Fix Peek error, cipherW constant, and file close handling

cmd/tle/tle.go

@@ -48,7 +48,9 @@ func run() error {
 			return fmt.Errorf("failed to open input file %q: %v", name, err)
 		}
 		defer func(f *os.File) {
-			err = f.Close()
+			if closeErr := f.Close(); closeErr != nil && err == nil {
+				err = fmt.Errorf("close input file: %w", closeErr)
+			}
 		}(f)
 		src = f
 	}
@@ -60,7 +62,9 @@ func run() error {
 			return fmt.Errorf("failed to open output file %q: %v", name, err)
 		}
 		defer func(f *os.File) {
-			err = f.Close()
+			if closeErr := f.Close(); closeErr != nil && err == nil {
+				err = fmt.Errorf("close output file: %w", closeErr)
+			}
 		}(f)
 		dst = f
 	}

tlock.go

@@ -89,7 +89,8 @@ func (t Tlock) Encrypt(dst io.Writer, src io.Reader, roundNumber uint64) (err er
 func (t Tlock) Decrypt(dst io.Writer, src io.Reader) error {
 	rr := bufio.NewReader(src)
 
-	if start, _ := rr.Peek(len(armor.Header)); string(start) == armor.Header {
+	start, err := rr.Peek(len(armor.Header))
+	if err == nil && string(start) == armor.Header {
 		src = armor.NewReader(rr)
 	} else {
 		src = rr
@@ -223,6 +224,8 @@ func TimeUnlock(scheme crypto.Scheme, publicKey kyber.Point, beacon chain.Beacon
 // =============================================================================
 
 // These constants define the size of the different CipherDEK fields.
+// cipherWLen is distinct from cipherVLen even if equal; keep constants separate
+// to preserve format invariants.
 const (
 	cipherVLen = 16
 	cipherWLen = 16
@@ -261,10 +264,10 @@ func BytesToCiphertext(scheme crypto.Scheme, b []byte) (*ibe.Ciphertext, error)
 	cipherV := make([]byte, cipherVLen)
 	copy(cipherV, b[kyberPointLen:kyberPointLen+cipherVLen])
 
-	cipherW := make([]byte, cipherVLen)
+	cipherW := make([]byte, cipherWLen)
 	copy(cipherW, b[kyberPointLen+cipherVLen:])
-	if len(b[kyberPointLen+cipherVLen:]) != cipherVLen {
-		return nil, fmt.Errorf("invalid ciphertext length: %d", len(b[kyberPointLen+cipherVLen:]))
+	if len(b[kyberPointLen+cipherVLen:]) != cipherWLen {
+		return nil, fmt.Errorf("invalid ciphertext W length: got %d, want %d", len(b[kyberPointLen+cipherVLen:]), cipherWLen)
 	}
 
 	u := scheme.KeyGroup.Point()

tlock_test.go

@@ -376,6 +376,45 @@ UnBmtsw6U2LlKh8iDf0E1PfwDenmKFfQaAGm0WLxdlzP8Q==
 	})
 }
 
+func TestBytesToCiphertext_MalformedInput(t *testing.T) {
+	network, err := fixed.FromInfo(`{"public_key":"83cf0f2896adee7eb8b5f01fcad3912212c437e0073e911fb90022d3e760183c8c4b450b6a0a6c3ac6a5776a2d1064510d1fec758c921cc22b0e17e63aaf4bcb5ed66304de9cf809bd274ca73bab4af5a6e9c76a4bc09e76eae8991ef5ece45a","period":3,"genesis_time":1692803367,"genesis_seed":"f477d5c89f21a17c863a7f937c6a6d15859414d2be09cd448d4279af331c5d3e","chain_hash":"52db9ba70e0cc0f6eaf7803dd07447a1f5477735fd3f661792ba94600c84e971","scheme":"bls-unchained-g1-rfc9380","beacon_id":"quicknet"}`)
+	require.NoError(t, err)
+	scheme := network.Scheme()
+	kyberPointLen := scheme.KeyGroup.PointLen()
+	validLen := kyberPointLen + 16 + 16
+
+	tests := []struct {
+		name   string
+		input  []byte
+		substr string
+	}{
+		{"truncated missing W", make([]byte, kyberPointLen+16), "incorrect length"},
+		{"empty", nil, "incorrect length"},
+		{"too long", make([]byte, validLen+10), "incorrect length"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			_, err := tlock.BytesToCiphertext(scheme, tt.input)
+			require.Error(t, err)
+			require.Contains(t, err.Error(), tt.substr, "error should be explicit about length")
+			require.Contains(t, err.Error(), "got", "crypto errors should include actual value")
+		})
+	}
+}
+
+func TestDecrypt_PeekShortRead(t *testing.T) {
+	network, err := fixed.FromInfo(`{"public_key":"83cf0f2896adee7eb8b5f01fcad3912212c437e0073e911fb90022d3e760183c8c4b450b6a0a6c3ac6a5776a2d1064510d1fec758c921cc22b0e17e63aaf4bcb5ed66304de9cf809bd274ca73bab4af5a6e9c76a4bc09e76eae8991ef5ece45a","period":3,"genesis_time":1692803367,"genesis_seed":"f477d5c89f21a17c863a7f937c6a6d15859414d2be09cd448d4279af331c5d3e","chain_hash":"52db9ba70e0cc0f6eaf7803dd07447a1f5477735fd3f661792ba94600c84e971","scheme":"bls-unchained-g1-rfc9380","beacon_id":"quicknet"}`)
+	require.NoError(t, err)
+
+	// input shorter than armor header (32 bytes); Peek will fail/short-read
+	// should fallback to non-armor path and age.Decrypt will return error
+	shortInput := strings.NewReader("short")
+	var dst bytes.Buffer
+
+	err = tlock.New(network).Decrypt(&dst, shortInput)
+	require.Error(t, err, "short input should not panic; Decrypt should return age error")
+}
+
 func TestInteropWithJS(t *testing.T) {
 	t.Run("on Mainnet with G1 sigs", func(t *testing.T) {
 		cipher := `-----BEGIN AGE ENCRYPTED FILE-----