Tutorial: SSH. Secure SHell: Connect remotely anything, anywhere. UL High Performance Computing (HPC) Team Sebastien Varrette

Transcription

1 Secure SHell: Connect remotely anything, anywhere UL High Performance Computing (HPC) Team Sebastien Varrette University of Luxembourg (UL), Luxembourg 1 / 26

2 Summary 1 Introduction 2 Installation Linux / Mac OS Windows 3 Usage Basic usage Advanced Usage with SOCKS [5] Proxy Advanced Usage with ProxyCommand 4 Extras Tools around SSH ASSH DSH 2 / 26

3 Introduction Summary 1 Introduction 2 Installation Linux / Mac OS Windows 3 Usage Basic usage Advanced Usage with SOCKS [5] Proxy Advanced Usage with ProxyCommand 4 Extras Tools around SSH ASSH DSH 3 / 26

4 Introduction SSH: Secure Shell Ensure secure connection to remote (UL) server establish encrypted tunnel using asymmetric keys Public id_rsa.pub vs. Private id_rsa (without.pub) typically on a non-standard port (Ex: 8022) limits kiddie script Basic rule: 1 machine = 1 key pair the private key is SECRET: never send it to anybody Can be protected with a passphrase 4 / 26

5 Introduction SSH: Secure Shell Ensure secure connection to remote (UL) server establish encrypted tunnel using asymmetric keys Public id_rsa.pub vs. Private id_rsa (without.pub) typically on a non-standard port (Ex: 8022) limits kiddie script Basic rule: 1 machine = 1 key pair the private key is SECRET: never send it to anybody Can be protected with a passphrase SSH is used as a secure backbone channel for many tools Remote shell i.e remote command line File transfer: rsync, scp, sftp versionning synchronization (svn, git), github, gitlab etc. 4 / 26

6 Introduction SSH: Secure Shell Ensure secure connection to remote (UL) server establish encrypted tunnel using asymmetric keys Public id_rsa.pub vs. Private id_rsa (without.pub) typically on a non-standard port (Ex: 8022) limits kiddie script Basic rule: 1 machine = 1 key pair the private key is SECRET: never send it to anybody Can be protected with a passphrase SSH is used as a secure backbone channel for many tools Remote shell i.e remote command line File transfer: rsync, scp, sftp versionning synchronization (svn, git), github, gitlab etc. Authentication: password (better) public key authentication (disable if possible) 4 / 26

7 Introduction SSH: Public Key Authentication Client Local Machine local homedir ~/.ssh/ id_rsa owns local private key id_rsa.pub known_hosts logs known servers 5 / 26

8 Introduction SSH: Public Key Authentication Client Local Machine Server Remote Machine local homedir ~/.ssh/ id_rsa owns local private key remote homedir ~/.ssh/ authorized_keys knows granted (public) key id_rsa.pub known_hosts logs known servers 5 / 26

9 Introduction SSH: Public Key Authentication Client Local Machine Server Remote Machine local homedir ~/.ssh/ id_rsa owns local private key remote homedir ~/.ssh/ authorized_keys knows granted (public) key id_rsa.pub known_hosts logs known servers SSH server config /etc/ssh/ sshd_config ssh_host_rsa_key ssh_host_rsa_key.pub 5 / 26

10 Introduction SSH: Public Key Authentication Client Local Machine Server Remote Machine local homedir ~/.ssh/ id_rsa owns local private key remote homedir ~/.ssh/ authorized_keys knows granted (public) key id_rsa.pub 5 / 26

11 Introduction SSH: Public Key Authentication Client Local Machine Server Remote Machine local homedir ~/.ssh/ id_rsa id_rsa.pub owns local private key 1. Initiate connection 3. solve challenge using private key return response 2. create random challenge, encrypt using public key remote homedir ~/.ssh/ authorized_keys knows granted (public) key 4. allow connection iff response == challenge Restrict to public key authentication: /etc/ssh/sshd_config: PermitRootLogin no # Disable Passwords PasswordAuthentication no ChallengeResponseAuthentication no # Enable Public key auth. RSAAuthentication yes PubkeyAuthentication yes 5 / 26

12 Installation Summary 1 Introduction 2 Installation Linux / Mac OS Windows 3 Usage Basic usage Advanced Usage with SOCKS [5] Proxy Advanced Usage with ProxyCommand 4 Extras Tools around SSH ASSH DSH 6 / 26

13 Installation SSH Setup on Linux / Mac OS OpenSSH natively supported; configuration directory : ~/.ssh/ package openssh-client (Debian-like) or ssh (Redhat-like) SSH Key Pairs (public vs private) generation: ssh-keygen specify a strong passphrase protect your private key from being stolen i.e. impersonation drawback: passphrase must be typed to use your key 7 / 26

14 Installation SSH Setup on Linux / Mac OS OpenSSH natively supported; configuration directory : ~/.ssh/ package openssh-client (Debian-like) or ssh (Redhat-like) SSH Key Pairs (public vs private) generation: ssh-keygen specify a strong passphrase protect your private key from being stolen i.e. impersonation drawback: passphrase must be typed to use your key ssh-agent 7 / 26

15 Installation SSH Setup on Linux / Mac OS OpenSSH natively supported; configuration directory : ~/.ssh/ package openssh-client (Debian-like) or ssh (Redhat-like) SSH Key Pairs (public vs private) generation: ssh-keygen specify a strong passphrase protect your private key from being stolen i.e. impersonation drawback: passphrase must be typed to use your key ssh-agent DSA and RSA 1024 bit are deprecated now! 7 / 26

16 Installation SSH Setup on Linux / Mac OS OpenSSH natively supported; configuration directory : ~/.ssh/ package openssh-client (Debian-like) or ssh (Redhat-like) SSH Key Pairs (public vs private) generation: ssh-keygen specify a strong passphrase protect your private key from being stolen i.e. impersonation drawback: passphrase must be typed to use your key ssh-agent DSA and RSA 1024 bit are deprecated now! $> ssh-keygen -t rsa -b o -a 100 # 4096 bits RSA (better) $> ssh-keygen -t ed o -a 100 # new sexy Ed25519 Private (identity) key ~/.ssh/id_{rsa,ed25519} Public Key ~/.ssh/id_{rsa,ed25519}.pub 7 / 26

17 Installation SSH Setup on Windows: the OLD way Putty Suite, includes: PuTTY, the free SSH client Pageant, an SSH authentication agent for PuTTY tools PLink, th PuTTy CLI PuTTYgen, an RSA and DSA key generation utility 8 / 26

18 Installation SSH Setup on Windows: the OLD way Putty Suite, includes: PuTTY, the free SSH client Pageant, an SSH authentication agent for PuTTY tools PLink, th PuTTy CLI PuTTYgen, an RSA and DSA key generation utility PuTTY OpenSSH 8 / 26

19 Installation SSH Setup on Windows: the OLD way Putty Suite, includes: PuTTY, the free SSH client Pageant, an SSH authentication agent for PuTTY tools PLink, th PuTTy CLI PuTTYgen, an RSA and DSA key generation utility PuTTY OpenSSH Putty keys are NOT supported by OpenSSH (yet can be exported) Binding Pageant with OpenSSH agent is NOT natively supported Third-party tools like ssh-pageant are made for that Combine nicely with Git bash with PLink, hostnames eventually refer to PuTTY Sessions NEVER to SSH entries in ~/.ssh/config This usage might be hidden... Ex: $GIT_SSH etc. 8 / 26

20 Installation SSH Setup on Windows: the NEW way Use MobaXterm! [tabbed] Sessions management X11 server w. enhanced X extensions Graphical SFTP browser SSH gateway / tunnels wizards [remote] Text Editor / 26

21 Usage Summary 1 Introduction 2 Installation Linux / Mac OS Windows 3 Usage Basic usage Advanced Usage with SOCKS [5] Proxy Advanced Usage with ProxyCommand 4 Extras Tools around SSH ASSH DSH 10 / 26

22 Usage SSH Basic Usage *.<domain>-intern.com gitlab bastion1.<domain>.com 11 / 26

23 Usage SSH Basic Usage *.<domain>-intern.com gitlab bastion1.<domain>.com SSH 11 / 26

24 Usage SSH Basic Usage *.<domain>-intern.com gitlab bastion1.<domain>.com OpenSSH ~/.ssh/config (Mac / Linux) Host uni_* User <LOGIN> Port 8022 Host uni_bastion1 Hostname bastion1.<domain>.com SSH 11 / 26

25 Usage SSH Basic Usage *.<domain>-intern.com PuTTY / PLink / Pageant (Windows) Session uni_bastion1 - Hostname: bastion1.<domain>.com - Port: Connection/Data: username: <LOGIN> gitlab bastion1.<domain>.com OpenSSH ~/.ssh/config (Mac / Linux) Host uni_* User <LOGIN> Port 8022 Host uni_bastion1 Hostname bastion1.<domain>.com SSH 11 / 26

26 Usage SSH in Practice ~/.ssh/config $> ssh [-X] [-p <port>] # Example: ssh -p 8022 Host <shortname> Port <port> User <login> Hostname <hostname> ~/.ssh/config: Simpler commands Bash completion $> ssh cha<tab> 12 / 26

27 Usage SSH in Practice ~/.ssh/config $> ssh [-X] [-p <port>] # Example: ssh -p 8022 Host *.ext_ul ProxyCommand ssh -q chaos-cluster \ "nc -q 0 %h %p" # UL HPC Platform -- Host chaos-cluster Hostname access-chaos.uni.lu Host gaia-cluster Hostname access-gaia.uni.lu Host iris-cluster Hostname access-iris.uni.lu Host *-cluster User login #ADAPT accordingly Port 8022 ForwardAgent no Host <shortname> Port <port> User <login> Hostname <hostname> ~/.ssh/config: Simpler commands Bash completion $> ssh cha<tab> 12 / 26

28 Usage SSH in Practice ~/.ssh/config $> ssh [-X] [-p <port>] # Example: ssh -p 8022 Host *.ext_ul ProxyCommand ssh -q chaos-cluster \ "nc -q 0 %h %p" # UL HPC Platform -- Host chaos-cluster Hostname access-chaos.uni.lu Host gaia-cluster Hostname access-gaia.uni.lu Host iris-cluster Hostname access-iris.uni.lu Host *-cluster User login #ADAPT accordingly Port 8022 ForwardAgent no Host <shortname> Port <port> User <login> Hostname <hostname> ~/.ssh/config: Simpler commands Bash completion $> ssh cha<tab> $> ssh chaos-cluster $> ssh work $> ssh work.ext_ul 12 / 26

29 Usage SSH Advanced Usage: SOCKS Proxy *.<domain>-intern.com gitlab bastion1.<domain>.com 13 / 26

30 Usage SSH Advanced Usage: SOCKS Proxy *.<domain>-intern.com PuTTY / PLink / Pageant (Windows) Session uni_bastion1 - Hostname: bastion1.<domain>.com - Port: Connection/Data: username: <LOGIN> gitlab bastion1.<domain>.com OpenSSH ~/.ssh/config (Mac / Linux) Host uni_* User <LOGIN> Port 8022 Host uni_bastion1 Hostname bastion1.<domain>.com SSH 13 / 26

31 Usage SSH Advanced Usage: SOCKS Proxy *.<domain>-intern.com PuTTY / PLink / Pageant (Windows) Session uni_bastion1 - Hostname: bastion1.<domain>.com - Port: Connection/Data: username: <LOGIN> gitlab bastion1.<domain>.com OpenSSH ~/.ssh/config (Mac / Linux) Host uni_* User <LOGIN> Port 8022 Host uni_bastion1 Hostname bastion1.<domain>.com SSH DOMAIN <domain>-intern.com NOT FOUND 13 / 26

32 Usage SSH Advanced Usage: SOCKS Proxy *.<domain>-intern.com PuTTY / PLink / Pageant (Windows) Session uni_bastion1 - Hostname: bastion1.<domain>.com - Port: Connection/Data: username: <LOGIN> - Connection/SSH/Tunnels: Port 1080, Dynamic gitlab bastion1.<domain>.com OpenSSH ~/.ssh/config (Mac / Linux) Host uni_* User <LOGIN> Port 8022 Host uni_bastion1 Hostname bastion1.<domain>.com SOCKS LISTEN: localhost:1080 SSH -D 1080 (SOCKS 5 Proxy) 13 / 26

33 Usage SSH Advanced Usage: SOCKS Proxy *.<domain>-intern.com PuTTY / PLink / Pageant (Windows) Session uni_bastion1 - Hostname: bastion1.<domain>.com - Port: Connection/Data: username: <LOGIN> - Connection/SSH/Tunnels: Port 1080, Dynamic gitlab bastion1.<domain>.com OpenSSH ~/.ssh/config (Mac / Linux) Host uni_* User <LOGIN> Port 8022 Host uni_bastion1 Hostname bastion1.<domain>.com SOCKS LISTEN: localhost:1080 SSH -D 1080 (SOCKS 5 Proxy) 13 / 26

34 Usage SSH Advanced Usage: SOCKS Proxy *.<domain>-intern.com PuTTY / PLink / Pageant (Windows) Session uni_bastion1 - Hostname: bastion1.<domain>.com - Port: Connection/Data: username: <LOGIN> - Connection/SSH/Tunnels: Port 1080, Dynamic gitlab bastion1.<domain>.com OpenSSH ~/.ssh/config (Mac / Linux) Host uni_* User <LOGIN> Port 8022 Host uni_bastion1 Hostname bastion1.<domain>.com SOCKS LISTEN: localhost:1080 SSH -D 1080 (SOCKS 5 Proxy) 13 / 26

35 Usage SSH Advanced Usage: SOCKS Proxy *.<domain>-intern.com PuTTY / PLink / Pageant (Windows) Session uni_bastion1 - Hostname: bastion1.<domain>.com - Port: Connection/Data: username: <LOGIN> - Connection/SSH/Tunnels: Port 1080, Dynamic gitlab bastion1.<domain>.com OpenSSH ~/.ssh/config (Mac / Linux) Host uni_* User <LOGIN> Port 8022 Host uni_bastion1 Hostname bastion1.<domain>.com SOCKS LISTEN: localhost:1080 SSH -D 1080 (SOCKS 5 Proxy) 13 / 26

36 Usage SSH Advanced Usage: SOCKS Proxy *.<domain>-intern.com PuTTY / PLink / Pageant (Windows) Session uni_bastion1 - Hostname: bastion1.<domain>.com - Port: Connection/Data: username: <LOGIN> - Connection/SSH/Tunnels: Port 1080, Dynamic gitlab bastion1.<domain>.com OpenSSH ~/.ssh/config (Mac / Linux) Host uni_* User <LOGIN> Port 8022 Host uni_bastion1 Hostname bastion1.<domain>.com SOCKS LISTEN: localhost:1080 SSH -D 1080 (SOCKS 5 Proxy) 13 / 26

37 Usage SSH Advanced Usage: ProxyCommand *.<domain>-intern.com gitlab bastion1.<domain>.com 14 / 26

38 Usage SSH Advanced Usage: ProxyCommand *.<domain>-intern.com PuTTY / PLink / Pageant (Windows) Session uni_bastion1 - Hostname: bastion1.<domain>.com - Port: Connection/Data: username: <LOGIN> gitlab bastion1.<domain>.com OpenSSH ~/.ssh/config (Mac / Linux) Host uni_* User <LOGIN> Port 8022 Host uni_bastion1 Hostname bastion1.<domain>.com SSH 14 / 26

39 Usage SSH Advanced Usage: ProxyCommand *.<domain>-intern.com PuTTY / PLink / Pageant (Windows) Session uni_bastion1 - Hostname: bastion1.<domain>.com - Port: Connection/Data: username: <LOGIN> gitlab Session uni_gitlab - Hostname: gitlab.<domain>-intern.com - Port: Connection/Data: username: <LOGIN> - Connection/Proxy: - type: local - Proxy hostname: bastion1.<domain>.com - Port: Username: <LOGIN> - Local proxy command: plink -load uni_bastion1 -nc %host:%port bastion1.<domain>.com OpenSSH ~/.ssh/config (Mac / Linux) Host uni_* User <LOGIN> Port 8022 Host uni_bastion1 Hostname bastion1.<domain>.com Host uni_gitlab Hostname gitlab ProxyCommand ssh -q uni_bastion1 "nc %h %p" SSH + ProxyCommand + netcat 14 / 26

40 Usage SSH Advanced Usage: ProxyCommand *.<domain>-intern.com PuTTY / PLink / Pageant (Windows) Session uni_bastion1 - Hostname: bastion1.<domain>.com - Port: Connection/Data: username: <LOGIN> gitlab Session uni_gitlab - Hostname: gitlab.<domain>-intern.com - Port: Connection/Data: username: <LOGIN> - Connection/Proxy: - type: local - Proxy hostname: bastion1.<domain>.com - Port: Username: <LOGIN> - Local proxy command: plink -load uni_bastion1 -nc %host:%port bastion1.<domain>.com OpenSSH ~/.ssh/config (Mac / Linux) Host uni_* User <LOGIN> Port 8022 Host uni_bastion1 Hostname bastion1.<domain>.com Host uni_gitlab Hostname gitlab ProxyCommand ssh -q uni_bastion1 "nc %h %p" SSH + ProxyCommand + netcat 14 / 26

41 Usage SSH Advanced Usage: ProxyCommand *.<domain>-intern.com PuTTY / PLink / Pageant (Windows) Session uni_bastion1 - Hostname: bastion1.<domain>.com - Port: Connection/Data: username: <LOGIN> gitlab Session uni_gitlab - Hostname: gitlab.<domain>-intern.com - Port: Connection/Data: username: <LOGIN> - Connection/Proxy: - type: local - Proxy hostname: bastion1.<domain>.com - Port: Username: <LOGIN> - Local proxy command: plink -load uni_bastion1 -nc %host:%port bastion1.<domain>.com OpenSSH ~/.ssh/config (Mac / Linux) Host uni_* User <LOGIN> Port 8022 Host uni_bastion1 Hostname bastion1.<domain>.com Host uni_gitlab Hostname gitlab ProxyCommand ssh -q uni_bastion1 "nc %h %p" SSH + ProxyCommand + netcat 14 / 26

42 Extras Tools around SSH Summary 1 Introduction 2 Installation Linux / Mac OS Windows 3 Usage Basic usage Advanced Usage with SOCKS [5] Proxy Advanced Usage with ProxyCommand 4 Extras Tools around SSH ASSH DSH 15 / 26

43 Extras Tools around SSH assh - Advanced SSH config Transparent wrapper that make ~/.ssh/config easier to manage support for templates, aliases, defaults, inheritance etc. gateways: transparent ssh connection chaining more flexible command-line Ex: Connect to hosta using hostb as a gateway $> ssh hosta/hostb drastically simplify your SSH config Linux / Mac OS only $> { apt-get yum brew } install assh # Installation 16 / 26

44 Extras Tools around SSH assh - Advanced SSH config YAML-based configuration: in ~/.ssh/assh.yml use.yml extension, NOT.yaml you can split configuration i.e. ~/.ssh/config.d/*.yml Hooks support with advanced templated capabilities Events: BeforeConnect, OnConnect, OnDisconnect Exec drivers: exec <binary> [args...] Notify driver: notify <line:string...> Compilation: $> assh config build -ignore-known-hosts > /.ssh/config 17 / 26

45 Extras Tools around SSH assh configuration ~/.ssh/assh.yml # ~/.ssh/assh.yml - Advanced SSH Config ################################################### # Global (default) SSH flags defaults: ForwardX11: no ForwardAgent: no ConnectTimeout: 15 #AddKeysToAgent: yes Compression: yes HashKnownHosts: no ServerAliveInterval: 60 ServerAliveCountMax: 30 #ControlMaster: auto #ControlPath: ~/.ssh/sockets/ssh-socket-%r-%h-%p.sock #ControlPersist: 600 includes: - ~/.ssh/config.d/*.yml - ~/.ssh/config.d/custom/*.yml 18 / 26

46 Extras Tools around SSH assh configuration: Templates # ~/.ssh/config.d/templates.yml - General templates #################################################### templates: # Public zone, feat. servers typically reachable from the outside DMZ: Hostname: "%h.domain.org" User: $USER Port: 22 # internal [private] zone for the WORK domain WORKi: Inherits: DMZ Gateways: - direct # try direct connection first... - gw #... then try through this [public] host - anotherserver #... then try through this other [public] host 19 / 26

47 Extras Tools around SSH assh configuration: Hosts # ~/.ssh/config.d/work.yml - ASSH config for your working place hosts: #### WORK gateways / Externally accessible nodes mygatewayserver: # ssh mygatewayserver Inherits: DMZ # eq. ssh -p 22 $USER@mygatewayserver.domain.org Aliases: - gw # more easier to type ssh gw anotherserver: # ssh anotherserver Inherits: DMZ # eq. ssh -p 2222 $USER@anotherserver.domain.org Port: 2222 # custom port here #### WORK internal servers workstation: Inherits: WORKi Hostname: 10.XX.XX.XX # if fixed IP and no DNS User: local gitlab: Inherits: WORKi storage: Inherits: WORKi IdentityFile: ~/.ssh/id_special_rsa 20 / 26

48 Extras Tools around SSH assh Basic Usage $> assh config build -ignore-known-hosts > /.ssh/config 21 / 26

49 Extras Tools around SSH assh Basic Usage $> assh config build -ignore-known-hosts > /.ssh/config Once ~/.ssh/config is compiled: $> ssh <host> # connect to <host> $> ssh <host>/<gw> # connect though (non-configured) <gw> 21 / 26

50 Extras Tools around SSH assh Basic Usage $> assh config build -ignore-known-hosts > /.ssh/config Once ~/.ssh/config is compiled: $> ssh <host> # connect to <host> $> ssh <host>/<gw> # connect though (non-configured) <gw> $> assh connect -dry-run <host> # dry-run verbose connection 21 / 26

51 Extras Tools around SSH assh Advanced Usage If you enable multiplexing / Control{Master,Path} settings defaults: ControlMaster: auto ControlPath: ~/.ssh/sockets/ssh-socket-%r-%h-%p.sock ControlPersist: 600 $> assh sockets list # list (opened) control sockets if you start to experience multiplexing issues: Ex: non-responding SSH connection etc. $> assh sockets flush # Close control sockets 22 / 26

52 Extras Tools around SSH DSH Distributed / Dancer s Shell SSH wrapper that allows to run commands over multiple machines. Linux / Mac OS only $> { apt-get yum brew } install dsh # Installation 23 / 26

53 Extras Tools around SSH DSH Distributed / Dancer s Shell SSH wrapper that allows to run commands over multiple machines. Linux / Mac OS only $> { apt-get yum brew } install dsh # Installation Configuration: in ~/.dsh/ ~/.dsh/dsh.conf: main configuration file ~/.dsh/machines.list: list of all nodes ~/.dsh/group/: holds group definition <name> Group definition: ~/.dsh/group/<name>: simply list SSH shortnames (one name by line) Bash completion file for DSH: 23 / 26

54 Extras Tools around SSH DSH configuration ~/.dsh/dsh.conf ############################################################ # ~/.dsh/dsh.conf # Configuration file for dsh (Distributed / Dancer s Shell). # man dsh.conf for details ############################################################ verbose = 0 remoteshell = ssh showmachinenames = 1 # Specify 1 to make the shell wait for each individual invocation. # See -c and -w option for dsh(1) waitshell = 0 # whether to wait for execution # Number of parallel connection to create at the same time. #forklimit=8 remoteshellopt = -q 24 / 26

55 Extras Tools around SSH DSH Basic Usage $> dsh [-c -w] { -a -g <group> -m <hostname> } <command> Option Description -c run the commands in parallel (default) -w run the commands in sequential -a run the command on all nodes listed in machines.list -g <group> restrict the commands to the hosts group <group> -m <hostname> run the command only on hostname FAQ: sudo: sorry, you must have a tty to run sudo requires to change the default configuration of sudo Ex: to not requiring a tty to launch a sudo command Defaults:<login>!requiretty 25 / 26

56 Thank you for your attention... Questions? Prof. Pascal Bouvry Dr. Sebastien Varrette & The UL HPC Team University of Luxembourg, Belval Campus: Maison du Nombre, 4th floor 2, avenue de l Université L-4365 Esch-sur-Alzette mail: hpc@uni.lu 1 Introduction 2 Installation Linux / Mac OS Windows 3 Usage Basic usage Advanced Usage with SOCKS [5] Proxy Advanced Usage with ProxyCommand 4 Extras Tools around SSH ASSH DSH 26 / 26