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Normalize IDN hostnames before DNS resolution to prevent UnknownHostException #608

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Merged
arturobernalg merged 1 commit into from
Jan 6, 2025
Merged

Normalize IDN hostnames before DNS resolution to prevent UnknownHostException #608

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15 changes: 14 additions & 1 deletion httpclient5/src/main/java/org/apache/hc/client5/http/SystemDefaultDnsResolver.java
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Original file line number Diff line number Diff line change
Expand Up @@ -26,9 +26,12 @@
*/
package org.apache.hc.client5.http;

import java.net.IDN;
import java.net.InetAddress;
import java.net.UnknownHostException;

import org.apache.hc.core5.util.TextUtils;

/**
* DNS resolver that uses the default OS implementation for resolving host names.
*
Expand All @@ -44,8 +47,18 @@ public class SystemDefaultDnsResolver implements DnsResolver {
@Override
public InetAddress[] resolve(final String host) throws UnknownHostException {
try {
String normalizedHost;
if (TextUtils.isAllASCII(host)) {
normalizedHost = host;
} else {
try {
normalizedHost = IDN.toASCII(host);
} catch (final IllegalArgumentException e) {
normalizedHost = host; // Fall back to original hostname
}
}
// Try resolving using the default resolver
return InetAddress.getAllByName(host);
return InetAddress.getAllByName(normalizedHost);
} catch (final UnknownHostException e) {
// If default resolver fails, try stripping the IPv6 zone ID and resolving again
String strippedHost = null;
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