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+                    GNU AFFERO GENERAL PUBLIC LICENSE
+                       Version 3, 19 November 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The GNU Affero General Public License is a free, copyleft license for
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+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published
+    by the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If your software can interact with users remotely through a computer
+network, you should also make sure that it provides a way for users to
+get its source.  For example, if your program is a web application, its
+interface could display a "Source" link that leads users to an archive
+of the code.  There are many ways you could offer source, and different
+solutions will be better for different programs; see section 13 for the
+specific requirements.
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU AGPL, see
+<https://www.gnu.org/licenses/>.

diff --git a/README.md b/README.md
new file mode 100644 (file)
index 0000000..1a31099
--- /dev/null
+++ b/README.md
@@ -0,0 +1,163 @@
+# httpd.execline: a simple\* static webserver ###
+
+`httpd.execline` performs the business logic of a a static HTTP mirror. it is
+implemented in [execline](https://skarnet.org/software/execline/), in the same
+sense that you could implement the business logic of a static HTTP server in
+POSIX `sh(1)`, by wrangling Unix tools together which will actually perform the
+useful tasks you want to get done. (the advantage of POSIX `sh(1)` for this job
+is that it is far less verbose.)
+
+it takes a lot of inspiration from
+[publicfile](https://cr.yp.to/publicfile.html), while trying to allow some level
+of customization (custom HTTP headers, file-extension/MIME-type mapping
+adjustments) without requiring you to edit code; here we use using a
+filesystem-driven configuration where the hierarchical file structure amounts to
+a simple structured key-value store.
+
+\* “simple” here better describes functionality than implementation.
+
+## usage ###
+
+if you’ve ever used the publicfile `httpd`, then the setup is familiar:
+`httpd.execline` expects to be run in a directory where there is a subdirectory
+matching every hostname the dæmon serves requests for; it will simply mirror the
+contents of every file in that subdirectory it is allowed to read.
+
+in short: if `example.org` routed to your machine, then place a directory named
+`./example.org` in the directory you’re running `./httpd.execline` from
+(normally, this one).
+
+(you should consider ensuring `httpd.execline` not have any write permissions
+for the hostname-directories and their contents.)
+
+if you’re using `daemontools`-style process supervision (runit, daemontools, s6,
+or the like), *and* you already have all the dependencies (see below), including
+statically linked binaries in `./binaries` (see below), then adjust
+paramaterized values in `./run.template` and rename it to `./run`, and drop this
+directory into wherever your process supervision suite is looking for service
+directories. (if you’re not using `s6`, you should replace `s6-log` in
+`./log/run.)
+
+i haven’t used `systemd` for years, and as such, haven’t gotten around to
+writing an equivalent unit file yet.
+
+### dependencies ###
+
+you will need a superserver to actually perform any networking; i use
+[`s6-tlsserver`](https://skarnet.org/software/s6-networking/s6-tlsserver.html)
+(which itself uses
+[`s6-tcpserver`](https://skarnet.org/software/s6-networking/s6-tcpserver.html),
+which you could use if you *don’t* need TLS), from
+[`s6-networking`](https://skarnet.org/software/s6-networking/).
+
+furthermore, we assume your kernel supports `chroot`, and that you have
+userspace-level access to the feature, like GNU coreutils `chroot(1)`.
+
+#### `./binaries` ###
+
+`httpd.execline` normally chroots into the directory it runs from, making it
+difficult to use dynamically linked versions of its hard dependencies. a
+feasible configuration is to place statically linked dependencies into
+`./binaries`:
+
++ [s6-portable-utils](https://skaret.org/software/s6-portable-utils/)
+`s6-applyuidgid`, `s6-test`
++ [9base](https://tools.suckless.org/9base/):
+`tr(1)` `read(1)`, `hoc(1)`, `sed(1)`, `grep(1)`, `urlencode(1)`,
+`cleanname(1)`, `cat(1)` + [toybox](http://www.landley.net/toybox/): `wc(1)`,
+`date(1p)`, `printenv(1)`, `stat(1)`
+
+we heavily rely on plan 9 regular expression semantics for `sed(1)` and
+`grep(1)`; i expect translating them to coreutils or \*BSD userspace would be an
+effort. so long as i am writing this code for myself, i will not perform that
+effort for you.
+
+i would like to note that **s6-test receives information controlled by the
+client** and is thus **difficult to replace with a different take on
+`test(1p)`**; the use of `s6-test` here relies on the (non-standard! but very
+useful) functionality that an argument escaped with an initial backslash is
+never interpreted as an option to the program. without s6-test, handling
+user-controlled input *robustly* probably requires a workaround (piping into
+`grep -s`, perhaps?)
+
+### additional, somewhat esoteric, functionality ###
+
+#### `Content-Type`s ###
+
+`httpd.execline` expects to see a subdirectory `./data/Content-Type_table`,
+where files named after file extensions contain the MIME type such files should
+be served as. for example, `data/Content-Type_table/html` should probably
+contain the string `text/html`.
+
+this feature can be overriden on a per-file basis by making its extension have
+the form `${1}=${2}`; such files will be served with a `Content-Type` of
+`{1}/${2}` (with colons in `${1}` or `${2}` converted to periods). (for example,
+a file named `index.text=x:market` will always be served with a `Content-Type`
+of `text/x.market`.)
+
+if no `Content-Type` can be determined, `httpd.execline` falls back on
+`application/octet-stream`.
+
+#### HTTP headers ###
+
+`httpd.execline` expects `./data/` to have another subdirectory named
+`extra_headers`; and a file inside it named `default`, which may contain a
+series of `\r\n`-terminated HTTP-heades inside. `default` can be overriden on a
+per-file basis as follows:
+
+say you have a client-side webapp at `${YOUR_SITE_HERE}/webapp/index.html` and
+you need a Content Security Policy that differs from the one specified in
+`./data/extra_headers/default`; create a file named
+`./data/extra_headers/${YOUR_SITE_HERE}/webapp/index.html` containing
+`\r\n`-separated headers as necessary.
+
+the UI for this is not convenient.
+
+#### HTTP status codes ###
+
+a subdirectory of `./data/` named `status_override` can override HTTP status
+codes on a per-file basis the same way you can override HTTP headers. i use this
+for 301 redirects.
+
+again, the interface to this feature in inconvenient.
+
+## implementatoin details ###
+
+### the subscripts ###
+
+as mentioned, this script relies on several smaller subscripts, themselves often
+depedent on other subscripts. we list all subscripts in the implementation
+below, along with their dependencies:
+
++ `./get-line-from-client.execline`: read a line from the client, timing out
+after 60 seconds + `./log.execline`: log, adding information useful for
+debugging + `./http-error-resonse.execline`: send an http resposne indicating
+error, halt(, and, optionally, log that we errored)
++ `./http-start-line-parse.execline`: parse the start line and export its
+components into the environment + `./http-header-parse.execline`: parse the
+headers and export them into the environment
++ `./supported-hostname-test.execline`: test if the first argument is a supported
+hostname, to signal whether to short-circuiting during header parsing
+
+`./http-error-response.execline` depends on:
+
++ `./log.execline`
+
+`./http-start-line-parse.execline` depends on:
+
++ `./get-line-from-client.execline` + `./http-error-response.execline`: and thus
++ `./log.execline`
+
+`./http-header-parse.execline` depends on:
+
++ `./get-line-from-client.execline` + `./http-error-response.execline`: and thus
++ `./log.execline`
+
+`./supported-hostname-test.execline` depends on:
+
++ `./http-error-response.execline`: and thus + `./log.execline`
+
+looking at the dependencies, we observe that `get-line-from-client.execline` and
+`http-error-response.execline` are fundamental building blocks for the rest of
+the script. it seems worth considering consolidating the logger into the error
+response script.

diff --git a/binaries/get-line-from-client.execline b/binaries/get-line-from-client.execline
new file mode 100755 (executable)
index 0000000..f8c18c0
--- /dev/null
+++ b/binaries/get-line-from-client.execline
@@ -0,0 +1,12 @@
+#!/binaries/execlineb -WP
+# wrapper around plan 9 read(1) to timeout after 60 seconds
+# returns read(1)'s exit status
+
+trap -x -t 60000 {
+       timeout {
+               importas -i -u ! !
+               kill -- ${!}
+       }
+}
+pipeline -w { tr -d "\r" }
+read

diff --git a/binaries/headers.execline b/binaries/headers.execline
new file mode 100755 (executable)
index 0000000..e69de29

diff --git a/binaries/http-error-response.execline b/binaries/http-error-response.execline
new file mode 100755 (executable)
index 0000000..f1e9f49
--- /dev/null
+++ b/binaries/http-error-response.execline
@@ -0,0 +1,59 @@
+#!/binaries/execlineb -WS2
+# http-error-response.execline STATUS_CODE STATUS_MESSAGE [LOG_MESSAGE]
+
+fdclose 0
+foreground {
+       if -t { s6-test \${#} = 3 }
+               log.execline "fatal: ??"${1}"??: "${3}
+}
+
+# (why does `hoc -e` not work?)
+backtick -i -n Content-Length {
+       backtick -i -n message_length {
+               pipeline { s6-echo -n -- ${2} }
+               wc -c
+       }
+       importas -i -u message_length message_length
+
+       pipeline { s6-echo -- ${message_length}"*2 + 288" }
+       hoc
+}
+
+backtick -i -n Date { date -u "+%a, %d %b %Y %T GMT" }
+
+backtick -i -n extra_headers { cat data/extra_headers/default }
+
+multisubstitute {
+       importas -i -u Content-Length Content-Length
+       importas -i -u Date Date
+       importas -i -u extra_headers extra_headers
+}
+
+if {
+       s6-echo -n -- "HTTP/1.1 "${1}" "${2}"\r
+Content-Type: application/xhtml+xml; charset=utf-8\r
+Content-Length: "${Content-Length}"\r
+Date: "${Date}"\r
+"${extra_headers}"\r
+\r
+<!DOCTYPE html>
+<html xmlns=\"http://www.w3.org/1999/xhtml\" lang=\"en\" xml:lang=\"en\">
+<head>
+       <meta charset=\"utf-8\" />
+       <title>"${2}"</title>
+       <style>html {
+       background: #FFFFEA;
+       color: #303020;
+       font-family: Tinos, serif;
+       text-align: center;
+}</style>
+</head>
+<body>
+<h1>"${2}"</h1>
+</body>
+</html>
+"
+}
+# hack: write(3p) is unsafe
+#
+s6-sleep -m 512

diff --git a/binaries/http-header-parse.execline b/binaries/http-header-parse.execline
new file mode 100755 (executable)
index 0000000..09d9a58
--- /dev/null
+++ b/binaries/http-header-parse.execline
@@ -0,0 +1,191 @@
+#!/binaries/execlineb -W
+## `http-header-parse.execline supported-hostname-test [rest of program]`
+#
+# expects a series of http headers from standard input  
+# exits syntax error otherwise
+#
+# current hard dependencies on external ./httpd.execline subscripts:
+# 
+# + ./get-line-from-client.execline
+# + ./http-error-response.execline: and thus,
+# + ./log.execline
+#
+# the first argument is a program to call when parsing a `Host` header
+# for the first time (usually the first line, but this convention is not
+# required); it should exit zero on a hostname the program supports,
+# and nonzero otherwise (in which case this program halts execution
+# immediately.)
+#
+# on a successful parse, we export environment variables of the form
+# `http_header_parse_${http_header}` and exec(3ps) into the remaining
+# program (excluding the first argument, of course!)  
+# if we do not exec(3p) into that argument list, the program will halt
+# completely, and **the currently exported environment variables will be
+# unavailable**; thus the expectation that the remaining script will be
+# passed as arguments, execline-style.  
+# this makes handling error cases difficult to do without hard depending
+# on other `httpd.execline` subscripts.  
+# TODO: [hard, design problem]: export failure information into the
+# environment, exec(3p)ing into the remaining program instead of exiting
+# immediately
+#
+# dealing with Host headers makes this script much more complicated than
+# it already needed to be. (turns out, existing servers often just ignore
+# some of the MUSTs we respect here! dammit…)
+#
+
+# the remaining program is supplied **after an initial argument we must
+# preserve and use**. we have not found a way to handle this without losing
+# efficiency (see the shebang (the "#!" line, on line 1))
+#
+importas supported_hostname_test 1
+shift
+elgetpositionals
+emptyenv -P
+
+# the overall plan is a simple recursive(!) script:
+#
+# + on an empty line, exec into the remaining program
+# + on a nomempty line, parse for a single header
+#
+# we use recursion to permanently modify the environment of the current
+# process for the remaining script (passed as arugments) to read from; we
+# simply cannot do this with execline’s built-in looping construct (which
+# performs the equivalent of spawning a *subshell* on every iteration)  
+# this is a heavy weakness for implementing actual program logic; we expect
+# the author of execline to never provide a convenient way to circumvent this
+# problem, as supporting Actual Programming Logic is out of scope for the
+# language (for example: see all the use of external tools `grep` and `sed`
+# throughout `httpd.execline`, as execline’s string manipulation tools are
+# (deliberately) very underpowered)
+#
+
+backtick -i -n current_line { get-line-from-client.execline }
+
+### terminating case: empty line
+#
+# exec(3p) the remaining program
+# 
+ifelse {
+       pipeline { printenv current_line }
+       grep -s "^ *$"
+}
+{
+       # the client MUST send a Host header, halt otherwise
+       #
+       ifelse { s6-test ! -v http_header_parse_Host }
+       {
+               http-error-response.execline
+                       400
+                       "syntax error"
+                       "client request lacking Host header"
+       }
+
+       unexport current_line
+       unexport header_name
+       unexport header_contents
+       ${@}
+}
+
+### recursive case: parse for a header
+#
+# after parsing, exec(3p) this script with the hostname validating
+# subscript, then the remaing program, as arguments
+# 
+backtick -I -n header_name {
+       pipeline { printenv current_line }
+       pipeline { sed -n "s/^([^ :]+):.*/\\1/p" }
+       read
+}
+backtick -I -n header_contents {
+       pipeline { printenv current_line }
+       # strip spaces or tabs from end of line  
+       # then print the second token verbatim  
+       #
+       # whitespace between header name and contents is optional
+       #
+       pipeline { sed -n "s/(  )*$//; s/^[^ ]+ *([^ ].*)/\\1/p" }
+       read
+}
+ifelse {
+       s6-test ! -v header_name -o
+               ! -v header_contents
+}
+{
+       importas -i current_line current_line
+       http-error-response.execline
+               400
+               "syntax error"
+               "http-header-parse.execline: bad header line: \""${current_line}\"
+}
+
+multisubstitute {
+       importas -i -u header_name header_name
+       importas -i -u header_contents header_contents
+}
+
+#### special case: host header
+#
+# short circuits the program  
+# TODO: [hard, design problem]: short circuit but exec(3p) into the
+# remaining program
+# 
+ifelse { s6-test \${header_name} = Host }
+{
+       # we MUST 400 on multiple Host headers
+       #
+       ifelse { s6-test -v http_header_parse_Host }
+       {
+               http-error-response.execline
+                       400
+                       "syntax error"
+                       "http-header-parse.execline: multiple Host headers!??"
+       }
+
+       # validate hostnames, exiting on syntactically illegal ones
+       #
+       ifelse {
+               define hexadecimal "[0-9a-fA-F]"
+               multisubstitute {
+                       # + dns-resolved hostname
+                       define domain_name "[a-zA-Z0-9\-.]+"
+
+                       # + ipv6 address (TODO: handle robustly)
+                       define approximate_ipv6 "("${hexadecimal}"+)?(::"${hexadecimal}")+"
+
+                       # + port string
+                       define port ":[0-9]+"
+               }
+               #
+               # as we understand it, a valid ipv4 address is always a valid
+               # domain name address, so we do not actually have to handle
+               # that…
+               #
+               pipeline { s6-echo -n -- ${header_contents} }
+               grep -sv "^ *(("${domain_name}")|("${approximate_ipv6}"))("${port}")? *$"
+       }
+       {
+               http-error-response.execline
+                       400
+                       "syntax error"
+                       "illegal host: "\"${header_contents}\"
+       }
+
+       # short circuit on unsupported hostnames
+       #
+       ifelse -n { ${supported_hostname_test} ${header_contents} }
+       {
+               fdclose 0
+               exit 0
+
+       }
+       export http_header_parse_${header_name} ${header_contents}
+       ${0}
+               ${supported_hostname_test}
+               ${@}
+}
+
+export http_header_parse_${header_name} ${header_contents}
+${0}
+       ${supported_hostname_test}
+       ${@}

diff --git a/binaries/http-start-line-parse.execline b/binaries/http-start-line-parse.execline
new file mode 100755 (executable)
index 0000000..e76fd3c
--- /dev/null
+++ b/binaries/http-start-line-parse.execline
@@ -0,0 +1,50 @@
+#!/binaries/execlineb -WS1
+# expects a start line from an http request from standard input  
+# exits syntax error otherwise
+#
+# current hard dependencies on `httpd.execline` subscripts:
+#
+# + ./get-line-from-client.execline
+# + ./http-error-response.execline: and, thus
+# + ./log.execline
+#
+# on success, exports
+#
+# + http_start_line_parse_method
+# + http_start_line_parse_resource
+# + http_start_line_parse_version
+#
+# containing the request's method, requested resource, and http version
+# it then exec(3p)s into its command line
+
+backtick -i -n start_line { get-line-from-client.execline }
+backtick -I -n http_start_line_parse_method {
+       pipeline { printenv start_line }
+       pipeline { sed -n "s@^(CONNECT|DELETE|GET|HEAD|OPTIONS|PATCH|POST|PUT|TRACE) +.*@\\1@p" }
+       read
+}
+backtick -I -n http_start_line_parse_resource {
+       pipeline { printenv start_line }
+       pipeline { sed -n "s@^[^ ]+ +(/[^ ]*) +.*@\\1@p" }
+       read
+}
+backtick -I -n http_start_line_parse_version {
+       pipeline { printenv start_line }
+       pipeline { sed -n "s@.*HTTP/([0-9]\.[0-9]) *@\\1@p" }
+       read
+}
+
+importas -i -u start_line start_line
+ifelse {
+       s6-test ! -v http_start_line_parse_method -o
+               ! -v http_start_line_parse_resource -o
+               ! -v http_start_line_parse_version
+}
+{
+       http-error-response.execline
+               400
+               "syntax error"
+               "http-start-line-parse.execline: (bad) start line: \""${start_line}\"
+}
+
+${@}

diff --git a/binaries/httpd.execline b/binaries/httpd.execline
new file mode 100755 (executable)
index 0000000..a7a6e93
--- /dev/null
+++ b/binaries/httpd.execline
@@ -0,0 +1,269 @@
+#!/usr/local/skarnet/bin/execlineb -WP
+## `httpd.execline`: a simple static web server ###
+# 
+# i would like to note that simplicity is relative; the *implementation* of
+# this simple functionality is not exactly simple. there are several subscripts
+# with sufficently complex and (in all but one case) reusable functionality
+# that we separate them out.  
+# unfortunately, many themselves are (currently )dependent on other subscripts.
+
+### the http/1.1 protocol, oversimplified ###
+#
+# a client sends a request that normally looks something like
+#
+# ```
+# > [http_method] [resource] [http version]\r
+# > Host: [hostname]\r
+# > [quite possibly many other headers]\r
+# > \r
+# ```
+#
+# (note the `\r`s before newlines.  
+# (also: the Host header does not *have* to be the second line)
+#
+# we respond to the client appropriately, using to the following template:
+#
+# ```
+# < HTTP/1.1 [status code] [status message]\r
+# < Content-Type: [MIME type of the message body]\r
+# < Content-Length: [size of message body in bytes]\r
+# < Date: [the time as of this response]\r
+# < [Last-Modified: [date of the resource’s last revision]]\r
+# < \r
+# < [content, sent verbatim]
+# ```
+#
+# we do not follow the http/1.1 protocol precisely, but it is enough to satisfy
+# web browsers and tools like `curl(1)`, and to handle misbehaving clients.
+#
+
+### brief httpd.execline overview ##
+#
+# 1. sandboxing (paranoia?)
+# 2. read, validate the start line and Host header sent by the client
+# 3. find resource, determine its filetype
+# 4. send response to client
+#
+
+#### 1. sandboxing ###
+#
+# this recreates a security measure we picked up from `publicfile`: if this
+# server should somehow be hijacked, it will not be able to escape the
+# directory it runs in, and it will be running as an unpriveleged user  
+# in the setup of this server, the user `httpd` owns no files or directories in
+# the change-rooted directory, nor does it have any write permissions for those
+# files and directories, so a hijacked process will not be able to do very much
+export PATH /binaries
+chroot .
+s6-applyuidgid -U -z
+
+# see `./log.execline`
+export program_name httpd.execline
+
+# see end of script: handle crashes (or syntax errors in this script,) cleanly
+if -X -n -t {
+       #### 2. read from client, with interspersed validation ###
+       ##### 2.1. start line ###
+       http-start-line-parse.execline
+       multisubstitute {
+               importas -i -u method http_start_line_parse_method
+               importas -i -u requested_resource http_start_line_parse_resource
+       }
+       ifelse -n {
+               s6-test \${method} = HEAD -o
+                       \${method} = GET
+       }
+       {
+               http-error-response.execline
+                       501
+                       "method not implemented"
+                       "unsupported method: \""${method}\"
+       }
+
+       ##### 2.2. headers ###
+       http-header-parse.execline
+               supported-hostname-test.execline
+       # if we reach this point, all headers from the client request will be
+       # available in environment variables named after the header, in the form
+       # http_header_parse_${Header_Name}.  
+       # that said, we use only `Host` here.  
+       # `/http-header-parse.execline` is implemented in a wonderfully silly way
+       importas -i -u hostname http_header_parse_Host
+
+       # we don’t need to read anything more from the client
+       fdclose 0
+
+       foreground {
+               log.execline
+                       "info:"
+                       "client request:"
+                       "for \""${hostname}\"":"
+                       \"${method}\"
+                       \"${requested_resource}\"
+       }
+
+       #### 3. process requested resource ###
+       backtick -i -n resource {
+               backtick -i -n candidate_resource {
+                       backtick -in with_dot_and_dot_dot {
+                               pipeline { s6-echo -n -- ${requested_resource} }
+                               #
+                               # strip query string, or resource location
+                               #
+                               pipeline { sed "s/[?#].*//; s@/\\.\\.?/@/@g" }
+                               # decode url-encodings, if any  
+                               urlencode -d
+                       }
+                       importas -i -u with_dot_and_dot_dot with_dot_and_dot_dot
+                       # include the hostname in the final resource name
+                       #
+                       if { s6-echo -n -- ${hostname} }
+                       # handle dot and dot-dot directory semantics  
+                       # we prepend the hostname to the result, ensuring
+                       # `${resource}` will route to somewhere inside the
+                       # subdirectory named after the host
+                       cleanname ${with_dot_and_dot_dot}
+               }
+               importas -i -u candidate_resource candidate_resource
+
+               # `${directory}` -> `${directory}/index.xhtml`  
+               ifelse { s6-test -d \${candidate_resource} }
+               {
+                       s6-echo -n -- ${candidate_resource}/index.xhtml
+               }
+                       s6-echo -n -- ${candidate_resource}
+       }
+       importas -i resource resource
+       ifelse { s6-test ! -r \${resource} }
+       {
+               http-error-response.execline
+                       404
+                       "not found"
+                       "attempted: \""${resource}\"
+       }
+
+       #### 4. send response ###
+       ##### 4.1. determine found resource's Content-Type ###
+       #
+       backtick -i -n Content-Type {
+               backtick -D "no.extension" -n extension {
+                       pipeline { printenv resource }
+                       # strip everything up to the non-periods after the final
+                       # period in the string
+                       #
+                       pipeline { sed -n "s/.+\\.([^.]+)$/\\1/p" }
+                       read
+               }
+
+               # publicfile-style custom filetypes: `file.{1}={2}` is served
+               # with `Content-Type` `${1}/${2}`. colons in the extension are
+               # transformed into periods, allowing files like
+               # `index.text=x:market` being served as `text/x.market`
+               #
+               # this overrides any other Content-Type determination mechanism
+               ifelse {
+                       pipeline { printenv extension }
+                       # this regex matches exactly what `publicfile` does
+                       #
+                       grep -s "[a-zA-Z0-9]+=[^=]+$"
+               }
+               {
+                       pipeline { printenv extension }
+                       tr := ./
+               }
+
+               # use `./data/Content-Type_table` as a key-value store: files with
+               # the name ${extension} map to the `Content-Type` embedded in
+               # their contents. for example, `./data/Content-Type_table/xhtml`
+               # contains the text “application/xhtml+xml” (with no newline)  
+               # (it is fine if the file contains a single newline at the end)
+               #
+               # if no key exists with the extension’s name, we fall back on
+               # “application/octet-stream”, as we should
+               importas -i -u extension extension
+               ifelse { s6-test -r \\./data/Content-Type_table/${extension} }
+               {
+                       cat ./data/Content-Type_table/${extension}
+               }
+                       s6-echo -n -- application/octet-stream
+       }
+
+       ##### 4.2. miscellaneous headers ###
+       # TODO: separate this out, ideally make reusable
+
+       # file length in bytes: SHOULD be provided
+       backtick -i -n Content-Length { stat -c%s -- ${resource} }
+
+       # "[weekday], [month-day] [month] [year] [hours:minutes:seconds] GMT"  
+       # (example: "Tue, 03 Mar 2020 21:06:08 GMT")
+       define date_format "+%a, %d %b %Y %T GMT"
+
+       # the date the resource was last modified SHOULD be provided
+       backtick -i -n Last-Modified {
+               backtick -i -n seconds_since_epoch { stat -c%Y -- ${resource} }
+               importas -i -u seconds_since_epoch seconds_since_epoch
+               date -d @${seconds_since_epoch} -u ${date_format}
+       }
+
+       # current time of response: SHOULD be provided (why?)
+       backtick -i -n Date { date -u ${date_format} }
+
+
+       # allow for arbitrary HTTP header and HTTP status code overrides.
+       # for an example where the former might be useful, consider Content
+       # Security Policy; for the latter, consider HTTP 301 redirects
+       #
+       # be warned!! we do not validate these overrides!
+       backtick -i -n extra_headers {
+               ifelse { s6-test -r \\data/extra_headers/override/${resource} }
+               {
+                       cat data/extra_headers/override/${resource}
+               }
+                       cat data/extra_headers/default
+       }
+
+       backtick -D "200 ok" -n status_code_and_message {
+               if { s6-test -r \\data/status_override/${resource} }
+                       cat data/status_override/${resource}
+       }
+
+       ##### 4.3. send the response ###
+       multisubstitute {
+               importas -i -u status_code_and_message status_code_and_message
+               importas -i -u Content-Length Content-Length
+               importas -i -u Content-Type Content-Type
+               importas -i -u Date Date
+               importas -i -u Last-Modified Last-Modified
+               importas -i -u extra_headers extra_headers
+       }
+       if {
+               s6-echo -n -- "HTTP/1.1 "${status_code_and_message}"\r
+Content-Type: "${Content-Type}"\r
+Content-Length: "${Content-Length}"\r
+Last-Modified: "${Last-Modified}"\r
+Date: "${Date}"\r
+"${extra_headers}"\r
+\r
+"
+       }
+       foreground {
+               if -t { s6-test \${method} = GET }
+                       cat ${resource}
+       }
+       # hack: write(3p) does not guarantee that all the
+       # content actually gets written before this process
+       # closes, and will not indicate in any way if a full
+       # write did not happen. a half second seems to be
+       # Long Enough to protect against this… hopefully…
+       s6-sleep -m 512
+       # TODO: (?) persistent connections? (recursion??)
+}
+       ##### end of script  
+       # catches crashes (and syntax errors,,), and other unexpected things  
+       # useful for debugging! otherwise, clients might do strange things
+       #
+       # probably a bad sign this is still left in lol
+       http-error-response.execline
+               500
+               "internal server error"
+               "(i/o error? timeout?)"

diff --git a/binaries/log.execline b/binaries/log.execline
new file mode 100755 (executable)
index 0000000..aecc5d1
--- /dev/null
+++ b/binaries/log.execline
@@ -0,0 +1,13 @@
+#!/binaries/execlineb -WS1
+
+multisubstitute {
+       importas -D "" program_name program_name
+       importas -D "no client process id?" process_id process_id
+       importas -D "no remote ip address (not being run from an UCPSI server?)" remote_ip TCPREMOTEIP
+       importas -D "no remote port (not being run from an UCPSI server?)" remote_port TCPREMOTEPORT
+}
+
+fdmove -c 1 2
+s6-echo --
+       ${program_name}": pid "${process_id}" ip "${remote_ip}":"${remote_port}":"
+       ${@}

diff --git a/binaries/supported-hostname-test.execline b/binaries/supported-hostname-test.execline
new file mode 100755 (executable)
index 0000000..80a7af9
--- /dev/null
+++ b/binaries/supported-hostname-test.execline
@@ -0,0 +1,54 @@
+#!/binaries/execlineb -WS1
+# `supported-hostname-test.execline hostname`
+# 
+# tests if `hostname` is supported by this server, by checking if
+# a directory by that exact name exists in the current working directory  
+# immediately 404s otherwise
+#
+# hard depends on these external `httpd.execline` subscripts:
+#
+# + ./http-error-response.execline: and thus,
+# + ./log.execline
+#
+
+# protect Special Subdirectories
+#
+# + `/binaries` is change root--available static binaries and helper scripts
+# + `tcp-access-rules` for the pseudo-firewall
+# + `.` and `..` are to disallow clients being Naughty
+# + the other directories are for process supervision things
+#
+# note: general policy for this server is to 404 where we "should" 403.
+#
+ifelse {
+       s6-test \${1} = binaries -o
+               \${1} = data -o
+               \${1} = event -o
+               \${1} = log -o
+               \${1} = supervise -o
+               \${1} = tcp-access-rules -o
+               \${1} = . -o
+               \${1} = ..
+}
+{
+       if {
+               http-error-response.execline
+                       404
+                       "not found"
+                       "illegal host: \""${1}\"
+       }
+       exit 1
+}
+# reject unsupported hostnames
+#
+ifelse { s6-test ! -d \${1} }
+{
+       if {
+               http-error-response.execline
+                       404
+                       "not found"
+                       "unsupported host: \""${1}\"
+       }
+       exit 1
+}
+exit 0

diff --git a/data/Content-Type_table/c b/data/Content-Type_table/c
new file mode 100644 (file)
index 0000000..4eed93f
--- /dev/null
+++ b/data/Content-Type_table/c
@@ -0,0 +1 @@
+text/x.c; charset=utf-8
\ No newline at end of file

diff --git a/data/Content-Type_table/css b/data/Content-Type_table/css
new file mode 100644 (file)
index 0000000..5bc394d
--- /dev/null
+++ b/data/Content-Type_table/css
@@ -0,0 +1 @@
+text/css
\ No newline at end of file

diff --git a/data/Content-Type_table/execline b/data/Content-Type_table/execline
new file mode 100644 (file)
index 0000000..1ce14d2
--- /dev/null
+++ b/data/Content-Type_table/execline
@@ -0,0 +1 @@
+text/x.execline; charset=utf-8
\ No newline at end of file

diff --git a/data/Content-Type_table/html b/data/Content-Type_table/html
new file mode 100644 (file)
index 0000000..f79d269
--- /dev/null
+++ b/data/Content-Type_table/html
@@ -0,0 +1 @@
+text/html; charset=utf-8
\ No newline at end of file

diff --git a/data/Content-Type_table/ico b/data/Content-Type_table/ico
new file mode 100644 (file)
index 0000000..cadc3b9
--- /dev/null
+++ b/data/Content-Type_table/ico
@@ -0,0 +1 @@
+image/png
\ No newline at end of file

diff --git a/data/Content-Type_table/jpeg b/data/Content-Type_table/jpeg
new file mode 100644 (file)
index 0000000..29e455a
--- /dev/null
+++ b/data/Content-Type_table/jpeg
@@ -0,0 +1 @@
+image/jpeg
\ No newline at end of file

diff --git a/data/Content-Type_table/jpg b/data/Content-Type_table/jpg
new file mode 100644 (file)
index 0000000..29e455a
--- /dev/null
+++ b/data/Content-Type_table/jpg
@@ -0,0 +1 @@
+image/jpeg
\ No newline at end of file

diff --git a/data/Content-Type_table/js b/data/Content-Type_table/js
new file mode 100644 (file)
index 0000000..54eef4f
--- /dev/null
+++ b/data/Content-Type_table/js
@@ -0,0 +1 @@
+application/js
\ No newline at end of file

diff --git a/data/Content-Type_table/market b/data/Content-Type_table/market
new file mode 100644 (file)
index 0000000..70a0914
--- /dev/null
+++ b/data/Content-Type_table/market
@@ -0,0 +1 @@
+text/x.market; charset=utf-8
\ No newline at end of file

diff --git a/data/Content-Type_table/png b/data/Content-Type_table/png
new file mode 100644 (file)
index 0000000..cadc3b9
--- /dev/null
+++ b/data/Content-Type_table/png
@@ -0,0 +1 @@
+image/png
\ No newline at end of file

diff --git a/data/Content-Type_table/txt b/data/Content-Type_table/txt
new file mode 100644 (file)
index 0000000..a2ef29a
--- /dev/null
+++ b/data/Content-Type_table/txt
@@ -0,0 +1 @@
+text/plain; charset=utf-8
\ No newline at end of file

diff --git a/data/Content-Type_table/xhtml b/data/Content-Type_table/xhtml
new file mode 100644 (file)
index 0000000..1140ed9
--- /dev/null
+++ b/data/Content-Type_table/xhtml
@@ -0,0 +1 @@
+application/xhtml+xml; charset=utf-8
\ No newline at end of file

diff --git a/data/extra_headers/default.example b/data/extra_headers/default.example
new file mode 100644 (file)
index 0000000..12184e2
--- /dev/null
+++ b/data/extra_headers/default.example
@@ -0,0 +1,2 @@
+Strict-Transport-Security: max-age=2175984000\r
+X-Clacks-Overhead: GNU Natalie Nguyen\r

diff --git a/log/run b/log/run
new file mode 100755 (executable)
index 0000000..330b8e6
--- /dev/null
+++ b/log/run
@@ -0,0 +1,4 @@
+#!/usr/local/skarnet/bin/execlineb -WP
+
+s6-setuidgid httpd
+s6-log t /log/httpd

diff --git a/run.template b/run.template
new file mode 100755 (executable)
index 0000000..342814e
--- /dev/null
+++ b/run.template
@@ -0,0 +1,37 @@
+#!/bin/execlineb -WP
+#
+# example `run` script for daemontools-style process supervision
+# replace contents in `${}` and copy to `./run`
+
+# for logging: redirect standard error to standard output
+fdmove -c 2 1
+
+# clear the entire environment except for PATH
+emptyenv -p
+
+# required by `s6-tld`
+export CERTFILE /etc/letsencrypt/live/${YOUR_SITE_HERE}/fullchain.pem
+export KEYFILE /etc/letsencrypt/live/${YOUR_SITE_HERE}/privkey.pem
+
+# we run as root until very early in `./binaries/httpd.execline` and `s6-tlsd`; this sets up environment variables for dropping priveleges
+#
+# sample numerical user ID for user `s6-tlsd` runs as (after reading certificate)
+export TLS_UID ${YOUR_TLS_USER_USER_ID_HERE}
+export TLS_GID ${YOUR_TLS_USER_GROUP_ID_HERE}
+# user for ./binaries/httpd.execline (after `chroot(8)`)
+s6-envuidgid ${YOUR_HTTP_USER_NAME_HERE}
+
+# somewhat verbose command line to make the httpd able to log the PID reported by s6-tcpserver  
+# (s6-tcpserver prints the pid of `s6-tlsd`, but `./httpd.execline` is a child of said PID)
+s6-tcpserver4
+       # for logging: log beginning and end of every connection
+       -v 2
+       # allow 1000 simultaneous connections; allow them all to be from the same ip address
+       -c 1000 -C 1000
+       --
+       ${YOUR_IP_ADDRESS_HERE}
+       443
+               getpid process_id # for logging
+               s6-tlsd
+                       --
+                               ./binaries/httpd.execline