Avoid double free with OpenSSL 1.1.0

Since commit OpenSSL_1_1_0-pre3~178
https://github.com/openssl/openssl/commit/b184e3ef73200cb3b7914a603b43a5b8a074c85f
OpenSSL automatically cleans up some of its internal data when the
program exits. This conflicts with some similar clean up
libimobiledevice attempts to do, which causes a double-free.
SSL_COMP_free_compression_methods() was available in OpenSSL 1.0.2,
and is still there in 1.1.0 as a no-op, so we can use that to free
the compression methods.

This bug can be hit with a simple idevicebackup2 --help

==14299== Invalid read of size 4
==14299==    at 0x547AEBC: OPENSSL_sk_pop_free (stack.c:263)
==14299==    by 0x508B848: ssl_library_stop (ssl_init.c:182)
==14299==    by 0x5424D11: OPENSSL_cleanup (init.c:402)
==14299==    by 0x5DC3134: __cxa_finalize (cxa_finalize.c:56)
==14299==    by 0x53332B2: ??? (in /usr/lib64/libcrypto.so.1.1.0e)
==14299==    by 0x4011232: _dl_fini (dl-fini.c:235)
==14299==    by 0x5DC2DC7: __run_exit_handlers (exit.c:83)
==14299==    by 0x5DC2E19: exit (exit.c:105)
==14299==    by 0x5DA8604: (below main) (libc-start.c:329)
==14299==  Address 0x6585590 is 0 bytes inside a block of size 40 free'd
==14299==    at 0x4C2FCC8: free (vg_replace_malloc.c:530)
==14299==    by 0x4E43381: sk_SSL_COMP_free (ssl.h:830)
==14299==    by 0x4E434E7: internal_idevice_deinit (idevice.c:103)
==14299==    by 0x5B79643: __pthread_once_slow (pthread_once.c:116)
==14299==    by 0x4E5663A: thread_once (thread.c:104)
==14299==    by 0x4E43525: libimobiledevice_deinitialize (idevice.c:140)
==14299==    by 0x4011232: _dl_fini (dl-fini.c:235)
==14299==    by 0x5DC2DC7: __run_exit_handlers (exit.c:83)
==14299==    by 0x5DC2E19: exit (exit.c:105)
==14299==    by 0x5DA8604: (below main) (libc-start.c:329)
==14299==  Block was alloc'd at
==14299==    at 0x4C2EB1B: malloc (vg_replace_malloc.c:299)
==14299==    by 0x5428908: CRYPTO_zalloc (mem.c:100)
==14299==    by 0x547A9AE: OPENSSL_sk_new (stack.c:108)
==14299==    by 0x5087D43: sk_SSL_COMP_new (ssl.h:830)
==14299==    by 0x5087D43: do_load_builtin_compressions (ssl_ciph.c:482)
==14299==    by 0x5087D43: do_load_builtin_compressions_ossl_ (ssl_ciph.c:476)
==14299==    by 0x5B79643: __pthread_once_slow (pthread_once.c:116)
==14299==    by 0x547B198: CRYPTO_THREAD_run_once (threads_pthread.c:106)
==14299==    by 0x5089F96: load_builtin_compressions (ssl_ciph.c:500)
==14299==    by 0x5089F96: SSL_COMP_get_compression_methods (ssl_ciph.c:1845)
==14299==    by 0x508B68B: ossl_init_ssl_base (ssl_init.c:125)
==14299==    by 0x508B68B: ossl_init_ssl_base_ossl_ (ssl_init.c:25)
==14299==    by 0x5B79643: __pthread_once_slow (pthread_once.c:116)
==14299==    by 0x547B198: CRYPTO_THREAD_run_once (threads_pthread.c:106)
==14299==    by 0x508B90A: OPENSSL_init_ssl (ssl_init.c:227)
==14299==    by 0x4E43416: internal_idevice_init (idevice.c:73)
=

Signed-off-by: Christophe Fergeau <cfergeau@redhat.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/src/idevice.c b/src/idevice.c
index 913038e..d1f13cb 100644
--- a/src/idevice.c
+++ b/src/idevice.c
@@ -51,6 +51,14 @@
 #include "common/debug.h"
 
 #ifdef HAVE_OPENSSL
+
+#if OPENSSL_VERSION_NUMBER < 0x10002000L
+static void SSL_COMP_free_compression_methods(void)
+{
+	sk_SSL_COMP_free(SSL_COMP_get_compression_methods());
+}
+#endif
+
 static mutex_t *mutex_buf = NULL;
 static void locking_function(int mode, int n, const char* file, int line)
 {
@@ -100,7 +108,7 @@ static void internal_idevice_deinit(void)
 
 	EVP_cleanup();
 	CRYPTO_cleanup_all_ex_data();
-	sk_SSL_COMP_free(SSL_COMP_get_compression_methods());
+	SSL_COMP_free_compression_methods();
 #ifdef HAVE_ERR_REMOVE_THREAD_STATE
 	ERR_remove_thread_state(NULL);
 #else