detecting-sql-injection-patterns

Testing & Quality

Scan a source tree for SQL-injection vulnerable patterns: string concatenation into queries, f-string interpolation in SQL, string-format substitution into raw queries, deprecated cursor methods (cursor.execute with % formatting), Knex / Sequelize raw() with template interpolation, sequelize.query with replacements. Use when: pre-commit code review, post-feature SQL-touching release, inheriting a legacy codebase that predates ORMs, or post-bug-report investigation. Threshold: any source line where SQL keywords (SELECT / INSERT / UPDATE / DELETE / FROM / WHERE) appear in a string that's being built via concatenation, f-string, %-format, or .format() with variable input. Trigger with: "scan for sqli", "sql injection patterns", "check raw queries", "audit cursor.execute".

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Detecting SQL Injection Patterns

Overview

SQL injection (CWE-89, OWASP A03:2021) remains one of the highest- impact and most-easily-introduced vulnerability classes. The fix is near-universal: use parameterized queries. The cause when introduced: an engineer concatenates user input into a SQL string because the ORM's parameterization mechanism wasn't obvious, or because they "just need to add a quick condition."

The scanner reads source files and grades each apparent SQL-string construction against the threshold table.

When the skill produces findings

Finding	Severity	Threshold	Affected control
f-string with SQL keywords + user input	CRITICAL	`f"SELECT * FROM users WHERE id = {user_id}"`	CWE-89
String concat into SQL keyword string	CRITICAL	`"SELECT ... " + var + " ..."`	CWE-89
%-format SQL string	HIGH	`"SELECT * FROM %s" % table_name`	CWE-89
`.format()` into SQL string	HIGH	`"SELECT {} FROM users".format(col)`	CWE-89
`cursor.execute(f"...")`	CRITICAL	f-string passed directly to cursor.execute	CWE-89
`sequelize.query` with template literal	HIGH	`sequelize.query(\`SELECT * FROM ${table}`)`	CWE-89
Knex / sequelize raw() with interpolation	HIGH	`knex.raw('SELECT * FROM ' + table)`	CWE-89
Django `.extra()` with raw SQL	MEDIUM	`Model.objects.extra(where=['col = ' + val])`	CWE-89
`cursor.executemany` with string-built query	CRITICAL	Same risk as execute	CWE-89
JDBC `Statement.execute` with concat	HIGH	Java pattern: not PreparedStatement	CWE-89
Rails `where()` with string interpolation	HIGH	`User.where("name = '#{name}'")`	CWE-89
Go `db.Query` with `fmt.Sprintf`	HIGH	`db.Query(fmt.Sprintf("...", arg))`	CWE-89

Prerequisites

Python 3.9+
Target source tree on local filesystem

Instructions

Step 1 — Run the scanner

python3 ${CLAUDE_PLUGIN_ROOT}/skills/detecting-sql-injection-patterns/scripts/scan_sqli.py /path/to/repo

Options:

Usage: scan_sqli.py PATH [OPTIONS]

Options:
  --output FILE      Write findings to FILE
  --format FMT       json | jsonl | markdown (default: markdown)
  --min-severity SEV (default: info)
  --include-tests    Include test directories (default: excluded)
  --languages LIST   Comma-separated: python,javascript,typescript,java,
                     ruby,go,php,csharp (default: all)

Step 2 — Interpret findings

CRITICAL = direct user-input → query string construction. Fix the specific query AND audit nearby code for the same pattern.

HIGH = pattern suggests interpolation but might be a fixed identifier (table/column name). Verify by reading the code.

MEDIUM = framework-specific pattern that's safe ONLY with strict input validation (Django .extra(), Rails string where()).

Step 3 — Remediation

For each finding, the fix is the same shape per language: use the language/library's parameterized-query API. See references/PLAYBOOK.md for per-language snippets.

Step 4 — Cross-skill chaining

Consider running scanning-for-hardcoded-secrets (#10) on the same target — same audit, different class of finding.

Examples

Example 1 — Pre-merge code review

python3 ${CLAUDE_PLUGIN_ROOT}/skills/detecting-sql-injection-patterns/scripts/scan_sqli.py \
    --min-severity high $(git diff --name-only main...HEAD | tr '\n' ' ')

Scans only files changed in the current branch — fast feedback for PR review.

Example 2 — Legacy codebase audit

python3 ${CLAUDE_PLUGIN_ROOT}/skills/detecting-sql-injection-patterns/scripts/scan_sqli.py \
    /path/to/legacy-app --format markdown > sqli-audit.md

Expect dozens to hundreds of findings on a pre-ORM Java/PHP codebase. Prioritize by reachability: the queries reached from public endpoints first.

Output

JSON / JSONL / Markdown. Exit codes: 0 clean, 1 high/critical, 2 error.

Error Handling

False positives on fixed-identifier interpolation (e.g., f"SELECT * FROM {tablename}" where tablename is hardcoded) → verify manually. The scanner can't reason about variable provenance without a full AST + control-flow pass.
String-built dynamic-table queries are sometimes legitimate (multi-tenant routing). Flag and review; the fix is usually allow-list validation + identifier quoting.

Resources

references/THEORY.md — Per-language interpolation patterns, ORM-specific safe vs unsafe APIs, why prepared statements work
references/PLAYBOOK.md — Per-language parameterization snippets (Python sqlite3 + psycopg + SQLAlchemy, Node mysql2 + pg + knex
- sequelize, Ruby ActiveRecord, Go database/sql, Java JDBC PreparedStatement, PHP PDO)