[OpenSIPS-Devel] [OpenSIPS/opensips] 11995a: stir_shaken: Fix heap corruption due to X509_STORE...

[Liviu Chircu]

  Branch: refs/heads/3.1
  Home:   https://github.com/OpenSIPS/opensips
  Commit: 11995a0a6ead5ef5588bf123486f8dd906f85435
      https://github.com/OpenSIPS/opensips/commit/11995a0a6ead5ef5588bf123486f8dd906f85435
  Author: Liviu Chircu <liviu at opensips.org>
  Date:   2021-04-15 (Thu, 15 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 and Alfred Farrugia (Enable Security) for
helping uncover this issue!

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

(cherry picked from commit db899f6df1110463935ce57745f82294a55f6f7a)