hmac-sha1.swift

import Foundation
import CommonCryptoKit

enum CryptoAlgorithm {
    case MD5, SHA1, SHA224, SHA256, SHA384, SHA512
    
    var HMACAlgorithm: CCHmacAlgorithm {
        var result: Int = 0
        switch self {
        case .MD5:      result = kCCHmacAlgMD5
        case .SHA1:     result = kCCHmacAlgSHA1
        case .SHA224:   result = kCCHmacAlgSHA224
        case .SHA256:   result = kCCHmacAlgSHA256
        case .SHA384:   result = kCCHmacAlgSHA384
        case .SHA512:   result = kCCHmacAlgSHA512
        }
        return CCHmacAlgorithm(result)
    }
    
    var digestLength: Int {
        var result: Int32 = 0
        switch self {
        case .MD5:      result = CC_MD5_DIGEST_LENGTH
        case .SHA1:     result = CC_SHA1_DIGEST_LENGTH
        case .SHA224:   result = CC_SHA224_DIGEST_LENGTH
        case .SHA256:   result = CC_SHA256_DIGEST_LENGTH
        case .SHA384:   result = CC_SHA384_DIGEST_LENGTH
        case .SHA512:   result = CC_SHA512_DIGEST_LENGTH
        }
        return Int(result)
    }
}

extension String {
    
    func hmac(algorithm: CryptoAlgorithm, key: String) -> String {
        let stringData = self.cString(using: .utf8)
        let keyData = key.cString(using: .utf8)
        
        let result = hmacGenerate(from: stringData, withKey: keyData, using: algorithm)
        return result.base64EncodedString(options:[])
    }

    private func hmacGenerate(from data: Data, withKey key: Data, using algorithm: CryptoAlgorithm) -> Data {
        // Get data pointers
        let dataBytesPointer = data.unsafeBytes
        let keyBytesPointer = key.unsafeBytes
        
        var result = Data(count: Int(algorithm.digestLength))
        
        let resultBytesPointer = result.unsafeMutableBytes
        
        CCHmac(algorithm.HMACAlgorithm, keyBytesPointer, key.count, dataBytesPointer, data.count, resultBytesPointer)
        
        return result
    }
}