奇怪的 Base64 编码/解码问题 [英] Strange Base64 encode/decode problem

问题描述

我使用的是 Grails 1.3.7.我有一些使用内置 base64Encode 函数和 base64Decode 函数的代码.在我编码一些二进制数据然后解码结果字符串并将其写入新文件的简单测试用例中，这一切都很好.在这种情况下，文件是相同的.

I'm using Grails 1.3.7. I have some code that uses the built-in base64Encode function and base64Decode function. It all works fine in simple test cases where I encode some binary data and then decode the resulting string and write it to a new file. In this case the files are identical.

但后来我编写了一个 Web 服务，该服务将 base64 编码数据作为 POST 调用中的参数.虽然base64数据的长度与我传入函数的字符串相同，但是base64数据的内容正在被修改.我花了几天的时间调试这个，最后写了一个测试控制器，将 base64 中的数据传递给 post，并使用正确的 base64 编码数据获取本地文件的名称，如下所示:

But then I wrote a web service that took the base64 encoded data as a parameter in a POST call. Although the length of the base64 data is identical to the string I passed into the function, the contents of the base64 data are being modified. I spend DAYS debugging this and finally wrote a test controller that passed the data in base64 to post and also took the name of a local file with the correct base64 encoded data, as in:

data=AAA-base-64-data...&testFilename=/name/of/file/with/base64data

在测试函数中，我将传入数据参数中的每个字节与测试文件中的相应字节进行了比较.我发现不知何故输入数据参数中的每个+"字符都被替换为"(空格，序数 ascii 32).嗯?什么能做到这一点?

Within the test function I compared every byte in the incoming data parameter with the appropriate byte in the test file. I found that somehow every "+" character in the input data parameter had been replaced with a " " (space, ordinal ascii 32). Huh? What could have done that?

为了确定我是对的，我添加了一行内容:

To be sure I was correct, I added a line that said:

data = data.replaceAll(' ', '+')

果然数据解码完全正确.我用任意长的二进制文件尝试过它，现在每次都可以使用.但是我终生无法弄清楚如何修改帖子中的数据参数以将 ord(43) 字符转换为 ord(32)?我知道加号是 base64 规范中两个有点平台相关的字符之一，但鉴于我现在在同一台机器上进行编码和解码，我非常困惑是什么导致了这种情况.当然我有一个修复"，因为我可以让它工作，但我对我不理解的修复"感到紧张.

and sure enough the data decoded exactly right. I tried it with arbitrarily long binary files and it now works every time. But I can't figure out for the life of me what would be modifying the data parameter in the post to convert the ord(43) character to ord(32)? I know that the plus sign is one of the 2 somewhat platform dependent characters in the base64 spec, but given that I am doing the encoding and decoding on the same machine for now I am super puzzled what caused this. Sure I have a "fix" since I can make it work, but I am nervous about "fixes" that I don't understand.

代码太大，无法在此处发布，但我得到了像这样的 base64 编码:

The code is too big to post here, but I get the base64 encoding like so:

def inputFile = new File(inputFilename)
def rawData =  inputFile.getBytes()
def encoded = rawData.encodeBase64().toString()

然后我将编码后的字符串写入新的文件中，以便稍后使用它进行测试.如果我重新加载该文件，我会得到相同的 rawData:

I then write that encoded string out to new a file so I can use it for testing later. If I load that file back in as so I get the same rawData:

def encodedFile = new File(encodedFilename)
String encoded = encodedFile.getText()
byte[] rawData = encoded.decodeBase64()

所以这一切都很好.现在假设我将编码"变量添加到 POST 函数的参数中，如下所示:

So all that is good. Now assume I take the "encoded" variable and add it to a param to a POST function like so:

String queryString = "data=$encoded"
String url = "http://localhost:8080/some_web_service"

def results = urlPost(url, queryString)

def urlPost(String urlString, String queryString) {
    def url = new URL(urlString)
    def connection = url.openConnection()
    connection.setRequestMethod("POST")
    connection.doOutput = true

    def writer = new OutputStreamWriter(connection.outputStream)
    writer.write(queryString)
    writer.flush()
    writer.close()
    connection.connect()

    return (connection.responseCode == 200) ? connection.content.text : "error                         $connection.responseCode, $connection.responseMessage"
}

在网络服务端，在控制器中我得到如下参数:

on the web service side, in the controller I get the parameter like so:

String data = params?.data
println "incoming data parameter has length of ${data.size()}" //confirm right size

//unless I run the following line, the data does not decode to the same source
data = data.replaceAll(' ', '+')

//as long as I replace spaces with plus, this decodes correctly, why?
byte[] bytedata = data.decodeBase64()

抱歉我的长篇大论，但我真的很想明白为什么我必须用加号替换空格"才能正确解码.请求参数中使用的加号有问题吗?

Sorry for the long rant, but I'd really love to understand why I had to do the "replace space with plus sign" to get this to decode correctly. Is there some problem with the plus sign being used in a request parameter?

推荐答案

Whatever populates params 期望请求是 URL 编码的表单(特别是 application/x-www-form-urlencoded，其中+"表示空格)，但您没有对其进行 URL 编码.我不知道你的语言提供了什么功能，但在伪代码中，queryString 应该由

Whatever populates params expects the request to be a URL-encoded form (specifically, application/x-www-form-urlencoded, where "+" means space), but you didn't URL-encode it. I don't know what functions your language provides, but in pseudo code, queryString should be constructed from

concat(uri_escape("data"), "=", uri_escape(base64_encode(rawBytes)))

简化为

concat("data=", uri_escape(base64_encode(rawBytes)))

+"字符将被替换为%2B".

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