You must sign all HTTP or HTTPS API requests to ensure security. Alibaba Cloud uses the request signature to verify the identity of a request sender. Alibaba Cloud implements symmetric encryption with an AccessKey pair to verify the identity of the request sender.

Note
  • The AccessKey pair serves as logon credentials that are used to call API operations, and the username and password are used to log on to the Elastic Compute Service (ECS) console. The AccessKey ID is used to verify identities of users, and the AccessKey secret is used to encrypt and verify signature strings. You must keep your AccessKey secret strictly confidential. For more information, see Create an AccessKey pair.
  • ECS provides SDKs in multiple programming languages, including third-party SDKs, to facilitate complex signature calculation. Download the SDK package.

Step 1: Create a canonicalized query string

  1. Create a canonicalized query string by arranging the request parameters (including all common and operation-specific parameters except Signature) in alphabetical order.
    Note If you use the GET method to send a request, the request parameters are included as a part of the request URL. The first parameter follows the question mark (?) in the URL, and the other parameters follow an ampersand (&).
  2. Encode the canonicalized query string in UTF-8. Use UTF-8 to encode the names and values of the request parameters based on RFC 3986.
    Encoding rules:
    • Uppercase letters, lowercase letters, digits, and some special characters such as hyphens (-), underscores (_), periods (.), and tildes (~) do not need to be encoded.
    • Other characters must be percent encoded in %XY format. XY represents the ASCII code of the characters in hexadecimal notation. For example, double quotation marks (") are encoded as %22.
    • Extended UTF-8 characters are encoded in %XY%ZA... format.
    • Spaces must be encoded as %20. Do not encode spaces as plus signs (+).

      The preceding encoding method is similar to but slightly different from the application/x-www-form-urlencoded MIME-type encoding algorithm.

      If you use java.net.URLEncoder in the Java standard library, use percentEncode to encode request parameters and their values. In the encoded query string, replace the plus sign (+) with %20, the asterisk (*) with %2A, and %7E with a tilde (~). In this way, you can obtain an encoded string that matches the preceding encoding rules.

      private static final String ENCODING = "UTF-8";
      private static String percentEncode(String value) throws UnsupportedEncodingException {
      return value ! = null ? URLEncoder.encode(value, ENCODING).replace("+", "%20").replace("*", "%2A").replace("%7E", "~") : null;
      }
  3. Connect the encoded parameter names and values with equal signs (=).
  4. Connect the encoded request parameters with ampersands (&).

Now, you have obtained a canonicalized query string (CanonicalizedQueryString) that follows the request syntax. For more information, see Call VPC APIs.

Step 2: Create a string-to-sign from the encoded canonicalized query string

  1. Create StringToSign.
    You can also use percentEncode to encode the canonicalized query string created in the previous step. Take the following steps to create a string-to-sign:
    StringToSign=
      HTTPMethod + "&" + // HTTPMethod: HTTP method used to make the request, such as GET.
      percentEncode("/") + "&" + // percentEncode("/"): Encode the forward slash (/) in UTF-8 as %2F.
      percentEncode(CanonicalizedQueryString) //Encode the canonicalized query string created in Step 1.
  2. Calculate the hash-based message authentication code (HMAC) value of the StringToSign, as defined in RFC 2104. Use the Secure Hash Algorithm 1 (SHA-1) algorithm to calculate the HMAC value. Encode the HMAC value in Base64 to obtain the signature string as shown below.
    Signature = Base64( HMAC-SHA1( AccessSecret, UTF-8-Encoding-Of(StringToSign) ) )
    Note When you calculate the signature, the key value specified by RFC 2104 is your AccessKeySecret with an ampersand (&) which has an ASCII value of 38. For more information, see Create an AccessKey pair.
  3. Encode the Signature parameter based on RFC 3986 and add it to the canonicalized query string.

Example 1: Concatenate parameters

The DescribeRegions operation is called to query Alibaba Cloud regions in the following example. This example shows the signature process when AccessKeyID is set to testid and AccessKeySecret is set to testsecret:

  1. Compose and encode a string-to-sign.
    http://vpc.aliyuncs.com/?Timestamp=2016-02-23T12%3A46%3A24Z&Format=XML&AccessKeyId=testid&Action=DescribeRegions&SignatureMethod=HMAC-SHA1&SignatureNonce=3ee8c1b8-83d3-44af-a94f-4e0ad82fd6cf&Version=2016-04-28&SignatureVersion=1.0
  2. Create a string-to-sign.
    GET&%2F&AccessKeyId%3Dtestid%26Action%3DDescribeRegions%26Format%3DXML%26SignatureMethod%3DHMAC-SHA1%26SignatureNonce%3D3ee8c1b8-83d3-44af-a94f-4e0ad82fd6cf%26SignatureVersion%3D1.0%26Timestamp%3D2016-02-23T12%253A46%253A24Z%26Version%3D2016-04-28
  3. Calculate the signature. If AccessKeySecret is set to testsecret, the key value used for calculation is testsecret&. The calculated signature is OLeaidS1JvxuMvnyHOwuJ+uX5qY=. This example uses the Java Base64 encoding method.
    Signature = Base64( HMAC-SHA1( AccessSecret, UTF-8-Encoding-Of(StringToSign) ) )
  4. Add the Signature=OLeaidS1JvxuMvnyHOwuJ%2BuX5qY%3D string that has been encoded based on RFC 3986 to the URL.
    http://vpc.aliyuncs.com/?SignatureVersion=1.0&Action=DescribeRegions&Format=XML&SignatureNonce=3ee8c1b8-83d3-44af-a94f-4e0ad82fd6cf&Version=2016-04-28&AccessKeyId=testid&Signature=OLeaidS1JvxuMvnyHOwuJ%2BuX5qY%3D&SignatureMethod=HMAC-SHA1&Timestamp=2016-02-23T12%253A46%253A24Z

You can use browsers or tools such as cURL and Wget to initiate an HTTP request through the new URL. The HTTP request calls the DescribeRegions operation to query the Alibaba Cloud region list.

Example 2: Use the standard library of the programming language

The DescribeRegions operation is called to query Alibaba Cloud regions in the following example. This example shows the signature process when AccessKeyID is set to testid and AccessKeySecret is set to testsecret, and all request parameters are placed in a Java Map<String, String> object:

  1. Predefine an encoding method.
    private static final String ENCODING = "UTF-8";
    private static String percentEncode(String value) throws UnsupportedEncodingException {
      return value ! = null ? URLEncoder.encode(value, ENCODING).replace("+", "%20").replace("*", "%2A").replace("%7E", "~") : null;
    }
  2. Predefine the time format for the Timestamp parameter. The Timestamp parameter must conform to the ISO8601 specification and must be in UTC+0.
    private static final String ISO8601_DATE_FORMAT = "yyyy-MM-dd'T'HH:mm:ss'Z'";
    private static String formatIso8601Date(Date date) {
      SimpleDateFormat df = new SimpleDateFormat(ISO8601_DATE_FORMAT);
      df.setTimeZone(new SimpleTimeZone(0, "GMT"));
      return df.format(date);
    }
  3. Create a query string.
    final String HTTP_METHOD = "GET";
    Map parameters = new HashMap();
    //Specify request parameters.
    parameters.put("Action", "DescribeRegions");
    parameters.put("Version", "2016-04-28");
    parameters.put("AccessKeyId", "testid");
    parameters.put("Timestamp", formatIso8601Date(new Date()));
    parameters.put("SignatureMethod", "HMAC-SHA1");
    parameters.put("SignatureVersion", "1.0");
    parameters.put("SignatureNonce", UUID.randomUUID().toString());
    parameters.put("Format", "XML");
    // Arrange request parameters.
    String[] sortedKeys = parameters.keySet().toArray(new String[]{});
    Arrays.sort(sortedKeys);
    final String SEPARATOR = "&";
    // Create a string-to-sign.
    StringBuilder stringToSign = new StringBuilder();
    stringToSign.append(HTTP_METHOD).append(SEPARATOR);
    stringToSign.append(percentEncode("/")).append(SEPARATOR);
    StringBuilder canonicalizedQueryString = new StringBuilder();
    for(String key : sortedKeys) {
    // Encode the key and the value.
      canonicalizedQueryString.append("&")
      .append(percentEncode(key)).append("=")
      .append(percentEncode(parameters.get(key)));
    }
    // Encode the canonicalized query string.
    stringToSign.append(percentEncode(
      canonicalizedQueryString.toString().substring(1)));
  4. Calculate the signature. If AccessKeySecret is set to testsecret, the key used for calculation is testsecret&. The calculated signature is OLeaidS1JvxuMvnyHOwuJ%2BuX5qY%3D.
    // The following code demonstrates how to calculate the signature:
    final String ALGORITHM = "HmacSHA1";
    final String ENCODING = "UTF-8";
    key = "testsecret&";
    Mac mac = Mac.getInstance(ALGORITHM);
    mac.init(new SecretKeySpec(key.getBytes(ENCODING), ALGORITHM));
    byte[] signData = mac.doFinal(stringToSign.getBytes(ENCODING));
    String signature = new String(Base64.encodeBase64(signData));

    Encode the Signature parameter based on RFC 3986 and add the parameter to the URL. The new URL is:

    http://vpc.aliyuncs.com/?SignatureVersion=1.0&Action=DescribeRegions&Format=XML&SignatureNonce=3ee8c1b8-83d3-44af-a94f-4e0ad82fd6cf&Version=2016-04-28&AccessKeyId=testid&Signature=OLeaidS1JvxuMvnyHOwuJ%2BuX5qY%3D&SignatureMethod=HMAC-SHA1&Timestamp=2016-02-23T12%253A46%253A24Z
  5. Send HTTP requests by using a browser, cURL, or wget.
    <DescribeRegionsResponse>
     <Regions>
         <Region>
             <LocalName>China (Qingdao)</LocalName>
             <RegionId>cn-qingdao</RegionId>
         </Region>
         <Region>
             <LocalName>China (Hangzhou)</LocalName>
             <RegionId>cn-hangzhou</RegionId>
         </Region>
     </Regions>
     <RequestId>833C6B2C-E309-45D4-A5C3-03A7A7A48ACF</RequestId>
    </DescribeRegionsResponse>

The returned result lists regions and region IDs. If you set Format to JSON when you submit a request, the response is returned in the JSON format instead of the XML format. For more information, see Error codes.