iOS防重签名

作者: sz_蓝天使者 | 来源:发表于2019-12-24 17:03 被阅读0次

背景：

我们的app发布后，有可能给别人砸壳然后进行重签名。为了加强安全性，我们现在对app进行防重签名的防护。接下来我们一起探讨一下如何防止别人重签名我们的app。
本文防重签名的方法是先从embedded.mobileprovision读取自己app的com.apple.developer.team-identifier中的证明组织单位TeamId，然后在app启动时检测当前app的这个信息与原来的是否相同，不同则闪退（当然我们也可以记录下用户行为，把当前收集用户的相关信息上报到服务器，然后再决定如何处理）。

技术要点：

1.关键字符串用函数替换，达到在二进制文件中查看不到的效果；
2.关键函数名用C语言写，这样用Class-dump等工具查不出函数名;
3.闪退的代码用汇编写，这样在编译后的二进制文件中找不到exit的关键字
4.关键函数名用不规则字符串替换，达到混淆效果，别人更难破解（慎用，上架可能被拒）

如何实现

1.先查看一下当前app的查看证明组织单位,在本地的证书中可以查看，如下图：

image.png

或者进入.app的包内容，查看embedded.mobileprovision信息security cms -D -i embedded.mobileprovision 找到<key>com.apple.developer.team-identifier</key>的value的就是（即<NSString>与</NSString>中间那一串字符）

image.png

2.利用签名信息进行重签名防护,以下方法是检测当前从com.apple.developer.team-identifier的Teamid与上面我们查出的Teamid是否相同，不同则调用汇编执行exit(0)，用subStr1()返回字符串替换embedde等

void  checkCodesign(NSString *teamId){
    // 描述文件路径
    NSString *embeddedPath = [[NSBundle mainBundle] pathForResource:@"embedded" ofType:@"mobileprovision"];
    // 读取com.apple.developer.team-identifier  注意描述文件的编码要使用:NSASCIIStringEncoding
    NSString *embeddedProvisioning = [NSString stringWithContentsOfFile:embeddedPath encoding:NSASCIIStringEncoding error:nil];
    NSArray *embeddedProvisioningLines = [embeddedProvisioning componentsSeparatedByCharactersInSet:[NSCharacterSet newlineCharacterSet]];
    
    for (int i = 0; i < embeddedProvisioningLines.count; i++) {
        if ([embeddedProvisioningLines[i] rangeOfString:@"com.apple.developer.team-identifier"].location != NSNotFound) {
            
            NSInteger fromPosition = [embeddedProvisioningLines[i+1] rangeOfString:@"<string>"].location+8;
            
            NSInteger toPosition = [embeddedProvisioningLines[i+1] rangeOfString:@"</string>"].location;
            
            NSRange range;
            range.location = fromPosition;
            range.length = toPosition - fromPosition;
            
            NSString *fullIdentifier = [embeddedProvisioningLines[i+1] substringWithRange:range];
            //NSArray *identifierComponents = [fullIdentifier componentsSeparatedByString:@"."];
          //  NSString *appIdentifier = [identifierComponents firstObject];
       
            // 对比签名ID
            if (![fullIdentifier isEqual:teamId]) {
                //以下等于exit(0)
                asm(
                    "mov X0,#0\n"
                    "mov w16,#1\n"
                    "svc #0x80"
                    );
            }
            break;
        }
    }
}

3.以上方法虽然能达到防止重签名的效果，但是通过hopper，能够查到相关的一些信息，这样别人能通过fishhook等方法绕过这个防护。

image.png

4.为了加强安全性，我们对以上的几个关键的字符串进行了隐藏，比如函数checkCodesign()改为safeStringHandle(),用subStr3()返回字符串替换application-identifier等等，从而达到让人误以为这个方法是在对字符串处理

//
//  aaasss.m
//  noResign
//
//  Created by caizhongtao on 2019/12/18.
//  Copyright © 2019 admin. All rights reserved.
//

#import "StringExtenHandle.h"

@implementation StringExtenHandleClass

+(void)load{
    NSLog(@"******************* FrameWork load ****************");
    safeStringHandle();
}


//查看embedded.mobileprovision信息security cms -D -i embedded.mobileprovision
//找到<key>application-identifier</key>的value的第一部分（即.com 前面的字条串）
#define Str_Key 0xAD
//把字符串3748LX2W73变成函数隐藏原来的字符串
//以下实际返回3748LX2W73
//23P8M9VEK5
static NSString *subStr4(){
    unsigned char key[] = {//用异或^运算进行加密
        (Str_Key ^ '2'),
        (Str_Key ^'3'),
        (Str_Key ^'P'),
        (Str_Key ^'8'),
        (Str_Key ^'M'),
        (Str_Key ^'9'),
        (Str_Key ^'V'),
        (Str_Key ^'E'),
        (Str_Key ^'K'),
        (Str_Key ^'5'),
        (Str_Key ^'\0'),
    };
    
    //用异或^运算进行解密
    unsigned char *p = key;
    while (((*p) ^= Str_Key) != '\0') {
        p++;
    };
    
    return [NSString stringWithUTF8String:(const char *)key];
}

//以下实际返回 embedded
static NSString *subStr1(){
    unsigned char key[] = {//用异或^运算进行加密
        (Str_Key ^'e'),
        (Str_Key ^'m'),
        (Str_Key ^'b'),
        (Str_Key ^'e'),
        (Str_Key ^'d'),
        (Str_Key ^'d'),
        (Str_Key ^'e'),
        (Str_Key ^'d'),
        (Str_Key ^'\0'),
    };
    
    //用异或^运算进行解密
    unsigned char *p = key;
    while (((*p) ^= Str_Key) != '\0') {
        p++;
    };
    
    return [NSString stringWithUTF8String:(const char *)key];
}

//以下实际返回 mobileprovision
static NSString *subStr2(){
    unsigned char key[] = {//用异或^运算进行加密
        (Str_Key ^'m'),
        (Str_Key ^'o'),
        (Str_Key ^'b'),
        (Str_Key ^'i'),
        (Str_Key ^'l'),
        (Str_Key ^'e'),
        (Str_Key ^'p'),
        (Str_Key ^'r'),
        (Str_Key ^'o'),
        (Str_Key ^'v'),
        (Str_Key ^'i'),
        (Str_Key ^'s'),
        (Str_Key ^'i'),
        (Str_Key ^'o'),
        (Str_Key ^'n'),
        (Str_Key ^'\0'),
    };
    
    //用异或^运算进行解密
    unsigned char *p = key;
    while (((*p) ^= Str_Key) != '\0') {
        p++;
    };
    
    return [NSString stringWithUTF8String:(const char *)key];
}


//以下实际返回  application-identifier
static NSString *subStr5(){
    unsigned char key[] = {//用异或^运算进行加密
        (Str_Key ^'a'),
        (Str_Key ^'p'),
        (Str_Key ^'p'),
        (Str_Key ^'l'),
        (Str_Key ^'i'),
        (Str_Key ^'c'),
        (Str_Key ^'a'),
        (Str_Key ^'t'),
        (Str_Key ^'i'),
        (Str_Key ^'o'),
        (Str_Key ^'n'),
        (Str_Key ^'-'),
        (Str_Key ^'i'),
        (Str_Key ^'d'),
        (Str_Key ^'e'),
        (Str_Key ^'n'),
        (Str_Key ^'t'),
        (Str_Key ^'i'),
        (Str_Key ^'f'),
        (Str_Key ^'i'),
        (Str_Key ^'e'),
        (Str_Key ^'r'),
        (Str_Key ^'\0'),
    };
    
    //用异或^运算进行解密
    unsigned char *p = key;
    while (((*p) ^= Str_Key) != '\0') {
        p++;
    };
    
    return [NSString stringWithUTF8String:(const char *)key];
}

//以下实际返回  //com.apple.developer.team-identifier
static NSString *subStr3(){
    unsigned char key[] = {//用异或^运算进行加密
        (Str_Key ^'c'),
        (Str_Key ^'o'),
        (Str_Key ^'m'),
        (Str_Key ^'.'),
        (Str_Key ^'a'),
        (Str_Key ^'p'),
        (Str_Key ^'p'),
        (Str_Key ^'l'),
        (Str_Key ^'e'),
        (Str_Key ^'.'),
        
        (Str_Key ^'d'),
        (Str_Key ^'e'),
        (Str_Key ^'v'),
        (Str_Key ^'e'),
        (Str_Key ^'l'),
        (Str_Key ^'o'),
        (Str_Key ^'p'),
        (Str_Key ^'e'),
        (Str_Key ^'r'),
        (Str_Key ^'.'),
        
        (Str_Key ^'t'),
        (Str_Key ^'e'),
        (Str_Key ^'a'),
        (Str_Key ^'m'),

        
        (Str_Key ^'-'),
        (Str_Key ^'i'),
        (Str_Key ^'d'),
        (Str_Key ^'e'),
        (Str_Key ^'n'),
        (Str_Key ^'t'),
        (Str_Key ^'i'),
        (Str_Key ^'f'),
        (Str_Key ^'i'),
        (Str_Key ^'e'),
        (Str_Key ^'r'),
        (Str_Key ^'\0'),
    };
    
    //用异或^运算进行解密
    unsigned char *p = key;
    while (((*p) ^= Str_Key) != '\0') {
        p++;
    };
    
    return [NSString stringWithUTF8String:(const char *)key];
}


//以下函数名实为checkCodesign(),但为了安全故意伪装成字符串处理函数
void   safeStringHandle(void){
    // 描述文件路径
    NSString *embeddedPath = [[NSBundle mainBundle] pathForResource:subStr1() ofType:subStr2()];
    // 读取application-identifier  注意描述文件的编码要使用:NSASCIIStringEncoding
    NSString *embeddedProvisioning = [NSString stringWithContentsOfFile:embeddedPath encoding:NSASCIIStringEncoding error:nil];
    NSArray *embeddedProvisioningLines = [embeddedProvisioning componentsSeparatedByCharactersInSet:[NSCharacterSet newlineCharacterSet]];

    for (int i = 0; i < embeddedProvisioningLines.count; i++) {
        if ([embeddedProvisioningLines[i] rangeOfString:subStr3()].location != NSNotFound) {

            NSInteger fromPosition = [embeddedProvisioningLines[i+1] rangeOfString:@"<string>"].location+8;

            NSInteger toPosition = [embeddedProvisioningLines[i+1] rangeOfString:@"</string>"].location;

            NSRange range;
            range.location = fromPosition;
            range.length = toPosition - fromPosition;

            NSString *fullIdentifier = [embeddedProvisioningLines[i+1] substringWithRange:range];
//            NSArray *identifierComponents = [fullIdentifier componentsSeparatedByString:@"."];
//            NSString *appIdentifier = [identifierComponents firstObject];

            // 对比签名ID
            if (![fullIdentifier isEqual:subStr4()]) {
                //exit(0)
            #ifdef __arm64__
                asm volatile(
                    "mov X0,#0\n"
                    "mov x16,#1\n"
                    "svc #0x80"
                    );
            #endif

            #ifdef __arm__
                asm volatile(
                    "mov r0,#0\n"
                    "mov r12,#1\n"
                    "svc #80"
                    );
            #endif
            }
            break;
        }
    }
}
@end

效果如下：

image.png

5.为了进一步加强安全性，我们也可以对以上几个重要的方法名进行重命名为不规则的名字,此方法用的是预编译的头文件。在编译的过程会把我们自己的函数转换成不规则的字符串，在编译后的二进制文件中就看不到我们原来的函数。（注：有网友提醒这种方法名混淆有可能审核不通过，所以这种头文件混淆请大家结合实际使用）

#ifndef PrefixHeader_pch
#define PrefixHeader_pch

#define   StringExtenHandleClass dedfsdE3Fjytlks
#define   safeStringHandle    dijSD9fojdfksjzDSdf
#define   subStr1        gsrjzs684zfgjt5afsFse
#define   subStr2        hFtw4ef5u57zvSgDSf
#define   subStr3        sGEW546UTRdewghfUJ6U65
#define   subStr4        ftkuyy45gkyghdd43tr

#endif /* PrefixHeader_pch */

//====================================================

#import "StringExtenHandle.h"

@implementation StringExtenHandleClass
//查看embedded.mobileprovision信息security cms -D -i embedded.mobileprovision
//找到<key>application-identifier</key>的value的第一部分（即.com 前面的字条串）
#define Str_Key 0xAD
//把字符串3748LX2W73变成函数隐藏原来的字符串
//以下实际返回3748LX2W75
static NSString *subStr4(){
    unsigned char key[] = {//用异或^运算进行加密
        (Str_Key ^ '3'),
        (Str_Key ^'7'),
        (Str_Key ^'4'),
        (Str_Key ^'8'),
        (Str_Key ^'L'),
        (Str_Key ^'X'),
        (Str_Key ^'2'),
        (Str_Key ^'W'),
        (Str_Key ^'7'),
        (Str_Key ^'5'),
        (Str_Key ^'\0'),
    };
    
    //用异或^运算进行解密
    unsigned char *p = key;
    while (((*p) ^= Str_Key) != '\0') {
        p++;
    };
    
    return [NSString stringWithUTF8String:(const char *)key];
}

//以下实际返回 embedded
static NSString *subStr1(){
    unsigned char key[] = {//用异或^运算进行加密
        (Str_Key ^'e'),
        (Str_Key ^'m'),
        (Str_Key ^'b'),
        (Str_Key ^'e'),
        (Str_Key ^'d'),
        (Str_Key ^'d'),
        (Str_Key ^'e'),
        (Str_Key ^'d'),
        (Str_Key ^'\0'),
    };
    
    //用异或^运算进行解密
    unsigned char *p = key;
    while (((*p) ^= Str_Key) != '\0') {
        p++;
    };
    
    return [NSString stringWithUTF8String:(const char *)key];
}

//以下实际返回 mobileprovision
static NSString *subStr2(){
    unsigned char key[] = {//用异或^运算进行加密
        (Str_Key ^'m'),
        (Str_Key ^'o'),
        (Str_Key ^'b'),
        (Str_Key ^'i'),
        (Str_Key ^'l'),
        (Str_Key ^'e'),
        (Str_Key ^'p'),
        (Str_Key ^'r'),
        (Str_Key ^'o'),
        (Str_Key ^'v'),
        (Str_Key ^'i'),
        (Str_Key ^'s'),
        (Str_Key ^'i'),
        (Str_Key ^'o'),
        (Str_Key ^'n'),
        (Str_Key ^'\0'),
    };
    
    //用异或^运算进行解密
    unsigned char *p = key;
    while (((*p) ^= Str_Key) != '\0') {
        p++;
    };
    
    return [NSString stringWithUTF8String:(const char *)key];
}

//以下实际返回  //com.apple.developer.team-identifier
static NSString *subStr3(){
    unsigned char key[] = {//用异或^运算进行加密
        (Str_Key ^'c'),
        (Str_Key ^'o'),
        (Str_Key ^'m'),
        (Str_Key ^'.'),
        (Str_Key ^'a'),
        (Str_Key ^'p'),
        (Str_Key ^'p'),
        (Str_Key ^'l'),
        (Str_Key ^'e'),
        (Str_Key ^'.'),
        
        (Str_Key ^'d'),
        (Str_Key ^'e'),
        (Str_Key ^'v'),
        (Str_Key ^'e'),
        (Str_Key ^'l'),
        (Str_Key ^'o'),
        (Str_Key ^'p'),
        (Str_Key ^'e'),
        (Str_Key ^'r'),
        (Str_Key ^'.'),
        
        (Str_Key ^'t'),
        (Str_Key ^'e'),
        (Str_Key ^'a'),
        (Str_Key ^'m'),

        
        (Str_Key ^'-'),
        (Str_Key ^'i'),
        (Str_Key ^'d'),
        (Str_Key ^'e'),
        (Str_Key ^'n'),
        (Str_Key ^'t'),
        (Str_Key ^'i'),
        (Str_Key ^'f'),
        (Str_Key ^'i'),
        (Str_Key ^'e'),
        (Str_Key ^'r'),
        (Str_Key ^'\0'),
    };
    
    //用异或^运算进行解密
    unsigned char *p = key;
    while (((*p) ^= Str_Key) != '\0') {
        p++;
    };
    
    return [NSString stringWithUTF8String:(const char *)key];
}


//以下函数名实为checkCodesign(),但为了安全故意伪装成字符串处理函数
void   safeStringHandle(){
    // 描述文件路径
    NSString *embeddedPath = [[NSBundle mainBundle] pathForResource:subStr1() ofType:subStr2()];
    // 读取application-identifier  注意描述文件的编码要使用:NSASCIIStringEncoding
    NSString *embeddedProvisioning = [NSString stringWithContentsOfFile:embeddedPath encoding:NSASCIIStringEncoding error:nil];
    NSArray *embeddedProvisioningLines = [embeddedProvisioning componentsSeparatedByCharactersInSet:[NSCharacterSet newlineCharacterSet]];
    
    for (int i = 0; i < embeddedProvisioningLines.count; i++) {
        if ([embeddedProvisioningLines[i] rangeOfString:subStr3()].location != NSNotFound) {
            
            NSInteger fromPosition = [embeddedProvisioningLines[i+1] rangeOfString:@"<string>"].location+8;
            
            NSInteger toPosition = [embeddedProvisioningLines[i+1] rangeOfString:@"</string>"].location;
            
            NSRange range;
            range.location = fromPosition;
            range.length = toPosition - fromPosition;
            
            NSString *fullIdentifier = [embeddedProvisioningLines[i+1] substringWithRange:range];
            NSArray *identifierComponents = [fullIdentifier componentsSeparatedByString:@"."];
            NSString *appIdentifier = [identifierComponents firstObject];
            
            // 对比签名ID
            if (![appIdentifier isEqual:subStr4()]) {
                   //exit(0)
            #ifdef __arm64__
                asm volatile(
                    "mov X0,#0\n"
                    "mov x16,#1\n"
                    "svc #0x80"
                    );
            #endif

            #ifdef __arm__
                asm volatile(
                    "mov r0,#0\n"
                    "mov r12,#1\n"
                    "svc #80"
                    );
            #endif
            }
            break;
        }
    }
}
@end

（特别注意：创建PreHeader文件后，一定要在BuilderSetting中添加到预处理中，不然这个文件不会生效）