iOS逆向 06：RSA加密（下）

iOS 底层原理 + 逆向文章汇总

本文主要介绍RSA的代码演示过程

RSA代码演示

前提：准备好公钥、私钥，需要在终端生成（属于自己签名）

证书申请步骤

1、申请CSR文件：keychain -> 证书助理 -> 从证书颁发机构请求证书
2、生成CSR请求文件（证书颁发机构信息 + 公钥）
- 命令：openssl req -new -key private.pem -out rsacert.csr
  
  证书申请步骤-02
3、生成CRT证书（自己签名，没有认证的）
- 命令：openssl x509 -req -days 3650 -in rsacert.csr -signkey private.pem -out rsacert.crt
4、生成der文件
- 命令：openssl x509 -outform der -in rsacert.crt -out rsacert.der
  
  证书申请步骤-04
5、获取p12文件
- 命令：openssl pkcs12 -export -out p.p12 -inkey private.pem -in rsacert.crt
  
  证书申请步骤-05
  
  注：代码中使用der格式

base64编码

base64编码由0-9、a-z、A-Z + /（64个字符）加上 =（表示补零）来组成的文本

终端命令

vi message.txt
base64编码：base64 message.txt -o abc.txt
base64解码：base abc.txt -o 123.txt -D

代码演示

- (void)viewDidLoad {
    [super viewDidLoad];
    
    NSLog(@"en:%@", [self base64Encode:@"A"]);
    NSLog(@"de:%@", [self base64Decode:@"QQ=="]);
    
}

//编码
- (NSString *)base64Encode:(NSString *)string{
    NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];
    return [data base64EncodedStringWithOptions: 0];
}
//解码
- (NSString *)base64Decode:(NSString *)string{
    NSData *data = [[NSData alloc] initWithBase64EncodedString:string options:0];
    return [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
}


en:QQ==
de:A

base64说明

1、base64只适用于表示二进制文件
2、base64编码后，文件数量变多，不适合对大型数据进行编码
3、bse64和数据是一一对应的

代码演示

前提：通过证书申请步骤，准备好p12和der文件

1、创建RSA加解密类：RSACryptor


#import 

@interface RSACryptor : NSObject
    
+ (instancetype)sharedRSACryptor;
    
    /**
     *  生成密钥对
     *
     *  @param keySize 密钥尺寸，可选数值(512/1024/2048)
     */
- (void)generateKeyPair:(NSUInteger)keySize;
    
    /**
     *  加载公钥
     *
     *  @param publicKeyPath 公钥路径
     *
     @code
     # 生成证书
     $ openssl genrsa -out ca.key 1024
     # 创建证书请求
     $ openssl req -new -key ca.key -out rsacert.csr
     # 生成证书并签名
     $ openssl x509 -req -days 3650 -in rsacert.csr -signkey ca.key -out rsacert.crt
     # 转换格式
     $ openssl x509 -outform der -in rsacert.crt -out rsacert.der
     @endcode
     */
- (void)loadPublicKey:(NSString *)publicKeyPath;
    
    /**
     *  加载私钥
     *
     *  @param privateKeyPath p12文件路径
     *  @param password       p12文件密码
     *
     @code
     openssl pkcs12 -export -out p.p12 -inkey ca.key -in rsacert.crt
     @endcode
     */
- (void)loadPrivateKey:(NSString *)privateKeyPath password:(NSString *)password;
    
    /**
     *  加密数据
     *
     *  @param plainData 明文数据
     *
     *  @return 密文数据
     */
- (NSData *)encryptData:(NSData *)plainData;
    
    /**
     *  解密数据
     *
     *  @param cipherData 密文数据
     *
     *  @return 明文数据
     */
- (NSData *)decryptData:(NSData *)cipherData;
@end


#import "RSACryptor.h"

// 填充模式
/*
 - kSecPaddingNone 不填充
 - kSecPaddingPKCS1 填充
 */
#define kTypeOfWrapPadding        kSecPaddingPKCS1

// 公钥/私钥标签
#define kPublicKeyTag            "com.cjl.EncryptDemo.publickey"
#define kPrivateKeyTag            "com.cjl.EncryptDemo.privatekey"

static const uint8_t publicKeyIdentifier[]        = kPublicKeyTag;
static const uint8_t privateKeyIdentifier[]        = kPrivateKeyTag;

@interface RSACryptor() {
    SecKeyRef publicKeyRef;                             // 公钥引用
    SecKeyRef privateKeyRef;                            // 私钥引用
}
    
    @property (nonatomic, retain) NSData *publicTag;        // 公钥标签
    @property (nonatomic, retain) NSData *privateTag;       // 私钥标签
    
    @end

@implementation RSACryptor
    
+ (instancetype)sharedRSACryptor {
    static id instance;
    
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        instance = [[self alloc] init];
    });
    return instance;
}
    
- (instancetype)init {
    self = [super init];
    if (self) {
        // 查询密钥的标签
        _privateTag = [[NSData alloc] initWithBytes:privateKeyIdentifier length:sizeof(privateKeyIdentifier)];
        _publicTag = [[NSData alloc] initWithBytes:publicKeyIdentifier length:sizeof(publicKeyIdentifier)];
    }
    return self;
}
    
#pragma mark - 加密 & 解密数据
- (NSData *)encryptData:(NSData *)plainData {
    OSStatus sanityCheck = noErr;
    size_t cipherBufferSize = 0;
    size_t keyBufferSize = 0;
    
    NSAssert(plainData != nil, @"明文数据为空");
    NSAssert(publicKeyRef != nil, @"公钥为空");
    
    NSData *cipher = nil;
    uint8_t *cipherBuffer = NULL;
    
    // 计算缓冲区大小
    cipherBufferSize = SecKeyGetBlockSize(publicKeyRef);
    keyBufferSize = [plainData length];
    
    if (kTypeOfWrapPadding == kSecPaddingNone) {
        NSAssert(keyBufferSize <= cipherBufferSize, @"加密内容太大");
    } else {
        NSAssert(keyBufferSize <= (cipherBufferSize - 11), @"加密内容太大");
    }
    
    // 分配缓冲区
    cipherBuffer = malloc(cipherBufferSize * sizeof(uint8_t));
    memset((void *)cipherBuffer, 0x0, cipherBufferSize);
    
    // 使用公钥加密
    sanityCheck = SecKeyEncrypt(publicKeyRef,
                                kTypeOfWrapPadding,
                                (const uint8_t *)[plainData bytes],
                                keyBufferSize,
                                cipherBuffer,
                                &cipherBufferSize
                                );
    
    NSAssert(sanityCheck == noErr, @"加密错误，OSStatus == %d", sanityCheck);
    
    // 生成密文数据
    cipher = [NSData dataWithBytes:(const void *)cipherBuffer length:(NSUInteger)cipherBufferSize];
    
    if (cipherBuffer) free(cipherBuffer);
    
    return cipher;
}
    
- (NSData *)decryptData:(NSData *)cipherData {
    OSStatus sanityCheck = noErr;
    size_t cipherBufferSize = 0;
    size_t keyBufferSize = 0;
    
    NSData *key = nil;
    uint8_t *keyBuffer = NULL;
    
    SecKeyRef privateKey = NULL;
    
    privateKey = [self getPrivateKeyRef];
    NSAssert(privateKey != NULL, @"私钥不存在");
    
    // 计算缓冲区大小
    cipherBufferSize = SecKeyGetBlockSize(privateKey);
    keyBufferSize = [cipherData length];
    
    NSAssert(keyBufferSize <= cipherBufferSize, @"解密内容太大");
    
    // 分配缓冲区
    keyBuffer = malloc(keyBufferSize * sizeof(uint8_t));
    memset((void *)keyBuffer, 0x0, keyBufferSize);
    
    // 使用私钥解密
    sanityCheck = SecKeyDecrypt(privateKey,
                                kTypeOfWrapPadding,
                                (const uint8_t *)[cipherData bytes],
                                cipherBufferSize,
                                keyBuffer,
                                &keyBufferSize
                                );
    
    NSAssert1(sanityCheck == noErr, @"解密错误，OSStatus == %d", sanityCheck);
    
    // 生成明文数据
    key = [NSData dataWithBytes:(const void *)keyBuffer length:(NSUInteger)keyBufferSize];
    
    if (keyBuffer) free(keyBuffer);
    
    return key;
}
    
#pragma mark - 密钥处理
    /**
     *  生成密钥对
     */
- (void)generateKeyPair:(NSUInteger)keySize {
    OSStatus sanityCheck = noErr;
    publicKeyRef = NULL;
    privateKeyRef = NULL;
    
    NSAssert1((keySize == 512 || keySize == 1024 || keySize == 2048), @"密钥尺寸无效 %tu", keySize);
    
    // 删除当前密钥对
    [self deleteAsymmetricKeys];
    
    // 容器字典
    NSMutableDictionary *privateKeyAttr = [[NSMutableDictionary alloc] init];
    NSMutableDictionary *publicKeyAttr = [[NSMutableDictionary alloc] init];
    NSMutableDictionary *keyPairAttr = [[NSMutableDictionary alloc] init];
    
    // 设置密钥对的顶级字典
    [keyPairAttr setObject:(__bridge id)kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
    [keyPairAttr setObject:[NSNumber numberWithUnsignedInteger:keySize] forKey:(__bridge id)kSecAttrKeySizeInBits];
    
    // 设置私钥字典
    [privateKeyAttr setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecAttrIsPermanent];
    [privateKeyAttr setObject:_privateTag forKey:(__bridge id)kSecAttrApplicationTag];
    
    // 设置公钥字典
    [publicKeyAttr setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecAttrIsPermanent];
    [publicKeyAttr setObject:_publicTag forKey:(__bridge id)kSecAttrApplicationTag];
    
    // 设置顶级字典属性
    [keyPairAttr setObject:privateKeyAttr forKey:(__bridge id)kSecPrivateKeyAttrs];
    [keyPairAttr setObject:publicKeyAttr forKey:(__bridge id)kSecPublicKeyAttrs];
    
    // SecKeyGeneratePair 返回密钥对引用
    sanityCheck = SecKeyGeneratePair((__bridge CFDictionaryRef)keyPairAttr, &publicKeyRef, &privateKeyRef);
    NSAssert((sanityCheck == noErr && publicKeyRef != NULL && privateKeyRef != NULL), @"生成密钥对失败");
}
    
    /**
     *  加载公钥
     */
- (void)loadPublicKey:(NSString *)publicKeyPath {
    
    NSAssert(publicKeyPath.length != 0, @"公钥路径为空");
    
    // 删除当前公钥
    if (publicKeyRef) CFRelease(publicKeyRef);
    
    // 从一个 DER 表示的证书创建一个证书对象
    NSData *certificateData = [NSData dataWithContentsOfFile:publicKeyPath];
    SecCertificateRef certificateRef = SecCertificateCreateWithData(kCFAllocatorDefault, (__bridge CFDataRef)certificateData);
    NSAssert(certificateRef != NULL, @"公钥文件错误");
    
    // 返回一个默认 X509 策略的公钥对象，使用之后需要调用 CFRelease 释放
    SecPolicyRef policyRef = SecPolicyCreateBasicX509();
    // 包含信任管理信息的结构体
    SecTrustRef trustRef;
    
    // 基于证书和策略创建一个信任管理对象
    OSStatus status = SecTrustCreateWithCertificates(certificateRef, policyRef, &trustRef);
    NSAssert(status == errSecSuccess, @"创建信任管理对象失败");
    
    // 信任结果
    SecTrustResultType trustResult;
    // 评估指定证书和策略的信任管理是否有效
    status = SecTrustEvaluate(trustRef, &trustResult);
    NSAssert(status == errSecSuccess, @"信任评估失败");
    
    // 评估之后返回公钥子证书
    publicKeyRef = SecTrustCopyPublicKey(trustRef);
    NSAssert(publicKeyRef != NULL, @"公钥创建失败");
    
    if (certificateRef) CFRelease(certificateRef);
    if (policyRef) CFRelease(policyRef);
    if (trustRef) CFRelease(trustRef);
}
    
    /**
     *  加载私钥
     */
- (void)loadPrivateKey:(NSString *)privateKeyPath password:(NSString *)password {
    
    NSAssert(privateKeyPath.length != 0, @"私钥路径为空");
    
    // 删除当前私钥
    if (privateKeyRef) CFRelease(privateKeyRef);
    
    NSData *PKCS12Data = [NSData dataWithContentsOfFile:privateKeyPath];
    CFDataRef inPKCS12Data = (__bridge CFDataRef)PKCS12Data;
    CFStringRef passwordRef = (__bridge CFStringRef)password;
    
    // 从 PKCS #12 证书中提取标示和证书
    SecIdentityRef myIdentity;
    SecTrustRef myTrust;
    const void *keys[] =   {kSecImportExportPassphrase};
    const void *values[] = {passwordRef};
    CFDictionaryRef optionsDictionary = CFDictionaryCreate(NULL, keys, values, 1, NULL, NULL);
    CFArrayRef items = CFArrayCreate(NULL, 0, 0, NULL);
    
    // 返回 PKCS #12 格式数据中的标示和证书
    OSStatus status = SecPKCS12Import(inPKCS12Data, optionsDictionary, &items);
    
    if (status == noErr) {
        CFDictionaryRef myIdentityAndTrust = CFArrayGetValueAtIndex(items, 0);
        myIdentity = (SecIdentityRef)CFDictionaryGetValue(myIdentityAndTrust, kSecImportItemIdentity);
        myTrust = (SecTrustRef)CFDictionaryGetValue(myIdentityAndTrust, kSecImportItemTrust);
    }
    
    if (optionsDictionary) CFRelease(optionsDictionary);
    
    NSAssert(status == noErr, @"提取身份和信任失败");
    
    SecTrustResultType trustResult;
    // 评估指定证书和策略的信任管理是否有效
    status = SecTrustEvaluate(myTrust, &trustResult);
    NSAssert(status == errSecSuccess, @"信任评估失败");
    
    // 提取私钥
    status = SecIdentityCopyPrivateKey(myIdentity, &privateKeyRef);
    NSAssert(status == errSecSuccess, @"私钥创建失败");
}
    
    /**
     *  删除非对称密钥
     */
- (void)deleteAsymmetricKeys {
    OSStatus sanityCheck = noErr;
    NSMutableDictionary *queryPublicKey = [[NSMutableDictionary alloc] init];
    NSMutableDictionary *queryPrivateKey = [[NSMutableDictionary alloc] init];
    
    // 设置公钥查询字典
    [queryPublicKey setObject:(__bridge id)kSecClassKey forKey:(__bridge id)kSecClass];
    [queryPublicKey setObject:_publicTag forKey:(__bridge id)kSecAttrApplicationTag];
    [queryPublicKey setObject:(__bridge id)kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
    
    // 设置私钥查询字典
    [queryPrivateKey setObject:(__bridge id)kSecClassKey forKey:(__bridge id)kSecClass];
    [queryPrivateKey setObject:_privateTag forKey:(__bridge id)kSecAttrApplicationTag];
    [queryPrivateKey setObject:(__bridge id)kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
    
    // 删除私钥
    sanityCheck = SecItemDelete((__bridge CFDictionaryRef)queryPrivateKey);
    NSAssert1((sanityCheck == noErr || sanityCheck == errSecItemNotFound), @"删除私钥错误，OSStatus == %d", sanityCheck);
    
    // 删除公钥
    sanityCheck = SecItemDelete((__bridge CFDictionaryRef)queryPublicKey);
    NSAssert1((sanityCheck == noErr || sanityCheck == errSecItemNotFound), @"删除公钥错误，OSStatus == %d", sanityCheck);
    
    if (publicKeyRef) CFRelease(publicKeyRef);
    if (privateKeyRef) CFRelease(privateKeyRef);
}
    
    /**
     *  获得私钥引用
     */
- (SecKeyRef)getPrivateKeyRef {
    OSStatus sanityCheck = noErr;
    SecKeyRef privateKeyReference = NULL;
    
    if (privateKeyRef == NULL) {
        NSMutableDictionary * queryPrivateKey = [[NSMutableDictionary alloc] init];
        
        // 设置私钥查询字典
        [queryPrivateKey setObject:(__bridge id)kSecClassKey forKey:(__bridge id)kSecClass];
        [queryPrivateKey setObject:_privateTag forKey:(__bridge id)kSecAttrApplicationTag];
        [queryPrivateKey setObject:(__bridge id)kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
        [queryPrivateKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecReturnRef];
        
        // 获得密钥
        sanityCheck = SecItemCopyMatching((__bridge CFDictionaryRef)queryPrivateKey, (CFTypeRef *)&privateKeyReference);
        
        if (sanityCheck != noErr) {
            privateKeyReference = NULL;
        }
    } else {
        privateKeyReference = privateKeyRef;
    }
    
    return privateKeyReference;
}
@end

2、通过代码加载公钥（der文件）和私钥（p12文件）

- (void)testRSA{
    //1、加载公钥
    [[RSACryptor sharedRSACryptor] loadPublicKey:[[NSBundle mainBundle] pathForResource:@"rsacert.der" ofType:nil]];
    
    //2、加载私钥
    [[RSACryptor sharedRSACryptor] loadPrivateKey:[[NSBundle mainBundle] pathForResource:@"p.p12" ofType:nil] password:@"123456"];
}

3、使用RSA进行加解密

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
    //加密
    NSData *result = [[RSACryptor sharedRSACryptor] encryptData:[@"hello" dataUsingEncoding:NSUTF8StringEncoding]];
    NSString *base64 = [result base64EncodedStringWithOptions:0];
    NSLog(@"en - %@", base64);
    
    
    //解密
    NSData *jiemi = [[RSACryptor sharedRSACryptor] decryptData:result];
    NSLog(@"de - %@", [[NSString alloc] initWithData:jiemi encoding:NSUTF8StringEncoding]);
}


en - L+1uUQ9eSzZmVJuEXMZ7Z8Wr241ze/6XbKMoBTLDdCvlf2bLcJPDJor5RVvn00rPg65NLwd3AyZDy+4/3t41bAJtHo2+MjmAHJ32rmTTx/HH5B3WOghOGqhLZS1hLFt62tic8betewTgzJg9IvMbtSvXDl4XdgLXM8ZWFdosneg=
de - hello

从结果中可以发现，每次RSA加密结果不一样，原因是因为RSA有个填充模式，导致每次结果不一样

kSecPaddingNone 不填充，密文每次不变
kSecPaddingPKCS1 填充，密文随机变化

RSA加密结果

总结

base64编码说明：
- 1、base64只适用于表示二进制文件
- 2、base64编码后，文件数量变多，不适合对大型数据进行编码
- 3、bse64和数据是一一对应的
RSA代码加解密是通过Security框架
- 加密：使用SecKeyEncrypt函数
- 解密：使用SecKeyDecrypt函数
- 加密有两种填充模式：
  - kSecPaddingNone 不填充，密文每次不变
  - kSecPaddingPKCS1 填充，密文每次随机变化

iOS逆向 06：RSA加密（下）

RSA代码演示

证书申请步骤

base64编码

代码演示

总结

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