如何在golang中對POST策略進行編碼 - 基於瀏覽器的上傳到amazon S3？

Question

我想上傳一個圖像文件到亞馬遜s3。設置如下：

Web服務器：golang
前端：用於測試

簡單的HTML形式。在本文檔參考：http://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-post-example.html

我所提到的上述文獻中所提供的示例和嘗試這樣：
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)) 
} 

我這個

01得到的結果

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 

基地64編碼政策，這是對亞馬遜教程鏈接：

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 

爲什麼我的base64編碼的政策，不與亞馬遜的匹配嗎？

Answer 1

只是因爲生成這些base64字符串的2個JSON源文本具有不同的縮進和不同的內容（如下所示）（它們不等於char-by-char）。

解碼兩個base64字符串，你會看到不同之處。您可以使用程序（不一定是Go）執行此操作，也可以只使用在線服務，如this one。

你不應該擔心縮進，它在JSON中並不重要。但是，當您使用Base64對文本進行編碼時，它會對包含用於縮進的空格和製表符的所有字符進行編碼，因此不同的縮進將導致不同的Base64編碼形式。

但對比2解碼JSON，也有其他方面的差異：

第一招：

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

第二屆一個：

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

---

完全解碼JSON文本：

第一招：

{ 
         "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" } 
          ] 
        } 

：第二個：

{ "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" } 
    ] 
}