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Make sure that the stored DH prime is safe to use.

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This commit is contained in:
George Kadianakis 2011-11-25 00:33:40 +01:00
parent 94076d9e3b
commit 5f3f41c234
1 changed files with 34 additions and 4 deletions
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38
src/common/crypto.c
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@ -1832,7 +1832,7 @@ crypto_generate_dynamic_prime(void)
tor_assert(dh_parameters);
r = DH_check(dh_parameters, &dh_codes);
tor_assert(r);
tor_assert(r && !dh_codes);
BN_copy(dynamic_prime, dh_parameters->p);
tor_assert(dynamic_prime);
@ -1855,10 +1855,12 @@ crypto_store_dynamic_prime(const char *fname)
{
FILE *fp = NULL;
int retval = -1;
file_status_t fname_status = file_status(fname);
file_status_t fname_status;
tor_assert(fname);
fname_status = file_status(fname);
if (fname_status == FN_FILE) {
/* If the fname is a file, then the dynamic prime is already stored. */
retval = 0;
@ -1896,6 +1898,8 @@ crypto_get_stored_dynamic_prime(const char *fname)
{
int retval;
char *contents = NULL;
DH *dh = NULL;
int dh_codes;
BIGNUM *dynamic_prime = BN_new();
tor_assert(fname);
@ -1909,11 +1913,35 @@ crypto_get_stored_dynamic_prime(const char *fname)
retval = BN_hex2bn(&dynamic_prime, contents);
if (!retval) {
log_notice(LD_GENERAL, "Could not understand the dynamic prime "
"format in '%s'", fname);
log_warn(LD_GENERAL, "Could not understand the dynamic prime "
"format in '%s'", fname);
goto err;
}
{ /* validate the stored prime */
dh = DH_new();
if (!dh)
goto err;
dh->p = BN_dup(dynamic_prime);
dh->g = BN_new();
BN_set_word(dh->g, DH_GENERATOR);
retval = DH_check(dh, &dh_codes);
if (!retval || dh_codes) {
log_warn(LD_GENERAL, "Stored dynamic DH prime is not a safe prime.");
goto err;
}
retval = DH_size(dh);
if (retval < DH_BYTES) {
log_warn(LD_GENERAL, "Stored dynamic DH prime is smaller "
"than '%d' bits.", DH_BYTES*8);
goto err;
}
}
{ /* log the dynamic prime: */
char *s = BN_bn2hex(dynamic_prime);
tor_assert(s);
@ -1931,6 +1959,8 @@ crypto_get_stored_dynamic_prime(const char *fname)
done:
tor_free(contents);
if (dh)
DH_free(dh);
return dynamic_prime;
}