1 files changed, 108 insertions, 0 deletions
diff --git a/src/crypto/x509/root_test.go b/src/crypto/x509/root_test.go
new file mode 100644
index 0000000..94ee6a6
--- /dev/null
+++ b/src/crypto/x509/root_test.go
@@ -0,0 +1,108 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+import (
+	"testing"
+)
+
+func TestFallbackPanic(t *testing.T) {
+	defer func() {
+		if recover() == nil {
+			t.Fatal("Multiple calls to SetFallbackRoots should panic")
+		}
+	}()
+	SetFallbackRoots(nil)
+	SetFallbackRoots(nil)
+}
+
+func TestFallback(t *testing.T) {
+	// call systemRootsPool so that the sync.Once is triggered, and we can
+	// manipulate systemRoots without worrying about our working being overwritten
+	systemRootsPool()
+	if systemRoots != nil {
+		originalSystemRoots := *systemRoots
+		defer func() { systemRoots = &originalSystemRoots }()
+	}
+
+	tests := []struct {
+		name            string
+		systemRoots     *CertPool
+		systemPool      bool
+		poolContent     []*Certificate
+		forceFallback   bool
+		returnsFallback bool
+	}{
+		{
+			name:            "nil systemRoots",
+			returnsFallback: true,
+		},
+		{
+			name:            "empty systemRoots",
+			systemRoots:     NewCertPool(),
+			returnsFallback: true,
+		},
+		{
+			name:        "empty systemRoots system pool",
+			systemRoots: NewCertPool(),
+			systemPool:  true,
+		},
+		{
+			name:        "filled systemRoots system pool",
+			systemRoots: NewCertPool(),
+			poolContent: []*Certificate{{}},
+			systemPool:  true,
+		},
+		{
+			name:        "filled systemRoots",
+			systemRoots: NewCertPool(),
+			poolContent: []*Certificate{{}},
+		},
+		{
+			name:            "filled systemRoots, force fallback",
+			systemRoots:     NewCertPool(),
+			poolContent:     []*Certificate{{}},
+			forceFallback:   true,
+			returnsFallback: true,
+		},
+		{
+			name:            "filled systemRoot system pool, force fallback",
+			systemRoots:     NewCertPool(),
+			poolContent:     []*Certificate{{}},
+			systemPool:      true,
+			forceFallback:   true,
+			returnsFallback: true,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			fallbacksSet = false
+			systemRoots = tc.systemRoots
+			if systemRoots != nil {
+				systemRoots.systemPool = tc.systemPool
+			}
+			for _, c := range tc.poolContent {
+				systemRoots.AddCert(c)
+			}
+			if tc.forceFallback {
+				t.Setenv("GODEBUG", "x509usefallbackroots=1")
+			} else {
+				t.Setenv("GODEBUG", "x509usefallbackroots=0")
+			}
+
+			fallbackPool := NewCertPool()
+			SetFallbackRoots(fallbackPool)
+
+			systemPoolIsFallback := systemRoots == fallbackPool
+
+			if tc.returnsFallback && !systemPoolIsFallback {
+				t.Error("systemRoots was not set to fallback pool")
+			} else if !tc.returnsFallback && systemPoolIsFallback {
+				t.Error("systemRoots was set to fallback pool when it shouldn't have been")
+			}
+		})
+	}
+}