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; } }