Apex Security Guide

Apex Security Guide

Comprehensive guide to Apex security including CRUD/FLS enforcement, sharing rules, SOQL injection prevention, and generation guardrails.

Table of Contents

1. Generation Guardrails
2. CRUD and FLS (Field-Level Security)
3. Sharing and Record Access
4. SOQL Injection Prevention
5. Security Checklist

Generation Guardrails

⛔ MANDATORY PRE-GENERATION CHECKS

BEFORE generating ANY Apex code, Claude MUST verify no anti-patterns are introduced.

If ANY of these patterns would be generated, STOP and ask the user:

"I noticed [pattern]. This will cause [problem]. Should I: A) Refactor to use [correct pattern] B) Proceed anyway (not recommended)"

DO NOT generate anti-patterns even if explicitly requested. Ask user to confirm the exception with documented justification.

Example: Detecting SOQL in Loop

BAD (BLOCKED):

for (Account acc : accounts) {
    List<Contact> contacts = [SELECT Id FROM Contact WHERE AccountId = :acc.Id];
    // Process contacts
}

GOOD (APPROVED):

// Query ONCE before loop
Map<Id, List<Contact>> contactsByAccountId = new Map<Id, List<Contact>>();
for (Contact con : [SELECT Id, AccountId FROM Contact WHERE AccountId IN :accountIds]) {
    if (!contactsByAccountId.containsKey(con.AccountId)) {
        contactsByAccountId.put(con.AccountId, new List<Contact>());
    }
    contactsByAccountId.get(con.AccountId).add(con);
}

// Then loop
for (Account acc : accounts) {
    List<Contact> contacts = contactsByAccountId.get(acc.Id) ?? new List<Contact>();
    // Process contacts
}

CRUD and FLS (Field-Level Security)

API 62.0: WITH USER_MODE

Modern approach (API 62.0+): Use WITH USER_MODE in SOQL to enforce CRUD and FLS automatically.

// ✅ GOOD: Respects user permissions
List<Account> accounts = [
    SELECT Id, Name, Industry, AnnualRevenue
    FROM Account
    WHERE Industry = 'Technology'
    WITH USER_MODE
];

What it does:

• Enforces object-level CRUD (Create, Read, Update, Delete)
• Enforces field-level security (FLS)
• Throws System.QueryException if user lacks access
• Respects user's sharing rules (when combined with with sharing)

When to use SYSTEM_MODE:

// Only use SYSTEM_MODE when you explicitly NEED to bypass security
List<Account> accounts = [
    SELECT Id, Name, Sensitive_Field__c
    FROM Account
    WITH SYSTEM_MODE  // ⚠️ Use with caution!
];

Use cases for SYSTEM_MODE:

• Background jobs that must process all records regardless of user
• System integrations
• Administrative cleanup scripts

ALWAYS document why SYSTEM_MODE is needed:

// JUSTIFICATION: This batch job processes all accounts for regulatory reporting,
// regardless of user's access level. Approved by Security Team on 2025-01-01.

Legacy Approach: Security.stripInaccessible()

For pre-62.0 compatibility or when you need to filter fields dynamically:

// Query all fields
List<Account> accounts = [SELECT Id, Name, Industry, AnnualRevenue FROM Account];

// Strip inaccessible fields
SObjectAccessDecision decision = Security.stripInaccessible(
    AccessType.READABLE,
    accounts
);

// Use stripped records
List<Account> accessibleAccounts = decision.getRecords();

// Check which fields were removed
Set<String> removedFields = decision.getRemovedFields().get('Account');
if (removedFields != null && !removedFields.isEmpty()) {
    System.debug('User lacks access to fields: ' + removedFields);
}

Access Types:

• READABLE - Read access (for queries)
• CREATABLE - Create access (before insert)
• UPDATABLE - Update access (before update)
• UPSERTABLE - Upsert access

Example: Pre-DML Check

public static void createAccounts(List<Account> accounts) {
    // Check if user can create these fields
    SObjectAccessDecision decision = Security.stripInaccessible(
        AccessType.CREATABLE,
        accounts
    );

    if (!decision.getRemovedFields().isEmpty()) {
        throw new SecurityException('User lacks permission to create some fields');
    }

    insert decision.getRecords();
}

Manual CRUD/FLS Checks (Verbose but Explicit)

// Check object-level CRUD
if (!Schema.sObjectType.Account.isAccessible()) {
    throw new SecurityException('User cannot read Accounts');
}

if (!Schema.sObjectType.Account.isCreateable()) {
    throw new SecurityException('User cannot create Accounts');
}

// Check field-level security
if (!Schema.sObjectType.Account.fields.Industry.isAccessible()) {
    throw new SecurityException('User cannot read Industry field');
}

if (!Schema.sObjectType.Account.fields.Industry.isUpdateable()) {
    throw new SecurityException('User cannot update Industry field');
}

When to use: Legacy codebases, specific error messaging, or when you need fine-grained control.

Sharing and Record Access

Sharing Keywords

Default Rule: If no keyword specified, class runs in without sharing mode (pre-API 40 behavior).

ALWAYS specify a sharing keyword - implicit behavior is confusing.

with sharing (Recommended Default)

public with sharing class AccountService {

    public static List<Account> getAccountsForUser() {
        // User only sees Accounts they have access to via sharing rules
        return [SELECT Id, Name FROM Account WITH USER_MODE];
    }

    public static void updateAccount(Account acc) {
        // Throws exception if user lacks access
        update acc;
    }
}

Use cases:

• User-facing controllers (LWC, Aura, Visualforce)
• Service classes handling user requests
• Trigger actions that respect user context

without sharing (Use Sparingly)

public without sharing class AdminService {

    // JUSTIFICATION: This method is only called by system administrators
    // to perform global updates. Access controlled by Custom Permission.
    public static void globalAccountUpdate() {
        List<Account> allAccounts = [SELECT Id, Name FROM Account];
        // Process ALL accounts, ignoring sharing
    }
}

Use cases:

• Background jobs
• System integrations
• Administrative operations

Security Note: Always add access control checks when using without sharing:

public without sharing class AdminService {

    public static void globalUpdate() {
        // Check permission before executing
        if (!FeatureManagement.checkPermission('Admin_Global_Update')) {
            throw new SecurityException('Requires Admin_Global_Update permission');
        }

        // Now safe to proceed with without sharing logic
    }
}

inherited sharing (Best for Utilities)

public inherited sharing class StringUtils {

    // Inherits sharing from calling class
    public static String sanitize(String input) {
        return String.escapeSingleQuotes(input);
    }
}

// Called from "with sharing" class → runs with sharing
// Called from "without sharing" class → runs without sharing

Use cases:

• Utility classes
• Helper methods
• Shared libraries that don't directly query records

Mixing Sharing Contexts

public with sharing class UserFacingService {

    public static void processAccount(Id accountId) {
        // This runs WITH sharing
        Account acc = [SELECT Id, Name FROM Account WHERE Id = :accountId];

        // Call a without sharing method for specific operation
        SystemOperations.performGlobalCheck(acc);
    }
}

public without sharing class SystemOperations {

    public static void performGlobalCheck(Account acc) {
        // This runs WITHOUT sharing
        // Can access records the original user couldn't see
    }
}

Pattern: Start with with sharing, only escalate to without sharing when needed.

SOQL Injection Prevention

The Problem

NEVER concatenate user input into SOQL strings:

// ❌ VULNERABLE to SOQL injection
public static List<Account> searchAccounts(String userInput) {
    String query = 'SELECT Id, Name FROM Account WHERE Name = '' + userInput + ''';
    return Database.query(query);
}

// Attack: userInput = "test' OR '1'='1"
// Results in: SELECT Id, Name FROM Account WHERE Name = 'test' OR '1'='1'
// Returns ALL accounts!

Solution 1: Bind Variables (Recommended)

// ✅ SAFE: Use bind variables
public static List<Account> searchAccounts(String userInput) {
    return [SELECT Id, Name FROM Account WHERE Name = :userInput WITH USER_MODE];
}

// Even with malicious input, it's treated as a literal string

Why it works: Salesforce treats :userInput as a value, not executable SOQL.

Solution 2: String.escapeSingleQuotes()

When dynamic SOQL is unavoidable (rare cases):

// ✅ SAFE: Escape user input
public static List<Account> dynamicSearch(String userInput) {
    String sanitized = String.escapeSingleQuotes(userInput);
    String query = 'SELECT Id, Name FROM Account WHERE Name = '' + sanitized + ''';
    return Database.query(query);
}

What it does: Escapes single quotes (' → ') to prevent breaking out of string literals.

Still prefer bind variables - escapeSingleQuotes is a backup.

Solution 3: Allowlist Validation

For field names, operators, or other dynamic query parts:

public static List<Account> sortedAccounts(String sortField) {
    // ✅ SAFE: Validate against allowlist
    Set<String> allowedFields = new Set<String>{'Name', 'Industry', 'AnnualRevenue'};

    if (!allowedFields.contains(sortField)) {
        throw new IllegalArgumentException('Invalid sort field');
    }

    String query = 'SELECT Id, Name, Industry FROM Account ORDER BY ' + sortField;
    return Database.query(query);
}

Use case: Dynamic ORDER BY, dynamic field selection (but NOT WHERE clause values).

Dynamic SOQL Best Practices

Pattern: Safe Dynamic Query Builder

public class SafeQueryBuilder {

    private static final Set<String> ALLOWED_FIELDS = new Set<String>{
        'Id', 'Name', 'Industry', 'AnnualRevenue'
    };

    private static final Set<String> ALLOWED_OPERATORS = new Set<String>{
        '=', '!=', '<', '>', '<=', '>=', 'LIKE', 'IN'
    };

    public static List<Account> query(
        String field,
        String operator,
        String value
    ) {
        // Validate field
        if (!ALLOWED_FIELDS.contains(field)) {
            throw new IllegalArgumentException('Invalid field: ' + field);
        }

        // Validate operator
        if (!ALLOWED_OPERATORS.contains(operator)) {
            throw new IllegalArgumentException('Invalid operator: ' + operator);
        }

        // Use bind variable for value
        String query = 'SELECT Id, Name FROM Account WHERE ' + field + ' ' + operator + ' :value WITH USER_MODE';
        return Database.query(query);
    }
}

Security Checklist

Use this checklist when generating or reviewing Apex code:

CRUD/FLS

• All SOQL queries use WITH USER_MODE (or Security.stripInaccessible() for pre-62.0)
• DML operations check isCreateable(), isUpdateable(), isDeletable() OR use WITH USER_MODE
• Custom fields have Permission Sets/Profiles granting FLS
• System operations using WITH SYSTEM_MODE are documented with justification

Sharing

• All classes have explicit sharing keyword (with sharing, without sharing, or inherited sharing)
• User-facing classes use with sharing
• without sharing classes have documented justification
• without sharing classes include Custom Permission checks

SOQL Injection

• No string concatenation in WHERE clauses with user input
• All user input uses bind variables (:variableName)
• Dynamic SOQL uses allowlist validation for field names/operators
• String.escapeSingleQuotes() used if concatenation is unavoidable

General Security

• No hardcoded credentials or API keys (use Named Credentials)
• No hardcoded Record IDs (use Custom Metadata or queries)
• Sensitive data (SSN, PII) is encrypted at rest (Platform Encryption)
• External callouts use Named Credentials, not plain URLs
• Error messages don't leak sensitive information

Advanced Security Patterns

Custom Permissions

Check user has specific permission before dangerous operations:

public without sharing class DataDeletionService {

    public static void deleteAllTestData() {
        // Check Custom Permission
        if (!FeatureManagement.checkPermission('Delete_Test_Data')) {
            throw new SecurityException('Requires Delete_Test_Data permission');
        }

        // Safe to proceed
        delete [SELECT Id FROM Account WHERE Name LIKE 'TEST%'];
    }
}

Create Custom Permission: Setup → Custom Permissions → New

Secure Remote Actions (@AuraEnabled)

public with sharing class AccountController {

    @AuraEnabled(cacheable=true)
    public static List<Account> getAccounts() {
        // Runs with sharing + user mode = secure
        return [SELECT Id, Name FROM Account WITH USER_MODE LIMIT 50];
    }

    @AuraEnabled
    public static void updateAccount(Account acc) {
        // Verify user can update
        if (!Schema.sObjectType.Account.isUpdateable()) {
            throw new AuraHandledException('No update permission');
        }

        update acc;
    }
}

Security Notes:

• Always use with sharing for @AuraEnabled methods
• Use WITH USER_MODE in SOQL
• Validate DML permissions before operations
• Use AuraHandledException for friendly error messages

Platform Events Security

public with sharing class EventPublisher {

    public static void publishEvent(String message) {
        // Check if user can create Platform Events
        if (!Schema.sObjectType.MyEvent__e.isCreateable()) {
            throw new SecurityException('Cannot publish events');
        }

        MyEvent__e event = new MyEvent__e(
            Message__c = message
        );

        EventBus.publish(event);
    }
}

Common Security Vulnerabilities

Testing Security

Test User Mode

@IsTest
static void testUserModeEnforcesPermissions() {
    // Create user without Account read access
    User restrictedUser = createRestrictedUser();

    System.runAs(restrictedUser) {
        try {
            List<Account> accounts = [SELECT Id FROM Account WITH USER_MODE];
            Assert.fail('Expected QueryException for user without access');
        } catch (System.QueryException e) {
            Assert.isTrue(e.getMessage().contains('Insufficient privileges'));
        }
    }
}

Test Sharing Rules

@IsTest
static void testSharingEnforcement() {
    Account acc = new Account(Name = 'Test Account', OwnerId = UserInfo.getUserId());
    insert acc;

    // Create user who is NOT the owner
    User otherUser = createStandardUser();

    System.runAs(otherUser) {
        // Should NOT see account owned by different user
        List<Account> visible = [SELECT Id FROM Account WHERE Id = :acc.Id];
        Assert.areEqual(0, visible.size(), 'User should not see account due to sharing rules');
    }
}

Reference

Full Documentation: See references/ folder for comprehensive guides:

• security-guide.md - Complete security reference (this is an extract)
• best-practices.md - Includes security best practices
• code-review-checklist.md - Security scoring criteria

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