SUNRPC: Improve Kerberos confounder generation

Other common Kerberos implementations use a fully random confounder
for encryption. The reason for this is explained in the new comment
added by this patch. The current get_random_bytes() implementation
does not exhaust system entropy.

Since confounder generation is part of Kerberos itself rather than
the GSS-API Kerberos mechanism, the function is renamed and moved.

Note that light top-down analysis shows that the SHA-1 transform
is by far the most CPU-intensive part of encryption. Thus we do not
expect this change to result in a significant performance impact.
However, eventually it might be necessary to generate an independent
stream of confounders for each Kerberos context to help improve I/O
parallelism.

Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

1 files changed, 7 insertions, 8 deletions

diff --git a/net/sunrpc/auth_gss/gss_krb5_mech.c b/net/sunrpc/auth_gss/gss_krb5_mech.c
index 08a86ece665e..76a0d83fe500 100644
--- a/net/sunrpc/auth_gss/gss_krb5_mech.c
+++ b/net/sunrpc/auth_gss/gss_krb5_mech.c
@@ -550,16 +550,15 @@ gss_import_sec_context_kerberos(const void *p, size_t len,
 		ret = gss_import_v1_context(p, end, ctx);
 	else
 		ret = gss_import_v2_context(p, end, ctx, gfp_mask);
-
-	if (ret == 0) {
-		ctx_id->internal_ctx_id = ctx;
-		if (endtime)
-			*endtime = ctx->endtime;
-	} else
+	if (ret) {
 		kfree(ctx);
+		return ret;
+	}
 
-	dprintk("RPC:       %s: returning %d\n", __func__, ret);
-	return ret;
+	ctx_id->internal_ctx_id = ctx;
+	if (endtime)
+		*endtime = ctx->endtime;
+	return 0;
 }
 
 static void