Hi André, > Paul Klinkenberg wrote: >> Hi André, >>> Paul Klinkenberg wrote: >>>> Hi Christopher, >>>> Thanks for taking the time to respond; again much appreciated. >>>> Your point, and André's, is understood. Security should not be done based >>>> on incoming IP address. >>>> With this current project, we off course want to deliver software which is >>>> secure by default. Now, if someone would install Tomcat, then add the >>>> mod_cfml valve, and then doesn't lock port 8080 or 8009, the server would >>>> become vulnerable in the same way as if the /host-manager would not have >>>> password-protection. >>>> Currently, I am discussing with the main mod_cfml developers Jordan >>>> Michaels and Bilal Soylu how to implement security, since I now won't be >>>> implementing IP restriction. We'll probably go with using the "secret" >>>> configuration parameter for ajp like you suggested. Or maybe using a >>>> shared "secret" key between the frontend server and the Tomcat valve. In >>>> this last case, we would also have tackled security when remote attackers >>>> try to contact Tomcat on http-8080 directly, instead of using the ajp >>>> connector. >>>> I never knew the remote_addr could not be trusted, but I believe you at >>>> once when you say so. >>>> I thought it was taken from the actual socket connection. With the >>>> exception of ajp by the way, where it is programmatically changed to >>>> reflect the remote client while handling the http call. Out of curiosity, >>>> could you shed some light as to why the remote_addr is not to be trusted >>>> in a regular http request? >>>> Thanks again for your time and effort! >>>> Kind regards, >>>> Paul Klinkenberg >>> On Tomcat, you can set the AJP Connector to only listen on the local IP >>> address of the Tomcat server host. That means that only "local LAN" >>> clients (including the httpd front-end, presumably) can connect to that >>> <Connector>. >>> So this already stops any external client (be it workstation or server) >>> from even connecting to Tomcat using AJP. >>> It also, presumably, insures that only your internal httpd front-ends can >>> potentially connect to Tomcat via AJP. >>> >>> Now if you do not even trust your internal servers/clients, /then/ you need >>> additional measures. But in such a case, whether you use a "secret" which >>> the front-end must provide, or whether you use an additional header or Jk >>> variable, is only a choice; but any of those requires some setup on the >>> front-ends. >>> >>> The same is for the other Connectors, like HTTP/HTTPS. If you do not want >>> people to connect through these, disable them or have them also only listen >>> on a local IP address. >> Thanks for these tips. I see there are quite a few options to secure the AJP >> connector, which is great. >> For the project I am currently working on, I have to take into consideration >> that the user might already have Tomcat installed, and then probably with >> the default configuration. That would mean the AJP connector is available, >> and http connector as well. When someone now wants to add the mod_cfml valve >> to their setup, I will warn them in the install/config notes to lock down >> their tomcat server, if they haven't done so already. Next to this, I would >> like to be able to make the valve "secure by default", without having to >> rely on external settings. >> For this "secure by default", a required shared secret key seems like a >> solution to me. > > Note : to check. I am not sure if the HTTP/HTTPS Connectors provide this > "shared secret" thing. This may well be an AJP Connector feature only. > > Remote users accessing either the http connector or ajp connector (only > possible if the server is not firewalled), would need to have that key in > order to get the valve to create a new context. >> I _do_ trust the internal servers/clients, I just want to make sure that if >> a mod_cfml user was too lame to secure it's server, then mod_cfml isn't the >> weakest link to be able to hack the server. I hope that makes sense? > > Ok, so at this point, you only want to know, by intellectual curiosity, *how > you could* theoretically, in your Valve, obtain the IP address and port of > the front-end proxy server who is forwarding the original client request to > your Tomcat. > Oof, that was hard to write, and I hope it is correct. > > Actually, Christopher already provided the answer to that, in a previous post > : > > >>> The only way to check the caller would be to get ahold of the Socket > >>> that Tomcat is using to communicate. That's not easily done, since > >>> Tomcat wants to protect its sockets from code messing-around with the > >>> state of those Sockets." > > That's a clue, but not a very helpful one for you, is it ? > > I believe that the main issue here is that there is no such standard > functionality dictated by the Servlet Specification, so there is no > obligation for any Servlet Engine to provide this, and apparently thus Tomcat > does not provide a way to obtain this information easily, because it doesn't > have to. > And according to Christopher, there may even be a deliberate attempt from the > Tomcat code to prevent one being able to do such things easily, because it > could potentially mess up things pretty badly if one went about playing with > the underlying socket objects which Tomcat's Connectors use behind the > scenes. (And it would in any case not be portable to another Servlet Engine; > but you already have that issue with your Valve anyway, so you probably don't > care.) > > Another way of saying the above, is that Tomcat works very hard at > "abstracting" all this underlying connection stuff, because it isn't really > any of a Valve's or a Webapp's business to know any of this stuff and > potentially create code which is not portable between specification-observing > Servlet Engines. > > > But then, after having said all that, and consulted the useful on-line > documentation for HttpServletRequest -> ServletRequest > (at https://tomcat.apache.org/tomcat-8.0-doc/servletapi/index.html) > I see : > getRemoteAddr() > Returns the Internet Protocol (IP) address of the client or last proxy that > sent the request. > > So it would seem that, in the case where the request was proxied (such as via > httpd+mod_jk), getRemoteAddr() should return the IP address of the proxy. > Isn't that what you wanted in the first place ? > > And as far as I can see from other documentation (such as > http://tomcat.apache.org/connectors-doc/generic_howto/proxy.html), it is if > you want this call to return the actual original client's IP (the one which > connects to the front-end httpd), that you have to do something special at > the httpd proxy level. > > So now I am a bit confused, because as I recall (maybe wrongly), you wanted > the IP of the httpd+mod_jk front-end, didn't you ? > > And in the opposite case, there is anyway this immanent truth : if you > consider a schema like this : > > browser <-- HTTP --> httpd front-end <-- AJP --> Tomcat > (1) (2) > > Connection (1) is basically a matter only between the client and the > front-end, and Tomcat has nothing to do with it. Tomcat only knows about > connection (2), because for that one, it is one of the connected parties. > Tomcat (and whatever code in it) would basically never know *anything* about > the connection (1) above, unless the httpd front-end decides to pass > information about it to Tomcat, over connection (2). And the only way to > have this happen, is to configure the front-end specifically to do so. > > Another way to say this : no matter how deep you would dig into the objects > and methods available in Tomcat to your Valve, there is no way you could ever > find any information about connection (1), because there isn't any, other > than what you can get from the HTTP headers or the Jk variables which the > front-end adds to the HTTP request that it forwards to Tomcat.
You were totally on your way to come to the point where my original question was aimed at, and then suddenly, bam, a right turn ;-) That happened when you write "getRemoteAddr() Returns the Internet Protocol (IP) address of the client or last proxy that sent the request." Yes, that is normally the case, but not when using AJP. The missing link in the story is the "translation" that AJP does: -------------------------------------------------------- 1) browser --- HTTP ---> httpd front-end 2) httpd front-end --- AJP ---> Tomcat-AJP 3) Tomcat-AJP --- HTTP ---> Tomcat-HTTP (and back off course: ----> AJP ----> httpd ----> browser ) -------------------------------------------------------- I doubt whether the AJP connector really sets up an http connection, which the arrow "---HTTP--->" implies at position 3). I do know that both the servletrequest and the valve present inside the http connector, think it is a genuine http request coming from the browser-client, not an ajp one. For example, debug results show: request.getProtocol() : HTTP/1.1 request.getRemoteAddr() : [ip of the browser-client] request.getLocalPort() : 80 <<< not 8080! request.getCoyoteRequest().getWorkerThreadName() : ajp-nio-8009-exec-1 <<< The _only_ reference I could find to anything non-http, but this is a string... And I needed to use reflection to get to the coyote request. What I wanted to know, indeed out of intellectual interest, is what you described perfectly (even though it was hard to write): the ip address of the httpd front-end server. I really don't want to exhaust your time on a hunt for something that is just nice to know, but won't be used afterwards. But I (again!) much appreciate the time you took to dive into this quest I gotten myself into ;) Thanks, kind regards, Paul Klinkenberg --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
