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package com.android.javacard.keymaster;
import javacard.framework.ISO7816;
import javacard.framework.ISOException;
import javacard.framework.Util;
/**
* KMSemanticTag corresponds to CBOR type of tagged item. The structure is defined as struct{byte
* SEMANTIC_TAG_TYPE; short length; tag, short ptr }. Tag is INTEGER_TYPE and the possible values
* are defined here https://www.rfc-editor.org/rfc/rfc7049#section-2.4
*/
public class KMSemanticTag extends KMType {
public static final short COSE_MAC_SEMANTIC_TAG = (short) 0x0011;
public static final short ROT_SEMANTIC_TAG = (short) 0x9C41;
private static KMSemanticTag prototype;
private KMSemanticTag() {}
private static KMSemanticTag proto(short ptr) {
if (prototype == null) {
prototype = new KMSemanticTag();
}
instanceTable[KM_SEMANTIC_TAG_OFFSET] = ptr;
return prototype;
}
// pointer to an empty instance used as expression
public static short exp(short valuePtr) {
short ptr = KMType.instance(SEMANTIC_TAG_TYPE, (short) 6);
Util.setShort(heap, (short) (ptr + TLV_HEADER_SIZE + 2), KMInteger.exp());
Util.setShort(heap, (short) (ptr + TLV_HEADER_SIZE + 4), valuePtr);
return ptr;
}
public static KMSemanticTag cast(short ptr) {
if (heap[ptr] != SEMANTIC_TAG_TYPE) {
ISOException.throwIt(ISO7816.SW_CONDITIONS_NOT_SATISFIED);
}
return proto(ptr);
}
public static short instance(short tag, short value) {
if (!isSemanticTagSupported(tag)) {
ISOException.throwIt(ISO7816.SW_DATA_INVALID);
}
// The maximum tag size can be UINT32. Currently, we support
// only two tags which are short.
short ptr = KMType.instance(SEMANTIC_TAG_TYPE, (short) 6);
Util.setShort(heap, (short) (ptr + TLV_HEADER_SIZE + 2), tag);
Util.setShort(heap, (short) (ptr + TLV_HEADER_SIZE + 4), value);
return ptr;
}
private static boolean isSemanticTagSupported(short tag) {
tag = KMInteger.cast(tag).getShort();
switch (tag) {
case COSE_MAC_SEMANTIC_TAG:
case ROT_SEMANTIC_TAG:
break;
default:
return false;
}
return true;
}
public short length() {
return Util.getShort(heap, (short) (instanceTable[KM_SEMANTIC_TAG_OFFSET] + 1));
}
public short getKeyPtr() {
return Util.getShort(
heap, (short) (instanceTable[KM_SEMANTIC_TAG_OFFSET] + TLV_HEADER_SIZE + 2));
}
public short getValuePtr() {
return Util.getShort(
heap, (short) (instanceTable[KM_SEMANTIC_TAG_OFFSET] + TLV_HEADER_SIZE + 4));
}
}
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