Object Storage Service:Assinatura POST V4

Como funcionam as assinaturas POST

As requisições POST utilizam o algoritmo de assinatura V4. O formulário e a policy garantem conjuntamente a autenticidade da requisição.

<AccessKeyId>/<date>/<region>/oss/aliyun_v4_request

{
  "expiration": "2023-12-03T13:00:00.000Z",
  "conditions": [
    {"bucket": "examplebucket"},
    {"x-oss-signature-version": "OSS4-HMAC-SHA256"},
    {"x-oss-credential": "AKIDEXAMPLE/20231203/cn-hangzhou/oss/aliyun_v4_request"},
    {"x-oss-security-token": "CAIS******"},
    {"x-oss-date": "20231203T121212Z"},
    ["content-length-range", 1, 10],
    ["eq", "$success_action_status", "201"],
    ["starts-with", "$key", "user/eric/"],
    ["in", "$content-type", ["image/jpg", "image/png"]],
    ["not-in", "$cache-control", ["no-cache"]]
  ]
}

Processo de cálculo da assinatura

1. Crie uma policy codificada em UTF-8.

2. Construa a string a ser assinada.

   Codifique a policy em Base64. O resultado é a string a ser assinada.

3. Calcule a chave de assinatura.

   Derive uma chave de assinatura aplicando operações sucessivas de HMAC-SHA256 usando seu AccessKey Secret, data, região e nome do serviço.

4. Calcule a assinatura.

   Assine a string com a chave de assinatura usando HMAC-SHA256 e converta o resultado para uma string hexadecimal. Esta é a assinatura final.

Exemplos de cálculo de assinatura POST

1. O exemplo Java a seguir calcula uma assinatura POST para a policy acima.

   AccessKey credentials

   import com.aliyun.oss.common.utils.BinaryUtil;
   import org.apache.commons.codec.binary.Base64;
   import javax.crypto.Mac;
   import javax.crypto.spec.SecretKeySpec;
   import com.fasterxml.jackson.databind.ObjectMapper; 
   import java.util.Map; 
   import java.util.HashMap; 
   import java.util.List; 
   import java.util.ArrayList; 
   import java.util.Arrays; 
   
   public class Demo {
       public static void main(String[] args) throws Exception {
           // Before you run this code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are set.
           String accesskeyid =  System.getenv().get("OSS_ACCESS_KEY_ID");
           String accesskeysecret =  System.getenv().get("OSS_ACCESS_KEY_SECRET");
   
           // Step 1: Create a policy.
           ObjectMapper mapper = new ObjectMapper();
   
           Map<String, Object> policy = new HashMap<>();
           policy.put("expiration", "2024-12-03T13:00:00.000Z");
   
           List<Object> conditions = new ArrayList<>();
   
           Map<String, String> bucketCondition = new HashMap<>();
           bucketCondition.put("bucket", "examplebucket");
           conditions.add(bucketCondition);
   
           Map<String, String> signatureVersionCondition = new HashMap<>();
           signatureVersionCondition.put("x-oss-signature-version", "OSS4-HMAC-SHA256");
           conditions.add(signatureVersionCondition);
   
           Map<String, String> credentialCondition = new HashMap<>();
           credentialCondition.put("x-oss-credential", accesskeyid + "/20241203/cn-hangzhou/oss/aliyun_v4_request");
           conditions.add(credentialCondition);
   
           Map<String, String> dateCondition = new HashMap<>();
           dateCondition.put("x-oss-date", "20241203T121212Z");
           conditions.add(dateCondition);
   
           conditions.add(Arrays.asList("content-length-range", 1, 10));
           conditions.add(Arrays.asList("eq", "$success_action_status", "201"));
           conditions.add(Arrays.asList("starts-with", "$key", "user/eric/"));
           conditions.add(Arrays.asList("in", "$content-type", Arrays.asList("image/jpg", "image/png")));
           conditions.add(Arrays.asList("not-in", "$cache-control", Arrays.asList("no-cache")));
   
           policy.put("conditions", conditions);
   
           String jsonPolicy = mapper.writeValueAsString(policy);
           // Step 2: Construct the string to sign.
           String stringToSign = new String(Base64.encodeBase64(jsonPolicy.getBytes()));
           System.out.println(stringToSign);
           
           // Step 3: Calculate the signing key.
           byte[] dateKey = hmacsha256(("aliyun_v4" + accesskeysecret).getBytes(), "20241203");
           byte[] dateRegionKey = hmacsha256(dateKey, "cn-hangzhou");
           byte[] dateRegionServiceKey = hmacsha256(dateRegionKey, "oss");
           byte[] signingKey = hmacsha256(dateRegionServiceKey, "aliyun_v4_request");
   
           // Step 4: Calculate the signature.
           byte[] result = hmacsha256(signingKey, stringToSign);
           String signature = BinaryUtil.toHex(result);
           System.out.println("signature:" + signature);
   
       }
   
       public static byte[] hmacsha256(byte[] key, String data) {
           try {
               // Initialize the HMAC key specification, specifying HmacSHA256 as the algorithm and using the provided key.
               SecretKeySpec secretKeySpec = new SecretKeySpec(key, "HmacSHA256");
   
               // Get a Mac instance, specifying HmacSHA256 as the algorithm.
               Mac mac = Mac.getInstance("HmacSHA256");
               // Initialize the Mac object with the key.
               mac.init(secretKeySpec);
   
               // Perform the HMAC calculation. The doFinal method takes the data and returns the resulting hash as a byte array.
               byte[] hmacBytes = mac.doFinal(data.getBytes());
   
               return hmacBytes;
           } catch (Exception e) {
               throw new RuntimeException("Failed to calculate HMAC-SHA256", e);
           }
       }
   }

   Resultado retornado:

   signature:3908473f7dbfb79a102eaaa44ca1edec8d7058ce3bd1c624d59eb437463bd5d6

   Temporary access credentials

   Ao usar credenciais temporárias do STS, obtenha um token de segurança chamando a operação AssumeRole.

   import com.aliyun.oss.common.utils.BinaryUtil;
   import org.apache.commons.codec.binary.Base64;
   import javax.crypto.Mac;
   import javax.crypto.spec.SecretKeySpec;
   import com.aliyun.sts20150401.models.AssumeRoleResponse;
   import com.aliyun.sts20150401.models.AssumeRoleResponseBody;
   import com.aliyun.tea.TeaException;
   import com.fasterxml.jackson.databind.ObjectMapper;
   import java.util.*;
   public class Demo {
   
       // Initialize the STS client.
       public static com.aliyun.sts20150401.Client createStsClient() throws Exception {
           com.aliyun.teaopenapi.models.Config config = new com.aliyun.teaopenapi.models.Config()
                   // Required. Make sure that the OSS_ACCESS_KEY_ID environment variable is set.
                   .setAccessKeyId(System.getenv("OSS_ACCESS_KEY_ID"))
                   // Required. Make sure that the OSS_ACCESS_KEY_SECRET environment variable is set.
                   .setAccessKeySecret(System.getenv("OSS_ACCESS_KEY_SECRET"));
           // Endpoint 
           config.endpoint = "sts.cn-hangzhou.aliyuncs.com";
           return new com.aliyun.sts20150401.Client(config);
       }
   
       // Obtain temporary access credentials from STS.
       public static AssumeRoleResponseBody.AssumeRoleResponseBodyCredentials getCredential() throws Exception {
           com.aliyun.sts20150401.Client client = Demo.createStsClient();
           com.aliyun.sts20150401.models.AssumeRoleRequest assumeRoleRequest = new com.aliyun.sts20150401.models.AssumeRoleRequest()
                   // Required. Make sure that the OSS_STS_ROLE_ARN environment variable is set.
                   .setRoleArn(System.getenv("OSS_STS_ROLE_ARN"))
                   .setRoleSessionName("role_session_name");// Custom session name.
           com.aliyun.teautil.models.RuntimeOptions runtime = new com.aliyun.teautil.models.RuntimeOptions();
           try {
               // If you copy this code, print the API response on your own.
               AssumeRoleResponse response = client.assumeRoleWithOptions(assumeRoleRequest, runtime);
               // The credentials object contains the AccessKeyId, AccessKeySecret, and SecurityToken for subsequent operations.
               return response.body.credentials;
           } catch (TeaException error) {
               // This is for demonstration only. In a production environment, handle exceptions with care and do not ignore them.
               // Error message
               System.out.println(error.getMessage());
               // Troubleshooting URL
               System.out.println(error.getData().get("Recommend"));
               com.aliyun.teautil.Common.assertAsString(error.message);
           } catch (Exception _error) {
               TeaException error = new TeaException(_error.getMessage(), _error);
               // This is for demonstration only. In a production environment, handle exceptions with care and do not ignore them.
               // Error message
               System.out.println(error.getMessage());
               // Troubleshooting URL
               System.out.println(error.getData().get("Recommend"));
               com.aliyun.teautil.Common.assertAsString(error.message);
           }
           return null;
       }
   
       public static void main(String[] args) throws Exception {
   
           AssumeRoleResponseBody.AssumeRoleResponseBodyCredentials sts_data = getCredential();
           String accesskeyid = sts_data.accessKeyId;
           String accesskeysecret = sts_data.accessKeySecret;
           String securitytoken = sts_data.securityToken;
           // Step 1: Create a policy.
           ObjectMapper mapper = new ObjectMapper();
   
           Map<String, Object> policy = new HashMap<>();
           policy.put("expiration", "2024-12-03T13:00:00.000Z");
   
           List<Object> conditions = new ArrayList<>();
   
           Map<String, String> bucketCondition = new HashMap<>();
           bucketCondition.put("bucket", "examplebucket");
           conditions.add(bucketCondition);
   
           Map<String, String> signatureVersionCondition = new HashMap<>();
           signatureVersionCondition.put("x-oss-signature-version", "OSS4-HMAC-SHA256");
           conditions.add(signatureVersionCondition);
           
           Map<String, String> securityTokenCondition = new HashMap<>();
           securityTokenCondition.put("x-oss-security-token", securitytoken);
           conditions.add(securityTokenCondition);
           
           Map<String, String> credentialCondition = new HashMap<>();
           credentialCondition.put("x-oss-credential", accesskeyid + "/20241203/cn-hangzhou/oss/aliyun_v4_request");
           conditions.add(credentialCondition);
   
           Map<String, String> dateCondition = new HashMap<>();
           dateCondition.put("x-oss-date", "20241203T121212Z");
           conditions.add(dateCondition);
   
           conditions.add(Arrays.asList("content-length-range", 1, 10));
           conditions.add(Arrays.asList("eq", "$success_action_status", "201"));
           conditions.add(Arrays.asList("starts-with", "$key", "user/eric/"));
           conditions.add(Arrays.asList("in", "$content-type", Arrays.asList("image/jpg", "image/png")));
           conditions.add(Arrays.asList("not-in", "$cache-control", Arrays.asList("no-cache")));
   
           policy.put("conditions", conditions);
   
           String jsonPolicy = mapper.writeValueAsString(policy);
           // Step 2: Construct the string to sign.
           String stringToSign = new String(Base64.encodeBase64(jsonPolicy.getBytes()));
   
           // Step 3: Calculate the signing key.
           byte[] dateKey = hmacsha256(("aliyun_v4" + accesskeysecret).getBytes(), "20241203");
           byte[] dateRegionKey = hmacsha256(dateKey, "cn-hangzhou");
           byte[] dateRegionServiceKey = hmacsha256(dateRegionKey, "oss");
           byte[] signingKey = hmacsha256(dateRegionServiceKey, "aliyun_v4_request");
   
           // Step 4: Calculate the signature.
           byte[] result = hmacsha256(signingKey, stringToSign);
           String signature = BinaryUtil.toHex(result);
           System.out.println("signature:" + signature);
   
       }
   
       public static byte[] hmacsha256(byte[] key, String data) {
           try {
               // Initialize the HMAC key specification, specifying HmacSHA256 as the algorithm and using the provided key.
               SecretKeySpec secretKeySpec = new SecretKeySpec(key, "HmacSHA256");
   
               // Get a Mac instance, specifying HmacSHA256 as the algorithm.
               Mac mac = Mac.getInstance("HmacSHA256");
               // Initialize the Mac object with the key.
               mac.init(secretKeySpec);
   
               // Perform the HMAC calculation. The doFinal method takes the data and returns the resulting hash as a byte array.
               byte[] hmacBytes = mac.doFinal(data.getBytes());
   
               return hmacBytes;
           } catch (Exception e) {
               throw new RuntimeException("Failed to calculate HMAC-SHA256", e);
           }
       }
   }

   Resultado retornado:

   signature:1e09438f7ad01af6b3e144b42c98929c68f8d090ce07f4c277b18d8b62d0aa02

2. O exemplo Python a seguir calcula uma assinatura POST.

   import base64
   import hmac
   import hashlib
   import os
   
   def hmac_sha256(key, data):
       return hmac.new(key, data.encode('utf-8'), hashlib.sha256).digest()
   
   # Read the AccessKey ID and AccessKey Secret from environment variables.
   accesskeyid = os.getenv('OSS_ACCESS_KEY_ID')
   accesskeysecret = os.getenv('OSS_ACCESS_KEY_SECRET')
   
   # Print the AccessKey ID.
   print(accesskeyid)
   
   # Check if the environment variables were successfully retrieved.
   if not accesskeyid or not accesskeysecret:
       raise ValueError("Necessary environment variables not found: OSS_ACCESS_KEY_ID or OSS_ACCESS_KEY_SECRET")
   
   # Create the policy.
   policy = f'''{{
     "expiration": "2025-01-01T00:00:00.000Z",
     "conditions": [
       {{"x-oss-signature-version": "OSS4-HMAC-SHA256"}},
       {{"x-oss-credential": "{accesskeyid}/20241105/cn-hangzhou/oss/aliyun_v4_request"}},
       {{"x-oss-date": "20241105T065000Z"}}
     ]
   }}'''
   
   # Print the policy.
   print(policy)
   
   # Calculate the string to sign.
   string_to_sign = base64.b64encode(policy.encode('utf-8')).decode('utf-8')
   print(string_to_sign)
   
   # Calculate the signing key.
   date_key = hmac_sha256(f"aliyun_v4{accesskeysecret}".encode('utf-8'), "20241105")
   date_region_key = hmac_sha256(date_key, "cn-hangzhou")
   date_region_service_key = hmac_sha256(date_region_key, "oss")
   signing_key = hmac_sha256(date_region_service_key, "aliyun_v4_request")
   
   # Calculate the signature.
   result = hmac_sha256(signing_key, string_to_sign)
   signature = result.hex()
   print("signature:", signature)

   Resultado retornado:

   signature:9e85d56429245283b1aca5bc2dc31e0020b95ac2de9e9b81b496994db602ba1e