ASP刷新验证码---高安全性很难破解

yoken 阅读：1603 2009-10-20 23:22:00 评论：0

将以下代码保存为 checkcode.asp
<%
'------------------
'图片验证码
'netdust
'05-8-29 发布
'以前的图片验证码很容易被破解，所以在其基础上进行改进，即使知道源代码
'也很难破解。
'干扰次数每加一  ->  穷举法的代价提高约100*100倍
'适当设定杂点几率可以有效降低软件识别正确率
'05-12-20 修正了一个错误
'------------------

Option Explicit

Call Com_CreatValidCode("GetCode")

Rem 生成验证码图片
Sub Com_CreatValidCode(pSN)
Const codeLen = 4 '验证码位数
Const cOdds = 3 '杂点出现的机率
Const dbtTimes = 1 '干扰次数（安全考虑，最好不要小于3）

Const cAmount = 10 '字库数量
Const cCode = "0123456789" '字库对应的字符
Const UnitWidth = 16 '字宽(要为4的倍数)
Const UnitHeight = 13 '字高
Const DotsLimit = 5 '每次删除有效点的上限(避免无法人为识别)
Const tryCount = 5 '避免删除有效点超过上限的尝试次数限制

'-----------

Randomize
Dim i, ii, iii

' 禁止缓存
Response.Expires = -9999
Response.AddHeader "Pragma","no-cache"
Response.AddHeader "cache-ctrol","no-cache"
Response.ContentType = "Image/BMP"

' 颜色的数?字符，背景)
Dim vColorData(1)
vColorData(0) = ChrB(0) & ChrB(0) & ChrB(0)  ' 蓝0，绿0，红0（黑色）
vColorData(1) = ChrB(255) & ChrB(255) & ChrB(255) ' 蓝250，绿236，红211（浅蓝色）

' 字符的数据(可以自己修改，如果修改了尺寸，记得把前面的设定也改了)
Dim vNumberData(9)
vNumberData(0) = "1111000000001111111000000000011111100111111001111110011111100111111001111110011111100111111001111110011111100111111001111110011111100111111001111110011111100111111001111110011111100000000001111111000000001111"
vNumberData(1) = "1111110001111111111100000111111111100000011111111100110001111111111111000111111111111100011111111111110001111111111111000111111111111100011111111111110001111111111111000111111111100000000011111110000000001111"
vNumberData(2) = "1111110000011111111110000000111111110001110011111110001111001111111111111001111111111111001111111111111001111111111111001111111111111001111111111111001111001111111001111100111111100000000011111110000000001111"
vNumberData(3) = "1111100000011111111100000000111111100111111001111110011111001111111111111001111111111110001111111111111000111111111111111001111111111111110011111110011111100111111001111110011111110000000011111111100000011111"
vNumberData(4) = "1111111100111111111110110011111111110011001111111111001100111111111001110011111111001111001111111000000000000011100000000000001111111111001111111111111100111111111111110011111111111111001111111111111100111111"
vNumberData(5) = "1110000000000111110011111111111111001111111111111100111111111111110011111111111111001100000011111100000111100111111111111110011111111111111001111111111111100111110011111110011111001111111001111110000000001111"
vNumberData(6) = "1111110000011111111110000000111111110011111001111110011111111111111001111111111111100100000111111110000000001111111000111110011111100111111001111110011111100111111001111110011111110000000011111111100000011111"
vNumberData(7) = "1110000000000111111000000000011111100111111001111110011111100111111111111100111111111111110011111111111110011111111111110011111111111111001111111111111100111111111111110011111111111111001111111111111100111111"
vNumberData(8) = "1111100000011111111100000000111111100111111001111110011111100111111001111110011111110000000011111111000000001111111100111100111111100111111001111110011111100111111001111110011111110000000011111111100000011111"
vNumberData(9) = "1111100000011111111100000000111111100111111001111110011111100111111001111110011111110000000001111111000000100111111111111110011111111111111001111111111111100111111001111100111111110000000011111111100000011111"

' 随机产生字符
Dim vCodes
ReDim vCode(codeLen-1)
For i = 0 To codeLen-1
   vCode(i) = Int(Rnd * cAmount)
   vCodes = vCodes & Mid(cCode, vCode(i) + 1, 1)
   vCode(i) = pcd_doubter(vNumberData(vCode(i)),UnitWidth,UnitHeight,DotsLimit,tryCount,dbtTimes)
Next

Session(pSN) = vCodes  '记录入Session

' 输出图像文件头
Response.BinaryWrite ChrB(66) & ChrB(77) & Num2ChrB(54+UnitWidth*UnitHeight*CodeLen*3,4) & ChrB(0) & ChrB(0) &_
   ChrB(0) & ChrB(0) & ChrB(54) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(40) & ChrB(0) &_
   ChrB(0) & ChrB(0) & Num2ChrB(UnitWidth*CodeLen,4) & Num2ChrB(UnitHeight,4) &_
   ChrB(1) & ChrB(0)

' 输出图像信息头
Response.BinaryWrite ChrB(24) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & Num2ChrB(UnitWidth*UnitHeight*CodeLen*3,4) &_
   ChrB(18) & ChrB(11) & ChrB(0) & ChrB(0) & ChrB(18) & ChrB(11) &_
   ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) & ChrB(0) &_
   ChrB(0) & ChrB(0)

For i = UnitHeight-1 To 0 Step -1  ' 历经所有行
   For ii = 0 To codeLen-1  ' 历经所有字
   For iii = 1 To UnitWidth ' 历经所有像素
      If Rnd * 99 + 1 >= cOdds Then ' 逐行、逐字、逐像素地输出图像数据
      Response.BinaryWrite vColorData(Mid(vCode(ii), i * UnitWidth + iii, 1))
      Else ' 随机生成杂点
      Response.BinaryWrite vColorData(1-CInt(Mid(vCode(ii), i * UnitWidth + iii, 1)))
      End If
   Next
   Next
Next
End Sub

Rem 对单个字的点阵进行干扰
Rem 干扰思想：在点阵范围内随机产生2个端点，进行连线，以位移较大的一方做横轴，先将连线上的点删除，再将被删除点的纵轴方向上方或下方的点（随机确定）移向被删除点，移动后的空白用背景色补充
Function pcd_doubter(ByVal str,UnitWidth,UnitHeight,DotsLimit,tryCount,dbtTimes)
Randomize
Dim x1,x2,y1,y2,xOffSet,yOffSet,direction,flag,rows,step,yu,yuStr,i,ii,iii,f1,f2
For f1=1 To dbtTimes '干扰次数
For f2=1 To tryCount '避免删除有效点超过上限的尝试次数限制
'随机确定2个端点
x1 = int(Rnd*UnitWidth)
x2 = int(Rnd*UnitWidth)
y1 = int(Rnd*UnitHeight)
y2 = int(Rnd*UnitHeight)
'x,y位移量
xOffSet = Abs(x2-x1)
yOffSet = Abs(y2-y1)
If xOffSet >= yOffSet Then '以位移量较大方做横轴
direction = "x"
ReDim ary(xOffSet) '用来记录连线各点y值
'x2,y2存储x值较大的点
If x2 < x1 Then
i = x1
x1 = x2
x2 = i
i = y1
y1 = y2
y2 = i
End If
'判断从x1->x2在纵轴方向上是增是减
If y2 >= y1 Then
flag = 1
Else
flag = -1
End If
'下面计算连线上点的分布（先是平均分配各行的点，然后随机分配剩余的点到各行）
rows = yOffSet + 1 '所占行数
step = (xOffSet+1) \ rows '各行平均分配的点
yu = (xOffSet+1) Mod rows '剩余的点数
ReDim ary2(rows-1) '用来记录剩余点的随机分配
While yu > 0
i = int(Rnd*rows)
ary2(i) = ary2(i)&"." '被分配到的行则加一个字符"."
yu = yu - 1
WEnd
iii = 0
'将连线的点信息记录到数组
For i=0 To rows-1
For ii=1 To step+Len(ary2(i))
ary(iii) = y1 + i*flag
iii = iii + 1
Next
Next
ii = 0
'统计连线上有效点的数量
For i=0 To xOffSet
If pcd_getDot(x1+i,ary(i),str,UnitWidth) = "0" Then ii = ii + 1
Next
Else
'这里是以y为横轴，原理与x时相同
direction = "y"
ReDim ary(yOffSet)
If y2 < y1 Then
i = x1
x1 = x2
x2 = i
i = y1
y1 = y2
y2 = i
End If
If x2 >= x1 Then
flag = 1
Else
flag = -1
End If
rows = xOffSet + 1
step = (yOffSet+1) \ rows
yu = (yOffSet+1) Mod rows
ReDim ary2(rows-1)
While yu > 0
i = int(Rnd*10)
If i < rows Then
ary2(i) = ary2(i)&"."
yu = yu - 1
End If
WEnd
iii = 0
For i=0 To rows-1
For ii=1 To step+Len(ary2(i))
ary(iii) = x1 + i*flag
iii = iii + 1
Next
Next
ii = 0
For i=0 To yOffSet
If pcd_getDot(ary(i),y1+i,str,UnitWidth) = "0" Then ii = ii + 1
Next
End If
'如未超过有效点上限则跳出循环，执行干扰
If ii <= DotsLimit Then Exit For
Next

If direction = "x" Then
'随机确定在纵轴方向上或下进行移动
If int(Rnd*10) > 4 Then
'变量连线上的点
For i=0 To xOffSet
'遍历移动
For ii=ary(i) To 1 Step -1
Call pcd_setDot(x1+i,ii,str,pcd_getDot(x1+i,ii-1,str,UnitWidth),UnitWidth)
Next
'添补空白
Call pcd_setDot(x1+i,0,str,"1",UnitWidth)
Next
Else
For i=0 To xOffSet
For ii=ary(i) To UnitHeight-2
Call pcd_setDot(x1+i,ii,str,pcd_getDot(x1+i,ii+1,str,UnitWidth),UnitWidth)
Next
Call pcd_setDot(x1+i,UnitHeight-1,str,"1",UnitWidth)
Next
End If
Else
If int(Rnd*10) > 4 Then
For i=0 To yOffSet
For ii=ary(i) To 1 Step -1
Call pcd_setDot(ii,y1+i,str,pcd_getDot(ii-1,y1+i,str,UnitWidth),UnitWidth)
Next
Call pcd_setDot(0,y1+i,str,"1",UnitWidth)
Next
Else
For i=0 To yOffSet
For ii=ary(i) To UnitWidth-2
Call pcd_setDot(ii,y1+i,str,pcd_getDot(ii+1,y1+i,str,UnitWidth),UnitWidth)
Next
Call pcd_setDot(UnitWidth-1,y1+i,str,"1",UnitWidth)
Next
End If
End If
Next
pcd_doubter = str
End Function

Rem 得到某点的字符
Function pcd_getDot(x,y,str,UnitWidth)
pcd_getDot = Mid(str,x+1+y*UnitWidth,1)
End Function

Rem 设置某点的字符
Sub pcd_setDot(x,y,ByRef str,newDot,UnitWidth)
str = Left(str,x+y*UnitWidth) & newDot & Right(str,Len(str)-x-y*UnitWidth-1)
End Sub

Rem 将数字转为bmp需要的格式 lens是目标字节长度
Function Num2ChrB(num,lens)
Dim ret,i
ret = ""
While (num>0)
ret = ret & ChrB(num mod 256)
num = num \ 256
WEnd
For i=Lenb(ret) To lens-1
ret = ret & chrB(0)
Next
Num2ChrB = ret
End Function
%>

使用如下代码调用验证码
<img src="code.asp" style="cursor:hand" onclick="this.src='code.asp';" alt="看不清?点一下" />

验证函数
Function codepass()
      Dim CodeStr
      CodeStr = Trim(request("CodeStr"))
      If CStr(Session("GetCode")) = CStr(CodeStr) And CodeStr <> "" Then
         codepass = True
         'Session("GetCode")=empty
      Else
         codepass = False
         'Session("GetCode")=empty
      End If
End Function

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