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More changes coming out of the bignum auditing. BN_CTX_get() should ideally

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return a "zero" bignum as BN_new() does - so reset 'top'. During
BN_CTX_end(), released bignums should be consistent so enforce this in
debug builds. Also, reduce the number of wasted BN_clear_free() calls from
BN_CTX_end() (typically by 75% or so).

Submitted by: Nils Larsch
Reviewed by: Geoff Thorpe, Ulf Möller
This commit is contained in:
Geoff Thorpe 2004-03-09 03:47:35 +00:00
parent a4e3150f00
commit e7716b7a19
1 changed files with 6 additions and 12 deletions
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16
crypto/bn/bn_ctx.c
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@ -123,6 +123,7 @@ void BN_CTX_free(BN_CTX *ctx)
for (i=0; i < BN_CTX_NUM; i++) { for (i=0; i < BN_CTX_NUM; i++) {
bn_check_top(&(ctx->bn[i])); bn_check_top(&(ctx->bn[i]));
if (ctx->bn[i].d)
BN_clear_free(&(ctx->bn[i])); BN_clear_free(&(ctx->bn[i]));
} }
if (ctx->flags & BN_FLG_MALLOCED) if (ctx->flags & BN_FLG_MALLOCED)
@ -154,7 +155,8 @@ BIGNUM *BN_CTX_get(BN_CTX *ctx)
} }
return NULL; return NULL;
} }
bn_check_top(&(ctx->bn[ctx->tos])); /* always return a 'zeroed' bignum */
ctx->bn[ctx->tos].top = 0;
return (&(ctx->bn[ctx->tos++])); return (&(ctx->bn[ctx->tos++]));
} }
@ -170,19 +172,11 @@ void BN_CTX_end(BN_CTX *ctx)
ctx->too_many = 0; ctx->too_many = 0;
ctx->depth--; ctx->depth--;
/* It appears some "scrapbook" uses of BN_CTX result in BIGNUMs being
* left in an inconsistent state when they are released (eg. BN_div).
* These can trip us up when they get reused, so the safest fix is to
* make sure the BIGNUMs are made sane when the context usage is
* releasing them. */
if (ctx->depth < BN_CTX_NUM_POS) if (ctx->depth < BN_CTX_NUM_POS)
#if 0 #ifndef BN_DEBUG
ctx->tos = ctx->pos[ctx->depth]; ctx->tos = ctx->pos[ctx->depth];
#else #else
{
while(ctx->tos > ctx->pos[ctx->depth]) while(ctx->tos > ctx->pos[ctx->depth])
/* This ensures the BIGNUM is sane(r) for reuse. */ bn_check_top(&ctx->bn[--(ctx->tos)]);
ctx->bn[--(ctx->tos)].top = 0;
}
#endif #endif
} }