[Bug 1921518] Re: OpenSSL "double free" error

[Eyal Itkin]

Loading the configuration only once will resolve this issue, and is the
recommended code fix.

On top of this bug fix, and as mentioned above, we recommend that future
versions will incorporate an API change that will shift the ownership on
releasing the pointers to the engine that allocated them on the first
place. We understand this is an API change and that it isn't relevant in
the near future.

Regarding workarounds that will apply till OpenSSL fix their double
loading of the configuration, as I mentioned in #35, we are at a loss
here because OpenSSL is actively freeing the memory that the engine
allocated. The struct ENGINE is an OpenSSL implementation detail, and is
allocated in an OpenSSL function ENGINE_new(). I fail to see how a given
engine can add fields to it / save its own context on top of it.

1. The engine library could maintain some Data structure with all
"known" engine instances of itself, but OpenSSL guaranteed developers a
singleton invocation. This is a drastic implementation change on behalf
of the engine developers, and I doubt developers will go to this effort
when they know it is temporary until OpenSSL fixes their code and
restore back the singleton guarantee.

2. It is a bit trickier, because OpenSSL expect the memory to be
initialized using EVP_PKEY_meth_new() and then the pointer to be set
using EVP_PKEY_meth_set_derive(). Hence, they've taken the liberty to
invoke EVP_PKEY_meth_free() and directly free the instance that was
given to them. If all engine instances use the same static field, it
will get freed by OpenSSL. If there will be an instance per engine, it
throws us back to point (1) of maintaining a data structure of the
additional engine metadata per instance.

3. In our deployment environments any environment variable based hack is
out of the question.

As such, any temporary fix will be a hack, and will need to bypass the
break of the singleton engine guarantee that was given to engine
developers. Disabling the double parsing of the configuration, and
double load of the engine is the code fix that should be done, and it
should be done on OpenSSL's side.

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https://bugs.launchpad.net/bugs/1921518

Title:
  OpenSSL "double free" error

Status in openssl package in Ubuntu:
  Incomplete
Status in openssl source package in Focal:
  Incomplete

Bug description:
  "double free" error is seen when using curl utility. Error is from
  libcrypto.so which is part of the OpenSSL package. This happens only
  when OpenSSL is configured to use a dynamic engine.

  OpenSSL version is 1.1.1f

  The issue is not encountered if
  http://www.openssl.org/source/openssl-1.1.1f.tar.gz is used instead.

  
  OpenSSL can be configured to use a dynamic engine by editing the default openssl config file which is located at '/etc/ssl/openssl.cnf' on Ubuntu systems.

  On Bluefield systems, config diff to enable PKA dynamic engine, is as
  below:

  +openssl_conf = conf_section
  +
   # Extra OBJECT IDENTIFIER info:
   #oid_file              = $ENV::HOME/.oid
   oid_section            = new_oids
   
  +[ conf_section ]
  +engines = engine_section
  +
  +[ engine_section ]
  +bf = bf_section
  +
  +[ bf_section ]
  +engine_id=pka
  +dynamic_path=/usr/lib/aarch64-linux-gnu/engines-1.1/pka.so
  +init=0
  +

  engine_id above refers to dynamic engine name/identifier.
  dynamic_path points to the .so file for the dynamic engine.

  # curl -O https://tpo.pe/pathogen.vim

  double free or corruption (out)

  Aborted (core dumped)

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