RT2759: Don't read TTY when already at EOF.

Reviewed-by: NAndy Polyakov <appro@openssl.org>

apps/s_client.c

@@ -818,6 +818,7 @@ int s_client_main(int argc, char **argv)
     int socket_family = AF_UNSPEC, socket_type = SOCK_STREAM;
     int starttls_proto = PROTO_OFF, crl_format = FORMAT_PEM, crl_download = 0;
     int write_tty, read_tty, write_ssl, read_ssl, tty_on, ssl_pending;
+    int at_eof = 0;
     int read_buf_len = 0;
     int fallback_scsv = 0;
     long randamt = 0;
@@ -2123,7 +2124,12 @@ int s_client_main(int argc, char **argv)
         if (!ssl_pending) {
 #if !defined(OPENSSL_SYS_WINDOWS) && !defined(OPENSSL_SYS_MSDOS)
             if (tty_on) {
-                if (read_tty)
+                /*
+                 * Note that select() returns when read _would not block_,
+                 * and EOF satisfies that.  To avoid a CPU-hogging loop,
+                 * set the flag so we exit.
+                 */
+                if (read_tty && !at_eof)
                     openssl_fdset(fileno(stdin), &readfds);
                 if (write_tty)
                     openssl_fdset(fileno(stdout), &writefds);
@@ -2369,6 +2375,9 @@ int s_client_main(int argc, char **argv)
             } else
                 i = raw_read_stdin(cbuf, BUFSIZZ);
 
+            if (i == 0)
+                at_eof = 1;
+
             if ((!c_ign_eof) && ((i <= 0) || (cbuf[0] == 'Q' && cmdletters))) {
                 BIO_printf(bio_err, "DONE\n");
                 ret = 0;