first commit

internal/sieve/sieve_fuzz_test.go

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+package sieve
+
+import "testing"
+
+func FuzzParse(f *testing.F) {
+	f.Add(`if header :contains "subject" "invoice" { fileinto "Invoices"; stop; }`)
+	f.Add(`if header :is "from" "boss@example.com" { fileinto "Important"; } elsif header :contains "subject" "urgent" { fileinto "Important"; } else { keep; }`)
+	f.Add("")
+	f.Add("keep;")
+	f.Add("if true { discard; }")
+	f.Add(`if header :contains "subject" { fileinto "X" }`)
+	f.Add("if header { }")
+	f.Add("{{{{{{{")
+	f.Add(`if header :contains "a" "b`)
+	f.Add("if header :bogus \"x\" \"y\" { keep; }")
+	f.Add("fileinto;")
+
+	f.Fuzz(func(t *testing.T, data string) {
+		// This is the fuzz target most directly exposed to untrusted input
+		// in production — every ManageSieve PUTSCRIPT is parsed by this
+		// exact function before storage. A crash here would be a remotely
+		// triggerable DoS against an authenticated user's own session, so
+		// "never panics" matters more here than for the calendar/contact
+		// parsers.
+		defer func() {
+			if r := recover(); r != nil {
+				t.Fatalf("Parse panicked on input %q: %v", data, r)
+			}
+		}()
+		Parse(data)
+	})
+}