Haga que los botones laterales del mouse activen las teclas virtuales

Tengo un mouse con dos botones laterales.

evtest el resultado de xev y evtest para ambos botones:

xev

 EnterNotify event, serial 37, synthetic NO, window 0x4600001, root 0x306, subw 0x0, time 5663259, (11,69), root:(799,121), mode NotifyNormal, detail NotifyInferior, same_screen YES, focus YES, state 0 KeymapNotify event, serial 37, synthetic NO, window 0x0, keys: 6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 --------------------------------------------------------------------------- --------------------------------------------------------------------------- EnterNotify event, serial 37, synthetic NO, window 0x4600001, root 0x306, subw 0x4600002, time 5662311, (30,60), root:(818,112), mode NotifyUngrab, detail NotifyVirtual, same_screen YES, focus YES, state 0 KeymapNotify event, serial 37, synthetic NO, window 0x0, keys: 6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

evtest:

 Event: time 1420063746.029705, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90005 Event: time 1420063746.029705, type 1 (EV_KEY), code 276 (BTN_EXTRA), value 1 Event: time 1420063746.029705, -------------- SYN_REPORT ------------ Event: time 1420063746.165669, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90005 Event: time 1420063746.165669, type 1 (EV_KEY), code 276 (BTN_EXTRA), value 0 ------------------------------------------------------------------------------ ------------------------------------------------------------------------------ Event: time 1420063746.165669, -------------- SYN_REPORT ------------ Event: time 1420063747.373693, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90004 Event: time 1420063747.373693, type 1 (EV_KEY), code 275 (BTN_SIDE), value 1 Event: time 1420063747.373693, -------------- SYN_REPORT ------------ Event: time 1420063747.533689, type 4 (EV_MSC), code 4 (MSC_SCAN), value 90004 Event: time 1420063747.533689, type 1 (EV_KEY), code 275 (BTN_SIDE), value 0 

¿Cómo se podría abordar la asignación de estos botones a algunas teclas virtuales? Por ejemplo, ¿cómo se pueden asignar estos botones para que funcionen como back y forward ?