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 concurrency and efficiency in mind.

• ZERO external dependencies.

• Security focused -- by default chroots to server directory and drops privileges, though -rootless flag may be applied to skip these steps (e.g. when running on a shared host).

• LRU file caching -- with user-controlled cache size, max cached file size and cache refresh frequency.

• Insert files within gophermaps, including automating reflowing of lines longer than (user definable) page width.

• Automatic replacement of $hostname or $port with the information of the host the client is connecting to.

• User supplied footer text appended to gophermaps and directory listings.

• Item type characters beyond RFC 1436 standard (see below).

• Separate system and access logging with output to file if requested (or to disable both).

Usage

gophor [args]
       -root-dir            Change server root directory.

       -port                Change server NON-TLS listening port.

       -hostname            Change server hostname (FQDN, used to craft dir
                            lists).

       -bind-addr           Change server bind-address (used in creating
                            socket).

       -user                Drop to supplied user's UID and GID permissions
                            before execution.

       -system-log          Path to gophor system log file, else use stderr.

       -access-log          Path to gophor access log file, else use stderr.

       -cache-check         Change file-cache freshness check frequency.

       -cache-size          Change max no. files in file-cache.

       -cache-file-max      Change maximum allowed size of a cached file.

       -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
                            restricting files from showing in directory listing.

       -description         Change server description in generated caps.txt.

       -admin-email         Change admin email in generated caps.txt.

       -geoloc              Change geolocation in generated caps.txt.

       -rootless            Run without root privileges (no chroot, no privilege
                            drop, no restricted ports).

       -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
 !   |     -    | [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 -- stop processing gophermap default
 *   |     -    | [SERVER ONLY] Last line + directory listing -- stop processing
     |          |               gophermap and end on a directory listing
 =   |     -    | [SERVER ONLY] Include subgophermap / regular file here. Prints
     |          |               and formats file / gophermap in-place

Planned to be supported:
Type | Treat as | Meaning
 $   |     -    | [SERVER ONLY] Execute shell command and print stdout here

Compliance

Item types

Supported item types are listed above.

Informational lines are sent as i<text here>\t/\tnull.host\t0.

Titles are sent as i<title text>\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:.

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 files.

Placeholder text

All of the following are used as placeholder text in responses...

Null selector: -

Null host: null.host

Null port: 0

Todos

Shortterm:

• Set default charset -- need to think about implementation here...

• Neaten codebase after recent RequestPath addition.

• Fix file cache only updating if main gophermap changes (but not sub files) -- need to either rethink how we keep track of files, or rethink how gophermaps are stored in memory.

Longterm:

• Finish inline shell scripting support -- current thinking is to only allow during rootless operation.

• Rotating logs -- have a check on start for a file-size, rotate out if the file is too large. Possibly checks during run-time too?

• Add last-mod-time to directory listings -- have global time parser object, maybe separate out separate global instances of objects (e.g. worker related, cache related, config related?)

• TLS support -- requires a rethink of how we're passing port functions generating gopher directory entries, also there is no definitive standard for this yet implemented these changes! figuring out gopher + TLS itself though? no luck yet.

• Connection throttling + timeouts -- thread to keep track of list of recently connected IPs. Keep incremementing connection count and only remove from list when lastIncremented time is greater than timeout

• More closely follow GoLang built-in net/http code style for worker -- just a neatness thing, maybe bring some performance improvements too and a generally different way of approaching some of the solutions to problems we have

Please note

During the initial writing phase the quality of git commit messages may be low and many changes are likely to be bundled together at a time, just because the pace of development right now is rather break-neck.

As soon as we reach a stable point in development, or if other people start contributing issues or PRs, whichever comes first, this will be changed right away.

Resources used

Gopher-II (The Next Generation Gopher WWIS): https://tools.ietf.org/html/draft-matavka-gopher-ii-00

Gophernicus supported item types: https://github.com/gophernicus/gophernicus/blob/master/README.gophermap

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