1 files changed, 87 insertions, 0 deletions
diff --git a/crypto/openssh/uidswap.c b/crypto/openssh/uidswap.c
new file mode 100644
index 000000000000..aebff0c73c88
--- /dev/null
+++ b/crypto/openssh/uidswap.c
@@ -0,0 +1,87 @@
+/*
+ * Author: Tatu Ylonen <ylo@cs.hut.fi>
+ * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+ *                    All rights reserved
+ * Created: Sat Sep  9 01:56:14 1995 ylo
+ * Code for uid-swapping.
+ */
+
+#include "includes.h"
+RCSID("$Id: uidswap.c,v 1.5 1999/11/24 19:53:54 markus Exp $");
+
+#include "ssh.h"
+#include "uidswap.h"
+
+/*
+ * Note: all these functions must work in all of the following cases:
+ *    1. euid=0, ruid=0
+ *    2. euid=0, ruid!=0
+ *    3. euid!=0, ruid!=0
+ * Additionally, they must work regardless of whether the system has
+ * POSIX saved uids or not.
+ */
+
+#ifdef _POSIX_SAVED_IDS
+/* Lets assume that posix saved ids also work with seteuid, even though that
+   is not part of the posix specification. */
+#define SAVED_IDS_WORK_WITH_SETEUID
+#endif /* _POSIX_SAVED_IDS */
+
+/* Saved effective uid. */
+static uid_t saved_euid = 0;
+
+/*
+ * Temporarily changes to the given uid.  If the effective user
+ * id is not root, this does nothing.  This call cannot be nested.
+ */
+void 
+temporarily_use_uid(uid_t uid)
+{
+#ifdef SAVED_IDS_WORK_WITH_SETEUID
+	/* Save the current euid. */
+	saved_euid = geteuid();
+
+	/* Set the effective uid to the given (unprivileged) uid. */
+	if (seteuid(uid) == -1)
+		debug("seteuid %d: %.100s", (int) uid, strerror(errno));
+#else /* SAVED_IDS_WORK_WITH_SETUID */
+	/* Propagate the privileged uid to all of our uids. */
+	if (setuid(geteuid()) < 0)
+		debug("setuid %d: %.100s", (int) geteuid(), strerror(errno));
+
+	/* Set the effective uid to the given (unprivileged) uid. */
+	if (seteuid(uid) == -1)
+		debug("seteuid %d: %.100s", (int) uid, strerror(errno));
+#endif /* SAVED_IDS_WORK_WITH_SETEUID */
+}
+
+/*
+ * Restores to the original uid.
+ */
+void 
+restore_uid()
+{
+#ifdef SAVED_IDS_WORK_WITH_SETEUID
+	/* Set the effective uid back to the saved uid. */
+	if (seteuid(saved_euid) < 0)
+		debug("seteuid %d: %.100s", (int) saved_euid, strerror(errno));
+#else /* SAVED_IDS_WORK_WITH_SETEUID */
+	/*
+	 * We are unable to restore the real uid to its unprivileged value.
+	 * Propagate the real uid (usually more privileged) to effective uid
+	 * as well.
+	 */
+	setuid(getuid());
+#endif /* SAVED_IDS_WORK_WITH_SETEUID */
+}
+
+/*
+ * Permanently sets all uids to the given uid.  This cannot be
+ * called while temporarily_use_uid is effective.
+ */
+void 
+permanently_set_uid(uid_t uid)
+{
+	if (setuid(uid) < 0)
+		debug("setuid %d: %.100s", (int) uid, strerror(errno));
+}