From 4e6adec81ab841c8f2ff042702b418ffbb4a569f Mon Sep 17 00:00:00 2001
From: Umar Getagazov <umar@handlerug.me>
Date: Mon, 14 Nov 2022 22:12:50 +0300
Subject: [PATCH] Validate the revision hash on /rev{,-text}/ pages

---
 history/histweb/histview.go | 11 +----------
 util/util.go                | 15 +++++++++++++++
 web/readers.go              | 33 ++++++++++++++++++---------------
 3 files changed, 34 insertions(+), 25 deletions(-)

diff --git a/history/histweb/histview.go b/history/histweb/histview.go
index 4467b44..4737817 100644
--- a/history/histweb/histview.go
+++ b/history/histweb/histview.go
@@ -3,7 +3,6 @@ package histweb
 
 import (
 	"embed"
-	"encoding/hex"
 	"fmt"
 	"github.com/bouncepaw/mycorrhiza/cfg"
 	"github.com/bouncepaw/mycorrhiza/files"
@@ -39,15 +38,7 @@ func handlerPrimitiveDiff(w http.ResponseWriter, rq *http.Request) {
 	util.PrepareRq(rq)
 	shorterURL := strings.TrimPrefix(rq.URL.Path, "/primitive-diff/")
 	revHash, slug, found := strings.Cut(shorterURL, "/")
-	if !found || len(revHash) < 7 || len(slug) < 1 {
-		http.Error(w, "403 bad request", http.StatusBadRequest)
-		return
-	}
-	paddedRevHash := revHash
-	if len(paddedRevHash)%2 != 0 {
-		paddedRevHash = paddedRevHash[:len(paddedRevHash)-1]
-	}
-	if _, err := hex.DecodeString(paddedRevHash); err != nil {
+	if !found || !util.IsRevHash(revHash) || len(slug) < 1 {
 		http.Error(w, "403 bad request", http.StatusBadRequest)
 		return
 	}
diff --git a/util/util.go b/util/util.go
index 98e37f8..a00230c 100644
--- a/util/util.go
+++ b/util/util.go
@@ -135,3 +135,18 @@ func (f FormData) Get(key string) string {
 func (f FormData) Put(key, value string) {
 	f.fields[key] = value
 }
+
+// IsRevHash checks if the revision hash is valid.
+func IsRevHash(revHash string) bool {
+	if len(revHash) < 7 {
+		return false
+	}
+	paddedRevHash := revHash
+	if len(paddedRevHash)%2 != 0 {
+		paddedRevHash = paddedRevHash[:len(paddedRevHash)-1]
+	}
+	if _, err := hex.DecodeString(paddedRevHash); err != nil {
+		return false
+	}
+	return true
+}
diff --git a/web/readers.go b/web/readers.go
index 2bc9a38..53f7576 100644
--- a/web/readers.go
+++ b/web/readers.go
@@ -59,12 +59,15 @@ func handlerMedia(w http.ResponseWriter, rq *http.Request) {
 // /rev-text/<revHash>/<hyphaName>
 func handlerRevisionText(w http.ResponseWriter, rq *http.Request) {
 	util.PrepareRq(rq)
+	shorterURL := strings.TrimPrefix(rq.URL.Path, "/rev-text/")
+	revHash, slug, found := strings.Cut(shorterURL, "/")
+	if !found || !util.IsRevHash(revHash) || len(slug) < 1 {
+		http.Error(w, "403 bad request", http.StatusBadRequest)
+		return
+	}
 	var (
-		shorterURL      = strings.TrimPrefix(rq.URL.Path, "/rev-text/")
-		firstSlashIndex = strings.IndexRune(shorterURL, '/')
-		revHash         = shorterURL[:firstSlashIndex]
-		hyphaName       = util.CanonicalName(shorterURL[firstSlashIndex+1:])
-		h               = hyphae.ByName(hyphaName)
+		hyphaName = util.CanonicalName(slug)
+		h         = hyphae.ByName(hyphaName)
 	)
 	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
 	switch h := h.(type) {
@@ -103,17 +106,17 @@ func handlerRevisionText(w http.ResponseWriter, rq *http.Request) {
 // handlerRevision displays a specific revision of the text part the hypha
 func handlerRevision(w http.ResponseWriter, rq *http.Request) {
 	util.PrepareRq(rq)
+	lc := l18n.FromRequest(rq)
+	shorterURL := strings.TrimPrefix(rq.URL.Path, "/rev/")
+	revHash, slug, found := strings.Cut(shorterURL, "/")
+	if !found || !util.IsRevHash(revHash) || len(slug) < 1 {
+		http.Error(w, "403 bad request", http.StatusBadRequest)
+		return
+	}
 	var (
-		lc              = l18n.FromRequest(rq)
-		shorterURL      = strings.TrimPrefix(rq.URL.Path, "/rev/")
-		firstSlashIndex = strings.IndexRune(shorterURL, '/')
-		revHash         = shorterURL[:firstSlashIndex]
-		hyphaName       = util.CanonicalName(shorterURL[firstSlashIndex+1:])
-		h               = hyphae.ByName(hyphaName)
-		contents        = fmt.Sprintf(`<p>%s</p>`, lc.Get("ui.revision_no_text"))
-	)
-
-	var (
+		hyphaName    = util.CanonicalName(slug)
+		h            = hyphae.ByName(hyphaName)
+		contents     = fmt.Sprintf(`<p>%s</p>`, lc.Get("ui.revision_no_text"))
 		textContents string
 		err          error
 		mycoFilePath string