iOS安全相关 - iOS中使用RSA加密与解密

作者: brownfeng | 来源:发表于2017-01-17 19:26 被阅读2079次

通常我们使用iOS的RSA加密或者解密时候,有如下几种情况(这里只讨论使用公钥加密的情况):

带公钥的证书
PEM的格式public key(base64编码的PEM格式的公钥)
DER格式的二进制字符串公钥
只有公钥的模n和公开幂e(通常是给的16进制Data数据)

带公钥证书,PEM格式publickey,DER格式的二进制字符串加密方法

iOS能够支持的带公钥的证书只能支持 --- 二进制编码格式的DER的X.509格式的证书.因此如果给予的证书格式是PEM格式,请参考本博客其他的RSA相关的文章,将PEM格式转化成DER格式.

#import "RSAEncryptor.h"
#import <Security/Security.h>

@implementation RSAEncryptor

/**
 讲传入的二进制数据,编码成base64格式的字符串

 @param data 需要编码的二进制数据
 @return base64编码以后的string
 */
static NSString *base64_encode_data(NSData *data){
    data = [data base64EncodedDataWithOptions:0];
    NSString *ret = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    return ret;
}

/**
 将base64编码的String,解码成二进制数据

 @param str base64编码以后的数据
 @return 原始二进制数据
 */
static NSData *base64_decode(NSString *str){
    NSData *data = [[NSData alloc] initWithBase64EncodedString:str options:NSDataBase64DecodingIgnoreUnknownCharacters];
    return data;
}

#pragma mark - 使用'.der'公钥证书文件加密
/**
 公钥加密的核心方法
 传入二进制编码的der格式的带publickey的证书,给str参数的字符串进行RSA加密

 @param str 待加密的字符串
 @param path publickey证书路径
 @return 加密以后的字符串
 */
+ (NSString *)encryptString:(NSString *)str publicKeyWithContentsOfFile:(NSString *)path{
    if (!str || !path)  return nil;
    return [self encryptString:str publicKeyRef:[self getPublicKeyRefWithContentsOfFile:path]];
}

/**
 工具方法
 传入der格式的带有公钥的证书,该方法从证书中获取公钥

 @param filePath 二进制编码的der格式带公钥的证书
 @return 公钥对象
 */
+ (SecKeyRef)getPublicKeyRefWithContentsOfFile:(NSString *)filePath{
    
    // 1. 获取der证书二进制数据
    NSData *certData = [NSData dataWithContentsOfFile:filePath];
    if (!certData) {
        return nil;
    }
    
    // 2. 通过<Security/Security.h>创建SecCertificateRef证书对象(这是c接口,因此需要手动管理对象的释放)
    SecCertificateRef cert = SecCertificateCreateWithData(NULL, (CFDataRef)certData);
    SecKeyRef key = NULL;
    SecTrustRef trust = NULL;
    SecPolicyRef policy = NULL;
    if (cert != NULL) {
        // 3. 根据证书数据,证书策略 -> 信任管理对象, 设置的证书的策略是否是X.509证书(HTTPS中策略使用的是SSL策略)
        policy = SecPolicyCreateBasicX509();
        if (policy) {
            if (SecTrustCreateWithCertificates((CFTypeRef)cert, policy, &trust) == noErr) {
                SecTrustResultType result;
                if (SecTrustEvaluate(trust, &result) == noErr) {
                    // 4. 从证书评估对象中获取公钥SecKeyRef的引用,注意使用的copy,因此需要手动释放
                    key = SecTrustCopyPublicKey(trust);
                }
            }
        }
    }
    if (policy) CFRelease(policy);
    if (trust) CFRelease(trust);
    if (cert) CFRelease(cert);
    return key;
}

/**
 加密核心方法
 传入需要加密的字符串

 @param str 需要加密的字符串
 @param publicKeyRef 公钥SecKeyRef引用对象
 @return 加密以后的数据
 */
+ (NSString *)encryptString:(NSString *)str publicKeyRef:(SecKeyRef)publicKeyRef{
    //1. 参数检查
    if(![str dataUsingEncoding:NSUTF8StringEncoding]){
        return nil;
    }
    if(!publicKeyRef){
        return nil;
    }
    //2. 待加密字符->二进制 -> 加密以后返回二进制加密数据
    NSData *data = [self encryptData:[str dataUsingEncoding:NSUTF8StringEncoding] withKeyRef:publicKeyRef];
    //3. 加密以后二进制数据->base64编码的字符串
    NSString *ret = base64_encode_data(data);
    return ret;
}

#pragma mark - 使用公钥字符串加密
/* START: Encryption with RSA public key */

/**
 使用RSA public key(非证书)进行加密

 @param str 需要加密的字符串
 @param pubKey 公钥字符串(格式PEM格式的publickey字符串)
 @return 返回加密以后的字符串
 */
+ (NSString *)encryptString:(NSString *)str publicKey:(NSString *)pubKey{
    //1.调用核心方法将待加密的字符串转化成二进制数据,返回加密以后的二进制数据
    NSData *data = [self encryptData:[str dataUsingEncoding:NSUTF8StringEncoding] publicKey:pubKey];
    //2.将加密以后的二进制数据通过base64编码以后的string返回,便于传输
    NSString *ret = base64_encode_data(data);
    return ret;
}


/**
 通过PEM格式的public key 加密二进制数据,输出加密以后的二进制数据

 @param data 待加密的二进制数据
 @param pubKey PEM格式的public key
 @return rsa加密以后的二进制数据
 */
+ (NSData *)encryptData:(NSData *)data publicKey:(NSString *)pubKey{
    if(!data || !pubKey){
        return nil;
    }
    //1.将PEM格式的public key数据生成SecKeyRef对象
    SecKeyRef keyRef = [self addPublicKey:pubKey];
    if(!keyRef){
        return nil;
    }
    //2.传入待加密二进制数据和SecKeyRef公钥对象
    return [self encryptData:data withKeyRef:keyRef];
}

/**
 将PEM格式public key的string创建SecKeyRef对象

 @param key PEM格式public key的string
 @return SecKeyRef对象
 */
+ (SecKeyRef)addPublicKey:(NSString *)key{
    //1. 找到PEM格式publickey的头部和尾部
    NSRange spos = [key rangeOfString:@"-----BEGIN PUBLIC KEY-----"];
    NSRange epos = [key rangeOfString:@"-----END PUBLIC KEY-----"];
    //2. 如果找到头部和尾部,那么截取头部尾部之间的部分 -- 真正的有用的public key部分
    if(spos.location != NSNotFound && epos.location != NSNotFound){
        NSUInteger s = spos.location + spos.length;
        NSUInteger e = epos.location;
        NSRange range = NSMakeRange(s, e-s);
        key = [key substringWithRange:range];
    }
    
    //3. 清理PEM格式publickey中的"\r","\n"," "等回车,换行,空格字符
    key = [key stringByReplacingOccurrencesOfString:@"\r" withString:@""];
    key = [key stringByReplacingOccurrencesOfString:@"\n" withString:@""];
    key = [key stringByReplacingOccurrencesOfString:@"\t" withString:@""];
    key = [key stringByReplacingOccurrencesOfString:@" "  withString:@""];
    
    //4. 一般PEM格式公钥字符串是通过base64编码以后的字符串,因此需要从中解码成原始二进制数据,解码以后是DER编码格式的
    NSData *data = base64_decode(key);
    //5. 清理DER格式的publickey的公钥头部信息 -- DER公钥满足ASN.1编码格式,具体参考TLV方式
    data = [self stripPublicKeyHeader:data];
    if(!data){
        return nil;
    }
    
    //6. 下面将使用iOS的keychain中的内容处理公钥
    
    //7. tag表示写入keychain的Tag标签,方便以后从keychain中读写这个公钥
    NSString *tag = @"RSAUtil_PubKey";
    NSData *d_tag = [NSData dataWithBytes:[tag UTF8String] length:[tag length]];
    
    //8. 先删除keychain中的tag同名的对应的key
    NSMutableDictionary *publicKey = [[NSMutableDictionary alloc] init];
    // kSecClass是表示keychain中存储的类型,常见的有kSecClassGenericPassword(一般密码),kSecClassInternetPassword(网络密码),kSecClassCertificate(证书),kSecClassKey(密钥),kSecClassIdentity(带私钥证书)等
    // 不同类型的钥匙串项对应的属性不同,这里使用的kSecClassKey(密钥),对应的属性有许多最重要的是kSecAttrKeyType,表示密钥的类型,这里使用的kSecAttrKeyTypeRSA;
    [publicKey setObject:(__bridge id) kSecClassKey forKey:(__bridge id)kSecClass];
    [publicKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
    [publicKey setObject:d_tag forKey:(__bridge id)kSecAttrApplicationTag];// 设置需要删除的带tag的密钥
    SecItemDelete((__bridge CFDictionaryRef)publicKey);// 先查询keychain中是否有同tag的,直接删除
    
    [publicKey setObject:data forKey:(__bridge id)kSecValueData];//设置keychain的写入字段的类型kSecValueData
    [publicKey setObject:(__bridge id) kSecAttrKeyClassPublic forKey:(__bridge id)
     kSecAttrKeyClass];//设置加密密钥类kSecAttrKeyClassPublic,kSecAttrKeyClassPrivate或者kSecAttrKeyClassSymmetric,这里是公钥
    [publicKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)
     kSecReturnPersistentRef];//设置是否返回持久型实例(CFDataRef)
    
    //9. 讲public key dict通过SecItemAdd添加到keychain中
    CFTypeRef persistKey = nil;
    OSStatus status = SecItemAdd((__bridge CFDictionaryRef)publicKey, &persistKey);
    if (persistKey != nil){
        CFRelease(persistKey);
    }
    if ((status != noErr) && (status != errSecDuplicateItem)) {
        return nil;
    }
    
    [publicKey removeObjectForKey:(__bridge id)kSecValueData];// 清理属性
    [publicKey removeObjectForKey:(__bridge id)kSecReturnPersistentRef];// 清理属性
    [publicKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecReturnRef];//设置返回实例(SecKeychainItemRef, SecKeyRef, SecCertificateRef, SecIdentityRef, or CFDataRef)
    [publicKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];// 这里其实原来已经添加过...
    
    //10. 从keychain中获取SecKeyRef对象
    SecKeyRef keyRef = nil;
    status = SecItemCopyMatching((__bridge CFDictionaryRef)publicKey, (CFTypeRef *)&keyRef);
    if(status != noErr){
        return nil;
    }
    return keyRef;
}


/**
 传入二进制的DER格式的公钥(包含header),返回去除头部的密钥的二进制形式
 
 这里DER公钥的二进制格式TLV格式的,可以参考我的一篇博客http://www.jianshu.com/p/25803dd9527d

 @param d_key 二进制的DER格式的公钥
 @return
 */
+ (NSData *)stripPublicKeyHeader:(NSData *)d_key{
    // Skip ASN.1 public key header
    if (d_key == nil) return(nil);
    
    unsigned long len = [d_key length];
    if (!len) return(nil);
    
    unsigned char *c_key = (unsigned char *)[d_key bytes];
    unsigned int  idx     = 0;
    
    //1.此时密钥一定是0x30开头的,或者说第一个字节一定是30(16进制)
    if (c_key[idx++] != 0x30) return(nil);
    
    //2.第二个字节一定是81或者82,81代表长度用1byte表示，82代表长度用2byte表示（此字节部分tag后不存在
    if (c_key[idx] > 0x80) idx += c_key[idx] - 0x80 + 1;
    else idx++;
    
    //3. 默认使用PKCS1填充格式,使用公共的头部数据填充:300d06092a864886f70d0101010500
    // PKCS #1 rsaEncryption szOID_RSA_RSA
    static unsigned char seqiod[] =
    { 0x30,   0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01,
        0x01, 0x05, 0x00 };
    if (memcmp(&c_key[idx], seqiod, 15)) return(nil);
    
    idx += 15;
    
    //4. 然后这里又是一个TLV格式,和开始类似0382010d
    if (c_key[idx++] != 0x03) return(nil);
    
    if (c_key[idx] > 0x80) idx += c_key[idx] - 0x80 + 1;
    else idx++;
    
    //5. 这里需要补充00,具体参考我的其他博客
    if (c_key[idx++] != '\0') return(nil);
    
    //6. 返回的就是TLV中的value值,就是最后的内容
    return ([NSData dataWithBytes:&c_key[idx] length:len - idx]);
}

/**
 使用SecKeyRef对象加密核心方法
 
 @param data 待加密二进制数据
 @param keyRef 密钥SecKeyRef对象
 @return RSA加密以后二进制数据
 */
+ (NSData *)encryptData:(NSData *)data withKeyRef:(SecKeyRef) keyRef{
    const uint8_t *srcbuf = (const uint8_t *)[data bytes];
    size_t srclen = (size_t)data.length;
    
    // 加密block_size
    size_t block_size = SecKeyGetBlockSize(keyRef) * sizeof(uint8_t);
    void *outbuf = malloc(block_size);
    size_t src_block_size = block_size - 11;
    
    NSMutableData *ret = [[NSMutableData alloc] init];
    for(int idx=0; idx<srclen; idx+=src_block_size){
        //NSLog(@"%d/%d block_size: %d", idx, (int)srclen, (int)block_size);
        size_t data_len = srclen - idx;
        if(data_len > src_block_size){
            data_len = src_block_size;
        }
        
        size_t outlen = block_size;
        OSStatus status = noErr;
        status = SecKeyEncrypt(keyRef,
                               kSecPaddingPKCS1,
                               srcbuf + idx,
                               data_len,
                               outbuf,
                               &outlen
                               );
        if (status != 0) {
            NSLog(@"SecKeyEncrypt fail. Error Code: %d", status);
            ret = nil;
            break;
        }else{
            [ret appendBytes:outbuf length:outlen];
        }
    }
    
    free(outbuf);
    CFRelease(keyRef);
    return ret;
}
/* END: Encryption with RSA public key */

#pragma mark - 使用'.12'私钥文件解密
//解密
+ (NSString *)decryptString:(NSString *)str privateKeyWithContentsOfFile:(NSString *)path password:(NSString *)password{
    if (!str || !path) return nil;
    if (!password) password = @"";
    return [self decryptString:str privateKeyRef:[self getPrivateKeyRefWithContentsOfFile:path password:password]];
}

//获取私钥
+ (SecKeyRef)getPrivateKeyRefWithContentsOfFile:(NSString *)filePath password:(NSString*)password{
    
    NSData *p12Data = [NSData dataWithContentsOfFile:filePath];
    if (!p12Data) {
        return nil;
    }
    SecKeyRef privateKeyRef = NULL;
    NSMutableDictionary * options = [[NSMutableDictionary alloc] init];
    [options setObject: password 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);
    
    return privateKeyRef;
}

+ (NSString *)decryptString:(NSString *)str privateKeyRef:(SecKeyRef)privKeyRef{
    NSData *data = [[NSData alloc] initWithBase64EncodedString:str options:NSDataBase64DecodingIgnoreUnknownCharacters];
    if (!privKeyRef) {
        return nil;
    }
    data = [self decryptData:data withKeyRef:privKeyRef];
    NSString *ret = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    return ret;
}

#pragma mark - 使用私钥字符串解密
/* START: Decryption with RSA private key */

//使用私钥字符串解密
+ (NSString *)decryptString:(NSString *)str privateKey:(NSString *)privKey{
    if (!str) return nil;
    NSData *data = [[NSData alloc] initWithBase64EncodedString:str options:NSDataBase64DecodingIgnoreUnknownCharacters];
    data = [self decryptData:data privateKey:privKey];
    NSString *ret = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    return ret;
}

+ (NSData *)decryptData:(NSData *)data privateKey:(NSString *)privKey{
    if(!data || !privKey){
        return nil;
    }
    SecKeyRef keyRef = [self addPrivateKey:privKey];
    if(!keyRef){
        return nil;
    }
    return [self decryptData:data withKeyRef:keyRef];
}

+ (SecKeyRef)addPrivateKey:(NSString *)key{
    NSRange spos = [key rangeOfString:@"-----BEGIN RSA PRIVATE KEY-----"];
    NSRange epos = [key rangeOfString:@"-----END RSA PRIVATE KEY-----"];
    if(spos.location != NSNotFound && epos.location != NSNotFound){
        NSUInteger s = spos.location + spos.length;
        NSUInteger e = epos.location;
        NSRange range = NSMakeRange(s, e-s);
        key = [key substringWithRange:range];
    }
    key = [key stringByReplacingOccurrencesOfString:@"\r" withString:@""];
    key = [key stringByReplacingOccurrencesOfString:@"\n" withString:@""];
    key = [key stringByReplacingOccurrencesOfString:@"\t" withString:@""];
    key = [key stringByReplacingOccurrencesOfString:@" "  withString:@""];
    
    // This will be base64 encoded, decode it.
    NSData *data = base64_decode(key);
    data = [self stripPrivateKeyHeader:data];
    if(!data){
        return nil;
    }
    
    //a tag to read/write keychain storage
    NSString *tag = @"RSAUtil_PrivKey";
    NSData *d_tag = [NSData dataWithBytes:[tag UTF8String] length:[tag length]];
    
    // Delete any old lingering key with the same tag
    NSMutableDictionary *privateKey = [[NSMutableDictionary alloc] init];
    [privateKey setObject:(__bridge id) kSecClassKey forKey:(__bridge id)kSecClass];
    [privateKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
    [privateKey setObject:d_tag forKey:(__bridge id)kSecAttrApplicationTag];
    SecItemDelete((__bridge CFDictionaryRef)privateKey);
    
    // Add persistent version of the key to system keychain
    [privateKey setObject:data forKey:(__bridge id)kSecValueData];
    [privateKey setObject:(__bridge id) kSecAttrKeyClassPrivate forKey:(__bridge id)
     kSecAttrKeyClass];
    [privateKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)
     kSecReturnPersistentRef];
    
    CFTypeRef persistKey = nil;
    OSStatus status = SecItemAdd((__bridge CFDictionaryRef)privateKey, &persistKey);
    if (persistKey != nil){
        CFRelease(persistKey);
    }
    if ((status != noErr) && (status != errSecDuplicateItem)) {
        return nil;
    }
    
    [privateKey removeObjectForKey:(__bridge id)kSecValueData];
    [privateKey removeObjectForKey:(__bridge id)kSecReturnPersistentRef];
    [privateKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecReturnRef];
    [privateKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
    
    // Now fetch the SecKeyRef version of the key
    SecKeyRef keyRef = nil;
    status = SecItemCopyMatching((__bridge CFDictionaryRef)privateKey, (CFTypeRef *)&keyRef);
    if(status != noErr){
        return nil;
    }
    return keyRef;
}

+ (NSData *)stripPrivateKeyHeader:(NSData *)d_key{
    // Skip ASN.1 private key header
    if (d_key == nil) return(nil);
    
    unsigned long len = [d_key length];
    if (!len) return(nil);
    
    unsigned char *c_key = (unsigned char *)[d_key bytes];
    unsigned int  idx     = 22; //magic byte at offset 22
    
    if (0x04 != c_key[idx++]) return nil;
    
    //calculate length of the key
    unsigned int c_len = c_key[idx++];
    int det = c_len & 0x80;
    if (!det) {
        c_len = c_len & 0x7f;
    } else {
        int byteCount = c_len & 0x7f;
        if (byteCount + idx > len) {
            //rsa length field longer than buffer
            return nil;
        }
        unsigned int accum = 0;
        unsigned char *ptr = &c_key[idx];
        idx += byteCount;
        while (byteCount) {
            accum = (accum << 8) + *ptr;
            ptr++;
            byteCount--;
        }
        c_len = accum;
    }
    
    // Now make a new NSData from this buffer
    return [d_key subdataWithRange:NSMakeRange(idx, c_len)];
}

+ (NSData *)decryptData:(NSData *)data withKeyRef:(SecKeyRef) keyRef{
    const uint8_t *srcbuf = (const uint8_t *)[data bytes];
    size_t srclen = (size_t)data.length;
    
    size_t block_size = SecKeyGetBlockSize(keyRef) * sizeof(uint8_t);
    UInt8 *outbuf = malloc(block_size);
    size_t src_block_size = block_size;
    
    NSMutableData *ret = [[NSMutableData alloc] init];
    for(int idx=0; idx<srclen; idx+=src_block_size){
        //NSLog(@"%d/%d block_size: %d", idx, (int)srclen, (int)block_size);
        size_t data_len = srclen - idx;
        if(data_len > src_block_size){
            data_len = src_block_size;
        }
        
        size_t outlen = block_size;
        OSStatus status = noErr;
        status = SecKeyDecrypt(keyRef,
                               kSecPaddingNone,
                               srcbuf + idx,
                               data_len,
                               outbuf,
                               &outlen
                               );
        if (status != 0) {
            NSLog(@"SecKeyEncrypt fail. Error Code: %d", status);
            ret = nil;
            break;
        }else{
            //the actual decrypted data is in the middle, locate it!
            int idxFirstZero = -1;
            int idxNextZero = (int)outlen;
            for ( int i = 0; i < outlen; i++ ) {
                if ( outbuf[i] == 0 ) {
                    if ( idxFirstZero < 0 ) {
                        idxFirstZero = i;
                    } else {
                        idxNextZero = i;
                        break;
                    }
                }
            }
            
            [ret appendBytes:&outbuf[idxFirstZero+1] length:idxNextZero-idxFirstZero-1];
        }
    }
    
    free(outbuf);
    CFRelease(keyRef);
    return ret;
}

/* END: Decryption with RSA private key */
@end

参考: https://github.com/ideawu/Objective-C-RSA

只有公钥的模n和公开幂e

当只有模n和公开幂e的时候,如果后台使用的JAVA,比较常见的情况是传递一个xml,内部包含公钥的长度,模n,以及幂e(有可能是base64的string,或者16进制data)下面的就有一个通用格式和一个实例:

<BitStrength>1024</BitStrength>
<RSAKeyValue>
<Modulus>xxxxxxxxxxxxxxxxxxxxx</Modulus>
<Exponent>xxxx</Exponent>
</RSAKeyValue>

<RSAKeyValue>
  <Modulus>yOTe0L1/NcbXdZYwliS82MiTE8VD5WD23S4RDsdbJOFzCLbsyb4d+K1M5fC+xDfCkji1zQjPiiiToZ7JSj/2ww==</Modulus>
  <Exponent>AWAB</Exponent>
</RSAKeyValue>

iOS系统的库不支持直接使用模n和幂e直接对数据进行加密.但是有大神开源了这个库SCZ-BasicEncodingRules-iOS.这个库的作用是通过已知的RSA的公钥的modulus和exponent,创建一个RSA的public key.下面是调用方法:

//注意使用这个库之前需要将base64的string转化成nsdata数据
// pubKeyModData 模n的二进制表示
// pubKeyExpData 幂e的二进制表示
NSMutableArray *testArray = [[NSMutableArray alloc] init];
[testArray addObject:pubKeyModData];
[testArray addObject:pubKeyExpData];
NSData *testPubKey = [testArray berData];

然后,将刚刚生成的publickey data写入keychain中,其他步骤见上节:

NSString * peerName = @"Test Public Key";

NSData * peerTag = [[NSData alloc] initWithBytes:(const void *)[peerName UTF8String] length:[peerName length]];

NSMutableDictionary * peerPublicKeyAttr = [[NSMutableDictionary alloc] init];
[peerPublicKeyAttr 
   setObject:(__bridge id)kSecClassKey 
   forKey:(__bridge id)kSecClass];
[peerPublicKeyAttr 
   setObject:(__bridge id)kSecAttrKeyTypeRSA 
   forKey:(__bridge id)kSecAttrKeyType];
[peerPublicKeyAttr 
   setObject:peerTag 
   forKey:(__bridge id)kSecAttrApplicationTag];
[peerPublicKeyAttr 
   setObject:testPubKey 
   forKey:(__bridge id)kSecValueData];
[peerPublicKeyAttr 
   setObject:[NSNumber numberWithBool:YES] 
   forKey:(__bridge id)kSecReturnPersistentRef];

sanityCheck = SecItemAdd((__bridge CFDictionaryRef) peerPublicKeyAttr, (CFTypeRef *)&persistPeer);

这里有一个使用上述方式的一个Demo工程:RSAPublicKey.核心方法如下:

SecKeyRef pubKey = [RSAPubKey stringToRSAPubKey:@"0E8fPw5rw/t1xobyTbXtZgLNYuBlX3RQy4re0SZerVGNW/LkN92Ycw+aLT0/9bxy/WuY63JOJFmZFVsIAnKhdfZLCoFQPq5nNJ1rUNfJ4J7FWvJoaM69IM/VA3GTdIRGQHgQJIXlXbiGOk+lJfo51Ncb67w2miqucsoS/YcgL0=" andExponent:@"AQAB"];

@implementation RSAPubKey

+ (SecKeyRef) stringToRSAPubKey: (NSString*) modulus andExponent:(NSString*) exponent
{
    NSData* modulusData = [NSData dataWithBase64EncodedString: modulus];
    NSData* exponentData = [NSData dataWithBase64EncodedString: exponent];

    return [RSAPubKey dataRSAPubKey: modulusData andExponent: exponentData];
}

+ (SecKeyRef) dataRSAPubKey: (NSData*) modulus andExponent:(NSData*) exponent
{
    if( modulus == nil || exponent == nil)
        return nil;

    NSMutableArray *testArray = [[NSMutableArray alloc] init];
    const char fixByte = 0;
    NSMutableData * fixedModule = [NSMutableData dataWithBytes:&fixByte length:1];
    [fixedModule appendData:modulus];
    [testArray addObject:fixedModule];
    [testArray addObject:exponent];
    NSData *pubKey = [testArray berData];
    if( pubKey == nil ) {
        return nil;
    }

    //a tag to read/write keychain storage
    NSString *tag = @"LiveStorage_PubKey";
    NSData *d_tag = [NSData dataWithBytes:[tag UTF8String] length:[tag length]];
    
    // Delete any old lingering key with the same tag
    NSMutableDictionary *publicKey = [[NSMutableDictionary alloc] init];
    [publicKey setObject:(__bridge id) kSecClassKey forKey:(__bridge id)kSecClass];
    [publicKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
    [publicKey setObject:d_tag forKey:(__bridge id)kSecAttrApplicationTag];
    SecItemDelete((__bridge CFDictionaryRef)publicKey);

    // Add persistent version of the key to system keychain
    [publicKey setObject:pubKey forKey:(__bridge id)kSecValueData];
    [publicKey setObject:(__bridge id) kSecAttrKeyClassPublic forKey:(__bridge id) kSecAttrKeyClass];
    [publicKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id) kSecReturnPersistentRef];
    
    CFTypeRef persistKey = nil;
    OSStatus status = SecItemAdd((__bridge CFDictionaryRef)publicKey, &persistKey);
    if (persistKey != nil){
        CFRelease(persistKey);
    }
    if ((status != noErr) && (status != errSecDuplicateItem)) {
        return nil;
    }
    
    publicKey = [[NSMutableDictionary alloc] init];
    
    [publicKey setObject:(__bridge id) kSecClassKey forKey:(__bridge id)kSecClass];
    [publicKey setObject:d_tag forKey:(__bridge id)kSecAttrApplicationTag];
    [publicKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecReturnRef];
    [publicKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
    
    // Now fetch the SecKeyRef version of the key
    SecKeyRef keyRef = nil;
    status = SecItemCopyMatching((__bridge CFDictionaryRef)publicKey, (CFTypeRef *)&keyRef);
    if(status != noErr){
        return nil;
    }
    return keyRef;
}
@end

或者我们可以创建一个base64编码的PEM格式的public key:

{
    NSString *modulusString =  @"c19bccae1e67743fab1c978f03122fb1a78ef05d565a2964728062ad0365e4751b8253df5fd13ab4ecb95c81ff17b91f969e4fb3d8274c30533338684278f6e5548027df775c055943a24a4117b0274c296c68b722c71670d4b21489a3da05d37ba06f2fb771b671a2c746bae4a049dc718fba19a75f1fb8ae1dd715b33d66a3";
    NSString *exponentString = @"010001";
    
    NSData *pubKeyModData = bytesFromHexString(modulusString);
    NSData *pubKeyExpData = bytesFromHexString(exponentString);
    NSArray *keyArray = @[pubKeyModData, pubKeyExpData];
    
    //Given that you are using SCZ-BasicEncodingRules-iOS:
    NSData *berData = [keyArray berData];
    NSLog(@"berData:\n%@", berData);
    
    NSString *berBase64 = [berData base64EncodedStringWithOptions:0];
    NSString *preamble = @"-----BEGIN CERTIFICATE REQUEST-----";
    NSString *postamble = @"-----END CERTIFICATE REQUEST-----";
    NSString *pem = [NSString stringWithFormat:@"%@\n%@\n%@", preamble, berBase64, postamble];
    NSLog(@"pem:\n%@", pem);
}

NSData* bytesFromHexString(NSString * aString) {
    NSString *theString = [[aString componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] componentsJoinedByString:nil];

    NSMutableData* data = [NSMutableData data];
    int idx;
    for (idx = 0; idx+2 <= theString.length; idx+=2) {
        NSRange range = NSMakeRange(idx, 2);
        NSString* hexStr = [theString substringWithRange:range];
        NSScanner* scanner = [NSScanner scannerWithString:hexStr];
        unsigned int intValue;
        if ([scanner scanHexInt:&intValue])
            [data appendBytes:&intValue length:1];
    }
    return data;
}

QuickRSA开源库包括系统API以及OpenSSL完成

QuickRSA,可以通过iOS的系统API来获取RSA SecKeyRef,并且用来Enc/Dec:

@interface QRSecCrypto : NSObject
//1. 509 Cert
+ (SecKeyRef)RSASecKeyPubCopyWithX509CertData:(NSData *)certData;
//2. Import P12 for private key
+ (SecKeyRef)RSASecKeyPriCopyWithP12Data:(NSData *)p12Data password:(NSString *)password;
//3. Use Keychain
+ (SecKeyRef)RSASecKeyCopyWithPKCS1Data:(NSData *)pkcs1Data appTag:(NSString *)appTag isPublic:(BOOL)isPublic;
//4. Use System API (For iOS 10 and later only)
+ (SecKeyRef)RSASecKeyCopyWithDERData:(NSData *)derData isPublic:(BOOL)isPublic;
@end

@interface NSData(QRSecCrypto)
- (NSData *)RSAEncryptDataWithPublicKey:(SecKeyRef)publicKey;
- (NSData *)RSADecryptDataWithPrivateKey:(SecKeyRef)privateKey;
@end

也可以通过OpenSSL来进行RSA加密和解密,同时可以直接使用模modulus和幂exponent

@interface NSData(OpenSSL)
//Use PEM, Pub(Pri) Enc -> Pri(Pub) Dec
- (NSData *)OpenSSL_RSA_EncryptDataWithPEM:(NSData *)pemData isPublic:(BOOL)isPublic;//PEM key
- (NSData *)OpenSSL_RSA_DecryptDataWithPEM:(NSData *)pemData isPublic:(BOOL)isPublic;//PEM key

//Use DER, Pub(Pri) Enc -> Pri(Pub) Dec
- (NSData *)OpenSSL_RSA_EncryptDataWithDER:(NSData *)derData isPublic:(BOOL)isPublic;//DER key
- (NSData *)OpenSSL_RSA_DecryptDataWithDER:(NSData *)derData isPublic:(BOOL)isPublic;//DER key

//Use modulus exponent
- (NSData *)OpenSSL_RSA_DataWithPublicModulus:(NSData *)modulus exponent:(NSData *)exponent isDecrypt:(BOOL)isDecrypt;
@end

同时,该库提供了QRFormatConvert类,进行如下类型的转换:

PEM <-> DER
modulus, exponent <-> DER
PKCS1 <-> DER
Data <->Hex string

参考

这里还有一个将模n和幂e转化成PEM 格式的 pubic key的工具:
https://superdry.apphb.com/tools/online-rsa-key-converter

网友评论

9f94d02340f1:然后我用instruments做内存泄漏检测的时候，这一块也总是出现泄漏。楼主你知道怎么回事吗？
9f94d02340f1:if (policy) CFRelease(policy);
if (trust) CFRelease(trust);
if (cert) CFRelease(cert);
释放这几个的时候，我这边还得把他们设置为NULL才能释放，不然释放不了
brownfeng:用备注里面的开源库吧. bug 会比较少
9f94d02340f1:Mark
沧冥海:你好，请问我只有后台给的模和幂，但是加密之后，后台解不出来，模和幂还有参数都没有问题，后台说是我的加密方法有问题，但是我使用
let rsaData = nsdatas.openSSL_RSA_Data(withPublicModulus: str.data(using: String.Encoding.utf8)!, exponent: ex.data(using: String.Encoding.utf8)!, isDecrypt: false)!
我也不知道该如何去改，请问，是我的传入的参数类型有问题，还是说这个方法，可能不适合我
沧冥海:@brownfeng 我拿到的模和指数，就是base64之后的，因为加密方法需要传递data类型，所以我才用上面的方法进行转换。
brownfeng:有可能呢你str.data(using: String.Encoding.utf8)! 还有ex.data(using: String.Encoding.utf8)!.
这里用的二进制需要base64编码. 你要不试试
brownfeng:你把模和冥转化成public key 让后台看看.生成的public key是不是一样的.
蚂蚱Damon:等下验证之后，再来评论.

iOS安全相关 - iOS中使用RSA加密与解密

带公钥证书,PEM格式publickey,DER格式的二进制字符串加密方法

只有公钥的模n和公开幂e

QuickRSA开源库包括系统API以及OpenSSL完成

参考

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