commit 07de40033e5caac513e03fa8956eeed6cede38cb Author: David Fifield david@bamsoftware.com Date: Sun Nov 25 21:39:43 2012 -0800

WebSocket HTTP negotiation. --- websocket-transport/websocket-server.go | 125 +++++++++++++++++++++++++++++++ 1 files changed, 125 insertions(+), 0 deletions(-)

diff --git a/websocket-transport/websocket-server.go b/websocket-transport/websocket-server.go index d905364..c6effe4 100644 --- a/websocket-transport/websocket-server.go +++ b/websocket-transport/websocket-server.go @@ -1,11 +1,15 @@ package main

import ( + "bufio" + "crypto/sha1" + "encoding/base64" "fmt" "net" "net/http" "os" "os/signal" + "strings" )

const defaultPort = 9901 @@ -18,7 +22,128 @@ func logDebug(format string, v ...interface{}) { fmt.Fprintf(os.Stderr, format+"\n", v...) }

+func httpError(w http.ResponseWriter, bufrw *bufio.ReadWriter, code int) { + w.Header().Set("Connection", "close") + bufrw.WriteString(fmt.Sprintf("HTTP/1.0 %d %s\r\n", code, http.StatusText(code))) + w.Header().Write(bufrw) + bufrw.WriteString("\r\n") + bufrw.Flush() +} + +func commaSplit(s string) []string { + var result []string + if strings.TrimSpace(s) == "" { + return result + } + for _, e := range strings.Split(s, ",") { + result = append(result, strings.TrimSpace(e)) + } + return result +} + +func containsCase(haystack []string, needle string) bool { + for _, e := range haystack { + if strings.ToLower(e) == strings.ToLower(needle) { + return true + } + } + return false +} + +func sha1Hash(data string) []byte { + h := sha1.New() + h.Write([]byte(data)) + return h.Sum(nil) +} + func handler(w http.ResponseWriter, req *http.Request) { + conn, bufrw, err := w.(http.Hijacker).Hijack() + if err != nil { + http.Error(w, err.Error(), http.StatusInternalServerError) + return + } + defer conn.Close() + + // See RFC 6455 section 4.2.1 for this sequence of checks. + + // 1. An HTTP/1.1 or higher GET request, including a "Request-URI"... + if req.Method != "GET" { + httpError(w, bufrw, http.StatusMethodNotAllowed) + return + } + if req.URL.Path != "/" { + httpError(w, bufrw, http.StatusNotFound) + return + } + // 2. A |Host| header field containing the server's authority. + // We deliberately skip this test. + // 3. An |Upgrade| header field containing the value "websocket", + // treated as an ASCII case-insensitive value. + if !containsCase(commaSplit(req.Header.Get("Upgrade")), "websocket") { + httpError(w, bufrw, http.StatusBadRequest) + return + } + // 4. A |Connection| header field that includes the token "Upgrade", + // treated as an ASCII case-insensitive value. + if !containsCase(commaSplit(req.Header.Get("Connection")), "Upgrade") { + httpError(w, bufrw, http.StatusBadRequest) + return + } + // 5. A |Sec-WebSocket-Key| header field with a base64-encoded value + // that, when decoded, is 16 bytes in length. + websocketKey := req.Header.Get("Sec-WebSocket-Key") + key, err := base64.StdEncoding.DecodeString(websocketKey) + if err != nil || len(key) != 16 { + httpError(w, bufrw, http.StatusBadRequest) + return + } + // 6. A |Sec-WebSocket-Version| header field, with a value of 13. + // We also allow 8 from draft-ietf-hybi-thewebsocketprotocol-10. + var knownVersions = []string{"8", "13"} + websocketVersion := req.Header.Get("Sec-WebSocket-Version") + if !containsCase(knownVersions, websocketVersion) { + // "If this version does not match a version understood by the + // server, the server MUST abort the WebSocket handshake + // described in this section and instead send an appropriate + // HTTP error code (such as 426 Upgrade Required) and a + // |Sec-WebSocket-Version| header field indicating the + // version(s) the server is capable of understanding." + w.Header().Set("Sec-WebSocket-Version", strings.Join(knownVersions, ", ")) + httpError(w, bufrw, 426) + return + } + // 7. Optionally, an |Origin| header field. + // 8. Optionally, a |Sec-WebSocket-Protocol| header field, with a list of + // values indicating which protocols the client would like to speak, ordered + // by preference. + _ = commaSplit(req.Header.Get("Sec-WebSocket-Protocol")) + // 9. Optionally, a |Sec-WebSocket-Extensions| header field... + // 10. Optionally, other header fields... + + // See RFC 6455 section 4.2.2, item 5 for these steps. + + // 1. A Status-Line with a 101 response code as per RFC 2616. + bufrw.WriteString(fmt.Sprintf("HTTP/1.0 %d %s\r\n", http.StatusSwitchingProtocols, http.StatusText(http.StatusSwitchingProtocols))) + // 2. An |Upgrade| header field with value "websocket" as per RFC 2616. + w.Header().Set("Upgrade", "websocket") + // 3. A |Connection| header field with value "Upgrade". + w.Header().Set("Connection", "Upgrade") + // 4. A |Sec-WebSocket-Accept| header field. The value of this header + // field is constructed by concatenating /key/, defined above in step 4 + // in Section 4.2.2, with the string + // "258EAFA5-E914-47DA-95CA-C5AB0DC85B11", taking the SHA-1 hash of this + // concatenated value to obtain a 20-byte value and base64-encoding (see + // Section 4 of [RFC4648]) this 20-byte hash. + const magicGUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11" + acceptKey := base64.StdEncoding.EncodeToString(sha1Hash(websocketKey + magicGUID)) + w.Header().Set("Sec-WebSocket-Accept", acceptKey) + // 5. Optionally, a |Sec-WebSocket-Protocol| header field, with a value + // /subprotocol/ as defined in step 4 in Section 4.2.2. + // w.Header().Set("Sec-WebSocket-Protocol", "base64") + // 6. Optionally, a |Sec-WebSocket-Extensions| header field... + w.Header().Write(bufrw) + bufrw.WriteString("\r\n") + bufrw.Flush() }

func startListener(addr *net.TCPAddr) (*net.TCPListener, error) {