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Catch null in calls to KnownHosts #437

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Merged
kruton merged 1 commit into from
Dec 22, 2025
Merged

Catch null in calls to KnownHosts #437

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6 changes: 6 additions & 0 deletions src/main/java/com/trilead/ssh2/KnownHosts.java
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Original file line number Diff line number Diff line change
Expand Up @@ -368,6 +368,9 @@ private final boolean hostnameMatches(String[] hostpatterns, String hostname)
boolean isMatch = false;
boolean negate = false;

if (hostname == null)
return false;

hostname = hostname.toLowerCase(Locale.US);

for (int k = 0; k < hostpatterns.length; k++)
Expand Down Expand Up @@ -806,6 +809,9 @@ public void removeServerHostKey(String hostname, int port, String serverHostKeyA
if (!hostnameMatches(entry.patterns, hostname))
return false;

if (serverHostKeyAlgorithm == null)
return false;

String algo = publicKeyToAlgorithm(entry.key);
return serverHostKeyAlgorithm.equals(algo);
});
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21 changes: 21 additions & 0 deletions src/test/java/com/trilead/ssh2/KnownHostsTest.java
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Expand Up @@ -153,4 +153,25 @@ public void getPreferredServerHostkeyAlgorithmOrder_Unknown() throws Exception {
assertThat(obj.getPreferredServerHostkeyAlgorithmOrder("unknown"),
nullValue());
}

@Test
public void removeServerHostKey_NullHostname() throws Exception {
KnownHosts obj = new KnownHosts();
obj.addHostkeys(getKnownHosts("known_hosts"));
obj.removeServerHostKey(null, 22, "ssh-rsa", null);
}

@Test
public void removeServerHostKey_NullAlgorithm() throws Exception {
KnownHosts obj = new KnownHosts();
obj.addHostkeys(getKnownHosts("known_hosts"));
obj.removeServerHostKey("example.com", 22, null, null);
}

@Test
public void removeServerHostKey_BothNull() throws Exception {
KnownHosts obj = new KnownHosts();
obj.addHostkeys(getKnownHosts("known_hosts"));
obj.removeServerHostKey(null, 22, null, null);
}
}
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