Skip to content

8382042: Add drill-into and path info to ASN1Formatter #30685

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wangweij wants to merge 2 commits into
base: master
Choose a base branch
from
+165 −78
Open

8382042: Add drill-into and path info to ASN1Formatter #30685

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
1fa2169
the change
wangweij Apr 10, 2026
3d9b6db
do not go into non-constructed
wangweij Apr 12, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
26 changes: 24 additions & 2 deletions test/lib-test/jdk/test/lib/hexdump/ASN1FormatterTest.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,8 @@
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Base64;
import java.util.HexFormat;
import java.util.Set;

import static org.junit.jupiter.api.Assertions.*;

Expand Down Expand Up @@ -110,12 +112,32 @@ void testIndefinite() {

assertEquals(1, result.lines().filter(s -> s.contains("OCTET STRING [INDEFINITE]")).count(),
"Indefinite length");
assertEquals(2, result.lines().filter(s -> s.contains("; OCTET STRING [2]")).count(),
assertEquals(2, result.lines().filter(s -> s.contains("OCTET STRING [2]")).count(),
"Octet Sequences");
assertEquals(1, result.lines().filter(s -> s.contains("; END-OF-CONTENT")).count(),
assertEquals(1, result.lines().filter(s -> s.contains("END-OF-CONTENT")).count(),
"end of content");
}

@Test
void testPositions() {
byte[] bytes = HexFormat.of().parseHex("3009040730050201050500");
HexPrinter p = HexPrinter.simple()
.formatter(ASN1Formatter.formatter(), "; ", 100);
String result = p.toString(bytes);
System.out.println(result);

assertTrue(result.contains("[0]: OCTET STRING [7] (try --drill=0)"));

p = HexPrinter.simple()
.formatter(ASN1Formatter.formatter(Set.of("0")), "; ", 100);
result = p.toString(bytes);
System.out.println(result);

assertTrue(!result.contains("try --drill"));
Copy link
Copy Markdown

@Marcono1234 Marcono1234 Apr 12, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Could this use assertFalse instead?

assertTrue(result.contains("[0]: OCTET STRING [7]"));
assertTrue(result.contains("[0c0]: BYTE 5"));
}

@Test
void testMain() {
String file = "openssl.p12.pem";
Expand Down
174 changes: 132 additions & 42 deletions test/lib/jdk/test/lib/hexdump/ASN1Formatter.java
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2019, 2023, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2019, 2026, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
Expand Down Expand Up @@ -34,7 +34,10 @@
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Arrays;
import java.util.Base64;
import java.util.HashSet;
import java.util.Set;

/**
* ASN.1 stream formatter; a debugging utility for visualizing the contents of an ASN.1 stream.
Expand All @@ -44,6 +47,10 @@
* with the {@code HexPrinter} as a formatter to display the ASN.1 tagged values
* with the corresponding bytes.
* <p>
* The formatter can be configured with a set of drill paths, which will drill into
* the OCTET STRING or BIT STRING at the path to parse the content as another ASN.1
* stream.
* <p>
* The formatter reads a single tag from the stream and prints a description
* of the tag and its contents. If the tag is a constructed tag, set or sequence,
* each of the contained tags is read and printed.
Expand Down Expand Up @@ -88,9 +95,26 @@
* // done
* }
* }</pre>
* As a standalone program, it can be launched with
* <pre>
* java ASN1Formatter [--drill=path[,path...]] [asn1file]
* </pre>
* It parses {@code asn1file} as a binary DER or BER encoded ASN.1 data block
* and print out both the HEX dump and annotations. If no file is supplied,
* the program reads from the standard input.
* <p>
* When the program detects that the content of an OCTET STRING or BIT STRING
* might be an embedded DER or BER encoding, it prints out hints in the form
* of "try --drill=110". User can launch the program again with the option
* and the content will be displayed. Multiple drill-into path can be provided
* in comma-separated-value format.
* <p>
* If {@code --no-dump} option is provided, the HEX dump will not be displayed.
*/
public class ASN1Formatter implements HexPrinter.Formatter {

private final Set<String> drillPaths;

/**
* Returns an ASN1Formatter.
* @return an ASN1Formatter
Expand All @@ -99,10 +123,25 @@ public static ASN1Formatter formatter() {
return new ASN1Formatter();
}

/**
* Returns an ASN1Formatter that drills into OCTET STRING or BIT STRING
* content at the specified paths.
* @param drillPaths paths like {@code 110} that should be drilled into
* @return an ASN1Formatter
*/
public static ASN1Formatter formatter(Set<String> drillPaths) {
return new ASN1Formatter(drillPaths);
}

/**
* Create a ANS1Formatter.
*/
private ASN1Formatter() {
this.drillPaths = Set.of();
}

private ASN1Formatter(Set<String> drillPaths) {
this.drillPaths = drillPaths;
}

/**
Expand Down Expand Up @@ -139,22 +178,30 @@ public String annotate(DataInputStream in) {
* @throws IOException if an I/O error occurs
*/
public void annotate(DataInputStream in, Appendable out) throws IOException {
annotate(in, out, -1, "");
annotate(in, out, -1, true, "");
}

/**
* Read bytes from the stream and annotate the stream as ASN.1.
*
* @param in a DataInputStream
* @param in a DataInputStream
* @param out an Appendable for the output
* @param available the number of bytes to read from the stream (if greater than zero)
* @param isRoot true for outermost call and drilling into OCTET STRING
* @param prefix a string to prefix each line of output, used for indentation
* @throws IOException if an I/O error occurs
*/
@SuppressWarnings("fallthrough")
private int annotate(DataInputStream in, Appendable out, int available, String prefix) throws IOException {
private int annotate(DataInputStream in, Appendable out, int available,
boolean isRoot, String prefix) throws IOException {
int origAvailable = available;
int position = 0;
String currentPrefix;
while (available != 0 || origAvailable < 0) {
// When isRoot is true, there is only one ASN.1 value inside.
// Do not use a new prefix.
currentPrefix = isRoot ? prefix : (prefix + position);
position++;
// Read the tag
int tag = in.readByte() & 0xff;
available--;
Expand Down Expand Up @@ -196,7 +243,7 @@ private int annotate(DataInputStream in, Appendable out, int available, String p
// started out unknown; set available to the length of this tagged value
available = len;
}
out.append(prefix); // start with indent
out.append('[').append(currentPrefix).append("]: "); // start with path
switch (tag) {
case TAG_EndOfContent: // End-of-contents octets; len == 0
out.append("END-OF-CONTENT");
Expand Down Expand Up @@ -226,9 +273,7 @@ private int annotate(DataInputStream in, Appendable out, int available, String p
byte[] bytes = new byte[len];
int l = in.read(bytes);
BigInteger big = new BigInteger(bytes);
out.append("BIG INTEGER [" + len + "] ");
out.append(big.toString());
out.append(".");
out.append("BIG INTEGER [" + len + "]");
available -= len;
break;
}
Expand All @@ -243,7 +288,29 @@ private int annotate(DataInputStream in, Appendable out, int available, String p
out.append(' ');
break;

case TAG_OctetString:
case TAG_BitString:
case TAG_OctetString: {
out.append(String.format("%s [%d]", tagName(tag), len));
if (tag == TAG_BitString) {
in.read();
len--;
available--;
}
String drillPath = currentPrefix + "c";
if (drillPaths.contains(currentPrefix)) {
out.append(System.lineSeparator());
annotate(in, out, len, true, drillPath);
available -= len;
continue;
} else {
byte[] content = in.readNBytes(len);
available -= content.length;
if (looksLikeDrillable(content)) {
out.append(" (try --drill=").append(currentPrefix).append(")");
}
}
break;
}
case TAG_UtcTime:
case TAG_GeneralizedTime:
out.append(tagName(tag) + " [" + len + "] ");
Expand Down Expand Up @@ -300,18 +367,11 @@ private int annotate(DataInputStream in, Appendable out, int available, String p
out.append(' ');
available -= len;
break;
case TAG_BitString:
out.append(String.format("%s [%d]", tagName(tag), len));
do {
var skipped = (int) in.skip(len);
len -= skipped;
available -= skipped;
} while (len > 0);
break;
default: {
if (tag == TAG_Sequence ||
tag == TAG_Set ||
isApplication(tag) ||
isContext(tag) ||
isConstructed(tag)) {
String lenStr = (len < 0) ? "INDEFINITE" : Integer.toString(len);
// Handle nesting
Expand All @@ -320,7 +380,7 @@ private int annotate(DataInputStream in, Appendable out, int available, String p
} else {
out.append(String.format("%s [%s]%n", tagName(tag), lenStr));
}
int remaining = annotate(in, out, len, prefix + " ");
int remaining = annotate(in, out, len, false, currentPrefix);
if (len > 0) {
available -= len - remaining;
}
Expand Down Expand Up @@ -355,6 +415,22 @@ private void formatBytes(DataInputStream in, Appendable out, int len) throws IOE
}
}

private static boolean looksLikeDrillable(byte[] bytes) {
int len = bytes.length;
if (len < 2) {
return false;
}
int b1 = bytes[1] & 0xff;
return switch (b1) {
case 0x80 -> true;
case 0x81 -> bytes.length >= 3 && (bytes[2] & 0xff) == len - 3;
case 0x82 -> bytes.length >= 4
&& (((bytes[2] & 0xff) << 8) | (bytes[3] & 0xff)) == len - 4;
case 0x83, 0x84 -> false;
default -> b1 == len - 2;
};
}

/**
* Returns a string read from the stream converted to the Charset.
* @param in an inputStream
Expand All @@ -375,7 +451,7 @@ private String getString(DataInputStream in, int len, Charset charset) throws IO
* @return a String representation of the tag.
*/
private String tagName(int tag) {
String tagString = (isConstructed(tag) ? "CONSTRUCTED " : "") + tagNames[tagType(tag)];
String tagString = (isConstructed(tag) ? "CONSTRUCTED " : "") + tagNames[tagType(tag)];
switch (tag & 0xc0) {
case TAG_APPLICATION:
return "APPLICATION " + tagString;
Expand Down Expand Up @@ -424,7 +500,8 @@ private static String oidName(byte[] bytes) {
Method findMatch = cl.getDeclaredMethod("findMatch", String.class);
Object oid = findMatch.invoke(null, noid);
return (oid == null) ? noid : noid + " (" + oid.toString() + ")";
} catch (ClassNotFoundException | NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
} catch (ClassNotFoundException | NoSuchMethodException | IllegalAccessException |
InvocationTargetException e) {
return noid;
}
}
Expand Down Expand Up @@ -565,18 +642,17 @@ private int tagType(int tag) {
* These values are the high order bits for the other kinds of tags.
*/

/**
* Returns true if the tag class is UNIVERSAL.
*/
/** Returns true if the tag class is UNIVERSAL. */
private boolean isUniversal(int tag) { return ((tag & 0xc0) == 0x0); }

/**
* Returns true if the tag class is APPLICATION.
*/
/** Returns true if the tag class is APPLICATION. */
private boolean isApplication(int tag) { return ((tag & 0xc0) == TAG_APPLICATION); }

/** Returns true iff the CONSTRUCTED bit is set in the type tag. */
private boolean isConstructed(int tag) { return ((tag & 0x20) == 0x20); }
/** Returns true if the tag class is CONTEXT. */
private boolean isContext(int tag) { return ((tag & 0xc0) == TAG_CONTEXT); }

/** Returns true iff the CONSTRUCTED bit is set in the type tag. */
private boolean isConstructed(int tag) { return ((tag & 0x20) == 0x20); }

// Names for tags.
private static final String[] tagNames = new String[] {
Expand All @@ -597,26 +673,40 @@ private int tagType(int tag) {
*/
public static void main(String[] args) {
if (args.length < 1) {
System.out.println("Usage: <asn.1 files>");
System.out.println("Usage: java ASN1Formatter [--drill=path[,path...]] [asn.1 file]");
return;
}
ASN1Formatter fmt = ASN1Formatter.formatter();
for (String file : args) {
System.out.printf("%s%n", file);
try (InputStream fis = Files.newInputStream(Path.of(file));
BufferedInputStream is = new BufferedInputStream(fis);
InputStream in = wrapIfBase64Mime(is)) {

DataInputStream dis = new DataInputStream(in);
Set<String> drillPaths = new HashSet<>();
boolean dump = true;
String file = null;
for (String arg : args) {
if (arg.startsWith("--drill=")) {
drillPaths.addAll(Arrays.asList(
arg.substring("--drill=".length()).split(",")));
} else if (arg.equals("--no-dump")) {
dump = false;
} else {
file = arg;
Copy link
Copy Markdown

@Marcono1234 Marcono1234 Apr 12, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

For usability, should this report an error if file is non-null (that is, if multiple files or unknown args are specified)?

Otherwise this would silently ignore unknown args or multiple files.

}
}
ASN1Formatter fmt = ASN1Formatter.formatter(drillPaths);
try (InputStream fis = file == null ? System.in : Files.newInputStream(Path.of(file));
BufferedInputStream is = new BufferedInputStream(fis);
InputStream in = wrapIfBase64Mime(is)) {

DataInputStream dis = new DataInputStream(in);
if (dump) {
HexPrinter p = HexPrinter.simple()
.dest(System.out)
.formatter(ASN1Formatter.formatter(), "; ", 100);
.formatter(fmt, "; ", 100);
p.format(dis);
} catch (EOFException eof) {
System.out.println();
} catch (IOException ioe) {
System.out.printf("%s: %s%n", file, ioe);
} else {
System.out.println(fmt.annotate(dis));
}
} catch (EOFException eof) {
System.out.println();
} catch (IOException ioe) {
System.out.printf("%s: %s%n", file, ioe);
}
}

Expand Down