From 09af83576a877eda40512bfba30b47a1b13061fb Mon Sep 17 00:00:00 2001
From: Rutger Broekhoff
Date: Wed, 13 Nov 2024 20:47:40 +0100
Subject: Initial (public) commit

---
 icalproxy.go | 117 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 117 insertions(+)
 create mode 100644 icalproxy.go

(limited to 'icalproxy.go')

diff --git a/icalproxy.go b/icalproxy.go
new file mode 100644
index 0000000..cf09e5d
--- /dev/null
+++ b/icalproxy.go
@@ -0,0 +1,117 @@
+package main
+
+import (
+	"bytes"
+	"log"
+	"net/http"
+	"net/url"
+	"time"
+
+	"github.com/emersion/go-ical"
+	"golang.org/x/crypto/argon2"
+)
+
+func main() {
+	cfg := loadConfig()
+	printConfig(&cfg)
+
+	handler := handler{ignore: cfg.Ignore, tokens: cfg.UserTokens}
+
+	mux := http.ServeMux{}
+	mux.HandleFunc("/", handler.handle)
+	server := http.Server{
+		Addr:              ":" + cfg.Port,
+		Handler:           &mux,
+		ReadTimeout:       5 * time.Second,
+		WriteTimeout:      30 * time.Second,
+		IdleTimeout:       30 * time.Second,
+		ReadHeaderTimeout: 2 * time.Second,
+	}
+
+	log.Println("Listening on", cfg.Port)
+	log.Fatal(server.ListenAndServe())
+}
+
+type handler struct {
+	ignore ignoreRules
+	tokens map[string]userToken
+	calURL url.URL
+}
+
+func (h handler) makeTokenURL(token string) string {
+	newURL := h.calURL
+	query := newURL.Query()
+	query.Set("token", token)
+	newURL.RawQuery = query.Encode()
+	return newURL.String()
+}
+
+func (h handler) handle(w http.ResponseWriter, r *http.Request) {
+	brightspaceToken := r.URL.Query().Get("brightspace_token")
+	proxyUserID := r.URL.Query().Get("proxy_user_id")
+	proxyToken := r.URL.Query().Get("proxy_token")
+	if !userOK(h.tokens, proxyUserID, []byte(proxyToken)) {
+		http.Error(w, "Bad proxy_user_id or proxy_token", http.StatusUnauthorized)
+		return
+	}
+
+	resp, err := http.Get(h.makeTokenURL(brightspaceToken))
+	if err != nil {
+		http.Error(w, "Error sending request to Brightspace", http.StatusInternalServerError)
+		return
+	}
+
+	cal, err := ical.NewDecoder(resp.Body).Decode()
+	if err != nil {
+		http.Error(w, "Could not decode iCal", http.StatusInternalServerError)
+		return
+	}
+
+	filter(h.ignore, cal.Component)
+
+	if err = ical.NewEncoder(w).Encode(cal); err != nil {
+		log.Println("Error writing calendar:", err)
+	}
+}
+
+func filter(ignore ignoreRules, c *ical.Component) {
+	j := 0
+	for _, child := range c.Children {
+		keep := true
+
+		if child.Name == ical.CompEvent {
+			if location := child.Props.Get(ical.PropLocation); location != nil {
+				for _, locationRule := range ignore.LocationRegexes {
+					if locationRule.MatchString(location.Value) {
+						keep = false
+					}
+				}
+			}
+			if summary := child.Props.Get(ical.PropSummary); summary != nil {
+				for _, summaryRule := range ignore.SummaryRegexes {
+					if summaryRule.MatchString(summary.Value) {
+						keep = false
+					}
+				}
+			}
+		}
+
+		if keep {
+			c.Children[j] = child
+			j++
+		}
+	}
+	c.Children = c.Children[:j]
+}
+
+func userOK(tokens map[string]userToken, id string, token []byte) bool {
+	info, ok := tokens[id]
+	if !ok {
+		return false
+	}
+	return bytes.Compare(hash(token, info.Salt), info.Hash) == 0
+}
+
+func hash(token []byte, salt []byte) []byte {
+	return argon2.IDKey(token, salt, 1, 64*1024, 4, 32)
+}
-- 
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