[openssl-dev] [openssl.org #4160] Candidate bug, malloc failure related issues in s3_enc.c, hm_pmeth.c

[Kurt Roeckx via RT]

On Sun, Nov 29, 2015 at 11:09:35AM +0000, Trevor Larock via RT wrote:
> Hi folks,
> 
> Can I ask about malloc failure handling issues, seems affecting OpenSSL 1.0.1p and 1.0.2d,
> 
> 1. In s3_enc.c::ssl3_digest_cached_records, we have the below code.
> 
>     s->s3->handshake_dgst =
>         OPENSSL_malloc(SSL_MAX_DIGEST * sizeof(EVP_MD_CTX *));
>     memset(s->s3->handshake_dgst, 0, SSL_MAX_DIGEST * sizeof(EVP_MD_CTX *));
> 
> We are not checking for the return value of the malloc resulting in a straight null dereference in the memset.

That seems to be fixed in the master branch.

> 2. In hm_pmeth.c::pkey_hmac_cleanup
> 
>     HMAC_PKEY_CTX *hctx = ctx->data;
>     HMAC_CTX_cleanup(&hctx->ctx);
> 
> Using hctx when it can be NULL. We could have failed to allocate ctx->data in int_ctx_new which calls pmeth->init (alloc can return error here).

So when pmeth->init() fails it calls EVP_PKEY_CTX_free(), which
calls ctx->pmeth->cleanup().

I'm guessing there are other cleanup / free functions that don't
really expect to get called when init / new failed.  At least
ossl_hmac_cleanup() looks to have the same problem, while things
like pkey_ec_cleanup(), pkey_dh_cleanup() and pkey_rsa_cleanup()
look good.


Kurt