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import itertools
import re
from dataclasses import replace
from typing import Any, ClassVar, Collection, Optional
import libcst as cst
from libcst.codemod import Codemod, CodemodContext, ContextAwareVisitor
from libcst.codemod.commands.unnecessary_format_string import UnnecessaryFormatString
from libcst.metadata import (
ClassScope,
GlobalScope,
ParentNodeProvider,
PositionProvider,
ProviderT,
ScopeProvider,
)
from codemodder.codemods.base_visitor import UtilsMixin
from codemodder.codemods.libcst_transformer import (
LibcstResultTransformer,
LibcstTransformerPipeline,
)
from codemodder.codemods.transformations.remove_empty_string_concatenation import (
RemoveEmptyStringConcatenation,
)
from codemodder.codemods.utils import (
Append,
ReplacementNodeType,
ReplaceNodes,
get_function_name_node,
infer_expression_type,
)
from codemodder.codemods.utils_mixin import NameAndAncestorResolutionMixin
from codemodder.utils.clean_code import (
NormalizeFStrings,
RemoveEmptyExpressionsFormatting,
RemoveUnusedVariables,
)
from codemodder.utils.format_string_parser import (
PrintfStringExpression,
PrintfStringText,
StringLiteralNodeType,
extract_raw_value,
)
from codemodder.utils.linearize_string_expression import (
LinearizedStringExpression,
LinearizeStringMixin,
)
from core_codemods.api import Metadata, Reference, ReviewGuidance
from core_codemods.api.core_codemod import CoreCodemod
parameter_token = "?"
quote_pattern = re.compile(r"(?<!\\)\\'|(?<!\\)'")
raw_quote_pattern = re.compile(r"(?<!\\)'")
class ExtractPrefixMixin(cst.MetadataDependent):
METADATA_DEPENDENCIES: ClassVar[Collection[ProviderT]] = (ParentNodeProvider,)
def extract_prefix(self, node: StringLiteralNodeType) -> str:
match node:
case cst.SimpleString():
return node.prefix.lower()
case cst.FormattedStringText():
try:
parent = self.get_metadata(ParentNodeProvider, node)
parent = cst.ensure_type(parent, cst.FormattedString)
except Exception:
return ""
return parent.start.lower()
case PrintfStringText():
return self.extract_prefix(node.origin)
return ""
def _extract_prefix_raw_value(self, node: StringLiteralNodeType) -> tuple[str, str]:
raw_value = extract_raw_value(node)
prefix = self.extract_prefix(node)
return prefix, raw_value
class CleanCode(Codemod):
METADATA_DEPENDENCIES = (
ParentNodeProvider,
ScopeProvider,
)
def transform_module_impl(self, tree: cst.Module) -> cst.Module:
result = RemoveEmptyStringConcatenation(self.context).transform_module(tree)
result = RemoveEmptyExpressionsFormatting(self.context).transform_module(result)
result = NormalizeFStrings(self.context).transform_module(result)
result = RemoveUnusedVariables(self.context).transform_module(result)
result = UnnecessaryFormatString(self.context).transform_module(result)
return result
def should_allow_multiple_passes(self) -> bool:
return True
class SQLQueryParameterizationTransformer(
LibcstResultTransformer, UtilsMixin, ExtractPrefixMixin
):
change_description = "Parameterized SQL query execution."
METADATA_DEPENDENCIES: ClassVar[Collection[ProviderT]] = (
PositionProvider,
ScopeProvider,
ParentNodeProvider,
)
def __init__(
self,
*codemod_args,
**codemod_kwargs,
) -> None:
self.changed_nodes: dict[
cst.CSTNode | PrintfStringText | PrintfStringExpression,
ReplacementNodeType
| PrintfStringText
| PrintfStringExpression
| dict[str, Any],
] = {}
LibcstResultTransformer.__init__(self, *codemod_args, **codemod_kwargs)
UtilsMixin.__init__(
self,
codemod_args[1],
line_exclude=self.file_context.line_exclude,
line_include=self.file_context.line_include,
)
def _build_param_element(self, prepend, middle, append, linearized_query):
middle = [linearized_query.aliased.get(e, e) for e in middle]
new_middle = (
([prepend] if prepend else []) + middle + ([append] if append else [])
)
format_pieces: list[str] = []
format_expr_count = 0
args = []
if len(new_middle) == 1:
# TODO maybe handle conversion here?
return new_middle[0]
for e in new_middle:
exception = False
if isinstance(
e, cst.SimpleString | cst.FormattedStringText | PrintfStringText
):
prefix, raw_value = self._extract_prefix_raw_value(e)
if all(char not in prefix for char in "bru"):
format_pieces.append(raw_value)
exception = True
if not exception:
format_pieces.append(f"{{{format_expr_count}}}")
format_expr_count += 1
args.append(cst.Arg(e))
format_string = "".join(format_pieces)
format_string_node = cst.SimpleString(f"'{format_string}'")
return cst.Call(
func=cst.Attribute(value=format_string_node, attr=cst.Name(value="format")),
args=args,
)
def transform_module_impl(self, tree: cst.Module) -> cst.Module:
"""
The transformation is composed of 3 steps, each step is done by a codemod/visitor: (1) FindQueryCalls, (2) ExtractParameters, and (3) _fix_injection
Step (1) finds the `execute` calls and linearizing the query argument. Step (2) extracts the expressions that are parameters to the query.
Step (3) swaps the parameters in the query for `?` tokens and passes them as an arguments for the `execute` call. At the end of the transformation, the `CleanCode` codemod is executed to remove leftover empty strings and unused variables.
"""
# Step (1)
find_queries = FindQueryCalls(self.context)
tree.visit(find_queries)
for call, linearized_query in find_queries.calls.items():
# filter node
if not self.node_is_selected(call):
continue
# Step (2)
ep = ExtractParameters(self.context, linearized_query)
tree.visit(ep)
# Step (3)
params_elements: list[cst.Element] = []
for start, middle, end in ep.injection_patterns:
prepend, append = self._fix_injection(
start, middle, end, linearized_query
)
expr = self._build_param_element(
prepend, middle, append, linearized_query
)
params_elements.append(
cst.Element(
value=expr,
comma=cst.Comma(whitespace_after=cst.SimpleWhitespace(" ")),
)
)
# TODO research if named parameters are widely supported
# it could solve for the case of existing parameters
# TODO Do all middle expressions hail from a single source?
# e.g. the following
# name = 'user_' + input() + '_name'
# execute("'" + name + "'")
# should produce: execute("?", name)
# instead of: execute("?", 'user_{0}_name'.format(input()))
if params_elements:
tuple_arg = cst.Arg(cst.Tuple(elements=params_elements))
self.changed_nodes[call] = {"args": Append([tuple_arg])}
# made changes
if self.changed_nodes:
# build changed_nodes from parts here
new_changed_nodes = {}
new_parts_for = set()
for k, v in self.changed_nodes.items():
match k:
case PrintfStringText():
new_parts_for.add(k.origin)
case _:
new_changed_nodes[k] = v
for node in new_parts_for:
new_raw_value = ""
for part in linearized_query.node_pieces[node]:
new_part = self.changed_nodes.get(part) or part
match new_part:
case cst.SimpleString():
new_raw_value += new_part.raw_value
case PrintfStringText() | PrintfStringExpression():
new_raw_value += new_part.value
case _:
new_raw_value = ""
match node:
case cst.SimpleString():
new_changed_nodes[node] = node.with_changes(
value=node.prefix
+ node.quote
+ new_raw_value
+ node.quote
)
case cst.FormattedStringText():
new_changed_nodes[node] = node.with_changes(
value=new_raw_value
)
result = tree.visit(ReplaceNodes(new_changed_nodes))
self.changed_nodes = {}
line_number = self.get_metadata(PositionProvider, call).start.line
self.report_change_for_line(
line_number, SQLQueryParameterizationTransformer.change_description
)
# Normalization and cleanup
result = CleanCode(self.context).transform_module(result)
# return after a single change
return result
return tree
def should_allow_multiple_passes(self) -> bool:
return True
def _fix_injection(
self,
start: cst.CSTNode,
middle: list[cst.CSTNode],
end: cst.CSTNode,
linearized_query: LinearizedStringExpression,
):
for expr in middle:
if expr in linearized_query.aliased:
self.changed_nodes[linearized_query.aliased[expr]] = (
cst.parse_expression('""')
)
else:
match expr:
case cst.FormattedStringText() | cst.FormattedStringExpression():
self.changed_nodes[expr] = cst.RemovalSentinel.REMOVE
case _:
self.changed_nodes[expr] = cst.parse_expression('""')
# remove quote literal from start
updated_start = self.changed_nodes.get(start) or start
prefix, raw_value = self._extract_prefix_raw_value(updated_start)
# gather string after the quote
if "r" in prefix:
quote_span = list(raw_quote_pattern.finditer(raw_value))[-1]
else:
quote_span = list(quote_pattern.finditer(raw_value))[-1]
new_raw_value = raw_value[: quote_span.start()] + parameter_token
prepend_raw_value = raw_value[quote_span.end() :]
prepend = self._remove_literal_and_gather_extra(
start, updated_start, prefix, new_raw_value, prepend_raw_value
)
# remove quote literal from end
updated_end = self.changed_nodes.get(end) or end
prefix, raw_value = self._extract_prefix_raw_value(updated_end)
if "r" in prefix:
quote_span = list(raw_quote_pattern.finditer(raw_value))[0]
else:
quote_span = list(quote_pattern.finditer(raw_value))[0]
new_raw_value = raw_value[quote_span.end() :]
append_raw_value = raw_value[: quote_span.start()]
append = self._remove_literal_and_gather_extra(
end, updated_end, prefix, new_raw_value, append_raw_value
)
return (prepend, append)
def _remove_literal_and_gather_extra(
self, original_node, updated_node, prefix, new_raw_value, extra_raw_value
) -> Optional[cst.SimpleString]:
extra = None
match updated_node:
case cst.SimpleString():
# gather string after or before the quote
if extra_raw_value:
extra = cst.SimpleString(
value=updated_node.prefix
+ updated_node.quote
+ extra_raw_value
+ updated_node.quote
)
new_value = (
updated_node.prefix
+ updated_node.quote
+ new_raw_value
+ updated_node.quote
)
self.changed_nodes[original_node] = updated_node.with_changes(
value=new_value
)
case cst.FormattedStringText():
if extra_raw_value:
extra = cst.SimpleString(
value=("r" if "r" in prefix else "") + f"'{extra_raw_value}'"
)
new_value = new_raw_value
self.changed_nodes[original_node] = updated_node.with_changes(
value=new_value
)
case PrintfStringText():
if extra_raw_value:
extra = cst.SimpleString(
value=("r" if "r" in prefix else "") + f"'{extra_raw_value}'"
)
new_value = new_raw_value
self.changed_nodes[original_node] = replace(
updated_node, value=new_value
)
return extra
SQLQueryParameterization = CoreCodemod(
metadata=Metadata(
name="sql-parameterization",
summary="Parameterize SQL Queries",
review_guidance=ReviewGuidance.MERGE_AFTER_CURSORY_REVIEW,
references=[
Reference(url="https://cwe.mitre.org/data/definitions/20"),
Reference(url="https://cwe.mitre.org/data/definitions/89"),
Reference(url="https://owasp.org/www-community/attacks/SQL_Injection"),
],
),
transformer=LibcstTransformerPipeline(SQLQueryParameterizationTransformer),
detector=None,
)
class ExtractParameters(
ContextAwareVisitor, NameAndAncestorResolutionMixin, ExtractPrefixMixin
):
"""
This visitor a takes the linearized query and extracts the expressions that are parameters in this query. An expression is a parameter if it is surrounded by single quotes in the query. It results in a list of triples (start, middle, end), where start and end contains the expressions with single quotes marking the parameter, and middle is a list of expressions that composes the parameter.
"""
def __init__(
self,
context: CodemodContext,
linearized_query: LinearizedStringExpression,
) -> None:
self.linearized_query = linearized_query
self.injection_patterns: list[
tuple[
cst.CSTNode,
list[cst.CSTNode],
cst.CSTNode,
]
] = []
super().__init__(context)
def leave_Module(self, original_node: cst.Module):
leaves = list(reversed(self.linearized_query.parts))
modulo_2 = 1
# treat it as a stack
while leaves:
# search for the literal start, we detect the single quote
start = leaves.pop()
if not self._is_literal_start(start, modulo_2):
continue
middle = []
# gather expressions until the literal ends
while leaves and not self._is_literal_end(leaves[-1]):
middle.append(leaves.pop())
# could not find the literal end
if not leaves:
break
end = leaves.pop()
if any(map(self._is_injectable, middle)):
if (
self._can_be_changed(start)
and self._can_be_changed(end)
and all(map(self._can_be_changed_middle, middle))
):
self.injection_patterns.append((start, middle, end))
# end may contain the start of another literal, put it back
# should not be a single quote
if self._is_literal_start(end, 0) and self._is_not_a_single_quote(end):
modulo_2 = 0
leaves.append(end)
else:
modulo_2 = 1
def _is_not_a_single_quote(self, expression: StringLiteralNodeType) -> bool:
prefix, raw_value = self._extract_prefix_raw_value(expression)
if "b" in prefix:
return False
if "r" in prefix:
return raw_quote_pattern.fullmatch(raw_value) is None
return quote_pattern.fullmatch(raw_value) is None
def _is_assigned_to_exposed_scope(self, expression):
# is it part of an expression that is assigned to a variable in an exposed scope?
path = self.path_to_root(expression)
for i, node in enumerate(path):
# ensure it descend from the value attribute
if isinstance(node, cst.Assign) and (i > 0 and path[i - 1] == node.value):
expression = node.value
scope = self.get_metadata(ScopeProvider, node, None)
match scope:
case GlobalScope() | ClassScope() | None:
return True
named, other = self.find_transitive_assignment_targets(expression)
for t in itertools.chain(named, other):
scope = self.get_metadata(ScopeProvider, t, None)
match scope:
case GlobalScope() | ClassScope() | None:
return True
return False
def _is_target_in_exposed_scope(self, expression):
assignments = self.find_assignments(expression)
for assignment in assignments:
match assignment.scope:
case GlobalScope() | ClassScope() | None:
return True
return False
def _can_be_changed_middle(self, expression):
# is it assigned to a variable with global/class scope?
# is itself a target in global/class scope?
# if the expression is aliased, it is just a reference and we can always change
match expression:
case PrintfStringText():
expression = expression.origin
if expression in self.linearized_query.aliased:
return True
return not (
self._is_target_in_exposed_scope(expression)
or self._is_assigned_to_exposed_scope(expression)
)
def _can_be_changed(self, expression):
# is it assigned to a variable with global/class scope?
# is itself a target in global/class scope?
match expression:
case PrintfStringText():
expression = expression.origin
return not (
self._is_target_in_exposed_scope(expression)
or self._is_assigned_to_exposed_scope(expression)
)
def _is_injectable(self, expression: cst.BaseExpression) -> bool:
return not bool(infer_expression_type(expression))
def _is_literal_start(
self,
node: cst.CSTNode | PrintfStringText | PrintfStringExpression,
modulo_2: int,
) -> bool:
if isinstance(
node, cst.SimpleString | cst.FormattedStringText | PrintfStringText
):
prefix, raw_value = self._extract_prefix_raw_value(node)
if "b" in prefix:
return False
if "r" in prefix:
matches = list(raw_quote_pattern.finditer(raw_value))
else:
matches = list(quote_pattern.finditer(raw_value))
# avoid cases like: "where name = 'foo\\\'s name'"
# don't count \\' as these are escaped in string literals
return (matches is not None) and len(matches) % 2 == modulo_2
return False
def _is_literal_end(
self, node: cst.CSTNode | PrintfStringExpression | PrintfStringText
) -> bool:
if isinstance(
node, cst.SimpleString | cst.FormattedStringText | PrintfStringText
):
prefix, raw_value = self._extract_prefix_raw_value(node)
if prefix is None:
return False
if "b" in prefix:
return False
if "r" in prefix:
matches = list(raw_quote_pattern.finditer(raw_value))
else:
matches = list(quote_pattern.finditer(raw_value))
return bool(matches)
return False
class FindQueryCalls(ContextAwareVisitor, LinearizeStringMixin):
"""
Finds `execute` calls and linearizes the query argument. The result is a dict mappig each detected call with the linearized query.
"""
# Right now it works by looking into some sql keywords in any pieces of the query
# Ideally we should infer what driver we are using
sql_keywords: list[str] = ["insert", "select", "delete", "create", "alter", "drop"]
def __init__(self, context: CodemodContext) -> None:
self.calls: dict = {}
super().__init__(context)
def _has_keyword(self, string: str) -> bool:
for keyword in self.sql_keywords:
if keyword in string.lower():
return True
return False
def leave_Call(self, original_node: cst.Call) -> None:
maybe_call_name = get_function_name_node(original_node)
if maybe_call_name and maybe_call_name.value == "execute":
# TODO don't parameterize if there are parameters already
# may be temporary until I figure out if named parameter will work on most drivers
if len(original_node.args) > 0 and len(original_node.args) < 2:
first_arg = original_node.args[0] if original_node.args else None
if first_arg:
linearized_string_expr = self.linearize_string_expression(
first_arg.value
)
for part in (
linearized_string_expr.parts if linearized_string_expr else []
):
match part:
case (
cst.SimpleString()
| cst.FormattedStringText()
| PrintfStringText()
) if self._has_keyword(part.value):
self.calls[original_node] = linearized_string_expr
break