The length of the GSS MIC token need not be a multiple of four bytes.
It is then padded by XDR to a multiple of 4 B, but unwrap_integ_data()
would previously only trim mic.len + 4 B. The remaining up to three
bytes would then trigger a check in nfs4svc_decode_compoundargs(),
leading to a "garbage args" error and mount failure:
nfs4svc_decode_compoundargs: compound not properly padded!
nfsd: failed to decode arguments!
This would prevent older clients using the pre-RFC 4121 MIC format
(37-byte MIC including a 9-byte OID) from mounting exports from v3.9+
servers using krb5i.
The trimming was introduced by commit 4c190e2f913f ("sunrpc: trim off
trailing checksum before returning decrypted or integrity authenticated
buffer").
Signed-off-by: Tomáš Trnka <ttrnka@xxxxxxxxxxxx>
---
net/sunrpc/auth_gss/svcauth_gss.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/sunrpc/auth_gss/svcauth_gss.c
b/net/sunrpc/auth_gss/svcauth_gss.c
index 1095be9..4605dc7 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -857,8 +857,8 @@ unwrap_integ_data(struct svc_rqst *rqstp, struct xdr_buf
*buf, u32 seq, struct g
goto out;
if (svc_getnl(&buf->head[0]) != seq)
goto out;
- /* trim off the mic at the end before returning */
- xdr_buf_trim(buf, mic.len + 4);
+ /* trim off the mic and padding at the end before returning */
+ xdr_buf_trim(buf, round_up_to_quad(mic.len) + 4);
stat = 0;
out:
kfree(mic.data);
--
2.5.5
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