Re: [gentoo-hardened] ssp random bytes solution

[Robert Connolly]

On April 20, 2004 12:13 pm, Ned Ludd wrote:
> Robert,
>
> I must apologize the previous example code was printing the address
> of __guard and not value of the __guard itself.
>
> Can we try something like?
> -------------------------
> extern unsigned long __guard[];
>
> int main () {
>         printf("__guard\t=\t0x%08x;\n", __guard[0]);
> 	return 0;
> }
> -----------------------

This output changes for each runtime using sysctl erandom.

> I've also been giving some more thought into using the gettimeofday() as
> we had discussed one day.. It could work across the board and would and
> no kernel patching would be required which is probably more ideal for
> Gentoo users as we have a butt ton of kernels. Disadvantage of course
> would be potential timing attacks by local users.

Using gettimeofday as a seed is less secure than we have now. I went to the 
trouble of getting sysctl-erandom working because it is equaly secure as 
urandom. I also have plans to patch mkstemp to use sysctl-erandom, and 
anywhere else that isn't crypto. Sysctl-erandom will not be only for SSP. 
Gettimeofday could be added to the canary fallback however. Infact I have an 
arcfour lib to hash gettimeofday that could be added to the ssp.c file, but 
it is a lot of bloat for a fallback feature, and again erandom does a better 
job.



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