SOLR-12316: Do not allow to use absolute URIs for including other files in solrconfig.xml and schema parsing

# Conflicts:
#	solr/CHANGES.txt

Author: uschindler

solr/CHANGES.txt

@@ -186,6 +186,9 @@ Bug Fixes
 
 * SOLR-12202: Fix errors in solr-exporter.cmd. (Minoru Osuka via koji)
 
+* SOLR-12316: Do not allow to use absolute URIs for including other files in solrconfig.xml and schema parsing.
+  (Ananthesh, Ishan Chattopadhyaya, Uwe Schindler)
+
 Optimizations
 ----------------------
 

solr/core/src/java/org/apache/solr/util/SystemIdResolver.java

@@ -16,17 +16,13 @@
  */
 package org.apache.solr.util;
 
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
 import org.apache.lucene.analysis.util.ResourceLoader;
 
 import org.xml.sax.InputSource;
 import org.xml.sax.EntityResolver;
 import org.xml.sax.ext.EntityResolver2;
 import java.io.File;
 import java.io.IOException;
-import java.lang.invoke.MethodHandles;
 import java.net.URI;
 import java.net.URISyntaxException;
 import javax.xml.transform.Source;
@@ -55,7 +51,6 @@
  * </pre>
  */
 public final class SystemIdResolver implements EntityResolver, EntityResolver2 {
-  private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
 
   public static final String RESOURCE_LOADER_URI_SCHEME = "solrres";
   public static final String RESOURCE_LOADER_AUTHORITY_ABSOLUTE = "@";
@@ -126,8 +121,9 @@ public InputSource getExternalSubset(String name, String baseURI) {
 
   @Override
   public InputSource resolveEntity(String name, String publicId, String baseURI, String systemId) throws IOException {
-    if (systemId == null)
+    if (systemId == null) {
       return null;
+    }
     try {
       final URI uri = resolveRelativeURI(baseURI, systemId);
 
@@ -147,12 +143,10 @@ public InputSource resolveEntity(String name, String publicId, String baseURI, S
           throw new IOException(re.getMessage(), re);
         }
       } else {
-        // resolve all other URIs using the standard resolver
-        return null;
+        throw new IOException("Cannot resolve absolute systemIDs / external entities (only relative paths work): " + systemId);
       }
     } catch (URISyntaxException use) {
-      log.warn("An URI systax problem occurred during resolving SystemId, falling back to default resolver", use);
-      return null;
+      throw new IOException("An URI syntax problem occurred during resolving systemId: " + systemId, use);
     }
   }
 

solr/core/src/test/org/apache/solr/util/TestSystemIdResolver.java

@@ -17,6 +17,7 @@
 package org.apache.solr.util;
 
 import java.io.File;
+import java.io.IOException;
 import java.nio.file.Path;
 
 import org.apache.commons.io.IOUtils;
@@ -76,8 +77,22 @@ public void testResolving() throws Exception {
     assertEntityResolving(resolver, SystemIdResolver.createSystemIdFromResourceName(testHome+"/crazy-path-to-schema.xml"),
       SystemIdResolver.createSystemIdFromResourceName(testHome+"/crazy-path-to-config.xml"), "crazy-path-to-schema.xml");
 
-    // test, that resolving works if somebody uses an absolute file:-URI in a href attribute, the resolver should return null (default fallback)
-    assertNull(resolver.resolveEntity(null, null, "solrres:/solrconfig.xml", fileUri));
+    // if somebody uses an absolute uri (e.g., file://) we should fail resolving:
+    IOException ioe = expectThrows(IOException.class, () -> {
+      resolver.resolveEntity(null, null, "solrres:/solrconfig.xml", fileUri);
+    });
+    assertTrue(ioe.getMessage().startsWith("Cannot resolve absolute"));
+    
+    ioe = expectThrows(IOException.class, () -> {
+      resolver.resolveEntity(null, null, "solrres:/solrconfig.xml", "http://lucene.apache.org/test.xml");
+    });
+    assertTrue(ioe.getMessage().startsWith("Cannot resolve absolute"));
+    
+    // check that we can't escape with absolute file paths:
+    ioe = expectThrows(IOException.class, () -> {
+      resolver.resolveEntity(null, null, "solrres:/solrconfig.xml", "/etc/passwd");
+    });
+    assertTrue(ioe.getMessage().startsWith("Can't find resource '/etc/passwd' in classpath or"));
   }
 
 }