Add fork handlers, based on pthread_atfork

Only for Unix platforms

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3754)

crypto/include/internal/cryptlib.h

@@ -66,6 +66,7 @@ extern unsigned int OPENSSL_ia32cap_P[];
 void OPENSSL_showfatal(const char *fmta, ...);
 extern int OPENSSL_NONPIC_relocated;
 void crypto_cleanup_all_ex_data_int(void);
+int openssl_init_fork_handlers(void);
 
 int openssl_strerror_r(int errnum, char *buf, size_t buflen);
 # if !defined(OPENSSL_NO_STDIO)

crypto/init.c

@@ -552,6 +552,10 @@ int OPENSSL_init_crypto(uint64_t opts, const OPENSSL_INIT_SETTINGS *settings)
             && !RUN_ONCE(&add_all_digests, ossl_init_add_all_digests))
         return 0;
 
+    if ((opts & OPENSSL_INIT_NO_ATFORK) == 0
+            && !openssl_init_fork_handlers())
+        return 0;
+
     if ((opts & OPENSSL_INIT_NO_LOAD_CONFIG)
             && !RUN_ONCE(&config, ossl_init_no_config))
         return 0;
@@ -677,3 +681,28 @@ int OPENSSL_atexit(void (*handler)(void))
 
     return 1;
 }
+
+#ifdef OPENSSL_SYS_UNIX
+/*
+ * The following three functions are for OpenSSL developers.  This is
+ * where we set/reset state across fork (called via pthread_atfork when
+ * it exists, or manually by the application when it doesn't).
+ *
+ * WARNING!  If you put code in either OPENSSL_fork_parent or
+ * OPENSSL_fork_child, you MUST MAKE SURE that they are async-signal-
+ * safe.  See this link, for example:
+ *      http://man7.org/linux/man-pages/man7/signal-safety.7.html
+ */
+
+void OPENSSL_fork_prepare(void)
+{
+}
+
+void OPENSSL_fork_parent(void)
+{
+}
+
+void OPENSSL_fork_child(void)
+{
+}
+#endif

crypto/threads_none.c

@@ -121,4 +121,9 @@ int CRYPTO_atomic_add(int *val, int amount, int *ret, CRYPTO_RWLOCK *lock)
     return 1;
 }
 
+int openssl_init_fork_handlers(void)
+{
+    return 0;
+}
+
 #endif

crypto/threads_pthread.c

@@ -8,6 +8,7 @@
  */
 
 #include <openssl/crypto.h>
+#include <internal/cryptlib.h>
 
 #if defined(OPENSSL_THREADS) && !defined(CRYPTO_TDEBUG) && !defined(OPENSSL_SYS_WINDOWS)
 
@@ -168,4 +169,13 @@ int CRYPTO_atomic_add(int *val, int amount, int *ret, CRYPTO_RWLOCK *lock)
     return 1;
 }
 
+int openssl_init_fork_handlers(void)
+{
+# ifdef OPENSSL_SYS_UNIX
+    if (pthread_atfork(OPENSSL_fork_prepare,
+                       OPENSSL_fork_parent, OPENSSL_fork_child) == 0)
+        return 1;
+# endif
+    return 0;
+}
 #endif

crypto/threads_win.c

@@ -133,4 +133,9 @@ int CRYPTO_atomic_add(int *val, int amount, int *ret, CRYPTO_RWLOCK *lock)
     return 1;
 }
 
+int openssl_init_fork_handlers(void)
+{
+    return 0;
+}
+
 #endif

doc/man3/OPENSSL_fork_prepare.pod

@@ -0,0 +1,58 @@
+=pod
+
+=head1 NAME
+
+OPENSSL_fork_prepare,
+OPENSSL_fork_parent,
+OPENSSL_fork_child
+- OpenSSL fork handlers
+
+=head1 SYNOPSIS
+
+ #include <openssl/crypto.h>
+
+ void OPENSSL_fork_prepare(void);
+ void OPENSSL_fork_parent(void);
+ void OPENSSL_fork_child(void);
+
+=head1 DESCRIPTION
+
+OpenSSL has state that should be reset when a process forks. For example,
+the entropy pool used to generate random numbers (and therefore encryption
+keys) should not be shared across multiple programs.
+The OPENSSL_fork_prepare(), OPENSSL_fork_parent(), and OPENSSL_fork_child()
+functions are used to reset this internal state.
+
+Platforms without fork(2) will probably not need to use these functions.
+Platforms with fork(2) but without pthreads_atfork(3) will probably need
+to call them manually, as described in the following paragraph.  Platforms
+such as Linux that have both functions will normally not need to call these
+functions as the OpenSSL library will do so automatically.
+
+L<OPENSSL_init_crypto(3)> will register these funtions with the appropriate
+hander, unless the B<OPENSSL_INIT_NO_ATFORK> flag is used. For those
+applications, these functions can be called directly. They should be used
+according to the calling sequence described by the pthreads_atfork(3)
+documentation, which is summarized here.  OPENSSL_fork_prepare() should
+be called before a fork() is done.  After the fork() returns, the parent
+process should call OPENSSL_fork_parent() and the child process should
+call OPENSSL_fork_child().
+
+=head1 SEE ALSO
+
+L<OPENSSL_init_crypto(3)>
+
+=head1 HISTORY
+
+These functions were added in OpenSSL 1.1.1.
+
+=head1 COPYRIGHT
+
+Copyright 2017 The OpenSSL Project Authors. All Rights Reserved.
+
+Licensed under the OpenSSL license (the "License").  You may not use
+this file except in compliance with the License.  You can obtain a copy
+in the file LICENSE in the source distribution or at
+L<https://www.openssl.org/source/license.html>.
+
+=cut

doc/man3/OPENSSL_init_crypto.pod

@@ -150,6 +150,11 @@ With this option the library will automatically load and initialise all the
 built in engines listed above with the exception of the openssl and dasync
 engines. This not a default option.
 
+=item OPENSSL_INIT_NO_ATFORK
+
+With this option the library will not register its fork handlers.
+See OPENSSL_fork_prepare(3) for details.
+
 =back
 
 Multiple options may be combined together in a single call to

include/openssl/crypto.h

@@ -332,6 +332,11 @@ int FIPS_mode(void);
 int FIPS_mode_set(int r);
 
 void OPENSSL_init(void);
+# ifdef OPENSSL_SYS_UNIX
+void OPENSSL_fork_prepare(void);
+void OPENSSL_fork_parent(void);
+void OPENSSL_fork_child(void);
+# endif
 
 struct tm *OPENSSL_gmtime(const time_t *timer, struct tm *result);
 int OPENSSL_gmtime_adj(struct tm *tm, int offset_day, long offset_sec);
@@ -364,7 +369,8 @@ int CRYPTO_memcmp(const void * in_a, const void * in_b, size_t len);
 # define OPENSSL_INIT_ENGINE_CAPI            0x00002000L
 # define OPENSSL_INIT_ENGINE_PADLOCK         0x00004000L
 # define OPENSSL_INIT_ENGINE_AFALG           0x00008000L
-/* OPENSSL_INIT flag 0x00010000 reserved for internal use */
+# define OPENSSL_INIT_reserved_internal      0x00010000L
+# define OPENSSL_INIT_NO_ATFORK              0x00020000L
 /* OPENSSL_INIT flag range 0xfff00000 reserved for OPENSSL_init_ssl() */
 /* Max OPENSSL_INIT flag value is 0x80000000 */
 

util/libcrypto.num

@@ -4342,3 +4342,6 @@ OSSL_STORE_INFO_set0_NAME_description   4284	1_1_1	EXIST::FUNCTION:
 OSSL_STORE_INFO_get1_NAME_description   4285	1_1_1	EXIST::FUNCTION:
 OSSL_STORE_do_all_loaders               4286	1_1_1	EXIST::FUNCTION:
 OSSL_STORE_LOADER_get0_engine           4287	1_1_1	EXIST::FUNCTION:
+OPENSSL_fork_prepare                    4288	1_1_1	EXIST:UNIX:FUNCTION:
+OPENSSL_fork_parent                     4289	1_1_1	EXIST:UNIX:FUNCTION:
+OPENSSL_fork_child                      4290	1_1_1	EXIST:UNIX:FUNCTION: