AES解密iOS

Question

我尝试使用 AES 解密来解密字符串消息。

- (NSData *)AES256DecryptWithKey:(NSString *)key andIV:(NSString*)iv{

// 'key' should be 32 bytes for AES256, will be null-padded otherwise
char keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)
bzero( keyPtr, sizeof( keyPtr ) ); // fill with zeroes (for padding)

// fetch key data
[key getCString:keyPtr maxLength:sizeof( keyPtr ) encoding:NSUTF8StringEncoding];

NSUInteger dataLength = [self length];

//See the doc: For block ciphers, the output size will always be less than or
//equal to the input size plus the size of one block.
//That's why we need to add the size of one block here
size_t bufferSize = dataLength + kCCBlockSizeAES128;
void *buffer = malloc( bufferSize );

size_t numBytesDecrypted = 0;

CCCryptorStatus cryptStatus = CCCrypt( kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                      keyPtr, kCCKeySizeAES256,
                                      //[iv cStringUsingEncoding:NSUTF8StringEncoding] /* initialization vector (optional) */,
                                      NULL,
                                      [self bytes], dataLength, /* input */
                                      buffer, bufferSize, /* output */
                                      &numBytesDecrypted );

if( cryptStatus == kCCSuccess )
{
    NSLog(@"CRYPTSTATUS %d",cryptStatus);

    //the returned NSData takes ownership of the buffer and will free it on deallocation
    return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];

}

NSLog(@"CRYPTSTATUS %d",cryptStatus);


free( buffer ); //free the buffer
return nil;

}

但是结果被截断了，有人有建议吗？填充似乎有问题，但我不知道。稍后将发送 AES 密钥（RSA 加密）。

如果您能给我一些建议，那就太好了。

编辑：输入（base64 编码）

NSData *keydata = [[NSData alloc]initWithBase64EncodedString:@"QUFBQUE5MThEOTMyOEJCQkJCQkJCODhFMTM3MURFREQ="];
NSString *key = [[NSString alloc]initWithData:keydata encoding:NSUTF8StringEncoding];

NSData *msgnormal = [[NSData alloc]initWithBase64EncodedString:@"oE4LOCjOfjPeggXsDbLQ4ko+57kdb/5EBUcmlTBvaaI="];
NSData *decrypted = [msgnormal AES256DecryptWithKey:key andIV:@""];

NSLog(@"DECRYPTED: %@",[[NSString alloc]initWithData:decrypted encoding:NSUTF8StringEncoding]);

Answer 1

输入也应该填充到最近的块。如果输入在块边界上结束，您实际上仍然添加了一个完整的其他块，只是为了始终拥有填充（稍后将删除）。

您必须知道解密文本的结束位置和填充的开始位置。通常，这是使用填充处理的，例如PKCS7。因为你会知道填充有多少字节，所以以后很容易去掉。