319 lines
9.1 KiB
Go
319 lines
9.1 KiB
Go
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// Copyright 2021 Ross Light
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// SPDX-License-Identifier: ISC
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package sqlite
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import (
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"fmt"
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"strings"
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"sync"
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"unsafe"
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"modernc.org/libc"
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lib "modernc.org/sqlite/lib"
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)
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// An Authorizer is called during statement preparation to see whether an action
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// is allowed by the application. An Authorizer must not modify the database
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// connection, including by preparing statements.
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//
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// See https://sqlite.org/c3ref/set_authorizer.html for a longer explanation.
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type Authorizer interface {
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Authorize(Action) AuthResult
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}
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// SetAuthorizer registers an authorizer for the database connection.
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// SetAuthorizer(nil) clears any authorizer previously set.
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func (c *Conn) SetAuthorizer(auth Authorizer) error {
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if c == nil {
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return fmt.Errorf("sqlite: set authorizer: nil connection")
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}
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if auth == nil {
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c.releaseAuthorizer()
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res := ResultCode(lib.Xsqlite3_set_authorizer(c.tls, c.conn, 0, 0))
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if err := reserr(res); err != nil {
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return fmt.Errorf("sqlite: set authorizer: %w", err)
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}
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return nil
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}
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authorizers.mu.Lock()
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if authorizers.m == nil {
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authorizers.m = make(map[uintptr]Authorizer)
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}
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authorizers.m[c.conn] = auth
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authorizers.mu.Unlock()
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// The following is a conversion from function value to uintptr. It assumes
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// the memory representation described in https://golang.org/s/go11func.
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//
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// It does this by doing the following in order:
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// 1) Create a Go struct containing a pointer to a pointer to
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// authTrampoline. It is assumed that the pointer to authTrampoline will be
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// stored in the read-only data section and thus will not move.
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// 2) Convert the pointer to the Go struct to a pointer to uintptr through
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// unsafe.Pointer. This is permitted via Rule #1 of unsafe.Pointer.
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// 3) Dereference the pointer to uintptr to obtain the function value as a
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// uintptr. This is safe as long as function values are passed as pointers.
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xAuth := *(*uintptr)(unsafe.Pointer(&struct {
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f func(*libc.TLS, uintptr, int32, uintptr, uintptr, uintptr, uintptr) int32
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}{authTrampoline}))
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res := ResultCode(lib.Xsqlite3_set_authorizer(c.tls, c.conn, xAuth, c.conn))
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if err := reserr(res); err != nil {
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return fmt.Errorf("sqlite: set authorizer: %w", err)
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}
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return nil
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}
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func (c *Conn) releaseAuthorizer() {
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authorizers.mu.Lock()
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delete(authorizers.m, c.conn)
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authorizers.mu.Unlock()
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}
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var authorizers struct {
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mu sync.RWMutex
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m map[uintptr]Authorizer // sqlite3* -> Authorizer
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}
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func authTrampoline(tls *libc.TLS, conn uintptr, op int32, cArg1, cArg2, cDB, cTrigger uintptr) int32 {
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authorizers.mu.RLock()
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auth := authorizers.m[conn]
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authorizers.mu.RUnlock()
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return int32(auth.Authorize(Action{
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op: OpType(op),
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arg1: libc.GoString(cArg1),
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arg2: libc.GoString(cArg2),
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database: libc.GoString(cDB),
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trigger: libc.GoString(cTrigger),
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}))
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}
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// AuthorizeFunc is a function that implements Authorizer.
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type AuthorizeFunc func(Action) AuthResult
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// Authorize calls f.
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func (f AuthorizeFunc) Authorize(action Action) AuthResult {
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return f(action)
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}
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// AuthResult is the result of a call to an Authorizer. The zero value is
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// AuthResultOK.
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type AuthResult int32
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// Possible return values from Authorize.
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const (
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// AuthResultOK allows the SQL statement to be compiled.
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AuthResultOK AuthResult = lib.SQLITE_OK
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// AuthResultDeny causes the entire SQL statement to be rejected with an error.
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AuthResultDeny AuthResult = lib.SQLITE_DENY
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// AuthResultIgnore disallows the specific action but allow the SQL statement
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// to continue to be compiled. For OpRead, this substitutes a NULL for the
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// column value. For OpDelete, the DELETE operation proceeds but the truncate
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// optimization is disabled and all rows are deleted individually.
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AuthResultIgnore AuthResult = lib.SQLITE_IGNORE
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)
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// String returns the C constant name of the result.
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func (result AuthResult) String() string {
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switch result {
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case AuthResultOK:
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return "SQLITE_OK"
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case AuthResultDeny:
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return "SQLITE_DENY"
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case AuthResultIgnore:
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return "SQLITE_IGNORE"
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default:
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return fmt.Sprintf("AuthResult(%d)", int32(result))
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}
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}
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// Action represents an action to be authorized.
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type Action struct {
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op OpType
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arg1 string
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arg2 string
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database string
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trigger string
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}
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// Mapping of argument position to concept at:
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// https://sqlite.org/c3ref/c_alter_table.html
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// Type returns the type of action being authorized.
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func (action Action) Type() OpType {
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return action.op
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}
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// Accessor returns the name of the inner-most trigger or view that is
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// responsible for the access attempt or the empty string if this access attempt
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// is directly from top-level SQL code.
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func (action Action) Accessor() string {
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return action.trigger
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}
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// Database returns the name of the database (e.g. "main", "temp", etc.) this
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// action affects or the empty string if not applicable.
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func (action Action) Database() string {
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switch action.op {
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case OpDetach, OpAlterTable:
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return action.arg1
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default:
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return action.database
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}
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}
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// Index returns the name of the index this action affects or the empty string
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// if not applicable.
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func (action Action) Index() string {
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switch action.op {
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case OpCreateIndex, OpCreateTempIndex, OpDropIndex, OpDropTempIndex, OpReindex:
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return action.arg1
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default:
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return ""
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}
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}
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// Table returns the name of the table this action affects or the empty string
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// if not applicable.
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func (action Action) Table() string {
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switch action.op {
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case OpCreateTable, OpCreateTempTable, OpDelete, OpDropTable, OpDropTempTable, OpInsert, OpRead, OpUpdate, OpAnalyze, OpCreateVTable, OpDropVTable:
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return action.arg1
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case OpCreateIndex, OpCreateTempIndex, OpCreateTempTrigger, OpCreateTrigger, OpDropIndex, OpDropTempIndex, OpDropTempTrigger, OpDropTrigger, OpAlterTable:
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return action.arg2
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default:
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return ""
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}
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}
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// Trigger returns the name of the trigger this action affects or the empty
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// string if not applicable.
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func (action Action) Trigger() string {
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switch action.op {
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case OpCreateTempTrigger, OpCreateTrigger, OpDropTempTrigger, OpDropTrigger:
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return action.arg1
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default:
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return ""
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}
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}
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// View returns the name of the view this action affects or the empty string
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// if not applicable.
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func (action Action) View() string {
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switch action.op {
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case OpCreateTempView, OpCreateView, OpDropTempView, OpDropView:
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return action.arg1
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default:
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return ""
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}
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}
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// Pragma returns the name of the action's PRAGMA command or the empty string
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// if the action does not represent a PRAGMA command.
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// See https://sqlite.org/pragma.html#toc for a list of possible values.
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func (action Action) Pragma() string {
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if action.op != OpPragma {
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return ""
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}
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return action.arg1
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}
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// PragmaArg returns the argument to the PRAGMA command or the empty string if
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// the action does not represent a PRAGMA command or the PRAGMA command does not
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// take an argument.
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func (action Action) PragmaArg() string {
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if action.op != OpPragma {
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return ""
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}
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return action.arg2
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}
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// Column returns the name of the column this action affects or the empty string
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// if not applicable. For OpRead actions, this will return the empty string if a
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// table is referenced but no column values are extracted from that table
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// (e.g. a query like "SELECT COUNT(*) FROM tab").
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func (action Action) Column() string {
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switch action.op {
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case OpRead, OpUpdate:
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return action.arg2
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default:
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return ""
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}
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}
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// Operation returns one of "BEGIN", "COMMIT", "RELEASE", or "ROLLBACK" for a
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// transaction or savepoint statement or the empty string otherwise.
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func (action Action) Operation() string {
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switch action.op {
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case OpTransaction, OpSavepoint:
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return action.arg1
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default:
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return ""
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}
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}
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// File returns the name of the file being ATTACHed or the empty string if the
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// action does not represent an ATTACH DATABASE statement.
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func (action Action) File() string {
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if action.op != OpAttach {
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return ""
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}
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return action.arg1
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}
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// Module returns the module name given to the virtual table statement or the
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// empty string if the action does not represent a CREATE VIRTUAL TABLE or
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// DROP VIRTUAL TABLE statement.
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func (action Action) Module() string {
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switch action.op {
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case OpCreateVTable, OpDropVTable:
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return action.arg2
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default:
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return ""
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}
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}
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// Savepoint returns the name given to the SAVEPOINT statement or the empty
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// string if the action does not represent a SAVEPOINT statement.
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func (action Action) Savepoint() string {
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if action.op != OpSavepoint {
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return ""
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}
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return action.arg2
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}
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// String returns a debugging representation of the action.
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func (action Action) String() string {
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sb := new(strings.Builder)
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sb.WriteString(action.op.String())
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params := []struct {
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name, value string
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}{
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{"database", action.Database()},
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{"file", action.File()},
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{"trigger", action.Trigger()},
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{"index", action.Index()},
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{"table", action.Table()},
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{"view", action.View()},
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{"module", action.Module()},
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{"column", action.Column()},
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{"operation", action.Operation()},
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{"savepoint", action.Savepoint()},
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{"pragma", action.Pragma()},
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{"arg", action.PragmaArg()},
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}
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for _, p := range params {
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if p.value != "" {
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sb.WriteString(" ")
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sb.WriteString(p.name)
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sb.WriteString(":")
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sb.WriteString(p.value)
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}
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}
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return sb.String()
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}
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