OC(十二)-加密算法(一)-RSA

今天公司测试,还在等待 bug 降临,闲来无事捯饬一个小问题.
首先絮叨一下 RSA 的前世今生, RSA 是三个作者名字的简称,具体内容请自行百度,加密机制如下:首先生成两个密钥,一个公钥,一个私钥,前者加密,后者解密,客户端和服务器各执一份.当客户端向服务器发送数据的时候,先用公钥加密,再有私钥加签,到了服务器一端,用公钥验签,用私钥解密,然后再往下走.加密是为了安全,加签是为了防止冒充APP 客户端进行请求,导致服务器的瘫痪.
👉安装OpenSSL
使用OpenSSL获取公钥和私钥, OpenSSL 的安装请自行百度.
👉获取公钥,私钥步骤
①生成 pem 文件
openssl:关键字
genrsa:格式
-out:输出到…
privatekey.pem:文件名任意取
1024:文件长度

openssl genrsa -out privatekey.pem 1024

②通过第一步生成的 pem 请求 csr 文件,这里会让你填写一些基本信息,最后一下密码可以选填
req:发出请求
-new:新的
privatekey.pem:👆生成的证书
requestrsacert.csr:证书请求文件

openssl req -new -key privatekey.pem -out requestCert.csr

③ 通过上面两步生成的文件,请求公钥
x509:证书格式
-days:有效时长
3650:10年(随意设置)
-in:放入哪个文件
requestrsacert.csr:👆生成的证书
-signkey:key
private.pem:👆生成的证书
publickey.crt:请求到的公钥

openssl x509 -req -days 3650 -in requestCert.csr -signkey privatekey.pem -out publickey.crt

④ 转换格式将base64转换为 bitcode
-outform:输出格式

openssl x509 -outform der -in publickey.crt -out publickey.der

⑤ 生成p12 私钥文件,会提示输入密码,这个密码是用来在加密是调用私钥的密码
-export:导出

openssl pkcs12 -export -out privatekey.p12 -inkey privatekey.pem -in publickey.crt

👉将公钥和私钥添加到工程中,引入Security.framework,创建对应的类SRSA, 这是我自己命名,你自己也是可以去自己想用的名字.记得设置为 MRC 的模式(-fno-objc-arc)

👉.h

//
//  SRSA.h
//  RSA
//
//  Created by HMC on 2016/11/1.
//  Copyright © 2016年 HMC. All rights reserved.
//
#import <Foundation/Foundation.h>
@interface SRSA : NSObject
/**
 *
 * 加密
 * originalString 原始字符串
 */
+(NSString *)encryptString:(NSString *) originalString;
/**
 *
 * 解密
 *
 * ciphertextString 加密字符串
 */
+(NSString *)decryptString:(NSString *) ciphertextString;
@end

👉.m

//
//  SRSA.m
//  RSA
//
//  Created by HMC on 2016/11/1.
//  Copyright © 2016年 HMC. All rights reserved.
//
#import "SRSA.h"
//私钥的密码
static NSString * pwd = @"123456";
@implementation SRSA
+(NSString *)encryptString:(NSString *)originalString{
    if (!originalString)
        return nil;
    SecKeyRef publicKey = [self getPublicKeyRef];
    size_t cipherBufferSize = SecKeyGetBlockSize(publicKey);
    uint8_t *cipherBuffer = malloc(cipherBufferSize);
    uint8_t *nonce = (uint8_t *) [originalString UTF8String];
    SecKeyEncrypt(publicKey,
                  kSecPaddingPKCS1,
                  nonce,
                  strlen((char *) nonce),
                  &cipherBuffer[0],
                  &cipherBufferSize);
    NSData *encryptedData = [NSData dataWithBytes:cipherBuffer length:cipherBufferSize];
    free(cipherBuffer);
    return [encryptedData base64EncodedStringWithOptions:0];
}
+(NSString *)decryptString:(NSString *)ciphertextString{
    if (!ciphertextString)
        return nil;
    SecKeyRef privateKey = [self getPrivateKeyRef];
    size_t plainBufferSize = SecKeyGetBlockSize(privateKey);
    uint8_t *plainBuffer = malloc(plainBufferSize);
    NSData *incomingData = [[NSData alloc] initWithBase64EncodedString:ciphertextString options:NSDataBase64DecodingIgnoreUnknownCharacters];
    uint8_t *cipherBuffer = (uint8_t *) [incomingData bytes];
    size_t cipherBufferSize = SecKeyGetBlockSize(privateKey);
    SecKeyDecrypt(privateKey,
                  kSecPaddingPKCS1,
                  cipherBuffer,
                  cipherBufferSize,
                  plainBuffer,
                  &plainBufferSize);
    NSData *decryptedData = [NSData dataWithBytes:plainBuffer length:plainBufferSize];
    NSString *originalString = [[NSString alloc] initWithData:decryptedData encoding:NSUTF8StringEncoding];
    [incomingData release];
    free(plainBuffer);
    return originalString;
;
}
//获取公钥
+(SecKeyRef)getPublicKeyRef{
    NSString * path = [[NSBundle mainBundle] pathForResource:@"publickey.der" ofType:nil];
    NSData *certData = [NSData dataWithContentsOfFile:path];
    if (!certData) {
        return nil;
    }
    SecCertificateRef cert = SecCertificateCreateWithData(NULL, (CFDataRef)certData);
    SecKeyRef publicKey = NULL;
    SecTrustRef trust = NULL;
    SecPolicyRef policy = NULL;
    if (cert != NULL) {
        policy = SecPolicyCreateBasicX509();
        if (policy) {
            if (SecTrustCreateWithCertificates((CFTypeRef)cert, policy, &trust) == noErr) {
                SecTrustResultType result;
                if (SecTrustEvaluate(trust, &result) == noErr) {
                    publicKey = SecTrustCopyPublicKey(trust);
                }
            }
        }
    }
    if (policy) CFRelease(policy);
    if (trust) CFRelease(trust);
    if (cert) CFRelease(cert);
    return publicKey;
}
//获取私钥
+(SecKeyRef)getPrivateKeyRef{
    NSString * path = [[NSBundle mainBundle] pathForResource:@"privatekey.p12" ofType:nil];
    NSData *p12Data = [NSData dataWithContentsOfFile:path];
    NSMutableDictionary * options = [[NSMutableDictionary alloc] init];
    SecKeyRef privateKeyRef = NULL;
    //这里的密码改成实际私钥的密码
    [options setObject:pwd forKey:(__bridge id)kSecImportExportPassphrase];
    CFArrayRef items = CFArrayCreate(NULL, 0, 0, NULL);
    OSStatus securityError = SecPKCS12Import((__bridge CFDataRef) p12Data,
                                             (__bridge CFDictionaryRef)options, &items);
    if (securityError == noErr && CFArrayGetCount(items) > 0) {
        CFDictionaryRef identityDict = CFArrayGetValueAtIndex(items, 0);
        SecIdentityRef identityApp =
        (SecIdentityRef)CFDictionaryGetValue(identityDict,
                                             kSecImportItemIdentity);
        securityError = SecIdentityCopyPrivateKey(identityApp, &privateKeyRef);
        if (securityError != noErr) {
            privateKeyRef = NULL;
        }
    }
    CFRelease(items);
    [options release];
    return privateKeyRef;
}
@end

👉调用

//
//  ViewController.m
//  RSA
//
//  Created by HMC on 2016/11/1.
//  Copyright © 2016年 HMC. All rights reserved.
//
#import "ViewController.h"
#import "SRSA.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    NSString * str = [SRSA encryptString:@"I am a Chinese"];
    NSLog(@"加密后:%@",str);
    NSLog(@"%@ 解密后:%@",str,[SRSA decryptString:str]);
}
@end

PS: 客户端的 RSA 是配合后台进行加密解密的,所以也要后台(本文是 Java 的后台)有同样的公钥和私钥,只是格式不同.命令如下:
公钥:

openssl rsa -in privatekey.pem -out publickeyForJava.pem -pubout

私钥

openssl pkcs8 -topk8 -in privatekey.pem -out privatekeyForJava.pem -nocrypt