Change snprintf to memcpy

There was a few uses of snprintf in the DTLS SCTP code which made more
sense to be a memcpy.
Reviewed-by: NTim Hudson <tjh@openssl.org>
Reviewed-by: NRichard Levitte <levitte@openssl.org>

ssl/statem/statem_clnt.c

@@ -1442,9 +1442,8 @@ MSG_PROCESS_RETURN tls_process_server_hello(SSL *s, PACKET *pkt)
          * Add new shared key for SCTP-Auth, will be ignored if
          * no SCTP used.
          */
-        snprintf((char *)labelbuffer,
-                 sizeof(DTLS1_SCTP_AUTH_LABEL),
-                 DTLS1_SCTP_AUTH_LABEL);
+        memcpy(labelbuffer, DTLS1_SCTP_AUTH_LABEL,
+               sizeof(DTLS1_SCTP_AUTH_LABEL));
 
         if (SSL_export_keying_material(s, sctpauthkey,
                                    sizeof(sctpauthkey),
@@ -2962,8 +2961,8 @@ int tls_client_key_exchange_post_work(SSL *s)
          * Add new shared key for SCTP-Auth, will be ignored if no SCTP
          * used.
          */
-        snprintf((char *)labelbuffer, sizeof(DTLS1_SCTP_AUTH_LABEL),
-                 DTLS1_SCTP_AUTH_LABEL);
+        memcpy(labelbuffer, DTLS1_SCTP_AUTH_LABEL,
+               sizeof(DTLS1_SCTP_AUTH_LABEL));
 
         if (SSL_export_keying_material(s, sctpauthkey,
                                    sizeof(sctpauthkey), labelbuffer,

ssl/statem/statem_srvr.c

@@ -635,8 +635,8 @@ WORK_STATE ossl_statem_server_post_work(SSL *s, WORK_STATE wst)
              * Add new shared key for SCTP-Auth, will be ignored if no
              * SCTP used.
              */
-            snprintf((char *)labelbuffer, sizeof(DTLS1_SCTP_AUTH_LABEL),
-                     DTLS1_SCTP_AUTH_LABEL);
+            memcpy(labelbuffer, DTLS1_SCTP_AUTH_LABEL,
+                   sizeof(DTLS1_SCTP_AUTH_LABEL));
 
             if (SSL_export_keying_material(s, sctpauthkey,
                     sizeof(sctpauthkey), labelbuffer,
@@ -2905,8 +2905,8 @@ WORK_STATE tls_post_process_client_key_exchange(SSL *s, WORK_STATE wst)
              * Add new shared key for SCTP-Auth, will be ignored if no SCTP
              * used.
              */
-            snprintf((char *)labelbuffer, sizeof(DTLS1_SCTP_AUTH_LABEL),
-                     DTLS1_SCTP_AUTH_LABEL);
+            memcpy(labelbuffer, DTLS1_SCTP_AUTH_LABEL,
+                   sizeof(DTLS1_SCTP_AUTH_LABEL));
 
             if (SSL_export_keying_material(s, sctpauthkey,
                                        sizeof(sctpauthkey), labelbuffer,