fuzz: introduce continuous fuzzing for Caddy (#2723)

* fuzz: lay down the foundation for continuous fuzzing

* improve the fuzzers and add some

* fuzz: add Fuzzit badge to README & enable fuzzers submission in CI

* v2-fuzz: do away with the submodule approach for fuzzers

* fuzz: enable fuzzit

2 files changed, 78 insertions, 0 deletions

diff --git a/caddyconfig/httpcaddyfile/adapter_fuzz.go b/caddyconfig/httpcaddyfile/adapter_fuzz.go
new file mode 100644
index 0000000..1748b66
--- /dev/null
+++ b/caddyconfig/httpcaddyfile/adapter_fuzz.go
@@ -0,0 +1,49 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build gofuzz
+// +build gofuzz_libfuzzer
+
+package httpcaddyfile
+
+import (
+	"bytes"
+
+	"github.com/caddyserver/caddy/v2"
+	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
+)
+
+func FuzzHTTPCaddyfileAdapter(data []byte) int {
+	adapter := caddyfile.Adapter{
+		ServerType: ServerType{},
+	}
+	b, warns, err := adapter.Adapt(data, nil)
+	// Adapt func calls the Setup() func of the ServerType,
+	// thus it's going across multiple layers, each can
+	// return warnings or errors. Marking the presence of
+	// errors or warnings as interesting in this case
+	// could push the fuzzer towards a path where we only
+	// catch errors. Let's push the fuzzer to where it passes
+	// but breaks.
+	if (err != nil) || (warns != nil && len(warns) > 0) {
+		return 0
+	}
+
+	// adapted Caddyfile should be parseable by the configuration loader in admin.go
+	err = caddy.Load(bytes.NewReader(b))
+	if err != nil {
+		return 0
+	}
+	return 1
+}
diff --git a/caddyconfig/httpcaddyfile/addresses_fuzz.go b/caddyconfig/httpcaddyfile/addresses_fuzz.go
new file mode 100644
index 0000000..26f3696
--- /dev/null
+++ b/caddyconfig/httpcaddyfile/addresses_fuzz.go
@@ -0,0 +1,29 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build gofuzz
+// +build gofuzz_libfuzzer
+
+package httpcaddyfile
+
+func FuzzParseAddress(data []byte) int {
+	addr, err := ParseAddress(string(data))
+	if err != nil {
+		if addr == (Address{}) {
+			return 1
+		}
+		return 0
+	}
+	return 1
+}