sizeof(struct) is usually wrong in 64-bits if the structure is
used for marshalling.  this was found by cinap.
need to write a tool for this.

Reference: /n/atom/patch/applied/chap64
Date: Sun Feb 16 12:53:48 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/auth/authsrv.c	Sun Feb 16 12:52:12 2014
+++ /sys/src/cmd/auth/authsrv.c	Sun Feb 16 12:52:13 2014
@@ -577,7 +577,7 @@
 	/*
 	 *  get chap reply
 	 */
-	if(readn(0, &reply, sizeof(reply)) < 0)
+	if(readn(0, &reply, OCHAPREPLYLEN) < 0)
 		exits(0);
 	safecpy(tr->uid, reply.uid, sizeof(tr->uid));
 
@@ -654,7 +654,7 @@
 	/*
 	 *  get chap reply
 	 */
-	if(readn(0, &reply, sizeof(reply)) < 0)
+	if(readn(0, &reply, OMSCHAPREPLYLEN) < 0)
 		exits(0);
 
 	safecpy(tr->uid, reply.uid, sizeof(tr->uid));
--- /sys/include/authsrv.h	Sun Feb 16 12:52:14 2014
+++ /sys/include/authsrv.h	Sun Feb 16 12:52:14 2014
@@ -100,6 +100,7 @@
 	char	uid[ANAMELEN];
 	char	resp[OMD5LEN];
 };
+#define OCHAPREPLYLEN	(1+ANAMELEN+OMD5LEN)
 
 struct	OMSchapreply
 {
@@ -107,6 +108,7 @@
 	char	LMresp[24];		/* Lan Manager response */
 	char	NTresp[24];		/* NT response */
 };
+#define OMSCHAPREPLYLEN	(ANAMELEN+24+24)
 
 /*
  *  convert to/from wire format
--- /sys/src/cmd/auth/factotum/chap.c	Sun Feb 16 12:52:15 2014
+++ /sys/src/cmd/auth/factotum/chap.c	Sun Feb 16 12:52:16 2014
@@ -33,7 +33,10 @@
 
 	MShashlen = 16,
 	MSchallen = 8,
-	MSresplen = 24
+	MSresplen = 24,
+
+	Chapreplylen = MD5LEN+1,
+	MSchapreplylen = 24+24,
 };
 
 static int
@@ -169,7 +172,7 @@
 		ds = md5(&cr.id, 1, 0, 0);
 		md5((uchar*)pw, npw, 0, ds);
 		md5(chal, nchal, (uchar*)cr.resp, ds);
-		if(convwrite(c, &cr, sizeof cr) < 0)
+		if(convwrite(c, &cr, Chapreplylen) < 0)
 			goto out;
 	}else{
 		uchar hash[MShashlen];
@@ -182,7 +185,7 @@
 			nthash(hash, pw);
 			mschalresp((uchar*)mscr.NTresp, hash, chal);
 		}
-		if(convwrite(c, &mscr, sizeof mscr) < 0)
+		if(convwrite(c, &mscr, MSchapreplylen) < 0)
 			goto out;
 	}