android、ios与服务器端php使用rsa加密解密通讯

http://alunblog.duapp.com/?p=50

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最近做手机项目，服务器端使用的是php，客户端分别有android版及ios版，在部分通讯环节需要对内容进行加密，RSA加密演算法是一种非对称加密演算法，能够较好达到要求，不过如果服务器架设https服务，较为麻烦，系统效率也不高，我们只需要在部分重要接口上使用RSA加密解密就行。

首先，准备工作

下载RSA密钥生成工具openssl，点击下载，解压缩至独立的文件夹，进入其中的bin目录，执行以下命令：

openssl genrsa -out rsa_private_key.pem 1024
 
openssl pkcs8 -topk8 -inform PEM -in rsa_private_key.pem -outform PEM -nocrypt -out private_key.pem
 
openssl rsa -in rsa_private_key.pem -pubout -out rsa_public_key.pem

第一条命令生成原始 RSA私钥文件 rsa_private_key.pem，第二条命令将原始 RSA私钥转换为 pkcs8格式，第三条生成RSA公钥 rsa_public_key.pem
从上面看出通过私钥能生成对应的公钥，因此我们将私钥private_key.pem用在服务器端，公钥发放给android跟ios等前端

第二步，php服务器端，使用openssl方法来进行加密解密类，代码如下：

打开private_key.pem，将上面的$PRIVATE_KEY，替换成private_key.pem的内容即可，服务器端我们只需要使用私钥来加密解密。

第三步，android前端，使用java的Cipher类来实现加密解密类，代码如下：

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.spec.X509EncodedKeySpec;
import javax.crypto.Cipher;
 
import android.util.Base64;
 
/**
 * @author alun (http://alunblog.duapp.com)
 * @version 1.0
 * @created 2013-5-17
 */
public class Rsa {
    private static final String RSA_PUBLICE =
            "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDPZ1Ju6zzYUoL7HYzLgneROyDC" + "\r" +
            "Qf/NANWGO42FfXwQinYVSpqnmtukGLsOhVuwdNH6aRFE0ms3bkpp/WL4cfVDgnCO" + "\r" +
            "+W9J6vRVpuTuD/iqfJd9TNacLCd3Jvg3HhjqxbJeO74fYnYqo/mmyJSeLE5iZg4I" + "\r" +
            "Zm5LPWBZWUp3ULCAZQIDAQAB";
    private static final String ALGORITHM = "RSA";
 
    /**
     * 得到公钥
     * @param algorithm
     * @param bysKey
     * @return
     */
    private static PublicKey getPublicKeyFromX509(String algorithm,
            String bysKey) throws NoSuchAlgorithmException, Exception {
        byte[] decodedKey = Base64.decode(bysKey,Base64.DEFAULT);
        X509EncodedKeySpec x509 = new X509EncodedKeySpec(decodedKey);
 
        KeyFactory keyFactory = KeyFactory.getInstance(algorithm);
        return keyFactory.generatePublic(x509);
    }
 
    /**
     * 使用公钥加密
     * @param content
     * @param key
     * @return
     */
    public static String encryptByPublic(String content) {
        try {
            PublicKey pubkey = getPublicKeyFromX509(ALGORITHM, RSA_PUBLICE);
 
            Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
            cipher.init(Cipher.ENCRYPT_MODE, pubkey);
 
            byte plaintext[] = content.getBytes("UTF-8");
            byte[] output = cipher.doFinal(plaintext);
 
            String s = new String(Base64.encode(output,Base64.DEFAULT));
 
            return s;
 
        } catch (Exception e) {
            return null;
        }
    }
 
    /**
    * 使用公钥解密
    * @param content 密文
    * @param key 商户私钥
    * @return 解密后的字符串
    */
    public static String decryptByPublic(String content) {
        try {
            PublicKey pubkey = getPublicKeyFromX509(ALGORITHM, RSA_PUBLICE);
            Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
            cipher.init(Cipher.DECRYPT_MODE, pubkey);
            InputStream ins = new ByteArrayInputStream(Base64.decode(content,Base64.DEFAULT));
            ByteArrayOutputStream writer = new ByteArrayOutputStream();
            byte[] buf = new byte[128];
            int bufl;
            while ((bufl = ins.read(buf)) != -1) {
                byte[] block = null;
                if (buf.length == bufl) {
                block = buf;
                } else {
                block = new byte[bufl];
                for (int i = 0; i < bufl; i++) {
                    block[i] = buf[i];
                }
                }
                writer.write(cipher.doFinal(block));
            }
            return new String(writer.toByteArray(), "utf-8");
        } catch (Exception e) {
            return null;
        }
    }
 
}

需要注意的是，在初始化Cipher对象时，一定要指明使用"RSA/ECB/PKCS1Padding"格式如Cipher.getInstance("RSA/ECB/PKCS1Padding");
打开rsa_public_key.pem文件，将上面代码的RSA_PUBLICE替换成其中内容即可。

第四步，ios前端，iOS上没有直接处理RSA加密的API，网上说的大多数也是处理X.509的证书的方法来实现，不过X.509证书是带签名的，在php端openssl_pkey_get_private方法获取密钥时，第二个参数需要传签名，而android端实现X.509证书加密解密较为不易，在这里我们利用ios兼容c程序的特点，利用openssl的api实现rsa的加密解密，代码如下：

CRSA.h代码：

#import 
#include 
#include 
#include 
 
typedef enum {
    KeyTypePublic,
    KeyTypePrivate
}KeyType;
 
typedef enum {
    RSA_PADDING_TYPE_NONE       = RSA_NO_PADDING,
    RSA_PADDING_TYPE_PKCS1      = RSA_PKCS1_PADDING,
    RSA_PADDING_TYPE_SSLV23     = RSA_SSLV23_PADDING
}RSA_PADDING_TYPE;
 
@interface CRSA : NSObject{
    RSA *_rsa;
}
+ (id)shareInstance;
- (BOOL)importRSAKeyWithType:(KeyType)type;
- (int)getBlockSizeWithRSA_PADDING_TYPE:(RSA_PADDING_TYPE)padding_type;
- (NSString *) encryptByRsa:(NSString*)content withKeyType:(KeyType)keyType;
- (NSString *) decryptByRsa:(NSString*)content withKeyType:(KeyType)keyType;
@end

CRSA.m代码

#import "CRSA.h"
 
#define BUFFSIZE  1024
#import "Base64.h"
 
#define PADDING RSA_PADDING_TYPE_PKCS1
@implementation CRSA
 
+ (id)shareInstance
{
    static CRSA *_crsa = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _crsa = [[self alloc] init];
    });
    return _crsa;
}
- (BOOL)importRSAKeyWithType:(KeyType)type
{
    FILE *file;
    NSString *keyName = type == KeyTypePublic ? @"public_key" : @"private_key";
    NSString *keyPath = [[NSBundle mainBundle] pathForResource:keyName ofType:@"pem"];
     
    file = fopen([keyPath UTF8String], "rb");
     
    if (NULL != file)
    {
        if (type == KeyTypePublic)
        {
            _rsa = PEM_read_RSA_PUBKEY(file, NULL, NULL, NULL);
            assert(_rsa != NULL);
        }
        else
        {
            _rsa = PEM_read_RSAPrivateKey(file, NULL, NULL, NULL);
            assert(_rsa != NULL);
        }
         
        fclose(file);
         
        return (_rsa != NULL) ? YES : NO;
    }
     
    return NO;
}
 
- (NSString *) encryptByRsa:(NSString*)content withKeyType:(KeyType)keyType
{
    if (![self importRSAKeyWithType:keyType])
         return nil;
     
    int status;
    int length  = [content length];
    unsigned char input[length + 1];
    bzero(input, length + 1);
    int i = 0;
    for (; i < length; i++)
    {
        input[i] = [content characterAtIndex:i];
    }
     
    NSInteger  flen = [self getBlockSizeWithRSA_PADDING_TYPE:PADDING];
     
    char *encData = (char*)malloc(flen);
    bzero(encData, flen);
     
    switch (keyType) {
        case KeyTypePublic:
            status = RSA_public_encrypt(length, (unsigned char*)input, (unsigned char*)encData, _rsa, PADDING);
            break;
             
        default:
            status = RSA_private_encrypt(length, (unsigned char*)input, (unsigned char*)encData, _rsa, PADDING);
            break;
    }
     
    if (status)
    {
        NSData *returnData = [NSData dataWithBytes:encData length:status];
        free(encData);
        encData = NULL;
         
        NSString *ret = [returnData base64EncodedString];
        return ret;
    }
     
    free(encData);
    encData = NULL;
     
    return nil;
}
 
- (NSString *) decryptByRsa:(NSString*)content withKeyType:(KeyType)keyType
{
    if (![self importRSAKeyWithType:keyType])
        return nil;
     
    int status;
 
    NSData *data = [content base64DecodedData];
    int length = [data length];
     
    NSInteger flen = [self getBlockSizeWithRSA_PADDING_TYPE:PADDING];
    char *decData = (char*)malloc(flen);
    bzero(decData, flen);
     
    switch (keyType) {
        case KeyTypePublic:
            status = RSA_public_decrypt(length, (unsigned char*)[data bytes], (unsigned char*)decData, _rsa, PADDING);
            break;
             
        default:
            status = RSA_private_decrypt(length, (unsigned char*)[data bytes], (unsigned char*)decData, _rsa, PADDING);
            break;
    }
     
    if (status)
    {
        NSMutableString *decryptString = [[NSMutableString alloc] initWithBytes:decData length:strlen(decData) encoding:NSASCIIStringEncoding];
        free(decData);
        decData = NULL;
         
        return decryptString;
    }
     
    free(decData);
    decData = NULL;
     
    return nil;
}
 
- (int)getBlockSizeWithRSA_PADDING_TYPE:(RSA_PADDING_TYPE)padding_type
{
    int len = RSA_size(_rsa);
     
    if (padding_type == RSA_PADDING_TYPE_PKCS1 || padding_type == RSA_PADDING_TYPE_SSLV23) {
        len -= 11;
    }
     
    return len;
}
@end

其中openssl api包，我们可以在第一步RSA密钥生成工具openssl的include文件夹中得到，完整代码包请点击这里下载