Hi Mark, What we are trying to do is to prevent Host header attacks by ensuring that the host name in the http request URL always matches the "Host" header in the request. If it does not, we are supposed refuse the request and respond with 400 Bad Request as per OWASP recommendations. Here are some examples:
Normal request GET http://example.com/myapp Host: example.com Expected response: 200 OK Request with a host header attack GET http://example.com/myapp Host: attacker.com Expected response: 400 Bad Request The AbstracktHttp11Processor.java class seems to be doing exactly that in the code snippet below: if (allowHostHeaderMismatch) { // The requirements of RFC 2616 are being // applied. If the host header and the request // line do not agree, the request line takes // precedence hostValueMB = headers.setValue("host"); hostValueMB.setBytes(uriB, uriBCStart + pos, slashPos - pos); } else { // The requirements of RFC 7230 are being // applied. If the host header and the request // line do not agree, trigger a 400 response. badRequest("http11processor.request.inconsistentHosts"); } However, this portion of the code is never reached for the reason mentioned in the previous email. By the time the request reaches our application, the HttpServletRequest.getRequestURL() returns http://attacker.com/myapp instead of http://example.com/myapp We have enabled the AccessLogValve in server.xml in the hope to see the URL that reaches tomcat, but it seems that we only get the relative URL there, never the absolute one, i.e. we only see /myapp when we print %u for example. Any tips in this area would be much appreciated. Ralph -----Original Message----- From: Mark Thomas <ma...@apache.org> Sent: Thursday, May 26, 2022 3:24 AM To: users@tomcat.apache.org Subject: Re: allowHostHeaderMismatch option only works if the Host Header has an http or https prefix WARNING: This email originated from outside of CallMiner. Do not click any links or open any attachments unless you recognize the sender and know that the content is safe. Please report suspicious emails to: reportsuspiciousema...@callminer.com <mailto:reportsuspiciousema...@callminer.com> On 26/05/2022 02:20, Ralph Atallah wrote: > Hi, > > We use Tomcat 7.0.109 and Tomcat 8.5 in our Tomcat based webapp deployments > and we have a new requirement to prevent Host Header injection. The > allowHostHeaderMismatch option seems the perfect answer to this issue. > However, configuring it in our environment, i.e. in the server.xml connector > tag still does not seem to make it work. > > Debugging the code, we see that the check for this setting is never even > reached in the > org.apache.coyote.http11.AbstractHttp11Processor.prepareRequest() method. > The reason is in the code snippet below: > > ByteChunk uriBC = request.requestURI().getByteChunk(); > byte[] uriB = uriBC.getBytes(); > if (uriBC.startsWithIgnoreCase("http", 0)) { > ... > if (allowHostHeaderMismatch) { > ... > } > } > > uriBC does not contain the full URL such as http://localhost:8080/myapp, but > rather only the /myapp path, so that if (uriBC.startsWithIgnoreCase("http", > 0)) condition is never met. > > We are probably missing something very basic, and would really appreciate > some guidance. I suspect that allowHostHeaderMismatch doesn't do what you think it does. Exactly what problem are you trying to solve when so say you want to prevent "Host header injection"? Mark --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
