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delphi - 多部分/表单数据请求的 Indy MIME 解码返回尾随 CR/LF

转载 作者:可可西里 更新时间:2023-11-01 15:20:16 26 4
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Indy 10.6 修订版 5128 似乎包含一项更改,该更改破坏了以下用于 HTTP 表单上传的代码。

接收到的数据在末尾包含两个附加字节,即 CR/LF 对。

通读 5127 和 5128 之间更改的代码行并没有找到根本原因。

我会在找到时间时尝试调试它并在此处发布结果(但也许有人更快)。

这是一个独立的演示应用程序,它在 http://127.0.0.1:8080

显示了一个 HTML 上传表单
program IndyMultipartUploadDemo;

{$APPTYPE CONSOLE}

uses
IdHTTPServer, IdCustomHTTPServer, IdContext, IdSocketHandle, IdGlobal,
IdMessageCoder, IdGlobalProtocols, IdMessageCoderMIME, IdMultiPartFormData,
SysUtils, Classes;

type
TMimeHandler = procedure(var VDecoder: TIdMessageDecoder;
var VMsgEnd: Boolean; const Response: TIdHTTPResponseInfo) of object;

TMyServer = class(TIdHTTPServer)
private
procedure ProcessMimePart(var VDecoder: TIdMessageDecoder;
var VMsgEnd: Boolean; const Response: TIdHTTPResponseInfo);
function IsHeaderMediaType(const AHeaderLine, AMediaType: String): Boolean;
function MediaTypeMatches(const AValue, AMediaType: String): Boolean;
function GetUploadFolder: string;
procedure HandleMultipartUpload(Request: TIdHTTPRequestInfo; Response:
TIdHTTPResponseInfo; MimeHandler: TMimeHandler);
public
procedure InitComponent; override;
procedure DoCommandGet(AContext: TIdContext;
ARequestInfo: TIdHTTPRequestInfo; AResponseInfo: TIdHTTPResponseInfo); override;
end;

procedure Demo;
var
Server: TMyServer;
begin
ReportMemoryLeaksOnShutdown := True;

Server := TMyServer.Create;
try
try
Server.Active := True;
except
on E: Exception do
begin
WriteLn(E.ClassName + ' ' + E.Message);
end;
end;
WriteLn('Hit any key to terminate.');
ReadLn;
finally
Server.Free;
end;
end;

procedure TMyServer.InitComponent;
var
Binding: TIdSocketHandle;
begin
inherited;

Bindings.Clear;
Binding := Bindings.Add;
Binding.IP := '127.0.0.1';
Binding.Port := 8080;

KeepAlive := True;
end;

procedure TMyServer.DoCommandGet(AContext: TIdContext;
ARequestInfo: TIdHTTPRequestInfo; AResponseInfo: TIdHTTPResponseInfo);
begin
AResponseInfo.ContentType := 'text/html';
AResponseInfo.CharSet := 'UTF-8';

if ARequestInfo.CommandType = hcGET then
begin
AResponseInfo.ContentText :=
'<!DOCTYPE HTML>' + #13#10
+ '<html>' + #13#10
+ ' <head>' + #13#10
+ ' <title>Multipart Upload Example</title>' + #13#10
+ ' </head>' + #13#10
+ ' <body> ' + #13#10
+ ' <form enctype="multipart/form-data" method="post">' + #13#10
+ ' <fieldset>' + #13#10
+ ' <legend>Standard file upload</legend>' + #13#10
+ ' <label>File input</label>' + #13#10
+ ' <input type="file" class="input-file" name="upload" />' + #13#10
+ ' <button type="submit" class="btn btn-default">Upload</button>' + #13#10
+ ' </fieldset>' + #13#10
+ ' </form>' + #13#10
+ ' </body>' + #13#10
+ '</html>' + #13#10;
end
else
begin
if ARequestInfo.CommandType = hcPOST then
begin
if IsHeaderMediaType(ARequestInfo.ContentType, 'multipart/form-data') then
begin
HandleMultipartUpload(ARequestInfo, AResponseInfo, ProcessMimePart);
end;
end;
end;
end;

// based on code on the Indy and Winsock Forum articles
// http://forums2.atozed.com/viewtopic.php?f=7&t=10924
// http://embarcadero.newsgroups.archived.at/public.delphi.internet.winsock/201107/1107276163.html

procedure TMyServer.ProcessMimePart(var VDecoder: TIdMessageDecoder;
var VMsgEnd: Boolean; const Response: TIdHTTPResponseInfo);
var
LMStream: TMemoryStream;
LNewDecoder: TIdMessageDecoder;
UploadFile: string;
begin
LMStream := TMemoryStream.Create;
try
LNewDecoder := VDecoder.ReadBody(LMStream, VMsgEnd);
if VDecoder.Filename <> '' then
begin
try
LMStream.Position := 0;
Response.ContentText := Response.ContentText
+ Format('<p>%s %d bytes</p>' + #13#10,
[VDecoder.Filename, LMStream.Size]);

// write stream to upload folder
UploadFile := GetUploadFolder + VDecoder.Filename;
LMStream.SaveToFile(UploadFile);
Response.ContentText := Response.ContentText
+ '<p>' + UploadFile + ' written</p>';

except
LNewDecoder.Free;
raise;
end;
end;
VDecoder.Free;
VDecoder := LNewDecoder;
finally
LMStream.Free;
end;
end;

function TMyServer.IsHeaderMediaType(const AHeaderLine, AMediaType: String): Boolean;
begin
Result := MediaTypeMatches(ExtractHeaderItem(AHeaderLine), AMediaType);
end;

function TMyServer.MediaTypeMatches(const AValue, AMediaType: String): Boolean;
begin
if Pos('/', AMediaType) > 0 then begin
Result := TextIsSame(AValue, AMediaType);
end else begin
Result := TextStartsWith(AValue, AMediaType + '/');
end;
end;

function TMyServer.GetUploadFolder: string;
begin
Result := ExtractFilePath(ParamStr(0)) + 'upload\';
ForceDirectories(Result);
end;

procedure TMyServer.HandleMultipartUpload(Request: TIdHTTPRequestInfo;
Response: TIdHTTPResponseInfo; MimeHandler: TMimeHandler);
var
LBoundary, LBoundaryStart, LBoundaryEnd: string;
LDecoder: TIdMessageDecoder;
LLine: string;
LBoundaryFound, LIsStartBoundary, LMsgEnd: Boolean;
begin
LBoundary := ExtractHeaderSubItem(Request.ContentType, 'boundary',
QuoteHTTP);
if LBoundary = '' then
begin
Response.ResponseNo := 400;
Response.CloseConnection := True;
Response.WriteHeader;
Exit;
end;

LBoundaryStart := '--' + LBoundary;
LBoundaryEnd := LBoundaryStart + '--';

LDecoder := TIdMessageDecoderMIME.Create(nil);
try
TIdMessageDecoderMIME(LDecoder).MIMEBoundary := LBoundary;
LDecoder.SourceStream := Request.PostStream;
LDecoder.FreeSourceStream := False;

LBoundaryFound := False;
LIsStartBoundary := False;
repeat
LLine := ReadLnFromStream(Request.PostStream, -1, True);
if LLine = LBoundaryStart then
begin
LBoundaryFound := True;
LIsStartBoundary := True;
end
else if LLine = LBoundaryEnd then
begin
LBoundaryFound := True;
end;
until LBoundaryFound;

if (not LBoundaryFound) or (not LIsStartBoundary) then
begin
Response.ResponseNo := 400;
Response.CloseConnection := True;
Response.WriteHeader;
Exit;
end;

LMsgEnd := False;
repeat
TIdMessageDecoderMIME(LDecoder).MIMEBoundary := LBoundary;
LDecoder.SourceStream := Request.PostStream;
LDecoder.FreeSourceStream := False;

LDecoder.ReadHeader;
case LDecoder.PartType of
mcptText, mcptAttachment:
begin
MimeHandler(LDecoder, LMsgEnd, Response);
end;
mcptIgnore:
begin
LDecoder.Free;
LDecoder := TIdMessageDecoderMIME.Create(nil);
end;
mcptEOF:
begin
LDecoder.Free;
LMsgEnd := True;
end;
end;
until (LDecoder = nil) or LMsgEnd;
finally
LDecoder.Free;
end;
end;

begin
Demo;
end.

最佳答案

目前的SVN版本是5203,所以你的更新有点落后。

我在带有 IE11 的 XE2 中使用修订版 5203 按原样测试了您的代码。

我上传了一个测试.pas文件,它在upload文件夹中大了53个字节。我可以确认解码前的原始 PostStream 数据是正确的。

是的,我确实在文件末尾看到了一个额外的 CRLF,这与 TIdMessageDecoderMIME 解码非二进制非 base64/QP 编码数据的方式有关(您的示例就是这样做的不是)。它逐行读取数据,对每一行进行解码,在不使用二进制传输编码时,将解码后的行写入带有新换行符的目标流。该逻辑没有考虑到 MIME 边界前面的换行符属于边界,而不属于边界之前的数据。 MIME 规范对此非常明确,但 Indy 尚未将非 base64 数据考虑在内。

文件大小的其余差异都与非 ASCII 字符被转换为 $3F 字节序列有关,包括 UTF-8 BOM。这是因为 PostStream 数据在 TIdMessageDecoderMIME.ReadBody() 中被解码为 7 位 ASCII,因为没有 Content-Transfer-Encoding header 与文件数据一起发送,因此由于 RFC 2045 第 6.1 节中的以下声明,Indy 默认为 ASCII:

"Content-Transfer-Encoding: 7BIT" is assumed if the Content-Transfer-Encoding header field is not present.

但是,第 6.4 节中的以下内容似乎与 6.1 相矛盾:

Any entity with an unrecognized Content-Transfer-Encoding must be treated as if it has a Content-Type of "application/octet-stream", regardless of what the Content-Type header field actually says.

ReadBody() 处理这两种情况,但是首先检查 6.1,因此 Indy 假设一个 7bit 编码,然后取消它对 6.4 的处理,因为 7bit 不是无法识别的编码。除非假设缺失的 Content-Transfer-Encoding 应该被视为无法识别的编码,而 Indy 目前不会这样做。

上传的实际Content-Typeapplication/octet-stream,这意味着8位编码。当我在应用第 6.1 节时更新 ReadBody() 以将 application/octet-stream 视为 8bit 而不是 7bit ,所有问题都消失了:

if LContentTransferEncoding = '' then begin
// RLebeau 04/08/2014: According to RFC 2045 Section 6.1:
// "Content-Transfer-Encoding: 7BIT" is assumed if the
// Content-Transfer-Encoding header field is not present."
if IsHeaderMediaType(LContentType, 'application/mac-binhex40') then begin {Do not Localize}
LContentTransferEncoding := 'binhex40'; {do not localize}
end

// START FIX!!
else if IsHeaderMediaType(LContentType, 'application/octet-stream') then begin {Do not Localize}
LContentTransferEncoding := '8bit'; {do not localize}
end
// END FIX!!

else begin
LContentTransferEncoding := '7bit'; {do not localize}
end;
end

上传的文件是正确的文件大小,字节被正确解码和写入,没有将非 ASCII 序列转换为 $3F 序列,并且文件末尾没有额外的 CRLF。

我将不得不进一步调查这个问题,看看是否有更好的方法来处理这种差异。我已经在 Indy 的问题跟踪器中为它开了票。同时,如果您修补您的 Indy 副本,您就有了解决方法。

关于delphi - 多部分/表单数据请求的 Indy MIME 解码返回尾随 CR/LF,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/27257577/

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