如何使用yaraQA提升Yara规则的质量和性能
yaraQA是一款功能强大的Yara规则分析工具，在该工具的帮助下，广大研究人员可以轻松提升Yara规则的质量和性能。
很多Yara规则可能在语法上是正确的，但功能很可能仍然存在问题。而yaraQA则会试图找到这些问题并将其报告给YARA规则集的开发者或维护者。
yaraQA的功能
yaraQA会尝试检测下列问题：
1、语法正确，但由于条件中的错误，从而导致不匹配的规则； 2、使用可能错误的字符串和修饰符组合的规则（例如$ = "\\Debug\\" fullword）； 3、由短原子、重复字符或循环引起的性能问题（例如$ = "AA"; 可以使用--ignore-performance从分析中排除）；
工具安装
由于该工具基于Python 3开发，因此我们首先需要在本地设备上安装并配置好Python 3环境。接下来，广大研究人员可以使用下列命令将该项目源码克隆至本地：
git clone https://github.com/Neo23x0/yaraQA.git
然后切换到项目目录中，使用pip工具和项目提供的requirements.txt文件安装该工具所需的其他依赖组件：
cd yaraQA/
pip install -r requirements.txt
工具使用帮助
usage: yaraQA.py [-h] [-f yara files [yara files ...]] [-d yara files [yara files ...]] [-o outfile] [-b baseline] [-l level]
[--ignore-performance] [--debug]
YARA RULE ANALYZER
optional arguments:
-h, --help 显示工具帮助信息和退出
-f yara files [yara files ...]
输入文件路径（一个或多个Yara规则，由空格分隔）
-d yara files [yara files ...]
输入目录路径（Yara规则目录，由空格分隔）
-o outfile 分析结果输出文件（JSON格式，默认为'yaraQA-issues.json'）
-b baseline 使用一个问题基线来过滤分析结果中的问题
-l level 要显示的最低级别（1=基本信息, 2=警告, 3=严重）
--ignore-performance 屏蔽与性能相关的规则问题
--debug 调试模式输出
工具使用样例
python3 yaraQA.py -d ./test/
屏蔽所有性能相关的问题，仅显示逻辑问题：
python3 yaraQA.py -d ./test/ --ignore-performance
屏蔽所有信息性字符问题：
python3 yaraQA.py -d ./test/ -level 2
使用一个基线，仅显示新的问题，基线文件需要是一个.json文件：
python3 yaraQA.py -d ./test/ -b yaraQA-reviewed-issues.json
工具输出
yaraQA会将检测到的问题写入一个名为yaraQA-issues.json的文件中。
下面给出的是yaraQA生成的JSON格式结果：
[
{
"rule": "Demo_Rule_1_Fullword_PDB",
"id": "SM1",
"issue": "The rule uses a PDB string with the modifier 'wide'. PDB strings are always included as ASCII strings. The 'wide' keyword is unneeded.",
"element": {
"name": "$s1",
"value": "\\\\i386\\\\mimidrv.pdb",
"type": "text",
"modifiers": [
"ascii",
"wide",
"fullword"
]
},
"level": "info",
"type": "logic",
"recommendation": "Remove the 'wide' modifier"
},
{
"rule": "Demo_Rule_1_Fullword_PDB",
"id": "SM2",
"issue": "The rule uses a PDB string with the modifier 'fullword' but it starts with two backslashes and thus the modifier could lead to a dysfunctional rule.",
"element": {
"name": "$s1",
"value": "\\\\i386\\\\mimidrv.pdb",
"type": "text",
"modifiers": [
"ascii",
"wide",
"fullword"
]
},
"level": "warning",
"type": "logic",
"recommendation": "Remove the 'fullword' modifier"
},
{
"rule": "Demo_Rule_2_Short_Atom",
"id": "PA2",
"issue": "The rule contains a string that turns out to be a very short atom, which could cause a reduced performance of the complete rule set or increased memory usage.",
"element": {
"name": "$s1",
"value": "{ 01 02 03 }",
"type": "byte"
},
"level": "warning",
"type": "performance",
"recommendation": "Try to avoid using such short atoms, by e.g. adding a few more bytes to the beginning or the end (e.g. add a binary 0 in front or a space after the string). Every additional byte helps."
},
{
"rule": "Demo_Rule_3_Fullword_FilePath_Section",
"id": "SM3",
"issue": "The rule uses a string with the modifier 'fullword' but it starts and ends with two backslashes and thus the modifier could lead to a dysfunctional rule.",
"element": {
"name": "$s1",
"value": "\\\\ZombieBoy\\\\",
"type": "text",
"modifiers": [
"ascii",
"fullword"
]
},
"level": "warning",
"type": "logic",
"recommendation": "Remove the 'fullword' modifier"
},
{
"rule": "Demo_Rule_4_Condition_Never_Matches",
"id": "CE1",
"issue": "The rule uses a condition that will never match",
"element": {
"condition_segment": "2 of",
"num_of_strings": 1
},
"level": "error",
"type": "logic",
"recommendation": "Fix the condition"
},
{
"rule": "Demo_Rule_5_Condition_Short_String_At_Pos",
"id": "PA1",
"issue": "This rule looks for a short string at a particular position. A short string represents a short atom and could be rewritten to an expression using uint(x) at position.",
"element": {
"condition_segment": "$mz at 0",
"string": "$mz",
"value": "MZ"
},
"level": "warning",
"type": "performance",
"recommendation": ""
},
{
"rule": "Demo_Rule_5_Condition_Short_String_At_Pos",
"id": "PA2",
"issue": "The rule contains a string that turns out to be a very short atom, which could cause a reduced performance of the complete rule set or increased memory usage.",
"element": {
"name": "$mz",
"value": "MZ",
"type": "text",
"modifiers": [
"ascii"
]
},
"level": "warning",
"type": "performance",
"recommendation": "Try to avoid using such short atoms, by e.g. adding a few more bytes to the beginning or the end (e.g. add a binary 0 in front or a space after the string). Every additional byte helps."
},
{
"rule": "Demo_Rule_6_Condition_Short_Byte_At_Pos",
"id": "PA1",
"issue": "This rule looks for a short string at a particular position. A short string represents a short atom and could be rewritten to an expression using uint(x) at position.",
"element": {
"condition_segment": "$mz at 0",
"string": "$mz",
"value": "{ 4d 5a }"
},
"level": "warning",
"type": "performance",
"recommendation": ""
},
{
"rule": "Demo_Rule_6_Condition_Short_Byte_At_Pos",
"id": "PA2",
"issue": "The rule contains a string that turns out to be a very short atom, which could cause a reduced performance of the complete rule set or increased memory usage.",
"element": {
"name": "$mz",
"value": "{ 4d 5a }",
"type": "byte"
},
"level": "warning",
"type": "performance",
"recommendation": "Try to avoid using such short atoms, by e.g. adding a few more bytes to the beginning or the end (e.g. add a binary 0 in front or a space after the string). Every additional byte helps."
},
{
"rule": "Demo_Rule_6_Condition_Short_Byte_At_Pos",
"id": "SM3",
"issue": "The rule uses a string with the modifier 'fullword' but it starts and ends with two backslashes and thus the modifier could lead to a dysfunctional rule.",
"element": {
"name": "$s1",
"value": "\\\\Section\\\\in\\\\Path\\\\",
"type": "text",
"modifiers": [
"ascii",
"fullword"
]
},
"level": "warning",
"type": "logic",
"recommendation": "Remove the 'fullword' modifier"
}
]
包含问题的规则样例
项目专门提供了包含问题的规则样例，可以在./test目录中找到。
工具运行截图
许可证协议
本项目的开发与发布遵循GPL-3.0开源许可证协议。
项目地址
yaraQA：https://github.com/Neo23x0/yaraQA
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原始发表：2023-08-14 18:57，如有侵权请联系 cloudcommunity@tencent.com 删除
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