-
Notifications
You must be signed in to change notification settings - Fork 79
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
FEAT: Text stream validation for literals
- added `PdfTextStream` class to handle: - detection of a text stream between `BT` and `ET` operators; - distinguish between hex streams (not validated yet) and string literals; - balance parenthesis in string literals while accounting for escaped characters; - added two new PDF error messages: - `PDF-HUL-163` IO Exception reading text stream; - `PDF-HUL-164` Unbalanced parentheses in text stream; - added a first cut function for walking pagesfor validation: `PdfModule:checkPageTextStreams`; - added method to check text streams: `PageObject:checkTextStreams`; - tidied up page content stream handling, empty lists are safer than nulls; - check page text streams after font finding; - removed unnecessary param from filter extraction; - fixed minor issue in header handling that terminated processing early for invalid files; and - added test files for the above.
- Loading branch information
1 parent
4fd44c2
commit a28bad1
Showing
12 changed files
with
220 additions
and
63 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
94 changes: 94 additions & 0 deletions
94
jhove-modules/pdf-hul/src/main/java/edu/harvard/hul/ois/jhove/module/pdf/PdfTextStream.java
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,94 @@ | ||
| package edu.harvard.hul.ois.jhove.module.pdf; | ||
|
|
||
| import java.io.IOException; | ||
| import java.io.RandomAccessFile; | ||
| import java.nio.charset.StandardCharsets; | ||
| import java.util.Arrays; | ||
|
|
||
| public class PdfTextStream { | ||
| private final byte[] streamData; | ||
|
|
||
| public PdfTextStream(PdfStream pdfStream, final RandomAccessFile raf) throws IOException { | ||
| Stream stream = pdfStream.getStream(); | ||
| stream.initRead(raf); | ||
| this.streamData = stream.getRawData(); | ||
| } | ||
|
|
||
| public void validate() throws PdfInvalidException { | ||
| String chars = new String(this.streamData, StandardCharsets.UTF_8); | ||
| if (isTextStream(chars) && !isHexStream(chars)) { | ||
| int textStart = chars.indexOf("BT"); | ||
| int parenthesesCount = 0; | ||
| char lastChar = 00; | ||
| boolean parenthesesFound = false; | ||
| for (int i = textStart; i < chars.lastIndexOf("ET"); i++) { | ||
| if (isReverseSolidus(lastChar)) { | ||
| // Ignore characters that are escaped, these may be legitimate unbalanced parentheses | ||
| lastChar = chars.charAt(i); | ||
| continue; | ||
| } | ||
| if (chars.charAt(i) == '(') { | ||
| parenthesesFound = true; | ||
| parenthesesCount++; | ||
| } else if (chars.charAt(i) == ')') { | ||
| parenthesesFound = true; | ||
| parenthesesCount--; | ||
| } | ||
| lastChar = chars.charAt(i); | ||
| } | ||
| if (parenthesesCount != 0 || !parenthesesFound) { | ||
| // The number of opening and closing braces don't match | ||
| // This is a sign that the text stream is malformed | ||
| throw new PdfInvalidException(MessageConstants.PDF_HUL_164); // PDF-HUL-123 | ||
| } | ||
| } | ||
| } | ||
|
|
||
| private boolean isReverseSolidus(final char toValidate) { | ||
| // Returns true if the character is a reverse solidus, false otherwise | ||
| return toValidate == '\\'; | ||
| } | ||
|
|
||
| private boolean isTextStream(final String toValidate) { | ||
| // Check if the stream is a text stream | ||
| if (toValidate.contains("BT") && toValidate.contains("ET")) { | ||
| // It contains both a begin and end text operator, get the first occurrence of BT and the last occurrence of ET | ||
| int firstBt = toValidate.indexOf("BT"); | ||
| int lastEt = toValidate.lastIndexOf("ET"); | ||
| if ((firstBt < lastEt) && | ||
| (firstBt == 0 || (Arrays.stream(Tokenizer.WHITESPACES).anyMatch(Character.valueOf(toValidate.charAt(firstBt -1))::equals))) && | ||
| (Arrays.stream(Tokenizer.WHITESPACES).anyMatch(Character.valueOf(toValidate.charAt(lastEt -1))::equals))) { | ||
| // Checks that the first occurrence of BT is before the last occurrence of ET, AND that the BT is the first char in the string OR | ||
| // the character before BT is a whitespace character, AND that the character before ET is a whitespace character. | ||
| // If so then return true | ||
| return true; | ||
| } | ||
| } | ||
| return false; | ||
| } | ||
|
|
||
| private boolean isHexStream(final String toValidate) { | ||
| // Check if the stream is a hex text stream, denoted by the presence of < and > rather than ( and ) | ||
| char lastChar = 00; | ||
| for (int i = toValidate.indexOf("BT"); i < toValidate.lastIndexOf("ET"); i++) { | ||
| // Work between the BT and ET operators | ||
| if (toValidate.charAt(i) == '(') { | ||
| // We found an opening parenthesis, check if it's escaped | ||
| if (!isReverseSolidus(lastChar)) { | ||
| // If it's not escaped then it's a literal text string comprised of characters | ||
| return false; | ||
| } | ||
| } else if (toValidate.charAt(i) == '<') { | ||
| // We found an opening angle bracket, check if it's escaped | ||
| if (!isReverseSolidus(lastChar)) { | ||
| // If it's not escaped then it's a hex string comprised of pairs of hexadecimal digits | ||
| return true; | ||
| } | ||
| } | ||
| lastChar = toValidate.charAt(i); | ||
| } | ||
| // If we reach this point then the stream is not a hex stream | ||
| return false; | ||
| } | ||
|
|
||
| } |
Oops, something went wrong.