[PATCH 3/3] nfs-utils: gssd: handle KRB5_AP_ERR_BAD_INTEGRITY for user credentials

[Olga Kornievskaia <olga.kornievskaia@xxxxxxxxx>]

From: Olga Kornievskaia <kolga@xxxxxxxxxx>

Unlike the machine credential case, we can't throw away the ticket
cache and use the keytab to renew the credentials. Instead, we
need to remove the service ticket for the server that returned
KRB5_AP_ERR_BAD_INTEGRITY and try again.

Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx>
---
 utils/gssd/gssd_proc.c |  2 ++
 utils/gssd/krb5_util.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 utils/gssd/krb5_util.h |  1 +
 3 files changed, 45 insertions(+)

diff --git a/utils/gssd/gssd_proc.c b/utils/gssd/gssd_proc.c
index e5cc1d98..a96647df 100644
--- a/utils/gssd/gssd_proc.c
+++ b/utils/gssd/gssd_proc.c
@@ -419,6 +419,8 @@ create_auth_rpc_client(struct clnt_info *clp,
 			if (cred == GSS_C_NO_CREDENTIAL)
 				retval = gssd_refresh_krb5_machine_credential(clp->servername,
 					"*", NULL, 1);
+			else
+				retval = gssd_k5_remove_bad_service_cred(clp->servername);
 			if (!retval) {
 				auth = authgss_create_default(rpc_clnt, tgtname,
 						&sec);
diff --git a/utils/gssd/krb5_util.c b/utils/gssd/krb5_util.c
index f6ce1fec..6f66ef4f 100644
--- a/utils/gssd/krb5_util.c
+++ b/utils/gssd/krb5_util.c
@@ -1553,6 +1553,48 @@ gssd_acquire_user_cred(gss_cred_id_t *gss_cred)
 	return ret;
 }
 
+/* Removed a service ticket for nfs/<name> from the ticket cache
+ */
+int
+gssd_k5_remove_bad_service_cred(char *name)
+{
+        krb5_creds in_creds, out_creds;
+        krb5_error_code ret;
+        krb5_context context;
+        krb5_ccache cache;
+        krb5_principal principal;
+        int retflags = KRB5_TC_MATCH_SRV_NAMEONLY;
+        char srvname[1024];
+
+        ret = krb5_init_context(&context);
+        if (ret)
+                goto out_cred;
+        ret = krb5_cc_default(context, &cache);
+        if (ret)
+                goto out_free_context;
+        ret = krb5_cc_get_principal(context, cache, &principal);
+        if (ret)
+                goto out_close_cache;
+        memset(&in_creds, 0, sizeof(in_creds));
+        in_creds.client = principal;
+        sprintf(srvname, "nfs/%s", name);
+        ret = krb5_parse_name(context, srvname, &in_creds.server);
+        if (ret)
+                goto out_free_principal;
+        ret = krb5_cc_retrieve_cred(context, cache, retflags, &in_creds, &out_creds);
+        if (ret)
+                goto out_free_principal;
+        ret = krb5_cc_remove_cred(context, cache, 0, &out_creds);
+out_free_principal:
+        krb5_free_principal(context, principal);
+out_close_cache:
+        krb5_cc_close(context, cache);
+out_free_context:
+        krb5_free_context(context);
+out_cred:
+        return ret;
+}
+
 #ifdef HAVE_SET_ALLOWABLE_ENCTYPES
 /*
  * this routine obtains a credentials handle via gss_acquire_cred()
diff --git a/utils/gssd/krb5_util.h b/utils/gssd/krb5_util.h
index 62c91a0e..7ef87018 100644
--- a/utils/gssd/krb5_util.h
+++ b/utils/gssd/krb5_util.h
@@ -22,6 +22,7 @@ char *gssd_k5_err_msg(krb5_context context, krb5_error_code code);
 void gssd_k5_get_default_realm(char **def_realm);
 
 int gssd_acquire_user_cred(gss_cred_id_t *gss_cred);
+int gssd_k5_remove_bad_service_cred(char *srvname);
 
 #ifdef HAVE_SET_ALLOWABLE_ENCTYPES
 extern int limit_to_legacy_enctypes;
-- 
2.39.1