basically none of these build

src/libauth/auth_chuid.c

@@ -0,0 +1,38 @@
+#include <u.h>
+#include <libc.h>
+#include <auth.h>
+
+/*
+ *  become the authenticated user
+ */
+int
+auth_chuid(AuthInfo *ai, char *ns)
+{
+	int rv, fd;
+
+	if(ai == nil || ai->cap == nil){
+		werrstr("no capability");
+		return -1;
+	}
+
+	/* change uid */
+	fd = open("#¤/capuse", OWRITE);
+	if(fd < 0){
+		werrstr("opening #¤/capuse: %r");
+		return -1;
+	}
+	rv = write(fd, ai->cap, strlen(ai->cap));
+	close(fd);
+	if(rv < 0){
+		werrstr("writing %s to #¤/capuse: %r", ai->cap);
+		return -1;
+	}
+
+	/* get a link to factotum as new user */
+	fd = open("/srv/factotum", ORDWR);
+	if(fd >= 0)
+		mount(fd, -1, "/mnt", MREPL, "");
+
+	/* set up new namespace */
+	return newns(ai->cuid, ns);
+}