dschmidt commented on code in PR #3062: URL: https://github.com/apache/tika/pull/3062#discussion_r3869568459
########## tika-parsers/tika-parsers-standard/tika-parsers-standard-modules/tika-parser-audiovideo-module/src/main/java/org/apache/tika/parser/mp4/Mp4SampleEntries.java: ########## @@ -0,0 +1,172 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.tika.parser.mp4; + +import java.nio.charset.StandardCharsets; + +import org.apache.tika.io.EndianUtils; + +/** + * Walks the sample entries of a SampleDescriptionBox ('stsd') payload, shared + * by the sound and video handlers. The payload is 4 bytes version and flags, + * a 4 byte entry count, then one sample entry per count. Each entry is a box: + * a 32-bit size and a FourCC, where a size of 1 announces a 64-bit largesize + * and a size of 0 extends the entry to the end of the payload (ISO/IEC + * 14496-12, 4.2). + */ +final class Mp4SampleEntries { + + /** + * Size of the SampleEntry fields that follow the box header in every + * entry: 6 reserved bytes and the 2 byte data reference index. + */ + static final int SAMPLE_ENTRY_FIELDS = 8; + + interface Visitor { + /** + * @param fourCC the entry's FourCC, or null if it is not printable + * @param b the stsd payload + * @param start offset of the first byte after the entry's box header + * @param end offset one past the entry's last byte + */ + void entry(String fourCC, byte[] b, int start, int end); + } + + private Mp4SampleEntries() { + } + + static void walk(byte[] b, Visitor visitor) { + if (b.length < 8) { + return; + } + long entryCount = EndianUtils.getUIntBE(b, 4); + int pos = 8; + for (long i = 0; i < entryCount && pos + 8 <= b.length; i++) { + long size = EndianUtils.getUIntBE(b, pos); + int header = 8; + if (size == 1) { + //largesize: the 64-bit size follows the FourCC + if (pos + 16 > b.length) { + return; + } + //a value beyond 63 bits goes negative and fails the size check below + size = (EndianUtils.getUIntBE(b, pos + 8) << 32) | EndianUtils.getUIntBE(b, pos + 12); + header = 16; + } else if (size == 0) { + //the entry extends to the end of the box + size = b.length - pos; + } + if (size < header + SAMPLE_ENTRY_FIELDS || size > b.length - pos) { + return; + } + int end = pos + (int) size; + visitor.entry(printableFourCC(b, pos + 4), b, pos + header, end); + pos = end; + } + } + + /** + * Returns whether a sample entry FourCC marks a protected stream: 'drms' + * and 'drmi' (FairPlay) or 'enca' and 'encv' (ISO common encryption). + */ + static boolean isProtected(String fourCC) { + return "drms".equals(fourCC) || "enca".equals(fourCC) + || "encv".equals(fourCC) || "drmi".equals(fourCC); + } + + /** + * Looks up the original (unprotected) format of a protected sample entry: + * the ProtectionSchemeInfoBox 'sinf' among the entry's child boxes carries + * an OriginalFormatBox 'frma' whose payload is the codec FourCC that the + * protected format replaced (ISO/IEC 14496-12, 8.12). Returns null if + * there is none or it is not printable. + * + * @param pos offset of the entry's first child box + * @param end offset one past the entry's last byte + */ + static String originalFormat(byte[] b, int pos, int end) { + int sinf = findBox(b, pos, end, "sinf"); + if (sinf < 0) { + return null; + } + int frma = findBox(b, sinf + 8, boxEnd(b, sinf, end), "frma"); + if (frma < 0 || frma + 12 > end) { + return null; + } + return printableFourCC(b, frma + 8); + } Review Comment: Good catch, fixed: the frma box end is now checked against frma + 12, with a header-only frma regression test in Mp4SampleEntriesTest. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
