What causes "encrypted asset metadata is too large" in siyuan-note/siyuan?

Reduce the metadata content (shorter original name, no extra fields) below the 1 MiB encrypted-size cap

encrypted asset metadata is too large

Error message

encrypted asset metadata is too large

What it means

EncryptAsset builds an encrypted asset container whose metadata (original name, size, chunk count, container ID) is encrypted as one AAD-bound blob and length-prefixed with a uint32. The kernel throws this error when the encrypted metadata exceeds encryptedAssetMetadataMaxSize (1 MiB), which would make the length prefix and parsing invariants unsatisfiable.

Solutions

Reduce the metadata content (shorter original name, no extra fields) below the 1 MiB encrypted-size cap
Check len(plaintext metadata) before calling EncryptAsset and reject inputs that could exceed encryptedAssetMetadataMaxSize after encryption overhead (~16-byte tag + nonce)
If larger metadata is genuinely needed, bump the format limit in a versioned container-format change, not ad hoc

Example fix

// before
enc, err := model.EncryptAsset(boxID, diskName, originalName, data)
// after
if len(originalName) > 255 { return errors.New("original name too long") }
enc, err := model.EncryptAsset(boxID, diskName, originalName, data)

Defensive patterns

Strategy: validation

Validate before calling

if len(metadataJSON) > 1<<20-64 {
    return errors.New("asset metadata would exceed the 1 MiB encrypted limit")
}
enc, err := model.EncryptAsset(boxID, diskName, name, data)

Try / catch

enc, err := model.EncryptAsset(boxID, diskName, name, data)
if err != nil && strings.Contains(err.Error(), "metadata is too large") {
    return shrinkMetadataAndRetry(name, data)
}

Prevention

Keep asset original names short (e.g. cap at 255 bytes) before encryption
Never append custom fields to the encrypted metadata struct without checking the size budget
Remember ciphertext adds nonce+tag overhead (~28+ bytes) to plaintext size

When it happens

Trigger: Calling model.EncryptAsset with a metadata payload whose ciphertext is larger than 1 MiB — practically only via abnormally huge original-name or metadata fields, since the struct is small; tampered/oversized metadata input to the encryption helper.

Common situations: Uploading an asset whose recorded metadata was extended or crafted to exceed the limit; future format extensions inflating metadata; pathological file names from a modified client.

Understand the failure class

Background: payload too large / request exceeds maximum size: why libraries cap bytes and how to fix oversize payloads — this error's family across 50 libraries.

Related errors

AI-assisted analysis of siyuan-note/siyuan@9f775e8a12 (2026-09-19). Data as JSON: /api/errors/d712f8d0b66cf5fb. Report an issue: GitHub.

Appendix: source

Thrown at kernel/model/crypto.go:2268

	metadata, err := json.Marshal(&encryptedAssetMetadata{
		Spec:         encryptedAssetSpec,
		ContainerID:  containerID,
		OriginalName: originalName,
		Size:         int64(len(plaintext)),
		Chunks:       chunkCount,
	})
	if err != nil {
		return nil, err
	}
	assetKey := util.DeriveSubKey(dek, "siyuan/asset")
	defer zeroAndClear(assetKey)
	aadPrefix := "siyuan:asset:" + boxID + ":assets/" + diskName
	encryptedMetadata, err := util.EncryptWithAAD(assetKey, metadata, []byte(aadPrefix+":metadata"))
	if err != nil {
		return nil, err
	}
	if len(encryptedMetadata) > encryptedAssetMetadataMaxSize {
		return nil, errors.New("encrypted asset metadata is too large")
	}
	ret := bytes.NewBuffer(make([]byte, 0, len(plaintext)+len(encryptedMetadata)+int(chunkCount)*64+12))
	ret.Write(encryptedAssetMagic)
	if err = binary.Write(ret, binary.BigEndian, uint32(len(encryptedMetadata))); err != nil {
		return nil, err
	}
	ret.Write(encryptedMetadata)
	for chunkIndex := uint64(0); chunkIndex < chunkCount; chunkIndex++ {
		start := int(chunkIndex) * encryptedAssetChunkSize
		end := start + encryptedAssetChunkSize
		if end > len(plaintext) {
			end = len(plaintext)
		}
		encryptedChunk, encryptErr := util.EncryptWithAAD(
			assetKey,
			plaintext[start:end],
			encryptedAssetChunkAAD(aadPrefix, containerID, chunkIndex),
		)

View on GitHub (pinned to 9f775e8a12)