1 /*
2  * Copyright (C) 2006 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.android.internal.telephony.cat;
18 
19 import java.util.List;
20 
21 /**
22  * Class for representing BER-TLV objects.
23  *
24  * @see "ETSI TS 102 223 Annex C" for more information.
25  *
26  * {@hide}
27  */
28 class BerTlv {
29     private int mTag = BER_UNKNOWN_TAG;
30     private List<ComprehensionTlv> mCompTlvs = null;
31     private boolean mLengthValid = true;
32 
33     public static final int BER_UNKNOWN_TAG             = 0x00;
34     public static final int BER_PROACTIVE_COMMAND_TAG   = 0xd0;
35     public static final int BER_MENU_SELECTION_TAG      = 0xd3;
36     public static final int BER_EVENT_DOWNLOAD_TAG      = 0xd6;
37 
BerTlv(int tag, List<ComprehensionTlv> ctlvs, boolean lengthValid)38     private BerTlv(int tag, List<ComprehensionTlv> ctlvs, boolean lengthValid) {
39         mTag = tag;
40         mCompTlvs = ctlvs;
41         mLengthValid = lengthValid;
42     }
43 
44     /**
45      * Gets a list of ComprehensionTlv objects contained in this BER-TLV object.
46      *
47      * @return A list of COMPREHENSION-TLV object
48      */
getComprehensionTlvs()49     public List<ComprehensionTlv> getComprehensionTlvs() {
50         return mCompTlvs;
51     }
52 
53     /**
54      * Gets a tag id of the BER-TLV object.
55      *
56      * @return A tag integer.
57      */
getTag()58     public int getTag() {
59         return mTag;
60     }
61 
62     /**
63      * Gets if the length of the BER-TLV object is valid
64      *
65      * @return if length valid
66      */
isLengthValid()67      public boolean isLengthValid() {
68          return mLengthValid;
69      }
70 
71     /**
72      * Decodes a BER-TLV object from a byte array.
73      *
74      * @param data A byte array to decode from
75      * @return A BER-TLV object decoded
76      * @throws ResultException
77      */
decode(byte[] data)78     public static BerTlv decode(byte[] data) throws ResultException {
79         int curIndex = 0;
80         int endIndex = data.length;
81         int tag, length = 0;
82         boolean isLengthValid = true;
83 
84         try {
85             /* tag */
86             tag = data[curIndex++] & 0xff;
87             if (tag == BER_PROACTIVE_COMMAND_TAG) {
88                 /* length */
89                 int temp = data[curIndex++] & 0xff;
90                 if (temp < 0x80) {
91                     length = temp;
92                 } else if (temp == 0x81) {
93                     temp = data[curIndex++] & 0xff;
94                     if (temp < 0x80) {
95                         throw new ResultException(
96                                 ResultCode.CMD_DATA_NOT_UNDERSTOOD,
97                                 "length < 0x80 length=" + Integer.toHexString(length) +
98                                 " curIndex=" + curIndex + " endIndex=" + endIndex);
99 
100                     }
101                     length = temp;
102                 } else {
103                     throw new ResultException(
104                             ResultCode.CMD_DATA_NOT_UNDERSTOOD,
105                             "Expected first byte to be length or a length tag and < 0x81" +
106                             " byte= " + Integer.toHexString(temp) + " curIndex=" + curIndex +
107                             " endIndex=" + endIndex);
108                 }
109             } else {
110                 if (ComprehensionTlvTag.COMMAND_DETAILS.value() == (tag & ~0x80)) {
111                     tag = BER_UNKNOWN_TAG;
112                     curIndex = 0;
113                 }
114             }
115         } catch (IndexOutOfBoundsException e) {
116             throw new ResultException(ResultCode.REQUIRED_VALUES_MISSING,
117                     "IndexOutOfBoundsException " +
118                     " curIndex=" + curIndex + " endIndex=" + endIndex);
119         } catch (ResultException e) {
120             throw new ResultException(ResultCode.CMD_DATA_NOT_UNDERSTOOD, e.explanation());
121         }
122 
123         /* COMPREHENSION-TLVs */
124         if (endIndex - curIndex < length) {
125             throw new ResultException(ResultCode.CMD_DATA_NOT_UNDERSTOOD,
126                     "Command had extra data endIndex=" + endIndex + " curIndex=" + curIndex +
127                     " length=" + length);
128         }
129 
130         List<ComprehensionTlv> ctlvs = ComprehensionTlv.decodeMany(data,
131                 curIndex);
132 
133         if (tag == BER_PROACTIVE_COMMAND_TAG) {
134             int totalLength = 0;
135             for (ComprehensionTlv item : ctlvs) {
136                 int itemLength = item.getLength();
137                 if (itemLength >= 0x80 && itemLength <= 0xFF) {
138                     totalLength += itemLength + 3; //3: 'tag'(1 byte) and 'length'(2 bytes).
139                 } else if (itemLength >= 0 && itemLength < 0x80) {
140                     totalLength += itemLength + 2; //2: 'tag'(1 byte) and 'length'(1 byte).
141                 } else {
142                     isLengthValid = false;
143                     break;
144                 }
145             }
146 
147             // According to 3gpp11.14, chapter 6.10.6 "Length errors",
148 
149             // If the total lengths of the SIMPLE-TLV data objects are not
150             // consistent with the length given in the BER-TLV data object,
151             // then the whole BER-TLV data object shall be rejected. The
152             // result field in the TERMINAL RESPONSE shall have the error
153             // condition "Command data not understood by ME".
154             if (length != totalLength) {
155                 isLengthValid = false;
156             }
157         }
158 
159         return new BerTlv(tag, ctlvs, isLengthValid);
160     }
161 }
162