diff --git a/doc/management-notes.txt b/doc/management-notes.txt
index 29f2da75..a3c09b78 100644
--- a/doc/management-notes.txt
+++ b/doc/management-notes.txt
@@ -592,6 +592,53 @@ interface to approve client connections.
 CID,KID -- client ID and Key ID.  See documentation for ">CLIENT:"
 notification for more info.
 
+COMMAND -- client-sso-auth  (OpenVPN 2.5 or higher)
+----------------------------------------------------
+
+Instruct OpenVPN server to send AUTH_PENDING and INFO_PRE signal
+a single sign on url to the client.
+
+  client-sso-auth {CID} {EXTRA}
+
+The server will send AUTH_PENDING and INFO_PRE,{EXTRA} to the client.
+The client is expected to inform the user that authentication is pending and
+display the extra information.
+For the openurl SSO method EXTRA has the form OPEN_URL:url
+and an example is:
+
+  client-sso-auth 17 "OPENURL:https://examples.com/do_web_auth"
+  
+and client should ask to the user to open the URL to continue. 
+
+For the OpenVPN server this is stateless operation and needs to be
+followed by a client-deny/client-auth[-nt] command (that is the result of the
+out of band authentication).
+
+The other implemented method is challenge/response (crtext). This uses
+the same format as the user and password bases challenge respsonse with
+AUTH_FAILED but omits the session id and username.
+
+   client-sso-auth 18 "CR_TEXT:<flags>:<challenge_text>"
+
+For exmaple:
+
+   client-sso-auth 18 "CR_TEXT:R,E:Please enter token PIN"
+
+The client should present the user the challenge and follow up
+with cr-response command.
+
+See the section >CLIENT,CR_RESPONSE for the client response.
+
+A client should announce its support for these methods with
+the IV_SSO variable seperated by comma. E.g., in the configuration file
+
+    setenv IV_SSO openurl,crtext
+
+A server should check wether these methods are supported by
+examining IV_SSO and otherwise fall back to classic challenge
+response protocol or sending a AUTH_FAILED message that points
+out missing client support.
+
 COMMAND -- client-deny  (OpenVPN 2.1 or higher)
 -----------------------------------------------
 
diff --git a/src/openvpn/manage.c b/src/openvpn/manage.c
index 8ec90bb1..ffd48445 100644
--- a/src/openvpn/manage.c
+++ b/src/openvpn/manage.c
@@ -105,6 +105,8 @@ man_help(void)
     msg(M_CLIENT, "client-auth-nt CID KID : Authenticate client-id/key-id CID/KID");
     msg(M_CLIENT, "client-deny CID KID R [CR] : Deny auth client-id/key-id CID/KID with log reason");
     msg(M_CLIENT, "                             text R and optional client reason text CR");
+    msg(M_CLIENT, "client-sso-auth CID MSG : Instruct OpenVPN to send AUTH_PENDING and INFO_PRE msg"
+                  "                          to the client and wait for a final client-auth/client-deny");
     msg(M_CLIENT, "client-kill CID [M]    : Kill client instance CID with message M (def=RESTART)");
     msg(M_CLIENT, "env-filter [level]     : Set env-var filter level");
 #ifdef MANAGEMENT_PF
@@ -1000,6 +1002,33 @@ parse_kid(const char *str, unsigned int *kid)
         return false;
     }
 }
+static void
+man_client_sso_auth(struct management *man, const char *cid_str, const char *extra)
+{
+    unsigned long cid = 0;
+    if (parse_cid(cid_str, &cid))
+    {
+        if (man->persist.callback.client_sso)
+        {
+            bool ret = (*man->persist.callback.client_sso)
+                           (man->persist.callback.arg, cid, extra);
+
+            if (ret)
+            {
+                msg(M_CLIENT, "SUCCESS: client-sso-auth command succeeded");
+            }
+            else
+            {
+                msg(M_CLIENT, "SUCCESS: client-sso-auth command failed."
+                              " Extra paramter might be too long");
+            }
+        }
+        else
+        {
+            msg(M_CLIENT, "ERROR: The client-deny command is not supported by the current daemon mode");
+        }
+    }
+}
 
 static void
 man_client_auth(struct management *man, const char *cid_str, const char *kid_str, const bool extra)
@@ -1539,6 +1568,13 @@ man_dispatch_command(struct management *man, struct status_output *so, const cha
             man_client_auth(man, p[1], p[2], true);
         }
     }
+    else if (streq(p[0], "client-sso-auth"))
+    {
+        if (man_need(man, p, 2, 0))
+        {
+            man_client_sso_auth(man, p[1], p[2]);
+        }
+    }
 #ifdef MANAGEMENT_PF
     else if (streq(p[0], "client-pf"))
     {
diff --git a/src/openvpn/manage.h b/src/openvpn/manage.h
index 6a749725..ff6b6737 100644
--- a/src/openvpn/manage.h
+++ b/src/openvpn/manage.h
@@ -174,6 +174,9 @@ struct management_callback
                          const char *reason,
                          const char *client_reason,
                          struct buffer_list *cc_config); /* ownership transferred */
+    bool (*client_sso) (void *arg,
+                        const unsigned long cid,
+                        const char *url);
     char *(*get_peer_info) (void *arg, const unsigned long cid);
 #endif
 #ifdef MANAGEMENT_PF
diff --git a/src/openvpn/multi.c b/src/openvpn/multi.c
index d1f9c72e..03e03aff 100644
--- a/src/openvpn/multi.c
+++ b/src/openvpn/multi.c
@@ -3253,6 +3253,24 @@ management_kill_by_cid(void *arg, const unsigned long cid, const char *kill_msg)
     }
 }
 
+static bool
+management_client_sso(void *arg,
+        const unsigned long cid,
+        const char *extra)
+{
+    struct multi_context *m = (struct multi_context *) arg;
+    struct multi_instance *mi = lookup_by_cid(m, cid);
+    if (mi)
+    {
+        /* sends INFO_PRE and AUTH_PENDING messages to client */
+        bool ret = send_sso_messages(&mi->context, extra);
+        multi_schedule_context_wakeup(m, mi);
+        return ret;
+    }
+    return false;
+}
+
+
 static bool
 management_client_auth(void *arg,
                        const unsigned long cid,
@@ -3360,6 +3378,7 @@ init_management_callback_multi(struct multi_context *m)
 #ifdef MANAGEMENT_DEF_AUTH
         cb.kill_by_cid = management_kill_by_cid;
         cb.client_auth = management_client_auth;
+        cb.client_sso = management_client_sso;
         cb.get_peer_info = management_get_peer_info;
 #endif
 #ifdef MANAGEMENT_PF
diff --git a/src/openvpn/push.c b/src/openvpn/push.c
index 3b568b9b..0cec692c 100644
--- a/src/openvpn/push.c
+++ b/src/openvpn/push.c
@@ -287,6 +287,30 @@ send_auth_failed(struct context *c, const char *client_reason)
     gc_free(&gc);
 }
 
+bool
+send_sso_messages(struct context *c, const char* extra)
+{
+    send_control_channel_string(c, "AUTH_PENDING", D_PUSH);
+
+    static const char info_pre[] = "INFO_PRE,";
+
+
+    size_t len = strlen(extra)+1 + sizeof(info_pre);
+    if (len > PUSH_BUNDLE_SIZE)
+    {
+        return false;
+    }
+    struct gc_arena gc = gc_new();
+
+    struct buffer buf = alloc_buf_gc(len, &gc);
+    buf_printf(&buf, info_pre);
+    buf_printf(&buf, "%s", extra);
+    send_control_channel_string(c, BSTR(&buf), D_PUSH);
+
+    gc_free(&gc);
+    return true;
+}
+
 /*
  * Send restart message from server to client.
  */
diff --git a/src/openvpn/push.h b/src/openvpn/push.h
index 3f5079f3..a15aa58c 100644
--- a/src/openvpn/push.h
+++ b/src/openvpn/push.h
@@ -72,6 +72,8 @@ void remove_iroutes_from_push_route_list(struct options *o);
 
 void send_auth_failed(struct context *c, const char *client_reason);
 
+bool send_sso_messages(struct context *c, const char *url);
+
 void send_restart(struct context *c, const char *kill_msg);
 
 #endif
