Bottom Line: Here’s how I fixed
Connection reset by peer on MacOS
After updating to MacOS Monterey (12.0) a couple of days ago, I found that my SSH access was no longer working.
My SSH access is set up on a custom port, which helps reduce the burden of constant port scanning (though is definitely “security through obscurity”); MacOS didn’t make this particularly easy to do, so I went through my setup in a prior post: How to Change the SSH Port on OSX El Capitan.
In trying to debug, I tried to connect locally, since I know that I have an ssh key set up to allow me to ssh to myself:
$ # replace 22 with your actual port number $ ssh -4 -p 22 localhost kex_exchange_identification: read: Connection reset by peer Connection reset by 127.0.0.1 port 22
I googled a bit and didn’t find much information about that error:
kex_exchange_identification: read: Connection reset by peer.
Reviewing my old post, I noticed that I had copied my SSH template from
Comparing the system-supplied one and my customized one: (
showed a few differences, notably the addition of
man 5 launchd.plist) and changing the ssh command from
Adopting these changes got SSH working again. For users starting from scratch,
I would recommend following the step-by-step from my prior post; my
/Library/LaunchDaemons/ssh.plist looks like this, replacing
REDACTED with my actual port number.
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0"> <dict> <key>Disabled</key> <false/> <key>Label</key> <string>com.n8henrie.sshd</string> <key>Program</key> <string>/usr/libexec/sshd-keygen-wrapper</string> <key>ProgramArguments</key> <array> <string>sshd-keygen-wrapper</string> </array> <key>Sockets</key> <dict> <key>Listeners</key> <dict> <key>SockServiceName</key> <string>REDACTED</string> <key>Bonjour</key> <array> <string>ssh</string> <string>sftp-ssh</string> </array> </dict> </dict> <key>inetdCompatibility</key> <dict> <key>Wait</key> <false/> <key>Instances</key> <integer>42</integer> </dict> <key>StandardErrorPath</key> <string>/dev/null</string> <key>RunAtLoad</key> <true/> <key>SHAuthorizationRight</key> <string>system.preferences</string> <key>POSIXSpawnType</key> <string>Interactive</string> <key>MaterializeDatalessFiles</key> <true/> </dict> </plist>
Next, reload the file in
$ sudo launchctl unload -w /Library/LaunchDaemons/ssh.plist $ sudo launchctl load -w /Library/LaunchDaemons/ssh.plist
At this point, I could
ssh -p 22 localhost and connect. Woohoo!
Unfortunately, I also noted that password authentication was working (which I like to disable):
ssh -p 22 -o pubkeyauthentication=no localhost
For this, I came across a post detailing a new method for disabling PAM
and password authentication on Monterey (ssh has gone to a
setup). The bottom line of the post amounts to the command below.
$ cat <<'EOF' | sudo tee /etc/ssh/sshd_config.d/000-n8henrie.conf UsePAM no PasswordAuthentication no EOF
After running this, I could confirm that password authentication was no longer possible:
$ ssh -p 22 -o pubkeyauthentication=no localhost n8henrie@localhost: Permission denied (publickey,keyboard-interactive).