1//
  2// Copyright (c) 2019 Ted Unangst <tedu@tedunangst.com>
  3//
  4// Permission to use, copy, modify, and distribute this software for any
  5// purpose with or without fee is hereby granted, provided that the above
  6// copyright notice and this permission notice appear in all copies.
  7//
  8// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  9// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 10// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 11// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 12// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 13// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 14// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 15
 16package main
 17
 18import (
 19	"bytes"
 20	"errors"
 21	"net"
 22	"net/http"
 23	"net/rpc"
 24	"os"
 25	"os/exec"
 26	"os/signal"
 27	"strings"
 28	"sync"
 29	"syscall"
 30
 31	"humungus.tedunangst.com/r/webs/gate"
 32	"humungus.tedunangst.com/r/webs/image"
 33)
 34
 35type Shrinker struct {
 36}
 37
 38type ShrinkerArgs struct {
 39	Buf    []byte
 40	Params image.Params
 41}
 42
 43type ShrinkerResult struct {
 44	Image *image.Image
 45}
 46
 47var shrinkgate = gate.NewLimiter(4)
 48
 49func (s *Shrinker) Shrink(args *ShrinkerArgs, res *ShrinkerResult) error {
 50	shrinkgate.Start()
 51	defer shrinkgate.Finish()
 52	img, err := image.Vacuum(bytes.NewReader(args.Buf), args.Params)
 53	if err != nil {
 54		return err
 55	}
 56	res.Image = img
 57	return nil
 58}
 59
 60func backendSockname() string {
 61	return dataDir + "/backend.sock"
 62}
 63
 64var bomFuck = []byte{0xef, 0xbb, 0xbf}
 65
 66func isSVG(data []byte) bool {
 67	if bytes.HasPrefix(data, bomFuck) {
 68		data = data[3:]
 69	}
 70	ct := http.DetectContentType(data)
 71	if strings.HasPrefix(ct, "text/xml") || strings.HasPrefix(ct, "text/plain") {
 72		if bytes.HasPrefix(data, []byte("<svg ")) || bytes.HasPrefix(data, []byte("<!DOCTYPE svg PUBLIC")) {
 73			return true
 74		}
 75	}
 76	return ct == "image/svg+xml"
 77}
 78
 79func imageFromSVG(data []byte) (*image.Image, error) {
 80	if bytes.HasPrefix(data, bomFuck) {
 81		data = data[3:]
 82	}
 83	if len(data) > 100000 {
 84		return nil, errors.New("my svg is too big")
 85	}
 86	svg := &image.Image{
 87		Data:   data,
 88		Format: "svg+xml",
 89	}
 90	return svg, nil
 91}
 92
 93func callshrink(data []byte, params image.Params) (*image.Image, error) {
 94	if isSVG(data) {
 95		return imageFromSVG(data)
 96	}
 97	cl, err := rpc.Dial("unix", backendSockname())
 98	if err != nil {
 99		return nil, err
100	}
101	defer cl.Close()
102	var res ShrinkerResult
103	err = cl.Call("Shrinker.Shrink", &ShrinkerArgs{
104		Buf:    data,
105		Params: params,
106	}, &res)
107	if err != nil {
108		return nil, err
109	}
110	return res.Image, nil
111}
112
113func bigshrink(data []byte) (*image.Image, error) {
114	params := image.Params{
115		LimitSize: 14200 * 4200,
116		MaxWidth:  2600,
117		MaxHeight: 2048,
118		MaxSize:   768 * 1024,
119	}
120	return callshrink(data, params)
121}
122
123func shrinkit(data []byte) (*image.Image, error) {
124	params := image.Params{
125		LimitSize: 4200 * 4200,
126		MaxWidth:  2048,
127		MaxHeight: 2048,
128	}
129	return callshrink(data, params)
130}
131
132func orphancheck() {
133	var b [1]byte
134	os.Stdin.Read(b[:])
135	dlog.Printf("backend shutting down")
136	os.Exit(0)
137}
138
139func backendServer() {
140	dlog.Printf("backend server running")
141	go orphancheck()
142	signal.Ignore(syscall.SIGINT)
143	shrinker := new(Shrinker)
144	srv := rpc.NewServer()
145	err := srv.Register(shrinker)
146	if err != nil {
147		elog.Panicf("unable to register shrinker: %s", err)
148	}
149
150	sockname := backendSockname()
151	err = os.Remove(sockname)
152	if err != nil && !os.IsNotExist(err) {
153		elog.Panicf("unable to unlink socket: %s", err)
154	}
155
156	lis, err := net.Listen("unix", sockname)
157	if err != nil {
158		elog.Panicf("unable to register shrinker: %s", err)
159	}
160	err = setLimits()
161	if err != nil {
162		elog.Printf("error setting backend limits: %s", err)
163	}
164	securitizebackend()
165	srv.Accept(lis)
166}
167
168func runBackendServer() {
169	r, w, err := os.Pipe()
170	if err != nil {
171		elog.Panicf("can't pipe: %s", err)
172	}
173	proc := exec.Command(os.Args[0], reexecArgs("backend")...)
174	proc.Stdout = os.Stdout
175	proc.Stderr = os.Stderr
176	proc.Stdin = r
177	err = proc.Start()
178	if err != nil {
179		elog.Panicf("can't exec backend: %s", err)
180	}
181	workinprogress++
182	var mtx sync.Mutex
183	go func() {
184		<-endoftheworld
185		mtx.Lock()
186		defer mtx.Unlock()
187		w.Close()
188		w = nil
189		readyalready <- true
190	}()
191	go func() {
192		err := proc.Wait()
193		mtx.Lock()
194		defer mtx.Unlock()
195		if w != nil {
196			elog.Printf("lost the backend: %s", err)
197			w.Close()
198		}
199	}()
200}