/************************************************* * KeyUsage Source File * * (C) 1999-2006 The Botan Project * *************************************************/ #include #include #include #include namespace Botan { namespace BER { /************************************************* * Decode a BER encoded KeyUsage * *************************************************/ void decode(BER_Decoder& source, Key_Constraints& key_usage) { BER_Object obj = source.get_next_object(); if(obj.type_tag != BIT_STRING || obj.class_tag != UNIVERSAL) throw BER_Bad_Tag("Bad tag for usage constraint", obj.type_tag, obj.class_tag); if(obj.value.size() != 2 && obj.value.size() != 3) throw BER_Decoding_Error("Bad size for BITSTRING in usage constraint"); if(obj.value[0] >= 8) throw BER_Decoding_Error("Invalid unused bits in usage constraint"); const byte mask = (0xFF << obj.value[0]); obj.value[obj.value.size()-1] &= mask; u16bit usage = 0; for(u32bit j = 1; j != obj.value.size(); ++j) usage = (obj.value[j] << 8) | usage; key_usage = Key_Constraints(usage); } } }