use deterministic handles
diff --git a/src/cmd/vbackup/vnfs.c b/src/cmd/vbackup/vnfs.c
index 019f7f7..047d337 100644
--- a/src/cmd/vbackup/vnfs.c
+++ b/src/cmd/vbackup/vnfs.c
@@ -207,12 +207,16 @@
*
* The decrypted handles begin with the following header:
*
- * rand[12] random bytes used to make encryption non-deterministic
- * len[4] length of handle that follows
* sessid[8] random session id chosen at start time
+ * len[4] length of handle that follows
*
* If we're pressed for space in the rest of the handle, we could
- * probably reduce the amount of randomness.
+ * probably reduce the amount of sessid bytes. Note that the sessid
+ * bytes must be consistent during a run of vnfs, or else some
+ * clients (e.g., Linux 2.4) eventually notice that successive TLookups
+ * return different handles, and they return "Stale NFS file handle"
+ * errors to system calls in response (even though we never sent
+ * that error!).
*
* Security woes aside, the fact that we have to shove everything
* into the handles is quite annoying. We have to encode, in 40 bytes:
@@ -231,9 +235,8 @@
enum
{
- RandSize = 16,
SessidSize = 8,
- HeaderSize = RandSize+SessidSize,
+ HeaderSize = SessidSize+4,
MaxHandleSize = Nfs3MaxHandleSize - HeaderSize
};
@@ -269,16 +272,13 @@
p = h->h;
memmove(p+HeaderSize, p, h->len);
- *(u32int*)p = fastrand();
- *(u32int*)(p+4) = fastrand();
- *(u32int*)(p+8) = fastrand();
- *(u32int*)(p+12) = h->len;
- memmove(p+16, sessid, SessidSize);
+ memmove(p, sessid, SessidSize);
+ *(u32int*)(p+SessidSize) = h->len;
h->len += HeaderSize;
if(encryptedhandles){
while(h->len < MaxHandleSize)
- h->h[h->len++] = fastrand();
+ h->h[h->len++] = 0;
aes = aesstate;
aesCBCencrypt(h->h, MaxHandleSize, &aes);
}
@@ -305,9 +305,11 @@
aes = aesstate;
aesCBCdecrypt(h->h, h->len, &aes);
}
- if(memcmp(h->h+RandSize, sessid, sizeof sessid) != 0)
+ if(memcmp(h->h, sessid, SessidSize) != 0)
return Nfs3ErrStale; /* give benefit of doubt */
- h->len = *(u32int*)(h->h+12); /* XXX byte order */
+ h->len = *(u32int*)(h->h+SessidSize);
+ if(h->len >= MaxHandleSize-HeaderSize)
+ return Nfs3ErrBadHandle;
memmove(h->h, h->h+HeaderSize, h->len);
return Nfs3Ok;
}
