Convert SSL_SESSION* functions to use const getters

Reviewed-by: NViktor Dukhovni <viktor@openssl.org>
Reviewed-by: NStephen Henson <steve@openssl.org>

doc/ssl/SSL_SESSION_has_ticket.pod

@@ -12,7 +12,7 @@ SSL_SESSION_has_ticket, SSL_SESSION_get_ticket_lifetime_hint,
 
  int SSL_SESSION_has_ticket(const SSL_SESSION *s);
  unsigned long SSL_SESSION_get_ticket_lifetime_hint(const SSL_SESSION *s);
- void SSL_SESSION_get0_ticket(const SSL_SESSION *s, unsigned char **tick,
+ void SSL_SESSION_get0_ticket(const SSL_SESSION *s, const unsigned char **tick,
                               size_t *len);
 
 =head1 DESCRIPTION

include/openssl/ssl.h

@@ -1400,7 +1400,7 @@ __owur const char *SSL_SESSION_get0_hostname(const SSL_SESSION *s);
 __owur const SSL_CIPHER *SSL_SESSION_get0_cipher(const SSL_SESSION *s);
 __owur int SSL_SESSION_has_ticket(const SSL_SESSION *s);
 __owur unsigned long SSL_SESSION_get_ticket_lifetime_hint(const SSL_SESSION *s);
-void SSL_SESSION_get0_ticket(const SSL_SESSION *s, unsigned char **tick,
+void SSL_SESSION_get0_ticket(const SSL_SESSION *s, const unsigned char **tick,
                             size_t *len);
 __owur int SSL_copy_session_id(SSL *to, const SSL *from);
 __owur X509 *SSL_SESSION_get0_peer(SSL_SESSION *s);

ssl/ssl_sess.c

@@ -847,7 +847,7 @@ unsigned long SSL_SESSION_get_ticket_lifetime_hint(const SSL_SESSION *s)
     return s->tlsext_tick_lifetime_hint;
 }
 
-void SSL_SESSION_get0_ticket(const SSL_SESSION *s, unsigned char **tick,
+void SSL_SESSION_get0_ticket(const SSL_SESSION *s, const unsigned char **tick,
                             size_t *len)
 {
     *len = s->tlsext_ticklen;

test/handshake_helper.c

@@ -699,7 +699,7 @@ static HANDSHAKE_RESULT *do_handshake_internal(
     int client_turn = 1;
     connect_phase_t phase = HANDSHAKE;
     handshake_status_t status = HANDSHAKE_RETRY;
-    unsigned char* tick = NULL;
+    const unsigned char* tick = NULL;
     size_t tick_len = 0;
     SSL_SESSION* sess = NULL;
     const unsigned char *proto = NULL;