keyformat, internal: add fuzzers

Adds fuzzers that have discovered some bugs, like:
* cosmos#760
* cosmos#761

internal/rand/fuzz_test.go

@@ -0,0 +1,34 @@
+package common
+
+import (
+	mrand "math/rand"
+	"testing"
+)
+
+func TestRandStrHuge(t *testing.T) {
+	_ = RandStr(8455134228352958140)
+}
+
+func FuzzRandStr(f *testing.F) {
+	// 1. Seed the fuzzer with lengths.
+	mr := mrand.New(mrand.NewSource(10))
+	for i := 0; i < 100; i++ {
+		f.Add(mr.Int())
+	}
+
+	// 2. Now run the fuzzer.
+	rr := NewRand()
+	f.Fuzz(func(t *testing.T, n int) {
+		s := rr.Str(n)
+		// Ensure that we've got alphanumeric sequences entirely.
+		for _, c := range s {
+			switch {
+			case c >= '0' && c <= '9':
+			case c >= 'a' && c <= 'z':
+			case c >= 'A' && c <= 'Z':
+			default:
+				t.Fatalf("found a non-alphanumeric value %c in %q", c, s)
+			}
+		}
+	})
+}

keyformat/fuzz_test.go

@@ -0,0 +1,68 @@
+package keyformat
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+	"testing"
+)
+
+func FuzzKeyFormatKeyBytes(f *testing.F) {
+	if testing.Short() {
+		f.Skip("in -short mode")
+	}
+
+	// 1. Create some seeds.
+	seeds := []*KeyFormat{
+		NewKeyFormat('a', 1, 2, 3, 5, 6, 0),
+		NewKeyFormat('b', 1, 2, 3, 5, 6, 1),
+		NewKeyFormat('b', 9, 21),
+		NewKeyFormat(byte('e'), 8, 8, 8),
+		NewKeyFormat(byte('e'), 8, 0),
+	}
+
+	type envelope struct {
+		KF *KeyFormat `json:"kf"`
+		BS [][]byte   `json:"bs"`
+	}
+
+	for _, kf := range seeds {
+		bsL := [][][]byte{
+			[][]byte{[]byte(""), []byte("abcdefgh")},
+			[][]byte{{1, 2, 3, 4, 5, 6, 7, 8}, {1, 2, 3, 4, 5, 6, 7, 8, 9}},
+			[][]byte{{1, 2, 3, 4, 5, 6, 7, 8}, []byte("hellohello")},
+			[][]byte{{1, 2, 3, 4, 5, 6, 7, 8}, {1, 2, 3, 4, 5, 6, 7, 8}, {1, 1, 2, 2, 3, 3}},
+		}
+		for _, bs := range bsL {
+			blob, err := json.Marshal(&envelope{KF: kf, BS: bs})
+			if err != nil {
+				f.Fatal(err)
+			}
+			f.Add(blob)
+		}
+	}
+
+	// 2. Fuzz it now.
+	f.Fuzz(func(t *testing.T, inputJSON []byte) {
+		defer func() {
+			if r := recover(); r != nil {
+				str := fmt.Sprintf("%s", r)
+				if !strings.Contains(str, "provided to KeyFormat.KeyBytes() is longer than the") {
+					// Re-raise the panic as it panicked in an unexpected place.
+					panic(r)
+				}
+			}
+		}()
+
+		env := new(envelope)
+		if err := json.Unmarshal(inputJSON, env); err != nil {
+			return
+		}
+
+		kf := env.KF
+		if kf == nil {
+			return
+		}
+		_ = kf.KeyBytes(env.BS...)
+	})
+}