basically none of these build
diff --git a/src/libauth/auth_chuid.c b/src/libauth/auth_chuid.c
new file mode 100644
index 0000000..1bfbfff
--- /dev/null
+++ b/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);
+}
