Use raw Wiki links for non-renderable Wiki files (#30273)

In Wiki pages, short-links created to local Wiki files were always
expanded as regular Wiki Links. In particular, if a link wanted to point
to a file that Gitea doesn't know how to render (e.g, a .zip file), a
user following the link would be silently redirected to the Wiki's home
page.

This change makes short-links* in Wiki pages be expanded to raw wiki
links, so these local wiki files may be accessed without manually
accessing their URL.

* only short-links ending in a file extension that isn't renderable are
affected.

Closes #27121.

Signed-off-by: Rafael Girão <rafael.s.girao@tecnico.ulisboa.pt>
Co-authored-by: silverwind <me@silverwind.io>

4 files changed, 55 insertions, 16 deletions

diff --git a/modules/markup/html.go b/modules/markup/html.go
index 56aa1cb49c..cef643bf18 100644
--- a/modules/markup/html.go
+++ b/modules/markup/html.go
@@ -709,7 +709,8 @@ func shortLinkProcessor(ctx *RenderContext, node *html.Node) {
 
 		name += tail
 		image := false
-		switch ext := filepath.Ext(link); ext {
+		ext := filepath.Ext(link)
+		switch ext {
 		// fast path: empty string, ignore
 		case "":
 			// leave image as false
@@ -767,11 +768,26 @@ func shortLinkProcessor(ctx *RenderContext, node *html.Node) {
 			}
 		} else {
 			if !absoluteLink {
+				var base string
 				if ctx.IsWiki {
-					link = util.URLJoin(ctx.Links.WikiLink(), link)
+					switch ext {
+					case "":
+						// no file extension, create a regular wiki link
+						base = ctx.Links.WikiLink()
+					default:
+						// we have a file extension:
+						// return a regular wiki link if it's a renderable file (extension),
+						// raw link otherwise
+						if Type(link) != "" {
+							base = ctx.Links.WikiLink()
+						} else {
+							base = ctx.Links.WikiRawLink()
+						}
+					}
 				} else {
-					link = util.URLJoin(ctx.Links.SrcLink(), link)
+					base = ctx.Links.SrcLink()
 				}
+				link = util.URLJoin(base, link)
 			}
 			childNode.Type = html.TextNode
 			childNode.Data = name
diff --git a/modules/markup/html_test.go b/modules/markup/html_test.go
index 55de65d196..916e74fb62 100644
--- a/modules/markup/html_test.go
+++ b/modules/markup/html_test.go
@@ -427,6 +427,10 @@ func TestRender_ShortLinks(t *testing.T) {
 	otherImgurlWiki := util.URLJoin(markup.TestRepoURL, "wiki", "raw", "Link+Other.jpg")
 	encodedImgurlWiki := util.URLJoin(markup.TestRepoURL, "wiki", "raw", "Link+%23.jpg")
 	notencodedImgurlWiki := util.URLJoin(markup.TestRepoURL, "wiki", "raw", "some", "path", "Link+#.jpg")
+	renderableFileURL := util.URLJoin(tree, "markdown_file.md")
+	renderableFileURLWiki := util.URLJoin(markup.TestRepoURL, "wiki", "markdown_file.md")
+	unrenderableFileURL := util.URLJoin(tree, "file.zip")
+	unrenderableFileURLWiki := util.URLJoin(markup.TestRepoURL, "wiki", "raw", "file.zip")
 	favicon := "http://google.com/favicon.ico"
 
 	test(
@@ -482,6 +486,14 @@ func TestRender_ShortLinks(t *testing.T) {
 		`<p><a href="`+url+`" rel="nofollow">Link</a> <a href="`+otherURL+`" rel="nofollow">Other Link</a> <a href="`+encodedURL+`" rel="nofollow">Link?</a></p>`,
 		`<p><a href="`+urlWiki+`" rel="nofollow">Link</a> <a href="`+otherURLWiki+`" rel="nofollow">Other Link</a> <a href="`+encodedURLWiki+`" rel="nofollow">Link?</a></p>`)
 	test(
+		"[[markdown_file.md]]",
+		`<p><a href="`+renderableFileURL+`" rel="nofollow">markdown_file.md</a></p>`,
+		`<p><a href="`+renderableFileURLWiki+`" rel="nofollow">markdown_file.md</a></p>`)
+	test(
+		"[[file.zip]]",
+		`<p><a href="`+unrenderableFileURL+`" rel="nofollow">file.zip</a></p>`,
+		`<p><a href="`+unrenderableFileURLWiki+`" rel="nofollow">file.zip</a></p>`)
+	test(
 		"[[Link #.jpg]]",
 		`<p><a href="`+encodedImgurl+`" rel="nofollow"><img src="`+encodedImgurl+`" title="Link #.jpg" alt="Link #.jpg"/></a></p>`,
 		`<p><a href="`+encodedImgurlWiki+`" rel="nofollow"><img src="`+encodedImgurlWiki+`" title="Link #.jpg" alt="Link #.jpg"/></a></p>`)
diff --git a/modules/markup/markdown/markdown_test.go b/modules/markup/markdown/markdown_test.go
index a9c9024982..d9b67e43af 100644
--- a/modules/markup/markdown/markdown_test.go
+++ b/modules/markup/markdown/markdown_test.go
@@ -653,9 +653,9 @@ space</p>
 			Expected: `<p>space @mention-user<br/>
 /just/a/path.bin<br/>
 <a href="https://example.com/file.bin" rel="nofollow">https://example.com/file.bin</a><br/>
-<a href="/wiki/file.bin" rel="nofollow">local link</a><br/>
+<a href="/wiki/raw/file.bin" rel="nofollow">local link</a><br/>
 <a href="https://example.com" rel="nofollow">remote link</a><br/>
-<a href="/wiki/file.bin" rel="nofollow">local link</a><br/>
+<a href="/wiki/raw/file.bin" rel="nofollow">local link</a><br/>
 <a href="https://example.com" rel="nofollow">remote link</a><br/>
 <a href="/wiki/raw/image.jpg" target="_blank" rel="nofollow noopener"><img src="/wiki/raw/image.jpg" alt="local image"/></a><br/>
 <a href="/wiki/raw/path/file" target="_blank" rel="nofollow noopener"><img src="/wiki/raw/path/file" alt="local image"/></a><br/>
@@ -711,9 +711,9 @@ space</p>
 			Expected: `<p>space @mention-user<br/>
 /just/a/path.bin<br/>
 <a href="https://example.com/file.bin" rel="nofollow">https://example.com/file.bin</a><br/>
-<a href="https://gitea.io/wiki/file.bin" rel="nofollow">local link</a><br/>
+<a href="https://gitea.io/wiki/raw/file.bin" rel="nofollow">local link</a><br/>
 <a href="https://example.com" rel="nofollow">remote link</a><br/>
-<a href="https://gitea.io/wiki/file.bin" rel="nofollow">local link</a><br/>
+<a href="https://gitea.io/wiki/raw/file.bin" rel="nofollow">local link</a><br/>
 <a href="https://example.com" rel="nofollow">remote link</a><br/>
 <a href="https://gitea.io/wiki/raw/image.jpg" target="_blank" rel="nofollow noopener"><img src="https://gitea.io/wiki/raw/image.jpg" alt="local image"/></a><br/>
 <a href="https://gitea.io/wiki/raw/path/file" target="_blank" rel="nofollow noopener"><img src="https://gitea.io/wiki/raw/path/file" alt="local image"/></a><br/>
@@ -769,9 +769,9 @@ space</p>
 			Expected: `<p>space @mention-user<br/>
 /just/a/path.bin<br/>
 <a href="https://example.com/file.bin" rel="nofollow">https://example.com/file.bin</a><br/>
-<a href="/relative/path/wiki/file.bin" rel="nofollow">local link</a><br/>
+<a href="/relative/path/wiki/raw/file.bin" rel="nofollow">local link</a><br/>
 <a href="https://example.com" rel="nofollow">remote link</a><br/>
-<a href="/relative/path/wiki/file.bin" rel="nofollow">local link</a><br/>
+<a href="/relative/path/wiki/raw/file.bin" rel="nofollow">local link</a><br/>
 <a href="https://example.com" rel="nofollow">remote link</a><br/>
 <a href="/relative/path/wiki/raw/image.jpg" target="_blank" rel="nofollow noopener"><img src="/relative/path/wiki/raw/image.jpg" alt="local image"/></a><br/>
 <a href="/relative/path/wiki/raw/path/file" target="_blank" rel="nofollow noopener"><img src="/relative/path/wiki/raw/path/file" alt="local image"/></a><br/>
@@ -829,9 +829,9 @@ space</p>
 			Expected: `<p>space @mention-user<br/>
 /just/a/path.bin<br/>
 <a href="https://example.com/file.bin" rel="nofollow">https://example.com/file.bin</a><br/>
-<a href="/relative/path/wiki/file.bin" rel="nofollow">local link</a><br/>
+<a href="/relative/path/wiki/raw/file.bin" rel="nofollow">local link</a><br/>
 <a href="https://example.com" rel="nofollow">remote link</a><br/>
-<a href="/relative/path/wiki/file.bin" rel="nofollow">local link</a><br/>
+<a href="/relative/path/wiki/raw/file.bin" rel="nofollow">local link</a><br/>
 <a href="https://example.com" rel="nofollow">remote link</a><br/>
 <a href="/relative/path/wiki/raw/image.jpg" target="_blank" rel="nofollow noopener"><img src="/relative/path/wiki/raw/image.jpg" alt="local image"/></a><br/>
 <a href="/relative/path/wiki/raw/path/file" target="_blank" rel="nofollow noopener"><img src="/relative/path/wiki/raw/path/file" alt="local image"/></a><br/>
@@ -889,9 +889,9 @@ space</p>
 			Expected: `<p>space @mention-user<br/>
 /just/a/path.bin<br/>
 <a href="https://example.com/file.bin" rel="nofollow">https://example.com/file.bin</a><br/>
-<a href="/relative/path/wiki/file.bin" rel="nofollow">local link</a><br/>
+<a href="/relative/path/wiki/raw/file.bin" rel="nofollow">local link</a><br/>
 <a href="https://example.com" rel="nofollow">remote link</a><br/>
-<a href="/relative/path/wiki/file.bin" rel="nofollow">local link</a><br/>
+<a href="/relative/path/wiki/raw/file.bin" rel="nofollow">local link</a><br/>
 <a href="https://example.com" rel="nofollow">remote link</a><br/>
 <a href="/relative/path/wiki/raw/image.jpg" target="_blank" rel="nofollow noopener"><img src="/relative/path/wiki/raw/image.jpg" alt="local image"/></a><br/>
 <a href="/relative/path/wiki/raw/path/file" target="_blank" rel="nofollow noopener"><img src="/relative/path/wiki/raw/path/file" alt="local image"/></a><br/>
@@ -951,9 +951,9 @@ space</p>
 			Expected: `<p>space @mention-user<br/>
 /just/a/path.bin<br/>
 <a href="https://example.com/file.bin" rel="nofollow">https://example.com/file.bin</a><br/>
-<a href="/relative/path/wiki/file.bin" rel="nofollow">local link</a><br/>
+<a href="/relative/path/wiki/raw/file.bin" rel="nofollow">local link</a><br/>
 <a href="https://example.com" rel="nofollow">remote link</a><br/>
-<a href="/relative/path/wiki/file.bin" rel="nofollow">local link</a><br/>
+<a href="/relative/path/wiki/raw/file.bin" rel="nofollow">local link</a><br/>
 <a href="https://example.com" rel="nofollow">remote link</a><br/>
 <a href="/relative/path/wiki/raw/image.jpg" target="_blank" rel="nofollow noopener"><img src="/relative/path/wiki/raw/image.jpg" alt="local image"/></a><br/>
 <a href="/relative/path/wiki/raw/path/file" target="_blank" rel="nofollow noopener"><img src="/relative/path/wiki/raw/path/file" alt="local image"/></a><br/>
diff --git a/modules/markup/markdown/transform_link.go b/modules/markup/markdown/transform_link.go
index 8bf19ea4ce..7e305b74bc 100644
--- a/modules/markup/markdown/transform_link.go
+++ b/modules/markup/markdown/transform_link.go
@@ -4,6 +4,8 @@
 package markdown
 
 import (
+	"path/filepath"
+
 	"code.gitea.io/gitea/modules/markup"
 	giteautil "code.gitea.io/gitea/modules/util"
 
@@ -18,7 +20,16 @@ func (g *ASTTransformer) transformLink(ctx *markup.RenderContext, v *ast.Link, r
 	if !isAnchorFragment && !markup.IsFullURLBytes(link) {
 		base := ctx.Links.Base
 		if ctx.IsWiki {
-			base = ctx.Links.WikiLink()
+			if filepath.Ext(string(link)) == "" {
+				// This link doesn't have a file extension - assume a regular wiki link
+				base = ctx.Links.WikiLink()
+			} else if markup.Type(string(link)) != "" {
+				// If it's a file type we can render, use a regular wiki link
+				base = ctx.Links.WikiLink()
+			} else {
+				// Otherwise, use a raw link instead
+				base = ctx.Links.WikiRawLink()
+			}
 		} else if ctx.Links.HasBranchInfo() {
 			base = ctx.Links.SrcLink()
 		}