跳跳糖
0 简介
CodeQL是一个帮助开发者自动完成安全检查、帮助安全研究者进行变异分析的分析引擎。它由代码数据库和代码语义分析引擎组成，通过将代码抽象为数据查询表保存到代码数据库中，可以方便地运行代码查询。本文的关注点在于CodeQL是如何生成代码数据库。
1 原理分析
这里以java作为示例语言进行分析
1.1 工作流程概览
在配置好CodeQL以后，用户目录下的codeql-home/codeql文件夹保存了CodeQL的CLI部分，它的目录结构如下，这里省略了部分无关文件
.
├── codeql
├── java
│ ├── codeql-extractor.yml
│ ├── semmlecode.dbscheme
│ ├── semmlecode.dbscheme.stats
│ └── tools
│ ├── autobuild-fat.jar
│ ├── autobuild.cmd
│ ├── autobuild.sh
│ ├── codeql-java-agent.jar
│ ├── compiler-tracing.spec
│ ├── macos
│ ├── pre-finalize.sh
│ ├── semmle-extractor-java.jar
│ └── tracing-config.lua
└──── tools
├── codeql.jar
├── osx64
├── test
└── tracer
CodeQL的入口文件为codeql，这是一个shell脚本，主要目的就是为调用codeql.jar做准备，包括检查环境和配置环境变量。codeql.jar是CodeQL的核心文件，包含了命令行解析、数据库创建和查询引擎相关的代码。
这里以创建数据库的指令为例。创建数据库要经过下面三步
initialize 初始化数据库，用到codeql.jar
build 生成trap文件，用到codeql-java-agent.jar，semmle-extractor-java.jar
finalize 将trap文件导入数据库，用到pre-finalize.sh，codeql.jar
我们按照这个流程，分成三步进行分析
1.2 initialize
我们新建一个IDEA工程，将codeql.jar导入为依赖库，然后编写如下代码
package cokeBeer;
import com.semmle.cli2.CodeQL;
import java.io.File;
public class RunCreate {
public static void main(String[] args) {
//参数部分可以自由配置，只要能正常运行database create的参数即可
String UserHome=System.getProperty("user.home");
String language="java";
String command="mvn clean package";
String ProjectName="java-sec-code";
String CodeQLHome=String.join(File.separator,UserHome,"codeql-home");
String SourceRoot=String.join(File.separator,CodeQLHome,"source","java-source");
String DatabaseRoot=String.join(File.separator,CodeQLHome,"database","java-database");
String source=String.join(File.separator,SourceRoot,ProjectName);
String database=String.join(File.separator,DatabaseRoot,ProjectName);
String[] QLArgs=new String[]{"database","create","-v","--overwrite","-l",language,"-s",source,"-c",command,database};
//调用CodeQL的入口方法，可以在这里下断点
CodeQL.main(QLArgs);
}
}
这里选择java-sec-code这个项目作为测试项目。具体选择的项目内容对分析过程没有影响，编译指令正确即可。
在入口方法处打上断点，开始调试，接下来的方法调用过程如下
com.semmle.cli2.CodeQL#main
com.semmle.cli2.picocli.SubcommandMaker#runMain(java.lang.String[])
com.semmle.cli2.picocli.SubcommandMaker#runMain(java.lang.String[], java.util.function.Function<com.semmle.cli2.picocli.SubcommandCommon,java.lang.Integer>, boolean)
java.util.function.Function#apply
com.semmle.cli2.picocli.SubcommandCommon#call
com.semmle.cli2.database.CreateCommand#executeSubcommand
最后是进入到了CreataeCommmand类，这个类处理创建数据库相关的操作，这里简化了部分代码，方法逻辑流程如下
protected void executeSubcommand() throws SubcommandDone {
// 初始化数据库
this.runPlumbingInProcess(InitCommand.class, new Object[]{this.initOptions, "--source-root=" + this.sourceRoot, "--allow-missing-source-root=" + this.traceCommandOptions.hasWorkingDir(), "--allow-already-existing", "--", this.initOptions.directory});
...
// 运行编译指令
this.runPlumbingInProcess(TraceCommandCommand.class, new Object[]{threadsOption(this.threads), ramOption(this.ram), this.tracingOptions, this.traceCommandOptions, this.extractorOptionsOptions, indexTracelessOption, multispec, "--", multispec.directory, commandLine});
...
// finalize
this.runPlumbingInProcess(FinalizeCommand.class, new Object[]{threadsOption(this.threads), ramOption(this.ram), this.finalizeParams, multispec, "--", multispec.directory});
}
}
我们进入初始化数据库的代码，调用链如下
com.semmle.cli2.picocli.SubcommandCommon#runPlumbingInProcess
com.semmle.cli2.picocli.PlumbingRunner#run
com.semmle.cli2.database.InitCommand#executeSubcommand
com.semmle.cli2.database.InitCommand#initOneDatabase
最后是进入了InitCommand类，这个类负责初始化数据库。initOneDatabase的代码简化后如下
private void initOneDatabase(String language, Path databaseDir, long linesOfCode, Optional<String> shaAnalyzed) {
// 搜索extractor
Map<String, List<Path>> allExtractors = ((ResolveLanguagesResult)this.callPlumbingInProcess(ResolveLanguagesCommand.class, new Object[]{this.options.extractorOptions})).getExtractorRoots();
List<Path> found = (List)allExtractors.get(language);
Path packRoot = (Path)found.get(0);
// 创建extractor对象
CodeQLExtractor extractor = new CodeQLExtractor(packRoot);
DbInfo dbInfo = new DbInfo(this.sourceRoot.toString(), extractor.usesUnicodeNewlines(), extractor.getColumnKind(), language, allExtractors, linesOfCode, (String)shaAnalyzed.orElse((Object)null), CodeQLVersion.currentVersion().version);
// 创建 skeleton
DatabaseLayout layout = DatabaseLayout.create(databaseDir, dbInfo);
}
运行完成后，数据库目录下会出现codeql-database.yml文件
java-sec-code $ tree -L 1
.
├── codeql-database.yml
└── log
从initalize部分返回以后，就进入了build部分，这里我们先调试几步，调用链如下
com.semmle.cli2.picocli.SubcommandCommon#runPlumbingInProcess
com.semmle.cli2.picocli.PlumbingRunner#run
com.semmle.cli2.database.TraceCommandCommand#executeSubcommand
com.semmle.cli2.database.DatabaseProcessCommandCommon#executeSubcommand
这个executeSubcommand方法很长，我们关注他进行的两个关键操作。
一是读取compile.spec文件，创建Tracer，对应代码如下
TracerSetup tracerSetup = this.getTracerSetup(this.logger(), databases, scratchFolder, logFolder, extractors);
getTracerSetup里面又调用了getTracingSpec
extractor.getTracingSpec().get()
内容如下，这里getTracingSpec会去找extractor根目录下的tools/compile.spec文件并读取
public Optional<Path> getTracingSpec() {
Path tools = this.extractorRoot.resolve("tools");
Path platformTools = tools.resolve(CodeQLDist.currentPlatform().name());
Iterator var3 = Arrays.asList(platformTools.resolve("compiler-tracing.spec"), tools.resolve("compiler-tracing.spec")).iterator();
Path candidate;
do {
if (!var3.hasNext()) {
return Optional.empty();
}
candidate = (Path)var3.next();
} while(!Files.isRegularFile(candidate, new LinkOption[0]) || !Files.isReadable(candidate));
return Optional.of(candidate);
}
用于示例的是java的extractor，我们很容易找到对应的compile.spec，内容如下
jvm_prepend_arg -javaagent:${config_dir}/codeql-java-agent.jar=ignore-project,java
jvm_prepend_arg -Xbootclasspath/a:${config_dir}/codeql-java-agent.jar
可见CodeQL会在build前准备好调用code-java-agent.jar相关的参数
二是创建进程，运行build指令。
Builder8 p = new Builder8(cmdArgs, LogbackUtils.streamFor(this.logger(), "build-stdout", true), LogbackUtils.streamFor(this.logger(), "build-stderr", true), Env.systemEnv().getenv(), workingDir.toFile());
this.env.addToProcess(p);
List<String> cmdProcessor = new ArrayList();
CommandLine.addCommandProcessor(cmdProcessor, this.env.expander);
p.prependArgs(cmdProcessor);
tracerSetup.enableTracing(p);
StreamAppender streamOutAppender = new StreamAppender(Streams.out());
int result;
try {
LogbackUtils.addAppender(streamOutAppender);
result = p.execute();
} finally {
LogbackUtils.removeAppender(streamOutAppender);
}
经过一番设置，进程运行时的命令行如下
codeql-home/codeql/tools/osx64/preload_tracer mvn clean package
关键环境变量如下
CODEQL_EXTRACTOR_JAVA_ROOT -> codeql-home/codeql/java
CODEQL_SCRATCH_DIR -> codeql-home/database/java-database/java-sec-code/working
CODEQL_EXTRACTOR_JAVA_LOG_DIR -> codeql-home/database/java-database/java-sec-code/log
CODEQL_EXTRACTOR_JAVA_SOURCE_ARCHIVE_DIR -> codeql-home/database/java-database/java-sec-code/src
CODEQL_EXTRACTOR_JAVA_TRAP_DIR -> codeql-home/database/java-database/java-sec-code/trap/java
SEMMLE_JAVA_TOOL_OPTIONS -> '-javaagent:codeql-home/codeql/java/tools/codeql-java-agent.jar=ignore-project,java' '-Xbootclasspath/a:codeql-home/codeql/java/tools/codeql-java-agent.jar'
因为这里调用的preload_tracer为二进制文件，所以直接分析它的具体行为较为困难。
但是我们可以推测出，preload_tracer会监控编译的过程。当需要运行JVM时，preload_tracer会添加准备好的-javaagent参数，使得codeql-java-agent.jar参与到编译过程中去。
所以我们接下来的任务是分析codeql-java-agent.jar的行为
1.3 codeql-java-agent.jar
这一部分需要读者对于
java-agent技术和ASM技术有一定了解
java源文件文件一般使用javac作为编译程序，生成类文件。但是javac仅仅是一个封装程序，其实际的编译操作是调用com.sun.tools.javac包下的类来完成的。如果使用java-agent技术，劫持com.sun.tools.javac包下的关键方法，就能自定义编译行为。
我们编写如下代码来调试codeql-java-agent.jar
package cokeBeer;
import com.sun.tools.javac.main.Main;
import com.sun.tools.javac.util.Context;
public class RunAgent {
public static void main(String[] args) throws Exception{
Main main=new Main("");
String[] arg=new String[]{"Test.java"};
main.compile(arg,new Context());
System.out.println("run agent");
}
}
为了调试codeql-java-agent.jar，首先将其作为库文件导入IDEA，然后在运行配置中添加vmoptions如下
-javaagent:your-codeql-home/codeql/java/tools/codeql-java-agent.jar=ignore-project,java
同时在运行配置中添加环境变量如下
CODEQL_EXTRACTOR_JAVA_ROOT=your-codeql-home/codeql/java
CODEQL_EXTRACTOR_JAVA_LOG_DIR=your-test-dir/log
再找到入口方法com.semmle.extractor.java.InterceptingAgent#premain打上断点，就可以开始调试了
public static void premain(String agentArgs, Instrumentation inst) {
inst.addTransformer(new InterceptingAgent(agentArgs, new Interceptor[0]));
}
这里我们看到premain创建了一个InterceptingAgent类型的对象，然后添加为Transformer
我们先看InterceptingAgent的构造方法
public InterceptingAgent(String agentArgs, Interceptor... extraInterceptors) {
// 略去部分无关代码
Set<String> args = new LinkedHashSet(Arrays.asList(agentArgs.split(",")));
Iterator var6 = args.iterator();
while(var6.hasNext()) {
String arg = (String)var6.next();
if (!arg.equals("ignore-project")) {
if (arg.equals("java")) {
this.interceptors.add(new JavacMainInterceptor());
this.interceptors.add(new JavacToolInterceptor());
this.interceptors.add(new ECJInterceptor());
this.interceptors.add(new TakariLifecycleJdtInterceptor());
if (Boolean.parseBoolean(System.getenv("CODEQL_EXTRACTOR_JAVA_JSP"))) {
this.interceptors.add(new JasperJdtInterceptor());
this.interceptors.add(new JasperJspcInterceptor());
}
} else if (arg.equals("kotlin")) {
this.interceptors.add(new KotlinInterceptor());
} else {
warn(1, "Unrecognized agent specification: " + arg);
}
}
}
}
可以看出，根据输入参数的不同，会创建不同类型的Interceptor，插入到this.interceptors去。这里我们的输入参数为ignore-project,java，所以会插入JavacMainInterceptor和JavacToolInteceptor
然后我们看InterceptingAgent的tranform方法，这个方法会在类加载时被系统主动回调
public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) {
if (loader == null && !bootstrapLoadableClasses.contains(className)) {
info(2, "Skipping bootstrap-loaded class " + className);
return null;
} else if ((!className.startsWith("java/") || className.equals("java/lang/Shutdown")) && !className.startsWith("javax/") && !className.startsWith("sun/")) {
if (className.startsWith("com/semmle/extractor/java/interceptors/")) {
info(2, "Skipping intercept handler class " + className);
return null;
} else if (className.startsWith("jdk/internal/reflect/")) {
info(2, "Skipping reflection class " + className);
return null;
} else if (className.startsWith("com/semmle/org/objectweb/asm/")) {
info(2, "Skipping ASM class " + className);
return null;
} else {
boolean intercept = false;
Iterator var7 = this.interceptors.iterator();
while(var7.hasNext()) {
Interceptor i = (Interceptor)var7.next();
if (i.interceptType(className)) {
intercept = true;
break;
}
}
//对于需要拦截的类，接下来使用ASM技术进行分析
...
}
} else {
info(2, "Skipping system class " + className);
return null;
}
}
可以看到if-else判断过滤了java的内置类，以及CodeQL本身包含的类
然后遍历this.interceptors，调用interceptType方法进行判断。interceptType方法要求输入的类名必须和interceptor内置的拦截类名一致
例如JavacMainInterceptor，它的内置的拦截类就是com.sun.tools.javac.main.Main
public boolean interceptType(String binaryTypeName) {
return binaryTypeName.equals("com/sun/tools/javac/main/Main");
}
当成功匹配以后，就使用ASM技术，对这个类进行改造。调用ASM的代码如下
if (!intercept) {
info(2, "Skipping class with no interested interceptor: " + className);
return null;
} else {
info(1, "Transforming " + className);
try {
ClassReader reader = new ClassReader(classfileBuffer);
if ((reader.getAccess() & 512) != 0) {
info(2, "Skipping interface " + className);
return null;
} else {
ClassWriter writer = new ClassWriter(reader, 1);
reader.accept(new RewriteMethods(writer, className, this.collectMemberSignatures(classfileBuffer)), 0);
return writer.toByteArray();
}
} catch (RuntimeException var9) {
log("ERROR: Exception while processing " + className + ": " + var9);
var9.printStackTrace(System.out);
log("Current class loader: " + loader);
throw var9;
}
}
这里是创建了一个RewriteMethods类型的对象，继承ASM中的ClassVistor，来重写类文件。这个RewriteMethods主要做两件事情，一是拦截并改造特定类方法，这里需要看visitMethod方法，它创建了一个InterceptMethod类型的对象
public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
return new InterceptMethod(super.visitMethod(access, name, desc, signature, exceptions), access, name, desc);
}
InterceptMethod又继承了ASM中的MethodVistor，它实现了applyInterceptors方法，内部会尝试遍历this.interceptors保存的Interceptor，然后调用他们的intercept方法。
private void applyInterceptors(boolean before) {
InterceptingAgent.info(3, "Considering method " + this.name + this.desc + " in " + RewriteMethods.this.binaryTypeName + ".");
Iterator var2 = InterceptingAgent.this.interceptors.iterator();
while(var2.hasNext()) {
Interceptor i = (Interceptor)var2.next();
try {
// 这里调用了下面的applyInterceptor
this.applyInterceptor(i, before);
} catch (Throwable var5) {
InterceptingAgent.log("ERROR: Interceptor of type " + i.getClass() + " caused an exception: " + var5);
var5.printStackTrace(System.out);
}
}
}
private void applyInterceptor(Interceptor i, boolean before) {
if (i.interceptType(RewriteMethods.this.binaryTypeName)) {
Interceptor.Interception interception = i.intercept(RewriteMethods.this.binaryTypeName, RewriteMethods.this.classMembers, this.name, this.desc, before);
if (interception != null) {
InterceptingAgent.info(1, "Interceptor " + i + " wants to call " + interception + " for " + RewriteMethods.this.binaryTypeName + "." + this.name + this.desc + ".");
this.instrument(interception);
} else {
InterceptingAgent.info(2, "Interceptor " + i + " is not interested in " + RewriteMethods.this.binaryTypeName + "." + this.name + this.desc + ".");
}
}
}
这里调试时会调用到JavacMainInterceptor的intercept方法，里面拦截com.sun.tools.java.main.Main类型的两个compile方法，这两个方法都是负责编译源文件的方法
public Interceptor.Interception intercept(String binaryTypeName, Set<String> classMembers, String methodName, String methodDescriptor, boolean before) {
if (before) {
return null;
} else {
if (methodName.equals("compile")) {
if (methodDescriptor.equals("([Ljava/lang/String;Lcom/sun/tools/javac/util/Context;)Lcom/sun/tools/javac/main/Main$Result;")) {
return new Interceptor.Interception("com/semmle/extractor/java/interceptors/JavacMainInterceptor", "void javacMainResult(Object,String[])", new Interceptor.CallWith[]{CallWith.STACK_TOP, CallWith.FIRST_ARG});
}
if (methodDescriptor.equals("([Ljava/lang/String;Lcom/sun/tools/javac/util/Context;)I")) {
return new Interceptor.Interception("com/semmle/extractor/java/interceptors/JavacMainInterceptor", "int javacMainInt(int,String[])", new Interceptor.CallWith[]{CallWith.FIRST_ARG});
}
}
return null;
}
}
然后创建对应的Interception类型的对象并返回，从applyInterceptor方法中看到返回值会被传递给instrument方法，这个方法的向类字节码中写入了一个方法调用SEMMLE_INTERCEPT$0
private void instrument(Interceptor.Interception interception) {
Integer idx = (Integer)RewriteMethods.this.applicableInterceptions.get(interception);
if (idx == null) {
idx = RewriteMethods.this.applicableInterceptions.size();
RewriteMethods.this.applicableInterceptions.put(interception, idx);
}
Interceptor.CallWith[] var3 = interception.callWith();
int var4 = var3.length;
for(int var5 = 0; var5 < var4; ++var5) {
Interceptor.CallWith cw = var3[var5];
switch (cw) {
case ALL_ARGS:
this.loadArgs();
break;
case ALL_ARGS_AS_ARRAY:
this.loadArgArray();
break;
case FIRST_ARG:
this.loadArg(0);
break;
case CLASS:
this.visitLdcInsn(RewriteMethods.this.binaryTypeName);
break;
case METHOD_NAME_AND_DESC:
this.visitLdcInsn(this.name);
this.visitLdcInsn(this.desc);
break;
case STACK_TOP:
this.visitInsn(89);
break;
case THIS:
if (!this.isStatic && !this.name.equals("<init>")) {
this.visitVarInsn(25, 0);
} else {
this.visitInsn(1);
}
}
}
Method method = Method.getMethod(interception.methodDecl());
this.visitMethodInsn(184, RewriteMethods.this.binaryTypeName, "SEMMLE_INTERCEPT$" + idx, method.getDescriptor(), false);
}
RewriteMethods做的第二件事情是创建一个新方法，这个方法就是上面调用的方法SEMMLE_INTERCEPT$0
这个一部分对应着它的visitEnd方法，里面使用ASM技术，构造了这个新方法。
为了直观展示，我们直接获取最终转换好的字节码进行反编译。最终发生变化的部分如下
public Result compile(String[] var1, Context var2) {
Result var10000 = this.compile(var1, var2, List.nil(), (Iterable)null);
SEMMLE_INTERCEPT$0(var10000, var1);
return var10000;
}
private static void SEMMLE_INTERCEPT$0(Object var0, String[] var1) {
Object var10000 = var0;
String[] var10001 = var1;
try {
JavacMainInterceptor.javacMainResult(var10000, var10001);
} catch (NoClassDefFoundError var2) {
System.err.println("ERROR: Exception during invocation of Semmle Java compiler. Perhaps you need to put odasa-agent.jar on the boot classpath?");
var2.printStackTrace(System.err);
}
}
可以看到，新的compile方法获取原compile方法的输入参数和编译返回值，然后交给javacMainResult处理
@InterceptionMethod
public static void javacMainResult(Object result, String[] args) {
info(1, "Intercepted javac Main.compile(String[],Context): " + Arrays.toString(args));
String resultName = result.toString();
int javacExitCode = getJavacExitCode(resultName);
int odasaJavacExitCode = Utils.invokeOdasaJavac(javacExitCode, args);
if (javacExitCode == 0 && odasaJavacExitCode != 0) {
throw new Error("Fatal extractor error detected. Attempting to abort build commands.");
}
}
里面调用Utils.invoke0dasaJavac，之后的调用链如下
com.semmle.extractor.java.Utils#invokeOdasaJavac(int, java.lang.String[])
com.semmle.extractor.java.Utils#invokeOdasaJavac(int, java.lang.String[], boolean)
com.semmle.extractor.java.Utils#invokeOdasaJavac(int, java.lang.String[], boolean, java.util.Map<java.lang.String,java.lang.String>)
最后一个invoke0dasaJavac方法内部首先配置一系列的环境变量、设置命令行参数，参数内容如下
codeql-home/codeql/java/tools/macos/jdk-extractor-java/bin/java
-Dfile.encoding=UTF-8
-Xmx1024M
-Xms256M
--add-opens
java.base/sun.reflect.annotation=ALL-UNNAMED
-classpath
codeql-home/codeql/java/tools/semmle-extractor-java.jar
com.semmle.extractor.java.JavaExtractor
--jdk-version
-1
--javac-args
@@@/your-test-dir/log/ext/javac.args
然后使用这些参数创建一个程序对象并执行
Builder b = new Builder(cmdLine, System.out, System.err);
b.removeEnvVar("JAVA_TOOL_OPTIONS");
Iterator var38 = addEnv.entrySet().iterator();
while(var38.hasNext()) {
Map.Entry<String, String> entry = (Map.Entry)var38.next();
b.putEnvVar((String)entry.getKey(), (String)entry.getValue());
}
exitCode = b.execute();
所以这里就是使用CodeQL内置的java命令行程序调用semmle-extractor-java.jar
有了这些参数，我们可以主动调用semmle-extractor-java.jar了
1.4 semmle-extractor-java.jar
运行semmle-extractor-java.jar会解析项目源代码，生成trap文件
这里我们将semmle-extractor-java.jar作为依赖库添加到IDEA
并编写如下代码来调试semmle-extractor-java.jar，其中调用参数来自上面的分析过程
package cokeBeer;
import com.semmle.extractor.java.JavaExtractor;
import java.io.File;
public class RunExtractor {
public static void main(String[] args) {
String argPath="@@@/your-test-dir/log/ext/javac.args");
String[] ExtractorArgs=new String[]{"--jdk-version","-1","--javac-args",argPath};
JavaExtractor.main(ExtractorArgs);
}
}
为了调试semmle-extractor-java.jar，首先将其作为库文件导入IDEA，然后在运行配置中添加环境变量如下
TRAP_FOLDER=your-test-dir/trap/java
SOURCE_ARCHIVE=your-test-dir/src
在入口方法处打上断点，开始调试。JavaExtractor#main首先创建一个JavaExtractor类型的对象
public static void main(String[] args) {
String allArgs = StringUtil.glue(" ", args);
JavaExtractor extractor = new JavaExtractor(args);
boolean hasJavacErrors = false;
try {
hasJavacErrors = !extractor.runExtractor();
} catch (Throwable var8) {
...
} finally {
extractor.close();
}
}
然后运行com.semmle.extractor.java.JavaExtractor#runExtractor方法，里面使用JavacCompiler对源文件进行解析，然后利用解析信息生成trap文件
boolean runExtractor() {
// 省略了部分日志相关代码
// 准备编译环境
Context context = this.output.getContext();
JavacFileManager.preRegister(context, this.specialSourcepathHandling);
Arguments arguments = this.setupJavacOptions(context);
Options.instance(context).put("ignore.symbol.file", "ignore.symbol.file");
JavaFileManager jfm = (JavaFileManager)context.get(JavaFileManager.class);
JavaFileManager bfm = jfm instanceof DelegatingJavaFileManager ? ((DelegatingJavaFileManager)jfm).getBaseFileManager() : jfm;
JavacFileManager dfm = (JavacFileManager)bfm;
dfm.handleOptions(arguments.getDeferredFileManagerOptions());
arguments.validate();
if (jfm.isSupportedOption(Option.MULTIRELEASE.primaryName) == 1) {
Target target = Target.instance(context);
List<String> list = List.of(target.multiReleaseValue());
jfm.handleOption(Option.MULTIRELEASE.primaryName, list.iterator());
}
JavaCompiler compiler = JavaCompiler.instance(context);
compiler.genEndPos = true;
Set<JavaFileObject> fileObjects = arguments.getFileObjects();
// 解析源文件
javac_extend.com.sun.tools.javac.util.List<JCTree.JCCompilationUnit> parsedFiles = compiler.parseFiles(fileObjects);
compiler.enterTrees(compiler.initModules(parsedFiles));
Queue<Queue<javac_extend.com.sun.tools.javac.comp.Env<AttrContext>>> groupedTodos = Todo.instance(context).groupByFile();
int prevErr = 0;
while(true) {
while(true) {
JCTree.JCCompilationUnit cu;
while(true) {
Queue todo;
do {
cu = null;
Iterator var23 = todo.iterator();
while(var23.hasNext()) {
javac_extend.com.sun.tools.javac.comp.Env<AttrContext> env = (javac_extend.com.sun.tools.javac.comp.Env)var23.next();
if (cu == null) {
cu = env.toplevel;
} else if (cu != env.toplevel) {
throw new CatastrophicError("Not grouped by file: CUs " + cu + " and " + env.toplevel);
}
}
} while(cu == null);
try {
Queue<javac_extend.com.sun.tools.javac.comp.Env<AttrContext>> queue = compiler.attribute(todo);
String envFlowChecks = System.getenv("CODEQL_EXTRACTOR_JAVA_FLOW_CHECKS");
if (envFlowChecks == null || Boolean.valueOf(envFlowChecks)) {
compiler.flow(queue);
}
break;
} catch (StackOverflowError | Exception var36) {
this.logThrowable(cu, var36);
}
}
try {
CharSequence cachedContent = dfm.getCachedContent(cu.getSourceFile());
if (cachedContent == null) {
try {
cachedContent = cu.getSourceFile().getCharContent(false);
} catch (IOException var37) {
this.logThrowable(cu, var37);
continue;
}
}
String contents = ((CharSequence)cachedContent).toString();
// 抽取解析信息，创建trap文件
(new CompilationUnitExtractor(this.output, cu, this.dw)).process(contents);
} catch (StackOverflowError | Exception var38) {
this.logThrowable(cu, var38);
}
break;
}
}
}
我们进入最后生成trap文件的方法com.semmle.extractor.java.CompilationUnitExtractor#process
里面创建了JavaTrapWriter类型的对象，然后依次调用各种Extractor，抽取信息写入trap文件
public void process(String contents) {
JavaFileObject sourceFile = this.compilationUnit.getSourceFile();
if (sourceFile.getKind() == Kind.SOURCE) {
File file = PathTransformer.std().canonicalFile(sourceFile.getName());
String outputPath = ClassFileLocations.getClassFileLocation(sourceFile.getName()).getOutputPath();
File outputFile = PathTransformer.std().canonicalFile(outputPath);
this.output.setCurrentSourceFile(outputFile);
OdasaOutput.TrapLocker trapLocker = this.output.getTrapLockerForCurrentSourceFile();
try {
// 创建writer
OdasaOutput.JavaTrapWriter writer = trapLocker.getTrapWriter();
try {
if (writer != null) {
OnDemandExtractor onDemand = new OnDemandExtractor(this.output, writer, this.dw);
TreeExtender treeExtender = new TreeExtender(file, contents, this.compilationUnit, this.dw);
// 抽取编译单元信息
this.extractCompilationUnit(contents, writer, onDemand, treeExtender);
Iterator var10 = this.compilationUnit.getTypeDecls().iterator();
while(var10.hasNext()) {
JCTree aClass = (JCTree)var10.next();
if (aClass instanceof JCTree.JCClassDecl) {
// 抽取AST信息
(new ClassDeclExtractor(writer, treeExtender, onDemand, (JCTree.JCClassDecl)aClass, this.compilationUnit, this.dw)).process();
}
}
treeExtender.writeCommentData(writer);
// 抽取类、方法的基本信息以及继承和从属信息
onDemand.extract();
String rootUri = Env.systemEnv().get("CODEQL_EXTRACTOR_JAVA_JSP_ROOT_URI");
String destDir = Env.systemEnv().get("CODEQL_EXTRACTOR_JAVA_JSP_DEST_DIR");
if (rootUri != null && destDir != null) {
String packge = this.compilationUnit.packge.getQualifiedName().toString();
String smapClassName = packge + "/" + FileUtil.basename(outputFile);
(new SmapExtractor(outputFile, smapClassName, destDir, rootUri, this.output, writer, this.dw)).extract();
}
}
} catch (Throwable var16) {
if (writer != null) {
try {
writer.close();
} catch (Throwable var15) {
var16.addSuppressed(var15);
}
}
throw var16;
}
if (writer != null) {
writer.close();
}
} catch (Throwable var17) {
if (trapLocker != null) {
try {
trapLocker.close();
} catch (Throwable var14) {
var17.addSuppressed(var14);
}
}
throw var17;
}
if (trapLocker != null) {
trapLocker.close();
}
}
}
先看extractCompilationUnit方法，它向trap文件写入包名称信息以及导入信息
private void extractCompilationUnit(String contents, TrapWriter writer, OnDemandExtractor onDemand, TreeExtender treeExtender) {
this.output.writeCurrentSourceFileToSourceArchive(contents);
TrapWriter.Label compilationUnitId = treeExtender.writeSourceFile(writer);
TrapWriter.Label packageId = onDemand.getPackageKey(this.compilationUnit.packge);
writer.addTuple(JavaTable.CuPackage, new Object[]{compilationUnitId, packageId});
Iterator var7 = this.compilationUnit.getImports().iterator();
while(var7.hasNext()) {
JCTree.JCImport i = (JCTree.JCImport)var7.next();
classifyImport(treeExtender, writer, onDemand, i);
}
}
然后是com.semmle.extractor.java.ClassDeclExtractor#process方法，它访问整个语法树，向trap文件写入表达式和语句信息
public void process() {
this.log.info("Processing file " + this.compilationUnit.getSourceFile().getName());
this.visitTree(this.classToExtract);
}
然后是com.semmle.extractor.java.OnDemandExtractor#extract方法，其内部会调用
com.semmle.extractor.java.OnDemandExtractor#extractModules
com.semmle.extractor.java.OnDemandExtractor#extractJarInfo
分别抽取模块信息和jar包清单信息
然后调用com.semmle.extractor.java.OnDemandExtractor#extractMembersToCurrentWriter方法，抽取成员变量和成员方法信息
完成分析以后，之前设置的trap目录your-test-dir/trap/java下就会出现多个trap.gz文件，这里我们简单解压一个来分析一下部分内容
源代码
public static void main(String[] args) {
System.out.println("hello");
}
生成结果
#10028=@"callable;{#10007}.main({#10020}){#10009}"
#10029=@"loc,{#10000},2,24,2,27"
locations_default(#10029,#10000,2,24,2,27)
hasLocation(#10028,#10029)
numlines(#10028,3,3,0)
#10030=*
stmts(#10030,0,#10028,0,#10028)
#10031=*
locations_default(#10031,#10000,2,44,4,5)
hasLocation(#10030,#10031)
numlines(#10030,3,3,0)
#10032=*
exprs(#10032,62,#10009,#10028,-1)
callableEnclosingExpr(#10032,#10028)
#10033=*
locations_default(#10033,#10000,2,19,2,22)
hasLocation(#10032,#10033)
numlines(#10032,1,1,0)
#10034=@"params;{#10028};0"
params(#10034,#10020,0,#10028,#10034)
paramName(#10034,"args")
#10035=@"loc,{#10000},2,29,2,41"
locations_default(#10035,#10000,2,29,2,41)
hasLocation(#10034,#10035)
#10036=*
exprs(#10036,63,#10020,#10034,-1)
callableEnclosingExpr(#10036,#10028)
#10037=*
locations_default(#10037,#10000,2,29,2,36)
hasLocation(#10036,#10037)
numlines(#10036,1,1,0)
#10038=*
exprs(#10038,62,#10019,#10036,0)
callableEnclosingExpr(#10038,#10028)
#10039=*
locations_default(#10039,#10000,2,29,2,34)
hasLocation(#10038,#10039)
numlines(#10038,1,1,0)
#10040=*
stmts(#10040,14,#10030,0,#10028)
#10041=*
locations_default(#10041,#10000,3,9,3,36)
hasLocation(#10040,#10041)
numlines(#10040,1,1,0)
#10042=*
exprs(#10042,61,#10009,#10040,0)
callableEnclosingExpr(#10042,#10028)
statementEnclosingExpr(#10042,#10040)
#10043=*
locations_default(#10043,#10000,3,9,3,35)
hasLocation(#10042,#10043)
numlines(#10042,1,1,0)
#10044=*
#10045=@"class;java.io.PrintStream"
exprs(#10044,60,#10045,#10042,-1)
callableEnclosingExpr(#10044,#10028)
statementEnclosingExpr(#10044,#10040)
#10046=*
locations_default(#10046,#10000,3,9,3,18)
hasLocation(#10044,#10046)
numlines(#10044,1,1,0)
#10047=@"callable;{#10045}.println({#10019}){#10009}"
callableBinding(#10042,#10047)
#10048=*
exprs(#10048,22,#10019,#10042,0)
callableEnclosingExpr(#10048,#10028)
statementEnclosingExpr(#10048,#10040)
#10049=*
locations_default(#10049,#10000,3,28,3,34)
hasLocation(#10048,#10049)
numlines(#10048,1,1,0)
#10050=*
#10051=@"class;java.lang.System"
exprs(#10050,62,#10051,#10044,-1)
callableEnclosingExpr(#10050,#10028)
statementEnclosingExpr(#10050,#10040)
#10052=*
locations_default(#10052,#10000,3,9,3,14)
hasLocation(#10050,#10052)
numlines(#10050,1,1,0)
#10053=@"field;{#10051};out"
variableBinding(#10044,#10053)
namestrings("""hello""","hello",#10048)
从最后面的#10050=*开始分析，这里表示刷新标签，无具体含义，但是可以被其他变量绑定为ID
接下来的#10051=@"class;java.lang.System"表示一个全局gloablID，其值为10051
再下来的exprs(#10050,62,#10051,#10044,-1)表示向名为exprs的代码表中插入一条记录，具体记录的含义可以在上面工作流程概览部分里面列举到的文件semmlecode.dbscheme中找到
#keyset[parent,idx]
exprs(
unique int id: @expr,
int kind: int ref,
int typeid: @type ref,
int parent: @exprparent ref,
int idx: int ref
);
对应起来就是id为10050，kind为62，typeid为10051(也就是上面记录的java.lang.System类型)，parent为10044，idx为-1
1.5 finalize
经过了上面几步，trap文件成功地被生成了。接下来就是将trap文件导入到代码数据库中。
现在进入最后的finalize部分，调用链如下
com.semmle.cli2.picocli.SubcommandCommon#runPlumbingInProcess
com.semmle.cli2.picocli.PlumbingRunner#run
com.semmle.cli2.database.FinalizeCommand#executeSubcommand
com.semmle.cli2.database.FinalizeCommand#finalizeOne
我们看finalizeOne方法的实现，它首先运行pre-finalize.sh文件，主要目的是为数据库建立索引。然后调用doTrapImport方法，导入trap文件
private void finalizeOne(DatabaseLayout dbLayout) throws SubcommandDone {
Path databaseDir = dbLayout.getDatabasePath();
if (dbLayout.isFinalized()) {
throw new UserError("Database " + databaseDir + " is already finalized.");
} else if (!Files.exists(dbLayout.getSourceArchiveRoot(), new LinkOption[0])) {
if (this.params.skipEmpty()) {
this.printWarning(this.emptyDatabaseMessage(databaseDir), new Object[0]);
} else {
this.printError(this.emptyDatabaseMessage(databaseDir), new Object[0]);
throw new SubcommandDone(32);
}
} else {
this.foundOneNonEmpty = true;
// 执行pre-finalize.sh
if (!this.params.suppressPreFinalize()) {
dbLayout.getExtractor().getPreFinalizeScript().ifPresent((script) -> {
Path workingDir = Paths.get(dbLayout.getSourceLocationPrefix());
this.printProgress("Running pre-finalize script {} in {}.", new Object[]{script, workingDir});
int result = this.runPlumbingInProcess(TraceCommandCommand.class, new Object[]{"--working-dir=" + workingDir, "--no-tracing", threadsOption(this.importOptions.getThreads()), ramOption(this.importOptions.getRam()), "--", databaseDir, script});
if (result != 0) {
throw new UserError("Failed to execute pre-finalize script in " + databaseDir + " [exit code: " + result + "].");
}
});
}
writeSourceLocationPrefixTrap(dbLayout);
List<Path> trapFolders = Collections.singletonList(dbLayout.getTrapFolder());
doTrapImport(this, dbLayout, this.importOptions, this.privateImportOptions, trapFolders);
dbLayout.markAsFinalized();
if (!this.params.suppressCleanup()) {
this.runPlumbingInProcess(CleanupDatabaseCommand.class, new Object[]{this.params.cleanupParams, "--", databaseDir});
}
}
}
接着看到doTrapImport方法，里面先获取数据库的schmema文件，然后继续调用import指令
static void doTrapImport(SubcommandCommon owner, DatabaseLayout dbLayout, ImportOptions importOptions, PrivateImportOptions privateImportOptions, List<Path> trapPaths) {
owner.printProgress("Running TRAP import for {}...", new Object[]{dbLayout});
SimpleTimer timer = new SimpleTimer();
Path dbscheme = importOptions.getDbscheme();
if (dbscheme == null) {
Either<Path, String> detectedDbscheme = dbLayout.getExtractor().getDbscheme();
if (!detectedDbscheme.isLeft()) {
throw new UserError((String)detectedDbscheme.getRight());
}
dbscheme = (Path)detectedDbscheme.getLeft();
}
List<Object> importCommandArgs = new ArrayList(Arrays.asList(importOptions.getRam() != null ? ResolveRamCommand.createHeapSizeOption(importOptions.getRam()) : Collections.EMPTY_LIST, "--dbscheme=" + dbscheme, threadsOption(importOptions.getThreads()), privateImportOptions, "--", dbLayout.getDatasetPath()));
importCommandArgs.addAll(trapPaths);
int result;
if (importOptions.getRam() != null) {
result = owner.spawnPlumbingAsChildProcess(ImportCommand.class, (RamOptions)null, importCommandArgs.toArray());
} else {
result = owner.runPlumbingInProcess(ImportCommand.class, importCommandArgs.toArray());
}
if (result != 0) {
throw new UserError("Dataset import for " + dbLayout.getDatasetPath() + " failed with code " + result + ".");
} else {
owner.printProgress("TRAP import complete ({}).", new Object[]{timer});
}
}
import指令的调用栈如下
com.semmle.cli2.picocli.SubcommandCommon#runPlumbingInProcess
com.semmle.cli2.picocli.PlumbingRunner#run
com.semmle.cli2.database.FinalizeCommand#executeSubcommand
com.semmle.cli2.ql.dataset.ImportCommand#executeSubcommand
executeSubcommand的实现如下，构建了一个TrapImporter类型对象，然后调用run方法
protected void executeSubcommand() throws SubcommandDone {
if (Files.exists(this.datasetDir, new LinkOption[0]) && !FileUtil8.isEmptyDirectory(this.datasetDir)) {
if (!Files.isDirectory(this.datasetDir, new LinkOption[]{LinkOption.NOFOLLOW_LINKS})) {
throw new UserError("Dataset " + this.datasetDir + " exists, but is not a directory.");
}
if (!Files.isDirectory((new IMBDiskLayout(this.datasetDir, new Context("default"))).getIdPoolDir(), new LinkOption[0])) {
throw new UserError("Dataset " + this.datasetDir + " has been finalized and does not support further TRAP import.");
}
FileUtil8.strictRecursiveDelete(IMBDiskLayout.getCacheDir(this.datasetDir.resolve("default")));
}
AtomicBoolean hasErrors = new AtomicBoolean(false);
TrapImporter importer = new TrapImporter(new TRAPReaderConfig(this.privateOptions.checkUndefinedLabels(), this.privateOptions.checkUnusedLabels(), this.privateOptions.checkRepeatedLabels(), this.privateOptions.checkRedefinedLabels(), this.privateOptions.checkUseBeforeDefinition(), this.privateOptions.locationInStar(), (error) -> {
hasErrors.set(true);
this.printError(error, new Object[0]);
}), this.datasetDir, "default", new CachingMode(), threadsOptionValue(this.threads));
try {
importer.run(Arrays.asList(this.trapPaths), this.dbscheme);
} catch (Throwable var6) {
try {
importer.close();
} catch (Throwable var5) {
var6.addSuppressed(var5);
}
throw var6;
}
importer.close();
if (this.privateOptions.failOnErrors() && hasErrors.get()) {
this.printError("Aborting as some errors occured during TRAP import.", new Object[0]);
throw new SubcommandDone(2);
}
}
run方法内部最终实现了导入
public void run(List<Path> trapRoots, Path targetDbscheme) {
AtomicInteger totalNumTrapFilesCounter = new AtomicInteger(0);
CancellationToken cancelToken = new CancellationToken();
CompletableFuture<List<TrapTask<LinkTarget[]>>> tasks = this.scanAndLink(trapRoots, totalNumTrapFilesCounter, this.executor);
try {
tasks.thenCompose((taskList) -> {
return ImportTasksProcessor.importTrap(this.loadDbSchemeBinding(targetDbscheme), this.backend, this.executor, this.trapReaderConfig, new LogProgressTracker(totalNumTrapFilesCounter.get()), taskList, cancelToken);
}).join();
} catch (CompletionException var7) {
logger.error("An exception occurred during TRAP import. The database may be partial.", var7);
throw Exceptions.asUnchecked(var7.getCause());
}
this.copyDbSchemeFile(targetDbscheme);
logger.info("Finished importing trap files.");
}
2 无源代码构建数据库
从上面的分析过程中可以看出，CodeQL其实不需要java项目真的可以成功编译，它只需要分析源码获取语法树即可。那么我们可以考虑跳过编译这一步，直接利用semmle-java-extractor.jar生成数据库，这正好可以解决某些场景下，只有反编译出的java源代码，但是不能成功编译的问题。
这里还是以java-sec-code这个项目为例子，为了模拟无源码的环境，下面我们只使用编译好的jar包
下面一共用到三个关键文件夹
/Users/cokeBeer/decompiled：反编译出的源代码的位置/Users/cokeBeer/test：semmle-extractor-java的工作文件夹/Users/coekBeer/nonsource：最终生成数据库的位置
首先用IDEA提供的fernflower反编译工具对java-sec-code-1.0.0.jar进行反编译
java -jar java-decompiler.jar -dgs=1 java-sec-code-1.0.0.jar <your-dst-dir>
这里我使用的目标文件夹为/Uesrs/cokeBeer/decompiled
然后在/Uesrs/cokeBeer/decompiled下找到反编译好的java-sec-code-1.0.0.jar，使用下面指令解压
jar -xvf java-sec-code-1.0.0.jar
然后在解压后的文件里面找到BOOT-INF/classes文件夹，这里面保存了反编译好的项目文件
classes $ tree -L 1
.
├── application.properties
├── banner.txt
├── create_db.sql
├── logback-online.xml
├── mapper
├── org
├── static
├── templates
└── url
下面我们先进行initialize环节，新建一个文件夹nonsource，使用下面的指令初始化数据库
codeql database init -l java --source-root org /Users/cokeBeer/nonsource
这里的source-root参数就设置为上面解压出的源代码文件夹org
回顾我们之前调试的过程，在完成codeql-java-agent.jar的处理以后，test文件夹里面应该出现一个log文件夹，里面保存了调用semmle-extractor-java.jar需要的参数javac.args
log $ tree -L 2
.
├── ext
│ ├── javac.args
│ ├── javac.env
│ ├── javac.orig
│ └── javac.properties
└── javac-errors.log
然后我们可以利用这个文件作为输入，调用semmle-extractor-java.jar
package cokeBeer;
import com.semmle.extractor.java.JavaExtractor;
import java.io.File;
public class RunExtractor {
public static void main(String[] args) {
// 在这里用到了
String argPath="@@@/Users/cokeBeer/test/log/ext/javac.args");
String[] ExtractorArgs=new String[]{"--jdk-version","-1","--javac-args",argPath};
JavaExtractor.main(ExtractorArgs);
}
}
同时需要配置环境变量，说明生成trap文件和src相关文件的位置，注意这里先输出到test文件夹
TRAP_FOLDER=/Users/cokeBeer/test/trap/java
SOURCE_ARCHIVE=/Users/cokeBeer/test/src
我们看一下javac.args的内容
-Xprefer:source
-source
1.8
-target
1.8
-classpath
...
-extdirs
...
-endorseddirs
...
-bootclasspath
...
Test.java
它的最后一行传入了编译的目标，那么我们只需要在这里替换了输入文件，就能正确调用
现在先回到/Users/cokeBeer/decompiled/BOOT-INF/classes文件夹，使用下面指令找到所有需要编译的java文件
find org -name *.java > sources.txt
sources.txt可能是相对目录，可以使用vscode批量替换为绝对目录
/Users/cokeBeer/decompiled/BOOT-INF/classes/org/joychou/imageConfig.java
/Users/cokeBeer/decompiled/BOOT-INF/classes/org/joychou/Application.java
/Users/cokeBeer/decompiled/BOOT-INF/classes/org/joychou/util/LoginUtils.java
/Users/cokeBeer/decompiled/BOOT-INF/classes/org/joychou/util/HttpUtils.java
/Users/cokeBeer/decompiled/BOOT-INF/classes/org/joychou/util/WebUtils.java
...
然后将输入替换为@/Users/cokeBeer/decompiled/BOOT-INF/classes/source.txt
-Xprefer:source
-source
1.8
-target
1.8
-classpath
...
-extdirs
...
-endorseddirs
...
-bootclasspath
...
@/Users/cokeBeer/decompiled/BOOT-INF/classes/source.txt
然后运行之前调试semmle-extractor-java.jar时配置好的代码，即可在/Users/cokeBeer/test/trap/java文件夹下找到trap文件
org $ tree -L 2
.
└── joychou
├── Application.java.set
├── Application.java.trap.gz
├── RMI
├── config
├── controller
├── dao
├── filter
├── imageConfig.java.set
├── imageConfig.java.trap.gz
├── mapper
├── security
└── util
现在trap文件已经生成完毕，最后就是finalize阶段
先将/Users/cokeBeer/test下生成的trap和src文件夹复制到/Users/cokeBeer/nonsource
然后运行下面的指令生成数据库
codeql database finalize '/Users/cokeBeer/nosource'
完成以后/Users/cokeBeer/nonsource目录结构应该如下
nonsource $ tree -L 1
.
├── codeql-database.yml
├── db-java
├── log
└── src.zip
下面到vscode中导入数据库，然后编写一个命令注入的污点分析查询
import java
import semmle.code.java.dataflow.FlowSources
import semmle.code.java.dataflow.TaintTracking
abstract class CommandInjectionSink extends DataFlow::Node {}
private class DefaultCommandInjectionSink extends CommandInjectionSink{
DefaultCommandInjectionSink(){
exists(ConstructorCall cc |cc.getAnArgument()=this.asExpr()|cc.getCallee().getDeclaringType() instanceof TypeProcessBuilder)
}
}
class CommandInjectionConfiguration extends TaintTracking::Configuration {
CommandInjectionConfiguration() { this = "CommandInjection" }
override predicate isSource(DataFlow::Node source) {
source instanceof RemoteFlowSource
}
override predicate isSink(DataFlow::Node sink) {
sink instanceof CommandInjectionSink
}
}
from DataFlow::PathNode source, DataFlow::PathNode sink, CommandInjectionConfiguration conf
where conf.hasFlowPath(source, sink)
select source, sink
成功查询出已知漏洞
commandInjection.ql on nonsource - finished in 0 seconds (1 results) [2022/8/11 18:52:16]
关于这个方案的自动化，waderwu师傅已经实现了，这里附上他的项目extractor-java
3 总结和问题讨论
本文从调试的角度分析了CodeQL数据库构建原理，介绍了CodeQL数据库构建过程中用到的一系列文件和参数的作用和含义。同时也演示了一种绕过编译过程的无源码构建数据库的方案
3.1 问题讨论
1.CodeQL构建数据库的实际过程？
使用java提供的API解析源代码，生成trap文件，导入数据库
2.无源代码构建的适用范围
CodeQL在构建trap文件时只需要解析源代码，不用真正生成类文件，这部分工作属于编译的前端。所以只需要CodeQL调用的API能够成功解析源代码，就能完成无源代码构建。
3.2 参考资料
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