1 files changed, 71 insertions, 0 deletions
diff --git a/src/tcsetpgrp_nobg.c b/src/tcsetpgrp_nobg.c
new file mode 100644
index 0000000..bac0aa6
--- /dev/null
+++ b/src/tcsetpgrp_nobg.c
@@ -0,0 +1,71 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2017 Todd C. Miller <Todd.Miller@sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <config.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <signal.h>
+
+#include "sudo.h"
+
+static volatile sig_atomic_t got_sigttou;
+
+/*
+ * SIGTTOU signal handler for tcsetpgrp_nobg() that just sets a flag.
+ */
+static void
+sigttou(int signo)
+{
+    got_sigttou = 1;
+}
+
+/*
+ * Like tcsetpgrp() but restarts on EINTR _except_ for SIGTTOU.
+ * Returns 0 on success or -1 on failure, setting errno.
+ * Sets got_sigttou on failure if interrupted by SIGTTOU.
+ */
+int
+tcsetpgrp_nobg(int fd, pid_t pgrp_id)
+{
+    struct sigaction sa, osa;
+    int rc;
+
+    /*
+     * If we receive SIGTTOU from tcsetpgrp() it means we are
+     * not in the foreground process group.
+     * This avoid a TOCTOU race compared to using tcgetpgrp().
+     */
+    memset(&sa, 0, sizeof(sa));
+    sigemptyset(&sa.sa_mask);
+    sa.sa_flags = 0; /* do not restart syscalls */
+    sa.sa_handler = sigttou;
+    got_sigttou = 0;
+    (void)sigaction(SIGTTOU, &sa, &osa);
+    do {
+	rc = tcsetpgrp(fd, pgrp_id);
+    } while (rc != 0 && errno == EINTR && !got_sigttou);
+    (void)sigaction(SIGTTOU, &osa, NULL);
+
+    return rc;
+}