nfs/internal/rpc/fuzz_test.go

// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: MIT

package rpc

import (
	"bytes"
	"testing"
)

// FuzzReadRecord feeds arbitrary fragment streams into the reassembler:
// no input may panic, allocate without bound or return anything but a
// record, io.EOF, ErrRecordTooLarge or a truncation error.
func FuzzReadRecord(f *testing.F) {
	f.Add([]byte{0x80, 0, 0, 4, 'a', 'b', 'c', 'd'})
	f.Add([]byte{0, 0, 0, 4, 'a', 'b', 'c', 'd', 0x80, 0, 0, 0})
	f.Add([]byte{0xff, 0xff, 0xff, 0xff})
	f.Add([]byte{0, 0, 0, 1})
	f.Fuzz(func(t *testing.T, data []byte) {
		rec, err := ReadRecord(bytes.NewReader(data), 1<<16)
		if err == nil && len(rec) > 1<<16 {
			t.Fatalf("a record of %d bytes against a limit of %d", len(rec), 1<<16)
		}
	})
}

// FuzzDecodeMessage feeds arbitrary records through the call and reply
// decoders: no input may panic, and every failure arrives as an error.
func FuzzDecodeMessage(f *testing.F) {
	call, err := AppendCall(nil, Call{XID: 1, Program: 100003, Version: 4, Procedure: 1,
		Cred: Auth{Flavor: FlavorSys, Body: []byte{1, 2}}})
	if err != nil {
		f.Fatal(err)
	}
	reply, err := AppendAcceptedReply(nil, 1, AuthNull, AcceptSuccess, Mismatch{})
	if err != nil {
		f.Fatal(err)
	}
	reply = append(reply, 0, 0, 0, 42)
	f.Add(call)
	f.Add(reply)
	f.Add(AppendRejectedReply(nil, 2, AuthBadVerf))
	f.Add([]byte{0, 0, 0, 1, 0, 0, 0, 1})
	f.Add([]byte{0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 2})
	f.Fuzz(func(t *testing.T, data []byte) {
		// The property under test is that none of these panics; every
		// malformed input must arrive as an ordinary error.
		_, _, _ = DecodeCall(data)
		_, _ = DecodeReply(data)
		_, _, _ = PeekHeader(data)
		_, _ = DecodeAuthSysBody(data)
		_, _ = DecodeGSSCred(data)
		_, _, _, _, _, _ = DecodeGSSInitRes(data)
	})
}