drbg: ensure fork-safety without using a pthread_atfork handler

When the new OpenSSL CSPRNG was introduced in version 1.1.1,
it was announced in the release notes that it would be fork-safe,
which the old CSPRNG hadn't been.

The fork-safety was implemented using a fork count, which was
incremented by a pthread_atfork handler. Initially, this handler
was enabled by default. Unfortunately, the default behaviour
had to be changed for other reasons in commit b5319bdbd095, so
the new OpenSSL CSPRNG failed to keep its promise.

This commit restores the fork-safety using a different approach.
It replaces the fork count by a fork id, which coincides with
the process id on UNIX-like operating systems and is zero on other
operating systems. It is used to detect when an automatic reseed
after a fork is necessary.

To prevent a future regression, it also adds a test to verify that
the child reseeds after fork.

CVE-2019-1549

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9832)

1 files changed, 1 insertions, 0 deletions

diff --git a/include/internal/cryptlib.h b/include/internal/cryptlib.h
index d591f203d2..cfac74a328 100644
--- a/include/internal/cryptlib.h
+++ b/include/internal/cryptlib.h
@@ -93,6 +93,7 @@ void OPENSSL_showfatal(const char *fmta, ...);
 int do_ex_data_init(OPENSSL_CTX *ctx);
 void crypto_cleanup_all_ex_data_int(OPENSSL_CTX *ctx);
 int openssl_init_fork_handlers(void);
+int openssl_get_fork_id(void);
 
 char *ossl_safe_getenv(const char *name);