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SUNRPC: The transmitted message must lie in the RPCSEC window of validity

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If a message has been encoded using RPCSEC_GSS, the server is
maintaining a window of sequence numbers that it considers valid.
The client should normally be tracking that window, and needs to
verify that the sequence number used by the message being transmitted
still lies inside the window of validity.

So far, we've been able to assume this condition would be realised
automatically, since the client has been encoding the message only
after taking the socket lock. Once we change that condition, we
will need the explicit check.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Trond Myklebust
2018-08-14 13:50:21 -04:00
parent 9ee94d3ed6
commit 3021a5bbbf
6 changed files with 64 additions and 0 deletions
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41
net/sunrpc/auth_gss/auth_gss.c
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@@ -1984,6 +1984,46 @@ gss_unwrap_req_decode(kxdrdproc_t decode, struct rpc_rqst *rqstp,
return decode(rqstp, &xdr, obj);
}
static bool
gss_seq_is_newer(u32 new, u32 old)
{
return (s32)(new - old) > 0;
}
static bool
gss_xmit_need_reencode(struct rpc_task *task)
{
struct rpc_rqst *req = task->tk_rqstp;
struct rpc_cred *cred = req->rq_cred;
struct gss_cl_ctx *ctx = gss_cred_get_ctx(cred);
u32 win, seq_xmit;
bool ret = true;
if (!ctx)
return true;
if (gss_seq_is_newer(req->rq_seqno, READ_ONCE(ctx->gc_seq)))
goto out;
seq_xmit = READ_ONCE(ctx->gc_seq_xmit);
while (gss_seq_is_newer(req->rq_seqno, seq_xmit)) {
u32 tmp = seq_xmit;
seq_xmit = cmpxchg(&ctx->gc_seq_xmit, tmp, req->rq_seqno);
if (seq_xmit == tmp) {
ret = false;
goto out;
}
}
win = ctx->gc_win;
if (win > 0)
ret = !gss_seq_is_newer(req->rq_seqno, seq_xmit - win);
out:
gss_put_ctx(ctx);
return ret;
}
static int
gss_unwrap_resp(struct rpc_task *task,
kxdrdproc_t decode, void *rqstp, __be32 *p, void *obj)
@@ -2052,6 +2092,7 @@ static const struct rpc_credops gss_credops = {
.crunwrap_resp = gss_unwrap_resp,
.crkey_timeout = gss_key_timeout,
.crstringify_acceptor = gss_stringify_acceptor,
.crneed_reencode = gss_xmit_need_reencode,
};
static const struct rpc_credops gss_nullops = {