OrbitalBeat/OrbitalBeat.go

package main

import (
	"bytes"
	"crypto/ecdsa"
	"crypto/ed25519"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/tls"
	"crypto/x509"
	"crypto/x509/pkix"
	"database/sql"
	"encoding/base32"
	"encoding/binary"
	"encoding/hex"
	"encoding/pem"
	"flag"
	"fmt"
	"github.com/ipfs/go-cid"
	_ "github.com/lib/pq"
	"github.com/multiformats/go-multihash"
	"log"
	"math/big"
	"net/http"
	"net/url"
	"os"
	"path"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"
	"time"
	"unicode"
)

type ContentCacheEntry struct {
	Entry      ContentEntry
	File       *os.File
	RefCount   int64
	AccessTime time.Time
}

func (e *ContentCacheEntry) valid() bool {
	return atomic.LoadInt64(&e.RefCount) > 0
}

func (e *ContentCacheEntry) borrow() *ContentCacheEntry {
	if e.valid() {
		if atomic.AddInt64(&e.RefCount, 1) > 1 {
			return e
		} else { //Has already been deallocated or is in the process
			atomic.AddInt64(&e.RefCount, -1)
		}
	}
	return nil
}

func (e *ContentCacheEntry) release() {
	objectCacheMutex.Lock()
	if atomic.AddInt64(&e.RefCount, -1) == 0 {
		defer e.File.Close()
		delete(objectCache, e.Entry.Identifier)
	}
	objectCacheMutex.Unlock()
}

var base32Encoding = base32.NewEncoding("qpzry9x8gf2tvdw0s3jn54khce6mua7l").WithPadding(base32.NoPadding)

var dbHandle *sql.DB
var sniAddress string
var sha256Statement *sql.Stmt
var md5Statement *sql.Stmt
var fdlimit int

var objectCacheMutex sync.RWMutex
var objectCache = make(map[cid.Cid]*ContentCacheEntry)

var messageCacheLimit int
var messageCacheMutex sync.RWMutex
var messageCache = make(map[string]*ContentMessage)

var trustedPublicKeys []ed25519.PublicKey

func isSNIAllowed(sni string) bool {
	return len(sniAddress) == 0 || sni == sniAddress
}

func getFirstValidContentEntry(entries *[]ContentEntry) *ContentEntry {
	for _, entry := range *entries {
		stat, err := os.Stat(entry.Path)
		if err == nil /*&& uint64(stat.Size()) == entry.Size*/ { //TODO: update Size if not found
			copiedEntry := entry
			copiedEntry.Size = uint64(stat.Size())
			return &copiedEntry
		}
	}

	return nil
}

func handleQueryRequest(w http.ResponseWriter, r *http.Request, identifier cid.Cid, extraArguments []string) {

	var cacheEntry = tryGetCacheEntryForIdentifier(identifier)

	if cacheEntry == nil {
		result := getEntriesForCID(identifier)

		entry := getFirstValidContentEntry(&result)

		if entry != nil {
			cacheEntry = getCacheEntryForContentEntry(entry)
		}
	}

	if cacheEntry == nil {
		var origin string

		if r.Header.Get("Referer") != "" {
			origin = r.Header.Get("Referer")
		} else if r.Header.Get("Origin") != "" {
			origin = r.Header.Get("Origin")
		}

		//Try to redirect back to origin
		if len(extraArguments) > 0 && origin != "" {
			mh, _ := multihash.Decode(identifier.Hash())
			var kind string
			if mh.Code == multihash.SHA2_256 {
				kind = "sha256"
			} else if mh.Code == multihash.MD5 {
				kind = "md5"
			}
			if kind != "" {
				http.Redirect(w, r, fmt.Sprintf("%s/%s/%s/%s", origin, kind, hex.EncodeToString(mh.Digest), strings.Join(extraArguments, "/")), http.StatusFound)
				return
			}
		}
		w.WriteHeader(http.StatusNotFound)
		return
	}
	defer cacheEntry.release()

	w.Header().Set("Accept-Ranges", "bytes")
	w.Header().Set("ETag", cacheEntry.Entry.Identifier.String())
	w.Header().Set("Content-Length", strconv.FormatUint(cacheEntry.Entry.Size, 10))
	w.Header().Set("Cache-Control", "public, max-age=2592000, immutable")

	filename := path.Base(cacheEntry.Entry.Path)

	//TODO: setting to hide filename
	w.Header().Set("Content-Disposition", fmt.Sprintf("inline; filename*=utf-8''%s", url.PathEscape(filename)))

	http.ServeContent(w, r, filename, time.Date(1970, 0, 0, 0, 0, 0, 0, time.UTC), cacheEntry.File)
}

func isASCII(s string) bool {
	for _, c := range s {
		if c > unicode.MaxASCII {
			return false
		}
	}
	return true
}

func setOtherHeaders(w http.ResponseWriter) {
	w.Header().Set("Server", "OrbitalBeat")
	w.Header().Set("Vary", "Content-Encoding")
	w.Header().Set("X-Content-Type-Options", "nosniff")
}
func setCORSHeaders(w http.ResponseWriter) {
	w.Header().Set("Access-Control-Allow-Credentials", "true")
	w.Header().Set("Access-Control-Max-Age", "7200") //Firefox caps this to 86400, Chrome to 7200. Default is 5 seconds (!!!)
	w.Header().Set("Access-Control-Allow-Methods", "GET,HEAD,OPTIONS")
	w.Header().Set("Access-Control-Allow-Headers", "DNT,ETag,Origin,Accept,Accept-Language,X-Requested-With,Range")
	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.Header().Set("Access-Control-Expose-Headers", "*")

	//CORP, COEP, COOP
	w.Header().Set("Cross-Origin-Embedder-Policy", "require-corp")
	w.Header().Set("Cross-Origin-Resource-Policy", "cross-origin")
	w.Header().Set("Cross-Origin-Opener-Policy", "unsafe-none")
}

func getCacheEntryForContentEntry(entry *ContentEntry) *ContentCacheEntry {

	cacheEntry := tryGetCacheEntryForIdentifier(entry.Identifier)

	if cacheEntry != nil {
		return cacheEntry
	}
	objectCacheMutex.Lock()
	defer objectCacheMutex.Unlock()

	if len(objectCache) >= fdlimit {
		//Find oldest value, remove it
		var item *ContentCacheEntry
		for _, e := range objectCache {
			if item == nil || e.AccessTime.Before(item.AccessTime) {
				item = e
			}
		}

		if item != nil {
			delete(objectCache, item.Entry.Identifier)
			item.release()
		}
	}

	f, err := os.Open(entry.Path)
	if err != nil {
		return nil
	}

	objectCache[entry.Identifier] = &ContentCacheEntry{
		Entry:      *entry,
		File:       f,
		RefCount:   1,
		AccessTime: time.Now(),
	}

	return objectCache[entry.Identifier].borrow()
}

func tryGetCacheEntryForIdentifier(identifier cid.Cid) *ContentCacheEntry {

	objectCacheMutex.RLock()
	defer objectCacheMutex.RUnlock()

	cacheEntry, ok := objectCache[identifier]
	if ok {
		cacheEntry := cacheEntry.borrow()
		cacheEntry.AccessTime = time.Now().UTC()
		return cacheEntry
	}

	return nil
}

func IsTrustedPublicKey(key ed25519.PublicKey) bool {
	for _, k := range trustedPublicKeys {
		if bytes.Compare(k, key) == 0 {
			return true
		}
	}
	return false
}

func handle(w http.ResponseWriter, r *http.Request) {
	if len(r.Host) > 0 && r.Host == r.TLS.ServerName { //Prevents rebinding / DNS stuff
		w.WriteHeader(http.StatusNotFound)
		return
	}

	if r.Method == "GET" || r.Method == "HEAD" {
		log.Printf("Serve %s", r.URL.Path)
		setOtherHeaders(w)
		setCORSHeaders(w)
		pathElements := strings.Split(r.URL.Path, "/")
		if len(pathElements) < 2 {
			w.WriteHeader(http.StatusBadRequest)
			return
		}

		messageBytes, err := base32Encoding.DecodeString(pathElements[1])
		if err != nil {
			w.WriteHeader(http.StatusBadRequest)
			return
		}
		message := DecodeContentMessage(messageBytes)
		if message == nil {
			w.WriteHeader(http.StatusBadRequest)
			return
		}

		if !IsTrustedPublicKey(message.PublicKey) {
			w.WriteHeader(http.StatusForbidden)
			return
		}

		if !message.verify() {
			w.WriteHeader(http.StatusForbidden)
			return
		}

		log.Printf("Valid %s %s", r.URL.Path, message.Identifier.String())

		handleQueryRequest(w, r, message.Identifier, pathElements[2:])
	} else if r.Method == "OPTIONS" {
		setOtherHeaders(w)
		setCORSHeaders(w)
		w.WriteHeader(http.StatusNoContent)
	} else {
		w.WriteHeader(http.StatusNotImplemented)
	}
}

//TODO: move this to a library
type ContentMessage struct {
	Version            uint64
	PublicKey          ed25519.PublicKey
	IssueTime          int64
	Identifier         cid.Cid
	VerificationResult *bool
	Signature          []byte
}

func (s *ContentMessage) sign(privateKey ed25519.PrivateKey) {
	s.PublicKey = make([]byte, ed25519.PublicKeySize)
	copy(s.PublicKey, privateKey[32:])
	s.Signature = ed25519.Sign(privateKey, s.encodeMessage())
	s.VerificationResult = nil
}

func (s *ContentMessage) verify() bool {
	currentTime := time.Now()

	notBefore := currentTime.Add(-time.Hour)    //Only one hour before time
	notAfter := currentTime.Add(time.Hour * 24) //Only 24 hours after time
	issueTime := time.Unix(s.IssueTime, 0)

	if issueTime.Before(notBefore) {
		return false
	}

	if issueTime.After(notAfter) {
		return false
	}

	messageCacheMutex.RLock()
	k := string(s.encode())
	cachedMessage, ok := messageCache[k]
	messageCacheMutex.RUnlock()
	if ok {
		return *cachedMessage.VerificationResult
	}

	messageCacheMutex.Lock()
	defer messageCacheMutex.Unlock()

	if s.VerificationResult == nil {
		makeBool := func(v bool) *bool { return &v }
		s.VerificationResult = makeBool(ed25519.Verify(s.PublicKey, s.encodeMessage(), s.Signature))
	}

	if len(messageCache) >= messageCacheLimit {
		//Find oldest value, remove it
		var item *ContentMessage
		for _, e := range messageCache {
			if item == nil || e.IssueTime < item.IssueTime {
				item = e
			}
		}

		if item != nil {
			delete(messageCache, string(item.encode()))
		}
	}

	messageCache[k] = s

	return *s.VerificationResult
}

func (s *ContentMessage) encodeMessage() []byte {
	message := &bytes.Buffer{}

	buf := make([]byte, binary.MaxVarintLen64)

	n := binary.PutUvarint(buf, s.Version) //signature version
	_, _ = message.Write(buf[:n])

	if s.Version == 0 {
		_, _ = message.Write(s.PublicKey)
		n = binary.PutVarint(buf, s.IssueTime) //time
		_, _ = message.Write(buf[:n])

		_, _ = s.Identifier.WriteBytes(message)

		return message.Bytes()
	}

	return nil
}

func (s *ContentMessage) encode() []byte {
	message := s.encodeMessage()

	if message == nil || len(s.Signature) != ed25519.SignatureSize {
		return nil
	}

	return append(message, s.Signature...)
}

func (s ContentMessage) String() string {
	return fmt.Sprintf("%d %x %d %s %x", s.Version, s.PublicKey, s.IssueTime, s.Identifier.String(), s.Signature)
}

func DecodeContentMessage(signatureBytes []byte) *ContentMessage {
	message := ContentMessage{}

	buffer := bytes.NewBuffer(signatureBytes)

	var err error

	message.Version, err = binary.ReadUvarint(buffer)
	if err != nil {
		log.Print(err)
		return nil
	}

	if message.Version == 0 {
		message.PublicKey = make([]byte, ed25519.PublicKeySize)
		_, err := buffer.Read(message.PublicKey)
		if err != nil {
			log.Print(message.String())
			log.Print(err)
			return nil
		}
		message.IssueTime, err = binary.ReadVarint(buffer)
		if err != nil {
			log.Print(message.String())
			log.Print(err)
			return nil
		}

		_, message.Identifier, err = cid.CidFromReader(buffer)
		if err != nil {
			log.Print(message.String())
			log.Print(err)
			return nil
		}

		message.Signature = make([]byte, ed25519.SignatureSize)
		_, err = buffer.Read(message.Signature)
		if err != nil {
			log.Print(message.String())
			log.Print(err)
			return nil
		}

		if buffer.Len() != 0 { //Unknown extra data
			log.Print(message.String())
			log.Printf("%x", buffer.Bytes())
			return nil
		}

		return &message

	}

	return nil
}

type ContentEntry struct {
	Identifier cid.Cid
	Path       string
	Size       uint64
}

func handleQuery(rows *sql.Rows, err error) []ContentEntry {
	if err != nil {
		log.Print(err)
		return []ContentEntry{}
	}
	defer rows.Close()

	var result []ContentEntry

	for rows.Next() {
		var entry ContentEntry
		var sha256 multihash.Multihash
		var size sql.NullInt64
		err := rows.Scan(&entry.Path, &size, &sha256)
		if err != nil {
			log.Print(err)
			break
		}
		if size.Valid {
			entry.Size = uint64(size.Int64)
		}
		mh, _ := multihash.Encode(sha256, multihash.SHA2_256)
		entry.Identifier = cid.NewCidV1(cid.Raw, mh)

		result = append(result, entry)
	}

	return result
}

func getEntriesForCID(identifier cid.Cid) []ContentEntry {

	mh, _ := multihash.Decode(identifier.Hash())
	if mh.Code == multihash.SHA2_256 {
		return handleQuery(sha256Statement.Query(mh.Digest))
	} else if mh.Code == multihash.MD5 {
		return handleQuery(md5Statement.Query(mh.Digest))
	}

	return []ContentEntry{}
}

func createSelfSignedCertificate() ([]byte, []byte) {
	x509Template := x509.Certificate{
		SerialNumber:          big.NewInt(1),
		Subject:               pkix.Name{},
		NotBefore:             time.Unix(0, 0).UTC(),
		NotAfter:              time.Date(time.Now().UTC().Year()+10, 0, 0, 0, 0, 0, 0, time.UTC),
		KeyUsage:              x509.KeyUsageCertSign | x509.KeyUsageCRLSign,
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
		BasicConstraintsValid: true,
		IsCA:                  true,
		MaxPathLen:            1,
	}

	privateBogusKey, err := ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
	if err != nil {
		log.Fatal(err)
	}

	certBytes, err := x509.CreateCertificate(rand.Reader, &x509Template, &x509Template, privateBogusKey.Public(), privateBogusKey)
	if err != nil {
		log.Fatal(err)
	}

	keyBytes, err := x509.MarshalPKCS8PrivateKey(privateBogusKey)
	if err != nil {
		log.Fatal(err)
	}

	return pem.EncodeToMemory(&pem.Block{
			Type:  "CERTIFICATE",
			Bytes: certBytes,
		}),
		pem.EncodeToMemory(&pem.Block{
			Type:  "PRIVATE KEY",
			Bytes: keyBytes,
		})
}

func main() {
	//TODO: OCSP
	certificatePath := flag.String("certificate", "ssl.crt", "Path to SSL certificate file.")
	keypairPath := flag.String("keypair", "ssl.key", "Path to SSL key file.")

	pgConnStr := flag.String("connstr", "", "Postgres connection string for postgres database")

	listenAddress := flag.String("listen", ":7777", "Path to SSL key file.")

	trustedKeys := flag.String("trusted_keys", "", "Trusted list of public keys, comma separated.")

	sniAddressOption := flag.String("sni", "", "Define SNI address if desired. Empty will serve any requests regardless.")

	fdLimitOption := flag.Int("fdlimit", 128, "Maximum number of lingering cached open files.")

	signatureCacheLimitOption := flag.Int("siglimit", 4096, "Maximum number of lingering valid signature cache results.")

	flag.Parse()

	fdlimit = *fdLimitOption
	messageCacheLimit = *signatureCacheLimitOption

	var err error

	for _, k := range strings.Split(*trustedKeys, ",") {
		var publicKey ed25519.PublicKey
		publicKey, err = base32Encoding.DecodeString(strings.Trim(k, " "))
		if err != nil {
			log.Fatal(err)
		}

		if len(publicKey) != ed25519.PublicKeySize {
			continue
		}
		trustedPublicKeys = append(trustedPublicKeys, publicKey)
		log.Printf("Added public key %x", publicKey)
	}

	dbHandle, err = sql.Open("postgres", *pgConnStr)
	if err != nil {
		log.Fatal(err)
	}

	defer dbHandle.Close()

	sha256Statement, err = dbHandle.Prepare("SELECT path, size, sha256 FROM entries WHERE sha256 = $1;")
	if err != nil {
		log.Fatal(err)
	}
	defer sha256Statement.Close()

	md5Statement, err = dbHandle.Prepare("SELECT path, size, sha256 FROM entries WHERE md5 = $1;")
	if err != nil {
		log.Fatal(err)
	}
	defer md5Statement.Close()

	//TODO: create postgres tables

	sniAddress = strings.ToLower(*sniAddressOption)

	bogusCertificatePEM, bogusKeyPairPEM := createSelfSignedCertificate()

	bogusCertificate, err := tls.X509KeyPair(bogusCertificatePEM, bogusKeyPairPEM)
	if err != nil {
		log.Fatal(err)
	}
	serverCertificate, err := tls.LoadX509KeyPair(*certificatePath, *keypairPath)
	if err != nil {
		log.Fatal(err)
	}

	server := &http.Server{
		Addr:    *listenAddress,
		Handler: http.HandlerFunc(handle),
		TLSConfig: &tls.Config{
			MinVersion: tls.VersionTLS12,
			MaxVersion: 0, //max supported, currently TLS 1.3
			CurvePreferences: []tls.CurveID{
				tls.X25519,
				tls.CurveP256,
				tls.CurveP384,
			},
			CipherSuites: []uint16{
				tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256,
				tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
				tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
			},
			PreferServerCipherSuites: false,
			SessionTicketsDisabled:   false,
			Renegotiation:            tls.RenegotiateFreelyAsClient,
			NextProtos: []string{
				"h2",
				"http/1.1",
			},
			GetCertificate: func(info *tls.ClientHelloInfo) (*tls.Certificate, error) {
				if isSNIAllowed(info.ServerName) {
					return &serverCertificate, nil
				}
				return &bogusCertificate, nil
			},
		},
	}

	log.Printf("Serving on %s", *listenAddress)

	log.Fatal(server.ListenAndServeTLS(*certificatePath, *keypairPath))
}