search for: persourcemaxstartup

https://bugzilla.mindrot.org/show_bug.cgi?id=3709 Bug ID: 3709 Summary: PerSourceMaxStartups no longer works as advertised Product: Portable OpenSSH Version: 9.8p1 Hardware: amd64 OS: Linux Status: NEW Severity: normal Priority: P5 Component: sshd Assignee: unassigned-bugs at mindrot.org...

...om/blog/2024-04-23-an-analysis-of-dheat-dos-against-ssh-in-cloud-environments/ A short summary: the default MaxStartup setting is fully ineffective in fixing the problem in low-latency network conditions; it is very easy to force a target to hit 100% CPU utilization in that case. Furthermore, the PerSourceMaxStartups setting is only effective when set to 1, which would only allow one unauthenticated connection at a time from any given source. This works poorly in use cases where a burst of new connects is normal. Hence, connection throttling at the kernel level seems a bit better to use in the general case (...

...-of-dheat-dos-against-ssh-in-cloud-environments/ > > A short summary: the default MaxStartup setting is fully ineffective > in > fixing the problem in low-latency network conditions; it is very easy > to force a target to hit 100% CPU utilization in that case. > Furthermore, the PerSourceMaxStartups setting is only effective when > set to 1, which would only allow one unauthenticated connection at a > time from any given source. This works poorly in use cases where a > burst of new connects is normal. Hence, connection throttling at the > kernel level seems a bit better to use i...

...virtualised host (not container) running Alpine Linux 3.21.3, and openssh-9.9_p2-r0 package. I have no other VMs affected, just this one; despite the same OS and network (though I expect different patterns of ssh probes) Relevant configuration in /etc/ssh/sshd_config: MaxStartups 32:30:64 PerSourceMaxStartups 16 LoginGraceTime 30 2025-04-16T03:18:32 indigo sshd[2690]: error: beginning MaxStartups throttling 2025-04-16T03:18:32 indigo sshd[2690]: drop connection #0 from [193.32.x.x]:39772 on [54.36.x.x]:22 past Maxstartups 2025-04-16T06:33:25 indigo sshd[2690]: error: in MaxStartups throttling for 03...