Commit 1f9dc86b authored by Bernd Edlinger's avatar Bernd Edlinger
Browse files

Change DH_generate_parameters back to order 2q subgroup 



For for G=2 and 5 DH_generate_parameters will continue to generate
the order 2q subgroup for compatibility with previous versions.

For G=3 DH_generate_parameters generates an order q subgroup, but it
will not pass the check in DH_check with previous OpenSSL versions.

Reviewed-by: default avatarMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9820)
parent 288241b6

CHANGES

+2 −2
Original line number Diff line number Diff line
@@ -50,8 +50,8 @@ 
     (CVE-2019-1552)

     [Richard Levitte]













  *) Changed DH parameters to generate the order q subgroup instead of 2q.













     Previously generated DH parameters are still accepted by DH_check













  *) Changed DH_check to accept parameters with order q and 2q subgroups.













     With order 2q subgroups the bit 0 of the private key is not secret















     but DH_generate_key works around that by clearing bit 0 of the















     private key for those. This avoids leaking bit 0 of the private key.















     [Bernd Edlinger]

































crypto/dh/dh_gen.c



+6
−2






























Original line number
Diff line number
Diff line








@@ -53,6 +53,10 @@ int DH_generate_parameters_ex(DH *ret, int prime_len, int generator,













 * for 2, p mod 24 == 23















 * for 3, p mod 12 == 11















 * for 5, p mod 60 == 59













 *













 * However for compatibilty with previous versions we use:













 * for 2, p mod 24 == 11













 * for 5, p mod 60 == 23















 */















static int dh_builtin_genparams(DH *ret, int prime_len, int generator,















                                BN_GENCB *cb)










@@ -83,13 +87,13 @@ static int dh_builtin_genparams(DH *ret, int prime_len, int generator,













    if (generator == DH_GENERATOR_2) {















        if (!BN_set_word(t1, 24))















            goto err;













        if (!BN_set_word(t2, 23))













        if (!BN_set_word(t2, 11))















            goto err;















        g = 2;















    } else if (generator == DH_GENERATOR_5) {















        if (!BN_set_word(t1, 60))















            goto err;













        if (!BN_set_word(t2, 59))













        if (!BN_set_word(t2, 23))















            goto err;















        g = 5;















    } else {