Function validate_readonly_query

src/environmentd/src/http/mcp.rs:1175–1217

Validates query is a single SELECT, SHOW, or EXPLAIN statement.

(sql: &str)

/// Validates query is a single SELECT, SHOW, or EXPLAIN statement.
fn validate_readonly_query(sql: &str) -> Result<(), McpRequestError> {
    let sql = sql.trim();
    if sql.is_empty() {
        return Err(McpRequestError::QueryValidationFailed(
            "Empty query".to_string(),
        ));
    }

    // Parse the SQL to get AST
    let stmts = parse(sql).map_err(|e| {
        McpRequestError::QueryValidationFailed(format!("Failed to parse SQL: {}", e))
    })?;

    // Only allow a single statement
    if stmts.len() != 1 {
        return Err(McpRequestError::QueryValidationFailed(format!(
            "Only one query allowed at a time. Found {} statements.",
            stmts.len()
        )));
    }

    // Allowlist: SELECT, SHOW, and every read-only EXPLAIN variant. EXPLAIN
    // expands to six distinct Statement variants in the parser (ExplainPlan
    // covers only the most common one). Listing them out exhaustively beats
    // matching by string prefix so a new write-capable EXPLAIN variant — were
    // one ever added — would have to be considered here.
    let stmt = &stmts[0];
    use mz_sql_parser::ast::Statement;

    match &stmt.ast {
        Statement::Select(_)
        | Statement::Show(_)
        | Statement::ExplainPlan(_)
        | Statement::ExplainPushdown(_)
        | Statement::ExplainTimestamp(_)
        | Statement::ExplainSinkSchema(_)
        | Statement::ExplainAnalyzeObject(_)
        | Statement::ExplainAnalyzeCluster(_) => Ok(()),
        _ => Err(McpRequestError::QueryValidationFailed(
            "Only SELECT, SHOW, and EXPLAIN statements are allowed".to_string(),
        )),
    }
}

async fn execute_query(
    client: &mut AuthedClient,