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use super::super::{CertRule, RuleViolation};
use crate::manifest::{RuleCategory, Severity};
use crate::utility::cert_c::ast_utils;
use lang_parsing_substrate::query;
use tree_sitter::Node;
pub struct Str03C;
impl CertRule for Str03C {
fn rule_id(&self) -> &'static str {
"STR03-C"
}
fn description(&self) -> &'static str {
"Do not inadvertently truncate a string"
}
fn severity(&self) -> Severity {
Severity::Medium
}
fn category(&self) -> RuleCategory {
RuleCategory::Recommendation
}
fn cert_id(&self) -> &'static str {
"STR03-C"
}
fn scan(&self, node: &Node, source: &str, violations: &mut Vec<RuleViolation>) {
self.check_node(node, source, violations);
}
}
impl Str03C {
fn check_node(&self, node: &Node, source: &str, violations: &mut Vec<RuleViolation>) {
for n in query::find_descendants(*node, |_| true) {
// Check for function calls that can truncate strings
if n.kind() == "call_expression" {
if let Some(function) = n.child_by_field_name("function") {
let func_name = ast_utils::get_node_text(&function, source);
match func_name {
"strncpy" | "strncat" | "snprintf"
// Check if there's proper length validation before this call
if !self.has_length_validation_before(&n, source) => {
violations.push(RuleViolation {
rule_id: self.rule_id().to_string(),
severity: self.severity(),
message: format!(
"Call to {} may inadvertently truncate string without proper length validation",
func_name
),
file_path: String::new(),
line: n.start_position().row + 1,
column: n.start_position().column + 1,
suggestion: Some(
"Validate string length before calling truncating functions, or use strcpy() after validation"
.to_string(),
),
requires_manual_review: Some(true),
});
}
_ => {}
}
}
}
// CWE-464: Detect (char)atoi(...) — atoi returns 0 on failure, which becomes
// a null sentinel '\0' when cast to char, inadvertently truncating strings.
if n.kind() == "cast_expression" {
self.check_atoi_char_cast(&n, source, violations);
}
}
}
/// CWE-464: Detect (char)atoi(...) pattern.
/// atoi() returns 0 on failure, which when cast to char becomes '\0' (null sentinel).
fn check_atoi_char_cast(&self, node: &Node, source: &str, violations: &mut Vec<RuleViolation>) {
// Check if the cast type is char
if let Some(type_node) = node.child_by_field_name("type") {
let type_text = ast_utils::get_node_text(&type_node, source);
if type_text != "char" {
return;
}
} else {
return;
}
// Check if the value is an atoi/strtol call
if let Some(value) = node.child_by_field_name("value") {
let call_node = if value.kind() == "call_expression" {
Some(value)
} else if value.kind() == "parenthesized_expression" {
// Handle (char)(atoi(...))
value.child(1).filter(|c| c.kind() == "call_expression")
} else {
None
};
if let Some(call) = call_node {
if let Some(func) = call.child_by_field_name("function") {
let func_name = ast_utils::get_node_text(&func, source);
if matches!(func_name, "atoi" | "strtol" | "strtoul" | "atol") {
let start_point = node.start_position();
violations.push(RuleViolation {
rule_id: self.rule_id().to_string(),
severity: Severity::Medium,
message: format!(
"Cast of {}() to char: returns 0 on failure, producing null sentinel '\\0' that truncates strings",
func_name
),
file_path: String::new(),
line: start_point.row + 1,
column: start_point.column + 1,
suggestion: Some(
"Use strtol() with error checking, or validate the result is non-zero before casting to char"
.to_string(),
),
..Default::default()
});
}
}
}
}
}
/// Check if there's length validation before this call
fn has_length_validation_before(&self, call_node: &Node, source: &str) -> bool {
// Find the enclosing statement
let mut current = call_node.parent();
while let Some(node) = current {
if matches!(
node.kind(),
"compound_statement" | "function_definition" | "translation_unit"
) {
// Look for if statements that validate length
return self.find_length_check_in_scope(
&node,
call_node.start_position().row,
source,
);
}
current = node.parent();
}
false
}
/// Search for length validation in the scope before the call
fn find_length_check_in_scope(
&self,
scope_node: &Node,
call_line: usize,
source: &str,
) -> bool {
// Any if-statement descendant starting before the call line is a
// candidate — a descendant starting at/after call_line can never
// contain a nested if starting earlier (children start no earlier
// than their parent), so this flat filter is equivalent to the
// depth-first walk that stopped descending past call_line.
query::find_descendants_of_kind(*scope_node, "if_statement")
.into_iter()
.filter(|n| n.start_position().row < call_line)
.any(|if_node| {
let Some(condition) = if_node.child_by_field_name("condition") else {
return false;
};
let cond_text = ast_utils::get_node_text(&condition, source);
if !self.is_length_validation(&cond_text) {
return false;
}
// Accept if the call is in the else branch (safe path)
if let Some(alternative) = if_node.child_by_field_name("alternative") {
if self.is_ancestor(&alternative, call_line) {
return true;
}
}
// Accept if the length check precedes the call in the
// same scope — the if handles the overlong case (e.g.,
// error/return), so code after the if is safe.
if_node.end_position().row < call_line
})
}
/// Check if a condition validates string length
fn is_length_validation(&self, condition: &str) -> bool {
// Look for patterns like:
// - strlen(x) >= sizeof(y)
// - strlen(x) < sizeof(y)
// - strlen(x) > n
(condition.contains("strlen")
&& (condition.contains("sizeof") || condition.contains(">") || condition.contains("<")))
|| (condition.contains("sizeof") && condition.contains("strlen"))
}
/// Check if the given line falls within this node's span. A descendant's
/// span is always a subset of its ancestor's, so checking `node` alone
/// is equivalent to checking `node` or any of its descendants.
fn is_ancestor(&self, node: &Node, target_line: usize) -> bool {
node.start_position().row <= target_line && target_line <= node.end_position().row
}
}