sdorra · April 29, 2020 19:33 · Apr 29, 2020
diff --git a/CorruptingProxy.groovy b/CorruptingProxy.groovy
@@ -0,0 +1,65 @@
+@Grab(group='org.eclipse.jetty', module='jetty-server', version='9.1.6.v20160112')
+@Grab(group='org.eclipse.jetty', module='jetty-servlet', version='9.1.6.v20160112')
+@Grab(group='org.eclipse.jetty', module='jetty-proxy', version='9.1.6.v20160112')
+@Grab(group='com.google.guava', module='guava', version='29.0-jre')
+
+import com.google.common.io.ByteStreams;
+import org.eclipse.jetty.client.api.Request;
+import org.eclipse.jetty.client.util.BytesContentProvider;
+import org.eclipse.jetty.proxy.ProxyServlet;
+import org.eclipse.jetty.server.Server;
+import org.eclipse.jetty.servlet.ServletContextHandler;
+import org.eclipse.jetty.servlet.ServletHolder;
+
+import javax.servlet.ServletInputStream;
+import javax.servlet.http.HttpServletRequest;
+import java.io.IOException;
+
+public class SvnProtocolProxy extends ProxyServlet.Transparent {
+
+  @Override
+  protected void customizeProxyRequest(Request proxyRequest, HttpServletRequest request) {
+    if (isSvnPutRequest(request)) {
+      try (ServletInputStream inputStream = request.getInputStream()) {
+        byte[] original = ByteStreams.toByteArray(inputStream);
+        byte[] corrupted = new byte[original.length];
+
+        for (int i = 0; i < original.length; i++) {
+          char c = (char) original[i];
+          if (c == 'a') {
+            corrupted[i] = 'z';
+          } else {
+            corrupted[i] = original[i];
+          }
+        }
+
+        byte[][] chunks = new byte[][]{
+            corrupted
+        };
+
+        proxyRequest.content(new BytesContentProvider(chunks));
+      } catch (IOException ex) {
+        ex.printStackTrace(System.err);
+      }
+    }
+  }
+
+  private boolean isSvnPutRequest(HttpServletRequest request) {
+    return "PUT".equalsIgnoreCase(request.getMethod())
+      && request.getHeader("X-SVN-Result-Fulltext-MD5") != null;
+  }
+
+}
+
+Server server = new Server(8000);
+
+ServletHolder proxyServlet = new ServletHolder(SvnProtocolProxy.class);
+proxyServlet.setInitParameter("proxyTo", "http://localhost:8080/");
+proxyServlet.setInitParameter("prefix", "/");
+
+ServletContextHandler context = new ServletContextHandler();
+context.addServlet(proxyServlet, "/*");
+
+server.setHandler(context);
+server.start();
+server.join();
diff --git a/verify.sh b/verify.sh
@@ -0,0 +1,36 @@
+# first we have to create an svn repository via scm-manager
+# in the following example we assume the repository scmadmin/hitchhiker was created
+$ svn checkout http://localhost:8000/scm/repo/scmadmin/hitchhiker
+$ cd hitchhiker
+$ echo a > a.txt
+$ svn add a.txt
+
+# the corrupting proxy will replace the content of 'a' with 'z'
+$ svn commit -m 'added a.txt'
+Adding         a.txt
+Transmitting file data .done
+Committing transaction...
+Committed revision 1.
+
+# the local copy contains 'a' but the server has 'z'
+$ svn commit -m 'update a.txt'
+Sending        a.txt
+Transmitting file data .svn: E200014: Commit failed (details follow):
+svn: E200014: svn: E200014: Base checksum mismatch on '/a.txt':
+   expected:  60b725f10c9c85c70d97880dfe8191b3
+     actual:  a8a78d0ff555c931f045b6f448129846
+
+$ cd ..
+$ rm -rf hitchhiker
+$ svn checkout http://localhost:8000/scm/repo/scmadmin/hitchhiker
+A    hitchhiker/a.txt
+Checked out revision 1.
+
+$ cat hitchhiker/a.txt
+z
+
+# but the repository on the server side does not know about the corruption
+$ svnadmin verify ${SCM_HOME}/repositories/idOfRepository/data 
+* Verifying repository metadata ...
+* Verified revision 0.
+* Verified revision 1.
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