Race Condition

[Serti Ayoub]

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
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