sipeed/picoclaw · error

invalid padding byte

Error message

invalid padding byte

What it means

Error "invalid padding byte" thrown in sipeed/picoclaw.

Source

Thrown at pkg/channels/wecom/media.go:131

		return nil, fmt.Errorf("create cipher: %w", err)
	}
	plaintext := make([]byte, len(ciphertext))
	iv := key[:aes.BlockSize]
	cipher.NewCBCDecrypter(block, iv).CryptBlocks(plaintext, ciphertext)
	return pkcs7Unpad(plaintext)
}

func pkcs7Unpad(data []byte) ([]byte, error) {
	if len(data) == 0 {
		return nil, fmt.Errorf("empty plaintext")
	}
	padding := int(data[len(data)-1])
	if padding == 0 || padding > 32 || padding > len(data) {
		return nil, fmt.Errorf("invalid padding size %d", padding)
	}
	for i := 0; i < padding; i++ {
		if data[len(data)-1-i] != byte(padding) {
			return nil, fmt.Errorf("invalid padding byte")
		}
	}
	return data[:len(data)-padding], nil
}

func inferMediaExt(contentType, fallback string) string {
	contentType = normalizeWeComContentType(contentType)
	switch contentType {
	case "image/jpeg", "image/jpg":
		return ".jpg"
	case "image/png":
		return ".png"
	case "image/gif":
		return ".gif"
	case "image/webp":
		return ".webp"
	case "application/pdf":
		return ".pdf"

View on GitHub (pinned to 49183d7e8d)

When it happens

Trigger: Thrown at pkg/channels/wecom/media.go:131 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of sipeed/picoclaw@49183d7e8d (2026-08-15). Data as JSON: /api/errors/8249053344ff8b37. Report an issue: GitHub.