test: x/tx/signing/aminojson: fuzz SignModeHandler.GetSignBytes (#16734)

Co-authored-by: Marko <marbar3778@yahoo.com>

x/tx/signing/aminojson/fuzz_test.go

@@ -0,0 +1,79 @@
+package aminojson
+
+import (
+	"context"
+	"encoding/json"
+	"testing"
+
+	"github.com/google/gofuzz"
+
+	bankv1beta1 "cosmossdk.io/api/cosmos/bank/v1beta1"
+	basev1beta1 "cosmossdk.io/api/cosmos/base/v1beta1"
+	txv1beta1 "cosmossdk.io/api/cosmos/tx/v1beta1"
+	"cosmossdk.io/x/tx/signing/testutil"
+)
+
+func FuzzSignModeGetSignBytes(f *testing.F) {
+	if testing.Short() {
+		f.Skip("not running in -short mode")
+	}
+
+	// 1. Create seeds.
+	fee := &txv1beta1.Fee{
+		Amount: []*basev1beta1.Coin{{Denom: "uatom", Amount: "1000"}},
+	}
+	seed := &testutil.HandlerArgumentOptions{
+		ChainID: "test-chain",
+		Memo:    "sometestmemo",
+		Tip: &txv1beta1.Tip{
+			Tipper: "tipper",
+			Amount: []*basev1beta1.Coin{{Denom: "Tip-token", Amount: "10"}},
+		},
+		Msg: &bankv1beta1.MsgSend{
+			FromAddress: "foo",
+			ToAddress:   "bar",
+			Amount:      []*basev1beta1.Coin{{Denom: "demon", Amount: "100"}},
+		},
+		AccNum:        1,
+		AccSeq:        2,
+		SignerAddress: "signerAddress",
+		Fee:           fee,
+	}
+
+	gf := fuzz.New()
+	for i := 0; i < 1e4; i++ {
+		blob, err := json.Marshal(seed)
+		if err != nil {
+			f.Fatal(err)
+		}
+		f.Add(blob)
+
+		// 1.5. Mutate the seed for the next iteration.
+		// gofuzz cannot handle mutating "&bankv1beta1.MsgSend",
+		// hence why we are mutating fields individually.
+		gf.Fuzz(&seed.ChainID)
+		gf.Fuzz(&seed.Memo)
+		gf.Fuzz(seed.Tip)
+		gf.Fuzz(&seed.AccNum)
+		gf.Fuzz(&seed.AccSeq)
+		gf.Fuzz(seed.Fee)
+		gf.Fuzz(&seed.SignerAddress)
+	}
+
+	ctx := context.Background()
+	handler := NewSignModeHandler(SignModeHandlerOptions{})
+
+	// 2. Now run the fuzzers.
+	f.Fuzz(func(t *testing.T, in []byte) {
+		opts := new(testutil.HandlerArgumentOptions)
+		if err := json.Unmarshal(in, opts); err != nil {
+			return
+		}
+
+		signerData, txData, err := testutil.MakeHandlerArguments(*opts)
+		if err != nil {
+			return
+		}
+		_, _ = handler.GetSignBytes(ctx, signerData, txData)
+	})
+}