[openssl-dev] [openssl.org #4185] Bug in EVP_MD_CTX_copy_ex's malloc failure handling

[David Benjamin via RT]

On Thu, Dec 17, 2015 at 2:43 PM Kurt Roeckx via RT <rt at openssl.org> wrote:

> On Wed, Dec 16, 2015 at 11:34:56PM +0000, David Benjamin via RT wrote:
> > EVP_MD_CTX_copy_ex is implemented with memcpy, followed by manually
> fixing
> > up |out->pctx| and |out->md_data|.
> >
> >
> https://git.openssl.org/gitweb/?p=openssl.git;a=blob;f=crypto/evp/digest.c;h=5da0e01039a6da039942db9f1bf8b70753f509f2;hb=HEAD#l292
> >
> > If allocating |out->md_data| fails, then both |out->pctx| and |in->pctx|
> > may point to the same EVP_PKEY_CTX and freeing |out| will cause problems.
> >
> > We fixed this by not using memcpy.
> >
> https://boringssl.googlesource.com/boringssl/+/306ece31bcaaed49e0240a2e5555f8901ebb2d45%5E%21/crypto/digest/digest.c
>
> This patch won't apply as is since we have more fields (engine,
> flags).
>
> We also don't have pctx_ops, but have update instead, but already
> seem to copy that anyway.
>

Right, we've diverged enough at this point that patches not applying as-is
is the norm. :-) That was meant as a reference, but someone will need to do
the equivalent change in OpenSSL if you all like the approach.

David