rooms-ios/NextcloudTalk/NCPushNotificationsUtils.m

/**
 * SPDX-FileCopyrightText: 2020 Nextcloud GmbH and Nextcloud contributors
 * SPDX-License-Identifier: GPL-3.0-or-later
 */

#import "NCPushNotificationsUtils.h"

#import <openssl/rsa.h>
#import <openssl/pem.h>
#import <openssl/bio.h>
#import <openssl/bn.h>
#import <openssl/sha.h>
#import <openssl/err.h>

@implementation NCPushNotificationsUtils

+ (NSString *)decryptPushNotification:(NSString *)message withDevicePrivateKey:(NSData *)privateKey
{
    NSString *privateKeyString = [[NSString alloc] initWithData:privateKey encoding:NSUTF8StringEncoding];
    NSData *decodedData = [[NSData alloc] initWithBase64EncodedString:message options:0];
    char *privKey = (char *)[privateKeyString UTF8String];
    
    // Get Device Private Key from PEM
    BIO *bio = BIO_new(BIO_s_mem());
    BIO_write(bio, privKey, (int)strlen(privKey));
    
    EVP_PKEY* pkey = 0;
    PEM_read_bio_PrivateKey(bio, &pkey, 0, 0);
    
    RSA* rsa = EVP_PKEY_get1_RSA(pkey);
    
    // Decrypt the message
    unsigned char *decrypted = (unsigned char *) malloc(4096);
    
    int decrypted_length = RSA_private_decrypt((int)[decodedData length], [decodedData bytes], decrypted, rsa, RSA_PKCS1_PADDING);
    if(decrypted_length == -1) {
        char buffer[500];
        ERR_error_string(ERR_get_error(), buffer);
        NSLog(@"%@",[NSString stringWithUTF8String:buffer]);
        return nil;
    }
    
    NSString *decryptString = [[NSString alloc] initWithBytes:decrypted length:decrypted_length encoding:NSUTF8StringEncoding];
    
    if (decrypted)
        free(decrypted);
    free(bio);
    free(rsa);
    
    return decryptString;
}

@end