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Reduce FuzzSign1 memory consumption #104

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merged 1 commit into from
Sep 27, 2022
Merged

Reduce FuzzSign1 memory consumption #104

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58 changes: 40 additions & 18 deletions fuzz_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,12 @@ import (
"github.com/veraison/go-cose"
)

var supportedAlgorithms = [...]cose.Algorithm{
cose.AlgorithmPS256, cose.AlgorithmPS384, cose.AlgorithmPS512,
cose.AlgorithmES256, cose.AlgorithmES384, cose.AlgorithmES512,
cose.AlgorithmEd25519,
}

func FuzzSign1Message_UnmarshalCBOR(f *testing.F) {
testdata, err := os.ReadDir("testdata")
if err != nil {
Expand Down Expand Up @@ -58,6 +64,9 @@ func FuzzSign1Message_UnmarshalCBOR(f *testing.F) {
return false
}
b1, err := enc.Marshal(tmp)
if err != nil {
return false
}
return bytes.Equal(b, b1)
}
f.Fuzz(func(t *testing.T, b []byte) {
Expand Down Expand Up @@ -107,6 +116,18 @@ func FuzzSign1(f *testing.F) {
f.Add(hdr, mustHexToBytes(tc.Sign1.Payload), mustHexToBytes(tc.Sign1.External))
}
}
// Generating new keys consumes a lot of memory,
// to the point that the host can decide to kill the fuzzing execution
// when the memory is low.
// We can avoid this by always reusing the same signer and verifier for a given algorithm.
signverif := make(map[cose.Algorithm]signVerifier, len(supportedAlgorithms))
for _, alg := range supportedAlgorithms {
signverif[alg], err = newSignerWithEphemeralKey(alg)
if err != nil {
f.Fatal(err)
}
}

f.Fuzz(func(t *testing.T, hdr_data, payload, external []byte) {
hdr := make(cose.ProtectedHeader)
err := hdr.UnmarshalCBOR(hdr_data)
Expand All @@ -117,40 +138,36 @@ func FuzzSign1(f *testing.F) {
if err != nil {
return
}
pkey, err := newSignerWithEphemeralKey(alg)
if err != nil {
sv, ok := signverif[alg]
if !ok {
return
}
signer, err := cose.NewSigner(alg, pkey)
if err != nil {
t.Fatal(err)
}
verifier, err := cose.NewVerifier(alg, pkey.Public())
if err != nil {
t.Fatal(err)
}
msg := cose.Sign1Message{
Headers: cose.Headers{Protected: hdr},
Payload: payload,
}
err = msg.Sign(rand.Reader, external, signer)
err = msg.Sign(rand.Reader, external, sv.signer)
if err != nil {
t.Fatal(err)
}
err = msg.Verify(external, verifier)
err = msg.Verify(external, sv.verifier)
if err != nil {
t.Fatal(err)
}
err = msg.Verify(append(external, []byte{0}...), verifier)
err = msg.Verify(append(external, []byte{0}...), sv.verifier)
if err == nil {
t.Fatal("verification error expected")
}
})
}

func newSignerWithEphemeralKey(alg cose.Algorithm) (crypto.Signer, error) {
type signVerifier struct {
signer cose.Signer
verifier cose.Verifier
}

func newSignerWithEphemeralKey(alg cose.Algorithm) (sv signVerifier, err error) {
var key crypto.Signer
var err error
switch alg {
case cose.AlgorithmPS256:
key, err = rsa.GenerateKey(rand.Reader, 2048)
Expand All @@ -167,10 +184,15 @@ func newSignerWithEphemeralKey(alg cose.Algorithm) (crypto.Signer, error) {
case cose.AlgorithmEd25519:
_, key, err = ed25519.GenerateKey(rand.Reader)
default:
return nil, cose.ErrAlgorithmNotSupported
err = cose.ErrAlgorithmNotSupported
}
if err != nil {
return
}
sv.signer, err = cose.NewSigner(alg, key)
if err != nil {
return nil, err
return
}
return key, nil
sv.verifier, err = cose.NewVerifier(alg, key.Public())
return
}