Hi Gyula, We've discussed the issue but no PR available yet. Feel free and cc me if you have time...
BR, G On Thu, Nov 27, 2025 at 8:52 AM Gyula Komlossi <[email protected]> wrote: > Hi Yaroslav, Gabor, > > I just ran into this issue, when tried to configure SSL for the REST > endpoint. I'm wondering what the preferred approach is with HTTPS on this > REST endpoint or if there is any code change in progress. > Have you been able to solve this one way or another, or started preparing > a code change for it? > > I was able to make this work with a small code change in the > RestServerEndpoint class to use the rest.address as the advertisedAddress > with HTTPS, but I’m looking forward to the official improvement. > Thank you both for taking care of this! > > Best, > Gyula > > > On 2025/08/19 20:34:06 Yaroslav Chernysh wrote: > > https://issues.apache.org/jira/browse/FLINK-38269 > > > > On 2025/08/19 18:58:59 Gabor Somogyi wrote: > > > You can file a jira and open a PR too so feel free. > > > > > > G > > > > > > On Tue, Aug 19, 2025, 19:51 Yaroslav Chernysh <[email protected]> > wrote: > > > > > > > Hi Gabor, > > > > > > > > > > > > Just to avoid any misunderstanding, I've been waiting for the > ticket > > > > from you. I assumed that you were going to do it. Please let me > know if > > > > I got you wrong and I should create it myself. > > > > > > > > > > > > Best regards, > > > > > > > > Yaroslav > > > > > > > > > > > > On 2025/08/18 14:07:51 Gabor Somogyi wrote: > > > > > Yeah, please read the how to contribute guide if you haven't done > > > > already. > > > > > > > > > > G > > > > > > > > > > On Mon, Aug 18, 2025 at 4:00 PM Yaroslav Chernysh < > [email protected]> > > > > > wrote: > > > > > > > > > > > Hi Gabor, > > > > > > > > > > > > > > > > > > Thanks, let's add a new option then to make advertised address > > > > > > configurable and document the default behavior. Would you mind > > filing > > > > a > > > > > > ticket for that? > > > > > > > > > > > > > > > > > > Regards, > > > > > > > > > > > > Yaroslav > > > > > > > > > > > > > > > > > > On 2025/08/18 13:41:54 Gabor Somogyi wrote: > > > > > > > Hi Yaroslav, > > > > > > > > > > > > > > Having a config option to advertise something else is what I > can > > > > > > support. > > > > > > > Needless to say the actual behavior would remain as default. > > > > > > > > > > > > > > G > > > > > > > > > > > > > > > > > > > > > On Mon, Aug 18, 2025 at 3:28 PM Yaroslav Chernysh > > <[email protected]> > > > > > > > wrote: > > > > > > > > > > > > > > > Hi Gabor, > > > > > > > > > > > > > > > > I got your point on using `getHostName()`. Thank you for > such a > > > > > > detailed > > > > > > > > explanation. > > > > > > > > > > > > > > > > What do you think about advertising rest.address instead? > In > > > > case of > > > > > > > > YARN (at least on my environment), this is already set by > YARN > > > > to a NM > > > > > > > > hostname, so rDNS would be avoided. > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > > > > Yaroslav > > > > > > > > > > > > > > > > > > > > > > > > On 2025/08/15 21:12:58 Gabor Somogyi wrote: > > > > > > > > > Hi Yaroslav, > > > > > > > > > > > > > > > > > > Thanks for your efforts in finding out all the details. > > > > > > > > > > > > > > > > > > I think making `getHostName` possible with a config + > some > > > > > > additional > > > > > > > > > warnings in the documentation can be considered. > > > > > > > > > You need to evaluate your security standards but you win > > > > something > > > > > > on > > > > > > > > one > > > > > > > > > side and introduce new attack vector on the other side. > > > > > > > > > > > > > > > > > > I would write something similar in the documentation, > and > > I also > > > > > > suggest > > > > > > > > > you consider these for your own situation as well: > > > > > > > > > - rDNS is not trustworthy for security decisions. > > Attackers with > > > > > > control > > > > > > > > > over PTR (or via poisoning/misconfig) can return > arbitrary > > > > names. > > > > > > > > > MITRE tracks this as CWE-350 [1] (Reliance on Reverse > DNS for > > > > > > > > Security). If > > > > > > > > > you base TLS host checks on rDNS, it’s bypassable. > > > > > > > > > - Slow or failing DNS causes blocking delays (seconds) > in JVM > > > > > > lookups. > > > > > > > > > OpenJDK issues document repeated timeouts and lack of > > > > > > > > > effective caching paths for some rDNS calls. Putting > rDNS in > > > > > > critical > > > > > > > > paths > > > > > > > > > (TLS, handshake, request handling) can amplify random > > outages. > > > > > > > > > > > > > > > > > > All in all I'm not yet convinced that this issue appears > in > > > > other > > > > > > > > trending > > > > > > > > > environments like k8s. > > > > > > > > > Adding this together with the mentioned risks I > personally > > > > wouldn't > > > > > > > > merge > > > > > > > > > it to the main repo. > > > > > > > > > > > > > > > > > > BR, > > > > > > > > > G > > > > > > > > > > > > > > > > > > [1] https://cwe.mitre.org/data/definitions/350.html > > > > > > > > > > > > > > > > > > > > > > > > > > > On Fri, Aug 15, 2025 at 7:44 PM Yaroslav Chernysh > > > > <[email protected]> > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > Hi Gobor, > > > > > > > > > > > > > > > > > > > > Thank you for such a quick response, I appreciate it. > > > > > > > > > > > > > > > > > > > > Actually, I'm not very good at all this security and > > > > networking > > > > > > > > stuff, so > > > > > > > > > > I apologize in advance if I'm wrong in some statement. > > > > > > > > > > > > > > > > > > > > > Does YARN containers share the host’s network in > your > > case? > > > > > > > > > > > > > > > > > > > > Yes, it does. And as far as I have researched, it > > always does, > > > > > > > > possibly > > > > > > > > > > only unless you have configured YARN to use Docker > > containers > > > > > > > > > > > > > > > > > > < > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://hadoop.apache.org/docs/r3.4.1/hadoop-yarn/hadoop-yarn-site/DockerContainers.html > > > > > > > > >, > > > > > > > > > > which is definitely not my case. I have also done some > > > > testing on > > > > > > > > my node, > > > > > > > > > > which has 2 IP addresses: > > > > > > > > > > > > > > > > > > > > - With default rest.bind-address (set by YARN to Node > > > > Manager's > > > > > > > > hostname), > > > > > > > > > > the only IP address that opens a port is the one that > NM > > > > > > hostname is > > > > > > > > > > resolved to. The other one (not sure where it comes > from, > > > > this is > > > > > > a > > > > > > > > VM) > > > > > > > > > > remains closed > > > > > > > > > > > > > > > > > > > > - With rest.bind-address set to 0.0.0.0, the port is > > open and > > > > > > > > accessible > > > > > > > > > > via both IP addresses > > > > > > > > > > > > > > > > > > > > > However if you have a single IP then using 0.0.0.0 > and > > > > > > binding it to > > > > > > > > > > lo + eth0 is something what I wouldn't worry about. > > > > > > > > > > > > > > > > > > > > I got the point and basically I agree here, but I'm not > > > > sure how > > > > > > > > > > future-proof this approach is. How probable is a > > scenario in > > > > > > which the > > > > > > > > > > environment (single IP node) is changed (to a > multi-homed > > > > > > node), but > > > > > > > > > > unchanged configuration (still listening on 0.0.0.0) > > now leads > > > > > > to an > > > > > > > > > > excessive network exposure? Either way, that's not my > case. > > > > And I > > > > > > > > think > > > > > > > > > > this is not restricted to YARN too: binding to all > > > > interfaces in > > > > > > > > Standalone > > > > > > > > > > deployment might be too excessive as well. > > > > > > > > > > > > > > > > > > > > > but you still have control on firewall, right? > > > > > > > > > > > > > > > > > > > > Probably yes (saying for an average user). This would > > probably > > > > > > > > cover the > > > > > > > > > > excessive binding leak, however only at the firewall > level > > > > and not > > > > > > > > at the > > > > > > > > > > "core". This adds a dependency on firewall. I'm not > saying > > > > it's > > > > > > > > bad, but > > > > > > > > > > rather that using the defense-in-depth approach and > > doing both > > > > > > limited > > > > > > > > > > binding and adding firewall would be even better than > > > > relying on > > > > > > > > firewall > > > > > > > > > > only. > > > > > > > > > > > > > > > > > > > > I hope all the above proves the point that even with > good > > > > enough > > > > > > > > > > environment (number of IP address + firewall) it still > does > > > > make > > > > > > > > sense to > > > > > > > > > > restrict the binding. At least that's how I see this, > > please > > > > > > > > correct me if > > > > > > > > > > I'm wrong. > > > > > > > > > > > > > > > > > > > > > introduce reverse DNS lookup as a must have feature > > > > > > > > > > > > > > > > > > > > Could we make it optional and disabled by default? > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > > > > > > > > Yaroslav > > > > > > > > > > > > > > > > > > > > On 2025/08/14 21:32:40 Gabor Somogyi wrote: > > > > > > > > > > > Hi Yaroslav, > > > > > > > > > > > > > > > > > > > > > > First of all I would like to understand why you think > > > > binding to > > > > > > > > 0.0.0.0 > > > > > > > > > > is > > > > > > > > > > > less secure in your case. Correct me if I'm wrong: > > > > > > > > > > > Does YARN containers share the host’s network in your > > > > case? On a > > > > > > > > > > > multi-homed node, 0.0.0.0 exposes on every host > > interface, > > > > > > > > > > > which can be less secure than binding to a specific > host > > > > IP. So > > > > > > > > this case > > > > > > > > > > > pinning can matter. > > > > > > > > > > > > > > > > > > > > > > However if you have a single IP then using 0.0.0.0 > and > > > > binding > > > > > > it > > > > > > > > to lo + > > > > > > > > > > > eth0 is something what I wouldn't worry about. > > > > > > > > > > > Like a "normal" kubernetes pod (default networking, > > single > > > > > > > > interface, no > > > > > > > > > > > hostNetwork) has no such issue. > > > > > > > > > > > > > > > > > > > > > > As a general remark. Let's say you expose the REST > > endpoint > > > > > > on 2 IP > > > > > > > > > > > addresses but you still have control on firewall, > right? > > > > > > > > > > > > > > > > > > > > > > The main reason why I'm asking these questions is > because > > > > using > > > > > > > > > > > `getHostName` would introduce reverse DNS lookup as a > > > > must have > > > > > > > > feature. > > > > > > > > > > > That could cause quite some turbulences at heavy > users by > > > > > > additional > > > > > > > > > > > traffic, PTR records can be wrong or spoofed, etc... > > > > > > > > > > > > > > > > > > > > > > BR, > > > > > > > > > > > G > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Thu, Aug 14, 2025 at 8:13 PM Yaroslav Chernysh > > > > > > <[email protected]> > > > > > > > > > > <[email protected]> > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > Hi Flink community, > > > > > > > > > > > > > > > > > > > > > > > > Is there a particular reason to advertise Job > Manager's > > > > REST > > > > > > > > endpoint > > > > > > > > > > > > address in a form of IP address instead of > > hostname? More > > > > > > > > precisely, > > > > > > > > > > I'm > > > > > > > > > > > > talking about this code block > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > < > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://github.com/apache/flink/blob/release-2.0.0/flink-runtime/src/main/java/org/apache/flink/runtime/rest/RestServerEndpoint.java#L298-L304 > > > > > > > > > > > > > > > > > > > > > > > > > > > < > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://github.com/apache/flink/blob/release-2.0.0/flink-runtime/src/main/java/org/apache/flink/runtime/rest/RestServerEndpoint.java#L298-L304 > > > > > > > > > > > > > > > > > > > in > > > > > > > > > > > > RestServerEndpoint.java: > > > > > > > > > > > > > > > > > > > > > > > > final InetSocketAddress bindAddress = > > (InetSocketAddress) > > > > > > > > > > > > serverChannel.localAddress(); > > > > > > > > > > > > final String advertisedAddress; > > > > > > > > > > > > if (bindAddress.getAddress().isAnyLocalAddress()) { > > > > > > > > > > > > advertisedAddress = this.restAddress; > > > > > > > > > > > > } else { > > > > > > > > > > > > advertisedAddress = > > > > > > > > > > > > bindAddress.getAddress().getHostAddress(); > > > > > > > > > > > > } > > > > > > > > > > > > > > > > > > > > > > > > That is (as far as I understood), if > rest.bind-address > > > > is set > > > > > > > > to the > > > > > > > > > > > > 0.0.0.0 wildcard (which means binding to all > available > > > > > > > > interfaces), > > > > > > > > > > then > > > > > > > > > > > > the advertised address will be the value of > > rest.address. > > > > > > > > Otherwise, an > > > > > > > > > > > > address in a form of IP address of the specified > > > > > > rest.bind-address > > > > > > > > > > will be > > > > > > > > > > > > used. > > > > > > > > > > > > What if I want to bind the REST endpoint to some > > specific > > > > > > > > address (for > > > > > > > > > > > > security reasons), but at the same time advertise > it in > > > > the > > > > > > form > > > > > > > > of > > > > > > > > > > > > hostname? Assuming that all the name resolution > things > > > > work > > > > > > > > correctly. > > > > > > > > > > > > > > > > > > > > > > > > For me particularly, the problem this creates is > with > > > > SSL. The > > > > > > > > > > certificate > > > > > > > > > > > > I have for the Job Manager (REST connectivity) is > > created > > > > > > with a > > > > > > > > > > hostname > > > > > > > > > > > > and not an IP address. I run Flink on YARN and > this way > > > > the > > > > > > > > default > > > > > > > > > > value > > > > > > > > > > > > for rest.bind-address is Node Manager's hostname > (thus, > > > > not > > > > > > the > > > > > > > > 0.0.0.0 > > > > > > > > > > > > wildcard), and the same goes for rest.address. This > > > > way, the > > > > > > > > advertised > > > > > > > > > > > > address is in the form of an IP address. I'd like > to > > > > access > > > > > > > > Flink's UI > > > > > > > > > > via > > > > > > > > > > > > the YARN Resource Manager proxy ("Tracking URL" in > the > > > > > > application > > > > > > > > > > page) > > > > > > > > > > > > that has the Job Manager's certificate in its > > truststore. > > > > > > > > However, due > > > > > > > > > > to > > > > > > > > > > > > the Flink being advertised to Resource Manager > with > > the IP > > > > > > > > address and > > > > > > > > > > the > > > > > > > > > > > > certificate holds the hostname, the connection from > > > > Resource > > > > > > > > Manager > > > > > > > > > > to Job > > > > > > > > > > > > Manager fails with: > > > > > > > > > > > > > > > > > > > > > > > > javax.net.ssl.SSLPeerUnverifiedException: > > Certificate for > > > > > > > > > > <192.168.33.11> > > > > > > > > > > > > doesn't match any of the subject alternative > names: [] > > > > > > > > > > > > > > > > > > > > > > > > The only way I can fix this (without code changes) > > is by > > > > > > > > explicitly > > > > > > > > > > > > setting rest.bind-address to 0.0.0.0, which is not > > > > secure, as > > > > > > > > far as I > > > > > > > > > > > > understand (less secure than binding to a specific > > > > address). > > > > > > > > > > > > However, if I substitute the getHostAddress() call > in > > > > the code > > > > > > > > block > > > > > > > > > > above > > > > > > > > > > > > with the getHostName(), the issue is gone. > > > > > > > > > > > > > > > > > > > > > > > > So, my question is: is there any particular reason > > not to > > > > > > > > > > > > use getHostName() here (assuming hostname is > > available)? > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > Yaroslav > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
