE_OK;
} }
infof(data, "libcurl is now using a weak random seed!\n"); infof(data, "libcurl is now using a weak random seed!\n");
return CURLE_SSL_CONNECT_ERROR; /* confusing error code */ return (rand_enough() ? CURLE_OK :
CURLE_SSL_CONNECT_ERROR /* confusing error code */);
} }
#ifndef SSL_FILETYPE_ENGINE #ifndef SSL_FILETYPE_ENGINE