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Password protect a static HTML page

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Re: Password protect a static HTML page

#141

Post by doodlesdev »

snowstormsun wrote: post #128
DanielBMarkham wrote: post #114

Gad! I have spent all morning trying to --- password protect a static html page. How in the hell does HN have a story about the exact topic I've been struggling with appear just a dozen or so hours after I started working on it. Wow. I was _extremely_ happy to see this posted. However when I click the link I am taken to the library I had initially tried and had to reject. Without getting into the crypto side of thing…

Something similar has been posted before some time ago: https://news.ycombinator.com/item?id=34083366

Which in turn has inspired the creation of PrivacyProtect [0]. It allows to do basically the same thing as the other applications, but in my opinion the interface is better, it also allows you to directly select a file which I guess is easier than copying the contents, it also means you can just select an image file for instance or some other type of file other than a web page.

[0]: https://www.privacyprotect.dev/

Re: Password protect a static HTML page

#142

Post by layer8 »

Karellen wrote: post #132
layer8 wrote: post #117

Earlier quoted context omitted.

Supposedly browsers are more ubiquitous on the recipient side than whatever other tools you might use.

I was thinking of editing my comment to add "Or be able to support filetypes other than HTML", but I suppose in our glorious "everything is the browser" future, filetypes other than HTML are as anachronistic as 8" floppy disks. Sigh.

FWIW, you can use data URLs to include any type of file in your HTML, and with browsers will allow you to save the file.

Re: Password protect a static HTML page

#143

Post by ThePhysicist »

tialaramex wrote: post #96
tptacek wrote: post #74

Earlier quoted context omitted.

I don't know what "being a stream" has to do with anything (you should virtually always use "stream" modes of AES); the meaningful distinction between CBC and GCM is that GCM authenticates the ciphertext, so you can't tamper with it.

> so you can't tamper with it. ... if the API provided is correctly designed, and either the language made it practical to design the API in a misuse-resistant way /or/ the programmer was actually careful and used it properly. We both know it's way more likely the problem in your actual system is "Oops, we use the bogus plaintext here despite the validation error" than "Dastardly enemy cryptographers have made a brea…

SubtleCrypto (Web Cryptography API) will simply throw an exception if the authentication fails for AES-GCM, so there's no way to even get at the bogus plaintext.

Re: Password protect a static HTML page

#144

Post by d-z-m »

fifafu wrote: post #115
tptacek wrote: post #87

Earlier quoted context omitted.

So use WebCrypto, instead of the cabinet of curiosities that is crypto-js. (Or, better yet, don't do stuff like this at all, because a browser window is simply an awful setting for serious cryptography).

WebCrypto only works in secure contexts which is a significant limitation (https origins only)

If you're talking about sending these files around via email/messenger, most browsers treat localhost as a secure context, so this doesn't seem like that significant of a limitation.

If you are serving out an encrypted HTML page insecurely, your users are already hosed, because someone on the path could inject a script that sends the password to evil[.]com when they type it in.

Re: Password protect a static HTML page

#145

Post by ThePhysicist »

dragontamer wrote: post #72
Xeoncross wrote: post #47

I'm not a cryptographer, but I'm pretty sure that CBC ( https://github.com/robinmoisson/staticrypt/blob/main/lib/cry... ) should be replaced with GCM ( https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypt... ) since this is not a stream. https://security.stackexchange.com/questions/184305/why-woul... (also, use the built-in WebCrypto API instead of the crypto-js package)

CBC is far easier to implement than GCM mode. I bet that most programmers cannot implement a Galois Field in Javascript. Meanwhile, CBC is just "encrypt then xor".

AES-GCM is part of the Web Cryptography API and supported in all modern browsers, so no need to implement anything.

Re: Password protect a static HTML page

#148

Post by tptacek »

majou wrote: post #139
tptacek wrote: post #133

Earlier quoted context omitted.

As I remember it, the balance of the bytes in the AES block are used for the counter. At any rate, the convention is essentially universal.

Sounds above my (current) head. Here I thought GCM was some modern foolproof/footgunless design.

It is sort of infamously footgunny.

Re: Password protect a static HTML page

#149

Post by ThePhysicist »

tptacek wrote: post #84
trusz wrote: post #55

Earlier quoted context omitted.

Not going to pretend that I know what the most of the stuff mean, or if it is even safe enough, but I've followed the MDN articles and put together this TypeScript snippet [1]. Maybe somebody could comment on it? Also sorry for the long link. Is there any accepted way to post a shorted URL? Edit: added a corrected version [2] [1]: https://www.typescriptlang.org/play?#code/DYUwLgBAbiDGYHsBOE... [2]: https://www.typesc…

If you call "encrypt" more than once in that code, you'll leak the authentication key. Every invocation of GCM encryption needs a unique nonce. Cryptography nerds will chastise you for using a random nonce (there theoretically isn't enough room in the GCM nonce space to safely encrypt large numbers of message with random nonces), but the alternative (using a counter) is even more hazardous. This problem motivates a l…

It's still considered safe to call AES-GCM with a single key and a randomly generated nonce 2^32 times [1], most practical systems don't come anywhere near this limit. And there's AES-GCM-SIV that solves nonce reuse (mostly), though it's not available in the Web Cryptography API at the moment.

1: https://csrc.nist.gov/csrc/media/Projects/crypto-publication...

Re: Password protect a static HTML page

#150

Post by DanielBMarkham »

doodlesdev wrote: post #141
snowstormsun wrote: post #128

Earlier quoted context omitted.

Something similar has been posted before some time ago: https://news.ycombinator.com/item?id=34083366

Which in turn has inspired the creation of PrivacyProtect [0]. It allows to do basically the same thing as the other applications, but in my opinion the interface is better, it also allows you to directly select a file which I guess is easier than copying the contents, it also means you can just select an image file for instance or some other type of file other than a web page. [0]: https://www.privacyprotect.dev/

Why is everybody forcing me to upload to the web the very files I want to keep private to myself? If any code in the universe should run locally, it's this kind of code.

I don't get it.

Great UI, though. But I still don't get it.

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