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new 2f78da1e50 TIKA_4782 -- allow print ticket headers in pdf detection
(#3027)
2f78da1e50 is described below
commit 2f78da1e50c1437245da5e8b241f4bed0b6d8936
Author: Tim Allison <[email protected]>
AuthorDate: Sun Aug 16 21:43:44 2026 -0400
TIKA_4782 -- allow print ticket headers in pdf detection (#3027)
---
CHANGES.txt | 5 +
.../org/apache/tika/mime/tika-mimetypes.xml | 10 ++
.../org/apache/tika/mime/PdfDetectionTest.java | 172 +++++++++++++++++++++
.../mime/test-pdf-with-print-ticket-header.pdf | Bin 0 -> 36766 bytes
4 files changed, 187 insertions(+)
diff --git a/CHANGES.txt b/CHANGES.txt
index d736d877e8..5ae4bb52ed 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -151,6 +151,11 @@ Release 4.0.0 - ???
closes its connection and recycles the per-client worker, so a
pooled client cannot go back to the queue dirty (TIKA-4815).
+ * PDFs whose %PDF- header is preceded by a print-composition job ticket are
+ no longer detected as text/x-matlab. Up to 50 %% comment or blank lines of
+ up to 150 characters, and nothing else, may now precede the header; the
+ TIKA-3328 rule this extends only reached 512 bytes (TIKA-4782).
+
Release 4.0.0-beta-1 - 6/29/2026
diff --git
a/tika-core/src/main/resources/org/apache/tika/mime/tika-mimetypes.xml
b/tika-core/src/main/resources/org/apache/tika/mime/tika-mimetypes.xml
index 6cd798ca80..a2f4374f4f 100644
--- a/tika-core/src/main/resources/org/apache/tika/mime/tika-mimetypes.xml
+++ b/tika-core/src/main/resources/org/apache/tika/mime/tika-mimetypes.xml
@@ -855,6 +855,16 @@
<match value="%PDF-2." type="string" offset="1:512"/>
</match>
</magic>
+ <magic priority="40">
+ <!-- Print-composition systems prepend a job ticket of %% comments that
can run well
+ past the 512-byte window above (TIKA-4782). Up to 50 %% comment or
blank lines of up
+ to 150 characters, and nothing else, may precede the header. 50x150 is
deliberate:
+ the worst case stays inside the first 8K, which is all MagicDetector
feeds a regex,
+ so every prefix within those bounds really is reachable.
+ Every quantifier is bounded and the group is atomic, so this cannot
backtrack: without
+ the (?> a hostile CRLF run splits exponentially and hangs detection.
Keep it that way. -->
+ <match
value="(?>(?:%%[^\\r\\n]{0,148})?(?:\\r\\n|[\\r\\n])){1,50}%PDF-[12]\\."
type="regex" offset="0"/>
+ </magic>
<magic priority="20">
<!-- Low priority match for %PDF-#.# near the start of the file -->
<!-- Can trigger false positives, so set the priority rather low here -->
diff --git a/tika-core/src/test/java/org/apache/tika/mime/PdfDetectionTest.java
b/tika-core/src/test/java/org/apache/tika/mime/PdfDetectionTest.java
new file mode 100644
index 0000000000..3e5bd1f10b
--- /dev/null
+++ b/tika-core/src/test/java/org/apache/tika/mime/PdfDetectionTest.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.mime;
+
+import static java.nio.charset.StandardCharsets.ISO_8859_1;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTimeoutPreemptively;
+
+import java.io.InputStream;
+import java.time.Duration;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import org.apache.tika.io.TikaInputStream;
+import org.apache.tika.metadata.Metadata;
+import org.apache.tika.parser.ParseContext;
+
+/**
+ * Detection of PDFs whose {@code %PDF-} header is preceded by {@code %%}
comment
+ * lines, which would otherwise be claimed by the matlab {@code %%} magic.
+ *
+ * @see <a href="https://issues.apache.org/jira/browse/TIKA-3328";>TIKA-3328</a>
+ * @see <a href="https://issues.apache.org/jira/browse/TIKA-4782";>TIKA-4782</a>
+ */
+public class PdfDetectionTest {
+
+ private static final MediaType PDF = MediaType.application("pdf");
+
+ private static final MediaType MATLAB = MediaType.text("x-matlab");
+
+ private static final String PDF_BODY = "%PDF-1.7\r\n1 0 obj\r\n";
+
+ private static MimeTypes MIME_TYPES;
+
+ @BeforeAll
+ public static void setUp() {
+ MIME_TYPES = MimeTypes.getDefaultMimeTypes();
+ }
+
+ /**
+ * Print-shop job ticket ahead of the header; the {@code %PDF-} lands well
past
+ * the 512-byte window of the older TIKA-3328 rule.
+ */
+ @Test
+ public void testPrintTicketHeader() throws Exception {
+ try (InputStream in =
getClass().getResourceAsStream("test-pdf-with-print-ticket-header.pdf")) {
+ assertNotNull(in, "missing test file");
+ assertEquals(PDF, detect(in));
+ }
+ }
+
+ /**
+ * 10 and 50 lines of 60 push the header past the 512-byte window the
older rules
+ * can reach; 1 line keeps TIKA-3328 covered.
+ */
+ @Test
+ public void testCommentLinesBeforeHeader() throws Exception {
+ for (int lines : new int[]{1, 10, 50}) {
+ assertEquals(PDF, detect(commentLines(lines, 60) + PDF_BODY),
lines + " comment lines");
+ }
+ assertEquals(PDF, detect(commentLines(5, 150) + PDF_BODY),
"maximum-length lines");
+ }
+
+ /**
+ * Both bounds at once. This is the case that catches a prefix sized
within the
+ * documented bounds but past the 8K MagicDetector hands a regex.
+ */
+ @Test
+ public void testLargestAcceptedPrefix() throws Exception {
+ assertEquals(PDF, detect(commentLines(50, 150) + PDF_BODY));
+ }
+
+ @Test
+ public void testBlankLinesAndLineEndings() throws Exception {
+ assertEquals(PDF, detect("%%BeginTicket\r\n\r\n%%EndTicket\n\n" +
PDF_BODY));
+ assertEquals(PDF, detect("\r\n\r\n" + PDF_BODY));
+ assertEquals(PDF, detect("%%a\r%%b\r" + PDF_BODY));
+ assertEquals(PDF, detect("%%a\n%%b\n" + PDF_BODY.replace("%PDF-1.",
"%PDF-2.")));
+ }
+
+ /**
+ * Each negative case puts the header past 512 bytes, so only the
TIKA-4782 rule
+ * could have matched it.
+ */
+ @Test
+ public void testCommentPrefixIsBounded() throws Exception {
+ assertNotEquals(PDF, detect(commentLines(51, 60) + PDF_BODY), "51
comment lines");
+ assertNotEquals(PDF, detect(commentLines(5, 151) + PDF_BODY),
"over-long comment lines");
+ }
+
+ /**
+ * Only comment and blank lines may precede the header: anything else and
this is
+ * some other format that happens to embed a PDF.
+ */
+ @Test
+ public void testNonCommentPrefixIsNotPdf() throws Exception {
+ assertNotEquals(PDF, detect(commentLines(10, 60) + "x = 1;\r\n" +
PDF_BODY));
+ }
+
+ @Test
+ public void testMatlabStillDetected() throws Exception {
+ assertEquals(MATLAB, detect("%% cell one\r\nx = 1;\r\n%% cell two\r\ny
= x + 1;\r\n"));
+ }
+
+ /**
+ * The TIKA-4782 regex must not backtrack. Earlier drafts of it hung
Java's matcher
+ * indefinitely on these inputs; linear forms answer in well under a
millisecond, so
+ * a generous timeout separates the two without being timing-sensitive.
+ */
+ @Test
+ public void testNoCatastrophicBacktracking() {
+ String[] hostile = new String[]{
+ "\r\n".repeat(4096),
+ "\r".repeat(8192),
+ "%".repeat(8192),
+ "%%".repeat(4096),
+ "%%a\r\n".repeat(1638),
+ "%%a\r\n\r\n".repeat(1024),
+ commentLines(50, 150) + "\r\n".repeat(1000)
+ };
+ assertTimeoutPreemptively(Duration.ofSeconds(10), () -> {
+ for (String s : hostile) {
+ detect(s);
+ }
+ });
+ }
+
+ /**
+ * @param lineLength characters per line including the leading {@code %%},
excluding the CRLF
+ */
+ private static String commentLines(int count, int lineLength) {
+ StringBuilder line = new StringBuilder("%%");
+ while (line.length() < lineLength) {
+ line.append('A');
+ }
+ line.append("\r\n");
+ StringBuilder sb = new StringBuilder();
+ for (int i = 0; i < count; i++) {
+ sb.append(line);
+ }
+ return sb.toString();
+ }
+
+ private static MediaType detect(String bytes) throws Exception {
+ try (TikaInputStream tis =
TikaInputStream.get(bytes.getBytes(ISO_8859_1))) {
+ return MIME_TYPES.detect(tis, new Metadata(), new ParseContext());
+ }
+ }
+
+ private static MediaType detect(InputStream in) throws Exception {
+ try (TikaInputStream tis = TikaInputStream.get(in)) {
+ return MIME_TYPES.detect(tis, new Metadata(), new ParseContext());
+ }
+ }
+}
diff --git
a/tika-core/src/test/resources/org/apache/tika/mime/test-pdf-with-print-ticket-header.pdf
b/tika-core/src/test/resources/org/apache/tika/mime/test-pdf-with-print-ticket-header.pdf
new file mode 100644
index 0000000000..a23b0c6c4d
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b/tika-core/src/test/resources/org/apache/tika/mime/test-pdf-with-print-ticket-header.pdf
differ
