From b594ff78b22452b1260286f86fc5a40dbf3d38d9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C5=99emysl=20Eric=20Janouch?= <p@janouch.name>
Date: Tue, 16 Apr 2024 07:38:23 +0200
Subject: [PATCH] Improve shell quoting

---
 Makefile          |  2 ++
 acid.adoc         |  3 +++
 acid.go           | 27 ++++++++++++++++++++++++---
 acid.yaml.example |  6 +++---
 acid_test.go      | 32 ++++++++++++++++++++++++++++++++
 5 files changed, 64 insertions(+), 6 deletions(-)
 create mode 100644 acid_test.go

diff --git a/Makefile b/Makefile
index 1fd3dc3..455c22d 100644
--- a/Makefile
+++ b/Makefile
@@ -9,5 +9,7 @@ acid: acid.go
 	go build -ldflags "-X 'main.projectVersion=$(version)'" -o $@
 acid.1: acid.adoc
 	asciidoctor -b manpage -a release-version=$(version) -o $@ acid.adoc
+test: all
+	go test
 clean:
 	rm -f $(outputs)
diff --git a/acid.adoc b/acid.adoc
index 4c56562..6775d52 100644
--- a/acid.adoc
+++ b/acid.adoc
@@ -71,6 +71,9 @@ which has the following fields:
 *CloneURL*::
 	Gitea link for cloning the repository over HTTP.
 
+The special *quote* template function quotes fields for safe usage
+in *sh*(1) command arguments.
+
 Runners
 -------
 Runners receive the following additional environment variables:
diff --git a/acid.go b/acid.go
index b029c2a..2c59c38 100644
--- a/acid.go
+++ b/acid.go
@@ -93,10 +93,30 @@ func parseConfig(path string) error {
 	}
 
 	var err error
-	gNotifyScript, err = ttemplate.New("notify").Parse(gConfig.Notify)
+	gNotifyScript, err =
+		ttemplate.New("notify").Funcs(shellFuncs).Parse(gConfig.Notify)
 	return err
 }
 
+var shellFuncs = ttemplate.FuncMap{
+	"quote": func(word string) string {
+		// History expansion is annoying, don't let it cut us.
+		if strings.IndexRune(word, '!') >= 0 {
+			return "'" + strings.ReplaceAll(word, "'", `'"'"'`) + "'"
+		}
+
+		const special = "$`\"\\"
+		quoted := []rune{'"'}
+		for _, r := range word {
+			if strings.IndexRune(special, r) >= 0 {
+				quoted = append(quoted, '\\')
+			}
+			quoted = append(quoted, r)
+		}
+		return string(append(quoted, '"'))
+	},
+}
+
 // --- Utilities ---------------------------------------------------------------
 
 func giteaSign(b []byte) string {
@@ -910,8 +930,9 @@ func executorRunTask(ctx context.Context, task Task) error {
 	//  - we might have to clone submodules as well.
 	// Otherwise, we could download a source archive from Gitea,
 	// and use SFTP to upload it to the runner.
-	tmplScript, err := ttemplate.New("script").Parse(rt.Runner.Setup + "\n" +
-		rt.ProjectRunner.Setup + "\n" + rt.ProjectRunner.Build)
+	tmplScript, err := ttemplate.New("script").Funcs(shellFuncs).
+		Parse(rt.Runner.Setup + "\n" +
+			rt.ProjectRunner.Setup + "\n" + rt.ProjectRunner.Build)
 	if err != nil {
 		return fmt.Errorf("script: %w", err)
 	}
diff --git a/acid.yaml.example b/acid.yaml.example
index a80cc4c..b34abf0 100644
--- a/acid.yaml.example
+++ b/acid.yaml.example
@@ -44,9 +44,9 @@ runners:
     setup: |
       set -ex
       sudo pacman -Syu --noconfirm git
-      git clone --recursive '{{.CloneURL}}' '{{.Repo}}'
-      cd '{{.Repo}}'
-      git -c advice.detachedHead=false checkout '{{.Hash}}'
+      git clone --recursive {{quote .CloneURL}} {{quote .Repo}}
+      cd {{quote .Repo}}
+      git -c advice.detachedHead=false checkout {{quote .Hash}}
 
 # Configuration for individual Gitea repositories.
 projects:
diff --git a/acid_test.go b/acid_test.go
new file mode 100644
index 0000000..f23d892
--- /dev/null
+++ b/acid_test.go
@@ -0,0 +1,32 @@
+package main
+
+import (
+	"bytes"
+	"testing"
+	ttemplate "text/template"
+)
+
+func TestTemplateQuote(t *testing.T) {
+	// Ideally, we should back-parse it using sh syntax.
+	// This is an unnecessarily fragile test.
+	for _, test := range []struct {
+		input, output string
+	}{
+		{`!!`, `'!!'`},
+		{``, `""`},
+		{`${var}`, `"\${var}"`},
+		{"`cat`", "\"\\`cat\\`\""},
+		{`"魚\"`, `"\"魚\\\""`},
+	} {
+		var b bytes.Buffer
+		err := ttemplate.Must(ttemplate.New("test").
+			Funcs(shellFuncs).Parse("{{quote .}}")).Execute(&b, test.input)
+		if err != nil {
+			t.Errorf("template execution error: %s\n", err)
+		}
+		if b.String() != test.output {
+			t.Errorf("%q should be quoted os %q, not %q\n",
+				test.input, test.output, b.String())
+		}
+	}
+}