23. SQL Injection Prevention with Proper Escaping

Date: 2025-11-14
Status: Accepted
Deciders: Engineering Team
Technical Story: Architecture Refactoring - Security Fix (November 14, 2025)

Sources: - Planning: 2025-11-14-architecture-refactoring

Context and Problem Statement

During architecture review, SQL injection vulnerability discovered in concept search WHERE clauses [Security Issue: 01-architecture-review-analysis.md, SQL injection section]. User input was directly interpolated into SQL queries without proper escaping [Problem: string concatenation in WHERE clauses].

Vulnerable Code Example: [Source: Pre-refactoring concept_search.ts]

// VULNERABLE: Direct string interpolation
const results = await conceptTable
  .query()
  .where(`concept = '${conceptLower}'`)  // SQL INJECTION!
  .toArray();

Attack Vector: User could search for: ' OR '1'='1 to return all concepts

The Core Problem: How to safely include user input in SQL WHERE clauses used by LanceDB queries? [Security: input validation]

Decision Drivers: * CRITICAL: Security vulnerability must be fixed [Priority: security] * LanceDB uses SQL-like WHERE syntax [Context: database API] * User input in search queries [Risk: untrusted input] * No parameterized queries available in LanceDB open-source [Limitation: API constraint] [Source: 10-parameterized-sql-investigation.md] * Need comprehensive solution for all queries [Requirement: system-wide]

Alternative Options

• Option 1: Manual SQL Escaping with Tests - Escape single quotes, validate
• Option 2: Parameterized Queries - Prepared statements (if available)
• Option 3: Input Validation Only - Whitelist/regex validation
• Option 4: ORM/Query Builder - Use library for query construction
• Option 5: No Special Characters - Reject queries with special chars

Decision Outcome

Chosen option: "Manual SQL Escaping with Comprehensive Tests (Option 1)", because LanceDB open-source doesn't support parameterized queries [Source: 10-parameterized-sql-investigation.md, investigation result], and proper escaping with thorough testing provides robust protection.

Implementation

Utility Function: [Source: Implementation in field parsers]

/**
 * Escape single quotes in SQL strings to prevent SQL injection.
 * LanceDB uses SQL WHERE clauses, so we must escape user input.
 * 
 * @param value - User input to escape
 * @returns Escaped string safe for SQL WHERE clause
 */
export function escapeSql(value: string): string {
  // Replace single quote (') with two single quotes ('')
  // Standard SQL escaping mechanism
  return value.replace(/'/g, "''");
}

Usage in Repositories:

// SAFE: Escaped user input
const escapedName = escapeSql(conceptName);
const results = await conceptTable
  .query()
  .where(`concept = '${escapedName}'`)
  .toArray();

Test Coverage: [Source: PR-DESCRIPTION.md, line 48; test files] - 14 unit tests: Comprehensive SQL injection prevention tests [Source: field-parsers.test.ts] - Attack vectors tested: ' OR '1'='1, '; DROP TABLE--, \\', etc. - Edge cases: Empty string, Unicode, very long strings

Consequences

Positive: * Security vulnerability fixed: SQL injection prevented [Result: PR-DESCRIPTION.md, lines 47-49] * 14 tests verify protection: Comprehensive test coverage [Validation: PR-DESCRIPTION.md, line 48] * System-wide: Applied to all user-facing queries [Scope: complete coverage] * Standard approach: SQL escaping is industry-standard technique [Pattern: established] * No dependencies: Pure JavaScript solution [Simplicity: no libraries] * Auditable: Simple escapeSQL function easy to review [Security: transparency]

Negative: * Manual escaping required: Must remember to call escapeSql() [Risk: human error] * No compile-time enforcement: TypeScript can't enforce escaping [Limitation: runtime] * Not parameterized queries: Less elegant than prepared statements [Trade-off: API limitation] * Developer discipline: Relies on code review to catch misses [Process: review required]

Neutral: * Single quote escaping: Standard SQL technique (replace ' with '') [Approach: conventional] * WHERE clause only: LanceDB doesn't support parameters [Context: API constraint]

Confirmation

Security Testing: [Source: Test coverage] - 14 unit tests: All passing, all attack vectors blocked - Attack patterns tested: - ' OR '1'='1 - Always-true condition - '; DROP TABLE-- - SQL injection with comment - \\' OR \\ - Escape sequence attacks - Multiple quotes, Unicode, empty strings

Code Review: - All WHERE clauses audited - All user input properly escaped - No vulnerable queries remain

Production Validation: - No SQL injection incidents reported - All queries working correctly with escaping

Pros and Cons of the Options

Option 1: Manual SQL Escaping with Tests - Chosen

Pros: * Works with LanceDB API * 14 comprehensive tests [Validated] * Industry-standard approach * Simple and auditable * No dependencies * Security vulnerability fixed [Result]

Cons: * Manual escaping (must remember) * No compile-time enforcement * Developer discipline required * Less elegant than parameters

Option 2: Parameterized Queries

Use prepared statements/parameterized queries.

Pros: * Best security practice * Compile-time safe * No escaping needed * Most elegant solution

Cons: * Not available in LanceDB open-source [Dealbreaker: API limitation] [Source: 10-parameterized-sql-investigation.md] * Only in Enterprise: FlightSQL protocol (enterprise edition only) [Limitation: cost] * Investigation result: Parameterized queries not feasible for open-source [Decision: rejected]

Option 3: Input Validation Only

Whitelist characters, reject special chars.

Pros: * Can prevent some attacks * Simple validation

Cons: * Breaks legitimate searches: User can't search for "O'Reilly books" [Problem: apostrophes legitimate] * Incomplete protection: Validation != escaping [Security: insufficient] * User frustration: "Why can't I search for X?" [UX: confusing] * Not sufficient: Need escaping, not rejection

Option 4: ORM/Query Builder

Use TypeORM, Prisma, or similar.

Pros: * Automatic escaping * Query builder syntax * Type-safe queries

Cons: * LanceDB not supported: ORMs don't support LanceDB [Incompatibility: no integration] * Heavy dependency: Large framework [Overhead: unnecessary] * Over-engineering: Just need escaping [Complexity: overkill] * Not applicable: LanceDB has custom query API

Option 5: No Special Characters

Reject queries containing ', ", ;, etc.

Pros: * Eliminates attack surface * Simple to implement

Cons: * Breaks legitimate use: Many valid searches contain apostrophes [Problem: "it's", "O'Reilly"] * Poor UX: Confusing error messages [UX: frustration] * Not real fix: Hiding problem, not solving it [Philosophy: wrong approach] * Escaping better: Handle special chars correctly, don't reject them

Implementation Notes

LanceDB Query Syntax

LanceDB WHERE Clause: [Context: SQL-like syntax]

await table
  .query()
  .where(`field = 'value'`)  // SQL-like WHERE clause
  .toArray();

Constraint: No parameterized query support in open-source [Source: 10-parameterized-sql-investigation.md]

Escaping Implementation

Standard SQL Technique: - Single quote (') is string delimiter in SQL - Escape by doubling: ' → '' - Standard across SQL databases (PostgreSQL, MySQL, SQLite, etc.)

JavaScript Implementation:

export function escapeSql(value: string): string {
  return value.replace(/'/g, "''");  // Replace ' with ''
}

16 characters: Simplest possible implementation

Test Coverage

Attack Patterns Tested: [Source: field-parsers.test.ts]

describe('escapeSql', () => {
  it('should escape basic SQL injection', () => {
    expect(escapeSql("' OR '1'='1")).toBe("'' OR ''1''=''1");
  });

  it('should escape DROP TABLE attack', () => {
    expect(escapeSql("'; DROP TABLE--")).toBe("''; DROP TABLE--");
  });

  it('should handle multiple quotes', () => {
    expect(escapeSql("O'Reilly's book")).toBe("O''Reilly''s book");
  });

  // ... 11 more tests
});

System-Wide Application

All Repositories: [Application: consistent usage] - ChunkRepository - User queries escaped - ConceptRepository - Concept names escaped - CatalogRepository - Source filters escaped

Code Review: All WHERE clauses audited for proper escaping

Alternative Investigated

Parameterized Queries: [Source: 10-parameterized-sql-investigation.md] - Investigated October/November 2025 - Conclusion: "Not available in open-source LanceDB" - Recommendation: "Keep current implementation (manual escaping)" - FlightSQL protocol (enterprise) supports parameters, but not accessible

Related Decisions

• ADR-0002: LanceDB - Database API constraints
• ADR-0017: Repository Pattern - Escaping in repositories
• ADR-0019: Vitest - Security tests

References

Related Decisions

• ADR-0002: LanceDB
• ADR-0017: Repository Pattern

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Confidence Level: HIGH Attribution: - Planning docs: November 14, 2024 - Security fix documented: PR-DESCRIPTION.md lines 47-49 - Investigation: 10-parameterized-sql-investigation.md

Traceability: 2025-11-14-architecture-refactoring