connectbot/sshlib

package com.trilead.ssh2;

import com.trilead.ssh2.packets.PacketExtInfo;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

/**
 * SSH extensions reported by the server
 *
 * https://tools.ietf.org/html/draft-ietf-curdle-ssh-ext-info-15
 */
public class ExtensionInfo
{
    private final Set<String> signatureAlgorithmsAccepted;

    /**
     * @return Signature algorithms that server will accept. If empty, this extension was absent.
     */
    public Set<String> getSignatureAlgorithmsAccepted()
    {
        return signatureAlgorithmsAccepted;
    }

    public static ExtensionInfo fromPacketExtInfo(PacketExtInfo packetExtInfo)
    {
        String rawAlgs = packetExtInfo.getExtNameToValue().get("server-sig-algs");
        if (rawAlgs == null)
        {
            return new ExtensionInfo(Collections.<String>emptySet());
        }

        Set<String> algsSet = new HashSet<>();
        Collections.addAll(algsSet, rawAlgs.split(","));
        return new ExtensionInfo(algsSet);
    }

    public static ExtensionInfo noExtInfoSeen()
    {
        return new ExtensionInfo(Collections.<String>emptySet());
    }

    private ExtensionInfo(Set<String> signatureAlgorithmsAccepted)
    {
        this.signatureAlgorithmsAccepted = Collections.unmodifiableSet(signatureAlgorithmsAccepted);
    }
}