| package com.android.hotspot2.asn1; |
| |
| import java.nio.ByteBuffer; |
| import java.util.Collection; |
| import java.util.HashMap; |
| import java.util.Map; |
| |
| public class Asn1Decoder { |
| public static final int TAG_UNIVZERO = 0x00; |
| public static final int TAG_BOOLEAN = 0x01; |
| public static final int TAG_INTEGER = 0x02; |
| public static final int TAG_BITSTRING = 0x03; |
| public static final int TAG_OCTET_STRING = 0x04; |
| public static final int TAG_NULL = 0x05; |
| public static final int TAG_OID = 0x06; |
| public static final int TAG_ObjectDescriptor = 0x07; |
| public static final int TAG_EXTERNAL = 0x08; |
| public static final int TAG_REAL = 0x09; |
| public static final int TAG_ENUMERATED = 0x0a; |
| public static final int TAG_UTF8String = 0x0c; // * (*) are X.509 DirectoryString's |
| public static final int TAG_RelativeOID = 0x0d; |
| public static final int TAG_SEQ = 0x10; // 30 if constructed |
| public static final int TAG_SET = 0x11; |
| public static final int TAG_NumericString = 0x12; // [UNIVERSAL 18] |
| public static final int TAG_PrintableString = 0x13; // * [UNIVERSAL 19] |
| public static final int TAG_T61String = 0x14; // * TeletexString [UNIVERSAL 20] |
| public static final int TAG_VideotexString = 0x15; // [UNIVERSAL 21] |
| public static final int TAG_IA5String = 0x16; // [UNIVERSAL 22] |
| public static final int TAG_UTCTime = 0x17; |
| public static final int TAG_GeneralizedTime = 0x18; |
| public static final int TAG_GraphicString = 0x19; // [UNIVERSAL 25] |
| public static final int TAG_VisibleString = 0x1a; // ISO64String [UNIVERSAL 26] |
| public static final int TAG_GeneralString = 0x1b; // [UNIVERSAL 27] |
| public static final int TAG_UniversalString = 0x1c; // * [UNIVERSAL 28] |
| public static final int TAG_BMPString = 0x1e; // * [UNIVERSAL 30] |
| |
| public static final int IntOverflow = 0xffff0000; |
| public static final int MoreBit = 0x80; |
| public static final int MoreData = 0x7f; |
| public static final int ConstructedBit = 0x20; |
| public static final int ClassShift = 6; |
| public static final int ClassMask = 0x3; |
| public static final int MoreWidth = 7; |
| public static final int ByteWidth = 8; |
| public static final int ByteMask = 0xff; |
| public static final int ContinuationTag = 31; |
| |
| public static final int IndefiniteLength = -1; |
| |
| private static final Map<Integer, Asn1Tag> sTagMap = new HashMap<>(); |
| |
| static { |
| sTagMap.put(TAG_UNIVZERO, Asn1Tag.UNIVZERO); |
| sTagMap.put(TAG_BOOLEAN, Asn1Tag.BOOLEAN); |
| sTagMap.put(TAG_INTEGER, Asn1Tag.INTEGER); |
| sTagMap.put(TAG_BITSTRING, Asn1Tag.BITSTRING); |
| sTagMap.put(TAG_OCTET_STRING, Asn1Tag.OCTET_STRING); |
| sTagMap.put(TAG_NULL, Asn1Tag.NULL); |
| sTagMap.put(TAG_OID, Asn1Tag.OID); |
| sTagMap.put(TAG_ObjectDescriptor, Asn1Tag.ObjectDescriptor); |
| sTagMap.put(TAG_EXTERNAL, Asn1Tag.EXTERNAL); |
| sTagMap.put(TAG_REAL, Asn1Tag.REAL); |
| sTagMap.put(TAG_ENUMERATED, Asn1Tag.ENUMERATED); |
| sTagMap.put(TAG_UTF8String, Asn1Tag.UTF8String); |
| sTagMap.put(TAG_RelativeOID, Asn1Tag.RelativeOID); |
| sTagMap.put(TAG_SEQ, Asn1Tag.SEQUENCE); |
| sTagMap.put(TAG_SET, Asn1Tag.SET); |
| sTagMap.put(TAG_NumericString, Asn1Tag.NumericString); |
| sTagMap.put(TAG_PrintableString, Asn1Tag.PrintableString); |
| sTagMap.put(TAG_T61String, Asn1Tag.T61String); |
| sTagMap.put(TAG_VideotexString, Asn1Tag.VideotexString); |
| sTagMap.put(TAG_IA5String, Asn1Tag.IA5String); |
| sTagMap.put(TAG_UTCTime, Asn1Tag.UTCTime); |
| sTagMap.put(TAG_GeneralizedTime, Asn1Tag.GeneralizedTime); |
| sTagMap.put(TAG_GraphicString, Asn1Tag.GraphicString); |
| sTagMap.put(TAG_VisibleString, Asn1Tag.VisibleString); |
| sTagMap.put(TAG_GeneralString, Asn1Tag.GeneralString); |
| sTagMap.put(TAG_UniversalString, Asn1Tag.UniversalString); |
| sTagMap.put(TAG_BMPString, Asn1Tag.BMPString); |
| } |
| |
| public static Asn1Tag mapTag(int tag) { |
| return sTagMap.get(tag); |
| } |
| |
| public static Collection<Asn1Object> decode(ByteBuffer data) throws DecodeException { |
| Asn1Constructed root = |
| new Asn1Constructed(0, null, data.remaining(), data, data.position()); |
| decode(0, root); |
| return root.getChildren(); |
| } |
| |
| private static void decode(int level, Asn1Constructed parent) throws DecodeException { |
| ByteBuffer data = parent.getPayload(); |
| while (data.hasRemaining()) { |
| int tagPosition = data.position(); |
| int propMask = data.get(tagPosition) & ByteMask; |
| if (propMask == 0 && parent.isIndefiniteLength() && data.get(tagPosition + 1) == 0) { |
| parent.setEndOfData(tagPosition); |
| return; |
| } |
| Asn1Class asn1Class = Asn1Class.values()[(propMask >> ClassShift) & ClassMask]; |
| boolean constructed = (propMask & ConstructedBit) != 0; |
| |
| int tag = decodeTag(data); |
| int length = decodeLength(data); |
| |
| if (constructed) { |
| ByteBuffer payload = peelOff(data, length); |
| Asn1Constructed root = |
| new Asn1Constructed(tag, asn1Class, length, payload, tagPosition); |
| decode(level + 1, root); |
| if (length == IndefiniteLength) { |
| data.position(root.getEndOfData() + 2); // advance past '00' |
| } |
| parent.addChild(root); |
| } else { |
| if (asn1Class != Asn1Class.Universal) { |
| parent.addChild(new Asn1Octets(tag, asn1Class, length, data)); |
| } else { |
| parent.addChild(buildScalar(tag, asn1Class, length, data)); |
| } |
| } |
| } |
| } |
| |
| private static ByteBuffer peelOff(ByteBuffer base, int length) { |
| ByteBuffer copy = base.duplicate(); |
| if (length == IndefiniteLength) { |
| return copy; |
| } |
| copy.limit(copy.position() + length); |
| base.position(base.position() + length); |
| return copy; |
| } |
| |
| private static Asn1Object buildScalar(int tag, Asn1Class asn1Class, int length, ByteBuffer data) |
| throws DecodeException { |
| switch (tag) { |
| case TAG_BOOLEAN: |
| return new Asn1Boolean(tag, asn1Class, length, data); |
| case TAG_INTEGER: |
| case TAG_ENUMERATED: |
| return new Asn1Integer(tag, asn1Class, length, data); |
| case TAG_BITSTRING: |
| int bitResidual = data.get() & ByteMask; |
| return new Asn1Octets(tag, asn1Class, length, data, bitResidual); |
| case TAG_OCTET_STRING: |
| return new Asn1Octets(tag, asn1Class, length, data); |
| case TAG_OID: |
| return new Asn1Oid(tag, asn1Class, length, data); |
| case TAG_UTF8String: |
| case TAG_NumericString: |
| case TAG_PrintableString: |
| case TAG_T61String: |
| case TAG_VideotexString: |
| case TAG_IA5String: |
| case TAG_GraphicString: |
| case TAG_VisibleString: |
| case TAG_GeneralString: |
| case TAG_UniversalString: |
| case TAG_BMPString: |
| return new Asn1String(tag, asn1Class, length, data); |
| case TAG_GeneralizedTime: |
| case TAG_UTCTime: |
| // Should really be a dedicated time object |
| return new Asn1String(tag, asn1Class, length, data); |
| default: |
| return new Asn1Octets(tag, asn1Class, length, data); |
| } |
| } |
| |
| private static int decodeTag(ByteBuffer data) throws DecodeException { |
| int tag; |
| byte tag0 = data.get(); |
| |
| if ((tag = (tag0 & ContinuationTag)) == ContinuationTag) { |
| int tagByte; |
| tag = 0; |
| while (((tagByte = data.get() & ByteMask) & MoreBit) != 0) { |
| tag = (tag << MoreWidth) | (tagByte & MoreData); |
| if ((tag & IntOverflow) != 0) |
| throw new DecodeException("Tag overflow", data.position()); |
| } |
| tag = (tag << MoreWidth) | tagByte; |
| } |
| return tag; |
| } |
| |
| private static int decodeLength(ByteBuffer data) throws DecodeException { |
| int length; |
| int lenlen = data.get() & ByteMask; |
| |
| if ((lenlen & MoreBit) == 0) // One byte encoding |
| length = lenlen; |
| else { |
| lenlen &= MoreData; |
| if (lenlen == 0) { |
| return IndefiniteLength; |
| } |
| length = 0; |
| while (lenlen-- > 0) { |
| length = (length << ByteWidth) | (data.get() & ByteMask); |
| if ((length & IntOverflow) != 0 && lenlen > 0) |
| throw new DecodeException("Length overflow", data.position()); |
| } |
| } |
| return length; |
| } |
| |
| } |
