Defeat SVGCaptcha

Question

I came across SVGCaptcha, and immediately knew it was a bad idea.

I would like you to show just how bad an idea this is by extracting the validation code from the SVG images that code produces.

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An example image looks like this:

Here is the source of the example image:

<?xml version="1.0" encoding="utf-8"?><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20010904//EN"
        "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd">
    <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" xml:space="preserve"
             width="200" height="40"
    > <rect x="0" y="0" width="200" height="40" 
        style="stroke: none; fill: none;" >
        </rect> <text style="fill: #4d9363;" x="5" y="34" font-size="20" transform="translate(5, 34) rotate(-17) translate(-5, -34)">8</text>
<text style="fill: #be8b33;" x="125" y="29" font-size="21" transform="translate(125, 29) rotate(17) translate(-125, -29)">f</text>
<text style="fill: #d561ff;" x="45" y="35" font-size="20" transform="translate(45, 35) rotate(-2) translate(-45, -35)">4</text>
<text style="fill: #3de754;" x="85" y="31" font-size="21" transform="translate(85, 31) rotate(-9) translate(-85, -31)">8</text>
<text style="fill: #5ed4bf;" x="25" y="33" font-size="22" transform="translate(25, 33) rotate(16) translate(-25, -33)">u</text>
<text style="fill: #894aee;" x="105" y="28" font-size="25" transform="translate(105, 28) rotate(9) translate(-105, -28)">1</text>
<text style="fill: #e4c437;" x="65" y="32" font-size="20" transform="translate(65, 32) rotate(17) translate(-65, -32)">x</text>
</svg>

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The input is the SVG image, which is a textual format.

The only real restriction is that your code must produce the values in the correct order.
The input <text> elements are in random order so you have to pay attention to the x attribute in the <text> tag

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Score is the number of bytes in the code

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Since the code currently does two transforms that cancel each-other out you can ignore them, but if you do take them in consideration, go ahead and take a 30% reduction from your score.

Answer 1

Bash, 63 56 39 bytes

cat<<_|grep -o 'x=.*>'|cut -c4-|sort -n|grep -o '>.</t'|cut -c2

grep -o 'x=.*>'|cut -c4-|sort -n|grep -o '>.</t'|cut -c2

grep -o 'x=.*<'|sort -k1.4n|rev|cut -c2

Note: requires cat, grep, sort, rev, and cut. Takes input from stdin. The output is separated by line breaks on stdout. Make sure to press CTRL+D (not COMMAND+D on Mac) when finished entering the CAPTCHA. Input must be followed by a newline and then '_'.

EDIT: Saved 13 bytes.

EDIT 2: Saved 20 bytes thanks to @manatwork!

Answer 2

CJam, 26 bytes

q"x="/2>{'"/1=i}${'>/1=c}/

Try it online in the CJam interpreter.

How it works

q     e# Read all input from STDIN.
"x="/ e# Split it at occurrences of "x=".
2>    e# Discard the first two chunks (head and container).
{     e# Sort the remaining chunks by the following key:
  '"/ e#   Split at occurrences of '"'.
  1=  e#   Select the second chunk (digits of x="<digits>").
  i   e#   Cast to integer.
}$    e#
{     e# For each of the sorted chunks:
  '>/ e#   Split at occurrences of '>'.
  1=  e#   Select the second chunk.
  c   e#   Cast to character.
}/    e#

Answer 3

JavaScript, 95 93 91 bytes

l=[],r=/x="(\d*).*>(.)/g;while(e=r.exec(document.lastChild.innerHTML))l[e[1]]=e[2];l.join``

edit: -2 bytes changing documentRoot to lastChild; -2 bytes changing join('') to join``, thanks Vɪʜᴀɴ

Enter code in the browser console on a page containg the SVG in question, writes to console output.

Answer 4

Perl, 40 bytes

39 bytes code + 1 for -n

$a[$1]=$2 for/x="(.+)".+(.)</g}{print@a

Example:

perl -ne '$a[$1]=$2 for/x="(.+)".+(.)</g}{print@a' <<< '<example from above>'
8u4x81f

Answer 5

Bash + GNU utilities, 53

grep -Po '(?<=x=").*(?=<)'|sort -n|grep -Po '(?<=>).'

Like this answer, output is one char per line.

Answer 6

Befunge, 79 bytes

It feels like it should be possible to golf at least one more byte off of this, but I've been working on it for a couple of days now, and this is as good as I could get it.

<%*:"~"*"~"_~&45*/99p1v-">":_|#`0:~<
#,:#g7-#:_@^-+*"x~=":+_~99g7p>999p#^_>>#1+

Try it online!

Explanation

Make the execution direction right-to-left, and wrap around to start the main loop.
Read a char from stdin, and test for the end-of-file value.
If it's not end-of-file, check if it's a >.
If it's not a >, add it to the value on the stack which tracks the last two characters, and check if the current pair matches x=.
If not, multiply by 126 and mod with 126² to drop the oldest value from the pair and make space for the next character.
Wrap around again to repeat the main loop.
When an x= pair is encountered, skip the next character (the quote), read an integer (the x value), and divide by 20. This becomes the current offset which is saved for later.
When a > is encountered, read the next character (typically one of the captcha letters), and save that at the current offset in an "array". Reset the offset to 9, so the captcha letter won't be overwritten when later > characters are encountered.
Finally, when then end-of-file is reached, iterate over the 7 values saved in the array and output them one by one. That should give you all the captcha letters in the correct order.

I'm glossing over some of the details here, since the code paths overlap each other in ways which are a little difficult to explain, but it should give you a general idea of how the algorithm works.

Answer 7

Perl 6, 68 bytes

say [~] lines.map({/'x="'(\d+).*(.)\</??(+$0=>$1)!!()}).sort».value

Answer 8

V, 28 26 25 24 bytes

d5j́x=
ún
J́">
lH$dÍî

Try it online!

Explanation:

d5j              delete first 6 lines
   Í<0x81>x=     In every line, replace everything up to x=" (inclusive) by nothing
ún               Sort numerically
J                Join line (closing </svg>) with next line
 Í<0x81>">       In every line, replace everything up to "> by nothing
l␖H$d            Visual block around closing </text> tags, delete
     Íî          In every line, replace \n by nothing.

HexDump:

00000000: 6435 6acd 8178 3d0a fa6e 0a4a cd81 223e  d5j..x=..n.J..">
00000010: 0a6c 1648 2464 cdee                      .l.H$d..

Answer 9

QuadS, 49 bytes

∊c[⍋⊃x c←↓⍎¨@1⍉(⊢⍴⍨2,⍨.5×≢)3↓⍵]
x="(\d+)
>(.)<
\1

Try it online!

Finds x values (digit-runs after x=") and "letters" (pinned by closing and opening tags), then executes the following APL (where ⍵ is the list of found x values and letters, in order of appearance):

3↓⍵ drop the first three elements (spaces around <rect…/rect> and the <rect's x value).

(…) apply the following tacit function on that:

 ≢ the number of remaining items

 .5× halve that

 2,⍨ append a two

 ⊢⍴⍨ reshape to that shape (i.e. an n×2 matrix)

⍉ transpose (to a 2×n matrix)

⍎¨@1 execute each string in the first row (turning them into numbers)

↓ split the matrix into two vectors (one per row)

x c← store those two in x (x values) and c (characters) respectively

⊃ pick the first (x)

⍋ grade up (the indices into x which would sort x)

c[…] use that to index into c

∊ ϵnlist (flatten) because each letter is a string by itself

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The equivalent APL expression of the entire QuadS program is:

∊c[⍋⊃x c←↓⍎¨@1⍉(⊢⍴⍨2,⍨.5×≢)3↓'x="(\d+)"' '>(.)<'⎕S'\1'⊢⎕]

Answer 10

Python2, 129 bytes

import re,sys
print''.join(t[1] for t in sorted(re.findall(r'(\d+), -\d+\)"\>(.)\</t',sys.stdin.read()),key=lambda t:int(t[0])))

Takes the HTML source on stdin, produces code on stdout.

Answer 11

Mathematica, 106 bytes

""<>(v=ImportString[#~StringDrop~157,"XML"][[2,3,4;;;;2]])[[;;,3]][[Ordering[FromDigits/@v[[;;,2,2,2]]]]]&

Note: The input needs to be in exactly the format specified by the example.

Answer 12

Java 8, 197 173 bytes

import java.util*;s->{String a[]=s.split("x=\""),r="";Map m=new TreeMap();for(int i=2;i<a.length;m.put(new Long(a[i].split("\"")[0]),a[i++].split(">|<")[1]));return m.values();}

Outputs a java.util.Collection of characters.

Explanation:

Try it online.

import java.util*;            // Required import for Map and TreeMap
s->{                          // Method with String as both parameter and return-type
  String a[]=s.split("x=\""), //  Split the input by `x="`, and store it as String-array
         r="";                //  Result-String, starting empty
  Map m=new TreeMap();        //  Create a sorted key-value map
  for(int i=2;                //  Skip the first two items in the array,
      i<a.length;             //  and loop over the rest
    m.put(new Long(a[i].split("\"")[0]),
                              //   Split by `"` and use the first item as number-key
          a[i++].split(">|<")[1]));
                              //   Split by `>` AND `<`, and use the second item as value
    return m.values();}       //  Return the values of the sorted map as result

Answer 13

Gema, 65 characters

x\="<D>*\>?=@set{$1;?}
?=
\Z=${5}${25}${45}${65}${85}${105}${125}

In Gema there is no sorting, but fortunately is not even needed.

Sample run:

bash-4.4$ gema 'x\="<D>*\>?=@set{$1;?};?=;\Z=${5}${25}${45}${65}${85}${105}${125}' < captcha.svg
8u4x81f

Answer 14

XMLStarlet, 46 characters

xmlstarlet sel -t -m //_:text -s A:N:U @x -v .

Hopefully this is valid solution as XMLStarlet is transpiler that generates and executes XSLT code, which is a Turing complete language.

Sample run:

bash-4.4$ xmlstarlet sel -t -m //_:text -s A:N:U @x -v . < captcha.svg 
8u4x81f

Answer 15

PHP, 96 bytes

Given that $i is the input string

preg_match_all('|x="(\d+).*(.)\<|',$i,$m);$a=array_combine($m[1],$m[2]);ksort($a);echo join($a);

Answer 16

Clean, 277 150 bytes

Yay pattern matching!

import StdEnv,StdLib
?s=map snd(sort(zip(map(toInt o toString)[takeWhile isDigit h\\['" x="':h]<-tails s],[c\\[c:t]<-tails s|take 7 t==['</text>']])))

Try it online!

Defines the function ?, taking [Char] and giving [Char].