MTRsa.m

#import "MTRsa.h"

/*
 @author: ideawu
 @link: https://github.com/ideawu/Objective-C-RSA
 */

#import <Security/Security.h>

@implementation MTRsa

NSString *MTStringByEncodingInBase64(NSData *data) {
    NSUInteger length = [data length];
    NSMutableData *mutableData = [[NSMutableData alloc] initWithLength:((length + 2) / 3) * 4];
    
    uint8_t *input = (uint8_t *)[data bytes];
    uint8_t *output = (uint8_t *)[mutableData mutableBytes];
    
    for (NSUInteger i = 0; i < length; i += 3)
    {
        NSUInteger value = 0;
        for (NSUInteger j = i; j < (i + 3); j++)
        {
            value <<= 8;
            if (j < length)
            {
                value |= (0xFF & input[j]);
            }
        }
        
        static uint8_t const kAFBase64EncodingTable[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
        
        NSUInteger idx = (i / 3) * 4;
        output[idx + 0] = kAFBase64EncodingTable[(value >> 18) & 0x3F];
        output[idx + 1] = kAFBase64EncodingTable[(value >> 12) & 0x3F];
        output[idx + 2] = (i + 1) < length ? kAFBase64EncodingTable[(value >> 6)  & 0x3F] : '=';
        output[idx + 3] = (i + 2) < length ? kAFBase64EncodingTable[(value >> 0)  & 0x3F] : '=';
    }
    
    return [[NSString alloc] initWithData:mutableData encoding:NSASCIIStringEncoding];
}

static NSString *base64_encode_data(NSData *data) {
    if ([data respondsToSelector:@selector(base64EncodedDataWithOptions:)]) {
        data = [data base64EncodedDataWithOptions:0];
        NSString *ret = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        return ret;
    } else {
        return MTStringByEncodingInBase64(data);
    }
}

static NSData *base64_decode(NSString *str) {
    if ([NSData instancesRespondToSelector:@selector(initWithBase64EncodedString:options:)]) {
        NSData *data = [[NSData alloc] initWithBase64EncodedString:str options:NSDataBase64DecodingIgnoreUnknownCharacters];
        return data;
    } else {
        return [[NSData alloc] initWithBase64Encoding:[str stringByReplacingOccurrencesOfString:@"[^A-Za-z0-9+/=]" withString:@"" options:NSRegularExpressionSearch range:NSMakeRange(0, [str length])]];
    }
}

+ (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]);
}

//credit: http://hg.mozilla.org/services/fx-home/file/tip/Sources/NetworkAndStorage/CryptoUtils.m#l1036
+ (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)];
}

+ (SecKeyRef)addPublicKey:(NSString *)key_s {
    NSString *key = [[key_s stringByReplacingOccurrencesOfString:@"-----BEGIN RSA PUBLIC KEY-----\n" withString:@"-----BEGIN PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8A"] stringByReplacingOccurrencesOfString:@"-----END RSA PUBLIC KEY-----" withString:@"-----END PUBLIC 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 = [MTRsa 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;
}

+ (SecKeyRef)addPrivateKey:(NSString *)key{
    NSRange spos;
    NSRange epos;
    spos = [key rangeOfString:@"-----BEGIN RSA PRIVATE KEY-----"];
    if(spos.length > 0){
        epos = [key rangeOfString:@"-----END RSA PRIVATE KEY-----"];
    }else{
        spos = [key rangeOfString:@"-----BEGIN PRIVATE KEY-----"];
        epos = [key rangeOfString:@"-----END 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 = [MTRsa 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;
}

/* START: Encryption & Decryption with RSA private key */

+ (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;
    
    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,
                               kSecPaddingNone,
                               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;
}

+ (NSString *)encryptString:(NSString *)str privateKey:(NSString *)privKey{
    NSData *data = [MTRsa encryptData:[str dataUsingEncoding:NSUTF8StringEncoding] privateKey:privKey];
    NSString *ret = base64_encode_data(data);
    return ret;
}

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

+ (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;
}


+ (NSString *)decryptString:(NSString *)str privateKey:(NSString *)privKey{
    NSData *data = base64_decode(str);
    data = [MTRsa 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 = [MTRsa addPrivateKey:privKey];
    if(!keyRef){
        return nil;
    }
    return [MTRsa decryptData:data withKeyRef:keyRef];
}

/* END: Encryption & Decryption with RSA private key */

/* START: Encryption & Decryption with RSA public key */

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

+ (NSString *)decryptString:(NSString *)str publicKey:(NSString *)pubKey{
    NSData *data = base64_decode(str);
    data = [MTRsa decryptData:data publicKey:pubKey];
    NSString *ret = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    return ret;
}

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

/* END: Encryption & Decryption with RSA public key */

@end