Comparing strace between Ubuntu and Debian (lxc launch images:debian/10) showed that Debian's version doesn't try to connect to the tlsmgr socket for some reason.
Ubuntu 3.4.10-1:
# grep connect /tmp/strace | grep AF_UNIX
connect(3, {sa_family=AF_UNIX, sun_path="private/tlsmgr"}, 110) = -1 ENOENT (No such file or directory)
connect(3, {sa_family=AF_UNIX, sun_path="private/tlsmgr"}, 110) = -1 ENOENT (No such file or directory)
connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
connect(3, {sa_family=AF_UNIX, sun_path=@"userdb-523239b8d3d1ae62cb3fa3fd342937ab"}, 42) = -1 ECONNREFUSED (Connection refused)
connect(4, {sa_family=AF_UNIX, sun_path="/run/systemd/userdb/io.systemd.DynamicUser"}, 45) = 0
connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
Debian 3.4.8-0+10debu1:
# grep connect /tmp/strace | grep AF_UNIX
connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
connect(3, {sa_family=AF_UNIX, sun_path="/run/dbus/system_bus_socket"}, 30) = 0
Those with TCP/25 outbound blocked, you can hit my server on port 465 in 'wrapped' mode (-w):
Comparing strace between Ubuntu and Debian (lxc launch images:debian/10) showed that Debian's version doesn't try to connect to the tlsmgr socket for some reason.
Ubuntu 3.4.10-1:
# grep connect /tmp/strace | grep AF_UNIX "private/ tlsmgr" }, 110) = -1 ENOENT (No such file or directory) "private/ tlsmgr" }, 110) = -1 ENOENT (No such file or directory) "/var/run/ nscd/socket" }, 110) = -1 ENOENT (No such file or directory) "/var/run/ nscd/socket" }, 110) = -1 ENOENT (No such file or directory) "/var/run/ nscd/socket" }, 110) = -1 ENOENT (No such file or directory) "/var/run/ nscd/socket" }, 110) = -1 ENOENT (No such file or directory) @"userdb- 523239b8d3d1ae6 2cb3fa3fd342937 ab"}, 42) = -1 ECONNREFUSED (Connection refused) "/run/systemd/ userdb/ io.systemd. DynamicUser" }, 45) = 0 "/var/run/ nscd/socket" }, 110) = -1 ENOENT (No such file or directory) "/var/run/ nscd/socket" }, 110) = -1 ENOENT (No such file or directory)
connect(3, {sa_family=AF_UNIX, sun_path=
connect(3, {sa_family=AF_UNIX, sun_path=
connect(3, {sa_family=AF_UNIX, sun_path=
connect(3, {sa_family=AF_UNIX, sun_path=
connect(3, {sa_family=AF_UNIX, sun_path=
connect(3, {sa_family=AF_UNIX, sun_path=
connect(3, {sa_family=AF_UNIX, sun_path=
connect(4, {sa_family=AF_UNIX, sun_path=
connect(3, {sa_family=AF_UNIX, sun_path=
connect(3, {sa_family=AF_UNIX, sun_path=
Debian 3.4.8-0+10debu1:
# grep connect /tmp/strace | grep AF_UNIX "/var/run/ nscd/socket" }, 110) = -1 ENOENT (No such file or directory) "/var/run/ nscd/socket" }, 110) = -1 ENOENT (No such file or directory) "/var/run/ nscd/socket" }, 110) = -1 ENOENT (No such file or directory) "/var/run/ nscd/socket" }, 110) = -1 ENOENT (No such file or directory) "/run/dbus/ system_ bus_socket" }, 30) = 0
connect(3, {sa_family=AF_UNIX, sun_path=
connect(3, {sa_family=AF_UNIX, sun_path=
connect(3, {sa_family=AF_UNIX, sun_path=
connect(3, {sa_family=AF_UNIX, sun_path=
connect(3, {sa_family=AF_UNIX, sun_path=
Those with TCP/25 outbound blocked, you can hit my server on port 465 in 'wrapped' mode (-w):
posttls-finger -t30 -T180 -c -L verbose,summary -w smtp.sdeziel. info:465