s4:heimdal Add hooks to check with the DB before we allow s4u2self

This allows us to resolve multiple forms of a name, allowing for
example machine$@REALM to get an S4U2Self ticket for
host/machine@REALM.

Andrew Bartlett

Signed-off-by: Love Hornquist Astrand <lha@h5l.org>

diff --git a/kdc/krb5tgs.c b/kdc/krb5tgs.c
index 1da90c2071f57ca88cb4cbf7d07a6896ea5edc92..30936e075392dd86627b5557461f19d46d4e38ce 100644 (file)
--- a/kdc/krb5tgs.c
+++ b/kdc/krb5tgs.c
@@ -494,7 +494,7 @@ check_tgs_flags(krb5_context context,
 }
 
 /*
- *
+ * Determine if constrained delegation is allowed from this client to this server
  */
 
 static krb5_error_code
@@ -536,6 +536,36 @@ check_constrained_delegation(krb5_context context,
     return ret;
 }
 
+/*
+ * Determine if s4u2self is allowed from this client to this server
+ *
+ * For example, regardless of the principal being impersonated, if the
+ * 'client' and 'server' are the same, then it's safe.
+ */
+
+static krb5_error_code
+check_s4u2self(krb5_context context,
+              krb5_kdc_configuration *config,
+              HDB *clientdb,
+              hdb_entry_ex *client,
+              krb5_const_principal server)
+{
+    krb5_error_code ret;
+
+    /* if client does a s4u2self to itself, that ok */
+    if (krb5_principal_compare(context, client->entry.principal, server) == TRUE)
+       return 0;
+
+    if (clientdb->hdb_check_s4u2self) {
+       ret = clientdb->hdb_check_s4u2self(context, clientdb, client, server);
+       if (ret == 0)
+           return 0;
+    } else {
+       ret = KRB5KDC_ERR_BADOPTION;
+    }
+    return ret;
+}
+
 /*
  *
  */
@@ -1793,13 +1823,13 @@ server_lookup:
             * Check that service doing the impersonating is
             * requesting a ticket to it-self.
             */
-           if (krb5_principal_compare(context, cp, sp) != TRUE) {
+           ret = check_s4u2self(context, config, clientdb, client, sp);
+           if (ret) {
                kdc_log(context, config, 0, "S4U2Self: %s is not allowed "
-                       "to impersonate some other user "
+                       "to impersonate to service "
                        "(tried for user %s to service %s)",
                        cpn, selfcpn, spn);
                free(selfcpn);
-               ret = KRB5KDC_ERR_BADOPTION; /* ? */
                goto out;
            }
 

diff --git a/lib/hdb/hdb.h b/lib/hdb/hdb.h
index 52373eb1d795aa174e3e3bbde0619023ca2969c7..469a330812785b076eef79bd6440b9eb44200ea5 100644 (file)
--- a/lib/hdb/hdb.h
+++ b/lib/hdb/hdb.h
@@ -235,9 +235,14 @@ typedef struct HDB{
      * Check if this name is an alias for the supplied client for PKINIT userPrinicpalName logins
      */
     krb5_error_code (*hdb_check_pkinit_ms_upn_match)(krb5_context, struct HDB *, hdb_entry_ex *, krb5_const_principal);
+
+    /**
+     * Check if s4u2self is allowed from this client to this server
+     */
+    krb5_error_code (*hdb_check_s4u2self)(krb5_context, struct HDB *, hdb_entry_ex *, krb5_const_principal);
 }HDB;
 
-#define HDB_INTERFACE_VERSION  6
+#define HDB_INTERFACE_VERSION  7
 
 struct hdb_so_method {
     int version;