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[原创]android JNI静态注册和动态注册
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发表于: 2021-9-28 20:46
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这几天在摸android的题目, 在XCTF里面做了一个ONLOAD来动态注册native的题目, 但是本身ida的export能够找到对应native函数名. 想找找ONLOAD注册方法和直接调用的区别, 就仔细去翻了一些相关的帖子.
这个OnLoad注册了一个名为CheckFlag的方法.
native方法分为静态注册和动态注册两种.(我的环境是java16)
因为注册的过程不太好调, 可能会有问题, 如果有错误请师傅们提出来, 我好及时改进.
java的每个方法都会有一个Method对象, 而这个Method对象有两个成员:nativeFunc和insns.
当java构建这个native方法时, 会将该方法对应的Method对象的nativeFunc成员设置为dvmResolveNativeMethod, dvmResolveNativeMethod方法会按照方法的名称去查找对应的C方法.
lookupSharedLibMethod函数用来查找SO层里面的方法, 再看下lookupSharedLibMethod代码
dvmHashForeach的注释是
findMethodInLib:
最终通过调用dlsym来查找so文件里面的方法, 这和windows的GetProAddress()很类似了.
在dvmResolveNativeMethod找到对应的方法后, 会对native方法对应的方法对象进行再一次赋值,
nativeFunc = dvmCallJNIMethod, insns = 找到的so中的方法地址.
dvmCallJNIMethod方法是一个bridge方法, 这个方法的作用就是调用insns对应的方法
当native方法对象构建好了之后, nativeFunc中已经有值, 这样就会直接执行nativeFunc方法
动态注册是将RegisterNatives放在OnLoad方法里面, 在加载库的时候, 会通过dlsym调用Onload方法.
System.java:
Runtime.class:
ClassLoader.loadLibrary:
libs.loadLibrary():
findFromPaths():
loadLibrary():
然后发现居然最后调用了一个native :
NativeLibraries.c:
findJniFunction:
buildJniFunctionName:
JVM_FindLibraryEntry中调用了dlsym()
然后在Onload里面写RegisterNatives方法就可以进行方法注册:
RegisterNatives的第二个参数为JNINativeMethod类型, 这个类型的定义为:
最后对native方法对应的方法对象进行赋值, 和静态注册类似
nativeFunc = dvmCallJNIMethod, insns = 找到的so中的方法地址.
最后可以总结一些, 在静态注册的时候,感觉和windows的iat加载有点类似, 一个是通过GetProAddress()查找DLL的EAT来实现,一个是通过通过dlsym寻找动态符号表.动态注册的时候, 是事先对结构体中的函数指针进行赋值, 通过RegisterNatives进行注册.当注册好了之后, native方法对应的方法对象的成员nativeFunc==dvmCallJNIMethod, 就不会在再设置为dvmResolveNativeMethod, 而是直接执行vmCallJNIMethod, 调用insns的方法.
void dvmResolveNativeMethod(const u4* args, JValue* pResult,
const Method* method, Thread* self)
{ ClassObject* clazz = method->clazz;
/*
* If this is a static method, it could be called before the class
* has been initialized.
*/
if (dvmIsStaticMethod(method)) {
if (!dvmIsClassInitialized(clazz) && !dvmInitClass(clazz)) {
assert(dvmCheckException(dvmThreadSelf()));
return;
}
} else {
assert(dvmIsClassInitialized(clazz) ||
dvmIsClassInitializing(clazz));
}
/* start with our internal-native methods */
DalvikNativeFunc infunc = dvmLookupInternalNativeMethod(method);
if (infunc != NULL) {
/* resolution always gets the same answer, so no race here */
IF_LOGVV() {
char* desc = dexProtoCopyMethodDescriptor(&method->prototype);
LOGVV("+++ resolved native %s.%s %s, invoking",
clazz->descriptor, method->name, desc);
free(desc);
}
if (dvmIsSynchronizedMethod(method)) {
ALOGE("ERROR: internal-native can't be declared 'synchronized'");
ALOGE("Failing on %s.%s", method->clazz->descriptor, method->name);
dvmAbort(); // harsh, but this is VM-internal problem
}
DalvikBridgeFunc dfunc = (DalvikBridgeFunc) infunc;
dvmSetNativeFunc((Method*) method, dfunc, NULL);
dfunc(args, pResult, method, self);
return;
}
/* now scan any DLLs we have loaded for JNI signatures */
void* func = lookupSharedLibMethod(method);
if (func != NULL) {
/* found it, point it at the JNI bridge and then call it */
dvmUseJNIBridge((Method*) method, func);
(*method->nativeFunc)(args, pResult, method, self);
return;
}
IF_ALOGW() {
char* desc = dexProtoCopyMethodDescriptor(&method->prototype);
ALOGW("No implementation found for native %s.%s:%s",
clazz->descriptor, method->name, desc);
free(desc);
}
dvmThrowUnsatisfiedLinkError("Native method not found", method);
}void dvmResolveNativeMethod(const u4* args, JValue* pResult,
const Method* method, Thread* self)
{ ClassObject* clazz = method->clazz;
/*
* If this is a static method, it could be called before the class
* has been initialized.
*/
if (dvmIsStaticMethod(method)) {
if (!dvmIsClassInitialized(clazz) && !dvmInitClass(clazz)) {
assert(dvmCheckException(dvmThreadSelf()));
return;
}
} else {
assert(dvmIsClassInitialized(clazz) ||
dvmIsClassInitializing(clazz));
}
/* start with our internal-native methods */
DalvikNativeFunc infunc = dvmLookupInternalNativeMethod(method);
if (infunc != NULL) {
/* resolution always gets the same answer, so no race here */
IF_LOGVV() {
char* desc = dexProtoCopyMethodDescriptor(&method->prototype);
LOGVV("+++ resolved native %s.%s %s, invoking",
clazz->descriptor, method->name, desc);
free(desc);
}
if (dvmIsSynchronizedMethod(method)) {
ALOGE("ERROR: internal-native can't be declared 'synchronized'");
ALOGE("Failing on %s.%s", method->clazz->descriptor, method->name);
dvmAbort(); // harsh, but this is VM-internal problem
}
DalvikBridgeFunc dfunc = (DalvikBridgeFunc) infunc;
dvmSetNativeFunc((Method*) method, dfunc, NULL);
dfunc(args, pResult, method, self);
return;
}
/* now scan any DLLs we have loaded for JNI signatures */
void* func = lookupSharedLibMethod(method);
if (func != NULL) {
/* found it, point it at the JNI bridge and then call it */
dvmUseJNIBridge((Method*) method, func);
(*method->nativeFunc)(args, pResult, method, self);
return;
}
IF_ALOGW() {
char* desc = dexProtoCopyMethodDescriptor(&method->prototype);
ALOGW("No implementation found for native %s.%s:%s",
clazz->descriptor, method->name, desc);
free(desc);
}
dvmThrowUnsatisfiedLinkError("Native method not found", method);
}static void* lookupSharedLibMethod(const Method* method)
{ if (gDvm.nativeLibs == NULL) {
ALOGE("Unexpected init state: nativeLibs not ready");
dvmAbort();
}
return (void*) dvmHashForeach(gDvm.nativeLibs, findMethodInLib,
(void*) method);
}static void* lookupSharedLibMethod(const Method* method)
{ if (gDvm.nativeLibs == NULL) {
ALOGE("Unexpected init state: nativeLibs not ready");
dvmAbort();
}
return (void*) dvmHashForeach(gDvm.nativeLibs, findMethodInLib,
(void*) method);
}int dvmHashForeach(HashTable* pHashTable, HashForeachFunc func, void* arg);
/*
* Execute "func" on every entry in the hash table.
*
* If "func" returns 1 detach the entry from the hash table. Does not invoke
* the "free" function.
*
* Returning values other than 0 or 1 from "func" will abort the routine.
*/
int dvmHashForeach(HashTable* pHashTable, HashForeachFunc func, void* arg);
/*
* Execute "func" on every entry in the hash table.
*
* If "func" returns 1 detach the entry from the hash table. Does not invoke
* the "free" function.
*
* Returning values other than 0 or 1 from "func" will abort the routine.
*/
static int findMethodInLib(void* vlib, void* vmethod)
{ const SharedLib* pLib = (const SharedLib*) vlib;
const Method* meth = (const Method*) vmethod;
char* preMangleCM = NULL;
char* mangleCM = NULL;
char* mangleSig = NULL;
char* mangleCMSig = NULL;
void* func = NULL;
int len;
if (meth->clazz->classLoader != pLib->classLoader) {
ALOGV("+++ not scanning '%s' for '%s' (wrong CL)",
pLib->pathName, meth->name);
return 0;
} else
ALOGV("+++ scanning '%s' for '%s'", pLib->pathName, meth->name);
/*
* First, we try it without the signature.
*/
preMangleCM =
createJniNameString(meth->clazz->descriptor, meth->name, &len);
if (preMangleCM == NULL)
goto bail;
mangleCM = mangleString(preMangleCM, len);
if (mangleCM == NULL)
goto bail;
ALOGV("+++ calling dlsym(%s)", mangleCM);
func = dlsym(pLib->handle, mangleCM);
if (func == NULL) {
mangleSig =
createMangledSignature(&meth->prototype);
if (mangleSig == NULL)
goto bail;
mangleCMSig = (char*) malloc(strlen(mangleCM) + strlen(mangleSig) +3);
if (mangleCMSig == NULL)
goto bail;
sprintf(mangleCMSig, "%s__%s", mangleCM, mangleSig);
ALOGV("+++ calling dlsym(%s)", mangleCMSig);
func = dlsym(pLib->handle, mangleCMSig);
if (func != NULL) {
ALOGV("Found '%s' with dlsym", mangleCMSig);
}
} else {
ALOGV("Found '%s' with dlsym", mangleCM);
}
bail: free(preMangleCM);
free(mangleCM);
free(mangleSig);
free(mangleCMSig);
return (int) func;
}static int findMethodInLib(void* vlib, void* vmethod)
{ const SharedLib* pLib = (const SharedLib*) vlib;
const Method* meth = (const Method*) vmethod;
char* preMangleCM = NULL;
char* mangleCM = NULL;
char* mangleSig = NULL;
char* mangleCMSig = NULL;
void* func = NULL;
int len;
if (meth->clazz->classLoader != pLib->classLoader) {
ALOGV("+++ not scanning '%s' for '%s' (wrong CL)",
pLib->pathName, meth->name);
return 0;
} else
ALOGV("+++ scanning '%s' for '%s'", pLib->pathName, meth->name);
/*
* First, we try it without the signature.
*/
preMangleCM =
createJniNameString(meth->clazz->descriptor, meth->name, &len);
if (preMangleCM == NULL)
goto bail;
mangleCM = mangleString(preMangleCM, len);
if (mangleCM == NULL)
goto bail;
ALOGV("+++ calling dlsym(%s)", mangleCM);
func = dlsym(pLib->handle, mangleCM);
if (func == NULL) {
mangleSig =
createMangledSignature(&meth->prototype);
if (mangleSig == NULL)
goto bail;
mangleCMSig = (char*) malloc(strlen(mangleCM) + strlen(mangleSig) +3);
if (mangleCMSig == NULL)
goto bail;
sprintf(mangleCMSig, "%s__%s", mangleCM, mangleSig);
ALOGV("+++ calling dlsym(%s)", mangleCMSig);
func = dlsym(pLib->handle, mangleCMSig);
if (func != NULL) {
ALOGV("Found '%s' with dlsym", mangleCMSig);
}
} else {
ALOGV("Found '%s' with dlsym", mangleCM);
}
bail: free(preMangleCM);
free(mangleCM);
free(mangleSig);
free(mangleCMSig);
return (int) func;
}public static void loadLibrary(String libname) { Runtime.getRuntime().loadLibrary0(Reflection.getCallerClass(), libname);
}public static void loadLibrary(String libname) { Runtime.getRuntime().loadLibrary0(Reflection.getCallerClass(), libname);
}void loadLibrary0(Class<?> fromClass, String libname) { SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkLink(libname);
}
if (libname.indexOf((int)File.separatorChar) != -1) {
throw new UnsatisfiedLinkError(
"Directory separator should not appear in library name: " + libname);
}
ClassLoader.loadLibrary(fromClass, libname);
}void loadLibrary0(Class<?> fromClass, String libname) { SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkLink(libname);
}
if (libname.indexOf((int)File.separatorChar) != -1) {
throw new UnsatisfiedLinkError(
"Directory separator should not appear in library name: " + libname);
}
ClassLoader.loadLibrary(fromClass, libname);
}static NativeLibrary loadLibrary(Class<?> fromClass, String name) { ClassLoader loader = (fromClass == null) ? null : fromClass.getClassLoader();
if (loader == null) {
NativeLibrary nl = BootLoader.getNativeLibraries().loadLibrary(fromClass, name);
if (nl != null) {
return nl;
}
throw new UnsatisfiedLinkError("no " + name +
" in system library path: " + StaticProperty.sunBootLibraryPath());
}
NativeLibraries libs = loader.libraries;
// First load from the file returned from ClassLoader::findLibrary, if found.
String libfilename = loader.findLibrary(name);
if (libfilename != null) {
File libfile = new File(libfilename);
if (!libfile.isAbsolute()) {
throw new UnsatisfiedLinkError(
"ClassLoader.findLibrary failed to return an absolute path: " + libfilename);
}
NativeLibrary nl = libs.loadLibrary(fromClass, libfile);
if (nl != null) {
return nl;
}
throw new UnsatisfiedLinkError("Can't load " + libfilename);
}
// Then load from system library path and java library path
NativeLibrary nl = libs.loadLibrary(fromClass, name);
if (nl != null) {
return nl;
}
// Oops, it failed
throw new UnsatisfiedLinkError("no " + name +
" in java.library.path: " + StaticProperty.javaLibraryPath());
}static NativeLibrary loadLibrary(Class<?> fromClass, String name) { ClassLoader loader = (fromClass == null) ? null : fromClass.getClassLoader();
if (loader == null) {
NativeLibrary nl = BootLoader.getNativeLibraries().loadLibrary(fromClass, name);
if (nl != null) {
return nl;
}
throw new UnsatisfiedLinkError("no " + name +
" in system library path: " + StaticProperty.sunBootLibraryPath());
}
NativeLibraries libs = loader.libraries;
// First load from the file returned from ClassLoader::findLibrary, if found.
String libfilename = loader.findLibrary(name);
if (libfilename != null) {
File libfile = new File(libfilename);
if (!libfile.isAbsolute()) {
throw new UnsatisfiedLinkError(
"ClassLoader.findLibrary failed to return an absolute path: " + libfilename);
}
NativeLibrary nl = libs.loadLibrary(fromClass, libfile);
if (nl != null) {
return nl;
}
throw new UnsatisfiedLinkError("Can't load " + libfilename);
}
// Then load from system library path and java library path
NativeLibrary nl = libs.loadLibrary(fromClass, name);
if (nl != null) {
return nl;
}
// Oops, it failed
throw new UnsatisfiedLinkError("no " + name +
" in java.library.path: " + StaticProperty.javaLibraryPath());
}public NativeLibrary loadLibrary(Class<?> fromClass, String name) { assert name.indexOf(File.separatorChar) < 0;
NativeLibrary lib = findFromPaths(LibraryPaths.SYS_PATHS, fromClass, name);
if (lib == null && searchJavaLibraryPath) {
lib = findFromPaths(LibraryPaths.USER_PATHS, fromClass, name);
}
return lib;
}public NativeLibrary loadLibrary(Class<?> fromClass, String name) { assert name.indexOf(File.separatorChar) < 0;
NativeLibrary lib = findFromPaths(LibraryPaths.SYS_PATHS, fromClass, name);
if (lib == null && searchJavaLibraryPath) {
lib = findFromPaths(LibraryPaths.USER_PATHS, fromClass, name);
}
return lib;
}private NativeLibrary findFromPaths(String[] paths, Class<?> fromClass, String name) { for (String path : paths) {
File libfile = new File(path, System.mapLibraryName(name));
NativeLibrary nl = loadLibrary(fromClass, libfile);
if (nl != null) {
return nl;
}
libfile = ClassLoaderHelper.mapAlternativeName(libfile);
if (libfile != null) {
nl = loadLibrary(fromClass, libfile);
if (nl != null) {
return nl;
}
}
}
return null;
}private NativeLibrary findFromPaths(String[] paths, Class<?> fromClass, String name) { for (String path : paths) {
File libfile = new File(path, System.mapLibraryName(name));
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最后于 2021-9-28 20:48
被margina1编辑
，原因：
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