在网上看到一种方法可以通过在Other Linker Flags中添加：

-Wl,-sectcreate,__RESTRICT,__restrict,/dev/null

的方法来阻止dylib注入。

便动手试了一下，编写一个测试Demo不添加任何linker flags，然后使用theos对其进行hook。

Snip20151110_8

启动后使用image list –o –f 来查看加载的动态库：
[145] 0x0025f000 /Library/MobileSubstrate/MobileSubstrate.dylib(0x000000000025f000)
[152] 0x003c0000 /Library/MobileSubstrate/DynamicLibraries/TestLog.dylib(0x00000000003c0000)
发现我们用来hook编写的dylib已经被加载，自然能看到hook成功的log。
2015-11-10 15:21:50.824 myTest[21906:273137] viewDidLoad — 你已经被我Hook了。。。。。。

然后使用linker flags：

-Wl,-sectcreate,__RESTRICT,__restrict,/dev/null

重新编译生成。

运行后在所有加载的动态库中已找不到hook的dylib，hook失败了，说明这是有效的。

再来看看生成的macho文件多了一个__RESTRICT/__restrict section。

Snip20151110_9

在这里找到了答案：http://www.opensource.apple.com/source/dyld/dyld-210.2.3/src/dyld.cpp

if ( removedCount != 0 ) {        
      dyld::[log](http://www.opengroup.org/onlinepubs/009695399/functions/log.html)("dyld: DYLD_ environment variables being ignored because ");        
      switch (sRestrictedReason) {            
            case restrictedNot:               
             break;            
            case restrictedBySetGUid:                
             dyld::[log](http://www.opengroup.org/onlinepubs/009695399/functions/log.html)("main executable (%s) is setuid or setgid\n", sExecPath);                
            break;            
          case restrictedBySegment:                
            dyld::[log](http://www.opengroup.org/onlinepubs/009695399/functions/log.html)("main executable (%s) has __RESTRICT/__restrict section\n", sExecPath);                
             break;            
          case restrictedByEntitlements:                
            dyld::[log](http://www.opengroup.org/onlinepubs/009695399/functions/log.html)("main executable (%s) is code signed with entitlements\n", sExecPath);                
            break;       
       }    
}

也就是说下面三种情况，可以让环境变量：DYLD_INSERT_LIBRARIES被无视
1.Set restricted status by entitlements
This option is only available to applications on OS X with special entitlements.

2.setuid and setgid
Any application that makes these two calls are going to be marked as restricted by the linker as a security measure.

3.Restricted Segment of Header
The final way to mark a binary as restricted is by telling the linker to add new section to the binary header that is named “__RESTRICT” and has a section named “__restrict” when you compile it.

所以编译生成的含有__RESTRICT/__restrict section的app会忽略DYLD_INSERT_LIBRARIES。

当然解决办法也是有的，把section的名字修改一下即可。
用010 editor打开可执行文件，找到section的名字：

Snip20151110_10

Snip20151110_12

Snip20151110_13

又可以成功注入了！

参考链接：
http://bbs.iosre.com/t/tweak-app-app-tweak/438
http://www.opensource.apple.com/source/dyld/dyld-210.2.3/src/dyld.cpp
http://www.samdmarshall.com/blog/blocking_code_injection_on_ios_and_os_x.html

转自 iOS安全—阻止tweak注入hook api

后记

关于注入linker flags之后通常会出现看不到Hierachy的现象。所以本尊一般会把其放在Release位置。