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建構 HMAC 簽章

建構 HMAC 簽章

您可能使用 HMAC 認證，而不要使用記號型授權。

這些認證用來建立類似於 AWS Signature 第 4 版的授權標頭。 計算簽章可提供身分驗證及傳輸中資料完整性。 每個簽章都與要求的時間戳記相關聯，因此不可能重複使用 authorization 標頭。 標頭由四個元件組合：演算法宣告、認證資訊、簽署標頭及計算簽章。

AWS4-HMAC-SHA256 Credential={access-key}/{date}/{region}/s3/aws4_request,SignedHeaders=host;x-amz-date;{other-required-headers},Signature={signature}

日期以 YYYYMMDD 格式提供，而且該地區對應至所指定儲存區的位置，例如 us。 一律需要 host 和 x-amz-date 標頭。 根據要求，可能還需要其他標頭（例如，在有效負載要求時，需要 x-amz-content-sha256）。 需要重新計算每個個別要求的簽章，因此許多開發人員都偏好使用會自動產生 authorization 標頭的工具或 SDK。

建立 authorization 標頭

首先，我們需要以標準化格式建立要求。

  1. 宣告所使用的 HTTP 方法（例如 PUT）
  2. 定義以標準化形式存取的資源。 這是 http(s):// 與查詢字串之間的位址部分。 若為帳戶層次的要求（例如列出儲存區），則這只是 /。
  3. 如果有任何要求參數，它們必須以百分比編碼進行標準化（例如，空格會呈現為 %20）並按字母順序排序。
  4. 標頭需要藉由移除空格、轉換為小寫，並為每個標頭新增換行來進行標準化，然後必須以 ASCII 順序排序。
  5. 以標準格式列出之後，則必須進行「簽署」。 這只會採用標頭名稱，而不是其值，並按字母順序列出它們，以分號區隔。所有要求都需要 Host 和 x-amz-date。
  6. 如果要求具有內文（例如上傳物件或建立新的 ACL 時），則必須使用 SHA-256 演算法來雜湊處理要求內文，並以 base-16 編碼的小寫字元表示。
  7. 結合以換行區隔的 HTTP 方法、標準化資源、標準化參數、標準化標頭、已簽署標頭及雜湊要求內文，以形成標準化要求。

接下來，我們需要組合 'string-to-sign'，它將與簽章金鑰結合，以形成最終簽章。 string-to-sign 採用下列格式：

AWS4-HMAC-SHA256
{time}
{date}/{string}/s3/aws4_request
{hashed-standardized-request}
  1. 時間必須是現行世界標準時間，並根據 ISO 8601 規格予以格式化（例如 20161128T152924Z）。
  2. 日期採用 YYYYMMDD 格式。
  3. 最後一行是先前建立並使用 SHA-256 演算法雜湊處理的標準化要求。

現在，我們需要計算簽章。

  1. 首先，需要透過帳戶的密碼存取金鑰、現行日期以及所使用的地區和 API 類型來計算簽章金鑰。
  2. 字串 AWS4 會新增為密碼存取金鑰的字首，然後使用該新字串作為雜湊處理日期的金鑰。
  3. 使用產生的雜湊作為雜湊處理地區的金鑰。
  4. 處理程序會繼續使用新的雜湊作為雜湊處理 API 類型的金鑰。
  5. 最後，使用最新的雜湊作為雜湊處理字串 aws4_request 以建立簽章金鑰的金鑰。
  6. 然後，使用簽章金鑰作為雜湊處理 string-to-sign 以產生最終簽章的金鑰。

現在，唯一剩下的步驟是組合 authorization 標頭，如下所示：

AWS4-HMAC-SHA256 Credential={access-key}/{date}/{region}/s3/aws4_request,SignedHeaders=host;x-amz-date;{other-required-headers},Signature={signature}

產生 authorization 標頭

Python 範例

import os
import datetime
import hashlib
import hmac
import requests

# please don't store credentials directly in code
access_key = os.environ.get('COS_HMAC_ACCESS_KEY_ID')
secret_key = os.environ.get('COS_HMAC_SECRET_ACCESS_KEY')

# request elements
http_method = 'GET'
host = 's3.us.cloud-object-storage.appdomain.cloud'
region = 'us-standard'
endpoint = 'https://s3.us.cloud-object-storage.appdomain.cloud'
bucket = '' # add a '/' before the bucket name to list buckets
object_key = ''
request_parameters = ''


# hashing and signing methods
def hash(key, msg):
    return hmac.new(key, msg.encode('utf-8'), hashlib.sha256).digest()

# region is a wildcard value that takes the place of the AWS region value
# as COS doen't use the same conventions for regions, this parameter can accept any string
def createSignatureKey(key, datestamp, region, service):

    keyDate = hash(('AWS4' + key).encode('utf-8'), datestamp)
    keyString = hash(keyDate, region)
    keyService = hash(keyString, service)
    keySigning = hash(keyService, 'aws4_request')
    return keySigning


# assemble the standardized request
time = datetime.datetime.utcnow()
timestamp = time.strftime('%Y%m%dT%H%M%SZ')
datestamp = time.strftime('%Y%m%d')

standardized_resource = '/' + bucket + '/' + object_key
standardized_querystring = request_parameters
standardized_headers = 'host:' + host + '\n' + 'x-amz-date:' + timestamp + '\n'
signed_headers = 'host;x-amz-date'
payload_hash = hashlib.sha256(''.encode('utf-8')).hexdigest()

standardized_request = (http_method + '\n' +
                        standardized_resource + '\n' +
                        standardized_querystring + '\n' +
                        standardized_headers + '\n' +
                        signed_headers + '\n' +
                        payload_hash).encode('utf-8')


# assemble string-to-sign
hashing_algorithm = 'AWS4-HMAC-SHA256'
credential_scope = datestamp + '/' + region + '/' + 's3' + '/' + 'aws4_request'
sts = (hashing_algorithm + '\n' +
       timestamp + '\n' +
       credential_scope + '\n' +
       hashlib.sha256(standardized_request).hexdigest())


# generate the signature
signature_key = createSignatureKey(secret_key, datestamp, region, 's3')
signature = hmac.new(signature_key,
                     (sts).encode('utf-8'),
                     hashlib.sha256).hexdigest()


# assemble all elements into the 'authorization' header
v4auth_header = (hashing_algorithm + ' ' +
                 'Credential=' + access_key + '/' + credential_scope + ', ' +
                 'SignedHeaders=' + signed_headers + ', ' +
                 'Signature=' + signature)


# create and send the request
headers = {'x-amz-date': timestamp, 'Authorization': v4auth_header}
# the 'requests' package autmatically adds the required 'host' header
request_url = endpoint + standardized_resource + standardized_querystring

print('\nSending `%s` request to IBM COS -----------------------' % http_method)
print('Request URL = ' + request_url)
request = requests.get(request_url, headers=headers)

print('\nResponse from IBM COS ----------------------------------')
print('Response code: %d\n' % request.status_code)
print(request.text)

Java 範例

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.time.format.DateTimeFormatter;
import java.time.ZoneId;
import java.time.ZoneOffset;
import java.time.ZonedDateTime;
import java.util.Formatter;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

public class CosHMAC {
    // please don't store credentials directly in code
    private static final String accessKey = System.getenv("COS_HMAC_ACCESS_KEY_ID");
    private static final String secretKey = System.getenv("COS_HMAC_SECRET_ACCESS_KEY");
    // constants
    private static final String httpMethod = "GET";
    private static final String host = "s3.us.cloud-object-storage.appdomain.cloud";
    private static final String region = "us-standard";
    private static final String endpoint = "https://s3.us.cloud-object-storage.appdomain.cloud";
    private static final String bucket = ""; // add a '/' before the bucket name to list buckets
    private static final String objectKey = "";
    private static final String requestParameters = "";

    public static void main(String[] args) {
        try {
            // assemble the standardized request
            ZonedDateTime time = ZonedDateTime.now(ZoneOffset.UTC);
            String datestamp = time.format(DateTimeFormatter.ofPattern("yyyyMMdd"));
            String timestamp = datestamp + "T" + time.format(DateTimeFormatter.ofPattern("HHmmss")) + "Z";

            String standardizedResource = bucket + "/" + objectKey;
            String standardizedQuerystring = requestParameters;
            String standardizedHeaders = "host:" + host + "\n" + "x-amz-date:" + timestamp + "\n";
            String signedHeaders = "host;x-amz-date";
            String payloadHash = hashHex("");

            String standardizedRequest = httpMethod + "\n" +
                standardizedResource + "\n" +
                standardizedQuerystring + "\n" +
                standardizedHeaders + "\n" +
                signedHeaders + "\n" +
                payloadHash;

            // assemble string-to-sign
            String hashingAlgorithm = "AWS4-HMAC-SHA256";
            String credentialScope = datestamp + "/" + region + "/" + "s3" + "/" + "aws4_request";
            String sts = hashingAlgorithm + "\n" +
                timestamp + "\n" +
                credentialScope + "\n" +
                hashHex(standardizedRequest);

            // generate the signature
            byte[] signatureKey = createSignatureKey(secretKey, datestamp, region, "s3");
            String signature = hmacHex(signatureKey, sts);

            // assemble all elements into the "authorization" header
            String v4auth_header = hashingAlgorithm + " " +
                "Credential=" + accessKey + "/" + credentialScope + ", " +
                "SignedHeaders=" + signedHeaders + ", " +
                "Signature=" + signature;

            // create and send the request
            String requestUrl = endpoint + standardizedResource + standardizedQuerystring;
            URL urlObj = new URL(requestUrl);
            HttpURLConnection con = (HttpURLConnection) urlObj.openConnection();
            con.setRequestMethod(httpMethod);

            //add request headers
            con.setRequestProperty("x-amz-date", timestamp);
            con.setRequestProperty("Authorization", v4auth_header);

            System.out.printf("\nSending %s request to IBM COS -----------------------", httpMethod);
            System.out.println("Request URL = " + requestUrl);

            int responseCode = con.getResponseCode();
            System.out.println("\nResponse from IBM COS ----------------------------------");
            System.out.printf("Response code: %d\n\n", responseCode);

            BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
            String inputLine;
            StringBuffer response = new StringBuffer();

            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();

            //print result
            System.out.println(response.toString());

            con.disconnect();
        }
        catch (Exception ex) {
            System.out.printf("Error: %s\n", ex.getMessage());
        }
    }

    private static String toHexString(byte[] bytes) {
		Formatter formatter = new Formatter();

		for (byte b : bytes) {
			formatter.format("%02x", b);
		}

		return formatter.toString();
	}

    private static byte[] hash(byte[] key, String msg) {
        byte[] returnVal = null;
        try {
            SecretKeySpec signingKey = new SecretKeySpec(key, "HmacSHA256");
            Mac mac = Mac.getInstance("HmacSHA256");
            mac.init(signingKey);
            returnVal = mac.doFinal(msg.getBytes("UTF8"));
        }
        catch (Exception ex) {
            throw ex;
        }
        finally {
            return returnVal;
        }
    }

    private static String hmacHex(byte[] key, String msg) {
        String returnVal = null;
        try {
            returnVal = toHexString(hash(key, msg));
        }
        catch (Exception ex) {
            throw ex;
        }
        finally {
            return returnVal;
        }
    }

    private static String hashHex(String msg) {
        String returnVal = null;
        try {
            MessageDigest digest = MessageDigest.getInstance("SHA-256");
            byte[] encodedhash = digest.digest(msg.getBytes(StandardCharsets.UTF_8));
            returnVal = toHexString(encodedhash);
        }
        catch (Exception ex) {
            throw ex;
        }
        finally {
            return returnVal;
        }
    }

    // region is a wildcard value that takes the place of the AWS region value
    // as COS doesn"t use the same conventions for regions, this parameter can accept any string
    private static byte[] createSignatureKey(String key, String datestamp, String region, String service) {
        byte[] returnVal = null;
        try {
            byte[] keyDate = hash(("AWS4" + key).getBytes("UTF8"), datestamp);
            byte[] keyString = hash(keyDate, region);
            byte[] keyService = hash(keyString, service);
            byte[] keySigning = hash(keyService, "aws4_request");
            returnVal = keySigning;
        }
        catch (Exception ex) {
            throw ex;
        }
        finally {
            return returnVal;
        }
    }
}

NodeJS 範例

const crypto = require('crypto');
const moment = require('moment');
const https = require('https');

// please don't store credentials directly in code
const accessKey = process.env.COS_HMAC_ACCESS_KEY_ID;
const secretKey = process.env.COS_HMAC_SECRET_ACCESS_KEY;

const httpMethod = 'GET';
const host = 's3.us.cloud-object-storage.appdomain.cloud';
const region = 'us-standard';
const endpoint = 'https://s3.us.cloud-object-storage.appdomain.cloud';
const bucket = ''; // add a '/' before the bucket name to list buckets
const objectKey = '';
const requestParameters = '';

// hashing and signing methods
function hash(key, msg) {
    var hmac = crypto.createHmac('sha256', key);
    hmac.update(msg, 'utf8');
    return hmac.digest();
}

function hmacHex(key, msg) {
    var hmac = crypto.createHmac('sha256', key);
    hmac.update(msg, 'utf8');
    return hmac.digest('hex');
}

function hashHex(msg) {
    var hash = crypto.createHash('sha256');
    hash.update(msg);
    return hash.digest('hex');
}

// region is a wildcard value that takes the place of the AWS region value
// as COS doesn't use the same conventions for regions, this parameter can accept any string
function createSignatureKey(key, datestamp, region, service) {
    keyDate = hash(('AWS4' + key), datestamp);
    keyString = hash(keyDate, region);
    keyService = hash(keyString, service);
    keySigning = hash(keyService, 'aws4_request');
    return keySigning;
}

// assemble the standardized request
var time = moment().utc();
var timestamp = time.format('YYYYMMDDTHHmmss') + 'Z';
var datestamp = time.format('YYYYMMDD');

var standardizedResource = bucket + '/' + objectKey;
var standardizedQuerystring = requestParameters;
var standardizedHeaders = 'host:' + host + '\n' + 'x-amz-date:' + timestamp + '\n';
var signedHeaders = 'host;x-amz-date';
var payloadHash = hashHex('');

var standardizedRequest = httpMethod + '\n' +
    standardizedResource + '\n' +
    standardizedQuerystring + '\n' +
    standardizedHeaders + '\n' +
    signedHeaders + '\n' +
    payloadHash;

// assemble string-to-sign
var hashingAlgorithm = 'AWS4-HMAC-SHA256';
var credentialScope = datestamp + '/' + region + '/' + 's3' + '/' + 'aws4_request';
var sts = hashingAlgorithm + '\n' +
    timestamp + '\n' +
    credentialScope + '\n' +
    hashHex(standardizedRequest);

// generate the signature
var signatureKey = createSignatureKey(secretKey, datestamp, region, 's3');
var signature = hmacHex(signatureKey, sts);

// assemble all elements into the 'authorization' header
var v4authHeader = hashingAlgorithm + ' ' +
    'Credential=' + accessKey + '/' + credentialScope + ', ' +
    'SignedHeaders=' + signedHeaders + ', ' +
    'Signature=' + signature;

// create and send the request
var authHeaders = {'x-amz-date': timestamp, 'Authorization': v4authHeader}
// the 'requests' package autmatically adds the required 'host' header
console.log(authHeaders);
var requestUrl = endpoint + standardizedResource + standardizedQuerystring

console.log(`\nSending ${httpMethod} request to IBM COS -----------------------`);
console.log('Request URL = ' + requestUrl);

var options = {
    host: host,
    port: 443,
    path: standardizedResource + standardizedQuerystring,
    method: httpMethod,
    headers: authHeaders
}

var request = https.request(options, function (response) {
    console.log('\nResponse from IBM COS ----------------------------------');
    console.log(`Response code: ${response.statusCode}\n`);

    response.on('data', function (chunk) {
        console.log(chunk.toString());
    });
});

request.end();

下一步

您可以在 服務認證 中檢閱認證的文件。 如需鑑別的概觀，請參閱 IBM Cloud Identity and Access Management 服務。