[Bug 1983100] Re: dotnet build intermittently crashes with segfault on Ubuntu 18.04

[Nicolas Bock]

** Patch added: "openssl-atexit-1.debdiff"
   https://bugs.launchpad.net/ubuntu/+source/openssl/+bug/1983100/+attachment/5607147/+files/openssl-atexit-1.debdiff

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https://bugs.launchpad.net/bugs/1983100

Title:
  dotnet build intermittently crashes with segfault on Ubuntu 18.04

Status in openssl package in Ubuntu:
  New
Status in openssl source package in Bionic:
  New

Bug description:
  [Impact]

  Bionic's OpenSSL 1.1.1 package
  (https://launchpad.net/ubuntu/bionic/+source/openssl) is the only
  version of openssl 1.1.1 on any distro that we've encountered that
  does not have support for the OPENSSL_NO_ATEXIT functionality from
  1.1.1b (openssl/openssl at c2b3db2).

  The threading model in .NET has the possibility that background
  threads are still running when exit() is called, which can cause
  SIGSEGV if a background thread interacts with OpenSSL after/while it
  has unloaded. For that reason, we always initialize OpenSSL 1.1.1 with
  the OPENSSL_NO_ATEXIT flag (which, of all the distros we run on only
  has no effect on Bionic).

  We feel that the stability of applications on Ubuntu 18.04 would be
  improved if the functionality of OPENSSL_NO_ATEXIT was merged into the
  bionic openssl 1.1.1 package, even if the constant isn't published
  into the header for the dev package.

  Context:
  https://github.com/dotnet/runtime/issues/48411#issuecomment-1178405101

  [Test Plan]

  The described behavior can be reproduced by passing the
  OPENSSL_NO_ATEXIT to the OPENSSL_init_ssl() call. The application will
  terminate with a SEGFAULT. More concretely, a minimal reproducer is:

  #include <stdio.h>
  #include <openssl/err.h>
  #include <openssl/ssl.h>

  #ifndef OPENSSL_INIT_NO_ATEXIT
  #define OPENSSL_INIT_NO_ATEXIT 0x00080000L
  #endif

  static void print_error_string()
  {
      printf("print_error_string:\n");
      printf("ERR_reason_error_string(0) => %s\n", ERR_reason_error_string(0));
  }

  int main(int argc, char* argv[])
  {
      // register this handler first, so it runs last.
      atexit(print_error_string);

      OPENSSL_init_ssl(
              OPENSSL_INIT_ADD_ALL_CIPHERS |
              OPENSSL_INIT_ADD_ALL_DIGESTS |
              OPENSSL_INIT_LOAD_CONFIG |
              OPENSSL_INIT_NO_ATEXIT |
              OPENSSL_INIT_LOAD_CRYPTO_STRINGS |
              OPENSSL_INIT_LOAD_SSL_STRINGS,
          NULL);

      print_error_string();

      return 0;
  }

  Building

  $ sudo apt install libssl-dev
  $ gcc test.c -lssl -lcrypto
  $ ./a.out
  print_error_string:
  ERR_reason_error_string(0) => (null)
  print_error_string:
  Segmentation fault (core dumped)

  [Where problems could occur]

  The patches adds an option to the OPENSSL_init_crypto() function to
  disable the default behavior of calling of a cleanup function on
  application exit. The patch also includes a few bug fixes around
  various initializations that were supposed to happen once when running
  threaded but were not.

  These changes have the potential for regressions and it is conceivable
  that they lead to incorrect behavior. However, I have also backported
  and included all new testing functions in the hope that the changed
  behavior will get appropriate testing.

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