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Remove superfluous NULL checks. Add Andy's BN_FLG comment.

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Reviewed-by: Andy Polyakov <appro@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6009)
This commit is contained in:
Billy Brumley 2018-04-23 14:34:11 +03:00 committed by Matt Caswell
parent 736b31e5ea
commit 39df51522b
2 changed files with 20 additions and 10 deletions
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25
crypto/bn/bn_lib.c
View File

@ -743,12 +743,27 @@ void BN_consttime_swap(BN_ULONG condition, BIGNUM *a, BIGNUM *b, int nwords)
a->neg ^= t;
b->neg ^= t;
/*
* cannot just arbitrarily swap flags.
* The way a->d is allocated etc.
* BN_FLG_MALLOCED, BN_FLG_STATIC_DATA, ...
/*-
* Idea behind BN_FLG_STATIC_DATA is actually to
* indicate that data may not be written to.
* Intention is actually to treat it as it's
* read-only data, and some (if not most) of it does
* reside in read-only segment. In other words
* observation of BN_FLG_STATIC_DATA in
* BN_consttime_swap should be treated as fatal
* condition. It would either cause SEGV or
* effectively cause data corruption.
* BN_FLG_MALLOCED refers to BN structure itself,
* and hence must be preserved. Remaining flags are
* BN_FLG_CONSTIME and BN_FLG_SECURE. Latter must be
* preserved, because it determines how x->d was
* allocated and hence how to free it. This leaves
* BN_FLG_CONSTTIME that one can do something about.
* To summarize it's sufficient to mask and swap
* BN_FLG_CONSTTIME alone. BN_FLG_STATIC_DATA should
* be treated as fatal.
*/
t = (a->flags ^ b->flags) & condition & BN_FLG_CONSTTIME;
t = ((a->flags ^ b->flags) & BN_FLG_CONSTTIME) & condition;
a->flags ^= t;
b->flags ^= t;

5
crypto/ec/ec_mult.c
View File

@ -142,9 +142,6 @@ static int ec_mul_consttime(const EC_GROUP *group, EC_POINT *r,
if (ctx == NULL && (ctx = new_ctx = BN_CTX_secure_new()) == NULL)
goto err;
if ((group->order == NULL) || (group->field == NULL))
goto err;
order_bits = BN_num_bits(group->order);
s = EC_POINT_new(group);
@ -152,8 +149,6 @@ static int ec_mul_consttime(const EC_GROUP *group, EC_POINT *r,
goto err;
if (point == NULL) {
if (group->generator == NULL)
goto err;
if (!EC_POINT_copy(s, group->generator))
goto err;
} else {