1 files changed, 102 insertions, 0 deletions
diff --git a/lib/iolog/iolog_swapids.c b/lib/iolog/iolog_swapids.c
new file mode 100644
index 0000000..d55123b
--- /dev/null
+++ b/lib/iolog/iolog_swapids.c
@@ -0,0 +1,102 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2009-2021 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 <stdio.h>
+#include <stdlib.h>
+#ifdef HAVE_STDBOOL_H
+# include <stdbool.h>
+#else
+# include <compat/stdbool.h>
+#endif
+#include <time.h>
+#include <unistd.h>
+
+#include <sudo_compat.h>
+#include <sudo_debug.h>
+#include <sudo_fatal.h>
+#include <sudo_gettext.h>
+#include <sudo_iolog.h>
+
+/*
+ * Set effective user and group-IDs to iolog_uid and iolog_gid.
+ * If restore flag is set, swap them back.
+ */
+bool
+iolog_swapids(bool restore)
+{
+#ifdef HAVE_SETEUID
+    static uid_t user_euid = (uid_t)-1;
+    static gid_t user_egid = (gid_t)-1;
+    const uid_t iolog_uid = iolog_get_uid();
+    const gid_t iolog_gid = iolog_get_gid();
+    debug_decl(io_swapids, SUDO_DEBUG_UTIL);
+
+    if (user_euid == (uid_t)-1)
+	user_euid = geteuid();
+    if (user_egid == (gid_t)-1)
+	user_egid = getegid();
+
+    if (user_euid == iolog_uid && user_egid == iolog_gid) {
+	sudo_debug_printf(SUDO_DEBUG_NOTICE,
+	    "%s: effective uid/gid matches iolog uid/gid, nothing to do",
+	    __func__);
+	debug_return_bool(true);
+    }
+
+    if (restore) {
+	if (seteuid(user_euid) == -1) {
+	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
+		"%s: unable to restore effective uid to %d", __func__,
+		(int)user_euid);
+	    sudo_warn("seteuid() %d -> %d", (int)iolog_uid, (int)user_euid);
+	    debug_return_bool(false);
+	}
+	if (setegid(user_egid) == -1) {
+	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
+		"%s: unable to restore effective gid to %d", __func__,
+		(int)user_egid);
+	    sudo_warn("setegid() %d -> %d", (int)iolog_gid, (int)user_egid);
+	    debug_return_bool(false);
+	}
+    } else {
+	/* Fail silently if the user has insufficient privileges. */
+	if (setegid(iolog_gid) == -1) {
+	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
+		"%s: unable to set effective gid to %d", __func__,
+		(int)iolog_gid);
+	    debug_return_bool(false);
+	}
+	if (seteuid(iolog_uid) == -1) {
+	    sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
+		"%s: unable to set effective uid to %d", __func__,
+		(int)iolog_uid);
+	    debug_return_bool(false);
+	}
+    }
+    debug_return_bool(true);
+#else
+    return false;
+#endif
+}