Hack 89. Syndicate Encrypted Content

Publish sensitive data securely and decrypt it on the fly.

I have a problem. It's actually a pretty common problem. I have data that I want to syndicate to myself, but I don't want you to see it. It's private. Now this data could be my credit card balance, my Google AdSense earnings, or internal bug reports for the day job. Whatever it is, I want the information in a form suitable for syndication but not available to everyone.

There is a solution. I could password-protect my feed. But that causes a problem, because my aggregator would then need to know my password. Now, my aggregator of choice is Bloglines, and I'm sure they're nice folks, but I really don't want to give them my password. One security breach, and my credit card history will be splattered across the Web.

The solution is to have a user script that detects the encrypted content and, using the right key, decrypts the encrypted content. I can continue to use Bloglines to poll the feed and present me with new items as they appear, but the decryption is done in my browser.

So, here is the whole scenario:

1. My content, which is going to sit inside the description element of an RSS feed, is going to be encrypted.

2. That feed is syndicated.

3. I will subscribe to that feed in Bloglines (or any other web-based aggregator).

4. When I view items in that feed in Bloglines, the description is initially displayed encrypted, but the Greasemonkey script detects the encrypted content and decrypts it on the fly and replaces the encrypted content with the decrypted content.

Here is an example of the microformat we're using to transport our encrypted content:

 <div  > <p>The following data is encrypted. Please install the SecureSyndication Greasemonkey script to view the encrypted content. </p> <div >WORK:C7FDD…15C4AC0643B86</div> </div> 

The outer div has a class of "encrypted blowfish", which means that the contents of div are encrypted. (Blowfish is the actual name of the encryption algorithm. I'm not making that up.) The content of <div > is the encrypted data. The first thing in the encrypted data is a key name, then a colon, and then the Blowfish-encrypted content. This allows different keys to be used for different feeds; the decryption script can have an array of keys and look up the password for each one when it's time to decrypt the data.

If there are other elements in the div, they are ignored. That lets us put a nice paragraph in there explaining what is going on to those who are unfamiliar with encrypted content. When our user script runs, it will decrypt the data and replace the innerHTML of the outer div with that decrypted content, thus overwriting the explanation. If someone subscribes to the feed who is not running the decryption script (or doesn't have the right password associated with this key), he will see the explanatory paragraph and the original encrypted data.

10.6.1. The Code

This script runs on Bloglines using a JavaScript implementation of Bruce Schneier's Blowfish algorithm. The rest of the code loops over all the div elements with a class attribute that contains "encrypted blowfish". For each block of encrypted content, we break the content at the colon to get the key name and the encrypted data. We create a new Blowfish context, initialize it with the indicated private key, decrypt the contents, and replace the outer div element with the decrypted data.

Save the following user script as securesyndication.user.js:

 // ==UserScript== // @name   Secure Syndication // @namespace   http://bitworking.org/projects/securesyndication/script/ // @include   http://bloglines.com/* // @include   http://www.bloglines.com/* // @include   http://bitworking.org/projects/securesyndication/* // @description   Allows decrypting content in syndication feeds // ==/UserScript== keys = {"WORK": "TESTKEY"}; N = 16; var ORIG_P = [ 0x243F6A88, 0x85A308D3, 0x13198A2E, 0x03707344, 0xA4093822, 0x299F31D0, 0x082EFA98, 0xEC4E6C89, 0x452821E6, 0x38D01377, 0xBE5466CF, 0x34E90C6C, 0xC0AC29B7, 0xC97C50DD, 0x3F84D5B5, 0xB5470917, 0x9216D5D9, 0x8979FB1B ]; var ORIG_S = []; ORIG_S[0] = [ 0xD1310BA6, 0x98DFB5AC, 0x2FFD72DB, 0xD01ADFB7, 0xB8E1AFED, 0x6A267E96, 0xBA7C9045, 0xF12C7F99, 0x24A19947, 0xB3916CF7, 0x0801F2E2, 0x858EFC16, 0x636920D8, 0x71574E69, 0xA458FEA3, 0xF4933D7E, 0x0D95748F, 0x728EB658, 0x718BCD58, 0x82154AEE, 0x7B54A41D, 0xC25A59B5, 0x9C30D539, 0x2AF26013, 0xC5D1B023, 0x286085F0, 0xCA417918, 0xB8DB38EF, 0x8E79DCB0, 0x603A180E, 0x6C9E0E8B, 0xB01E8A3E, 0xD71577C1, 0xBD314B27, 0x78AF2FDA, 0x55605C60, 0xE65525F3, 0xAA55AB94, 0x57489862, 0x63E81440, 0x55CA396A, 0x2AAB10B6, 0xB4CC5C34, 0x1141E8CE, 0xA15486AF, 0x7C72E993, 0xB3EE1411, 0x636FBC2A, 0x2BA9C55D, 0x741831F6, 0xCE5C3E16, 0x9B87931E, 0xAFD6BA33, 0x6C24CF5C, 0x7A325381, 0x28958677, 0x3B8F4898, 0x6B4BB9AF, 0xC4BFE81B, 0x66282193, 0x61D809CC, 0xFB21A991, 0x487CAC60, 0x5DEC8032, 0xEF845D5D, 0xE98575B1, 0xDC262302, 0xEB651B88, 0x23893E81, 0xD396ACC5, 0x0F6D6FF3, 0x83F44239, 0x2E0B4482, 0xA4842004, 0x69C8F04A, 0x9E1F9B5E, 0x21C66842, 0xF6E96C9A, 0x670C9C61, 0xABD388F0, 0x6A51A0D2, 0xD8542F68, 0x960FA728, 0xAB5133A3, 0x6EEF0B6C, 0x137A3BE4, 0xBA3BF050, 0x7EFB2A98, 0xA1F1651D, 0x39AF0176, 0x66CA593E, 0x82430E88, 0x8CEE8619, 0x456F9FB4, 0x7D84A5C3, 0x3B8B5EBE, 0xE06F75D8, 0x85C12073, 0x401A449F, 0x56C16AA6, 0x4ED3AA62, 0x363F7706, 0x1BFEDF72, 0x429B023D, 0x37D0D724, 0xD00A1248, 0xDB0FEAD3, 0x49F1C09B, 0x075372C9, 0x80991B7B, 0x25D479D8, 0xF6E8DEF7, 0xE3FE501A, 0xB6794C3B, 0x976CE0BD, 0x04C006BA, 0xC1A94FB6, 0x409F60C4, 0x5E5C9EC2, 0x196A2463, 0x68FB6FAF, 0x3E6C53B5, 0x1339B2EB, 0x3B52EC6F, 0x6DFC511F, 0x9B30952C, 0xCC814544, 0xAF5EBD09, 0xBEE3D004, 0xDE334AFD, 0x660F2807, 0x192E4BB3, 0xC0CBA857, 0x45C8740F, 0xD20B5F39, 0xB9D3FBDB, 0x5579C0BD, 0x1A60320A, 0xD6A100C6, 0x402C7279, 0x679F25FE, 0xFB1FA3CC, 0x8EA5E9F8, 0xDB3222F8, 0x3C7516DF, 0xFD616B15, 0x2F501EC8, 0xAD0552AB, 0x323DB5FA, 0xFD238760, 0x53317B48, 0x3E00DF82, 0x9E5C57BB, 0xCA6F8CA0, 0x1A87562E, 0xDF1769DB, 0xD542A8F6, 0x287EFFC3, 0xAC6732C6, 0x8C4F5573, 0x695B27B0, 0xBBCA58C8, 0xE1FFA35D, 0xB8F011A0, 0x10FA3D98, 0xFD2183B8, 0x4AFCB56C, 0x2DD1D35B, 0x9A53E479, 0xB6F84565, 0xD28E49BC, 0x4BFB9790, 0xE1DDF2DA, 0xA4CB7E33, 0x62FB1341, 0xCEE4C6E8, 0xEF20CADA, 0x36774C01, 0xD07E9EFE, 0x2BF11FB4, 0x95DBDA4D, 0xAE909198, 0xEAAD8E71, 0x6B93D5A0, 0xD08ED1D0, 0xAFC725E0, 0x8E3C5B2F, 0x8E7594B7, 0x8FF6E2FB, 0xF2122B64, 0x8888B812, 0x900DF01C, 0x4FAD5EA0, 0x688FC31C, 0xD1CFF191, 0xB3A8C1AD, 0x2F2F2218, 0xBE0E1777, 0xEA752DFE, 0x8B021FA1, 0xE5A0CC0F, 0xB56F74E8, 0x18ACF3D6, 0xCE89E299, 0xB4A84FE0, 0xFD13E0B7, 0x7CC43B81, 0xD2ADA8D9, 0x165FA266, 0x80957705, 0x93CC7314, 0x211A1477, 0xE6AD2065, 0x77B5FA86, 0xC75442F5, 0xFB9D35CF, 0xEBCDAF0C, 0x7B3E89A0, 0xD6411BD3, 0xAE1E7E49, 0x00250E2D, 0x2071B35E, 0x226800BB, 0x57B8E0AF, 0x2464369B, 0xF009B91E, 0x5563911D, 0x59DFA6AA, 0x78C14389, 0xD95A537F, 0x207D5BA2, 0x02E5B9C5, 0x83260376, 0x6295CFA9, 0x11C81968, 0x4E734A41, 0xB3472DCA, 0x7B14A94A, 0x1B510052, 0x9A532915, 0xD60F573F, 0xBC9BC6E4, 0x2B60A476, 0x81E67400, 0x08BA6FB5, 0x571BE91F, 0xF296EC6B, 0x2A0DD915, 0xB6636521, 0xE7B9F9B6, 0xFF34052E, 0xC5855664, 0x53B02D5D, 0xA99F8FA1, 0x08BA4799, 0x6E85076A ]; ORIG_S[1] = [ 0x4B7A70E9, 0xB5B32944, 0xDB75092E, 0xC4192623, 0xAD6EA6B0, 0x49A7DF7D, 0x9CEE60B8, 0x8FEDB266, 0xECAA8C71, 0x699A17FF, 0x5664526C, 0xC2B19EE1, 0x193602A5, 0x75094C29, 0xA0591340, 0xE4183A3E, 0x3F54989A, 0x5B429D65, 0x6B8FE4D6, 0x99F73FD6, 0xA1D29C07, 0xEFE830F5, 0x4D2D38E6, 0xF0255DC1, 0x4CDD2086, 0x8470EB26, 0x6382E9C6, 0x021ECC5E, 0x09686B3F, 0x3EBAEFC9, 0x3C971814, 0x6B6A70A1, 0x687F3584, 0x52A0E286, 0xB79C5305, 0xAA500737, 0x3E07841C, 0x7FDEAE5C, 0x8E7D44EC, 0x5716F2B8, 0xB03ADA37, 0xF0500C0D, 0xF01C1F04, 0x0200B3FF, 0xAE0CF51A, 0x3CB574B2, 0x25837A58, 0xDC0921BD, 0xD19113F9, 0x7CA92FF6, 0x94324773, 0x22F54701, 0x3AE5E581, 0x37C2DADC, 0xC8B57634, 0x9AF3DDA7, 0xA9446146, 0x0FD0030E, 0xECC8C73E, 0xA4751E41, 0xE238CD99, 0x3BEA0E2F, 0x3280BBA1, 0x183EB331, 0x4E548B38, 0x4F6DB908, 0x6F420D03, 0xF60A04BF, 0x2CB81290, 0x24977C79, 0x5679B072, 0xBCAF89AF, 0xDE9A771F, 0xD9930810, 0xB38BAE12, 0xDCCF3F2E, 0x5512721F, 0x2E6B7124, 0x501ADDE6, 0x9F84CD87, 0x7A584718, 0x7408DA17, 0xBC9F9ABC, 0xE94B7D8C, 0xEC7AEC3A, 0xDB851DFA, 0x63094366, 0xC464C3D2, 0xEF1C1847, 0x3215D908, 0xDD433B37, 0x24C2BA16, 0x12A14D43, 0x2A65C451, 0x50940002, 0x133AE4DD, 0x71DFF89E, 0x10314E55, 0x81AC77D6, 0x5F11199B, 0x043556F1, 0xD7A3C76B, 0x3C11183B, 0x5924A509, 0xF28FE6ED, 0x97F1FBFA, 0x9EBABF2C, 0x1E153C6E, 0x86E34570, 0xEAE96FB1, 0x860E5E0A, 0x5A3E2AB3, 0x771FE71C, 0x4E3D06FA, 0x2965DCB9, 0x99E71D0F, 0x803E89D6, 0x5266C825, 0x2E4CC978, 0x9C10B36A, 0xC6150EBA, 0x94E2EA78, 0xA5FC3C53, 0x1E0A2DF4, 0xF2F74EA7, 0x361D2B3D, 0x1939260F, 0x19C27960, 0x5223A708, 0xF71312B6, 0xEBADFE6E, 0xEAC31F66, 0xE3BC4595, 0xA67BC883, 0xB17F37D1, 0x018CFF28, 0xC332DDEF, 0xBE6C5AA5, 0x65582185, 0x68AB9802, 0xEECEA50F, 0xDB2F953B, 0x2AEF7DAD, 0x5B6E2F84, 0x1521B628, 0x29076170, 0xECDD4775, 0x619F1510, 0x13CCA830, 0xEB61BD96, 0x0334FE1E, 0xAA0363CF, 0xB5735C90, 0x4C70A239, 0xD59E9E0B, 0xCBAADE14, 0xEECC86BC, 0x60622CA7, 0x9CAB5CAB, 0xB2F3846E, 0x648B1EAF, 0x19BDF0CA, 0xA02369B9, 0x655ABB50, 0x40685A32, 0x3C2AB4B3, 0x319EE9D5, 0xC021B8F7, 0x9B540B19, 0x875FA099, 0x95F7997E, 0x623D7DA8, 0xF837889A, 0x97E32D77, 0x11ED935F, 0x16681281, 0x0E358829, 0xC7E61FD6, 0x96DEDFA1, 0x7858BA99, 0x57F584A5, 0x1B227263, 0x9B83C3FF, 0x1AC24696, 0xCDB30AEB, 0x532E3054, 0x8FD948E4, 0x6DBC3128, 0x58EBF2EF, 0x34C6FFEA, 0xFE28ED61, 0xEE7C3C73, 0x5D4A14D9, 0xE864B7E3, 0x42105D14, 0x203E13E0, 0x45EEE2B6, 0xA3AAABEA, 0xDB6C4F15, 0xFACB4FD0, 0xC742F442, 0xEF6ABBB5, 0x654F3B1D, 0x41CD2105, 0xD81E799E, 0x86854DC7, 0xE44B476A, 0x3D816250, 0xCF62A1F2, 0x5B8D2646, 0xFC8883A0, 0xC1C7B6A3, 0x7F1524C3, 0x69CB7492, 0x47848A0B, 0x5692B285, 0x095BBF00, 0xAD19489D, 0x1462B174, 0x23820E00, 0x58428D2A, 0x0C55F5EA, 0x1DADF43E, 0x233F7061, 0x3372F092, 0x8D937E41, 0xD65FECF1, 0x6C223BDB, 0x7CDE3759, 0xCBEE7460, 0x4085F2A7, 0xCE77326E, 0xA6078084, 0x19F8509E, 0xE8EFD855, 0x61D99735, 0xA969A7AA, 0xC50C06C2, 0x5A04ABFC, 0x800BCADC, 0x9E447A2E, 0xC3453484, 0xFDD56705, 0x0E1E9EC9, 0xDB73DBD3, 0x105588CD, 0x675FDA79, 0xE3674340, 0xC5C43465, 0x713E38D8, 0x3D28F89E, 0xF16DFF20, 0x153E21E7, 0x8FB03D4A, 0xE6E39F2B, 0xDB83ADF7 ]; ORIG_S[2] = [ 0xE93D5A68, 0x948140F7, 0xF64C261C, 0x94692934, 0x411520F7, 0x7602D4F7, 0xBCF46B2E, 0xD4A20068, 0xD4082471, 0x3320F46A, 0x43B7D4B7, 0x500061AF, 0x1E39F62E, 0x97244546, 0x14214F74, 0xBF8B8840, 0x4D95FC1D, 0x96B591AF, 0x70F4DDD3, 0x66A02F45, 0xBFBC09EC, 0x03BD9785, 0x7FAC6DD0, 0x31CB8504, 0x96EB27B3, 0x55FD3941, 0xDA2547E6, 0xABCA0A9A, 0x28507825, 0x530429F4, 0x0A2C86DA, 0xE9B66DFB, 0x68DC1462, 0xD7486900, 0x680EC0A4, 0x27A18DEE, 0x4F3FFEA2, 0xE887AD8C, 0xB58CE006, 0x7AF4D6B6, 0xAACE1E7C, 0xD3375FEC, 0xCE78A399, 0x406B2A42, 0x20FE9E35, 0xD9F385B9, 0xEE39D7AB, 0x3B124E8B, 0x1DC9FAF7, 0x4B6D1856, 0x26A36631, 0xEAE397B2, 0x3A6EFA74, 0xDD5B4332, 0x6841E7F7, 0xCA7820FB, 0xFB0AF54E, 0xD8FEB397, 0x454056AC, 0xBA489527, 0x55533A3A, 0x20838D87, 0xFE6BA9B7, 0xD096954B, 0x55A867BC, 0xA1159A58, 0xCCA92963, 0x99E1DB33, 0xA62A4A56, 0x3F3125F9, 0x5EF47E1C, 0x9029317C, 0xFDF8E802, 0x04272F70, 0x80BB155C, 0x05282CE3, 0x95C11548, 0xE4C66D22, 0x48C1133F, 0xC70F86DC, 0x07F9C9EE, 0x41041F0F, 0x404779A4, 0x5D886E17, 0x325F51EB, 0xD59BC0D1, 0xF2BCC18F, 0x41113564, 0x257B7834, 0x602A9C60, 0xDFF8E8A3, 0x1F636C1B, 0x0E12B4C2, 0x02E1329E, 0xAF664FD1, 0xCAD18115, 0x6B2395E0, 0x333E92E1, 0x3B240B62, 0xEEBEB922, 0x85B2A20E, 0xE6BA0D99, 0xDE720C8C, 0x2DA2F728, 0xD0127845, 0x95B794FD, 0x647D0862, 0xE7CCF5F0, 0x5449A36F, 0x877D48FA, 0xC39DFD27, 0xF33E8D1E, 0x0A476341, 0x992EFF74, 0x3A6F6EAB, 0xF4F8FD37, 0xA812DC60, 0xA1EBDDF8, 0x991BE14C, 0xDB6E6B0D, 0xC67B5510, 0x6D672C37, 0x2765D43B, 0xDCD0E804, 0xF1290DC7, 0xCC00FFA3, 0xB5390F92, 0x690FED0B, 0x667B9FFB, 0xCEDB7D9C, 0xA091CF0B, 0xD9155EA3, 0xBB132F88, 0x515BAD24, 0x7B9479BF, 0x763BD6EB, 0x37392EB3, 0xCC115979, 0x8026E297, 0xF42E312D, 0x6842ADA7, 0xC66A2B3B, 0x12754CCC, 0x782EF11C, 0x6A124237, 0xB79251E7, 0x06A1BBE6, 0x4BFB6350, 0x1A6B1018, 0x11CAEDFA, 0x3D25BDD8, 0xE2E1C3C9, 0x44421659, 0x0A121386, 0xD90CEC6E, 0xD5ABEA2A, 0x64AF674E, 0xDA86A85F, 0xBEBFE988, 0x64E4C3FE, 0x9DBC8057, 0xF0F7C086, 0x60787BF8, 0x6003604D, 0xD1FD8346, 0xF6381FB0, 0x7745AE04, 0xD736FCCC, 0x83426B33, 0xF01EAB71, 0xB0804187, 0x3C005E5F, 0x77A057BE, 0xBDE8AE24, 0x55464299, 0xBF582E61, 0x4E58F48F, 0xF2DDFDA2, 0xF474EF38, 0x8789BDC2, 0x5366F9C3, 0xC8B38E74, 0xB475F255, 0x46FCD9B9, 0x7AEB2661, 0x8B1DDF84, 0x846A0E79, 0x915F95E2, 0x466E598E, 0x20B45770, 0x8CD55591, 0xC902DE4C, 0xB90BACE1, 0xBB8205D0, 0x11A86248, 0x7574A99E, 0xB77F19B6, 0xE0A9DC09, 0x662D09A1, 0xC4324633, 0xE85A1F02, 0x09F0BE8C, 0x4A99A025, 0x1D6EFE10, 0x1AB93D1D, 0x0BA5A4DF, 0xA186F20F, 0x2868F169, 0xDCB7DA83, 0x573906FE, 0xA1E2CE9B, 0x4FCD7F52, 0x50115E01, 0xA70683FA, 0xA002B5C4, 0x0DE6D027, 0x9AF88C27, 0x773F8641, 0xC3604C06, 0x61A806B5, 0xF0177A28, 0xC0F586E0, 0x006058AA, 0x30DC7D62, 0x11E69ED7, 0x2338EA63, 0x53C2DD94, 0xC2C21634, 0xBBCBEE56, 0x90BCB6DE, 0xEBFC7DA1, 0xCE591D76, 0x6F05E409, 0x4B7C0188, 0x39720A3D, 0x7C927C24, 0x86E3725F, 0x724D9DB9, 0x1AC15BB4, 0xD39EB8FC, 0xED545578, 0x08FCA5B5, 0xD83D7CD3, 0x4DAD0FC4, 0x1E50EF5E, 0xB161E6F8, 0xA28514D9, 0x6C51133C, 0x6FD5C7E7, 0x56E14EC4, 0x362ABFCE, 0xDDC6C837, 0xD79A3234, 0x92638212, 0x670EFA8E, 0x406000E0 ]; ORIG_S[3] = [ 0x3A39CE37, 0xD3FAF5CF, 0xABC27737, 0x5AC52D1B, 0x5CB0679E, 0x4FA33742, 0xD3822740, 0x99BC9BBE, 0xD5118E9D, 0xBF0F7315, 0xD62D1C7E, 0xC700C47B, 0xB78C1B6B, 0x21A19045, 0xB26EB1BE, 0x6A366EB4, 0x5748AB2F, 0xBC946E79, 0xC6A376D2, 0x6549C2C8, 0x530FF8EE, 0x468DDE7D, 0xD5730A1D, 0x4CD04DC6, 0x2939BBDB, 0xA9BA4650, 0xAC9526E8, 0xBE5EE304, 0xA1FAD5F0, 0x6A2D519A, 0x63EF8CE2, 0x9A86EE22, 0xC089C2B8, 0x43242EF6, 0xA51E03AA, 0x9CF2D0A4, 0x83C061BA, 0x9BE96A4D, 0x8FE51550, 0xBA645BD6, 0x2826A2F9, 0xA73A3AE1, 0x4BA99586, 0xEF5562E9, 0xC72FEFD3, 0xF752F7DA, 0x3F046F69, 0x77FA0A59, 0x80E4A915, 0x87B08601, 0x9B09E6AD, 0x3B3EE593, 0xE990FD5A, 0x9E34D797, 0x2CF0B7D9, 0x022B8B51, 0x96D5AC3A, 0x017DA67D, 0xD1CF3ED6, 0x7C7D2D28, 0x1F9F25CF, 0xADF2B89B, 0x5AD6B472, 0x5A88F54C, 0xE029AC71, 0xE019A5E6, 0x47B0ACFD, 0xED93FA9B, 0xE8D3C48D, 0x283B57CC, 0xF8D56629, 0x79132E28, 0x785F0191, 0xED756055, 0xF7960E44, 0xE3D35E8C, 0x15056DD4, 0x88F46DBA, 0x03A16125, 0x0564F0BD, 0xC3EB9E15, 0x3C9057A2, 0x97271AEC, 0xA93A072A, 0x1B3F6D9B, 0x1E6321F5, 0xF59C66FB, 0x26DCF319, 0x7533D928, 0xB155FDF5, 0x03563482, 0x8ABA3CBB, 0x28517711, 0xC20AD9F8, 0xABCC5167, 0xCCAD925F, 0x4DE81751, 0x3830DC8E, 0x379D5862, 0x9320F991, 0xEA7A90C2, 0xFB3E7BCE, 0x5121CE64, 0x774FBE32, 0xA8B6E37E, 0xC3293D46, 0x48DE5369, 0x6413E680, 0xA2AE0810, 0xDD6DB224, 0x69852DFD, 0x09072166, 0xB39A460A, 0x6445C0DD, 0x586CDECF, 0x1C20C8AE, 0x5BBEF7DD, 0x1B588D40, 0xCCD2017F, 0x6BB4E3BB, 0xDDA26A7E, 0x3A59FF45, 0x3E350A44, 0xBCB4CDD5, 0x72EACEA8, 0xFA6484BB, 0x8D6612AE, 0xBF3C6F47, 0xD29BE463, 0x542F5D9E, 0xAEC2771B, 0xF64E6370, 0x740E0D8D, 0xE75B1357, 0xF8721671, 0xAF537D5D, 0x4040CB08, 0x4EB4E2CC, 0x34D2466A, 0x0115AF84, 0xE1B00428, 0x95983A1D, 0x06B89FB4, 0xCE6EA048, 0x6F3F3B82, 0x3520AB82, 0x011A1D4B, 0x277227F8, 0x611560B1, 0xE7933FDC, 0xBB3A792B, 0x344525BD, 0xA08839E1, 0x51CE794B, 0x2F32C9B7, 0xA01FBAC9, 0xE01CC87E, 0xBCC7D1F6, 0xCF0111C3, 0xA1E8AAC7, 0x1A908749, 0xD44FBD9A, 0xD0DADECB, 0xD50ADA38, 0x0339C32A, 0xC6913667, 0x8DF9317C, 0xE0B12B4F, 0xF79E59B7, 0x43F5BB3A, 0xF2D519FF, 0x27D9459C, 0xBF97222C, 0x15E6FC2A, 0x0F91FC71, 0x9B941525, 0xFAE59361, 0xCEB69CEB, 0xC2A86459, 0x12BAA8D1, 0xB6C1075E, 0xE3056A0C, 0x10D25065, 0xCB03A442, 0xE0EC6E0E, 0x1698DB3B, 0x4C98A0BE, 0x3278E964, 0x9F1F9532, 0xE0D392DF, 0xD3A0342B, 0x8971F21E, 0x1B0A7441, 0x4BA3348C, 0xC5BE7120, 0xC37632D8, 0xDF359F8D, 0x9B992F2E, 0xE60B6F47, 0x0FE3F11D, 0xE54CDA54, 0x1EDAD891, 0xCE6279CF, 0xCD3E7E6F, 0x1618B166, 0xFD2C1D05, 0x848FD2C5, 0xF6FB2299, 0xF523F357, 0xA6327623, 0x93A83531, 0x56CCCD02, 0xACF08162, 0x5A75EBB5, 0x6E163697, 0x88D273CC, 0xDE966292, 0x81B949D0, 0x4C50901B, 0x71C65614, 0xE6C6C7BD, 0x327A140A, 0x45E1D006, 0xC3F27B9A, 0xC9AA53FD, 0x62A80F00, 0xBB25BFE2, 0x35BDD2F6, 0x71126905, 0xB2040222, 0xB6CBCF7C, 0xCD769C2B, 0x53113EC0, 0x1640E3D3, 0x38ABBD60, 0x2547ADF0, 0xBA38209C, 0xF746CE76, 0x77AFA1C5, 0x20756060, 0x85CBFE4E, 0x8AE88DD8, 0x7AAAF9B0, 0x4CF9AA7E, 0x1948C25C, 0x02FB8A8C, 0x01C36AE4, 0xD6EBE1F9, 0x90D4F869, 0xA65CDEA0, 0x3F09252D, 0xC208E69F, 0xB74E6132, 0xCE77E25B, 0x578FDFE3, 0x3AC372E6 ]; function BlowfishCtx () { this.P = []; this.S = []; for (var i=0; i<4; i++) { this.S[i] = []; } return this; }; function uns32Add(a, b) { var sum = (a + b) & 0xFFFFFFFF; var retval; if (sum < 0) { sum = -sum; var lw = ((sum & 0xFFFF) ^ 0xFFFF) + 1; var uw = ((sum >> 16) ^ 0xFFFF); retval = 65536 * uw + lw; } else { retval = sum; } return retval; } function split32(a) { var r = a & 0xFFFFFFFF; var retval = []; if (r < 0) { r = -r; retval[0] = ((r & 0xFFFF) ^ 0xFFFF) + 1; retval[1] = ((r >> 16) ^ 0xFFFF); } else { retval[0] = r & 0xFFFF; retval[1] = r >> 16; } return retval; } function uns32Xor(x, y) { xs = split32(x); ys = split32(y); return 65536 * (xs[1] ^ ys[1]) + (xs[0] ^ ys[0]); } function F(ctx, x) { var a, b, c, d; var y; d = x & 0xFF; x >>= 8; c = x & 0xFF; x >>= 8; b = x & 0xFF; x >>= 8; a = x & 0xFF; y = uns32Add(ctx.S[0][a], ctx.S[1][b]); y = uns32Xor(y, ctx.S[2][c]); y = uns32Add(y, ctx.S[3][d]); return y; } function blowfish_encrypt(ctx, Xl, Xr) { var temp; for (var i = 0; i < N; ++i) {   Xl = uns32Xor(Xl,ctx.P[i]);   Xr = uns32Xor(F(ctx, Xl), Xr);   temp = Xl;   Xl = Xr;   Xr = temp; } temp = Xl; Xl = Xr; Xr = temp; Xr = uns32Xor(Xr, ctx.P[N]); Xl = uns32Xor(Xl, ctx.P[N + 1]);   return [Xl, Xr]; } function blowfish_decrypt(ctx, Xl, Xr){   var temp;   for (i = N + 1; i > 1; --i) { Xl = uns32Xor(Xl, ctx.P[i]); Xr = uns32Xor(F(ctx, Xl), Xr); temp = Xl; Xl = Xr; Xr = temp;   }   temp = Xl;   Xl = Xr;   Xr = temp;   Xr = uns32Xor(Xr, ctx.P[1]);   Xl = uns32Xor(Xl, ctx.P[0]);   return [Xl, Xr]; } function blowfish_init(ctx, key) { var data, datal, datar; var i, j, k; for (i = 0; i < 4; i++) {   for (j = 0; j < 256; j++) ctx.S[i][j] = ORIG_S[i][j]; } j = 0; for (i = 0; i < N + 2; ++i) {   data = 0x00000000;   for (k = 0; k < 4; ++k) { data = ((data << 8) & 0xFFFFFFFF) | key.charCodeAt(j); j = j + 1; if (j >= key.length) { j = 0; }   }   ctx.P[i] = ORIG_P[i] ^ data; } datal = 0x00000000; datar = 0x00000000; var res = []; for (i = 0; i < N + 2; i += 2) {   res = blowfish_encrypt(ctx, datal, datar);   datal = res[0];   datar = res[1];   ctx.P[i] = datal;   ctx.P[i + 1] = datar; } for (i = 0; i < 4; ++i) {   for (j = 0; j < 256; j += 2) {   res = blowfish_encrypt(ctx, datal, datar);   datal = res[0];   datar = res[1];   ctx.S[i][j] = datal;   ctx.S[i][j + 1] = datar;   } } } function decrypt(context, s) { var L = 0, R = 0; L = parseInt(s.substring(0, 8), 16); R = parseInt(s.substring(8, 16), 16); r = blowfish_decrypt(context, L, R); var s = ""; if (r[0] & 0xFFFF) { s += String.fromCharCode(r[0] & 0xFFFF); } if (r[0] >> 16) { s += String.fromCharCode(r[0] >> 16); } if (r[1] & 0xFFFF) { s += String.fromCharCode(r[1] & 0xFFFF); } if (r[1] >> 16) { s += String.fromCharCode(r[1] >> 16); } return s; } function decrypt_string(context, s) { output = ""; while (s.length) { output += decrypt(context, s); s = s.substring(16, s.length); } return output; } var enc_divs = document.evaluate("//div[contains('encrypted blowfish', " + "@class)]//div[contains('encdata', @class)]", document, null, XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE, null); for (var i = 0; i < enc_divs.snapshotLength; i++) { var tdiv = enc_divs.snapshotItem(i); var div_content = tdiv.innerHTML.split(":"); if (div_content.length < 2) { continue; } if (!(div_content[0] in keys)) { continue; } var context = new BlowfishCtx(); blowfish_init(context, keys[div_content[0]]); tdiv.parentNode.innerHTML = decrypt_string( context, div_content.slice(1).join(':')); } 

10.6.2. Running the Hack

Before you install the user script, log into Bloglines (http://www.bloglines.com), click Add to add a subscription, and subscribe to the Secure Syndication test feed (http://bitworking.org/projects/securesyndication/index.rss). When you view the entry in Bloglines, all you will see is encrypted data, as shown in Figure 10-11.

Figure 10-11. Encrypted feed

Now, install the script (Tools Install This User Script) and refresh the Bloglines page. Select the encrypted feed subscription, and then select All Items from the drop-down menu to force Bloglines to redisplay the encrypted entry. You will briefly see the encrypted data, and then the script will decrypt the data and replace it with the decrypted message, as shown in Figure 10-12.

Figure 10-12. Decrypted feed

Currently, the encryption key is stored in the script, thus forcing you to hand-edit the script for every new key you use. It would be easy enough to store the keys with GM_setValue and retrieve them with GM_getValue. This would allow you to enter new keys manually by going to about:config and adding a new value. Or you could construct a graphical interface for adding a new key.

To store passwords in the Firefox preferences database, change the for loop:

 for (var i = 0; i < enc_divs.snapshotLength; i++) { var tdiv = enc_divs.snapshotItem(i); var div_content = tdiv.innerHTML.split(":"); if (div_content.length != 2) { continue; } var pass = GM_getValue('key.' + div_content[0]); if (!pass) { continue; } var context = new BlowfishCtx(); blowfish_init(context, pass); tdiv.parentNode.innerHTML = decrypt_string(context, div_content[1]); } 

If the script encounters an encrypted area for which it doesn't have the key, it will simply leave the encrypted data as-is. But we could extend this further, to insert a form above the encrypted data that prompts the user for the password and then saves it with GM_setValue:

 var enc_divs = document.evaluate("//div[contains('encrypted blowfish', " + "@class)]//div[contains('encdata', @class)]", document, null, XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE, null); for (var i = 0; i < enc_divs.snapshotLength; i++) { var tdiv = enc_divs.snapshotItem(i); var div_content = tdiv.innerHTML.split(":"); if (div_content.length < 2) { continue; } var pass = GM_getValue('key.' + div_content[0]); if (!pass) { var elmForm = document.createElement('form'); elmForm.id = div_content[0]; elmForm.innerHTML = 'Password: <input type="password">'; elmForm.addEventListener('submit', function(e) { var elmPassword = e.target.getElementsByTagName('input')[0]; var pass = elmPassword.value; GM_setValue('key.' + e.target.id, pass); e.preventDefault(); var context = new BlowfishCtx(); blowfish_init(context, pass); var tdiv = e.target.nextSibling; tdiv.parentNode.innerHTML = decrypt_string(context, tdiv.innerHTML.split(':').slice(1).join(':')); }, true); tdiv.parentNode.insertBefore(elmForm, tdiv); continue; } var context = new BlowfishCtx(); blowfish_init(context, pass); tdiv.parentNode.innerHTML = decrypt_string( context, div_content.slice(1).join(':')); } 

Now, instead of simply showing the encrypted data, the script displays a small form in which you can enter the password to decrypt the data, as shown in Figure 10-13.

Figure 10-13. Entering a password to decrypt the feed

The script traps the onsubmit event and stores the password you entered, and then proceeds to decrypt the data and display it.

Joe Gregorio