Golang fuzzing fixed-length strings

Question

I'm looking for a efficient way to test fixed-length strings via fuzzing (so that only the content of the string is variable, not the length). My first idea was to use arrays for this like

f.Fuzz(func(t *testing.T, stringUnderTest [8]byte))

Sadly this doesn't work, as arrays are not supported (https://go.dev/security/fuzz/). Is there any way to tell the fuzzer: "This string is only 8 digits"?

Vlad · Accepted Answer · 2024-05-03 11:42:36Z

0

You can translate several machine words to the bytes sequence.

func wordsToBytes(words ...uint64) []byte {
    buf := make([]byte, 8*len(words))
    for n, v := range words {
        for i := range 8 {
            buf[n+i] = byte(v >> i * 8)
        }
    }
    return buf
 }

Then your fuzz target can accept several uint64 which will be converted to bytes.

func FuzzFoo(f *testing.F) {

    f.Fuzz(func(t *testing.T, w1 uint64, w2 uint64) {
        raw := wordsToBytes(w1, w2)

answered May 3, 2024 at 11:42

Vlad

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