From 3cc94d964548404c06fb919dc4cd8e2029b1d1fb Mon Sep 17 00:00:00 2001 From: tb Date: Thu, 7 Apr 2022 17:37:25 +0000 Subject: [PATCH] Avoid infinite loop for custom curves of order 1 If a private key encoded with EC parameters happens to have order 1 and is used for ECDSA signatures, this causes an infinite loop since a random integer x in the interval [0,1) will be 0, so do ... while (x == 0); will loop indefinitely. Found and reported with a reproducer by Hanno Boeck. Helpful comments and analysis from David Benjamin. ok beck jsing --- lib/libcrypto/ec/ec_lib.c | 6 +++--- lib/libcrypto/ecdsa/ecs_ossl.c | 7 ++++++- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/lib/libcrypto/ec/ec_lib.c b/lib/libcrypto/ec/ec_lib.c index 888f1edfcf2..4ec17d5d5d1 100644 --- a/lib/libcrypto/ec/ec_lib.c +++ b/lib/libcrypto/ec/ec_lib.c @@ -1,4 +1,4 @@ -/* $OpenBSD: ec_lib.c,v 1.44 2022/03/29 14:03:12 tb Exp $ */ +/* $OpenBSD: ec_lib.c,v 1.45 2022/04/07 17:37:25 tb Exp $ */ /* * Originally written by Bodo Moeller for the OpenSSL project. */ @@ -348,10 +348,10 @@ EC_GROUP_set_generator(EC_GROUP *group, const EC_POINT *generator, } /* - * Require order >= 1 and enforce an upper bound of at most one bit more + * Require order > 1 and enforce an upper bound of at most one bit more * than the field cardinality due to Hasse's theorem. */ - if (order == NULL || BN_is_zero(order) || BN_is_negative(order) || + if (order == NULL || BN_cmp(order, BN_value_one()) <= 0 || BN_num_bits(order) > BN_num_bits(&group->field) + 1) { ECerror(EC_R_INVALID_GROUP_ORDER); return 0; diff --git a/lib/libcrypto/ecdsa/ecs_ossl.c b/lib/libcrypto/ecdsa/ecs_ossl.c index 2429e36b59e..0203b01bb55 100644 --- a/lib/libcrypto/ecdsa/ecs_ossl.c +++ b/lib/libcrypto/ecdsa/ecs_ossl.c @@ -1,4 +1,4 @@ -/* $OpenBSD: ecs_ossl.c,v 1.23 2022/01/20 11:03:48 inoguchi Exp $ */ +/* $OpenBSD: ecs_ossl.c,v 1.24 2022/04/07 17:37:25 tb Exp $ */ /* * Written by Nils Larsch for the OpenSSL project */ @@ -163,6 +163,11 @@ ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp) goto err; } + if (BN_cmp(order, BN_value_one()) <= 0) { + ECDSAerror(EC_R_INVALID_GROUP_ORDER); + goto err; + } + /* Preallocate space. */ order_bits = BN_num_bits(order); if (!BN_set_bit(k, order_bits) || -- 2.20.1