[OpenSIPS-Devel] [OpenSIPS/opensips] db899f: stir_shaken: Fix heap corruption due to X509_STORE...

[Liviu Chircu]

  Branch: refs/heads/master
  Home:   https://github.com/OpenSIPS/opensips
  Commit: db899f6df1110463935ce57745f82294a55f6f7a
      https://github.com/OpenSIPS/opensips/commit/db899f6df1110463935ce57745f82294a55f6f7a
  Author: Liviu Chircu <liviu at opensips.org>
  Date:   2021-04-14 (Wed, 14 Apr 2021)

  Changed paths:
    M modules/stir_shaken/stir_shaken.c

  Log Message:
  -----------
  stir_shaken: Fix heap corruption due to X509_STORE_CTX misusage

As advised by the OpenSSL docs:

"The certificates and CRLs in a store are used internally and should not
be freed up until after the associated X509_STORE_CTX is freed."

... whereas the code would attempt to create a global X509_STORE_CTX
object a single time, at OpenSIPS startup, then re-use it on each
stir_shaken_verify() call.  However, the certs would unfortunately get
freed after each verification, thus breaking the library requirements.

The solution is to simply create and free a X509_STORE_CTX object on
each verification.

Many thanks to Sandro Gauci (Enable Security) for the find!

Issue discovered during OpenSIPIt'01 (https://opensipit.org/)