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List:       openssl-dev
Subject:    Re: bug in EVP_MD_CTX_copy()
From:       Dr S N Henson <drh () celocom ! com>
Date:       2001-04-24 11:29:27
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T Bharath wrote:
> 
> Steve i still do not understand that
> Here ctx.digest does not have any memory and when the call
> memcpy((char *)out,(char *)in,in->digest->ctx_size);
> is made,in my case you are copying 96 bytes to ctx.digest and in the
> process overwriting someotherdata.Isnt that true.


No it isn't. The structures are being copied. The actual pointer
ctx->digest is being changed *not* the (invalid) data it points to. So
what you are effectively doing is (among other things):

out->digest = in->digest;

and the in->digest pointer points to a valid EVP_MD structure.

Steve.
-- 
Dr Stephen N. Henson.   http://www.drh-consultancy.demon.co.uk/
Personal Email: shenson@drh-consultancy.demon.co.uk 
Senior crypto engineer, Celo Communications: http://www.celocom.com/
Core developer of the   OpenSSL project: http://www.openssl.org/
Business Email: drh@celocom.com PGP key: via homepage.

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