Race Condition

[Dr Paul Dale]

The SSL sessions are not thread safe.  It is up to the calling application to ensure that this race condition does not occur.


Pauli
-- 
Dr Paul Dale | Cryptographer | Network Security & Encryption 
Phone +61 7 3031 7217
Oracle Australia



> On 14 Jun 2019, at 8:09 pm, Serti Ayoub <ayb.serti at gmail.com> wrote:
> 
> Hi,
> 
> We upgraded a code base from openssl 1.0.2 to openssl1.1.1b.
> The upgrade was straightforward and we manage to activate and use TLS1.3.
> OpenSSL is used to implement multi-threaded HTTPS server. 
> 
> While using TLS1.3 as the minimum version with option SSL_OP_NO_TICKET  the app crash randomly due to a race condition in openssl, exactly when 2 threads use the same SSL_SESSION*.
> 
> Some t
> 
> We don't install any session management callback and we keep session caching mode to 2 ( SSL_SESS_CACHE_SERVER).
> 
> I made some debugging/tracing and I found that SSL_OP_NO_TICKET force openssl to call lookup_sess_in_cache() function ( file ssl_sess.c )  
> 
>         CRYPTO_THREAD_read_lock(s->session_ctx->lock);
>         ret = lh_SSL_SESSION_retrieve(s->session_ctx->sessions, &data);
>         if (ret != NULL) {
>             /* don't allow other threads to steal it: */
>             SSL_SESSION_up_ref(ret);
>         }
>         CRYPTO_THREAD_unlock(s->session_ctx->lock);
> 
> lh_SSL_SESSION_retriev() doesn't make any lock check in retrieved session and lookup_sess_in_cache don't lock the session avec SSL_SESSION have a CRYPT_RWLOCK member.
> 
> I can't provide a sample to reproduce the crash, it's totaly random.
>  
> Here example of thread call stack:
> 
> Thread1:
> libssl-1_1-x64.dll!tls_parse_ctos_supported_groups(ssl_st * s, PACKET * pkt, unsigned int context, x509_st * x, unsigned __int64 chainidx) Ligne 966	C
>  	libssl-1_1-x64.dll!tls_parse_extension(ssl_st * s, tlsext_index_en idx, int context, raw_extension_st * exts, x509_st * x, unsigned __int64 chainidx) Ligne 715	C
>  	libssl-1_1-x64.dll!tls_parse_all_extensions(ssl_st * s, int context, raw_extension_st * exts, x509_st * x, unsigned __int64 chainidx, int fin) Ligne 748	C
>  	libssl-1_1-x64.dll!tls_early_post_process_client_hello(ssl_st * s) Ligne 1883	C
>  	libssl-1_1-x64.dll!tls_post_process_client_hello(ssl_st * s, WORK_STATE wst) Ligne 2222	C
>  	libssl-1_1-x64.dll!ossl_statem_server_post_process_message(ssl_st * s, WORK_STATE wst) Ligne 1220	C
>  	libssl-1_1-x64.dll!read_state_machine(ssl_st * s) Ligne 664	C
>  	libssl-1_1-x64.dll!state_machine(ssl_st * s, int server) Ligne 434	C
>  	libssl-1_1-x64.dll!ossl_statem_accept(ssl_st * s) Ligne 256	C
>  	libssl-1_1-x64.dll!ssl3_read_bytes(ssl_st * s, int type, int * recvd_type, unsigned char * buf, unsigned __int64 len, int peek, unsigned __int64 * readbytes) Ligne 1270	C
>  	libssl-1_1-x64.dll!ssl3_read_internal(ssl_st * s, void * buf, unsigned __int64 len, int peek, unsigned __int64 * readbytes) Ligne 4473	C
>  	libssl-1_1-x64.dll!ssl3_read(ssl_st * s, void * buf, unsigned __int64 len, unsigned __int64 * readbytes) Ligne 4498	C
>  	libssl-1_1-x64.dll!ssl_read_internal(ssl_st * s, void * buf, unsigned __int64 num, unsigned __int64 * readbytes) Ligne 1754	C
>  	libssl-1_1-x64.dll!SSL_read(ssl_st * s, void * buf, int num) Ligne 1766	C
> 
> Thread2:
>  	libcrypto-1_1-x64.dll!CRYPTO_malloc(unsigned __int64 num, const char * file, int line) Ligne 222	C
>  libssl-1_1-x64.dll!tls1_save_u16(PACKET * pkt, wchar_t * * pdest, unsigned __int64 * pdestlen) Ligne 1779	C
>  	libssl-1_1-x64.dll!tls_parse_ctos_supported_groups(ssl_st * s, PACKET * pkt, unsigned int context, x509_st * x, unsigned __int64 chainidx) Ligne 968	C
>  	libssl-1_1-x64.dll!tls_parse_extension(ssl_st * s, tlsext_index_en idx, int context, raw_extension_st * exts, x509_st * x, unsigned __int64 chainidx) Ligne 715	C
>  	libssl-1_1-x64.dll!tls_parse_all_extensions(ssl_st * s, int context, raw_extension_st * exts, x509_st * x, unsigned __int64 chainidx, int fin) Ligne 748	C
>  	libssl-1_1-x64.dll!tls_early_post_process_client_hello(ssl_st * s) Ligne 1883	C
>  	libssl-1_1-x64.dll!tls_post_process_client_hello(ssl_st * s, WORK_STATE wst) Ligne 2222	C
>  	libssl-1_1-x64.dll!ossl_statem_server_post_process_message(ssl_st * s, WORK_STATE wst) Ligne 1220	C
>  	libssl-1_1-x64.dll!read_state_machine(ssl_st * s) Ligne 664	C
>  	libssl-1_1-x64.dll!state_machine(ssl_st * s, int server) Ligne 434	C
>  	libssl-1_1-x64.dll!ossl_statem_accept(ssl_st * s) Ligne 256	C
>  	libssl-1_1-x64.dll!ssl3_read_bytes(ssl_st * s, int type, int * recvd_type, unsigned char * buf, unsigned __int64 len, int peek, unsigned __int64 * readbytes) Ligne 1270	C
>  	libssl-1_1-x64.dll!ssl3_read_internal(ssl_st * s, void * buf, unsigned __int64 len, int peek, unsigned __int64 * readbytes) Ligne 4473	C
>  	libssl-1_1-x64.dll!ssl3_read(ssl_st * s, void * buf, unsigned __int64 len, unsigned __int64 * readbytes) Ligne 4498	C
>  	libssl-1_1-x64.dll!ssl_read_internal(ssl_st * s, void * buf, unsigned __int64 num, unsigned __int64 * readbytes) Ligne 1754	C
>  	libssl-1_1-x64.dll!SSL_read(ssl_st * s, void * buf, int num) Ligne 1766	C
> 
> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mta.openssl.org/pipermail/openssl-users/attachments/20190614/15bc1210/attachment-0001.html>