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use std::fs::File;
use std::io::Read;
use std::path::Path;
use std::collections::HashMap;
use byteorder::{WriteBytesExt, BigEndian};
use regex::Regex;
use serde::Deserialize;
use log::{debug, warn};
#[derive(Debug)]
struct OperatorTree {
left: Box<OperatorNode>,
right: Box<OperatorNode>,
operator: u8,
}
#[derive(Debug)]
struct OperatorOf {
n: String,
pattern: String,
}
#[derive(Debug)]
enum OperatorNode {
Tree(OperatorTree),
Of(OperatorOf),
Identifier(String),
}
#[derive(Deserialize, Debug)]
struct RuleString {
id: String,
#[serde(rename = "type")]
string_type: u8,
text: String,
modifiers: HashMap<String, bool>,
}
#[derive(Deserialize, Debug)]
struct RuleEntry {
identifier: String,
condition: String,
strings: Vec<RuleString>,
}
pub struct YaraDatabase {
entries: Vec<RuleEntry>,
pub data: Vec<u8>,
}
impl YaraDatabase {
const STRING_TYPE_STRING: u8 = 0;
const STRING_TYPE_HEX: u8 = 1;
const STRING_TYPE_REGEX: u8 = 2;
const WILDCARD_NIBBLE_LOW: u8 = 0;
const WILDCARD_NIBBLE_HIGH: u8 = 1;
const WILDCARD_NIBBLE_BOTH: u8 = 2;
const CONDITION_OPERATOR_OR: u8 = 0;
const CONDITION_OPERATOR_AND: u8 = 1;
const CONDITION_OPERATOR_OF: u8 = 2;
const CONDITION_OPERATOR_SINGLE: u8 = 3;
const CONDITION_OPERATOR_TRUE: u8 = 4;
pub fn new() -> Self {
YaraDatabase {
entries: Vec::new(),
data: Vec::new(),
}
}
pub fn add_file<P: AsRef<Path>>(&mut self, path: P) -> Result<(), Box<dyn std::error::Error>> {
let mut f = File::open(path)?;
let mut content = String::new();
f.read_to_string(&mut content)?;
let json: serde_json::Value = serde_json::from_str(&content)?;
if let Some(rules) = json.get("rules") {
self.entries.extend(serde_json::from_value::<Vec<RuleEntry>>(rules.clone())?);
}
Ok(())
}
fn build_tree(condition: &str) -> OperatorNode {
let pattern_or = Regex::new(r"(.*)\s+or\s+(.*)").unwrap();
let pattern_and = Regex::new(r"(.*)\s+and\s+(.*)").unwrap();
let pattern_of = Regex::new(r"((\d+)|(all)|(any))\s+of\s+([\w\_\(\)\$\*\,]+)").unwrap();
debug!("Parsing condition = {}", condition);
if let Some(caps) = pattern_or.captures(condition) {
return OperatorNode::Tree(OperatorTree {
left: Box::new(Self::build_tree(&caps[1])),
right: Box::new(Self::build_tree(&caps[2])),
operator: Self::CONDITION_OPERATOR_OR,
});
}
if let Some(caps) = pattern_and.captures(condition) {
return OperatorNode::Tree(OperatorTree {
left: Box::new(Self::build_tree(&caps[1])),
right: Box::new(Self::build_tree(&caps[2])),
operator: Self::CONDITION_OPERATOR_AND,
});
}
if let Some(caps) = pattern_of.captures(condition) {
let n = caps[1].to_string();
let pattern = caps[5].to_string();
debug!("Leaf: OperatorOf, n = {}, pattern = {}", n, pattern);
return OperatorNode::Of(OperatorOf { n, pattern });
}
debug!("Leaf: remainder = {}", condition);
OperatorNode::Identifier(condition.trim().to_string())
}
fn compile_tree(node: &OperatorNode, strings: &[String]) -> Vec<u8> {
let mut data = Vec::new();
match node {
OperatorNode::Tree(tree) => {
data.write_u8(tree.operator).unwrap();
data.extend(Self::compile_tree(&tree.left, strings));
data.extend(Self::compile_tree(&tree.right, strings));
}
OperatorNode::Of(op_of) => {
debug!("Compiling OperatorOf, n = {}, pattern = {}", op_of.n, op_of.pattern);
data.write_u8(Self::CONDITION_OPERATOR_OF).unwrap();
let mut pattern = String::new();
let mut para = 0;
for c in op_of.pattern.chars() {
match c {
'$' => pattern.push_str(r"\$"),
'*' => pattern.push_str(".*"),
',' => pattern.push_str(")|("),
'(' => { pattern.push('('); para += 1; }
')' => {
if para == 0 {
warn!("Unmatched parenthesis in pattern {}", op_of.pattern);
} else {
pattern.push(')');
para -= 1;
}
}
' ' => {}
other => pattern.push(other),
}
}
let re = Regex::new(&format!("^({})$", pattern)).unwrap();
let of_elements: Vec<u8> = strings.iter().enumerate()
.filter(|(_, s)| re.is_match(s))
.map(|(i, _)| i as u8)
.collect();
let n = match op_of.n.as_str() {
"all" => 0,
"any" => 1,
_ => op_of.n.parse::<u8>().unwrap_or(0),
};
data.write_u8(n).unwrap();
data.write_u8(of_elements.len() as u8).unwrap();
for e in of_elements {
data.write_u8(e).unwrap();
}
}
OperatorNode::Identifier(id) => {
debug!("Compiling single identifier {}", id);
let mut found = false;
for (i, s) in strings.iter().enumerate() {
if s == id {
data.write_u8(Self::CONDITION_OPERATOR_SINGLE).unwrap();
data.write_u8(i as u8).unwrap();
found = true;
break;
}
}
if !found {
warn!("Single identifier {} not found, defaulting to true", id);
data.write_u8(Self::CONDITION_OPERATOR_TRUE).unwrap();
}
}
}
data
}
}
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