commit 5f3f41c23412e149add77a30e82431eb018cd376 Author: George Kadianakis desnacked@gmail.com Date: Fri Nov 25 00:33:40 2011 +0100

Make sure that the stored DH prime is safe to use. --- src/common/crypto.c | 38 ++++++++++++++++++++++++++++++++++---- 1 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/src/common/crypto.c b/src/common/crypto.c index c6285e5..83f56a5 100644 --- a/src/common/crypto.c +++ b/src/common/crypto.c @@ -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; }