Documentation
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Overview ¶
Package validation provides MCP message validation logic.
Package validation provides MCP message validation logic. It validates JSON-RPC structure and MCP-specific requirements to reject malformed messages early in the proxy chain.
Index ¶
Constants ¶
const ( // MaxStringLength is the maximum length of any string value (1MB). // Strings longer than this are truncated to prevent memory exhaustion. MaxStringLength = 1048576 // MaxToolNameLength is the maximum length of a tool name. MaxToolNameLength = 255 )
Size limits for sanitization.
const ( // ErrCodeParseError indicates invalid JSON was received. ErrCodeParseError = -32700 // ErrCodeInvalidRequest indicates the JSON is not a valid Request object. ErrCodeInvalidRequest = -32600 // ErrCodeMethodNotFound indicates the method does not exist or is not available. ErrCodeMethodNotFound = -32601 // ErrCodeInvalidParams indicates invalid method parameters. ErrCodeInvalidParams = -32602 // ErrCodeInternalError indicates an internal JSON-RPC error. ErrCodeInternalError = -32603 )
JSON-RPC 2.0 standard error codes. These are defined in the JSON-RPC 2.0 specification: https://www.jsonrpc.org/specification#error_object
Variables ¶
var ValidMCPMethods = map[string]bool{ "initialize": true, "initialized": true, "notifications/initialized": true, "ping": true, "tools/list": true, "tools/call": true, "resources/list": true, "resources/read": true, "prompts/list": true, "prompts/get": true, "completion/complete": true, "logging/setLevel": true, "notifications/cancelled": true, "notifications/progress": true, "notifications/message": true, "notifications/resources/updated": true, "notifications/resources/list_changed": true, "notifications/tools/list_changed": true, "notifications/prompts/list_changed": true, "sampling/createMessage": true, "roots/list": true, "notifications/roots/list_changed": true, }
ValidMCPMethods contains all valid MCP 2025-11-25 method names. This is a whitelist of methods that are allowed through the proxy. Unknown methods are rejected with ErrCodeMethodNotFound.
Reference: https://modelcontextprotocol.io/specification/2025-11-25
Functions ¶
func IsValidMCPMethod ¶
IsValidMCPMethod returns true if the method is a valid MCP method. MCP method names are case-sensitive.
Types ¶
type MessageValidator ¶
type MessageValidator struct{}
MessageValidator validates MCP messages for JSON-RPC compliance and MCP-specific requirements.
func NewMessageValidator ¶
func NewMessageValidator() *MessageValidator
NewMessageValidator creates a new MessageValidator.
func (*MessageValidator) Validate ¶
func (v *MessageValidator) Validate(msg *mcp.Message) error
Validate checks if the message is a valid JSON-RPC/MCP message. Returns nil if valid, or a *ValidationError if invalid.
Validation rules: - Message must have a non-nil Decoded field (parse error if nil) - Requests must have non-nil ID and non-empty Method - Request Method must be a valid MCP method - Notifications (Request with nil ID) must have non-empty Method - Responses must have ID and either Result or Error (not both, not neither)
type Sanitizer ¶
type Sanitizer struct {
}
Sanitizer provides input sanitization for tool call arguments. It validates tool names and recursively sanitizes string values to prevent injection attacks and policy bypass attempts.
func (*Sanitizer) SanitizeToolCall ¶
SanitizeToolCall sanitizes tool call parameters. It validates the tool name and sanitizes all argument values.
Expected params structure:
{
"name": "tool_name",
"arguments": { ... }
}
Returns sanitized params with validated name and sanitized arguments.
func (*Sanitizer) SanitizeValue ¶
SanitizeValue recursively sanitizes a value. For strings, it removes null bytes and truncates at MaxStringLength. For maps and slices, it recurses into each element. For other types (numbers, booleans, nil), it returns them unchanged.
func (*Sanitizer) ValidateToolName ¶
ValidateToolName validates a tool name against injection patterns. It returns a ValidationError if the name is invalid.
Valid tool names:
- Start with a letter
- Contain only alphanumeric characters, underscores, and hyphens
- Are at most MaxToolNameLength characters
- Do not contain path traversal sequences
type ValidationError ¶
type ValidationError struct {
// Code is the JSON-RPC error code.
Code int
// Message is a safe, client-facing error message.
// This MUST NOT contain internal details like file paths or stack traces.
Message string
}
ValidationError represents a validation failure with a JSON-RPC error code. The Message field contains a safe message for the client (no internal details).
func NewValidationError ¶
func NewValidationError(code int, message string) *ValidationError
NewValidationError creates a new ValidationError with the given code and message.
func (*ValidationError) Error ¶
func (e *ValidationError) Error() string
Error implements the error interface.
Source Files