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[UNDERTOW-2451] fix the information leakage issues #1668

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[UNDERTOW-2451] fix the information leakage issues #1668

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560b84c
fix CVE-2024-7885 vul#2
BFionaccept Sep 25, 2024
9b5acb4
fix the message leak issue in HPACK decoder
BFionaccept Sep 25, 2024
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13 changes: 1 addition & 12 deletions core/src/main/java/io/undertow/protocols/ajp/AjpResponseParser.java
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Original file line number Diff line number Diff line change
Expand Up @@ -224,11 +224,6 @@ public int getReadBodyChunkSize() {
*/
public int stringLength = -1;

/**
* The current string being read
*/
public StringBuilder currentString;
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You can't remove currentString here. The parser is invoked multiple times as bytes are made available and, when the last byte is read, it wil need the whole currentString to form a parsed result, it will neeed information from previous parse invocations. Otherwise, you risk losing bytes. It all depends on how many bytes the parser has received on every invocation.


/**
* when reading the first byte of an integer this stores the first value. It is set to -1 to signify that
* the first byte has not been read yet.
Expand All @@ -248,7 +243,6 @@ public void reset() {
reasonPhrase = null;
headers = new HeaderMap();
stringLength = -1;
currentString = null;
currentIntegerPart = -1;
readHeaders = 0;
}
Expand Down Expand Up @@ -300,12 +294,8 @@ protected StringHolder parseString(ByteBuffer buf, boolean header) {
this.stringLength = -1;
return new StringHolder(null, true, false);
}
StringBuilder builder = this.currentString;
final StringBuilder builder = new StringBuilder();

if (builder == null) {
builder = new StringBuilder();
this.currentString = builder;
}
int length = builder.length();
while (length < stringLength) {
if (!buf.hasRemaining()) {
Expand All @@ -323,7 +313,6 @@ protected StringHolder parseString(ByteBuffer buf, boolean header) {

if (buf.hasRemaining()) {
buf.get(); //null terminator
this.currentString = null;
this.stringLength = -1;
this.containsUrlCharacters = false;
return new StringHolder(builder.toString(), true, containsUrlCharacters);
Expand Down
6 changes: 2 additions & 4 deletions core/src/main/java/io/undertow/protocols/http2/HpackDecoder.java
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Expand Up @@ -73,8 +73,6 @@ public class HpackDecoder {

private boolean first = true;

private final StringBuilder stringBuilder = new StringBuilder();
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There is no leakage in this class either. In this case, we are reusing the same builder across multiple decode invocations, but we are clearing the buffer right after we use it on every call. It just prevents us from having to create a new builder everytime we are invoked, which is a good thing.

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The root cause for this leak is very similar to the vulnerability CVE-2020-17527 in Tomcat. I added additional details at https://issues.redhat.com/browse/UNDERTOW-2451.


public HpackDecoder(int maxAllowedMemorySize) {
this.specifiedMemorySize = Math.min(Hpack.DEFAULT_TABLE_SIZE, maxAllowedMemorySize);
this.maxAllowedMemorySize = maxAllowedMemorySize;
Expand Down Expand Up @@ -247,11 +245,11 @@ private String readHpackString(ByteBuffer buffer) throws HpackException {
if (huffman) {
return readHuffmanString(length, buffer);
}
StringBuilder stringBuilder = new StringBuilder(length);
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for (int i = 0; i < length; ++i) {
stringBuilder.append((char) (buffer.get() & 0xFF));
}
String ret = stringBuilder.toString();
stringBuilder.setLength(0);
if (ret.isEmpty()) {
//return the interned empty string, rather than allocating a new one each time
return "";
Expand All @@ -260,12 +258,12 @@ private String readHpackString(ByteBuffer buffer) throws HpackException {
}

private String readHuffmanString(int length, ByteBuffer buffer) throws HpackException {
StringBuilder stringBuilder = new StringBuilder(length);
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final ?

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In this fix, I referenced the patch for a similar vulnerability (CVE-2020-17527) in the corresponding functional module of Tomcat, as shown in this commit: apache/tomcat@d56293f#diff-98723542790b05d2e3c2dadeef7c632e641e3118b3b809660e9b1ef41686cfe0R226. I removed the final from the StringBuilder stringBuilder declaration, enhancing code flexibility and allowing for future reassignment if needed.

Certainly, I think it is also acceptable to retain the final modifier.

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Oh, I’m sorry, I accidentally deleted a previous conversation.

HPackHuffman.decode(buffer, length, stringBuilder);
String ret = stringBuilder.toString();
if (ret.isEmpty()) {
return "";
}
stringBuilder.setLength(0);
return ret;
}

Expand Down
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