All reindex.remote.whitelist to be set to * (elastic#135546)

Prior to this change, ES would refuse to start if the
`reindex.remote.whitelist` node setting was `*` (or anything else
which matches every string). This removes that restriction.

The logic did not provide any real security, since it would accept a
setting value of `*:*`, which would effectively match everything since
the string checked against it was always of the form
`<host>:<port>`. It has been agreed that users should be allowed to
whitelist everything if they choose, so there is no value to just
making it more awkward for them to figure out how to do so.

Author: PeteGillinElastic

modules/reindex/src/main/java/org/elasticsearch/reindex/ReindexValidator.java

@@ -101,15 +101,6 @@ static CharacterRunAutomaton buildRemoteWhitelist(List<String> whitelist) {
         }
         Automaton automaton = Regex.simpleMatchToAutomaton(whitelist.toArray(Strings.EMPTY_ARRAY));
         automaton = Operations.determinize(automaton, Operations.DEFAULT_DETERMINIZE_WORK_LIMIT);
-        if (Operations.isTotal(automaton)) {
-            throw new IllegalArgumentException(
-                "Refusing to start because whitelist "
-                    + whitelist
-                    + " accepts all addresses. "
-                    + "This would allow users to reindex-from-remote any URL they like effectively having Elasticsearch make HTTP GETs "
-                    + "for them."
-            );
-        }
         return new CharacterRunAutomaton(automaton);
     }
 

modules/reindex/src/test/java/org/elasticsearch/reindex/ReindexFromRemoteWhitelistTests.java

@@ -16,7 +16,6 @@
 
 import java.net.UnknownHostException;
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.List;
 
 import static java.util.Collections.emptyList;
@@ -112,35 +111,12 @@ public void testUnwhitelistedRemote() {
         assertEquals("[not in list:" + port + "] not whitelisted in reindex.remote.whitelist", e.getMessage());
     }
 
-    public void testRejectMatchAll() {
-        assertMatchesTooMuch(singletonList("*"));
-        assertMatchesTooMuch(singletonList("**"));
-        assertMatchesTooMuch(singletonList("***"));
-        assertMatchesTooMuch(Arrays.asList("realstuff", "*"));
-        assertMatchesTooMuch(Arrays.asList("*", "realstuff"));
-        List<String> random = randomWhitelist();
-        random.add("*");
-        assertMatchesTooMuch(random);
-    }
-
     public void testIPv6Address() {
         List<String> whitelist = randomWhitelist();
         whitelist.add("[::1]:*");
         checkRemoteWhitelist(buildRemoteWhitelist(whitelist), newRemoteInfo("[::1]", 9200));
     }
 
-    private void assertMatchesTooMuch(List<String> whitelist) {
-        Exception e = expectThrows(IllegalArgumentException.class, () -> buildRemoteWhitelist(whitelist));
-        assertEquals(
-            "Refusing to start because whitelist "
-                + whitelist
-                + " accepts all addresses. "
-                + "This would allow users to reindex-from-remote any URL they like effectively having Elasticsearch make HTTP GETs "
-                + "for them.",
-            e.getMessage()
-        );
-    }
-
     private List<String> randomWhitelist() {
         int size = between(1, 100);
         List<String> whitelist = new ArrayList<>(size);