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Message-ID: <50C5A19A.7070205@banquise.net>
Date: Mon, 10 Dec 2012 09:47:22 +0100
From: Simon Marechal <simon@...quise.net>
To: john-dev@...ts.openwall.com
Subject: Re: fixing the valid() methods
On 10/12/2012 02:57, Solar Designer wrote:
> Can we afford a dependency on regcomp(3), regexec(3), regfree(3) in
> jumbo? Apparently, these are in POSIX.1-2001. Yet I am unlikely to
> introduce this change to core, so it'd be yet another jumbo thing.
>
> Personally, I don't feel much need to go for regexps - I find it easy
> enough to write robust valid() based on str(r)chr() and such - but I
> understand that others' preferences may be different.
Perhaps some kind of sscanf-like function, that accepts a specific
format ? Something that might look like:
validate("$X$%b8$%h128", ciphertext)
That would return true if ciphertext is made of (exactly) "$X$" followed
by 8 chars forming a valid base 64 value, followed by 128 chars forming
a valid hex-encoded value.
It might even work as sscanf for use in binary, and would be used like
this in valid:
validate(ciphertext, "$X$%b8$%h128", NULL, NULL)
in binary :
validate(ciphertext, "$X$%b8$%h128", NULL, &bin)
in salt :
validate(ciphertext, "$X$%b8$%h128", &salt, NULL)
This doesn't seem to be too much work, and has the following advantages:
* centralized and hopefuly bug-free code for converting ascii to binary
in various ways (hex, base64, endianness, ...)
* reuse the same format and functions in validate, binary and salt
* makes the expected ciphertext format obvious
Another approach would be having a set of functions working with a
parsing context. This might be easier to add features this way, but
seems less easy to use :
ctx = start_parse(ciphertext);
if(!parse_string(ctx, "$X$"))
return 0;
if(!parse_base64(ctx, 8))
return 0;
if(!parse_string(ctx,"$"))
return 0;
if(!parse_hex(ctx, 128))
return 0;
if(!parse_eol(ctx))
return 0;
What do you guys think ?
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