• POST Object
  • Construction of policy：
    • Expiration
    • Condition:
      • Condition type
      • Conditions field
  • Signature Construction:

POST Object

• Description: upload a file by post (based on browser form).

• Request：

POST / HTTP/1.1
Host: <Your-Bucket-Name>.ss.bscstorage.com
Content-Length: <length>

Content-Type:multipart/form-data; boundary=----WebKitFormBoundary1dIjDASRYXQm6DNA

------WebKitFormBoundary1dIjDASRYXQm6DNA
Content-Disposition: form-data; name="key"

destinationProject/${filename}
------WebKitFormBoundary1dIjDASRYXQm6DNA
Content-Disposition: form-data; name="success_action_redirect"

http://123.abc.com/1.php?f=1111.txt
------WebKitFormBoundary1dIjDASRYXQm6DNA
Content-Disposition: form-data; name="AWSAccessKeyId"

00M414ZO0X30
------WebKitFormBoundary1dIjDASRYXQm6DNA
Content-Disposition: form-data; name="Policy"

eyJleHBpcmF0aW9uIjoiMjAxMi0wNi0wNlQwNjozOTo0MS4wMDBaIiwiY29uZGl0aW9ucyI6W3siYnVja2V0IjoiczN4cC5zM3dhdGNoIn0sWyJzdGFydHMtd2l0aCIsIiRrZXkiLCJhbmdlbFwvIl1dfQ==
------WebKitFormBoundary1dIjDASRYXQm6DNA
Content-Disposition: form-data; name="Signature"

VK6Kw4kRqW2e84ZIX2cV2QqHo58=
------WebKitFormBoundary1dIjDASRYXQm6DNA
Content-Disposition: form-data; name="file"; filename="112233.txt"
Content-Type: text/plain

------WebKitFormBoundary1dIjDASRYXQm6DNA
Content-Disposition: form-data; name="submit"

上传
------WebKitFormBoundary1dIjDASRYXQm6DNA-

• Form elements:

Construction of policy：

The policy is a JSON document encoded with UTF-8 and Base64, which specifies the conditions that the request must meet and is used to authenticate the content. Depending on how you design policy documents, you can use them for each upload, each user, all uploads, or other designs that meet your needs.

{
    "expiration": "2014-04-10T08:55:34.000Z",

    "conditions": [

        {
            "bucket": "my-bucket-name"
        },

        {
            "acl": "private"
        },

        [
            "starts-with", "$key", "my_prefix/"
        ],

        [
            "content-length-range", 0, 52428800
        ]
    ]
}

• Description of the above example:

  • Upload must be before "2014-04-10t08:55:34.000z".
  • Upload the file to the bucket named "my bucket name".
  • starts-with：$key must start with "my_ Prefix" / '(the "$key" in the policy must be preceded by "$"). If the $key value is empty, there is no prefix before the file name.
  • content-length-range：The file size must be within the specified range.
  • Finally, Base64 encode the policy and set it to the value of the form policy.expiration:

Expiration

Expiration is used to specify the expiration time of the policy. The expiration date of the policy is specified in ISO 8601 UTC date format. For example, "2007-12-01t12:00:00.000z" specifies that expiration is required in the policy.

Condition:

Condition is used to verify the content of the uploaded object and the fields filled in by the form

Condition type

Conditions field

The conditions in the policy document verify the content of the uploaded object. Each form field you specify in the form（AWSAccessKeyId、Signature、 file、Policy except）Can be used as a condition

Signature Construction:

• Encoding policy with UTF-8
• Encode the policy in UTF-8 form with Base64
• Use HMAC SHA-1 and your secret key to convert your policy. Finally, Base64 coding is performed. For example, when using PHP，base64_encode( hash_hmac( "sha1", $policy, $SECRETKEY, true ) );
• Set the final value to the value of the form signature.

Finally generated HTML form:

<form method="post" action="http://my-bucket.<?=c('api_host');?>/" enctype="multipart/form-data">
    <input type="hidden" name="AWSAccessKeyId" value="您的accesskey" />
    <input type="hidden" name="key" value="my_prefix/${filename}" />
    <input type="hidden" name="acl" value="private" />
    <input type="hidden" name="success_action_status" value="201" />
    <input type="hidden" name="Policy" value="eyJleHBpcmF0aW9uIjoiMjAxNC0wNC0xMFQwOToxNzozMC4wMDBaIiwiY29uZGl0aW9ucyI6W3siYnVja2V0IjoiY2xvdWQxMjMqwqwsdifsdGFydHMtd2l0aCIsIiRrZXkiLCJteWZpbGVzLyJdLFsic3RhcnRzLXdpdGgiLCIkQ29udGVudC1UeXBlIiwiIl0sWyJzdGFydHMtd2l0aCIsIiRDb250ZW50LURpc3Bvc2l0aW9uIiwiIl0seyJ1aWQiOiIxMjMifSxbImNvbnRlbnQtbGVuZ3RoLXJhbmdlIiwwLDUyNDI4ODAwXV19" />
    <input type="hidden" name="Signature" value="HnOSk3kfx5LFtn4CIiFcSglQUXc=" />
    <input type="file" name="file" />
    <input type="submit" value="上传" />
</form>

• matters needing attention：
  • The URI after the POST request can only be “/”
  • success_action_redirect：Specify the URL to be redirected by the client after successful upload.
  • key：The variable ${filename} will be automatically replaced with the file name of the uploaded file