Commit 5f2d9c4d authored by Dr. Stephen Henson's avatar Dr. Stephen Henson
Browse files

Support constant BN for DH parameters 



If BN_FLG_STATIC_DATA is set don't cleanse a->d as it will reside
in read only memory. If BN_FLG_MALLOCED is not set don't modify the
BIGNUM at all.

This change applies to BN_clear_free() and BN_free(). Now the BIGNUM
structure is opaque applications cannot create a BIGNUM structure
without BN_FLG_MALLOCED being set so they are unaffected.

Update internal DH routines so they only copy pointers for read only
parameters.

Reviewed-by: default avatarAndy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4485)
parent 8e826a33

crypto/bn/bn_lib.c

+5 −16
Original line number Diff line number Diff line
@@ -179,37 +179,26 @@ static void bn_free_d(BIGNUM *a) 


void BN_clear_free(BIGNUM *a)

{

    int i;



    if (a == NULL)

        return;

    bn_check_top(a);

    if (a->d != NULL) {

    if (a->d != NULL && !BN_get_flags(a, BN_FLG_STATIC_DATA)) {

        OPENSSL_cleanse(a->d, a->dmax * sizeof(a->d[0]));

        if (!BN_get_flags(a, BN_FLG_STATIC_DATA))

        bn_free_d(a);

    }

    i = BN_get_flags(a, BN_FLG_MALLOCED);

    if (BN_get_flags(a, BN_FLG_MALLOCED)) {

        OPENSSL_cleanse(a, sizeof(*a));

    if (i)

        OPENSSL_free(a);

    }

}



void BN_free(BIGNUM *a)

{

    if (a == NULL)

        return;

    bn_check_top(a);

    if (!BN_get_flags(a, BN_FLG_STATIC_DATA))

        bn_free_d(a);

    if (a->flags & BN_FLG_MALLOCED)

        OPENSSL_free(a);

    else {

#if OPENSSL_API_COMPAT < 0x00908000L

        a->flags |= BN_FLG_FREE;

#endif

        a->d = NULL;

    }

}



void bn_init(BIGNUM *a)

crypto/dh/dh_ameth.c

+12 −6
Original line number Diff line number Diff line
@@ -374,13 +374,19 @@ static int dh_cmp_parameters(const EVP_PKEY *a, const EVP_PKEY *b) 
static int int_dh_bn_cpy(BIGNUM **dst, const BIGNUM *src)

{

    BIGNUM *a;

    if (src) {

        a = BN_dup(src);

        if (!a)

            return 0;

    } else



    /*

     * If source is read only just copy the pointer, so

     * we don't have to reallocate it.

     */

    if (src == NULL)

        a = NULL;

    BN_free(*dst);

    else if (BN_get_flags(src, BN_FLG_STATIC_DATA)

                && !BN_get_flags(src, BN_FLG_MALLOCED))

        a = (BIGNUM *)src;

    else if ((a = BN_dup(src)) == NULL)

        return 0;

    BN_clear_free(*dst);

    *dst = a;

    return 1;

}