RSA加密

iOS中的Security.framework提供了对RSA算法的支持。

在iOS中使用RSA加密解密，需要用到.der和.p12后缀格式的文件，其中.der格式的文件存放的是公钥（Public key）用于加密，.p12格式的文件存放的是私钥（Private key）用于解密。

使用Mac终端自带的openssl工具，生成公钥和私钥。

一、使用openssl生成所需秘钥文件
生成环境是在mac系统下，使用openssl进行生成，首先打开终端，按下面这些步骤依次来做：

1. 生成模长为1024bit的私钥文件private_key.pem
openssl genrsa -out private_key.pem 1024

2. 生成证书请求文件rsaCertReq.csr
openssl req -new -key private_key.pem -out rsaCerReq.csr
注意：这一步会提示输入国家、省份、mail等信息，可以根据实际情况填写，或者全部不用填写，直接全部敲回车.

3. 生成证书rsaCert.crt，并设置有效时间为10年
openssl x509 -req -days 3650 -in rsaCerReq.csr -signkey private_key.pem -out rsaCert.crt

4. 生成供iOS使用的公钥文件public_key.der
openssl x509 -outform der -in rsaCert.crt -out public_key.der

5. 生成供iOS使用的私钥文件private_key.p12
openssl pkcs12 -export -out private_key.p12 -inkey private_key.pem -in rsaCert.crt
注意：这一步会提示给私钥文件设置密码，直接输入想要设置密码即可，然后敲回车，然后再验证刚才设置的密码，再次输入密码，然后敲回车，完毕！
在解密时，private_key.p12文件需要和这里设置的密码配合使用，因此需要牢记此密码.

6. 生成供Java使用的公钥rsa_public_key.pem
openssl rsa -in private_key.pem -out rsa_public_key.pem -pubout

7. 生成供Java使用的私钥pkcs8_private_key.pem
openssl pkcs8 -topk8 -in private_key.pem -out pkcs8_private_key.pem -nocrypt

全部执行成功后，会生成如下文件，其中public_key.der和private_key.p12就是iOS需要用到的文件；rsa_public_key.pem和pkcs8_private_key.pem就是JAVA需要用到的文件。

加密操作步骤

1.项目内导入Security.framework框架。

2.项目中导入生成的.der公钥和.p12私钥。

3.导入加密类 —— RSAEncryptor类

4.实用api进行加密解密

#import <Foundation/Foundation.h>

@interface RSAEncryptor : NSObject

/**
*  加密方法
*
*  @param str   需要加密的字符串
*  @param path  '.der'格式的公钥文件路径
*/
+ (NSString *)encryptString:(NSString *)str
publicKeyWithContentsOfFile:(NSString *)path;

/**
*  解密方法
*
*  @param str       需要解密的字符串
*  @param path      '.p12'格式的私钥文件路径
*  @param password  私钥文件密码
*/
+ (NSString *)decryptString:(NSString *)str
privateKeyWithContentsOfFile:(NSString *)path
password:(NSString *)password;

/**
*  加密方法
*
*  @param str    需要加密的字符串
*  @param pubKey 公钥字符串
*/
+ (NSString *)encryptString:(NSString *)str
publicKey:(NSString *)pubKey;

/**
*  解密方法
*
*  @param str     需要解密的字符串
*  @param privKey 私钥字符串
*/
+ (NSString *)decryptString:(NSString *)str
privateKey:(NSString *)privKey;

@end

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

@implementation RSAEncryptor

static NSString *base64_encode_data(NSData *data){
data = [data base64EncodedDataWithOptions:0];
NSString *ret = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
return ret;
}

static NSData *base64_decode(NSString *str){
NSData *data = [[NSData alloc] initWithBase64EncodedString:str options:NSDataBase64DecodingIgnoreUnknownCharacters];
return data;
}

#pragma mark - 使用'.der'公钥文件加密

//加密
+ (NSString *)encryptString:(NSString *)str publicKeyWithContentsOfFile:(NSString *)path{
if (!str || !path)  return nil;
return [self encryptString:str publicKeyRef:[self getPublicKeyRefWithContentsOfFile:path]];
}

//获取公钥
+ (SecKeyRef)getPublicKeyRefWithContentsOfFile:(NSString *)filePath{

NSData *certData = [NSData dataWithContentsOfFile:filePath];
if (!certData) {
return nil;
}
SecCertificateRef cert = SecCertificateCreateWithData(NULL, (CFDataRef)certData);
SecKeyRef key = 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) {
key = SecTrustCopyPublicKey(trust);
}
}
}
}
if (policy) CFRelease(policy);
if (trust) CFRelease(trust);
if (cert) CFRelease(cert);
return key;
}

+ (NSString *)encryptString:(NSString *)str publicKeyRef:(SecKeyRef)publicKeyRef{
if(![str dataUsingEncoding:NSUTF8StringEncoding]){
return nil;
}
if(!publicKeyRef){
return nil;
}
NSData *data = [self encryptData:[str dataUsingEncoding:NSUTF8StringEncoding] withKeyRef:publicKeyRef];
NSString *ret = base64_encode_data(data);
return ret;
}

#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 - 使用公钥字符串加密

/* START: Encryption with RSA public key */

//使用公钥字符串加密
+ (NSString *)encryptString:(NSString *)str publicKey:(NSString *)pubKey{
NSData *data = [self encryptData:[str dataUsingEncoding:NSUTF8StringEncoding] publicKey:pubKey];
NSString *ret = base64_encode_data(data);
return ret;
}

+ (NSData *)encryptData:(NSData *)data publicKey:(NSString *)pubKey{
if(!data || !pubKey){
return nil;
}
SecKeyRef keyRef = [self addPublicKey:pubKey];
if(!keyRef){
return nil;
}
return [self encryptData:data withKeyRef:keyRef];
}

+ (SecKeyRef)addPublicKey:(NSString *)key{
NSRange spos = [key rangeOfString:@"-----BEGIN PUBLIC KEY-----"];
NSRange epos = [key rangeOfString:@"-----END PUBLIC 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 stripPublicKeyHeader:data];
if(!data){
return nil;
}

//a tag to read/write keychain storage
NSString *tag = @"RSAUtil_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:data 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 removeObjectForKey:(__bridge id)kSecValueData];
[publicKey removeObjectForKey:(__bridge id)kSecReturnPersistentRef];
[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;
}

+ (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;

if (c_key[idx++] != 0x30) return(nil);

if (c_key[idx] > 0x80) idx += c_key[idx] - 0x80 + 1;
else idx++;

// 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;

if (c_key[idx++] != 0x03) return(nil);

if (c_key[idx] > 0x80) idx += c_key[idx] - 0x80 + 1;
else idx++;

if (c_key[idx++] != '\0') return(nil);

// Now make a new NSData from this buffer
return ([NSData dataWithBytes:&c_key[idx] length:len - idx]);
}

+ (NSData *)encryptData:(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);
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;
}

#pragma mark - KT( 把SecKeyRef 转化成NSData )
- (NSData *)getPublicKeyBitsFromKey:(SecKeyRef)givenKey {

static const uint8_t publicKeyIdentifier[] = "com.your.company.publickey";
NSData *publicTag = [[NSData alloc] initWithBytes:publicKeyIdentifier length:sizeof(publicKeyIdentifier)];

OSStatus sanityCheck = noErr;
NSData * publicKeyBits = nil;

NSMutableDictionary * queryPublicKey = [[NSMutableDictionary alloc] init];
[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];

// Temporarily add key to the Keychain, return as data:
NSMutableDictionary * attributes = [queryPublicKey mutableCopy];
[attributes setObject:(__bridge id)givenKey forKey:(__bridge id)kSecValueRef];
[attributes setObject:@YES forKey:(__bridge id)kSecReturnData];
CFTypeRef result;
sanityCheck = SecItemAdd((__bridge CFDictionaryRef) attributes, &result);
if (sanityCheck == errSecSuccess) {
publicKeyBits = CFBridgingRelease(result);

// Remove from Keychain again:
(void)SecItemDelete((__bridge CFDictionaryRef) queryPublicKey);
}

return publicKeyBits;
}

@end