git » chasquid » commit 4b0b31a

diff --git a/internal/dkim/file_test.go b/internal/dkim/file_test.go
index 443f26d..dfbc7d4 100644
--- a/internal/dkim/file_test.go
+++ b/internal/dkim/file_test.go
@@ -86,6 +86,23 @@ func equalErrors(a, b error) bool {
 	return a.Error() == b.Error()
 }
 
+// Add the messages from the file-based tests to the fuzzing corpus.
+func addTestdataCorpus(f *testing.F) {
+	f.Helper()
+
+	msgfs, err := filepath.Glob("testdata/*.msg")
+	if err != nil {
+		f.Fatalf("error finding test files: %v", err)
+	}
+	for _, msgf := range msgfs {
+		c, err := os.ReadFile(msgf)
+		if err != nil {
+			f.Fatalf("error reading %q: %v", msgf, err)
+		}
+		f.Add(toCRLF(string(c)))
+	}
+}
+
 func mustReadFile(t *testing.T, path string) string {
 	t.Helper()
 	contents, err := os.ReadFile(path)
diff --git a/internal/dkim/sign_test.go b/internal/dkim/sign_test.go
index f5b0239..05a8756 100644
--- a/internal/dkim/sign_test.go
+++ b/internal/dkim/sign_test.go
@@ -1,6 +1,7 @@
 package dkim
 
 import (
+	"context"
 	"crypto/ecdsa"
 	"crypto/ed25519"
 	"crypto/elliptic"
@@ -376,3 +377,57 @@ func TestFormatHeaders(t *testing.T) {
 		}
 	}
 }
+
+func FuzzSignAndVerify(f *testing.F) {
+	f.Add(basicMessage)
+	f.Add("From: a@b\r\n\r\n")
+	f.Add("")
+
+	// Repeated headers with different values.
+	f.Add("From: a@b\r\nTo: c@d\r\n e@f\r\nTo: g@h\r\n\r\nbody\r\n")
+
+	// Non-ASCII header name (U+017F is a long s).
+	f.Add("From: a@b\r\nſubject: x\r\n\r\nbody\r\n")
+
+	// Messages from the file-based tests, which have more realistic headers,
+	// including existing DKIM signatures.
+	addTestdataCorpus(f)
+
+	// Use a fixed key, as generating one for each run would be too slow.
+	priv := ed25519.NewKeyFromSeed(make([]byte, ed25519.SeedSize))
+	pub := priv.Public().(ed25519.PublicKey)
+	ctx := WithLookupTXTFunc(context.Background(),
+		makeLookupTXT(map[string][]string{
+			"test._domainkey.example.com": {
+				"v=DKIM1; k=ed25519; p=" +
+					base64.StdEncoding.EncodeToString(pub),
+			},
+		}))
+
+	s := &Signer{
+		Domain:   "example.com",
+		Selector: "test",
+		Signer:   priv,
+	}
+
+	f.Fuzz(func(t *testing.T, msg string) {
+		sig, err := s.Sign(ctx, msg)
+		if err != nil {
+			return
+		}
+
+		// Any message we can sign, we must be able to verify.
+		// Our signature is the first one, so it's always verified even if
+		// the message has other signatures.
+		res, err := VerifyMessage(ctx, addSig(sig, msg))
+		if err != nil {
+			t.Fatalf("VerifyMessage error: %v", err)
+		}
+		if len(res.Results) == 0 {
+			t.Fatalf("signature not found when verifying")
+		}
+		if r := res.Results[0]; r.State != SUCCESS {
+			t.Errorf("signature did not verify: %v / %v", r.State, r.Error)
+		}
+	})
+}
diff --git a/internal/dkim/verify_test.go b/internal/dkim/verify_test.go
index 01063f8..6b92b77 100644
--- a/internal/dkim/verify_test.go
+++ b/internal/dkim/verify_test.go
@@ -520,3 +520,38 @@ func TestAuthenticationResults(t *testing.T) {
 		}
 	}
 }
+
+func FuzzVerifyMessage(f *testing.F) {
+	addTestdataCorpus(f)
+
+	// Return valid keys for every domain, so we can get past the key lookup
+	// and exercise the rest of the verification. The ed25519 key is the one
+	// used by testdata/01-rfc8463.
+	ctx := WithLookupTXTFunc(context.Background(),
+		func(ctx context.Context, domain string) ([]string, error) {
+			return []string{
+				"v=DKIM1; k=ed25519; p=" + exampleEd25519KeyB64,
+				"v=DKIM1; k=rsa; p=" + exampleRSAKeyB64,
+			}, nil
+		})
+
+	f.Fuzz(func(t *testing.T, msg string) {
+		res, err := VerifyMessage(ctx, msg)
+		if err != nil {
+			return
+		}
+
+		if res.Found != uint(len(res.Results)) {
+			t.Errorf("found %d signatures, but got %d results",
+				res.Found, len(res.Results))
+		}
+		if res.Valid > res.Found {
+			t.Errorf("%d valid signatures, but only %d found",
+				res.Valid, res.Found)
+		}
+
+		// This is always called on the result when receiving a message, so
+		// exercise it too.
+		res.AuthenticationResults()
+	})
+}