Amazon.S3.Util.S3PostUploadSignedPolicy.GetSignedPolicyV4 C# (CSharp) Метод

        public static S3PostUploadSignedPolicy GetSignedPolicyV4(string policy, AWSCredentials credentials, RegionEndpoint region)
        {
            var signedAt = AWSSDKUtils.CorrectedUtcNow;

            ImmutableCredentials iCreds = credentials.GetCredentials();
            var algorithm = "AWS4-HMAC-SHA256";
            var dateStamp = Runtime.Internal.Auth.AWS4Signer.FormatDateTime(signedAt, AWSSDKUtils.ISO8601BasicDateFormat);
            var dateTimeStamp = Runtime.Internal.Auth.AWS4Signer.FormatDateTime(signedAt, AWSSDKUtils.ISO8601BasicDateTimeFormat);
            var credentialString = string.Format(CultureInfo.InvariantCulture, "{0}/{1}/{2}/{3}/{4}/", iCreds.AccessKey, dateStamp, region.SystemName, "s3", Runtime.Internal.Auth.AWS4Signer.Terminator);

            Dictionary<string, string> extraConditions = new Dictionary<string, string> {
                { S3Constants.PostFormDataXAmzCredential, credentialString },
                { S3Constants.PostFormDataXAmzAlgorithm, algorithm },
                { S3Constants.PostFormDataXAmzDate, dateTimeStamp }
            };
            if (iCreds.UseToken) { extraConditions[S3Constants.PostFormDataSecurityToken] = iCreds.Token; }

            var policyBytes = addConditionsToPolicy(policy, extraConditions);

            var base64Policy = Convert.ToBase64String(policyBytes);

            var signingKey = Runtime.Internal.Auth.AWS4Signer.ComposeSigningKey(iCreds.SecretKey, region.SystemName, dateStamp, "s3");

            var signature = AWSSDKUtils.ToHex(Runtime.Internal.Auth.AWS4Signer.ComputeKeyedHash(SigningAlgorithm.HmacSHA256, signingKey, base64Policy), true);

            return new S3PostUploadSignedPolicy
            {
                Policy = base64Policy,
                Signature = signature,
                AccessKeyId = iCreds.AccessKey,
                SecurityToken = iCreds.Token,
                SignatureVersion = "4",
                Algorithm = algorithm,
                Date = dateTimeStamp,
                Credential = credentialString
            };
        }