What does it do, what technologies and concepts are used and how does it reach its goal. Step by step, step by step, step by step, divide these contents into smaller parts and explain. months ago main.go chore: remove refs to deprecated io/ioutil   last month README.md Chisel GoDoc CI Chisel is a fast TCP/UDP tunnel, transported over HTTP, secured via SSH. Single executable including both client and server. Written in Go (golang). Chisel is mainly useful for passing through firewalls, though it can also be used to provide a secure endpoint into your network. overview Table of Contents Features Install Demo Usage Contributing Changelog License Features Easy to use Performant* Encrypted connections using the SSH protocol (via crypto/ssh) Authenticated connections; authenticated client connections with a users config file, authenticated server connections with fingerprint matching. Client auto-reconnects with exponential backoff Clients can create multiple tunnel endpoints over one TCP connection Clients can optionally pass through SOCKS or HTTP CONNECT proxies Reverse port forwarding (Connections go through the server and out the client) Server optionally doubles as a reverse proxy Server optionally allows SOCKS5 connections (See guide below) Clients optionally allow SOCKS5 connections from a reversed port forward Client connections over stdio which supports ssh -o ProxyCommand providing SSH over HTTP Install Binaries Releases Releases See the latest release or download and install it now with curl https://i.jpillora.com/chisel! | bash Docker Docker Pulls Image Size docker run --rm -it jpillora/chisel --help Fedora The package is maintained by the Fedora community. If you encounter issues related to the usage of the RPM, please use this issue tracker. sudo dnf -y install chisel Source $ go install github.com/jpillora/chisel@latest Demo A demo app on Heroku is running this chisel server: $ chisel server --port $PORT --proxy http://example.com # listens on $PORT, proxy web requests to http://example.com This demo app is also running a simple file server on :3000, which is normally inaccessible due to Heroku's firewall. However, if we tunnel in with: $ chisel client https://chisel-demo.herokuapp.com 3000 # connects to chisel server at https://chisel-demo.herokuapp.com, # tunnels your localhost:3000 to the server's localhost:3000 and then visit localhost:3000, we should see a directory listing. Also, if we visit the demo app in the browser we should hit the server's default proxy and see a copy of example.com. Usage $ chisel --help Usage: chisel [command] [--help] Version: X.Y.Z Commands: server - runs chisel in server mode client - runs chisel in client mode Read more: https://github.com/jpillora/chisel $ chisel server --help Usage: chisel server [options] Options: --host, Defines the HTTP listening host  the network interface (defaults the environment variable HOST and falls back to 0.0.0.0). --port, -p, Defines the HTTP listening port (defaults to the environment variable PORT and fallsback to port 8080). --key, (deprecated use --keygen and --keyfile instead) An optional string to seed the generation of a ECDSA public and private key pair. All communications will be secured using this key pair. Share the subsequent fingerprint with clients to enable detection of man-in-the-middle attacks (defaults to the CHISEL_KEY environment variable, otherwise a new key is generate each run). --keygen, A path to write a newly generated PEM-encoded SSH private key file. If users depend on your --key fingerprint, you may also include your --key to output your existing key. Use - (dash) to output the generated key to stdout. --keyfile, An optional path to a PEM-encoded SSH private key. When this flag is set, the --key option is ignored, and the provided private key is used to secure all communications. (defaults to the CHISEL_KEY_FILE environment variable). Since ECDSA keys are short, you may also set keyfile to an inline base64 private key (e.g. chisel server --keygen - | base64). --authfile, An optional path to a users.json file. This file should be an object with users defined like: { "<user:pass>": ["<addr-regex>","<addr-regex>"] } when <user> connects, their <pass> will be verified and then each of the remote addresses will be compared against the list of address regular expressions for a match. Addresses will always come in the form "<remote-host>:<remote-port>" for normal remotes and "R:<local-interface>:<local-port>" for reverse port forwarding remotes. This file will be automatically reloaded on change. --auth, An optional string representing a single user with full access, in the form of <user:pass>. It is equivalent to creating an authfile with {"<user:pass>": [""]}. If unset, it will use the environment variable AUTH. --keepalive, An optional keepalive interval. Since the underlying transport is HTTP, in many instances we'll be traversing through proxies, often these proxies will close idle connections. You must specify a time with a unit, for example '5s' or '2m'. Defaults to '25s' (set to 0s to disable). --backend, Specifies another HTTP server to proxy requests to when chisel receives a normal HTTP request. Useful for hiding chisel in plain sight. --socks5, Allow clients to access the internal SOCKS5 proxy. See chisel client --help for more information. --reverse, Allow clients to specify reverse port forwarding remotes in addition to normal remotes. --tls-key, Enables TLS and provides optional path to a PEM-encoded TLS private key. When this flag is set, you must also set --tls-cert, and you cannot set --tls-domain. --tls-cert, Enables TLS and provides optional path to a PEM-encoded TLS certificate. When this flag is set, you must also set --tls-key, and you cannot set --tls-domain. --tls-domain, Enables TLS and automatically acquires a TLS key and certificate using LetsEncrypt. Setting --tls-domain requires port 443. You may specify multiple --tls-domain flags to serve multiple domains. The resulting files are cached in the "$HOME/.cache/chisel" directory. You can modify this path by setting the CHISEL_LE_CACHE variable, or disable caching by setting this variable to "-". You can optionally provide a certificate notification email by setting CHISEL_LE_EMAIL. --tls-ca, a path to a PEM encoded CA certificate bundle or a directory holding multiple PEM encode CA certificate bundle files, which is used to validate client connections. The provided CA certificates will be used instead of the system roots. This is commonly used to implement mutual-TLS. --pid Generate pid file in current working directory -v, Enable verbose logging --help, This help text Signals: The chisel process is listening for: a SIGUSR2 to print process stats, and a SIGHUP to short-circuit the client reconnect timer Version: X.Y.Z Read more: https://github.com/jpillora/chisel $ chisel client --help Usage: chisel client [options] <server> <remote> [remote] [remote] ... <server> is the URL to the chisel server. <remote>s are remote connections tunneled through the server, each of which come in the form: <local-host>:<local-port>:<remote-host>:<remote-port>/<protocol>  local-host defaults to 0.0.0.0 (all interfaces).  local-port defaults to remote-port.  remote-port is required*.  remote-host defaults to 0.0.0.0 (server localhost).  protocol defaults to tcp. which shares <remote-host>:<remote-port> from the server to the client as <local-host>:<local-port>, or: R:<local-interface>:<local-port>:<remote-host>:<remote-port>/<protocol> which does reverse port forwarding, sharing <remote-host>:<remote-port> from the client to the server's <local-interface>:<local-port>. example remotes 3000 example.com:3000 3000:google.com:80 192.168.0.5:3000:google.com:80 socks 5000:socks R:2222:localhost:22 R:socks R:5000:socks stdio:example.com:22 1.1.1.1:53/udp When the chisel server has --socks5 enabled, remotes can specify "socks" in place of remote-host and remote-port. The default local host and port for a "socks" remote is 127.0.0.1:1080. Connections to this remote will terminate at the server's internal SOCKS5 proxy. When the chisel server has --reverse enabled, remotes can be prefixed with R to denote that they are reversed. That is, the server will listen and accept connections, and they will be proxied through the client which specified the remote. Reverse remotes specifying "R:socks" will listen on the server's default socks port (1080) and terminate the connection at the client's internal SOCKS5 proxy. When stdio is used as local-host, the tunnel will connect standard input/output of this program with the remote. This is useful when combined with ssh ProxyCommand. You can use ssh -o ProxyCommand='chisel client chiselserver stdio:%h:%p' \ user@example.com to connect to an SSH server through the tunnel. Options: --fingerprint, A *strongly recommended* fingerprint string to perform host-key validation against the server's public key. Fingerprint mismatches will close the connection. Fingerprints are generated by hashing the ECDSA public key using SHA256 and encoding the result in base64. Fingerprints must be 44 characters containing a trailing equals (=). --auth, An optional username and password (client authentication) in the form: "<user>:<pass>". These credentials are compared to the credentials inside the server's --authfile. defaults to the AUTH environment variable. --keepalive, An optional keepalive interval. Since the underlying transport is HTTP, in many instances we'll be traversing through proxies, often these proxies will close idle connections. You must specify a time with a unit, for example '5s' or '2m'. Defaults to '25s' (set to 0s to disable). --max-retry-count, Maximum number of times to retry before exiting. Defaults to unlimited. --max-retry-interval, Maximum wait time before retrying after a disconnection. Defaults to 5 minutes. --proxy, An optional HTTP CONNECT or SOCKS5 proxy which will be used to reach the chisel server. Authentication can be specified inside the URL. For example, http://admin:<PRESIDIO_ANONYMIZED_EMAIL_ADDRESS>:8081 or: socks://admin:<PRESIDIO_ANONYMIZED_EMAIL_ADDRESS>:1080 --header, Set a custom header in the form "HeaderName: HeaderContent". Can be used multiple times. (e.g --header "Foo: Bar" --header "Hello: World") --hostname, Optionally set the 'Host' header (defaults to the host found in the server url). --sni, Override the ServerName when using TLS (defaults to the hostname). --tls-ca, An optional root certificate bundle used to verify the chisel server. Only valid when connecting to the server with "https" or "wss". By default, the operating system CAs will be used. --tls-skip-verify, Skip server TLS certificate verification of chain and host name (if TLS is used for transport connections to server). If set, client accepts any TLS certificate presented by the server and any host name in that certificate. This only affects transport https (wss) connection. Chisel server's public key may be still verified (see --fingerprint) after inner connection is established. --tls-key, a path to a PEM encoded private key used for client authentication (mutual-TLS). --tls-cert, a path to a PEM encoded certificate matching the provided private key. The certificate must have client authentication enabled (mutual-TLS). --pid Generate pid file in current working directory -v, Enable verbose logging --help, This help text Signals: The chisel process is listening for: a SIGUSR2 to print process stats, and a SIGHUP to short-circuit the client reconnect timer Version: X.Y.Z Read more: https://github.com/jpillora/chisel Security Encryption is always enabled. When you start up a chisel server, it will generate an in-memory ECDSA public/private key pair. The public key fingerprint (base64 encoded SHA256) will be displayed as the server starts. Instead of generating a random key, the server may optionally specify a key file, using the --keyfile option. When clients connect, they will also display the server's public key fingerprint. The client can force a particular fingerprint using the --fingerprint option. See the --help above for more information. Authentication Using the --authfile option, the server may optionally provide a user.json configuration file to create a list of accepted users. The client then authenticates using the --auth option. See users.json for an example authentication configuration file. See the --help above for more information. Internally, this is done using the Password authentication method provided by SSH. Learn more about crypto/ssh here http://blog.gopheracademy.com/go-and-ssh/. SOCKS5 Guide with Docker Print a new private key to the terminal chisel server --keygen - # or save it to disk --keygen /path/to/mykey Start your chisel server jpillora/chisel server --keyfile '<ck-base64 string or file path>' -p 9312 --socks5 Connect your chisel client (using server's fingerprint) chisel client --fingerprint '<see server output>' <server-address>:9312 socks Point your SOCKS5 clients (e.g. OS/Browser) to: <client-address>:1080 Now you have an encrypted, authenticated SOCKS5 connection over HTTP Caveats Since WebSockets support is required: IaaS providers all will support WebSockets (unless an unsupporting HTTP proxy has been forced in front of you, in which case I'd argue that you've been downgraded to PaaS) PaaS providers vary in their support for WebSockets Heroku has full support Openshift has full support though connections are only accepted on ports 8443 and 8080 Google App Engine has no support (Track this on their repo) Contributing http://golang.org/doc/code.html http://golang.org/doc/effective_go.html github.com/jpillora/chisel/share contains the shared package github.com/jpillora/chisel/server contains the server package github.com/jpillora/chisel/client contains the client package Changelog 1.0 - Initial release 1.1 - Replaced simple symmetric encryption for ECDSA SSH 1.2 - Added SOCKS5 (server) and HTTP CONNECT (client) support 1.3 - Added reverse tunnelling support 1.4 - Added arbitrary HTTP header support 1.5 - Added reverse SOCKS support (by @aus) 1.6 - Added client stdio support (by @BoleynSu) 1.7 - Added UDP support 1.8 - Move to a scratchDocker image 1.9 - Switch from --key seed to P256 key strings with --key{gen,file} + bump to Go 1.21 (by @cmenginnz) License MIT  Jaime Pillora About A fast TCP/UDP tunnel over HTTP Topics tunnel golang http tcp Resources Readme License MIT license Activity Stars 10.1k stars Watchers 187 watching Forks 1.2k forks Report repository Releases 30 v1.9.1 Latest on Aug 23 + 29 releases Packages No packages published Used by 1.4k @thr2240 @forcodedancing @AliKarbasiCom @SAIGA-Security @qf3l3k @tsunhua @ttdung @Sem1112 + 1,417 Contributors 39 @jpillora @noahsbwilliams @aus @sunshineco @Meteorite @xtyxtyx @ArchiMoebius @iineva @fabaff @srueg @GuillaumeSmaha + 28 contributors Languages Go 98.1% Makefile 1.5% Dockerfile 0.4% Footer  2023 GitHub, Inc. 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