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4 years ago · b648598bba
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--- a/21
+++ b/21
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+The MIT License (MIT)
+
+Copyright (c) 2019 Tyler Sommer <contact@tylersommer.pro>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
--- a/README.md
+++ b/README.md
@ -0,0 +1,66 @@
+eok.vin
+=======
+
+Private, single-user, self-hosted URL shortening service.
+
+> "These are words." -- anonymous
+
+Usage
+----- 
+
+eokvin enforces TLS, relying on LetsEncrypt to issue certificates
+automatically by default. Short URLs are created using a basic POST API
+and expire after a set time.
+
+```
+Usage of ./eokvin:
+  -cert-file string
+        TLS certificate chain file, blank for autocert
+  -hash-token string
+        If given, the sha256 of the given value will be printed
+  -host string
+        Listen hostname (default "eok.vin")
+  -http-port int
+        HTTP listen port (default 80)
+  -key-file string
+        TLS private key file, blank for autocert
+  -port int
+        HTTPS listen port (default 443)
+  -token string
+        SHA256 of the secret token, used to authenticate
+```
+
+### Important notes
+
+* A secret token is required to create new short URLs, given in the `-token`
+  command-line option. This must be the hexadecimal string representation of
+  the token (ie. 64 characters long) in question.
+* Use the `-hash-token` command-line option to print the SHA256 result 
+  (formatted as the `-hash` option expects) of a given phrase.
+  ```
+  $ ./eokvin -hash-token "this is a really long and arbitrary input"
+  d1e6d468c926d9167693c190688d964fec0258c4ef4a4e1ed9cd87ea9c682156
+  ```
+* To avoid using LetsEncrypt (for example, when running locally), use a
+  standard cert and key by using the `-cert-file` and `-key-file` 
+  command-line options.
+
+
+### Create a short URL
+
+Submit a POST request with Content-Type `application/x-www-form-encoded`
+to `/new` with the request body containing:
+
+1. The original, plaintext secret token as `token=<plain token>`.
+2. The real URL to redirect to for the new short URL as `url=<redirect-url>`.
+
+Upon success, the server will respond with a JSON blob. For example:
+
+```json
+{"short-url":"https://localhost:3000/yuzahnt5"}
+```
+
+Visiting the generated URL in your browser will redirect you to the specified
+redirect URL. After the configured expiry duration passes (5 minutes at the
+time of writing), short URLs are no longer accessible and are removed from the
+in-memory data store.
--- a/cmd/eokvin/http.go
+++ b/cmd/eokvin/http.go
@ -0,0 +1,160 @@
+package main
+
+import (
+	"crypto/sha256"
+	"crypto/subtle"
+	"crypto/tls"
+	"encoding/json"
+	"fmt"
+	"golang.org/x/crypto/acme/autocert"
+	"log"
+	"net/http"
+	"strings"
+)
+
+func listenAndServe() error {
+	l := fmt.Sprintf("%s:%d", listenHost, listenPortHTTP)
+	srv := &http.Server{Addr: l, Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		redirectToCanonicalHost(w, r)
+		return
+	})}
+	return srv.ListenAndServe()
+}
+
+func listenAndServeTLS() error {
+	l := fmt.Sprintf("%s:%d", listenHost, listenPortHTTPS)
+	srv := &http.Server{Addr: l, Handler: newServeMux()}
+	if tlsKeyFile == "" && tlsCertFile == "" {
+		hosts := append([]string{listenHost}, fmt.Sprintf("www.%s", listenHost))
+		m := autocert.Manager{
+			Prompt:     autocert.AcceptTOS,
+			HostPolicy: autocert.HostWhitelist(hosts...),
+			Cache:      autocert.DirCache("certs"),
+		}
+		srv.TLSConfig = &tls.Config{GetCertificate: m.GetCertificate}
+	}
+	return srv.ListenAndServeTLS(tlsCertFile, tlsKeyFile)
+}
+
+func newServeMux() *http.ServeMux {
+	mux := http.NewServeMux()
+	mux.Handle("/new",
+		ensureCanonicalHost(
+			acceptMethod("POST",
+				requireToken(newHandler))))
+
+	mux.Handle("/", ensureCanonicalHost(indexHandler))
+	return mux
+}
+
+// ensureCanonicalHost decorates a http.Handler, ensuring that the
+// request being served is on the canonical hostname.
+func ensureCanonicalHost(h http.Handler) http.Handler {
+	listenHostPort := fmt.Sprintf("%s:%d", listenHost, listenPortHTTPS)
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Host != listenHost && r.Host != listenHostPort {
+			log.Println(r.Host, "doesnt equal", listenHost, "or", listenPortHTTPS)
+			redirectToCanonicalHost(w, r)
+			return
+		}
+		h.ServeHTTP(w, r)
+	})
+}
+
+// acceptMethod decorates a http.Handler, ensuring that the given HTTP method
+// is used in the request.
+func acceptMethod(m string, h http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != m {
+			w.WriteHeader(http.StatusMethodNotAllowed)
+			return
+		}
+		h.ServeHTTP(w, r)
+	})
+}
+
+func verifyToken(s string) bool {
+	sv := fmt.Sprintf("%x", sha256.Sum256([]byte(s)))
+	return subtle.ConstantTimeCompare([]byte(sv), []byte(tokenSHA256)) == 1
+}
+
+// requireToken decorates a http.Handler, ensuring that the request has a valid
+// token identifier.
+func requireToken(h http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if !verifyToken(r.PostFormValue("token")) {
+			w.WriteHeader(http.StatusForbidden)
+			return
+		}
+		h.ServeHTTP(w, r)
+	})
+}
+
+// redirectToCanonicalHost responds with a redirect to the canonical host.
+func redirectToCanonicalHost(w http.ResponseWriter, r *http.Request) {
+	t := canonicalHost + r.URL.Path
+	http.Redirect(w, r, t, http.StatusMovedPermanently)
+	if _, err := fmt.Fprintf(w, `<a href="%s">Redirecting...</a>`, t); err != nil {
+		log.Println("error writing response:", err.Error())
+	}
+}
+
+// newHandler is an http.Handler that creates a new item in the urlStore store.
+var newHandler http.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	link := r.PostFormValue("url")
+	if len(link) == 0 {
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+	k, err := urlStore.newItemID()
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+	urlStore.mu.Lock()
+	urlStore.entries[k] = newItem(link)
+	urlStore.mu.Unlock()
+	b, err := json.Marshal(map[string]string{"short-url": canonicalHost + k.String()})
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		_, err = fmt.Fprintf(w, `{"error": "%s"}\n`, strings.Replace(err.Error(), `"`, `'`, -1))
+		if err != nil {
+			log.Println("error writing response:", err.Error())
+		}
+		return
+	}
+	w.WriteHeader(http.StatusCreated)
+	if _, err = fmt.Fprintln(w, string(b)); err != nil {
+		log.Println("error writing response:", err.Error())
+	}
+	return
+})
+
+// indexHandler is a catch-all http.Handler that attempts to lookup items in
+// the store based on request path.
+var indexHandler http.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	key := strings.TrimLeft(r.URL.Path, "/")
+	if len(key) == 0 {
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+	k := itemID(key)
+	urlStore.mu.RLock()
+	v, ok := urlStore.entries[k]
+	urlStore.mu.RUnlock()
+	if ok {
+		if urlStore.isExpired(v) {
+			// rely on the reaper function to actually delete items.
+			w.WriteHeader(http.StatusNotFound)
+			return
+		}
+		u := v.String()
+		http.Redirect(w, r, u, http.StatusMovedPermanently)
+		if _, err := fmt.Fprintf(w, `<a href="%s">Redirecting...</a>`, u); err != nil {
+			log.Println("error writing response:", err.Error())
+		}
+		return
+	}
+	w.WriteHeader(http.StatusNotFound)
+	return
+})
--- a/cmd/eokvin/main.go
+++ b/cmd/eokvin/main.go
@ -0,0 +1,89 @@
+package main
+
+import (
+	"crypto/sha256"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"time"
+)
+
+// Runtime configuration values.
+var listenHost string
+var listenPortHTTPS int
+var listenPortHTTP int
+var canonicalHost string
+var tokenSHA256 string
+
+var tlsKeyFile string
+var tlsCertFile string
+
+var rawToken string
+
+// urlTTL contains the time.Duration describing how long a short URL shall
+// remain accessible.
+const urlTTL = 10 * time.Minute
+// urlStore contains URL values that map to short, random string keys.
+var urlStore = &store{entries: make(map[itemID]item), ttl: urlTTL}
+
+func init() {
+	flag.StringVar(&listenHost, "host", "eok.vin", "Listen hostname")
+	flag.IntVar(&listenPortHTTPS, "port", 443, "HTTPS listen port")
+	flag.IntVar(&listenPortHTTP, "http-port", 80, "HTTP listen port")
+	flag.StringVar(&tlsKeyFile, "key-file", "", "TLS private key file, blank for autocert")
+	flag.StringVar(&tlsCertFile, "cert-file", "", "TLS certificate chain file, blank for autocert")
+	flag.StringVar(&tokenSHA256, "token", "", "SHA256 of the secret token, used to authenticate")
+	flag.StringVar(&rawToken, "hash-token", "", "If given, the sha256 of the given value will be printed")
+}
+
+func validate() {
+	flag.Parse()
+
+	if len(rawToken) > 0 {
+		fmt.Printf("%x\n", sha256.Sum256([]byte(rawToken)))
+		os.Exit(0)
+		return
+	}
+
+	if len(listenHost) == 0 {
+		log.Fatal("host cannot be blank")
+	}
+	if listenPortHTTPS <= 0 {
+		log.Fatal("port must be > 0")
+	}
+	if listenPortHTTP <= 0 {
+		log.Fatal("http-port must be > 0")
+	}
+	if len(tokenSHA256) != 64 {
+		log.Fatal("token must be a valid sha256 sum")
+	}
+
+	canonicalHost = fmt.Sprintf("https://%s:%d/", listenHost, listenPortHTTPS)
+}
+
+func main() {
+	validate()
+
+	// Launch the HTTP redirect server.
+	go func() {
+		if err := listenAndServe(); err != nil {
+			log.Println(err.Error())
+		}
+	}()
+	// Launch the HTTPS main server.
+	go func() {
+		if err := listenAndServeTLS(); err != nil {
+			log.Println(err.Error())
+		}
+	}()
+	// Launch the expired entry reaper.
+	go func() {
+		if err := urlStore.expiredItemReaper(); err != nil {
+			log.Println(err.Error())
+		}
+	}()
+	// Yield forever.
+	select {}
+}
+
--- a/cmd/eokvin/store.go
+++ b/cmd/eokvin/store.go
@ -0,0 +1,93 @@
+package main
+
+import (
+	"crypto/rand"
+	"errors"
+	"math/big"
+	"sync"
+	"time"
+)
+
+// randSet is the set of characters used when generating a random key.
+const randSet = "abcdefghijklmnopqrstuvwxyz1234567890"
+const randSetLen = int64(len(randSet))
+
+// An itemID is a unique key in a store.
+type itemID string
+func (c itemID) String() string {
+	return string(c)
+}
+
+// An item is a single item, stored in a store.
+type item struct {
+	value string
+	insertedAt time.Time
+}
+func (c item) String() string {
+	return c.value
+}
+
+// A store is an in-memory data store with expiring items.
+type store struct {
+	mu sync.RWMutex
+	entries map[itemID]item
+	ttl time.Duration
+}
+
+// newItemID creates a new store key, ensuring it is unique.
+func (cch *store) newItemID() (itemID, error) {
+	b := make([]byte, 8)
+	l := big.NewInt(randSetLen)
+	for i := 0; i < 8; i++ {
+		n, err := rand.Int(rand.Reader, l)
+		if err != nil {
+			return "", err
+		}
+		b[i] = randSet[int(n.Int64())]
+	}
+	k := itemID(b)
+	cch.mu.RLock()
+	defer cch.mu.RUnlock()
+	// Avoid overwriting existing entries
+	if _, ok := cch.entries[k]; ok {
+		return "", errors.New("cache: collision detected")
+	}
+	return k, nil
+}
+
+// isExpired returns true if the given item is expired.
+func (cch *store) isExpired(c item) bool {
+	return c.insertedAt.Before(time.Now().Add(-1 * cch.ttl))
+}
+
+// expiredItemReaper deletes expired entries from the store at regular
+// intervals.
+func (cch *store) expiredItemReaper() error {
+	for {
+		select {
+		case <-time.After(30 * time.Second):
+			var del []itemID
+			cch.mu.RLock()
+			for k, v := range cch.entries {
+				if cch.isExpired(v) {
+					del = append(del, k)
+				}
+			}
+			cch.mu.RUnlock()
+			if len(del) == 0 {
+				continue
+			}
+			cch.mu.Lock()
+			for _, k := range del {
+				delete(cch.entries, k)
+			}
+			cch.mu.Unlock()
+		}
+	}
+}
+
+// newItem initializes a new item.
+func newItem(s string) item {
+	return item{value: s, insertedAt: time.Now()}
+}
+