Fix two typos in comments
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 2bb4fcd..2d9c591 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -1743,7 +1743,7 @@
         == MBEDTLS_KEY_EXCHANGE_RSA )
     {
         ((void) ret);
-        /* The premaster secret has already been by
+        /* The premaster secret has already been set by
          * ssl_rsa_generate_partial_pms(). Only the
          * PMS length needs to be set. */
         ssl->handshake->pmslen = 48;