post - 如何在 golang 中编码 POST 策略 - 基于浏览器的上传到 amazon S3？

Question

我正在尝试将图像文件上传到 amazon s3。设置如下:

Web 服务器:golang
前端:用于测试的简单 html 表单

引用本文档:http://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-post-example.html

我引用了上面文档中提供的示例并尝试了这个:
http://play.golang.org/p/3zn5fSDasK

  package main

  import "fmt"
  import "encoding/base64"

  func main() {
         bytePolicy := []byte(`{ 
                    "expiration": "2013-08-06T12:00:00.000Z",
                    "conditions": [
                             {"bucket": "examplebucket"},
                             ["starts-with", "$key", "user/user1/"],
                             {"acl": "public-read"},
                             {"success_action_redirect": "http://acl6.s3.amazonaws.com/successful_upload.html"},
                             ["starts-with", "$Content-Type", "image/"],
                             {"x-amz-meta-uuid": "14365123651274"},
                             ["starts-with", "$x-amz-meta-tag", ""],
                             {"x-amz-credential":"AKIAIOSFODNN7EXAMPLE/20130806/us-east-1/s3/aws4_request"},
                             {"x-amz-algorithm": "AWS4-HMAC-SHA256"},
                             {"x-amz-date": "20130806T000000Z" }
                      ]
                  }`)
        fmt.Println(base64.StdEncoding.EncodeToString(bytePolicy))
 }

我得到的结果

   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

亚马逊教程链接上的base 64编码策略:

   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

为什么我的 base64 编码策略与亚马逊的不匹配？

Answer 1

仅仅是因为生成这些 base64 字符串的 2 个 JSON 源文本具有不同的缩进和不同的内容，如下所示(它们不等于逐个字符)。

解码这两个 base64 字符串，您将看到不同之处。您可以使用程序(不一定是 Go)或简单地使用像 this one 这样的在线服务来做到这一点。 .

您不必担心缩进，这在 JSON 中无关紧要。但是当您使用 Base64 对文本进行编码时，它会对源的所有字符进行编码，包括用于缩进的空格和制表符，因此不同的缩进将导致不同的 Base64 编码形式。

但是对比2个解码后的JSON，还有其他的不同:

第一个:

"expiration": "2013-08-06T12:00:00.000Z"
"success_action_redirect": "http://acl6.s3.amazonaws.com/successful_upload.html"

第二个:

"expiration": "2013-08-07T12:00:00.000Z"
"success_action_redirect": "http://examplebucket.s3.amazonaws.com/successful_upload.html"

---

完整解码的 JSON 文本:

第一个:

{ 
                        "expiration": "2013-08-06T12:00:00.000Z",
                        "conditions": [
                                 {"bucket": "examplebucket"},
                                ["starts-with", "$key", "user/user1/"],
                                 {"acl": "public-read"},
                                 {"success_action_redirect": "http://acl6.s3.amazonaws.com/successful_upload.html"},
                                ["starts-with", "$Content-Type", "image/"],
                                {"x-amz-meta-uuid": "14365123651274"},
                                ["starts-with", "$x-amz-meta-tag", ""],

                                {"x-amz-credential":"AKIAIOSFODNN7EXAMPLE/20130806/us-east-1/s3/aws4_request"},
                                {"x-amz-algorithm": "AWS4-HMAC-SHA256"},
                               {"x-amz-date": "20130806T000000Z" }
                          ]
                    }

第二个:

{ "expiration": "2013-08-07T12:00:00.000Z",
  "conditions": [
    {"bucket": "examplebucket"},
    ["starts-with", "$key", "user/user1/"],
    {"acl": "public-read"},
    {"success_action_redirect": "http://examplebucket.s3.amazonaws.com/successful_upload.html"},
    ["starts-with", "$Content-Type", "image/"],
    {"x-amz-meta-uuid": "14365123651274"},
    ["starts-with", "$x-amz-meta-tag", ""],

    {"x-amz-credential": "AKIAIOSFODNN7EXAMPLE/20130806/us-east-1/s3/aws4_request"},
    {"x-amz-algorithm": "AWS4-HMAC-SHA256"},
    {"x-amz-date": "20130806T000000Z" }
  ]
}