[openssl-users] Multiple client connection to Nginx server

Jakob Bohm jb-openssl at wisemo.com
Wed Dec 12 14:25:57 UTC 2018

On 12/12/2018 12:54, ASHIQUE CK wrote:
> Hi,
> Any help on this ?
> On Wed, Dec 12, 2018 at 3:03 PM ASHIQUE CK <ckashiquekvk at gmail.com 
> <mailto:ckashiquekvk at gmail.com>> wrote:
>     Hi,
>     We are using a Crypto Accelerator Engine to offload AESGCM and RSA
>     parameters. Trying to connect multiple clients simultaneously with
>     a single Nginx server, which is using this accelerator.  The Key
>     and IV is passing only at handshake, and after handshake this set
>     of key and IV is using for all encryption and decryption. So at
>     Engine side, we are storing this Key and IV to a buffer and while
>     encrypting/decrypting , this Key and IV is used from this buffer.
>     But, while multiple client connects, the last saved Key/IV is
>     getting for all clients.
>             So, is there any way to get a unique ID foer each client
>     connection ?
The following assumes that the accelerator is accessed using an
OpenSSL "engine" plugin, if instead you are inserting code in NGINX
to hand over the complete SSL/TLS record processing to the hardware,
then a different approach is needed.

OpenSSL Crypto Engines are not limited to SSL/TLS but can be used
for other tasks using the OpenSSL libcrypto library.

Thus the way this works is that the SSL/TLS requests an EVP "handle"
for each key that it wants to use, this handle then maps (indirectly)
to a structure passed to the engine, which is unique to each key.

A correctly implemented engine is supposed to use that structure to
tell the difference between different keys stored in the actual

For the case of GCM key/IV pairs, it may be that in some situations
OpenSSL requests more than one EVP key instance for the same key,
typically to allow each to have its own independent state (for GCM,
this is the counter, for CBC it would be the IV chaining from block
to block).  The simple solution is to just treat them as different
keys, but if this uses too many hardware key storage locations, an
engine may use some way to recognize the reused key, share the
hardware object and keep count of how many "handles" point to that


Jakob Bohm, CIO, Partner, WiseMo A/S.  https://www.wisemo.com
Transformervej 29, 2860 Søborg, Denmark.  Direct +45 31 13 16 10
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