# Gophor A Gopher server written in GoLang as a means of learning about the Gopher protocol, and more GoLang. Linux only _for now_. Cross-compiled to way too many architectures. Build-script now much improved, but still not pretty... I'm unemployed and work on open-source projects like this and many others for free. If you would like to help support my work that would be hugely appreciated 💕 https://liberapay.com/grufwub/ WARNING: the development branch is filled with lava, fear and capitalism. # Features - Built with security, concurrency and efficiency in mind. - ZERO external dependencies. - LRU file caching with user-controlled cache size, max cached file size and cache refresh frequency. - CGI/1.1 support (see below for CGI environment variables set). - HTTP style URL query and encoding support. - Serve `DIR/gophermap` by default, else falls back to directory listing. - Parsing of any files named `gophermap` / ending in `.gophermap` as gophermaps. - Executable gophermap support. - Insert files with automated line reflowing, output of any CGI scripts or executable gophermaps WITHIN gophermaps. - Support for all commonly accepted item type characters (beyond just RFC1436 support). - Automatic replacement of `$hostname` or `$port` in gophermap lines with current host information. - User supplied footer text appended to gophermaps and directory listings. - Separate system and access logging with output and formatting options. ## Please note ### Gophermap parsing Due to the way that gophermap parsing is handled, if a gophermap is larger than the max cache'd file size or file caching is disabled (same as same as setting max size to 0), these gophermaps WILL NOT be parsed by the server. The features you will miss out on for these files are features listed `[SERVER ONLY]` in the gophermap item types section below. ### Chroots and privilege dropping Previously, chrooting to server directory and dropping privileges was supported by using Go C bindings. This is not officially supported due to weird behaviour with `.Set{U,G}id()` under Linux. As such, the feature has been dropped for now. There is a near 10 year ongoing tracked issue (https://github.com/golang/go/issues/1435), and as soon as this patch gets merged I'll add support: https://go-review.googlesource.com/c/go/+/210639 In place of removing this, request sanitization has been majorly improved and checks are in place to prevent running Gophor as root. If you run into issues binding to a lower port number due to insufficient permissions then there are a few alternatives: - set gophor process capabilities: e.g. `setcap 'cap_net_bind_service=+ep' /usr/local/bin/gophor` - use Docker (or some other solution) and configure port forwarding on the host - start gopher in it's own namespace in a chroot # Usage ``` gophor [args] -root Change server root directory. -bind-addr Change server bind-address (used in creating socket). -port Change server bind port. -fwd-port Change port used in $port replacement strings (e.g. when port forwarding). -hostname Change server hostname (FQDN). -system-log Path to gophor system log file. -access-log Path to gophor access log file. -log-output Change log output type (disable|stderr|file) -log-opts Comma-separated list of lop opts (timestamp|ip) -file-monitor-freq Change file-cache freshness check frequency. -file-remap New-line separated list of file remappings of format: /virtual/relative/path -> /actual/relative/path -cache-size Change max no. files in file-cache. -cache-file-max Change maximum allowed size of a cached file. -disable-cache Disable file caching. -page-width Change page width used when formatting output. -footer Change gophermap footer text (Unix new-line separated lines). -no-footer-separator Disable footer text line separator. -restrict-files New-line separated list of regex statements (checked against absolute paths) restricting file access. -description Change server description in generated caps.txt. -admin-email Change admin email in generated caps.txt. -geoloc Change geolocation in generated caps.txt. -disable-cgi Disable CGI and all executable support. -http-compat-cgi Enable HTTP CGI script compatibility (will strip HTTP headers). -http-header-buf Change max CGI read count to look for and strip HTTP headers before sending raw (bytes). -safe-path Set safe PATH variable to be used when executing CGI scripts, gophermaps and inline shell commands. -max-exec-time Change max executable CGI, gophermap and inline shell command runtime. -socket-write-buf Change socket write buffer size (bytes). -socket-read-buf Change socket read buffer size (bytes). -socket-read-max Change socket read count max (integer multiplier to socket-read-buf-max). -file-read-buf Change file read buffer size (bytes). -version Print version string. ``` # Supported gophermap item types All of the following item types are supported by Gophor, separated into grouped standards. Most handling of item types is performed by the clients connecting to Gophor, but when performing directory listings Gophor will attempt to automatically classify files according to the below types. Item types listed as `[SERVER ONLY]` means that these are item types recognised ONLY by Gophor and to be used when crafting a gophermap. They provide additional methods of formatting / functionality within a gophermap, and the output of these item types is usually converted to informational text lines before sending to connecting clients. ``` RFC 1436 Standard: Type | Treat as | Meaning -------------------------- 0 | TEXT | Regular file (text) 1 | MENU | Directory (menu) 2 | EXTERNAL | CCSO flat db; other db 3 | ERROR | Error message 4 | TEXT | Macintosh BinHex file 5 | BINARY | Binary archive (zip, rar, 7zip, tar, gzip, etc) 6 | TEXT | UUEncoded archive 7 | INDEX | Query search engine or CGI script 8 | EXTERNAL | Telnet to: VT100 series server 9 | BINARY | Binary file (see also, 5) T | EXTERNAL | Telnet to: tn3270 series server g | BINARY | GIF format image file (just use I) I | BINARY | Any format image file + | - | Redundant (indicates mirror of previous item) GopherII Standard: Type | Treat as | Meaning -------------------------- c | BINARY | Calendar file d | BINARY | Word-processing document; PDF document h | TEXT | HTML document i | - | Informational text (not selectable) p | TEXT | Page layout or markup document (plain text w/ ASCII tags) m | BINARY | Email repository (MBOX) s | BINARY | Audio recordings x | TEXT | eXtensible Markup Language document ; | BINARY | Video files Commonly used: Type | Treat as | Meaning -------------------------- . | - | Last line -- stop processing gophermap default ! | - | [SERVER ONLY] Menu title (set title ONCE per gophermap) # | - | [SERVER ONLY] Comment, rest of line is ignored - | - | [SERVER ONLY] Hide file/directory from directory listing * | - | [SERVER ONLY] Last line + directory listing -- stop processing | | gophermap and end on a directory listing = | - | [SERVER ONLY] Include or execute subgophermap, cgi-bin or regular | | file here. ``` # Compliance We aim to comply more with GopherII (see in references below). ## Item types Supported item types are listed above. Informational lines are sent as `i\t/\tnull.host\t0`. Titles are sent as `i\tTITLE\tnull.host\t0`. Web address links are sent as `h<text here>\tURL:<address>\thostname\tport`. An HTML redirect is sent in response to any requests beginning with `URL:`. ## CGI/1.1 The list of environment variables that gophor sets are as follows. RFC 3875 standard: ``` # Set GATEWAY INTERFACE SERVER_SOFTWARE SERVER_PROTOCOL CONTENT_LENGTH REQUEST_METHOD SERVER_NAME SERVER_PORT REMOTE_ADDR QUERY_STRING SCRIPT_NAME SCRIPT_FILENAME # NOT set Env Var | Reasoning ---------------------------------------------- PATH_INFO | This variable can fuck off, having to find the shortest | valid part of path heirarchy in a URI every single | CGI request so you can split and set this variable is SO | inefficient. However, if someone more knowledgeable has | other opinions or would like to point out where I'm wrong I | will happily change my tune on this. PATH_TRANSLATED | See above. AUTH_TYPE | Until we implement authentication of some kind, ignoring. CONTENT_TYPE | Very HTTP-centric relying on 'content-type' header. REMOTE_IDENT | Remote client identity information. REMOTE_HOST | Basically if the client has a resolving name (not just | IP), not really necessary. REMOTE_USER | Remote user id, not used as again no user auth yet. ``` Non-standard: ``` # Set SELECTOR DOCUMENT_ROOT REQUEST_URI PATH COLUMNS GOPHER_CHARSET ``` ## Policy files Upon request, `caps.txt` can be provided from the server root directory containing server capabiities. This can either be user or server generated. Upon request, `robots.txt` can be provided from the server root directory containing robot access restriction policies. This can either be user or server generated. ## Errors Errors are sent according to GopherII standards, terminating with a last line: `3<error text>CR-LF` Possible Gophor errors: ``` Text | Meaning 400 Bad Request | Request not understood by server due to malformed | syntax 401 Unauthorised | Request requires authentication 403 Forbidden | Request received but not fulfilled 404 Not Found | Server could not find anything matching requested | URL 408 Request Time-out | Client did not produce request within server wait | time 410 Gone | Requested resource no longer available with no | forwarding address 500 Internal Server Error | Server encountered an unexpected condition which | prevented request being fulfilled 501 Not Implemented | Server does not support the functionality | required to fulfil the request 503 Service Unavailable | Server currently unable to handle the request | due to temporary overload / maintenance ``` ## Terminating full stop Gophor will send a terminating full-stop for menus, but not for served or executed files. ## Placeholder (null) text All of the following are used as placeholder text in responses... Null selector: `-` Null host: `null.host` Null port: `0` # Todos - Set default character encoding as US-ASCII - Move filesystem_read functions to FileSystem struct function - FastCGI support - Personal user gopherspaces - Rotating logs - TLS support - Connection throttling + timeouts # Resources used Gopher-II (The Next Generation Gopher WWIS): https://tools.ietf.org/html/draft-matavka-gopher-ii-00 Gophernicus source (a great gopher daemon in C): https://github.com/gophernicus/gophernicus All of the below can be viewed from your standard web browser using floodgap's Gopher proxy: https://gopher.floodgap.com/gopher/gw RFC 1436 (The Internet Gopher Protocol: gopher://gopher.floodgap.com:70/0/gopher/tech/rfc1436.txt Gopher+ (upward compatible enhancements): gopher://gopher.floodgap.com:70/0/gopher/tech/gopherplus.txt